IElectronic compiled by
Machine Tool Engineering Foundation in November, 2022
IIISBN 978-4-909859-02-0© Machine Tool Engineering Foundation 2022
Photograph in front cover:by courtesy of Nakamura-tome Precision Industry

IIIPreface
In discussing the utilization technology for machine tools, primary concern
is the “Machining Space”, i.e., machine-attachment-tool-work system, andas well known, the utilization technology relies on the skill and qualificationof the user to a large extent even in the era of NC (Numerical Control,
Numerically Controlled) technology. As represented by the “Chatter
Vibration”, we cannot run the machine tool efficiently and effectively
without having the mature process planner (process plan engineer) andtechnician, even when we can purchase it with the best performance.
To be the preferable utilization technology in satisfactory quality, a root
cause of difficulties lies furthermore in the establishment of the machining
space with better leverage, i.e., better combination of all the systemcomponents, which are also individually in the best functional andperformance specifications. Of note, such a desirable machining space mayachieve especially from the viewpoint of hardware in the case of “Chatter
Vibration”.
Within process planning context, the facing problems are much more
complex than those in “Chatter Vibration”, because we must discuss how toestablish a desirable machining space from both the hardware and thesoftware aspects together with considering the leverage between them. Morespecifically, process planning is a synergy of hardware, e.g., theory andpractice in metal cutting, and software, i.e., information processing startingfrom the part drawing and terminating the generation of the process plan.
As a result, it has been common sense that process planning is very
experienced-oriented technology, and that the only mature process planner
can produce the acceptable process plan with higher quality.
Importantly, with the advent of FMS (Flexible Manufacturing System) andCIM (Computer-Integrated Manufacturing), CAPP (Computer-Aided
Process Planning), i.e., computerization of process planning, became one of
the necessary and inevitable software to produce automatically the processplan together with playing the intermediating role between CAD (ComputerIVAided Design) and CAM (Computer-Aided Manufacturing). In consequence,
there have been a myriad of academic research activities on and engineeringdevelopments of CAPP since 1980s; however, nearly all CAPPs so far
publicized are far from completion. In fact, we can eye something definite
indicating the fatal shortage of the academic research into CAPP, which is
caused by not modeling authentically process planning in practice. In otherwords, nearly all CAPPs either have been or being developed by not delving
into what are the essential features of process planning in practice such as
follows.
(1) Along with considering a synergy of hardware and software
technologies, process planning can be characterized by its humanintelligence-based nature. The process planner must deal with themediation among various determinants, which are in conflict
relationships among one another, to obtain the preferable process plan.
Obviously, we need higher skill to automatize such a decision-making
procedure by the computer-aided method.
(2) The utmost primary concerns in process planning are to choose firstwhat is the preparatory work of raw material, e.g., either forging or cold
drawing, and then to determine its shape and dimensions in
consideration of the material efficiency. Importantly, the engineering
designer pays special attention to the form-generating procedure of thepart being drawn by assuming what is a preferable raw material together
with conducting rough pre-process planning.
Furthermore, we face often certain difficulties in applying the commercial
software for CAPP to practice even now, because such a software involves
the conversion problem of the geometrical into corresponding machining
features.
Against to this context, we must, in general, recognize that CAPP at present
appears as to be in mature states, although involving certain shortages asmentioned above; however, it emphasizes now that the machine tool,
attachment and tool have launched out to a new horizon in the year 2010 andVbeyond. Thus, CAPP at present appears as to be obsolete, i.e., “CAPP atpresent becoming immature from mature states”.
More specifically, at issues in machine tool and attachment are now thehighly machining function-integrated kind like “Mill-turn” and“Combination Chuck”, respectively. This means, there are no necessities tochoose the kind of the machine tool in process planning, although it is oneof conventional functions within CAPP at present. In addition, we can see a
handful of innovative and novel cutting and grinding tools, which may
accelerate the amazing phase changes in process planning.
As can be readily seen from the above, we face a turning point now, and must
duly conduct the two-pronged activities to enhance CAPP at present: one is
to improve its applicability to the practice, and the other is to contrive a newconcept and due methodologies for CAPP, which is available for a future
factory system, i.e., flexible-, intelligent- and smart-factory system.
Obviously, the utmost crucial issue in both the ways is to establish a “Oneto-One” conversion method between the geometrical information describedon the part drawing and the manufacturing-related information. In fact, there
are various turning methods to generate the cylindrical part ranging fromturning with a single-point cutting tool, through rotating cutter method, toturn-milling. In retrospect, nearly all CAPP at present involve such a serious
problem related to “One-to-One” conversion apart from those employed “IFTHEN” rule in the expert type; however, we must remember that “IF-THEN”
rule is far from fruition. Intuitively, to solve the “One-to-One” conversion
problem, one of powerful remedies appears to incorporate the decisionmaking procedure of the mature process planner after visualizing it bycertain methods.
In consideration of both the essential features in CAPP and the new horizon
upheaving CAPP at present, this book describes first the basic knowledge
about CAPP, and reviews its present perspectives. In due course, the book
discusses then the innovative driving factors in the machining space, which
will induce the marked phase changes in CAPP at present and in very near
future. Finally, the book proposes a new concept for CAPP available for theVIfuture machining space, which is based on the thinking ways and thoughtpatterns of the mature process planner.
Summarizing, the book discusses what are R & D (Research and Engineering
Development) subjects for CAPP, which is expectable in very near future
together with considering the rapidly changing states within the machining
space. Thus, the book is very suitable for young researchers and engineers
who are interested in and attracted to CAPP of advanced type. Importantly,
the author will suggest obviously the due “R & D” subjects by using the“Bold-Italic” within the main body, whenever necessary. Furthermore, toavoid unnecessary confusion and complexity, the book discusses mainly
CAPP for “Axis-symmetrical rotational parts”, which can be finished by TC(Turning Centre). In this context, we must mind that TC is one of advanced
types of NC turning machine, and “Mill-turn” is a synergy of TC and MC(Machining Centre).
November 2022

Yoshimi ITO, Tokyo Institute of Technology
Professor Emeritus Dr.

VIIAbbreviations
ACC: Automatic Chuck Changer
AJC: Automatic Jaw Changer
CAD: Computer-Aided Design
CAM: Computer-Aided Manufacturing
CAOP: Computer-Aided Operational Planning
CAPP: Computer-Aided Process Planning
CIM: Computer-Integrated Manufacturing
GT: Group Technology
FCIPS: Flexible Computer-Integrated Production Structure
FMC: Flexible Manufacturing Cell
FMS: Flexible Manufacturing System
MC: Machining Center
NC: Numerical Control, or Numerically Controlled
QFD: Quality Function Deployment
TC: Turning Center

VIII

Contents
Preface
Chapter 1 Introduction .................................................................................. 1
References...................................................................................................... 5
Chapter 2 Basic Knowledge about, Present Perspectives and Facing Issuesof CAPP ...................................................................................... 6
2.1 What Are Primary Concerns in Process Planning ................................... 6
2.2 Perspectives of and Leading Types in CAPP at Present ........................ 12
2.3 Leading Issues Inhabiting within CAPP in Details ............................... 21
2.4 Another Crucial Issue by Nature – Essential Causality Departing
Academic Research from Practical Application .................................... 23
References.................................................................................................... 27
Chapter 3 Upheaval of New Phases in Form-generating Methods Inducing
Considerable Changes in CAPP ............................................... 29
3.1 Prevalence of Highly Machining Function-integrated Kinds ............... 31
3.2 First-hand View for Innovative Attachments and Tools ........................ 38
3.2.1 Attachment and tool with modular system................................. 38
3.2.2 Attachment and tool with function-integrated type ................... 43
3.2.3 Innovative improvement of conventional tools ......................... 46
References.................................................................................................... 51
Supplements ................................................................................................. 52
Chapter 4 A New Concept for Process Planning and Its Variants - In
Consideration of Thinking Ways of Experienced Process
Planner and Innovative Form-generating Method .................... 55
4.1 CAPP of Flair Type................................................................................ 56
4.2 A New Concept of CAPP, “Thought-pattern-based Type”, and R & D
Subjects for Its Establishment ............................................................... 62
IX

References.................................................................................................... 69
Chapter 5 Concluding Remarks.................................................................. 71
Appendix Rapid Calculation Method for Machining Cost by Using HourlyRate ........................................................................................... 74

X

Chapter 1 Introduction
There have been no changes in the essential roles and characteristic featuresof process planning including its computerization, i.e., CAPP (ComputerAided Process Planning) since 1960s. In short, the production system
consists of the “Material (hardware) and Information (software) Flows”, andalso we can represent the product lifespan by the “Production Morphology”
as shown in Fig. 1.1. The production morphology is a wider scope of
hardware-oriented product lifespan, and thus it is better to discuss processplanning from the viewpoint of information flow.

Fig. 1.1 Concept of production morphology
Within the information flow, process planning plays the role of the interface(linkage) between the “Design” and the “Manufacture” in Fig. 1.1, especiallyconverting the geometrical information on the part drawing into the
manufacturing-related information, which is a “Must” in finishing the work(part or component) and assembling all the components necessary to the
product. Intuitively, the properties of manufacturing-related informationdiffer completely from those of geometrical information, and such1

characteristic features provide process planning with the very experiencedependence aspects.
At present, CAPP is in leading position with the advance of CIM (ComputerIntegrated Manufacturing) and FMS (Flexible Manufacturing Systems),
where the former and latter are roughly software- and hardware-oriented
technologies, respectively. Of notes, the utmost advanced CIM and FMS
were duly in strong fusion, resulting in FCIPS (Flexible ComputerIntegrated Production Structure) in 1980s (Ruth, Ito 2018), and one of its
successors has become the “Smart Factory Systems” in the 2000s (Ito 2017).
Even in the most advanced CAPP in the smart factory systems, without
doubts, we can observe its experience-dependence features to a large extent.

Fig. 1.2 Grass root-like knowledge necessary andinevitable in process planning2

Importantly, we need knowledge about various “Form-generating
Technologies” with wider and narrower scopes in process planning. For
example, such technologies range from the “Form-generating Movements in
Machining Space” to the “Axially Directional Orientation of Cutting Tool in
Tool Layout”.
Figure 1.2 shows such a grass-root like knowledge related to the tool layout
in the turret head, and it also suggests the very importance of paying thespecial attention to process planning when producing the part drawing.
More specifically, there are no apparent changes between both the partdrawings, apart from the end shape of long groove, either “Round” or“Square” as shown in the bottom view of Fig. 1.2. In contrast, both themachining time and the cost reduce considerable in the case of “Square
Groove”, because we can set the square end mill as same axial direction as
those of boring bar, drill and tap at the tool seat of the turret head.
This means, we can use the same axial feed in the end mill as others; whereas
we must use the radial in-feed and axial feed to generate the groove of roundend, even when using the square end mill. In addition, the end mill is liable
to deform in the latter case, resulting in the deterioration of the machining
accuracy.
As can be readily seen from the above, we must be aware of it that processplanning for a work differs more than expectation from the other, even when
the shapes and dimensions of both the works are very similar. As typicallyshown here, process planning in practice should be carried out with leverageof wider scope, e.g., linkage between CAD (Computer-Aided Design) andCAM (Computer-Aided Manufacturing), and with narrower scope, e.g.,grass root-like finishing method of the work.
Admitting that CAPP at present does not change its essential features as sameas those from the past, and involves certain shortcomings in its applicability
to the practice, nowadays CAPP faces an upheaval of new horizon in themachining space, i.e., machine-attachment-tool-work system. In fact, such a
new horizon results from a holistic effect of the enhancement of individual3technology within the machining space than ever before, as suggested in thefollowing.
(1) Prevalence of the machining function-integrated kind like TC of twinspindle type.
(2) Innovation and new contrivance in the chuck and tool of modular andcombination types.
(3) Development of tool with innovative function and performance like“Parting-off Tool Available for Reverse Cylindrical Turning (Turn-top)”.
A new horizon mentioned above appears to duly induce considerable
changes in CAPP, and thus a quick note to suggest what is under way in
CAPP in very near future is as follows.
“The more versatile a machining method by using the innovative formgenerating concept, the more necessity is to establish its effective application
to CAPP”
In fact, CAPP being used may become obsolete by growing the innovationof the form-generating function in the machining space, and thus we must
establish a new method for CAPP to actively apply such innovative functions
to it. In addition, the academic research into CAPP so far deals with thefacing problem by narrower scope, but not with wider scope, i.e., that only
considering the spot-like material removal technology, but not the formgenerating movement of machine body. In due course, it is better to discuss
CAPP as one of the total software issues within the machining space together
with concerting with its hardware aspect to a lager extent. In contrast, thechatter vibration and thermal deformation can be considered as those mainly
related to the hardware aspect within the machining space.
As will be clear from the above, we can say simply that CAPP is to mediate
CAD and CAM, and that CAPP is in mature states; however, in considerationof both the essential feature in CAPP and the upheaval of innovativetechnologies in the machining space, we must now re-investigate what is a
desirable CAPP hereafter. Importantly, we need again to delve into thefollowing fatal problems involving within CAPP at present.

4(1) Establishment for “One-to-One” conversion rule of the geometricalinformation into the manufacturing-related information. In this context,
we must be aware that the work can be finished by the preferable
integration of form-generating movement within the machining space,i.e., synergy of primary and secondary movement functions of the main
body of the machine tool itself and secondary movement functions of
the attachment and tool.
Simultaneously, we must investigate(2) an innovative concept of CAPP in very near future like “Advanced
CAPP of Flair Type”, which intends to use positively the humanintelligence-based knowledge.

References
Ito Y. (2017) Layout Design for Flexible Machining Systems in FCIPS andConvertibility to CPS Module in Smart Factory. Jour. of Machine
Engineering; 17-4: 5-28.
Ruth K, Ito Y. (Dec. 2018) Flexible-Intelligent and Smart Factory Systems.
MTEF Research Guide Series No.01. MTEF.
https://www.kousakukikai-zaidan.or.jp/en/epublication/no01

5

Chapter 2 Basic Knowledge about, Present Perspectives andFacing Issues of CAPP
With the advance of the flexible-, intelligent- and smart-factory system,
CAPP grows its importance almost daily, and as can be readily seen from
Chapter 1, we must urgently conduct two-pronged research into CAPP atpresent as follows.
(1) To enhance the applicability of CAPP to practice much more than everbefore, the improvement of conversion function from geometrical to
manufacturing-related information, i.e., rationally processing output
data from CAD to input data for CAM.
(2) In consideration of not enough applicability of CAPP at present, a
proposal for innovative CAPP based on another concept, e.g., that using
positively human-intelligence.
In such contexts, we must be duly aware that the driving force is amazingchanges in form-generating function in the machining space. Equally, wemust mind dire necessities to re-investigate what is the essential feature of
CAPP, and to unveil what are unknown inhabiting fatal shortages of CAPP
so far developed and commercialized.
Thus, we will discuss such issues in the following, especially clarifying theperspectives and involving problems of CAPP at present, and furthermore
putting main stress on the possibility of incorporating the humanintelligence within CAPP in very near future.
2.1 What Are Primary Concerns in Process Planning
In principle, we should carry out CAPP by inputting the explicit and implicit
geometrical information described on the part drawing, i.e., one of outputsof CAD, and in due course produce finally the “Process Plan (Process
Sheet)”. In other words, CAPP can be interpreted as an “Information
Processing” commencing from the “Determination of Raw Material” andterminating the “Production of Process Plan”. While dealing apparently withthe geometrical information to produce the process plan, we must, at least,6

conduct the “Process Analyses”, “Ordering Necessary Processes” and“Estimation of Machining Time and Cost”. Of course, we must convert thegeometrical information to those for machining and concerns, if necessary,so that the corresponding work is finished properly.
For ease of understanding what is process planning, Fig. 2.1 illustrates asample work and its process sheet. In the process sheet of Fig. 2.1, thearrowed line indicates roughly the order of processes, and for further
convenience, we describe the “Process Symbol”. In short, the process
symbol is legislated by JIS (Japanese Industrial Standards) and can beconverted into the “Machining Method Description”, which is compatible
with the “Functional Description of Machine Tools”. Thus, the “Process
Symbol” is one of the powerful enablers when enhancing CAPP at present
as will be discussed later in Chapter 3.

Fig. 2.1 Sample work with its process planning and conversion of “Process
Symbol” into “Machining Method Description”

7From the process plan shown in Fig. 2.1, process planning appears as to bevery easy work for people, who is not familiar process planning; however,in determining a preferable process plan, the process planner should conduct
very tedious, time consuming and pains-taking work, even when using thecomputerized process planning, i.e., CAPP.
In CAPP, we must firstly remind that primary concern is, no doubt, tominimize the machining time and cost, when the corresponding part is to be
in reality in accordance with the indication described on the part drawing.
On the strength of factory floor experience, such an economization can befacilitated by the integration of several processes, division of one process
into the proper number of individual process and elimination of undue
processes.
As can be readily seen, thus, it is wrong way to process the geometricalinformation itself, which are absolutely no relation to the machining timeand cost, without converting them into machining-related information. In
due course, at the burning issue is the conversion of geometrical informationon the part drawing into machining-related information in consideration ofdiffering characteristics between both the information. As a result, CAPP
becomes the very experience-oriented technology, and duly the matureprocess planner plays the very important role by activating her/his longstanding experience and flair.
Within this context, we must be furthermore aware that the utmost difficulty
is to establish the “One-to-One Relationship between Geometrical andMachining-related Information” as will be described later. In contrast, nearly
all CAPPs have so far dealt with only geometrical information, e.g.,
information conversion of an entity (primitive volume, feature) within a partby adding and subtracting other entities, although related people assert thatthey dealt with the “Machining-related Entities” (for further details, see
Sections 2.3 and 2.4).
Apparently, such a misunderstanding appears as to be one of causalities forthe serious shortages of CAPP at present. In the most cases, thus, the research

8into CAPP in academia has been carried out far afield from the practice,
resulting in its achievement useless for the practical work.
Of course, we have investigated CAPP of expert system to overcome such aproblem, but it is far from completion because of difficulty in establishingwell-arranged “Machining-related Knowledge Database”. Importantly, it
appears that such a serious problem in CAPP is, in part, derived from thepoor understanding of the production procedure of the part drawing.
In this context, a “Must” is to deeply understand what are the essential
features in the production of the part drawing, and of special note, theengineering designer always considers explicitly and implicitly thenecessary processes to finish the work to certain extents.

Fig. 2.2 Manufacturing-related knowledge and standards necessary inproduction of part drawing
Figure. 2.2 illustrates the production procedure of the part drawing, which
inputs the output from the “Embodiment Design” in the production
morphology (see Fig. 1.1), i.e., rough part drawing, and outputs duly thecompleted one. As shown in Fig. 2.2, both the machining-related knowledge
and the standard play the key roles in this procedure. Importantly, it can besuggested that the detailed procedure can be facilitated with the machiningrelated information to a large extent, and that the engineering designer
conducts such detailed procedure not only explicitly processing geometrical9

information, but also implicitly considering their corresponding machining
methods. For example, Table 2.1 is a first-hand view of explicit and implicit
information described on the part drawing, and furthermore Table 2.2
expounds on the examples for machining-related knowledge, i.e., those forwork grasping, which affects indirectly process planning to a large extent.

Table 2.1 Information described on part drawing

Table 2.2 Examples of machining-related knowledge necessary when
producing part drawing

10In addition to the serious problem mentioned above, another issue in CAPP
lies in an ambiguity of the boundary between CAPP and CAM (exactly
saying CAOP: Computer-Aided Operational Planning). Fig. 2.3 shows aninformation flow in CAPP and CAOP.

Fig. 2.3 Information flows and processing objectives in CAPP and CAOP
In this context, at issue is at which stage, either CAPP or CAOP, the standardrelated knowledge should be incorporated, because as exemplified at thefitting feature of two parts, the standard as per JIS B 0405 for chamferingand rounding is closely related to process planning. In general, we cangenerate such a fitting feature by “Recessing” as indicated “B” in Fig. 2.4,
i.e., “Orthodox way”; however, recess turning increases the machining cost,
and thus we must contrive another economic way, provided that theallowable accuracy is not too much higher. More specifically, chamferingand rounding can be, as shown also in Fig. 2.4, carried out by adjusting either
11the side cutting edge angle or entering angle, and choosing the preferable
nose radius of cutting edge in the single-point cutting tool, respectively.

Fig. 2.4 Chamfering and rounding as per standard for facilitating higher
assembly accuracy together with reduction of machining cost
In summarizing, it emphasizes that the part drawing and process planning
are in mutually closer relation, and the engineering designer must always bein mind all the necessary processes to produce the part being designed tocertain extent. Nevertheless, nearly all the academic investigations into
CAPP have been carried out without paying any attention to such animportant aspect in the part design procedure in practice.
2.2 Perspectives of and Leading Types in CAPP at Present
As already stated in Chapter 1, we have had a long history in R & D of CAPP,
and thus there are an uncountable number of research papers and technicalreports, and duly certain numbers of the commercialized software. In
12discussing what is under way in CAPP at present, we must first unveil withwider scope the past and present perspectives of CAPP. Then, we will discuss
what are facing problems when enhancing CAPP at present.

Table 2.3 Examples of research subjects for CAPP in 2010s
Importantly, Table 2.3 summarizes some leading research subjects for CAPP
in the 2010s. These are obtained from the literature survey, and we can see
the same techniques and involving problems as those observed within R &D carried out since 1970s. In addition, we can suggest some leading
hindrances when enhancing CAPP at present as follows.
(1) CAPPs having been and being carried out remain still in unsatisfactory
applicability to the practical work.
(2) CAPPs in academic research depart considerably from process planningin practice, because of poor understanding its essential features.
(3) The utmost causality lies in the conversion of the geometricalinformation on the part drawing into the machining-related information.
(4) The very poor knowledge about the kind of the leading machine tool in
the factory floor at present. In other words, a considerable number of
13

CAPPs rely on the old concept, in which the factory system is still basedon the production cell, job shop style, GT (Group Technology) cell andso on. In fact, it is now common sense that FMS plays major role inmachining the work, and thus we need not to choose the kind of themachine tool almost all cases at present. Importantly, the core machining
function of FMS consists, in general, of the highly function-integrated
machine tool like mill-turn.
Of these, the utmost important issue is to convert the geometricalinformation into the machining-related ones, and we can suggest two serious
causalities as will be discussed in Section 2.4.
Admitting that there are not so much CAPPs applicable to the practice, wehave had a myriad of research activities in the academia. Such states havebeen continued from the past, and for the sake of further discussion, it isbetter to classify CAPP, although we have not established the widely
acceptable classification system yet.
Figure 2.5 shows a classification system, and of these, the feature-based(primitive volume) type is dominant at present, and the “Thought Modelbased” type will be compatible with CAPP in very near future (see Chapter 4).

Fig. 2.5 Classification of CAPP
Of course, there are a considerable number of the hybrid types like a
combination of “Feature-based Type with Expert system”.
14

In consequence, there are another classification systems. For example,
someone asserts that CAPP of generative type can be interpreted as a variantof the expert system and product model type. In addition, there are various
terminologies for the “Knowledge-based CAPP”, depending upon what are
the leading characteristics to be stressed. In short, in the generative method,
one of the cores is the “Knowledge Structure”, which may be facilitated withthe flowchart, decision trees, decision tables, pattern recognition, and so on.
In contrast, in the expert system very similar to the knowledge-based type,the kernel function is the knowledge representation with “Production Rules”.
In the following, a dominant type, i.e., “Feature-based” type, and two otherrepresentative types in CAPP at present will be discussed.
CAPP of feature-based type
In feature-based type, the “Feature Recognition” is one of cores, andaccordingly, there are a handful of variants in the feature-based type
depending upon the feature recognition. For example, the feature can be
represented by the “(Directed) Graph” as shown in Fig. 2.6, where the vertex
and edge correspond with the machining feature and connecting pattern
among the vertexes concerned. As widely known, the graph can be converted
into the “Adjacent Matrix”, which is very convenient for the mathematicaltreatment.

Fig. 2.6 Graph for future recognition15

In addition, we can provide both the vertex and edge with necessary
properties like the technical data and characteristics in connecting eachmachining feature, respectively. Importantly, such applications of thedirected graph were already tried within the design methodology for themodular design of the machine tool (Ito 2008) and system layout of FMS(Ito 2014).
Conceptually, process planning can be interpreted to choose a set of vertexes
and edges from a whole combination of all the vertexes and edges, by which
all the process plans possible can be delineated. In contrast, Fig. 2.7
reproduces the sample work and its machining features delineating with the“Hierarchical Feature Tree” (Hamada et al 2012). In this case, we canproduce the “Future Tree” by considering the superiority order andcharacteristics in generating each machining feature. In addition, the feature
for reference in machining is given the utmost priority in the hierarchicalstructure.

Fig. 2.7 Concept for CAPP of feature-based type(by courtesy of Nakamoto)As can be readily seen from Fig. 2.7, we can generate the process plan bysubtracting the objective allowance from the raw material.
More specifically, process planning can be carried out as follows.
16

(1) Input: Shapes and dimensions of both the raw material and the finishedwork.
(2) After defining 16 machining features like “Face”, “Step”, “Boss” and“Side turning face”, and also establishing the “Feature Tree of
Hierarchical Structure”, the choice of one candidate group together withgiving the processing order.
(3) By comparing both the inputs, the determination of total removal features
and their division into each feature in consideration of the priority orderamong them, i.e., process planning.
In short, that of Hamada et al delves into the priority order of process,interference between the tool and work, limitation of drilling depth and so
on, resulting in better quality. In contrast, there remain something to be seen
in relation to the systematic handling for the process integration anddisintegration together with choosing the priority order in processes.
More specifically, that of Hamada involves the following problems as sameas those in other CAPPs of future-based type.
(1) Without indicating anything, the shape and dimensions of the raw
material is given. In practice, the process planner determines the raw
material after concerting various attributes in confliction among one
another.
(2) Although calling the “Machining Feature”, its property is still geometryrelated. In addition, the authors assert that the machining feature is ingood correspondence with the “Machining Method and Available Tools”.
There are however no guarantees between the machining feature andmachining method to be finished the work.
Of special interest, we may enhance such a feature-based type mentioned
above by coupling the hierarchical feature tree with the machining methodclassification of hierarchical type.
In retrospect, the feature-based type is derived from CAD of primitive(Volumetric Element, Form Element) type, where we can generate the partby adding and subtracting the basic geometrical entities (primitives). Such
CADs were developed by, for example, the CAD Centre of UK (Designing
17

with Volumes; Cantab Press, 1974) and Technishe Universität Berlin (Spur1977) . In addition, the feature-based type appears one of the variants of GT
type, which was prevailed in the first development stage of CAPP.
CAPP of GT (Group Technology) type
With the prevalence of feature-based type, GT type appears as to be obsolete;
however, GT type is even now used in practice to some extents. In fact, GT
type is very convenient when the product deployment is relatively narrow,
resulting in the less variation in machining methods. Importantly, GT type isincorporated in part within the feature-based type to ease of specification of
the machining method to the corresponding machining feature.
As widely known, GT was proposed by Mitrofanov of USSR immediately
after the 2nd World War, and firstly aimed at the rationalization of the batch
machining from the viewpoint of the cost, i.e., “Part Family Machining”. In
principle, a part should be divided into several “sub-parts (Functional
Complexes), and a sub-part and its variants are determined by theirsimilarities in machining across a group of parts. In addition, the numericalnumber, i.e., GT code, can facilitate the identification of each sub-part.
In the part family machining, the part and sub-part with the same GT codeare first gathered to consist a certain scale of group, and then machined by
the corresponding kind of the machine tool, so that the machining cost isequal or lowered as compared with that obtained by the mass-production.
In due course, each GT code has its own machining method, which is verified
its validity by the factory floor experiences, and thus it is very easy to apply
GT code to process planning. In consequence, CAPP of GT type can be
regarded as an “Experience-oriented Template Method”. More specifically,
we can produce, within less processing time, the process plan by referring to
the corresponding GT code for the given part drawing with the database. In
fact, we can extract, without any problems, the process plan when finding
the same GT code within the database, i.e., “GT Code Retrieval Method”. In
contrast, we must revise duly the process plan a little bit when finding only18

a similar GT code, and the revised one should be stored within the databasefor further application (in certain cases, called “Generative GT type).
Figure 2.8 shows schematically a part consisting of three sub-parts, and bygathering process plan for each sub-part, we can produce the final processplan for a part (Szabó Z-J, Vogel F O 1975). By it, we can increase theadaptability of CAPP much wider than that for the part itself. Importantly, akernel is thus to arrange a database, which can give us the due process planfor each GT code, reliability of which is already verified on the basis of longstanding experience.

Fig. 2.8 Variants in a primitive volume and their integration in GT type
- Modified that of Szabó in part
In due course, CAPP of GT type has two typical hindrances as follows fromthe past and even now.
(1) Because of experience-based method, only applicable to the “Variant
Process Planning”, but not for the “Free Process Planning”.
(2) The painstaking efforts are needed to prepare the database and theapplicability is limited within a certain product.
As can be readily seen, GT is the very handy and has high potentiality, andthus later it has been also applied to CAD. We must be thus aware of it thatthe “Functional Section” is, at present, called as either “Machining Feature”
in CAPP or “Geometrical Feature” in CAD.

19

CAPP of Expert System TypeAs literally shown, CAPP of expert systems aims at the positive
incorporation of the knowledge and flair of the experienced process planner,and thus one of the cores is the establishment of the knowledge database. In
general, we can represent the knowledge by the “Production Rule”, “If-ThenRule”, and so on. Up to now, however, we face certain difficulties to havethe reliable knowledge database, because of difficulties in the knowledge
acquisition. In addition, we must suggest that the expert system so far
publicized relies considerably on the knowledge database, which don’t
consider anything related to the thought pattern or thinking ways of theexperienced process planner.
In other words, the weakest point in CAPP of expert system lies in theknowledge acquisition. For example, NEDO (New Energy and Industrial
Technology Development Organization) run once the project research into
the establishment for the “Machining Database” in 2005.

Table 2.4 Organizations conducted R & D into CAPP of knowledge-based
type and expert system in 1980s
In retrospect, CAPP of expert system was once evaluated as to be very
expectable in practice such as shown in Table 2.4. Table 2.4 summarizes ahandful of organizations, at which CAPP of expert system was investigatedin the 1980s; however, these were far from the practical application, because
they were mainly investigated into the “Knowledge Processing” and“Database Structure”, provided that all the necessary knowledge were20

already obtained. In certain cases, the choice process of the kind of machine
tool was furthermore included, even though TC (Turning Center) and MC(Machining Center) became the leading machining facilities on that occasion.
To this end, it emphasizes that CAPP of expert system has not been improved
and deployed since 1980s, and its dominant causality is derived from thefierce difficulty in the knowledge acquisition from the mature processplanner. In due course, we may expect CAPP of “Thought Process-Based”
type to a large extent (see Chapter 4).
2.3 Leading Issues Inhabiting within CAPP in Details
As already suggested in Section 2.2, in principle, we must foster the humanresources and arrange the hierarchical database for machining method tosolve a fatal shortage in CAPP, i.e., not guaranteeing “One-to-One”
relationships between the geometrical and machining features.
Cultivation of human resources who can understand essential facets in CAPP
In general, people related to CAPP are liable to use the terminology,“Machining Feature” with uncertainty as exemplified by the following twocases.
(1) A review paper discusses what is “Manufacturing Features” in theapplication of STEP AP224 to CAPP for prismatic parts, and states only
one sentence, i.e., “Feature extraction and translation of design features
into manufacturing features” (Majstorović 2017). It sounds very easy toconvert the design features (geometrical features) into the machining
features; however, there are no conversions between both the features. In
fact, STEP AP224 handles only the geometrical information in detail, but
not indicating what is the actual machining method, i.e., apparently
representing “Machining Feature”, but not concretely machining method
to be applied.
(2) Some researchers state that the machining feature of “Drilled Hole” canbe defined from the technical data, e.g., diameter, depth of hole and drill
angle, on the part drawing. This “Drilled Hole” is not the “machining
21

feature”, but only represents the dimensions and shape of hole remaining
still in the geometrical feature. In fact, we must specify, at least either
twist drilling or slot drilling, which is real “Machining Feature”.
Dare to say, such a wrong interpretation happens often when the software
specialist manages CAPP, but she/he has not enough knowledge aboutmachining technology and form-generating function (hardware aspects) inthe machining space. In this context, we can observe a typical example inchoosing the kind of the machine tool, which was very popular in thesoftware of production scheduling in the past; however, such a function in
CAPP is obsolete, and CAPP renders it needles hereafter. At present, it iscommon sense that the highly machining function-integrated kind like
“Mill-turn” is primary concern in the machining space. In short,nowadays we need not any choosing procedures for the kind of themachine tool.
Establishment of “One-to-One” relationships between the geometrical andmachining features
As widely known from the past, a geometrical feature like “cylinder” can befinished by a handful of machining methods ranging from the “Cylindrical
Turning (Turn Top)”, through “Turning by Rotary Cutting Tool”, to mill-turn(see Chapter 4). Importantly, these machining methods are in hierarchicalstructure, and its structural configuration depends upon what is leading“Discriminator” like “Machining Accuracy” and “Heavy Cutting
Capability”.
Although there have been no trials so far, the author suggests two clues tosolve this crucial problem herein. One is to apply QFD (Quality Function
Deployment) of hierarchical type, and the other clue will be interrelated the“Feature Tree” or “Feature Graph” in feature-based type with the
hierarchical structure in machining method when intending to establish“One-to-One” relationship between the geometrical and machining
features (for details, see Chapter 4).

22

2.4 Another Crucial Issue by Nature – Essential Causality Departing
Academic Research from Practical Application
In general, nearly all CAPPs deal only with the geometrical addition andsubtraction of the features (primitives) without paying any attention to theirmachining methods. Even when discussing CAPP of expert system, it may
take into consideration of the apparent manufacturing-related knowledge,
but not the “Deep Knowledge”, which is not indicated on the part drawing,for example, “Leaving suitable allowance for finishing with required quality
in succeeding process”.
To exploit such deep knowledge from the part drawing, we need to establish
ourselves as the experienced and mature engineers. In due course, this
implicit information is the utmost causality departing the achievement
obtained from the academic research from the practical use. Morespecifically, we can suggest a handful of such “Deep Knowledge” in theengineering design as follows.
Changing machining requirements by counterpart – Necessity of referringassembly drawing
We face certain difficulties in understanding correctly the information
described on the part drawing, and in such a case, we must refer to theassembly drawing, otherwise we cannot produce the preferable process plan.
Figure 2.9 shows fixing of the bearing at the end of the shaft. As can bereadily seen, fixing the bearing by “Belleville washer” is not required highaccuracy in groove machining, whereas the groove should be finished withhigher fitting tolerance when fixing the bearing by the retaining ring.
Obviously, process plans for both the cases differ considerably from eachother. Thus, we must refer to the assembly drawing to produce an acceptableprocess plan, or it is desirable to indicate the counterpart by using the twodot chain line to avoid unnecessary work such as shown also in Fig. 2.9.

23

Fig. 2.9 Considerable differences in process planningcaused by counterpart

Fig. 2.10 Generation of datum for succeeding processes
while cutting work

24

Another typical example is to provide the work with a reference for the
succeeding process such as shown in Fig. 2.10. This reference is notnecessary as a function of the part when assembling in the product. In
contrast, it is a datum for gear grinding and also for the inspection of the gear
accuracy after finishing the work, and thus there is no necessity of the heat
treatment and finish grinding, although the higher fitting tolerance isrequired. As will be clear from the above, there is a certain change in processplanning as compared with that for conventional work.
Undue allowance for grasping – Cutting-off after finishing work
There are two types: one is for finishing the work with higher accuracy, andthe other is due to the restriction of the machining space, which is caused by
the functional and performance specifications of the machine tool itself.

Fig. 2.11 Undue allowance for work grasping
Figure 2.11 shows such typical examples. As can be readily seen, the undue
allowance plays only to hold the work by the attachment, but is not necessary
as a part of the finished work. More specifically, the former is for higher
accuracy turning by single-spindle turning machine. In this case, two subcylindrical entities should be in better concentricity, and thus we cannot use
any re-chucking. In contrast, the latter is for machining the splined shaft by25

using a spline milling machine of specified manufacturer-make, and ofcourse the manufacturer gives the detail of undue allowance to us.
Undue allowance for reinforcement of thin-walled work
The undue allowance is often employed to reinforce the work with thinwalled portion instead of the jig and fixture. Fig. 2.12 shows such a typicalexample in the case of box-like work. As can be readily seen from the work
configuration, the center portion of the work is liable to deform, and thus weneed to place the due “Rib” allowance. Obviously, this allowance is partedoff after finishing the work.

Fig. 2.12 Undue “Rib” allowance for reinforcemnt of“Thin-walled” portion of work
Restriction of machining space in gear grinding by machine of specified
manufacturer-make
In not only gear grinding, but also other special processing, we have certain
restriction in the shape and dimension of the work, resulting in considerable
changes in process planning. Fig. 2.13 shows such a typical example in teeth
grinding of the gang gear. More specifically, the grinding wheel affects the26span and step between the adjacent gears, and in addition, such dimensionschange depending upon the manufacturer of gear grinding machine. Thus,
Pratt and Whitney developed the gang gear of combination type as shown
also in Fig. 2.13. This excellent contrivance is based on the dexterous use of
the splined shaft together with fine thread, and of course, both the processplans differ considerably from each other.

Fig. 2.13 Different restriction in allowable work dimensions for gang gear
depending upon grinding machine of different-make

References
Hamada D, et al. (2012) Development of CAPP System for Multi-Tasking
Machine Tool. Trans. of JSME (C); 78-791: 2698-2709 (in Japanese)
Ito Y. (2008) Chapter 3 Description of Machine Tools. In: Modular Designfor Machine Tools. McGraw Hill, p.111-171.
Ito Y. (2014) Chapter 10 Similarity Evaluation for Flexible Manufacturing
Cell: An Interesting Application of Graph Theory to Manufacture. In: Ito27

Y(ed) Thought–Evoking Approaches in Engineering Problems. Springer
Verlag, p. 213-230.
Majstorović V. et al. (2017) Capp Model for Prismatic Parts in Digital
Manufacturing. https://hal.inria.fr/hal-01485815.
Spur G, et al. (1977) Computer Aided Handling of Geometric Data for
Design and Manufacturing. Preprint of 18th MTDR Conf., p. 725,
MacMillan.
Szabó Z-J, Vogel F O. (1975) Industrie-Anzeiger; 97-24: 453.

28

Chapter 3 Upheaval of New Phases in Form-generating
Methods Inducing Considerable Changes in CAPPIn discussing CAPP, it is, in principle, very convenient to employ the“Functional Description” of the machine tool, which can represent the formgenerating movement in the main body of the machine tool by using theCartesian co-ordinate system, i.e., (X, Y, Z) and (A, B, C) (Ito 2008). Morespecifically, “Must” is to represent the form-generating movement in themachining space, i.e., machine-attachment-tool-work system, together with
employing the “Process Symbol”, which is, in general, legislated within the
National Standard.

Fig. 3.1 Sample work with its process planning and conversion of“Process Symbol” into “Machining Method Description”
For ease of understanding, Fig. 3.1 reproduces a process sheet for the flangelike sample work by using the process symbol, which can be facilitated withsimilar description method as that in functional description (see Fig. 2.1).
Thus, the process can be converted into the “Machining Method Description”
without any difficulties, and then we can choose a desirable kind of the29machine tool for the given work by comparing the process symbol with thefunctional description for the machining space.
In fact, one of the cores in CAPP is to choose the machine type within thehighly machining function-integrated kind, and thus, as mentioned above,
the functional description is very useful to enhance process planninghereafter; however, there remains something to be seen in the further
applications of the functional description and process symbol to processplanning.

Fig. 3.2 Primary and secondary form-generating movements
in main body of TC (Photograph; by courtesy of Traub, 2009)
Importantly, the form-generating movement should be classified into thoseof primary and secondary types, as will be discussed later, to expound theirown important roles and effectiveness. In principle, the main body of themachine tool can conduct both the primary and secondary movements,
whereas the attachment and tool can conduct only the secondary movement
as shown in Fig. 3.2. For example, we used to apply a special boring bar and30

face plate in the horizontal boring and milling machine to the tapered holeboring and face turning, respectively, which can be classified into thesecondary form-generating movement.
3.1 Prevalence of Highly Machining Function-integrated Kinds
TC belongs to a family of “Machining Function-integrated Kinds”, and there
are two representative types, i.e., those with single- and twin-spindle, as
shown in Fig. 3.3. Importantly, TC can be characterized by the outstanding
capability of carrying out various processing methods not only machining,
but also special processing such as shown together in Fig. 3.3, where themachining method can be classified those for primary and secondary formgenerating functions. For example, grinding and gear cutting belong tosecondary form-generating function, although these are for machining, andobviously, special processing can play the role of secondary form-generating
function.

Fig. 3.3 A classification of machining function-integrated kinds in 2010s
In short, the TC can carry out a handful of leading machining methods by its
primary form-generating method, and in due course reinforce its processing
31

capabilities to a great extent by its secondary form-generating function.
Intuitively, the secondary form-generating function in TC may enhance
indirectly process planning by reducing, for example, the number of othermachines, which conduct individual processing, and thus we can economize
in transportation and preparatory work. Of note, Fig. 3.4 shows themachining spaces in TC, where the work is being ground and gear cut.
As a result, we can guess considerable changes in CAPP with the advanceand prevalence of TC as will be, for example, shown later in Fig. 3.5,
although we cannot obtain the relevant and quantitative evidence foramazing enhancement of CAPP, because of company’s confidentiality.

Fig. 3.4 Secondary form-generating function in TC
In this context, it can be furthermore suggested that TC of twin-spindle type
is one of “Highly Machining Function-integrated Kinds” and may give us
considerable effects on the CAPP. Thus we must first discuss what is theamazing change in CAPP, and to what extent we must consider the effect of
TC of twin-spindle type on CAPP. In consequence, Fig. 3.5 compares atypical machining state of the work with better accuracy by TC of either
single- or twin-spindle type.

32

Fig. 3.5 Comparison of beneficial use of twn-spindle
with conventional turning by single-spindle

33

In principle, the work should be finished its one branch at 1st machining, andthen furthermore finished the other branch at 2nd machining, after truing the
jaw and re-chucking in the case of TC of single-spindle type. Of course, inthe case of requiring much better accuracy, we must use the jig.
In contrast, we can use the “Hand-off” operation after 1st machining, andduly finish the work by the other main spindle at 2nd machining, provided
that the concentricity between both the main spindles is within the allowableaccuracy, and also the collect chuck with higher grasping accuracy should be
employed. Importantly, even in TC of single-spindle type we need not rechucking when employing the innovative cutting tool as will be discussed
later.
As will be clear from the above, CAPP depends furthermore upon the
structural configuration of the turret head including tool bracket and tool
block to some extents, and duly the number of turret heads available within
the machining space. Figs. 3.6 (a) and (b) show various configurations inturret head, and of these, both the “Twin type” and the “Conical type
(Kronenrevolver)” may function to produce valuable process planning,although it is difficult to find their effective applications to the practice. In
fact, the former increases considerably the flexibility in tool layout, and the34

Fig. 3.6 Various structural configurations in turret heads
latter can simplify tool mounting on the turret seat. More specifically, in theconical type, the turret seat is declined to the main spindle axis, and thus thetool axial direction can be positioned either along or perpendicular to themain spindle axis after indexing it to the cutting position.
Figure 3.7 shows a mill-turn, i.e., a variant of TC, with multiple turret heads
in comparison with that with milling head. Importantly, it is said that bothmill-turns have the same capabilities; however, such a discussion was carriedout without indicating the process sheets for the work shown also in Fig. 3.7.
As can be readily seen, there are a considerable number of research subjects
aiming at the rationalization of process planning by the number andallocation of turret heads within the machining space, configuration of theturret head and tool bracket, tool layout for a tool seat (see Fig. 3.6), andso on; however there have been no research activities, and there remains
something to be seen.

35

Fig. 3.7 Two representative mill-turns capable of machining
same part family (by courtesy of Traub, 2009)
To this end, we must be furthermore aware of the following. In the effective
use of “Hand-off” operation in machining with better accuracy, anotherprimary concern is to be the thermal stability of the machining space in full
reality. From such a point of view, the twin-spindle of opposite mounted typeis desirable as illustrated in Fig. 3.8. More specifically, the heat flow may becirculated duly and thoroughly across the whole machining space by
oppositely mounted both the spindle heads. As a result, we can expect
conceptually the thermally stable machining space, and such a noteworthy
design idea is credited to Hüller-Hille in 2002. At present, Index applies
such a design idea to TC and merchandizes the corresponding machine asshown in Fig. 3.9; however, such a thermal stability has not been
investigated and verified so far, although growing its importance morethan ever before.

36Fig. 3.8 Vertical turning machine of twin-spindle type possible to actualize
thermally stable machining space (Type DVT of Hüller Hille-brand, 2002)

Fig. 3.9 Mill-turn of opposite allocated twin-spindle type possible tofacilitate thermally stable machining space - Type R 200 of
Index-make (Twin-quinaxial control type)37

3.2 First-hand View for Innovative Attachments and Tools
At present, there are two representative methods within the innovative
attachment and tool, i.e., those with modular system and of functionintegrated type (combination system). Of these, the function-integrated typeis handy as compared with the modular system in practice.
3.2.1 Attachment and tool with modular system
In retrospect, the chuck and cutting tool of modular type were once prevailed
with the advance of FMS and FMC (Flexible Manufacturing Cell) in 1980s.
For example, ACC (Automatic Chuck Changer) and AJC (Automatic Jaw
Changer) were employed within FMC for turning together with cutting toolof modular type. As were expected beforehand, these modular attachment
and tool achieved considerable benefits; however, we needed to install thetransportation equipment within FMC.

Fig. 3.10 Block tooling system- A variant of modular tooling systems (By Sandvik, 1980s)
Figure 3.10 reproduces a modular tooling system of Sandvik-make in 1980s.
In due course, the cutting-edge module was contained within the tool
magazine of drum type, and in accordance with the machining requirement,38the corresponding cutting-edge module was transported from the tool
magazine to the machining space by the traveling robot. Obviously, theflexibility of the tool layout increased considerably, whereas the preparatory
time increased.

Fig. 3.11 An innovative collet chuck of modular systems(by courtesy of Hainbuch, 2016)
As will be clear from the above, the modular system is, in general, not so
effective from the viewpoint of the rationalization of process planning evennow. For example, Fig.3.11 shows the most advanced modular chuck ofHainbuch-make, which is applicable to various work grasping ranging fromthe jaw and collet chucks, through mandrel, to face driver. Figs. 3.12 (a) and(b) show furthermore modular tooling system, which can be characterized
by using, in general, the “cutting-edge of quick changing type“, and also the“Buttress Thread” to connect the cutting-edge to the tool shank module withsecure tightening. Surely, these tooling systems reinforce indirectly therationalization of process planning by their flexibility in tool layout. Of
39special notes, it emphasizes that one of leading research subjects is to seeka preferable application of the modular attachment and tool torationalization of process planning.

Fig. 3.12 Modular tooling system and cutting edge ofquick changing type around 2015
Importantly, the turret head can facilitate the primary form-generating
movement and to reinforce its flexibility, the modular tool layout is very40

effective. Figs. 3.13 (a) and (b) show two representative cutting-edge
modules and as can be readily seen, these modular tools employ the cuttingedge module only, and thus very handy together with ensuring higher rigidity
than those of modular tool in general.
There have been however no research activities for the effective
application of such modular tools to the rationalization of processplanning. More specifically, at issue is to what extent the tool layout withmodular system is applicable to the machining requirements of a partfamily and its variants. In this context, we must be furthermore aware thevalidity of the taper connection of the cutting-edge module, i.e., either
cylindrical or polygonal type (see Fig. 3.13(b)), from the viewpoint ofprocess planning.
In general, it is said that the mounting seat of polygon type is superior to thatof cylindrical type in the positioning accuracy and rigidity; however, we have
not had reliable and quantitative evaluation data so far.

41

Fig. 3.13 Modular tooling system of HSK type
To this end, it emphasizes that another facing issue in the modular toolingis to design a desirable gang tool instead of mounting a single cutting tool
on a tool seat in the turret head. In other words, in TC with multiple turretheads, single cutting tool with tool bracket mounted on one tool seat of turrethead has become very popular. It is however preferable to use the gang tool
when producing the process planning with economic efficiency, althoughsuch a trial has been very seldom so far. Typically, we may be in fruition
such tooling systems by scrutinizing the tool layout in the automatic turret
lathe and multiple-spindle automat in the past as shown, for example, in Fig.
3.14.

42

Fig. 3.14 Integration of various machining methods within one process
3.2.2 Attachment and tool with function-integrated typeIn fact, the attachment and tool with modular system are effective indirectlyon the rationalization of process planning, whereas those with functionintegrated (combination) type give us directly very beneficial effects onprocess planning.
Typically, Fig. 3.15 shows two representatives of the combination chuck andpendulum chuck for thin-walled work. The combination chuck consists ofthe face driver and jaw chuck, and first the work is held by the face driver tofinish the grasping surface while the jaw is in the retracted position. Then,the work can be held by the jaw to carry out turning for necessary formgeneration. In contrast, the latter is not of combination type, but renders the
jig useless, resulting in the reduction of preparatory work.
Within the combination tool context, there are two typical types, both ofwhich can be produced various shapes by one-hit feeding, resulting in theconsiderable reduction of the machining time. In principle, one integrates
several tools for the different machining purposes within a monolithic tool
as a whole such as shown in Fig.3.16, where the drill with chamfering and
43

Fig. 3.15 Combination and pendulum chucks forrationalization of process planning

Fig. 3.16 Examples of combination tool
depth control functions can generate the drilled hole together withchamfering the entrance of the hole. The other is of gang type consisting of
the same tools as shown in Fig. 3.17, where the boring bar for stepped holeis very popular from the past, and where the staggered gang milling cutter is
newly commercialized. Of note, the staggered gang milling cutter is very
interesting, because of facilitating the suppression of chatter vibration byshifting the adjacency cutting edge at certain angle. Importantly, there is acombination of drilling and boring, and also gang tooling as shown in Fig.
3.18.
44

Fig. 3.17 Gang cutting tools

Fig. 3.18 Multiple-spindle head for drilling and boring(by courtesy of SU-matic, 2015)45

As will be clear from the above, we can expect the considerable
rationalization of process planning by using the combination tool, and suchtools grow duly their importance almost daily. Of special note, Fig. 3.19
shows the most advanced boring tool, which is a synergy of modular andcombination types and for machining the component of the aircraft andmotorcar. Importantly, this tool can be characterized by its heavy swarf
removal, i.e., double volume than that obtained by the conventional tool, andin addition, has the following marked features.
(1) The slot drill is located at the center of the tool, and around it the face
milling cutter with staggered-tooth arrangement is mounted. As a result,
the radial component of the cutting force acting on the milling cutter canbe counter-balanced, resulting in that the resultant cutting force candirect only to the axis of the main spindle.
(2) The cutting-edge module can be located by the taper and flange
connection, which results simultaneously in the higher positioning
accuracy and rigidity.

Fig. 3.19 Boring tool of modular and combination types- Type FBX of Kennametal-make (patented, 2021)
3.2.3 Innovative improvement of conventional tools
As can be readily seen from Fig. 3.17, gang milling by a couple of grooving
cutters with staggered arrangement, i.e., cutting edges with certain phaseshift, can facilitates heavy cutting without the chatter vibration. In addition,46

a face mill of ISCAR-make appears as to be compatible with turn-milling
better than ever before such as shown in Fig. 3.20. As exemplified by these,
we may expect something noteworthy changes in process planning byimproving the traditional and conventional cutting tool.

Fig. 3.20 Face milling cutter compatible with turn-milling(by courtesy of ISCAR)
In fact, we can observe such a typical example as shown in Fig. 3.21, where
an innovative parting-off tool plays excellent roles to generate a geometricalfeature in the case of TC. In general, such a feature may generate by rechucking the work; however, a parting-off tool with higher performance thanever before can travel to axial direction after in-feeding into the work, andgenerate the cylindrical shape by the reverse feed turning. Of note, Fig. 3.22
shows a reverse feed turning by the single-point cutting tool with special
insert, which was for copy turning in the past.
In fact, there have been a handful of proposals for the innovative parting-off
tool as shown in Fig. 3.23. For example, Iscar has merchandized a partingoff tool as similar as that of ARNO, the performances of which are as follows(Werkstatt+Betrieb, September 2021).

47

Fig. 3.21 Cutting processes of work with higher accuracy
by TC of single-spindle type without re-chucking

Fig. 3.22 Reverse feed turning by single-point cutting tool for copying
lathe (by courtesy of Dieterle, 2018)48

Fig. 3.23 Innovative parting-off and slot tools driving
process planning to new horizon(1) The depth of in-feed possible is around 20 times of cutting width, e.g.,
40 mm in depth by tool with 2 mm in width.
(2) The parting-off speed is 2~3 times higher than that by traditional tool,
and we need not finish turning to the parted-off face.
In addition to the parting-off tool, we can also see the marked improvementof the slot cutter (fluting cutter) as shown together in Fig. 3.23.
Conceptually, we can classify such improvements into bifurcation way: one
can relevantly differentiate from others so far used. The other appears not tobe important, because of its “Grass Root-like Improvement”; however, itaffects considerably the rationalization of process planning as mentioned
above. Of special note, we may discuss a “Scroll-free Turning” shown in Fig.
3.24 as a typical example of the former case. This turning method can becharacterized by its helical located cutting edge made of PcBN, and also by
its skiving-like cutting mechanism. Obviously, we may use it to finish thehardened seat for bearing and oil seal, and thus expect its large potentiality
when using by TC with laser processing function.
49

Fig. 3.24 Scroll-free Turning (by courtesy of Mapal, 2014)

Fig. 3.25 Generation of shaft with non-circular cross section
by polygon cutter (by courtesy of Dieterle)

50

Importantly, Fig. 3.25 shows another interesting improvement of theconventional turning by the rotating tool like the “Polygon Cutter”, in which
the form-generating movement can be facilitated by the regulated relativerotation of the tool to the work. In fact, we can produce the flat face after
finishing the cylindrical form while maintaining the rotation of the work.
Within the grass root-like improvement, we can suggest furthermore theeffectiveness of the cutting tool with internal cutting fluid supply shown in
Fig. 3.26 on the rationalization of process planning. In this tool, the major
objective is to supply the enough cutting fluid to the cutting point together
with expecting the breakage of the long-curled swarf. The long-curled swarf
may induce the damage of the finished surface and cutting tool in certain
cases, resulting in something unfavorable cutting environment.

Fig. 3.26 Boring head and insert for internal supply of cutting fluidwith higher pressure (by courtesy of Sandvik, 2015)

References
Ito Y. (2008) Chapter 3 Description of Machine Tools. In: Modular Designfor Machine Tools. McGraw Hill, New York.
Fachartikel (3. September 2021) Abstechen mit Hochvorschub. Werkstatt +Betrieb.

51

Supplements
As typified by the gang milling cutter, we used to economize the machining
process by means of the combination tools from the past. Thus, to understandwhat are differing features in the combination tools at present from those in
the old day, some representatives so far used will be discussed in thefollowing.

Fig. 3.S1 Form-generating movement by gang milling cutter
Figure 3.S1 shows two gang milling cutters for the traditional horizontal
milling machine and planomiller, respectively. Importantly the former canbe characterized by its secondary form-generating function, which can
produce the stepped plane by one-hit feeding motion. Such a formgenerating movement is also very popular in stepped-hole boring as shownin Fig. 3.S2, and as compared with Fig. 3.17, there are no new ideas, but only
modernized.

52

Fig. 3.S2 Stepped-hole boring by multiple-edge tools
Even in the gear cutting sphere, we can observe the effective use of the
combination cutting and grinding. Fig. 3.S3 shows the combination of gear
shaping with gear hobbing, and furthermore a synergy of gear grinding andpolishing. Obviously, these are very effective to shorten the preparatory work,
and in that of Pfauter, we may expect the ease of cutting for the gang gearwith adjacency gear of larger diameter.
Within the gear production context, we can remind such an interesting
method for gear honing shown in Fig. 3.S4, in which the form-generating
movement can be facilitated by the “three leave clover-like grinding wheel”
and the “symphony of two rotating axes”. In short, Technishe Universität
Berlin proposed the original idea of this innovative gear honing and Fässler
applied it to the practical use.
Summarizing, either the integrated or multiple-edge tool in the past aimed at
the reduction of preparatory and machining time, and of course such aims
are even now primary concerns.
53

Fig. 3.S3 Integration of tools in gear production

Fig. 3.S4 Innovative gear honing- Type HMX-400 (by courtesy of Fässler, 2004)

54

Chapter 4 A New Concept for Process Planning and Its
Variants - In Consideration of Thinking Ways of Experienced
Process Planner and Innovative Form-generating Method
In accordance with the investigation into the past and present perspectivesof CAPP, as already suggested in Chapters 1 and 2, at burning issue is toestablish an effective linkage between the academic research and the practice.
In fact, CAPP being investigated in academia is far from the practicalapplication, because it is too much simplified process planning in practice.
More specifically, the utmost hindrance is to convert the geometricalinformation on the part drawing without any difficulties into the machiningrelated information together with guaranteeing the “One-to-One
Relationship” between both the information. Conceptually, all the CAPPs so
far used in practice involve this hindrance by nature, and dare to say, even
CAPP of expert system cannot overcome it, because of acute shortage of theknowledge database, which is the kernel of the expert system.
Within the “One-to-One Relationship” context, some research papers use“If-Then” rule; however, such a rule is not sufficient to solve the essential
problem mentioned above. It is furthermore said that the knowledge databaseshould be in fruition by the “Hierarchical, Modularized and Grouping
Structure”; however, there have been no acceptable proposals for suchdatabases.
A root cause of difficulties lies in the variety and complexity in themachining method to generate the same geometrical shape, i.e., geometricalfeature or primitive volume (entity). In addition, we must consider, at least,
the best availability of each machining method for the requirements inaccuracy, capability, surface quality, and duly the machining time and cost.
Thus, an idea is to positively use the “Thought-Pattern of Experience
Engineer” following to CAPP of flair type. In this context, it is desirable that
we must simultaneously establish a conversion table for the geometricalfeature to the machining method concretely available. Obviously, such a
conversion table may be also available for the improvement of CAPP atpresent.
55

4.1 CAPP of Flair TypeIn general, a crucial issue within CAPP is to establish the “One-to-One”
relationships between the geometrical and the real machining features. It isthus natural that some researchers tried to visualize the thinking way andthought-pattern of the mature process planner by using the “Questionnaire
investigation”, “Think aloud method”, “Eye mark camera method”, and soon. Simultaneously, they intended to incorporate such a thinking way within
CAPP as one of decision-making function.

Fig. 4.1 Decision-making flow of mature process planner- Visualization by directed graph
Figure 4.1 shows a directed graph in general, which can visualize a decisionmaking procedure of the process planner (Chen 1985). In fact, we can56

produce the directed graph by the “Face-to-Face Interview” or“Questionnaire Investigation”, where the core item (vertex with property
description) is pre-given. More specifically, the subject should connect all
the vertexes by the directed edges, which are necessary and inevitable todetermine a vertex. Obviously, this is one of indirect visualizations for thethought-pattern of the process planner, and as can be seen, the circulating
directed edges imply the cause of the “Ill-defined Problem”-likecharacteristic in process planning. In addition, we can observe several
interesting matters as follows.
(1) There are certain numbers of variants in the directed graph depending
upon the maturity, and also culture and mindset aspect of the subject,even when all the subjects belong to the same organization. In fact, twoengineers belonging to the same organization produce different processplans with each other, and both the plans are acceptable, but not theupmost desirable one.
(2) The same subject shows a different directed graph from those obtainedat another days. This means, the decision-making process is influenced
considerably by the mental and physical conditions of the subject.
(3) The pattern of the directed graph changes to a great extent, i.e., lessnumbers of circulating edges, when providing the subject with such apart drawing, i.e., geared drive shaft, as a “Stimulus”. Fig. 4.2 shows anexample, and we can see the strong individual dependence, although thecirculating directed edges reduce considerably in general. In addition,
the “Stimulus” induces a new vertex, i.e., GR, which plays certain
important role to the pattern of the directed graph.
Of special note, we must be aware of it that the directed graph can beconverted into the adjacent matrix, which is very convenient to themathematical treatment.
Such a visualization by the directed graph is worth evaluating the decisionmaking of the process planner; however, it involves uncertainties caused by
the leading question-like aspect to some extents, and thus Ihara and Ito(1991) proposed to use the “Eye mark Camera” to avoid such uncertainties.
57

Fig. 4.2 Directed graph when providing part drawing
Fig. 4.3 illustrates the testing setup and shows an example of the test result.
As will be clear from Fig. 4.3, the subject reads the part drawing projectedon the large screen and simultaneously conducts process planning. While thesubject produces the process plan, the eye mark camera records the
movement of the eyeballs, i.e., moving direction and watching time at the
special point on the part drawing, which may reflect indirectly the decisionmaking procedure of the subject.
Of note, the more numbers of the circles around a point, the subject isstrongly interested in it, and also the longer the watching time, the larger isthe recorded circle. Obviously, the latter means that the subject needs
something necessary to understand the meaning of the watched point.
Through the eye mark camera testing, we can first obtain to what attributes
the subject is extremely interested in by investigating the earlier watching
points immediately after starting the test. From a couple of such test results,
it is clarified that the mature process planner uses a weighing principle tochoose the priority order among all the attributes related to process planning.
58

Fig. 4.3 Eye mark camera testing and a recorded result
More specifically, the mature process planner chooses several leading
attributes from 1st to 4th such as shown Fig. 4.4, while conducting processplanning. As a result, the process planner does not spend much more time to
produce the process plan, which is, in general, acceptable with high quality.
In contrast, nearly all CAPPs put, in general, the same weights on all theattributes, resulting in the time-consuming work.
In consequence, Ihara et al proposed an idea of CAPP of Flair type, in which
the process planner discriminates several routes to produce the process plan,
depending upon which leading attribute is in much more priority. Obviously,both the higher machining accuracy and the difficult-to-machining play theimportant roles, and thus we need to evaluate the difficult-to-machining.

59Fig. 4.4 Priority order of attributes on part drawing
in producing process plan by mature engineer
Thus, Ihara et al (1993) presume that the difficult-to-machining may be
represented with the mutual relationships among the attributes related to“Thinkable Troubles in Machining” and “Possible Remedies for Troubles”.
In consideration of the ease of mathematical treatments, such relationships
are visualized by the directed graph as shown, for example in the case of thecylinder with thin wall in part, in Fig. 4.5.
After conducting a handful of trials, they can obtain a normalized directed
graph by extracting the common patterns from the trial results as shown in
Fig. 4.6, where we can find some attractive facts as follow.

60

Fig. 4.5 Directed graph delineating “Difficult-to-machine”
for thin-walled cylinder

Fig. 4.6 Normalized directed graph to visualize “Difficult-to-Machining”
61(1) The “Difficult-to-Machining” can be detailed into the “Complexity in
Machining” and “Real Difficult-to-Machining”, which can be visualized
by the “Tree Structure” and “Loop Structure”, respectively.
(2) The “Real Difficult-to-Machining” can be evaluated the number of“Loops” and “Circulating Loops”, and the much more the latter, the“Difficult-to-Machining” increases much more.
(3) The “Complexity of Machining” does mean nothing even when it showscomplicated flow. In fact, the mature process planner does not pay any
attention to it.
4.2 A New Concept of CAPP, “Thought-pattern-based Type”, and R &D Subjects for Its Establishment
Following to CAPP of flair type, thus, a concept for new CAPP may be basedon the positive use of the “Thought Pattern of Experience Engineer”, andFigs. 4.7 (a) and (b) are first-hand conceptual views of the proposed idea.

62

Fig. 4.7 Concept for CAPP of “Thought Pattern-based” type
In principle, the proposed idea consists of two cores, which can becharacterized as follows.
(1) First screening phase based on thinking ways of mature process planner.
(2) Second screening phase based on thought pattern of engineering designer
Within Fig. 4.7 context, the mature process planner may decide whether the
chatter vibration occurs or not, at glance the part drawing. To our regret, wehave not visualized such a decision-making procedure of the matureengineer yet, resulting in R & D subject in future. In general, the thinwalled work may induce the chatter vibration, and thus we need to reinforce
such a geometrical feature with jig and fixtures, or with “Cut-off Rib” afterdue machining (Undue Rib).
As can be readily seen, a new idea may be in fruition by establishing twocore functions, i.e., procedure for raw material determination and structuralorganization of database together with identifying the determinant.

63

Procedure for raw material determination
As will be easily imagined, we need various and wider knowledge to carryout the procedure for determining the utmost desirable raw material
corresponding with the part drawing. For example, we must determine to use
either the draw bar or forged cylinder, even when the material indicated on
the drawing is the same. Of course, such a knowledge ranges from theproperties of engineering materials in general, through form-generating
movement of the machine body and attachment, to “Do-It-Yourself” tool. In
principle, we must use the general knowledge about the engineering material
regulated in the standards; however, such a knowledge renders often useless,and instead of them, we must rely on the factory floor-based data.

Table 4.1 Some determinants for choosing preferable raw material
Conceptually, this issue is closely related to the problem regarding “What isthe part drawing with better quality”. In this context, we must recall that theengineering designer conducts often, without any consciousness, the choiceof the preferable raw material while producing the part drawing. Such anactivity of the engineering designer lies in “Implicit thought pattern” and is64

a “Must” to produce the part drawing with the best quality. Importantly, theimplicit thought pattern can be interpreted as a rough process planningbeforehand. Thus, we must visualize such a thought-pattern by, for example,“Think aloud method” and describe, at least, the determinants as shown in
Table 4.1. Obviously, there remain something to be seen in the visualizationof the determinants, which are closely related to the experience-oriented
knowledge.
Database structure
We can classify the machining methods to generate the same geometricalfeature by the hierarchical system as shown, for example those forcylindrical turning (turn-top), in Figs. 4.8 (a), (b) and (c). In due course, afacing issue is what is a desirable database structure to fulfill the “One-toOne Relationship” mentioned above; however, at present, we have no ideas.
Thus, Fig. 4.9 is a proposal based on QFD (Quality Function Deployment)(Höft 1999), and more specifically, the proposal can be characterized asfollows.

65

Fig. 4.8 Fundamental type, its variants and special types in cylindricalturning together with their functional descriptions
66

Fig. 4.9 Database concept to generate utmost desirable
machining method by QFD(1) In consideration of core attributes possible to extract from the partdrawing, the characteristic features of each machining method should be
evaluated.
(2) The core attributes obtained from given part drawing should becompared with those of each machining method, and some preferable
methods should be chosen.
(3) By using a representative index, e.g., “Ease of Use”, the utmost suitable
method should be determined among some candidates.
Of course, the database mentioned above is also available for the traditional
CAPP of generative type.
As can be readily seen, within the weight rates in Fig. 4.9, the further R &D subjects are as follows.
(1) Determination for characterizing functions of each machining method by
six leading attributes, i.e., machining accuracy, capability, machining
time and cost, and furthermore the batch size and work material. In
67

common senses, we believe that such characterization data were alreadyin fruition; however, such a belief is “Myth”. In fact, we must belatedly
establish the characterization data in satisfactory states. For the sake offurther understanding, a forerunning achievement is shown in Fig. 4.10,
which was carried out by Sorge (1984) in consideration of three
representative attributes, i.e., configuration complexity and shapegeometry deviation in part, and also the type of swarf.
(2) Definition of “Ease of Use” and its evaluation, which can quantify
obviously the differing features among various machining methods togenerate the same geometrical feature.
(3) Investigation into another suitable “Index” for choosing the optimum
machining method rather than “Ease of Use”.

Fig. 4.10 Comparison for available ranges of turning in general,
whirling and turn-milling in consideration of three attributes(by Sorge, 1984)
Admitting that QFD may facilitate to give a sure-handed relationshipbetween the geometrical feature to the preferable machining method, we
68need furthermore a diagram indicating possible linkages among themachining method, types of cutting tools, turret head types and machinekinds such as shown in Fig. 4.11.

Fig. 4.11 Linkage diagram ranging from machining method
to structural configuration entities - Turn-top

References
Chen M-F, Ito Y. (1985) Investigation on the Engineer’s Thinking Flow in
the Process Planning of Machine Tool Manufacturer. In: 13th NAMRC Proc.,
NAMRI of SME, Michigan, p. 418-422.
Höft, K (March, 1999). Culture- and Mindset-Harmonised Manufacturing in
Sustainable Global Environments. Dissertation, Tokyo Institute ofTechnology.
Ihara T, Ito Y. (1991) A New Concept of CAPP Based on Flair of Experienced
Engineers – Analyses of Decision-Making Processes of Experienced Process
Engineers. Annals of CIRP; 40-1: 437-440.
69

Ihara T, Ogawa M, Ito Y. (1993) An Evaluation Method of Complexity andDifficulty of Difficult-to-Machine Portions for CAPP Based on Flair. Jour.
of Precision Engineering. 59; 3: 435-440.
Sorge K-P. (1984). Die Technologie des Drehfräsens. Darmstädter
Forschungsberichte für Konstruktion und Fertigung. Carl Hanser Verlag,
München.

70

Chapter 5 Concluding Remarks
In short, process planning at present has been considered in mature states,
although its quality depends upon the competency of the experienced
engineer to a great extent. With the advance of individual technology, which
consists of the machining space, i.e., machine-attachment-tool-work system,
however, process planning so far used is duly forced to change or shouldchange itself as can be readily seen from the main body of this book.
Nevertheless, it is, in general, difficult to find the forerunning andchallenging research into an innovative CAPP, which is compatible with themachining environments in the year 2020 and beyond. In fact, the smart
factory is at crucial issue, and duly a new CAPP should be investigated;
however, there have been, for example, no interesting applications to the“Open Project Research being conducted by MTEF” over a couple of years.
This is very incredible, and thus the author would like to encourage theyoung researcher in conducting the research into an innovative CAPP byreferring to this book.
Of special notes, we face now to contrive process planning compatible withnew machining environments, and to do so, we must overcome two serious
hindrances. One is, as already mentioned in detail, to establish the “One-toOne Relationship between Geometrical and Manufacturing-relatedInformation”, and the other is to establish a methodology for processplanning, where we must, at least, consider the linkage diagram shown
already in Fig.4.11.
Importantly, we have not had any methodologies for process planning,
because of its complexity resulting from the numerous numbers of attributes
being concerned, and also the necessity of incorporating grass root-likefactory floor knowledge. For example, Fig. R.1 shows a typical grass rootlike knowledge about machining and assembly technologies at the joint faceof headstock with top cover, when guaranteeing the oil tight witheconomization. In fact, we used to apply the joint face without overhang,although it is very costly. In contrast, we can benefit economically by
employing the top cover with overhang, which can play desirable oil tight,
71

Fig. R.1 A remedy for reduction of machining and assembly cost
- In case of oil tight between headstock body and top covereven though the joint face is rough-machined. In addition, another issue is
how to transfer the manufacturing-related knowledge of the engineering
designer while producing the part drawing into the methodology. For
example, Table R.1 shows such knowledge in general.
In principle, we can understand the importance of these mentioned above;
however, there are no ideas at present regarding what is desirable
methodology in practice, and in due course, we face considerable difficulties
in conducting the academic research itself.
To this end, it emphasizes that another CAPP should be established forresurrecting the recycled part and unit, which will be supplied to theassembly process in manufacturing in consideration of re-manufacturing
shown together within Fig. 1.1. For example, we need to develop processplanning for disintegration of recycled unit with reminding that thedisintegration of the unit differs from its assembly to a large extent, e.g.,loosening tightening bolt with rust, dust and sand-like particles. In case ofmachining, the recycled piston should be first milled to take off pitching72

caused by the operation, then overlaid by the Cr- or Ni-based alloy, andfinally finish-machining.

Table R.1 Manufacturing-related knowledge being consideredwhile producing part drawing by engineering designer

73

Appendix Rapid Calculation Method for Machining Cost by
Using Hourly Rate
In conducting process planning, we must always pay the special attention to
the machining cost, and thus, we need to have a rapid calculation method forthe machining cost.

Fig. A.1 Simple formula for machining cost
In this context, we used to a simple method based on the “Hourly Cost” asshown in Fig. A.1. Obviously, each machining method has its own hourly
cost, and the total machining cost for a corresponding work can be obtainedby summing up those for each machining method after carrying out thecalculation procedures shown in Fig. A.2. In consequence, the hourly cost
can be determined in various ways depending upon the organizational
circumstances of each enterprise. For example, Km can be determined inconsideration of depreciation cost of machine tool and transportation cost of
materials in certain cases.
For the sake of further understanding, a sample of the cost calculation isshown in Fig. A.3.
74

Fig. A.2 Calculation procedures for machining cost

Fig. A.3 Rapid calculation of machining cost by hourly rate
To this end, it emphasizes that the machining cost can be reduced by
preferably using the grass root-like remedies such as exemplified in thefollowing.

75

(1) When producing the part drawing, a “Must” is to employ the throughdrilling, reaming and tapping instead of those with pocket holes as
possible as we can.
(2) We must use positively some major shapes and leading dimensions of
cutting and grinding tools, and also attachments, which are regulated byvarious Standards. For example, rounding and chamfering produced by
the single-point cutting tool as per the standard can reduce the machining
cost together with guaranteeing the out-of-square accuracy in assembling
both the parts (see Fig. 2.4).

76