Process Engineering: For Manufacturing

768 Pages·1962·133.39 MB·English

by  G. E. Johnson, Donald F. Eary

Pro c·e E n g i n e e r i n g
55
for Manufacturing
Dona ld F.
T
Mechanical Engineering Laboratories
General Motors Institute
Gerald E. Johnson
Manufacturing Engineering Department
General Motors Institute
;,. C'CN . N 0 • f'J 1\
P R E N T I C E - H A L L , I N C . Englewood Cliffs, N.J.
©-1962 by Inc., Englewood Cliffs, N.J.
All rights reserved. No part of this book ·may be
reproduced, by mimeograph or any other means,
without permission in writing from the publishers.
Library of Congress Catalog Card Number: 62-16313
Current printing (last digit):
11 10 9 8 7 6 5 4 3
Printed in the United States of America
72312-C
J
Preface
Beyond the design stage, one of the most complex problems faced by the
engineer is the development and coordination of plans for manufacturing
products. Using essentially the only information available to him, the
part print, he must create and follow through a properly sequenced series
of operations to transpose materials into useful products. To supplement
his plan, he must select the types of tooling and equipment needed to
carry it out. He must at the same time be concerned with product qual-
ity, quantity, and manufacturing economy. This function is called
engineering and should not be confused with tool design which performs
the mechanical function of designing the tools which are used to carry
out the process engineer's plan.
In our initial statement we used the word coordination. This, of course,
requires getting together all those people directly concerned with the
successful production of the product. We emphasize the need for close
contact with the product designer, for it is from his part print the
process engineer must work. As in a legal contract, there must be a
meeting of the minds. Both the designer and process engineer must work
toward the same objective: To produce a product which is acceptable
to the customer. Errors and omissions on the part print are not
avoidable. Some information needed for manufacturing cannot conveni-
ently be specified on the print. Manufacturing problems discovered early
in the planning may prevent costly engineering and tooling changes later.
Thus, the need for close cooperation between these two functions is
vital. It is significant, then, that in writing those sections of the book
which relate to tolerances, surface quality, and other areas of common
interest, we have endeavored to maintain contact with our associates in
product design. In the end, we have all gained a closer understanding of
each other's problems.
We have combined a substantial number of years of experience as
process engineers or under related titles with such organizations as
Chevrolet and Buick Motor Divisions, North American Aviation, Howard
Manufacturing Corporation, and others, with our years of teaching this
subject at General Motors Institute in developing this book. Many tech-
niques and principles were developed or acquired over the years and are
included. Prior to this book, our processing course was taught with the
iii
iv Preface
aid of a manual which was the joint effort of both authors and our
colleagues. As the result of the use of this manual, which was primarily
a workbook, it became increasingly clear that a complete book on the
subject would have many potential benefits for our students and those
at other schools. In addition, it would aid substantially those already
out in industry.
In content, this book provides all the essential background informa-
tion for college level teaching as well as for processing in actual plant
operation. The order of chapters follows what has been found to be the
most logical approach for teaching. Some of the concepts are entirely
new whereas others are new applications of basic sciences. The prin-
ciples presented will aid the process engineer at a time when close
tolerances, new materials, high production, and economic competition
are prevalent.
The encouragement and support given for this project by the personnel
of General Motors Institute is appreciated. Acknowledgment is given
to Arthur King, Buick Motor Division for his assistance in preparing the
materials concerning paperwork.
Many manufacturers of tooling and equipment have contributed illus-
trations and data for the text. Several manufacturing concerns have pro-
vided illustrations of actual operations. Our acknowledgments of their
important assistance is generally recognized by courtesy lines.
Over the past two decades certain basic concepts of process planning
at General Motors Institute have been developed both in special plant
instruction and in our engineering courses. Some of these concepts were
the outgrowth of the plant instruction conducted by Lawrence C. Lander,
Jr. in such plants as Allison, Detroit Transmission, and Detroit Diesel
Engine, all of which are divisions of General Motors Corporation. For
example, such concepts and principles as the location system and the
symbols used came out of group discussions with those responsible for
process ·p lanning in their respective plants. It is impossible to identify
and to give credit to those who participated. We wish, however, to ac-
knowledge the assistance of all those men who were involved. Our
acknowledgments would not be complete without recognizing our depart-
mental secretary, Mrs. Barbara Mize, who typed the many letters request-
ing permission to use illustrations shown in this text.
Gerald E. Johnson
Donald F. Eary
Contents
1 The Process Engineering Function 1
v
General Manufacturing Processes, 2. Organization Chart, 4. Product
Engineering, 5. Process Engineering, 1. Glossary of Terms, 10. Com-
munications, 11.
2 Preliminary Part Print 14
Problems Encountered in Reading and Interpreting Part Prints, 15. Y
Establishing the General Characteristics of the Workpiece, 15. Auxiliary
Methods for Visualizing the Part from the Print, 22. Determining the
Pf'incipal Process, 23. Alternate Processes, 24. Functional Surfaces of
the Workpiece, 25. Determining Areas Used for Processing, 26. Speci-
fications, 28. Nature of the Work to be Performed, 29. Finishing and
Identifying Operations, 32. Re[ating the Part to Assembly, 33.
3 Dimensional Analysis 42
Types of Dimensions, 43. Measuring the Geometry of Form, 44. Sur-
face Quality and Its Measurement, 56. Baselines, 70. Direction of
Specific Dimensions, 72. The Skeleton Part, 72.
v 4
Tolerance Analysis 79
Causes of Workpiece Variation, 80. Terms Used in Determining Work-
piece Dimensions, 80. How Limits are ExrJressed, 81. How Tolerances
are Expressed, 81. The Problem of Selective Assembly, 83. Tolerance
Stacks, 84. Cost of Arbitrary Tolerance Selection, 90.
Tolerance Charts
Purpose and Utilization of Tolerance Charts, 98. Definitions and Sym-
bols, 99. Rule for Adding and Subtracting Dimensions, 100. Estab-
lishing a Tentative Operation Sequence, 101. Layout of the Tolerance
Chart, 103. Converting Tolerances, 105. Figuring Stock Removal, 106.
Developing the Tolerance Chart, 107. Balancing the Tolerance Chart,
117.
v
vi Contents
Workpiece Control 120
,J
Equilibrium Theories, 123. Concept of Location, 125. Geometric Con-
trol, 133. Dimensional Control, 151. Mechanical Control, 166. Al-
ternate Location Theory, 183. Gaging, 196.
V'7
Classifying Operations 198
/
Basic Process Operations, 199. Principal Process Operations, 203.
Major Operations, 209. Auxiliary Process Operations, 217. Support-
ing Operations, 217.
8 Selecting and Planning the Process of Manufacture 222
Function, Economy and Appearance, 222. Fundamental Rules for the
Manufacturing Process, 225. The Engineering Approach, 225. Basic
Design of the Product, 227. Influence of Process Engineering on
Product Design, 228. Rechecking Specifications, 231. How Materials
Selected Affect Process Cost, 231. Using Materials More Economically,
232. The Material Cost Balance Sheet, 244. How the Process Can
Affect Materials Cost, 246. Eliminating Operations, 249. Combined
Operations, 250. Advantages of Combined Operations, 256. Disad-
vantages of Combined Ope-rations, 259. Selecting the Proper Tooling,
265. Availability of Equipment, 267. Effects of Ope-ration Speed on
Performance and Economy, 268. The Make or Buy Decision, 274.
Terminating the Process, 277.
/ 9
Determining the Manufacturing Sequence 280
Operation Classifications and the Manufacturing Sequence, 280. De-
termining the Ma;or Process Sequence, 282. What Dictates Operation
Sequence, 284. The Purpose of the Major Process Seque-nce, 286. An
Example of a Machining Sequence, 287. Combining Operations, 295.
\1"'1 0 The Question of Mechanization 297
Studying Manufacturing Costs, 298. What is the Proper Cost Base,
298. The Problem of Incomplete Machine Utilization, 299. The In-
ventory Alternative, 302. The Scrap Inventory Proble-m, 302. Capi-
tal Costs Are Inflexible, 304. The Start-up Proble-m, 304. Com-
parison by Break-even Principle, 306.
11 1
Selection of Equipment 309
Relationship Between Process Selection and Machine Selection, 310.
Knowledge Required to Select Equipment, 310. Sources of Informa-
tion for the "Process Engineer, 311. The Nature of the Selection Prob-
lem, 312. Special-Purpose Versus General-Purpose Equipment, 315.
Adapting General-Purpose Machines to Special Purpose Work, 322.
Contents vii
Basic Factors in Machine Selection, 325. Cost Factors, 325. Design
Factors, 326. Approaches to Selection Among Alternatives, 329. Cost
Analysis of Proposals, 330. Comparative Cost Analysis, 338. Com-
parison by Break-even Principle, 340. Acquiring New Equipment by
Leasing, 340.
12 Standard Equipment 346
Turning, 347. Drilling, 361. Milling, 373. Shaping, 389. Broach-
ing, 399. Grinding, 413. Cutoff, 435. Pressworking, 446. Pressure
Molding, 461. Forming, 474. Assembly, 493. Heating, 512. Clean-
ing and Surface Treatment, 525. Classification Systems, 551.
13 Special Equipment 558
Workpiece H andZ.ing Systems, 559. Integrated Equipment, 579. Unit-
ized Equipment, 586. Controls, 602. Speci.al Processes Equipment,
603. Rules for Automation, 605.
\II 14 Classification of Tooling 607
Sources of Tooling, 608. Tooling, 613. Tool<>, 615. Tool Holders,
617. Workpiece Holders, 652. Molds, 676. Patterns, 681. Core
Boxes, 683. Dies, 686. Templates, 690. Gages, 690. Miscellaneous
Supplies, 705.
15 The Process Picture 707
\/"
Process Symbols, 707. Process Picture Sheet, 110. Processing Dimen-
sions, 713. Selection of Views, 714.
16 The Operation Routing 720
Routing Uses, 722. Routing Description, 728 .
./17 Orders and Requests 736
Engineering Release, 737. Engine.ering Change Notice, 739. Stand-
ards, 741. Tool Orders, 742. Tool Revision Orders, 745. Request
for Purchase Requisition, 7 46. Request for Engineering Change, 7 48.
Machine Specifications, 751. Miscellaneous Paperwork, 753.
Index 755

1
chapter
The Process Engineering
Function
Before the detailed study of processing can be understood, the general
position of the process engineer in the over-all plant organization should
be described. Also, some of the more important terminology used in proc-
essing needs to be defined. The function and responsibilities of the process
engineer must be presented so that the meaning and need for the follow-
ing chapters are evident.
The term process should be defined first. A process is simply a method
by which products can be manufactured from raw materials. This text
deals primarily with processes as used in the hardware industry. The
hardware industry includes manufacturers of metal products. The term
hardware was evidently developed when metal products first began to
replace wood, paper, leather, or earthen products on a volume basis. The
term hardware indicates a ware having good strength, hardness, and
wearing properties. Metal products have these properties to a higher
degree than other products. Hardware originally was limited to locks,
handles, cooking utensils, guns, tools, and other small parts. The items
found in the common hardware store illustrate these items. At the present
1
2 The Process Engineering Function
time, the hardware industry now includes the manufacture of other metal
products such as appliances, automobiles, electronic devices, aircraft, and
other larger products. Many may consider plastic and rubber products as
now a part of the hardware indust ry.
A process could also be described as a method for shaping raw material
into usuable product forms. The term process, as used here, applies to
the shaping of metal, plastic, or rubber in the raw material states. The
principles presented here are not applicable to other industries, such as
those for manufacturing foodstuffs, textiles, chemicals, and medicines.
This text is not intended for use in relation to the industry which makes
raw materials. In other words, the plants which produce sheet metal, bar
stock, tubing, pigs, metal powders, or plastic powders are not considered
manufacturing plants. Plants which cast, forge, or extrude raw materials
into rough product fmms may find limited use of the information
presented.
General Manufacturing Processes
The manufacture of all hardware products can be separated into four
general categories as follows:
Casting and Molding
Cutting
Forming
Assembly
Raw materials in the molten or powdered states are either cast or
molded into the shapes desired. Liquid metals are cast in sand, plaster,
or metal molds. Powdered or granular plastics are heated to the liquid
state and placed under pressure in metal molds. Metal powders can be
squeezed under high pressures to mold parts. Casting and molding are
then used to create shapes by the use of cavities having the contours
desired.
Materials in the solid state can be shaped by cutting away small chips
with a very hard and sharp tool. By removing only small chips, the forces
required are small. Bar stock, extrusions, castings, forgings, and other
forms can be fw·ther shaped by the cutting process. Material cutting can
therefore be considered a finishing process in most cases.
Solid materials can also be shaped by actually squeezing or stretching
them under very high forces. Material forming then is used to create
product shapes from bar stock, sheet materials, tubing, and similar raw
materials. Often, the raw material is heated to reduce the forces required
for shaping. Material forming is often l'eferred to as a chipless manu-
facturing process.
Many final products are too complex to be made in one piece. In other