Unit 34
MASS PRODUCTION
Science and invention, coupled with industrial
know-how, have made America a great nation. We
have developed systems of mass production that
provide us with a tremendous range of products that
make life easier and more enjoyable. Items that were
considered luxuries just a generation ago, are now
available to everyone.
Although wood products are seldom produced at
the high volume reached by such metal products
as automobiles and refrigerators, the same general
procedures, methods, and considerations must be
applied to the manufacturing process.
All manufacturing plants, whether they are large
or small, build a few custom products or mass
produce items for wide distribution, include such
departments and divisions as business and finance,
product selection, design and engineering, produc­
tion, inspection, storing, packaging, and shipping.
In the mass production plant there are additional
elements that receive special attention:
1. PRODUCT SIMPLIFICATION. Designing or
redesigning the product so that it is easy to
produce, yet still includes features that are at­
tractive and functional.
2. STANDARDIZATION OF PARTS. Given parts
will all be the same. They are interchangeable
in an assembly. Worn or damaged parts can be
easily replaced after the product is placed in
service, Fig. 34-1.
3. SPECIAL MACHINES AND TOOLS. This in­
cludes jigs, fixtures, and special setups that can
be applied to standard equipment so the equip­
ment will perform a given operation with speed
and accuracy, Fig. 34-2.
4. ORGANIZATION OF MACHINES, MATERIALS,
AND WORKERS. Involves careful analysis of
work, so that jobs can be broken down into
simple operations and arranged in proper
sequence. Controlled movement of materials
and assemblies from one station to the next.
Synchronization of all operations, so that the
right things are at the right place at the right
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Fig. 34-1 . Standardized kitchen cabinets have interchangeable
parts. Drawers are installed before units are given a final
inspection, then they are individually boxed for shipment.
(Bertch Wood Specialties)
Fig. 34-2. A specialized setup for cutting several fine grooves
in a panel at once. Each piece cut in this manner will be exactly
the same. (Campbellrhea Mfg., Inc.)
Modern Woodworking
time. Assignment and coordination of workers
and jobs.
Already you may have experienced in a small way
the efficiency that can grow out of mass produc­
tion. Possibly you have constructed a pair of
matching end tables or similar project and found that
you were able to produce them in less than double
the time necessary to produce one.
Production time for each item can be further
reduced as larger quantities are produced, especially
if the work is carefully organized and attention is
given to the development of special devices. For
example, Fig. 34-3 compares several methods of
cutting a dowel to a specified length. The hand
sawing jig greatly improves the accuracy and quality
of the work, which is very important for producing
interchangeable parts. The sawing fixture mounted
on the table saw provides the same accuracy, plus
a higher production rate.
You may want to design and mass produce a
small item working by yourself. If you carefully
planned and organized the work, built a pilot model,
and constructed a special jig or fixture for several
of the key operations, you would gain considerable
experience, even though you actually produced only
a relatively small number of units.
It is likely, however, that your instructor may
want to develop a mass production project involv­
ing a group of students or even the entire class. This
will provide an experience more closely related to
modern industry, that includes the careful control
of material flow, production schedules, and the
coordination of the efforts of many people.
Using standard hand tools. Length is laid out with pencil and
bench rule. Dowel stock is clamped in vise and cut made with
backsaw. Accuracy and squareness of cut will vary depend­
ing on the skill of the operator. Production rate is about two
pieces a minute.
Using sawing jig mounted in bench vise. Dowel stock is fed
through channel to stop, then clamped with eccentric (ar­
row). Backsaw rides in sawing slot and produces square cut.
When cut is complete and saw raised, part rolls down slop­
ing surface. Production rate is about five pieces a minute.
SELECTING AND DESIGNING
The selection and design of your individual pro­
jects will be determined largely by your personal
interests and desires. When selecting an article to
be mass produced and widely distributed, it will be
especially important that you consider its function
and appearance, and whether others will want to
buy and own it, Fig. 34-4. Business and industry
gives great consideration to this matter, and refers
to it as MARKET RESEARCH. Manufacturers try to
develop products that have a high level of consumer
appeal. They give little attention to the personal
whims off the designer or engineer.
After an article has been tentatively selected for
mass production, study it carefully. Determine
whether it can be adapted to mass production
methods and efficiently built in the shop with
standard tools and machines, Fig. 34-5. By de­
signing and constructing special setups, this
equipment can often be adapted to mass produc­
tion requirements.
Parts that cannot be efficiently produced in the
shop might be purchased from some outside source.
Using table saw fixture. Dowel stock is fed through holder
to stop (arrow). Fixture, guided by strips riding in saw table
slots, is moved forward through the cut as shown. When
the cut is complete, the part drops slightly, clearing the stop.
Fixture is returned to starting position and dowel stock is
again fed through holder. This action pushes the completed
part onto the ramp where it rolls back to stacking area. Pro­
duction rate is about 1 5 pieces a minute.
Fig. 34-3. Comparison of three production methods.
564
Mass Production
Fig. 34-4. This log carrier was designed and built in a classroom
mass production setup.
Fig. 34-6. These four panels represent successive operations
in production of the finished part. From left to right: cut part
to basic size, machine elongated hole for strap, round edges
and sand the panel, and apply finish .
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Fig. 34-5. Drawings of individual parts, production sequence
plans, and assembly details are made and approved before
production begins.
Industry does this quite often. For example, some
factories specialize in turned parts while others pro­
duce only formed plywood units. They then sell to
companies that manufacture the finished items of
furniture, cabinetwork, and other wood products.
Try to visualize the article in production. Deter­
mine if there can be easy movement of materials
through the shop, with storage space for sub­
assemblies and finished products, Fig. 34-6. Large
pieces may create extra storage problems; it is
usually best to select small articles which actually
become advanced woodworking problems when
planned and produced on a mass production basis.
After your sketches and ideas become stabilized,
prepare a working drawing of the article. In addi­
tion to the usual details of construction, include the
number that will likely be produced, along with sug­
gestions on special procedures and setups that
might be used to produce it in the most efficient
way. See Fig. 34-7.
565
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CONSTRUCTION PROCEDURE
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BASIC STOCK
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CUT GROOVE
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CUT OPEN
ASSEMBLE
CUT LIP
Fig. 34- 7. Working drawing of card and pencil box to be mass
produced.
Modern Woodworking
PILOT MODELS AND PRODUCTION IDEAS
As soon as the working drawings are stabilized,
build a sample unit or pilot model. This will provide
a check on the design and may reveal certain
improvements that can be made. As the various
operations are performed they should be studied
carefully to determine what special jigs or fixtures
can be developed for the mass production setup,
Fig. 34-8. Changes and improvements may be so
extensive that several models may need to be built
before a satisfactory solution is found. The original
working drawing should, of course, be corrected
and revised accordingly.
As you think of ways to mass produce the article,
record your ideas in sketch form. These can be very
simple drawings or diagrams. Instead of including
dimensions, try to make the drawing to an approx­
imate scale. Small details should be drawn full size.
An example of such a sketch is shown in Fig. 34-9.
The only "key," or exact dimension, is the size of
the box. The sizes of the various parts of the jig are
usually not critical and c.an be determined by the
good judgment of the builder.
OPERATIONAL ANALYSIS
During the construction of the pilot model, a great
deal will be learned about the operations and pro­
cedures best suited for the production. Make a list
of all the parts and subassemblies. Under each one
list the detailed operations in the order they will be
performed. Working from this analysis, prepare an
operations flow chart, Fig. 34-1 0.
Fig. 34-9. Sketch of a gluing jig for card and pencil box. The
only critical dimensions are those of the box. Sometimes
colored lines are used to define the outline of the work from
the jig or fixture.
Fig. 34-8. Experimenting with various techniques for holding a part for machining. Left. Double-action clamp holds the part
securely, but may interfere with the operation. Right. Special jig designed to hold the part while 1 5 holes are drilled in precise
locations.
566
Mass Production
BOTTOMS AND TOPS
SIDES AND ENDS
OPERATIONS FLOW CHART
RGH. RIP
RGH. RIP
ENDS
SIDES
RESAW
RECISION PLANE
TO WIDTH
INSP.
---------TO PACKAGING
AND SHIPPING
INSP.
----, ,,r I----------\
CARD AND PENCIL BOX
MASS PRODUCTION PROJECTION
NUMBER 5-65
Fig. 34-10. Operations flow chart.
The symbols used in the sample chart are similar
to those recommended by the A.S.M.E. (American
Society of Mechanical Engineers). They show the
sequence and order of operations, assembly points,
and inspection points. Rectangles connecting to the
operations indicate the construction of special jigs
and fixtures. Numbering the operations makes it
easier to assign workers and keep records. When
the chart is complete it should be posted in the shop
for easy reference by all students assigned to the
project. See Fig. 34-11.
PART IDENTIFICATION
The experience you have had in making PLANS
OF PROCEDURE for your regular project work will
be helpful as you prepare an operational analysis
and a flow chart for mass production work.
STEP NUMBER
OPERATIONS AND PROCEDURES
B
V
I
X X
INSPECTION POINTS
PROCUREMENT AND STORAGE
JIGS/FIXTURES
AND TEMPLATES
Fig. 34-11. Flow chart symbols.
567
TOOLING-UP FOR PRODUCTION
Designing and constructing special tools, setups,
jigs, and fixtures is one of the most important steps
in developing a mass production project. It com­
pares with the work of the tool designer in industry.
The tool designer is a highly skilled mechanic and
knows basic mathematics, drawing, and manufac­
turing methods. He or she must be able to analyze
operations and then develop various tools,
machines, and devices so these operations can be
performed quickly, safely, and accurately. Fig.
34-1 2 shows a simple sanding jig used for round­
ing the corner of a production project (also shown).
The construction of the pilot model probably pro­
vided some ideas of what special tooling might be
used. Now you will need to refine these ideas,
develop the setups, and try them out. These devices
are called jigs and fixtures. A JIG is a device that
is attached to the work and guides the tool. A
FIXTURE is usually mounted on or attached to the
machine or tool, and holds and/or guides the work
as the operation is performed. See Fig. 34-13.
Modern Woodworking
There are three requirements a jig or fixture must
meet. It must provide a way to make the part or
perform the operation rapidly, it must be safe to
operate, and it must also produce work that is
accurate within the limits specified. The inter­
changeability of parts is an essential element in
mass production and depends on this accuracy.
Note the jig construction in Fig. 34-14. You will
always need to maintain a higher degree of accuracy
in the jig and fixture building than will be required
in the work that it performs. If the tolerance per­
mitted in the fabrication of the part is 1/1 6 in., then
you will usually need to construct the jig or fixture
to within 1/32 in. of the size requirements. This is
no doubt a higher level of accuracy than you have
had to maintain in your regular project construction,
where you worked with individual pieces and could
easily adjust each part to secure the desired fit.
Fig. 34-1 2. Top. A simple sanding jig made in the shop for
rounding the corners of a part. Bottom. The completed product
ready for delivery.
The size of the production run (number of articles
to be produced) will determine how extensive and
complicated the jigs and fixtures should be. Produc­
tion runs of 10 to 50 units will not justify the
intricate tooling-up that would be required for runs
of 100 to 1000. In industry the tooling-up process
might include the purchase of additional equipment,
specialized machinery, and require extra space and
other facilities. All of this would be expensive; it
would not become a profitable operation until many
thousands of units had been produced and sold.
Fig. 34-1 3. Examine this setup. Determine whether it is a jig
or fixture, based on the definitions given in the text.
(Amerock Corp.)
Fig. 34-14. Building a jig.
568
Mass Production
In the school shop it is justifiable to develop far
more extensive jigs and fixtures than the size of the
run might indicate. They should be designed as
small, separate units that can be quickly attached
and set up for use on benches and machines, then
easily removed and stored.
EQUIPMENT LAYOUT AND PRODUCTION LINES
The selection and arrangement of equipment in
industrial plants is so important that a special plant
layout department is often included in the total
organization. Members of this group are continually
searching for new and better ways to refine and
improve the flow of materials and the use of
machines and equipment. They plan the arrange­
ment of work stations and lay out production lines.
PRODUCTION LINES are the areas where the
product is assembled as it is carried along on
continuously or intermittently moving conveyors.
It requires a tremendous amount of careful planning
to organize all of the tools, machines, supplies,
materials, and workers in such a way that the
product will be produced with speed and efficiency.
Woodworking plants generally do not make ex­
tensive use of moving production lines, except in
the final assembly and finishing departments. See
Fig. 34-1 5. Duplicate parts are usually stacked on
stock trucks or carts and moved from one area or
Fig. 34-16. Cabinet drawer parts stacked on stock cart for easy
movement to machine stations. Partially assembled frames are
stacked on a pallet (arrow) that is usually moved by a fork-lift
truck. (Bertch Wood Specialties)
work station to another, Fig. 34-1 6. A typical work
station is shown in Fig. 34-1 7.
The average school shop is not designed for mass
production work. It would be impractical to make
extensive rearrangements for any particular prod­
uct. It is worthwhile, however, to make a drawing
Fig. 34-1 5. Conveyor carries piano cabinets along the assembly line in a modern wood­
working plant. (Kimball International)
569
Fig. 34-1 7. Workpieces moving out of a double-end tenoner. They have been trimmed to
size. In addition, the edges have been rabbeted and the dado for the web frame has been
cut. (Bertch Wood Specialties)
of the equipment layout as it exists, assign work
stations, and draw coded lines indicating the flow
of material. This assignment will be helpful, even
though there may be overlapping of routes and other
interference that would not be permitted in a regular
industrial operation.
After the work stations have been established and.
the flow of materials and parts has been determined,
try out each operation. It is especially important to
check the time required at each station. If the time
seems so long that a bottleneck (delay) may be
created, one of the following adjustments should
be made:
1 . Refine the procedure or method.
2. Improve the operator's performance.
3. Break the operation down into two or more
steps.
4. Duplicate the setup and add more operators
(workers).
5. "Stock pile" or "bank" materials in overtime
work sessions.
In the school shop the movement of material,
parts, and assemblies is limited to stock carts, tote
trays, and stock boxes. A stock cart, Fig. 34-19,
can be used to transport material from one station
to another. It can also serve as a storage unit. At
the beginning of the work period it can be quickly
moved from the storage area to the work station
and returned at the end of the session. Tote trays
and boxes can be used in about the same way for
small parts, Fig. 34-20.
HANDLING AND STORING MATERIALS
The transportation or flow of material and parts
from one machine or work station to another
requires special equipment. Woodworking industries
use pallets, lift trucks, stock carts, roller conveyors,
belt conveyors, and palletized conveyors. When
machines are set up to produce a specific part, or
certain subassemblies are being fabricated, many
more units are produced than can be immediately
used in the final assembly section. They are
stockpiled and stored, Fig. 34-1 8.
570
Fig. 34-18. Parts and subassemblies in storage.
(Kimball International)
Mass Production
materials, and money.
Inspection points will vary greatly as to the
methods and procedures used. At some points, a
visual check may be all that is needed. Parts are
stacked together so that imperfect ones can be
quickly spotted. Other points may require that each
part, or every tenth part, or a certain percentage
of parts be accurately checked with a rule, gauge,
or some special measuring device or instrument.
Industrial operations often require an entire depart­
ment or group of experts to work in this area. It is
known as QUALITY CONTROL.
The final inspection is very important in furniture
and cabinetwork production. The unit must be
square and true. Drawers, doors, and other work­
ing parts must fit smoothly and with the proper
clearance. And the finish must also be carefully in­
spected. If a company wants to maintain a reputa­
tion for producing quality products, it is necessary
to carefully inspect each unit before it is packaged
and shipped.
Fig. 34-19. A stock cart that is adaptable to production work
in the school shop.
OPERATING THE PRODUCTION LINE
If the planning and preparation has been carefully
done it will be enjoyable and exciting to actually get
the article into production. A high level of perfec­
tion in timing and movement of work, however,
should not be expected. Even in industrial plants,
where personnel are highly trained and experts han­
dle the work, it may require many weeks or months
to perfect production lines and remove all the bugs
(problems). Figs. 34-21 to 34-32 show a mass pro­
duction project carried out in a school shop.
Workers can be assigned to the various work sta­
tions, using the coded numbers on the operations
flow chart. Other systems can also be devised.
Everyone should have an opportunity to practice
their operations before the production run. Some
workers may need special training and extra prac­
tice. When the run is of short duration, a given
student may have several assignments, first at the
beginning of the line and later at the end.
Fig. 34-20. A tote tray can be used for organizing, transporting,
and storing small parts. If the parts are carefully stacked (as
shown) it is easy to count and check them.
INSPECTION POINTS
In the operations flow chart, you have probably
noted the squares that are used to mark inspection
points. They usually follow those operations where
high accuracy and quality of work is especially
important. You can readily see that it would be poor
practice to just wait and see if the parts fitted
properly at another station along the production line.
By that time many defective pieces might have been
produced, resulting in a great deal of wasted time,
571
Fig. 34-21. Using a carrier board to plane stock to finished
thickness.
Modern Woodworking
Fig. 34-22. Precision planing stock to width on the shaper. Ring
guard has been removed for this photo.
Fig. 34-26. Gluing setup for assembly of sides and ends. The
polyvinyl glue makes an initial set in the time required for the
subassembly to travel around the turntable.
Fig. 34-23. Portable belt sander, held in a cradle to sand thin
side strips.
Fig. 34-27. Rabbet joints are pressed against the applicator
bar after glue has been spread on bar with roller.
Fig. 34-24. Fixture for cutting box ends to exact length. Regular
saw guard is used for this operation.
Fig. 34-28. Gluing tops and bottoms to the side and end
assemblies. The clamping units are mounted on a carrier that
is waxed on the underside and slides back and forth easily in
front of the operator.
Fig. 34-2 5. Sides are cut to length and rabbeted in a single
operation. A section of a dado head is mounted on each side
of the saw blade. Note plastic-covered guard.
572
Mass Production
Fig. 34-29. Sanding outside surfaces on a stationary belt
sander.
Fig. 34-32. Top. Spraying a final coat of lacquer on outside
surfaces. Small turntables are mounted on the larger revolv­
ing table. Bottom. Finished boxes.
Fig. 34-30. Cutting the box open. Cut is made half way on
one side and then the box is turned over to cut the othe side.
stations and keep the flow of work moving. Bottle­
necks will very likely develop because of errors in
planning, malfunctions in equipment, or inability of
the workers. Sometimes the problems may be so
severe that production will need to be closed down
for the day. While supervisors or foremen make
adjustments and repairs, the balance of the workers
can return to their regular individual projects.
RECORDS AND EVALUATION
Fig. 34-31. Cutting a rabbet on the lower section to receive
the lipped top. A small bench shaper is being used.
Parts that include time consuming operations and
are likely to cause problems during the production
run should be fabricated ahead of time. Also, all the
basic stock should be selected and rough milled.
It will be quite a challenge to coordinate all the
573
At the end of the production run it will be
especially valuable to review the total operation.
Records should include such items as number of
parts produced, total time required, percentage of
waste or number of parts rejected, parts reclaimed
or reworked, and total material and supplies used.
These records should be studied and evaluated
along with a review of some of the problems and
bottlenecks. Improved practices and organization
will probably be evident. These should be discussed.
Highlighted also, should be some of the operations
or special jigs and fixtures tbat performed especially
well. Those that did not meet expectations should
also be pointed out, along with reasons for their
failure. Fig. 34-33 shows several successful jigs
and fixtures that were built in the school shop.
Modern Woodworking
Fig. 34-33. Shop built jigs and fixtures used in mass production projects. Top left. Fixture mounted on lathe bed supports portable
router. Spring (not visible) holds guide against template as carriage is fed along the cut from right to left. Top right. Blanking-out
top contour of book holder end-piece. Router cut is guided as edge of base moves along template. Bottom left. Four place assembly
and gluing jig. By the time the fourth compartment is filled, the first unit can be removed. Bottom right. Fixture on disk sander
accurately smooths one side and both circular ends in a single operation. Carrier is guided by pins located on underside.
(Noel Mast, Dennis Marsh, Wilson Forbes)
TEST YOUR KNOWLEDGE. Unit 34
PRODUCTS
From the very start of a mass production project,
a plan must exist for the use of the articles that will
be produced. For short runs, the students involved
in the work may want to divide the articles among
themselves. On larger production runs it may be
necessary to organize and establish a business
committee. They can handle the distribution and
sales, as well as control the money and pay for
materials used.
Even though the emphasis in the school shop is
directed toward the production aspects of a mass­
produced article, some attention can be given to a
study of such business and financial factors as
capital outlay, raw material costs, labor costs,
overhead and other expenses. Organization and
control of all these, along with an efficient sales and
distribution plan will be essential if the entire opera­
tion is to be profitable. In our modern industrial
plants, the smooth running and efficient production
line will help insure a profit only if it is a part of a
sound and well-administered business structure.
Please do not write in the text. Place your
answers on a separate sheet of paper.
1 . List four elements that receive special atten­
tion in mass production plants.
2. When consideration is given to the function,
appearance, and consumer appeal of a product, this is known as __________
3. An experimental or sample unit of a product
to be mass produced is called a(n):
a. Pilot model.
b. Production idea.
c. Operational analysis model.
d. None of the above.
4. Rectangles used in an operations flow chart
indicate the construction of special ____
and _____
5. A square on the operations flow chart indicates
procurement and storage. True or False?
6. What is the difference between a jig and a
fixture?
7. What are some of the responsibilities of per-
574
Mass Production
sons working in the plant layout department?
8. List three reasons why bottlenecks are
sometimes created on production lines.
9. Why is it important to detect defective prod­
ucts as soon as possible on the production
line?
10. How valuable is it to review the total opera­
tion of a production run? Why?
ACTIVITIES
1 . Select or design a small article that can be
mass produced in the school shop. Make an
operational analysis and then prepare a flow
chart.
2. Prepare sketches of a jig or fixture that could
be used for some "key" operation in a mass
production project. Include a written explana­
tion of how it works and some of its features.
3. Design a gauge that could be used to check
the thickness or width of mass produced parts
to determine if they are within acceptable
limits. Such a device is commonly called a "go
and no-go" gauge. It has two gaps spaced so
an acceptable part will slip by the first gap but
not the second.
4. Study the history of the development of mass
production. Learn of the contributions made
by James Watt, Eli Whitney, and Henry Ford.
Prepare a written or oral report for your class.
These solid wood chairs are excellent examples of mass produced wood furniture pieces.
575
(Period Furniture, Inc.)