U.S. Department

of Commerce

National Bureau

of Standards

Reference

NBS

Publi * cations

Automation Technology Program

A11101 730014

NBSIR 80-2073

Guidelines for Exchangeable Apt Data Packages ®(''>EAU Of

Final Report

Bradford M. Smith

June 1980

Prepared for the

Air Force Logistics Command

Sacramento Air Logistics Center

PRAM Office

-QC

100

. U56

80-2073

1980

national bureau

OF STANDARDS

LIBRARY

SEP 1 9 1980

Automation Technology Program

NBSIR 80-2073

GUIDELINES FOR EXCHANGEABLE APT DATA PACKAGES

Bradford M. Smith

June 1980

Final Report

Prepared for the

Air Force Logistics Command

Sacramento Air Logistics Center

PRAM Office

U.S. DEPARTMENT OF COMMERCE, Philip M. Klutznick, Secretary

Luther H. Hodges, Jr., Deputy Secretary

Jordan J. Baruch, Assistant Secretary for Productivity. Technology, and Innovation

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director

TABLE OF CONTENTS

EXECUTIVE SUMMARY ----------- 3

BACKGROUND ______________ 5 PROBLEM ---------------- 6

APT LANGUAGE SELECTION --------- 7

SOFTWARE MODIFICATION _________ 9

BENEFITS 10

IMPLEMENTATION PRIORITIES _______ 12

CONCLUSION --------------- 13

APPENDICES

STEERING GROUP ---------- 15

PROJECT SCHEDULE 17

- 1 -

i

EXECUTIVE SUMMARY

Users of numerical control (NC) machines could save considerable

time and money if it were possible to quickly and easily exchange

part program data among different NC machines. Historically the

Air Force Logistics Command (AFLC) has used a program called APT

to help prepare control data for its large inventory of NC equipment. Software postprocessors link the APT system with each individual machine tool. However, because of an early lack of

standardization in the APT language used to control machining

functions, a programmer must write slightly different APT part

programs to produce the same part on different machine tools.

The National Bureau

five Air Logistic

method of APT progr

this exchange at

drilling type machi

to machine tools or

general processor o other modifications

of Standa

s Centers

amming and

the APT

ne tools.

controlle

ther than

are local

rds working in cooperation with the

(ALC) has developed and tested a postprocessor design which permits

source language level for millingThe technique involves no changes

r hardware and no changes to the APT

simple vocabulary additions. All

ized in the postprocessors.

Sponsored by the Producibility, Reliability, Attainability and

Maintenance Office at Sacramento ALC under Military Interdepartmental Purchase Request FD 2040 78 60013, the project developed a comprehensive plan for modifying AFLC software. The Project

Manager at Sacramento was Mr. Cleon Binyon, and software modifications at Ogden were under the direction of Mr. Malcolm Allen.

The approach was successfully demonstrated in production at Sacramento by processing a single APT data package on three different milling-drilling type machine tools.

Kearney and Trecker three spindle profiler - 3 axis

Giddings and Lewis vertical machining center - 3 axis

Pratt and Whitney horizontal machining center - 4 axis

The APT part program was processed for each machine by changing

only the MACHIN selection statement and the part ORIGIN statement. This exchangeability of part manufacturing data was made

possible by modifying the postprocessor software to process each

APT statement in the same manner for all machine tools. Thus the

original intent of the part programmer was satisfied on all three

machine tools regardless of whether the function was performed

automatically by the machine or was simulated by other means such

as by the postprocessor or by requests to the machine operator.

Project results are contained in four documents:

Guidelines for Exchangeable APT Data Packages

AFLC APT Part Programmer's Manual

AFLC APT Postprocessor Specifications

AFLC Postprocessor Software Guide

3
The first report details the approach taken and the benefits

measured. The Part Programmer's Manual documents the functions

to be performed at the machine tool for each APT language statement. This one manual will serve the needs of all millingdrilling type machine tools in AFLC whereas before, every machine

required its own different programming manual. The Postprocessor

Specifications are to be used in the procurement of new postprocessors along with future machine tools. Initially, it is expected that the requested software will result in additional expense until vendors recognize the logic of the approach taken.

Finally, the Software Guide was developed to assist Ogden ALC

personnel in modifying some 30 existing postprocessors to implement the approach across all of AFLC's production facilities.

This figure includes 21 existing postprocessors plus 9 anticipated near term procurements.

A Steering Group of numerical control manufacturing experts from

each ALC provided guidance and direction for the project to insure that results would reflect a generic need and not just that

of Sacramento. This group has developed a prioritized plan for

full implementation across 31 machine tools at the five AFLC facilities. Furthermore, the group has projected an 23 % increase

in numerical control manufacturing efficiency upon complete implementation. Elements of these savings are:

More Efficient Programming

Less Reprogramming of Workload

Reduced Computer Charges

Simplified Training

Better Shop Scheduling

- 8 % - 6 % - 5 % - 2 % - 2 %
BACKGROUND

The typical user of NC machine tools has high praise for the increased productivity and the better control over the manufacturing process that NC has brought him. But a careful look at shop

operations will often identify problems that are all too familiar

to veterans in this field; idle machines waiting for tapes, work

stacked up on machines which are down for maintenance, and part

programmers wrestling with the details of reprogramming some jobs

for other machines. These nonproductive operations highlight

several technical problems which must be solved before users can

achieve maximum benefits from their NC equipment.

One problem very basic to NC is the lack of interchangeability of

part manufacturing data among different machines. Productive

utilization of a group of machine tools is enhanced by the abili-^

ty to interchange jobs among the machines, and to be able to do

this with minimum costs and time delays. For years, NC users

have needed to be able to quickly and easily exchange part

manufacturing data among their NC machines. But the proliferation of different controls, optional features and tape coding

schemes have precluded much hope of this unless a shop was able

to standardize on a single NC controller or could afford to re~

trofit all their machines to the newer CNC controls.

Recognizing this problem, the National Bureau of Standards (NBS)

proposed to the Air Force Logistics Command (AFLC) a joint effort

to develop, test and demonstrate a method which would allow part

manufacturing data to be developed in a high level language and

in a common format for all mi 11 i ng^d r i 11 i ng type NC machines. A

Steering Group of ALC experts, listed in Appendix 1, was esta^

blished to guide this effort. The project involved the defini^*

tion of a common format by the Steering Group and NBS, the modify

ication of production software by NBS and Ogden ALC, and the

machining demonstration at Sacramento ALC. A detailed schedule

for the project is given in Appendix 2.

5
PROBLEM

While sharing tapes among NC machines has seldom been possible,

the sharing of part data may be made practical through the use of

higher level programming languages. APT is one of these higher

level languages and is used by many NC shops.

One objective in the development of the APT language processor

was to lessen the computational burden on the part programmer.

This has been accomplished successfully. However, another design

intent was to be able to postprocess the same part program for

any machine simply by changing the MACHIN statement. Unfortunately, present APT systems fall short of doing this because

various machine postprocessors require slight differences in

their input language. These language inconsistencies force a part programmer to choose which machine will be used before he

starts to program. Thus, present APT part programs cannot be

reused without modification for any machine other than the one

originally chosen for machining the part.

One problem involves language syntax. A programmer is forced to

use slightly different APT statements to achieve the same result

on different machine tools. For instance, the statements below

invoke the same spindle speed and tapping cycle on two different

machines. Yet if they are interchanged, error diagnostics are

produced instead of parts.

SPINDL/1 00 0 , CLW , HIGH CYCLE/TAP , z , f , IPM

SPINDL/RANGE, HIGH, RPM, 1000 CYCLE/TAP , RAPTO , n , FEDTO , Z , I PM ,

A second problem which causes trouble in exchanging APT data involves part programming statements which call for features not

available on the other machine tool - features such as an automatic tool changer. These part programming commands, when

postprocessed for the other machine, will either produce error

diagnostics or worse yet, will be ignored without comment, leaving the programmer to believe that the tape is good. Some of the

commands which fall into this category are:

LOAD/TOOL ROTATE/TABLE

AIR/ON CUTCOM/ON

A third problem involves semantics. There are some language

statements which have different meanings to different machines.

For instance, the statement GOHOME does not cause the same sequence of actions on all machines. These various inconsistencies

in the APT postprocessor language and in the way that language is

interpreted by postprocessors complicate the task of running a part program on any machine other than the one originally selected for the job. However, one can see that the problems are not

i ns urmoun table

-6
APT LANGUAGE SELECTION

A major requirement for achieving the objective of rapid and simple exchange of APT part programs among different NC machines is

a common language for the machine dependent APT statements. This

choice of language was heavily influenced by the American National Standards Institute (ANSI) X 3*37 - 1980, the latest U.S.

Standard for the APT Language. This revision addresses much of

the postprocessor language needed for the project and was adopted

as a starting point. Additional vocabulary was developed for

those areas of the ANSI APT where no language had yet been specified. The exact choice of vocabulary was discussed with the lead

part programmers throughout the Air Logistics Centers and with

other personnel in the Army, Navy, Air Force, other government

activities, and several private industrial firms. The exact

choice of language is documented in the AFLC APT Part

Programmer's Manual.

But having a language set is only part of the solution. It

specifies only the input to the postprocessor. The second requirement for part program portability is that all postprocessors

execute each APT command in the same way. One must determine the

desired functional output of each language statement - the sequence of motions at the machine tool. Our project analyzed 32

postprocessor vocabulary statements shown in Table 1 to define

the desired actions. These are also documented in the Part

Programmer's Manual. Normally, there is a different part

programmer's manual for each NC machine tool. However, using the

methodology developed by this project, only one such manual will

be required for all NC machines of the milling-drilling type.

Table 1 - APT Postprocessor Major Words

AIR INSERT RETRCT

BREAK LEADER REWIND

CLAMP LINTOL ROTATE

CLRSRF LOAD SELECT

COOLNT MCHTOL SEQNO

CUTCOM OPSKIP SET

CYCLE OPSTOP SPINDL

DELAY ORIGIN STOP

END PIVOTZ TMARK

FEDRAT PPRINT TRANS

GOHOME RAPID

- 7 -
Given the input language and the desired functional output we evolved a philosophy for modifying and/or constructing postprocessors such that part programs can be interchanged. It has four

major elements

All postprocessors must accept the same statement syntax.

A postprocessor must recognize all statements and flag those

which cannot be processed.

The meaning of each APT statement must be the same for all

postprocessors

.

The postprocessor must always ensure that the desired function is accomplished, either directly or by simulation.

A primary guideline of this philosophy is to satisfy the intent

of the part programmer at all times. Where this intent cannot be

met automatically by the chosen controller and machine tool, the

postprocessor must simulate the action desired. Sometimes this

requires the assistance of the machine tool operator. A few examples will serve to illustrate.

Task Statement

Load cutting tool LOAD/TOOL, 21, LENGTH, 3-75

21 into spindle

Ordinarily this statement is used to control an automatic tool

changer in a sequence that is quite familiar. With the new approach to exchanging part programs, this same LOAD/TOOL statement

is used whenever the programmer desires to change a tool regardless of whether the machine tool is equipped with a tool changer

or not. When the statement is processed for a machine without

tool change capability, the following actions are generated; move

the machine to the manual tool change position, stop the spindle,

lock the spindle if necessary, and issue a comment to the operator with instructions to load the tool. In this way the desires

of the part programmer can be met by all NC machines.

Task Statement

Provide a dwell DELAY/4

of four seconds

This statement usually results in tape codes that cause the NC

controller to halt feedrate motion for the preset time. In cases

where this controller feature is not present, it may be possible

for the postprocessor to calculate and output a number of leader

characters to accomplish the desired dwell time. Otherwise a warning diagnostic would normally be issued to advise the part

programmer that the intent cannot be satisfied on the selected

machine and controller.

- 8 -
SOFTWARE MODIFICATION

The key to implementing this strategy is the modification of APT

postprocessor software to process each APT statement in the same

manner for all machine tools. To demonstrate this approach at

Sacramento ALC, three postprocessors were modified by Ogden for

the following machines:

Kearney and Trecker three spindle profiler - 3 axis

Giddings and Lewis vertical machining center - 3 axis

Pratt and Whitney horizontal machining center - 4 axis

These software changes are documented in a companion report, the

AFLC Postprocessor Software Guide. It must be recognized that a great diversity exists among postprocessors. Each generally has

been developed by different sources and incorporates different

software processing techniques. AFLC currently has 39 postprocessors, 28 of which represent substantially different codes.

The normal procedure for modifying any one of these is for a computer programmer to first learn the detailed operation and structure before devising specialized code changes to implement the

new capability. While this approach works, the trouble for AFLC

is that changing the second or third postprocessor is just as much work as the first. The Software Guide details another approach which although far from optimum does alleviate some of the

repetetive work and appears to be a more economical method for

modifying those postprocessors needed by AFLC.

The process is accomplished in a stepwise manner with tests performed after each modification so that the production integrity

of the postprocessor is maintained. A total of ten test part

programs were developed for this purpose. Neither the Guide nor

this project is intended to imply a standardization of the FORTRAN code in all postprocessors. Quite the opposite, only the

input data to a postprocessor has been standardized. The CL file

represents the standardized coding, format and functional intent

of the original APT part program. Thus, the syntax and semantics

of the APT postprocessor language plus the CL file are the only

things standardized. This software guide serves only as a reference to document the modifications which were made to three inhouse postprocessors. Other implementors of this concept will

probably choose an entirely different modification scheme in

their FORTRAN code. How they do it is immaterial, for the only

important point is that the postprocessor - controller - machine

combination function according to the specifications in the AFLC

Part Programmer's Manual. If this is done consistently and is

done well, users will have the portability they desire and

management will see more productivity from their NC investment.

- 9 -
BENEFITS

Full implementation of this methodology will produce savings in

terms of labor content, leadtime, and cost of NC manufacturing

both on new work as well as on maintenance and repair work. At a meeting of the AFLC Steering Group in Sacramento these savings

were calculated to be a 23 % increase in numerical control

manufacturing productivity. Elements of these savings are:

MORE EFFICIENT PROGRAMMING - The part programmer's task is

simplified since there is no need to remember the idiocyncracies of each machine tool's APT language. There will be

fewer errors in coding, leading to fewer computer runs for

each part. There will be less time spent referring to part

programming manuals. The Steering Group estimated that labor savings are 8 % of annual workload.

LESS REPROGRAMMING OF WORKLOAD - Since a part program can be

processed quickly and easily for any available machine tool,

costly reprogramming of parts is eliminated. Table 2 shows

for the five ALC's in calendar 1979 that an average of 6 %

of a part programmer's time was spent in reprogramming parts

because the machine for which the program was originally

written was not available to do the job.

REDUCED COMPUTER CHARGES - Indirect savings are expected in

areas such as cost of computer time and materials since

fewer computer runs are anticipated for each completed job.

Overhead costs such as these are difficult to quantize but

data from Sacramento indicates an average of seven computer

runs per job. Conservatively, one run per job could be

saved via this approach leading to a 5 % annual savings.

SIMPLIFIED TRAINING - New personnel can be more completely

trained in a classroom environment rather than on-the-job

resulting in a 2 % savings.

BETTER SHOP SCHEDULING - Workload can be more efficiently

scheduled, and priority work can be accomplished without major disruption of ongoing projects. The savings from having

to tear down machines in the middle of a job is estimated by

Sacramento at 2 %.
Table 2 Benefits from Less Reprogramming

Total Hours per Man-Year

Less leave, holidays

Less non programming tasks

Training, tooling

Drafting, designing

Net Programming Time

Per Man-Year

2096

337

668

*********

1091 hours

Air Hourly Average Total

Logistics Reprogramming Number of Hours of

Center Workload Programmers Workload

Per Cent

Reprogramming **********************************************************************

Ogden

Oklahoma City

San Antonio

Warner Robins

Sacramento

368

452

294

566

281

4

8

7

6.5

6

4364

8728

7637

709 1

6546

8.4

5.2

3.8

8 .

4.3 **********************************************************************

Average % Reprogramming 6 .
IMPLEMENTATION PRIORITIES

This project has developed the basic framework for an enhanced NC

software system that holds significant benefits for both users

and management. The Steering Group has recommended full implementation of the concept across AFLC. A total of 31 machines are

involved as shown below. The machines are listed in priority

order for each of the five shops and do not include those slated

for near term replacement.

SAN ANTONIO

12

3

4

5

12

3

4

5

6

7

12

3

4

Sundstrand Series 80 new

Sundstrand OM 3 BXOM35

K+T Moduline CONCRD, 044012

B+S Machining Center CINCY,

2

Hydrotel BENDIX ,2566

OKLAHOMA CITY

Sundstrand OM 1 BCSPOS , 12

Sundstrand OM 1 BCSPOS , 20

XLO Vicker XLONCS , 108

Burgmaster VTC BURG , 160

Hillyer AB AB4500 , 1

0

M00G MOOG ,

2

Cincinnati CIMTRL ,22

7 more machines anticipated

WARNER ROBINS

C I MX

CIMX

K+T Moduline

Hydrotel

CINAC9 , 076

new

SUNTRN , 103005

CINAC7 ,083

OGDEN

12

NCVPTH ,

2

CINAC1 ,125100

12

3

45

6

SACRAMENTO

Brown & Sharpe

Gorton

G & L Die Mill

Pratt & Whitney Cub

Cincy Hydrotel

XLO 4 axis

BROWNS ,

1

BR 3 1 00

DIMILL , 1 AB3300, 1 8

CINAC6 , 004

XL0AB5

- 12 -
CONCLUSION

Portability of APT part program data among functionally similar

NC machine tools is a prime concern for users of this automation

equipment. Existing standards for the postprocessor language do

much toward simplifying the exchange of data but are not adequate

to ensure total portability. The guidelines developed by this

project enable portability through a consistent specification of

machining functions that result from the use of each APT language

statement. Whether these functions are carried out by the postprocessor, the NC controller, the machine tool or the operator is

immaterial. The essential point is that they be carried out consistently for all machines. The postprocessor - controller

machine tool - operator combination must at all times satisfy the

intent of the part programmer. In this way exchangeability of

APT data packages becomes possible.

This project has addressed only the milling and drilling type

machine tools, but the approach and benefits are clear for subsequent application to lathe operations. Furthermore, the approach

is equally applicable to systems where the postprocessor is

resident on the mainframe computer or to systems where it is imbedded in the NC control unit. The technique has shown significant benefits in actual production. Implementation involves no

changes to machine tools or controller hardware and no changes to

the APT general processor other than simple vocabulary additions.

The key lies in the postprocessor software. It is the mechanism

which must compensate for the many differences in electronic controller features and machine tool options.

APPENDIX 1 STEERING GROUP

Mr. Cleon Binyon

Sacramento - ALC-MANEB

McClellan AFB . Calif. 95652

Mr. Malcolm Allen

Ogden - ALC-ACDBB

Hill Air Force Base, Utah 84406

Mr. Marion Eichman

Oklahoma - ALC-MATTN

Tinker Air Force Base, Oklahoma 73145

Mr. George Sheffield

Ogden - ALC-MANER

Hill Air Force Base, Utah 84406

Mr. Alex Tschirhart

San Antonio - ALC-MANEN

Kelley Air Force Base, Texas 78241

Mr. Jerry Elmers AFLC-MAXF

Air Force Logistics Command

Wright Patterson Air Force Base, Ohio 45433

Mr. James Ward

Sacramento - ALC-MANEB

McClellan AFB, Calif. 95652

Mr. Tommy Warren

Warner Robins - ALC-MANEF

Robins Air Force Base, Georgia 31093

- 15 -
' • '
APPENDIX 2

PROJECT SCHEDULE

Headquarters Air Force Logistics Command ( AFLC ) Code MAXF

will create a steering group to meet with the National

Bureau of Standards at Ogden Air Logistics Center ( ALC ) to

identify project personnel and the NC production equipment

to be involved. ( April 78 ) Sacramento ALC Code MA will be Office of Primary Responsibility (OPR) will furnish programming manuals on the NC

equipment selected. ( May 78 )

A committee, as designated by the steering group, will

analyze the present AFLC software and the APT Postprocessor

Language currently in use. ( June 78 ) The combined committee will investigate the new ANSI standard for applicability and will select final language

features to be used. ( June 78 ) NBS will document the language chosen in a Part Programmer's

Manual . ( July 78 ) NBS will specify the functional machine response for each

language command and will differentiate those actions which

can be performed automatically from those which must be

simulated by the postprocessor. ( November 78 ) NBS will furnish to Ogden ACD the written documentation for

implementation of this approach on the NC machines selected.

( November 79 ) Ogden Code ACD will modify postprocessors for the selected

machines. ( December 79 ) Sacramento ALC will host an end of project demonstration

running at least three test programs, using the materials

developed. ( January 80 ) NBS will furnish additional written documentation to enable

computer programmers to implement the standard on all

machine centers in the Air Logistics Command. (February 80)

NBS will furnish Headquarters AFLC Code MAXF written quarterly progress reports and a final written report on all

products developed in this study. ( February 80 )

- 17 -
NBS-114A (REV. 8-78)

U.S. DEPT. OF COMM. 2. Gov't Accession No, BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBSIR 80-2073

3. Reciptent' s Accession No.

4. TITLE AND SUBTITLE

Air Force Logistics Command

APT Postprocessor Standardization Project

Final Report

5. Publication Date June 1980

Performing Organization Code

7. AUTHOR(S)

Mr. Bradford M. Smith

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

It. Project/Task/Work Unit No.

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, state, zip)

Air Force Logistics Center

McClellan Air Force Base

California 95652

13. Type of Report & Period Covered Final

?;>5

'

15. supplementary NOTES Three other reports complete the documentation on this project

:

APT Part Programmers Manual, APT Postprocessor Specifications, and The Postprocessor

Software Guide

I | Document describes a computer program; SF-185, FIPS Software Summary, is attached.

IS. ABSTRACT (A 200-word or leas factual summary of moat significant information. If document includes a significant bibliography or

literature survey, mention it here.) A method of APT programming and postprocessor design is described which permits

more efficient data preparation for numerical control (NC) machine tools and then

allows this data to be quickly and easily exchanged among different NC machines.

A rigorous specification is made of the APT postprocessor language based upon new

ANSI standards for APT and is coupled with a comprehensive definition of the

machining functions which should result from the use of each APT language statement,

Individual postprocessors are modified to process each statement in the same manner,

Thus, the original intent of the part programmer is always satisfied. A 23%

increase in NC manufacturing efficiency is projected. The approach is demonstrated

in production by processing a single APT data package on three different millingdrilling type machine tools. This Final Report details the approach taken and the

benefits measured.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name

separated by semicolons)

APT; Automation; Computer aided manufacturing; NC machining; NC programming;

Numerical Control; Part programming

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