Method for determining inner diameter machining method in numerical control information generating function

For the function of forming numerical control information prior to machining process, the type of machining (such as drilling, end milling, outer diameter end face, etc.) and machining scope for each machining area is determined by inputting the shapes of a work and a part determining the machining areas based on said shapes, identifying the areas for inner diameter machining out of said machining areas, extracting from said inner diameter machining areas those characteristic areas to the inner diameter machining such as the area where a rear end face exists on the part shape, where a through hole is unprocessed or where a through hole is bored on the work based on the shape elements. As this method does not require preliminary reviewing of the machining method for inner diameter (and especially for small diameter), it allows beginner operators to produce numerical control information as easily as a skilled operator.

BACKGROUND OF THE INVENTION 
The present invention relates to a method for determining a machining 
method in the numerical control information generating function which 
forms information for numerical control prior to machining, and more 
particularly to a method for determining the type and scope, i.e.-inherent 
limitations, of the machining in each step in an inner diameter machining. 
There has been realized a numerical control information generating function 
which, when necessary data are inputted using a graphic display screen of 
the interactive type, forms the numerical control information such as NC 
programs from design drawings. This function permits inputting of the 
shape to be machined simply by pressing suitable keys on the panel 
according to the shape of component part on the design drawings. In the 
numerical control information generating function as above described, 
information necessary for setting data is conveniently displayed in 
graphics, and various data such as dimensions may be inputted in response 
to questions asked in easy and everyday language which laymen can 
understand. Furthermore, as soon as all the data necessary for forming 
numerical control information are inputted, the shape of a blank or the 
shape of a machining is instantly displayed, automatic calculation of 
numerical control data is started, tool tracks are graphically displayed 
and the numerical control information is formed. 
The function of the numerical control information generating function 
generally comprises the following steps 1 to 10: 
1. Selecting a work material 
2. Selecting a graphical type 
3. Inputting the shape and dimension of a work 
4. Inputting the shape and dimension to be machined 
5. Inputting the original point of the machine and the turret position 
6. Selecting the types of machining 
7. Selecting tools 
8. Determining the scope, i.e.-inherent limitations, of each type of the 
machining 
9. Inputting the cutting conditions 
10. Calculating the tool paths 
Necessary data are sequentially inputted to eventually form the numerical 
control information. 
In the conventional function described as above, after the steps of 
inputting the blank shape and the machining shape, an operator determines 
which area of the blank should be machined in each step and what tool 
should be moved in which direction, and determines the order of use of the 
tools, and inputs the necessary data according to the order thus decided. 
Although the conventional method is flexible as the operator can freely 
select the order and scope of use of the tools, the operator requires 
certain skills and experience with regard to machining and therefore, a 
beginner operator sometimes finds the step of setting various data 
difficult and cumbersome. 
The conventional method requires a great deal of time in inputting the data 
since it requires selecting the types of machining, determining their 
order, and inputting each type of tool, cutting direction, machining 
scope, i.e.-inherent limitations, and cutting conditions for each type of 
machining. In order to overcome such short comings, Japanese Laid-Open 
Patent Application No. 126710/1985 teaches a method which stores in 
advance the order of the machining steps, evaluates for each step which 
machining types are necessary in the above order, and automatically 
determines, if necessary, the scope and cutting direction for each given 
machining operation. However, it teaches only one way of determining which 
types of machining and their scope are necessary. Particularly, in the 
case of inner diameter machining, where various machining steps are needed 
depending on the shapes and size of each of type of machining and the 
blanks, it becomes impossible to select an optimal type and scope of 
machining. For example, when the machinings are to be roughly machined 
from the blanks as shown in FIGS. 1A, 1B and 1C, the types of the 
machining to be selected by the conventional method are determined 
indiscriminately: 
center counterboring 
drilling 
rough machining of inner diameter 
and the machining scopes are determined as shown in FIGS. 2A, 2B and 2C. 
However, when an operator actually designates the types and scope of the 
machining, the types of the machining for the case FIG. 2A will be: 
end face rough machining 
rough machining of inner diameter 
and the scope of the machining becomes set as shown in FIG. 3A. In the case 
of FIG. 3B, the types of the machining are generally set: 
center counterboring 
drilling 
end milling 
rough machining of inner diameter 
while the machining scope is set as shown in FIG. 3B. Moreover, in the case 
of FIG. 3C, the types of the machining are: 
end milling 
rough machining of inner diameter 
and the scope is set as shown in FIG. 3C. 
As illustrated as above, the conventional method could not quite correspond 
optimally to the various needs in the machining steps as the types and 
scope of the machining are determined without considering the shape and 
dimension of the machinings and the blanks. 
Although the conventional automatic programming systems automatically 
determine the type and scope of the machining for machining a part simply 
by inputting the shapes of the machining and the blank, none of them can 
determine the types of machining after evaluating the shapes and size of 
the areas to be machined that are defined by the shape of the machining 
and the blank. They could only determine unilaterally the type and scope 
of the machining for inner diameter machining (especially small diameters) 
which requires various machining methods depending on the shapes and size 
of the machining area. 
SUMMARY OF THE INVENTION 
The present invention was contrived to solve such prior art problems as 
described above, and aims at providing a method for determining a 
machining method for inner diameter in the function of numerical control 
information generating which can determine the type and scope of machining 
for each step depending on the characteristics of the shape of each 
machining or blank without the necessity for the operator to review the 
machining method before data input, and which is so easy and simple in 
operation that beginners having no skills and experience on complicated 
inner diameter machining methods can easily handle the method. 
According to one aspect of the present invention, for achieving the objects 
described above, there is provided a method for determining an inner 
diameter machining method in the numerical control information generating 
function which forms information for numerical control prior to machining, 
and which comprises the steps of: inputting a blank shape and a machining 
shape on which the machining is to be conducted; determining a machining 
area based on the inputted shapes; identifying areas for an inner diameter 
machining within said machining area, and extracting characteristic 
machining areas for various machining methods in the inner diameter 
machining within said inner diameter machining area based on machining 
element data thereof so as to automatically determine the types and scope 
of machining for said characteristic machining areas. 
The nature, principle and utility of the invention will become more 
apparent from the following detailed description when read in conjunction 
with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention will now be described in more detail referring to 
preferred embodiments shown in attached drawings. 
FIG. 4 is a block diagram showing a system which realizes the method for 
determining an inner diameter machining method in the numerical control 
information function according to the present invention. 
An operator inputs blank shapes and machining shapes from a keyboard 6 
while confirming on the display unit 5 the entry of the inputs. The input 
blank shapes and machining shapes are developed into shape element strings 
and stored in a blank/machining shape memory 3. The shape element strings 
are described below. As shown in FIG. 5, the element shape comprises blank 
shape element strings l.sub.w1, l.sub.w2, . . . , l.sub.w8, while the 
machining shape comprises machining shape element strings l.sub.p1, 
l.sub.p2, . . . , l.sub.p10. Elements in the shape element strings 
comprise respective data on position, shape and size which are sufficient 
to specify a graphic figure. 
A processor 1 generates a shape element string which forms a machining area 
based on the blank shape element strings and the machining shape element 
strings and stores them in a temporary memory 4. The shape element strings 
which forms the machining area may be obtained from the machining 
shape/blank shape of FIG. 5 as shown in FIG. 6 below: 
Machining area 1 
blank shape element string: l.sub.w '.sub.6 .multidot.l.sub.w7 
.multidot.l.sub.w8 .multidot.l.sub.w1 .multidot.l.sub.w '.sub.2 
machining shape element string: l.sub.p3 .multidot.l.sub.p2 
.multidot.l.sub.p1 .multidot.l.sub.p10 .multidot.l.sub.p9 
Machining area 2 
blank shape element string: l.sub.w '.sub.3 .multidot.l.sub.w4 
.multidot.l.sub.w '.sub.5 
machining shape element string: l.sub.p6 .multidot. 
The blank shape elements attached with the symbol "'" means that they are 
the elements obtained by subtracting from original blank shape the 
portions which overlap with machining shape elements. 
Then, the processor 1 forms a shape element string which forms an inner 
diameter machining area based on the inner diameter machining scope and 
the machining areas 1 and 2 and stores it in the temporary memory 4. The 
inner diameter machining scope is the scope which is determined on the 
premise that outer diameter and inner diameter machinings are to be 
conducted after an end face is machined, such as the portion shaded in 
FIG. 7. In other words, the inner diameter machining area which should be 
machined on the inner diameter is the machining area which exists within 
the inner diameter machining scope, such as those shaded in FIG. 8. 
Inner diameter machining area 1 
blank shape element string: l.sub.wI1 .multidot.l.sub.wI2 
machining shape element string: l.sub.pI1 .multidot.l.sub.pI2 
Inner diameter machining area 2 
blank shape element string: l.sub.wI3 .multidot.l.sub.wI4 
.multidot.l.sub.wI5 
machining shape element string: l.sub.pI3 
The symbol l.sub.wI1 indicates a blank shape element which is newly 
produced by the boundary line of the inner diameter machining scope, and 
the symbol l.sub.wI2 the blank shape element produced by separation of 
l.sub.w '.sub.2 by boundary line of the inner machining scope where 
relations below hold. 
EQU l.sub.pI1 =l.sub.p3 
EQU l.sub.pI2 =l.sub.p2 
EQU l.sub.wI3 =l.sub.w '.sub.3 
EQU l.sub.wI4 =l.sub.w4 
EQU l.sub.wI5 =l.sub.w '.sub.5 
EQU l.sub.pI3 =l.sub.p6 
Then, the processor 1 generates machining steps for the inner diameter 
machining area, but description will first be made on the definition of a 
machining scope and on the renewal method of a the machining area. The 
machining scope is these areas within the machining area which should be 
cut off by the step. In the steps using a drill or an end mill, it means 
the portions where the tool shape overlaps the machining area when a tool 
with a predetermined diameter is moved from a starting point to an end 
point. More specifically, they are the portions shaded in FIGS. 9A through 
9C. The renewal of the machining area means the step of removing the 
determined machining scope from the machining area. Referring to the 
machining shape/blank shape and the machining area shown in FIG. 9A, as 
shown in FIG. 10A. 
Inner diameter machining area 
blank shape element string: l.sub.wI1 .multidot.l.sub.wI2 
machining shape element string: l.sub.pI1 .multidot.l.sub.pI2 
is renewed as follows (FIG. 10B): 
Inner diameter machining area 
blank shape element string: l.sub.wI3 .multidot.l.sub.wI4 
.multidot.l.sub.wI5 
machining shape element string: l.sub.pI1 .multidot.l.sub.pI2 
The method of machining step generating for the inner diameter machining 
area will now be described referring to the flowcharts shown in FIGS. 11 
through 15B. All the processings such as judgement in the following 
description are conducted by the processor 1. 
In Step S1, a judgement is made as to whether or not the machining shape 
elements forming an inner diameter machining other than the 
longitudinal/end face exist on a diameter smaller than the minimum 
machining diameter (referred to as .alpha. hereinafter) of the lathe 
turning tool which has been stored in the parameter memory 7 in advance, 
and if there is no such machining shape element, the step proceeds to Step 
S3 but if such an element exists within the diameter, the step proceeds to 
Step S2. At Step S2, taper/arc (including chamfer/rounding) on a diameter 
smaller than the minimum machining diameter .alpha. must be machined in 
the boring process, but as it is impossible to completely cut without 
leaving some area unless a forming tool is used, such an incomplete cut 
should be kept minimum. The machining shape is corrected by forming a 
virtual machining shape element by connecting a vertical extension of an 
end face element from the point X=.alpha. with an extension of the 
longitudinal element existing in the area X&lt;.alpha. but having the minimal 
X value on the machining shape. Through these steps, the machining shape 
and the machining area shown in FIGS. 16A and 17A are corrected as shown 
in FIGS. 16B and 17B respectively. If there is no such longitudinal 
element in the region of X&lt;.alpha., X=0 is used as the longitudinal 
element. 
At Step S3, the step jumps to the subroutine shown in FIGS. 12A through 12C 
for forming the inner diameter rough machining step. 
At Step S301, it is judged whether or not an inner diameter machining area 
exists, and if not, the process returns to the step (or Step S4) 
immediately after Step S3, and if it does, the step proceeds to Step S302. 
Whether or not a machining area exists is judged by judging if there 
exists a shape element string by offsetting overlapping of the machining 
shape elements and the blank shape elements in a machining area. A 
machining area in the rough machining means a machining area obtained by 
assuming the final machining shape plus a finishing allowance as the 
machining shape, the machining shape in the rough machining means herein 
the machining shape including the finish stock. At Step S302 a judgement 
is made as to, whether or not there is a through hole bored on the 
machining shape, and if there is no hole, the process advance to Step 
S305, but if there is a through hole, it goes to Step S303. At Step S303 a 
judgement is made as to, whether or not a through hole exists on the blank 
shape and if not, since the machining shape is a bored through hole, it is 
recognized as a machining area characteristic to the inner diameter 
machining with an unprocessed through hole, and the process goes to Step 
S316 in FIG. 12B which indicates the method for machining such an area. 
Otherwise, the process goes to Step S304. At the Step S304, the minimum 
value (referred to as the blank shape element minimum diameter) of the 
blank shape elements forming the inner diameter machining area in the X 
direction is compared with the minimum value (referred to as the machining 
shape element minimum diameter) of the machining shape elements in the X 
direction. If the minimum diameter of the blank shape elements is the 
smaller of the two values, it is judged that there is a through hole in 
the blank, and that a machining area should exist at the through hole, and 
the process goes to Step S307. Otherwise, it goes to Step S305. It is 
judged at Step S305 that the machining area exists only on the portion of 
a blind hole or on what may be recognized as the blind hole, and that it 
is not necessary to machine the through hole of the part even if there is 
one. In Step S305 the blank shape element minimum diameter in the inner 
diameter machining area is compared with .alpha., and if the minimum 
diameter is larger than .alpha., the whole machining area is judged to be 
machinable by lathing the inner diameter. Steps for the rough machining by 
turning are formed (Step S306), and then the process goes to Step S315. 
Otherwise, it is recognized as the machining area characteristic to the 
inner diameter machining with a rear end face, and the process advances to 
Step S335 of FIG. 12C which indicates the machining method for such an 
area. At Step S307, a comparison is made between the blank shape element 
minimum diameter of the inner diameter machining area and .alpha.. If the 
blank shape element minimum diameter is larger than .alpha., the whole 
machining area is judged to be machinable by turning the inner diameter, 
and the process advances to Step S306. Otherwise, it is recognized as the 
machining area characteristic to the inner diameter machining with the 
through hole in the blank, and the process goes to Step S308. 
Referring now to FIG. 18A, the process of Step S308 and thereafter will be 
explained. At Step S308, the machining shape element minimum diameter in 
the machining area characteristic to the inner diameter machining is 
compared with .alpha.. If the machining shape element minimum diameter is 
larger than .alpha., or if the X coordinate at l.sub.pI1 &gt;.alpha., it is 
judged that the portion of the machining shape element minimum diameter 
could be improved in surface roughness due to rough machining by end 
milling and turning, and the process proceeds to Step S309. Otherwise, it 
is judged that the portion of the part shape element minimum diameter can 
only be roughly machined by end milling alone. The diameter of the end 
milling for the rough machining for determining the scope is set as the 
machining shape element minimum diameter (Step S313), and the process goes 
to Step S314. At the Step S309, a calculation is made as follows. 
##EQU1## 
The drill deviation allowance means the maximum value of deviation by a 
twist drill or an end mill during a boring operation. The numeral D.sub.1 
indicates the maximum diameter of the tool which can machine without 
lowering cutting conditions. At Step S310, the diameter D.sub.1 is 
compared with the maximum diameter stored in the parameter memory 7 in 
advance for an end mill which is attachable on the machine, and if the 
value D.sub.1 is smaller than the end mill maximum diameter, the 
relationship is set as the roughing end mill diameter=D.sub.1 (Step S311). 
Otherwise, the roughing end mill diameter=(end mill maximum diameter), and 
an arrangement is made to use an end mill having the largest possible 
diameter which is still mountable on the machine (Step S312). At Step 
S314, the machining scope is determined based on the tool diameter 
determined at Step S311, S312 or S313 (see FIG. 18B), and the types and 
scope of the machining are stored in the temporary memory 4. At Step S315, 
the machining area is renewed based on the determined machining scope 
(FIG. 18C) and the process returns to Step S301. 
The steps after Step S316 of FIG. 12B for the machining area characteristic 
to the inner diameter machining with an unprocessed through hole will now 
be described referring to FIGS. 19A, 20A and 21A. 
At Step S316, the diameter D.sub.1 is calculated in a process similar to 
that of Step S309. At Step S317, the maximum diameter (referred to as the 
drill maximum diameter herein) of a drill mountable on the machine which 
has been stored in the parameter memory 7 is compared with the value 
D.sub.1, and if the value D.sub.1 is smaller than the maximum diameter, 
the relationship is set as the virtual drill diameter=D.sub.1 (Step S318). 
Otherwise, the virtual drill diameter is set at the maximum drill 
diameter, and a drill having diameter as large as possible is assumed 
(Step S319). The virtual drill diameter is determined at Steps S320 and 
S322 for allowing a judgement based on the machining scope of the assumed 
drill. At Step S320, the quotient (referred to as the width/length ratio) 
obtained by dividing the length of the machining scope by the assumed 
drill in the Z direction with the maximum coordinate in the X direction is 
compared with the minimum width/length ratio (expressed by the symbol 
.zeta.) stored in the parameter memory 7 in advance for the machining 
scope which requires machining by a drill, and if the width/length ratio 
in the assumed drill machining scope is less than .zeta., the machining 
scope is judged too shallow and no drilling is necessary, and the process 
advances to Step S321. Otherwise, it is judged that drill machining is 
necessary and the process goes to Step S322. 
At the Step S321, the value D.sub.1 is compared with the maximum end mill 
diameter, and if the value D.sub.1 is smaller than the maximum end mill 
diameter, the relationship is set that roughing end mill diameter=D.sub.1 
(Step S323). Otherwise, the roughing end mill diameter is set at the 
maximum end mill diameter, and an arrangement is made to use an end mill 
having the largest possible diameter still mountable on the machine (Step 
S324). At Step S325, based on the tool diameter determined at Steps S323 
and S324, the machining scope is determined (see FIG. 19B) and the types 
and the scope of the machining are stored in the temporary memory 4, and 
the process goes to Step S315 in FIG. 12A. At Step S322, a comparison is 
made between the width/length ratio of the drill machining scope and the 
width/length ratio (referred to as the symbol .beta. herein) stored in 
advance in the parameter memory 7 for the machining scope in which a 
carbide drill is usable and between the minimum diameter (referred to as 
the symbol .gamma.) of the carbide drill stored in the parameter memory 7 
and the value D.sub.1. If the width/length ratio of the drill machining 
scope is smaller than .beta. and yet the value D.sub.1 is larger than 
.gamma., it is judged that a carbide drill can be used, and the process 
advances to Step S333. Otherwise, it is judged that a high-speed steel 
drill is suitable and the process goes to Step S326. At Step S326, the 
value D.sub.1 is compared with the maximum drill diameter, and if D.sub.1 
is smaller than the maximum drill diameter, the high-speed steel drill 
diameter is set as D.sub.1 (Step S327). Otherwise, the high-speed steel 
drill diameter is set as the maximum drill diameter, and a drill having 
the largest possible diameter and still mountable on the machine is 
selected (Step S328). At Step S329, the width/length ratio of the drill 
machining scope is compared with that (expressed by the symbol .delta.) of 
the machining scope where a center machining is required, and if it is 
judged that the machining scope is too shallow to require the center 
machining, than the process advances to Step S322. Otherwise, it is judged 
that the center machining is necessary and the process goes to Step S330. 
At Step S330, the machining scope is determined based on the shape data of 
a center machining drill stored in the parameter memory 7 in advance (see 
FIG. 20B), and the types and the scope of the machining are stored in the 
temporary memory 4. At Steps S331 and S332, the machining scope is 
determined based on the tool diameter determined at Step S327 or S328 
(FIG. 20B), and types and scope of the machining are stored in the 
temporary memory 4, and the process advances to Step S315 as shown in FIG. 
12A. 
At Step S333, the value D.sub.1 is compared with the maximum drill 
diameter, and if the value D.sub.1 is smaller than the maximum drill 
diameter, the diameter of the carbide drill is set at the value D.sub.1 
(Step S334). Otherwise, it is set at the maximum drill diameter, and an 
arrangement is made to machine by a drill having the largest possible 
diameter and still mountable on the machine (Step S335). At Step S336, the 
machining scope is determined based on the tool diameter which is 
determined at Steps S334 and S335, and the types and scope the machining 
are stored in the temporary memory 4 and the process advances to Step S315 
in FIG. 12A. 
Further, Step S337 in FIG. 12C and the steps thereafter will be described 
with respect to the machining area characteristic to the inner diameter 
machining with a rear end face. 
At Step S337, the quotient (referred to as the width/length ratio) obtained 
by dividing the difference between the maximum value and the minimum value 
in the X direction of the machining area characteristic to the inner 
diameter machining with a rear end face with the difference between the 
maximum value and the minimum value in Z direction thereof is compared 
with the minimum value (expressed by the symbol .epsilon.) of the 
width/length ratio in the machining area necessary to form steps for the 
outer diameter end face which has been stored in the parameter memory 7. 
At Step S338, it is judged whether or not a straight line extending from 
the point X=.alpha. on the machining shape as shown in FIG. 22A in the 
direction of an angle at which the tool for outer diameter end face may be 
insertable crosses the machining shape within the scope where X&gt;.alpha.. 
At the Steps S337 and S338, if the width/length ratio of the machining 
area is greater than .epsilon., and if the line does not crosses the 
machining shape within the scope X&gt;.alpha., it is judged that the 
machining area is shallow but tool for outer diameter end face can be 
inserted to reach the portion where X.gtoreq..alpha. in machining shape, 
and the process goes to Step S342. Otherwise, it is judged that the 
machining with an outer diameter end face tool is not suitable, and the 
process goes to Step S339. At Step S342, the scope of turning on the outer 
diameter end face is determined as shown in FIG. 22B, and the types and 
scope of the machining are stored at the temporary memory 4, and the 
process goes to Step S315 as shown in FIG. 12A. At Step S339, it is judged 
whether or not a blind hole is bored on the blank depending on the 
presence or absence of plural end face elements on the blank shape as 
shown in FIG. 23, and the maximum value in the X direction of the end face 
elements of the work having the minimum value in the Z direction is 
compared with the value .alpha.. If there is the blind hole on the blank 
and if the maximum value in the X direction of the end face element of the 
blank which has the minimum value in the Z direction is larger than the 
value .alpha., it is judged that boring should be conducted only on the 
rear end face of the blank shape for higher efficiency because the time 
needed for cutting feed is shorter, and the process goes to Step S341. 
Otherwise, it is judged that the machining by inner diameter turning 
cannot be achieved only with the boring of the rear end face thereof, and 
the process goes to Step S340 in order to form steps corresponding to the 
machining shape. 
The jump takes place to the subroutine shown in FIGS. 13A and 13B at Step 
S340. For the following description of Steps SP01 and the steps 
thereafter, FIGS. 24A through 27A are referred to. 
At Step SP01, a calculation is made as follows; 
##EQU2## 
At Step SP02, (D.sub.2 +Drill deviation allowance) is compared with the 
maximum drill diameter, and if the former is smaller than the maximum 
drill diameter, the virtual drill diameter is set at the value D.sub.2 
(Step SP03). Otherwise, it is set at the maximum drill diameter, and a 
drill having the largest possible diameter is assumed (Step SP04). At step 
SP05, a high-speed steel drill having an assumed diameter is assumed, and 
whether or not the tip end thereof abuts on the blank at the start of 
machining is judged. If it does, it is judged the drill machining is 
suitable, and the process goes to Step SP07. Otherwise, the drill 
machining is judged unsuitable, and the process goes to Step SP06. 
At Step SP06, the rear end face diameter of the machining shape is compared 
with the maximum end mill diameter. If the former is less than the maximum 
end mill diameter, the roughing end mill diameter is set at the rear end 
face diameter of the machining shape (Step SP08). Otherwise, it is set as 
the maximum end mill diameter, and an arrangement is made so as to machine 
with an end mill having the largest possible diameter and still mountable 
on the machine (Step SP09). At Step SP10, the machining scope is 
determined based on the tool diameter determined at Steps SP08 and SP09 
(see FIG. 24B), and the types and scope of the machining are stored in the 
temporary memory 4, and the process returns to the step immediately after 
Step S340 in FIG. 12C. More particularly, it goes to Step S315 of FIG. 
12A. At Step SP07, a comparison is made between the width/length ratio in 
the drill machining scope and .beta., and between D.sub.2 and .gamma.. If 
the width/length ratio is less than the value .beta. and yet the value 
D.sub.2 is larger than the value .gamma., it is judged that a carbide 
drill could be used, and the process advances to Step SP11. Otherwise, a 
high-speed steel drill is judged suitable and the process goes to Step 
SP18 of FIG. 13B. At Step SP18, (D.sub.2 +drill deviation allowance) is 
compared with the maximum drill diameter, and if the former is less than 
the maximum drill diameter, the high-speed steel drill diameter is set at 
the value D.sub.2 (Step SP19). For flattening the bottom face of the hole 
after boring it with a drill, the roughing end mill diameter is set at the 
rear end face diameter (Step SP20) of the machining shape. By roughing the 
rear end face of the machining shape with a drill and an end mill alone, 
the number of necessary steps is kept minimal. Otherwise, the diameter of 
the high-speed steel drill is set as the maximum drill diameter (Step 
SP21), and the roughing end mill diameter is set at the value obtained by 
(maximum drill diameter-end mill allowance) (Step SP22) so that the 
machining is conducted with a drill having the largest possible diameter 
and with an end mill with a diameter suitable to minimize the distance the 
cutter should travel. At Step SP23, the width/length ratio of the drill 
machining scope is compared with the value .delta., and if the ratio is 
less than the value .delta., it is judged that the machining scope is too 
shallow to require the center machining, and the process goes to Step 
SP27. Otherwise, the center machining is judged necessary, and the process 
advances to Step SP24. At Step SP24, the machining scope is determined 
based on the shape data of the center machining drill which have been 
stored in the parameter memory 7 (see FIG. 25B), and the types and scope 
of the machining are stored in the temporary memory 4. At Step SP25, the 
machining scope is determined based on the tool diameter determined at 
Step SP19 or SP21 (see FIG. 25B), and the types and scope of the machining 
are stored in the temporary memory 4. At Step SP26, the machining scope is 
determined based on the tool diameter determined at Step SP20 or SP22 (see 
FIG. 25B), and the types and scope of the machining are stored in the 
temporary memory 4, and the process returns to the step immediately after 
Step S340 of FIG. 12C. More particularly, the process goes to Step S315 of 
FIG. 12A. At Step SP27, based on the tool diameter determined at Step SP19 
or SP21, the machining scope is determined (FIG. 26B), and the types and 
scope of the machining are stored in the temporary memory 4. At Step SP28, 
based on the tool diameter determined at Step SP20 or SP22, the machining 
scope is determined (see FIG. 26B), and the types and scope of the 
machining are stored in the temporary memory 4, and the process returns to 
the step immediately after Step S340 in FIG. 12C, or Step S315. 
At Step SP11, (D.sub.2 +drill deviation allowance) is compared with the 
maximum drill diameter, and if the former is less than the maximum drill 
diameter, the carbide drill diameter is set at the value D.sub.2 (Step 
SP12), the roughing end mill diameter is set at the rear end face diameter 
of the machining shape (Step SP13) and the rear end face is roughly 
machined with a drill and an end mill alone so as to minimize the number 
of necessary steps. Otherwise, the diameter of the carbide drill is set at 
the maximum drill diameter (Step SP14) while the roughing end mill 
diameter is set at the value obtained by (drill maximum diameter-end mill 
allowance) (Step SP15). The drill machining is conducted by a drill having 
the largest possible diameter and by an end mill having a diameter 
suitable to the distance the cutter should travel. At Step SP16, based on 
the tool diameter determined at Step SP12 or SP14, the machining scope is 
determined (see FIG. 27B), and the types and scope of the machining are 
stored in the temporary memory 4. At Step SP17, based on the tool diameter 
determined at Step SP13 or SP15, the machining scope is determined (see 
FIG. 27B), and the types and scope of the machining are stored in the 
temporary memory 4. The process then returns to the step immediately after 
Step S340 of FIG. 12C, or the Step S315 of FIG. 12A. 
At Step S341 of FIG. 12C, the process jumps to the subroutine shown in 
FIGS. 14A and 14B. A description follows for the process of and after Step 
SW01 referring to FIG. 28A through FIG. 31A. 
At Step SW01, a calculation is made for D.sub.3 =(rear end face diameter of 
the blank shape-drill deviation allowance). At Step SW02, the value 
D.sub.3 is compared with the maximum drill diameter, and if the value 
D.sub.3 is less than the maximum diameter, a virtual drill diameter is set 
at the value D.sub.3 (Step SW03). Otherwise, the virtual drill diameter is 
set at the maximum drill diameter so as to assume a drill having the 
largest possible diameter (Step SW04). At Step SW05, the width/length 
ratio in the drill machining scope by an assumed drill is compared with 
the value .zeta.. If the ratio is less than the value .zeta., it is judged 
that the machining scope is too shallow to require the drill machining, 
and the process advances to Step SW06. Otherwise, the drill machining is 
judged necessary and the process goes to Step SW07. At Step SW06, the 
value D.sub.3 is compared with the maximum diameter of the end mill. If 
the former is less than the maximum end mill diameter, the roughing end 
mill diameter is set at the value D.sub.3 (Step SW08). Otherwise, it is 
set at the maximum end mill diameter, and an arrangement is made to the 
machine with an end mill the largest possible diameter and still mountable 
on the machine (Step SW09). At Step SW10, the machining scope is 
determined based on the tool diameter determined at the Steps SW08 and 
SW09 (FIG. 28B), and the types and scope of the machining are stored in 
the temporary memory 4, and the process returns to a step immediately 
after Step S341 in FIG. 12C, or Step S315 of FIG. 12A. At Step SW07, a 
comparison is made between the width/length ratio of the drill machining 
scope and .beta., and between D.sub.3 and .gamma.. If the ratio is less 
than the value .beta. and yet the value D.sub.3 is larger than the value 
.gamma., a carbide drill is judged usable and the process goes to Step 
SW11. Otherwise, a high-speed steel drill is judged more suitable and the 
process goes to Step SW18 of FIG. 14B. 
At Step SW18, the value D.sub.3 is compared with the maximum drill 
diameter, and if the value D.sub.3 is less than the maximum drill 
diameter, the diameter of the high-speed steel drill is set at the value 
D.sub.3 (Step SW19). For flattening the hole bottom face after having 
bored the same, the roughing end mill diameter is set at (D.sub.3 -end 
mill allowance) (Step SW20) so that the rough machining on the blank shape 
rear end face is conducted only by a drill and an end mill to minimize the 
number of steps. Otherwise, the high-speed steel drill diameter is set as 
the maximum drill diameter (Step SW21), and roughing end mill diameter at 
(maximum drill diameter-end mill allowance) (Step SW22) so that machining 
is conducted with a drill having the largest possible diameter and with a 
roughing end mill having a diameter which could minimize the distance the 
cutter should travel. At Step SW23, the width/length ratio in the drill 
machining scope is compared with the value .delta., and if the ratio is 
less than the value .delta., it is judged that the machining scope is too 
shallow to require the center machining, and the process advances to Step 
SW27. Otherwise, it is judged that the center machining is necessary, and 
the process advances to Step SW24. At the Step SW24, the machining scope 
is determined based on the shape data of the center machining drill stored 
in the parameter memory 7 (FIG. 29B), and the types and scope of the 
machining are stored in the temporary memory 4. At Step SW25, the 
machining scope is determined based on the tool diameter determined at 
Step SW19 or SW21 (FIG. 29B), and the types and scope of the machining are 
stored in the temporary memory 4. At Step SW26, the machining scope is 
determined based on the tool diameter determined at Step SW20 or SW22 
(FIG. 29B), and the types and scope of the machining are stored in the 
temporary memory 4, and the process returns to a step immediately after 
Step S341 of FIG. 12C, or Step S315 of FIG. 12A. 
At Step SW27, the machining scope is determined based on the tool diameter 
determined at Step SW19 or SW21 (FIG. 30B), and the types and scope of the 
machining are stored in the temporary memory 4. At Step SW28, the 
machining scope is determined based on the tool diameter determined at 
Step SW20 or SW22 (FIG. 30B), and the types and scope of the machining are 
stored in the temporary memory 4. The process returns to a step 
immediately after Step S341 of FIG. 12C, or Step S315 of FIG. 12A. 
At Step SW11, the value D.sub.3 is compared with the maximum drill 
diameter, and if the value D.sub.3 is less than the diameter, the carbide 
drill diameter D.sub.3, and the roughing and mill diameter at (D.sub.3 
-end mill allowance) (Step SW13) so that the rough machining on the blank 
shape rear end face could be conducted only with a drill and an end mill 
to minimize the number of steps. Otherwise, the carbide drill diameter is 
set at the maximum drill diameter (Step SW14), and the roughing end mill 
diameter at (maximum end mill diameter-end mill allowance) (Step SW15) so 
that the machining is conducted with a drill having the largest possible 
diameter and with a roughing end mill having a diameter which could 
minimize the distance of cutter feed. At Step SW16, the machining scope is 
determined based on the tool diameter determined at Step SW12 or SW14 
(FIG. 31B) and the types and scope of the machining are stored in the 
temporary memory 4. At Step SW17, the machining scope is determined based 
on the tool diameter determined at Step SW13 or SW15 (FIG. 31B), and the 
types and scope of the machining are stored in the temporary memory 4. The 
process returns to a step immediately after Step S341 of FIG. 12C, or Step 
S315 of FIG. 12A. 
At Step S4 of FIG. 11, the process jumps to a subroutine shown in FIGS. 15A 
and 15B in order to form steps of inner diameter finish machining. 
At Step S401, it is judged whether or not an inner diameter machining area 
exists, and if not, the process returns to the step immediately after Step 
S4. In other words, generating of inner machining steps is completed. 
However, if such area does exist, the process advances to Step S402. A 
machining area in the finish machining means an area defined by the final 
machining shape and the blank shape which is given as the final machining 
shape plus a finish stock. Therefore, the machining shape means the final 
machining shape as shown in FIG. 32. 
At Steps S402 and S403, it is judged whether or not a through hole exists 
in the machining shape, and the minimum diameter of the blank shape 
element is compared with that of the machining shape element, the elements 
forming the machining area. If the through hole exists in the machining 
shape and the minimum diameter of the blank shape element is smaller than 
that of the machining shape element, it is judged that the machining area 
exists in the through hole of the machining shape which needs finishing, 
and the process advances to Step S404. Otherwise, it is judged that the 
machining area is the one characteristic to machining of an inner diameter 
with a rear end face, and the process advances to Step S409 of FIG. 15B. 
At Step S404, the minimum diameter of the machining shape element is 
compared with the value .alpha.. If the diameter is larger than the value 
.alpha., it is judged that the entire area could be finished by inner 
diameter turning, and the step of finishing with inner diameter turning is 
formed (Step S407), and the process advances to Step S408. If the minimum 
diameter of the machining shape element is less than the value .alpha., it 
is judged that the inner diameter machining area is an area characteristic 
to the machining of the inner diameter with the through hole on the blank 
(as exemplified in FIG. 33A), and the process advances to Step S405 in 
order to finish the through hole portion of the machining shape with a 
finishing end mill. At Step S405, the finishing end mill diameter is set 
as the minimum diameter of the machining shape element. At Step S406, the 
machining scope is determined based on the tool diameter determined at 
Step S405, and the types and scope of the machining are stored in the 
temporary memory 4 (FIG. 33B). 
At step S408, the machining area is renewed based on the determined scope 
(FIG. 33C), and the process returns to Step S401. At Step S409, the rear 
end face diameter of the machining shape is compared with the value 
2.alpha., and if the diameter is larger than the value 2.alpha., it is 
judged that the machining shape rear end face could be finished with a 
minor cutting edge of the inner diameter turning tool as shown in FIG. 34, 
and the process advances to Step S410. Otherwise, the process advances to 
Step S411. At Step S410, the machining shape rear end face is set as the 
scope of the machining with the minor cutting edge of the inner diameter 
turning tool, and the types and scope of the machining are stored in the 
temporary memory 4. The process than advances to Step S408 of FIG. 15A. At 
Steps S411 and S412, a comparison is made between the minimum diameter of 
the work shape element and the value .alpha., and between the sum of the 
maximum value and the minimum value of the machining shape rear end face 
in the X direction and the value 2.alpha.. If the minimum diameter of the 
blank shape element is larger than the value .alpha., or if the mean value 
of the maximum and minimum values in the X direction is larger than the 
value .alpha., it is judged that machining could be conducted by an inner 
diameter turning tool as shown in FIGS. 35 and 36, and the process goes to 
Step S407 of FIG. 15A. Otherwise, the process advances to Step S413 
judging that an end mill is more suitable for finishing. 
At Step S413, the rear end face diameter of the machining shape is compared 
with the maximum end mill diameter, and if the rear end face diameter is 
less than the maximum end mill diameter, the finishing end mill diameter 
is set as the rear end face diameter of the machining shape (Step S414). 
Otherwise, the finishing end mill diameter is set as the end mill maximum 
diameter so that the machining could be conducted with an end mill having 
the largest possible diameter and yet mountable on the machine (Step 
S415). At Step S416, the machining scope is determined based on the tool 
diameter determined at Step S414 or S415, and the type and scope of the 
machining are stored in the temporary memory 4. The process goes to Step 
S408 of FIG. 15A. Thus, an example of the machining step generating method 
for an inner diameter machining scope has been described. 
After the above steps, the processor 1 forms numerical control information 
for the inner diameter machining based on the information on the types and 
scope of the machining which have been stored in the temporary memory 4 
and on the machining conditions and tool types which are either extracted 
from the data registered in the parameter memory 7 in advance or 
automatically determined by the processor 1, and stores them in a 
numerical control information memory 8. An operator can conduct any 
desired machining using the numerical control information stored in the 
memory 8. 
In the embodiment, as shown in FIG. 37A, both in the machining shape and 
the blank shape in the inner diameter machining scope, X is monotonically 
increasing as Z increases. This is because, considering the fact that when 
a machining shape of a recessed form exists in a machining area 
characteristic to the inner diameter machining, such a recessed shape is 
generally machined by a grooving or an inner diameter turning, it is 
judged that not much problem would occur even if the steps are determined 
by closing the recessed portions with a virtual lid before generating the 
grooving steps or the inner diameter turning steps, as shown in FIG. 37B. 
As stated in the foregoing, according to the present invention, simply by 
inputting the shapes of the blank and the machining on which the machining 
is to be conducted, it becomes possible to automatically extract a 
machining area characteristic to each machining method in the inner 
diameter machining, and to automatically determine the optimal machining 
method for the area. This can eliminate the necessary to review the 
machining methods before data input and thereby allows beginners without 
expertise and knowledge of complicated inner diameter machining to easily 
determine a method for the inner diameter machining. 
It should be understood that many modifications and adaptations of the 
invention will become apparent to those skilled in the art and it is 
intended to encompass such obvious modifications and changes in the scope 
of the claims appended hereto.