Technology of watch production - part 2

"Technological discipline " consists in the faithful carrying out of all

instructio�s appearing in the engineering charts , and cons titutes one of the
main conditions for the manufacture of high- quality products .

Watchmaking plants make us e of s everal different kinds of technical

documentation, for different purpos es .

The degree to which the technological process is provided with technical

documentation, and the thoroughness of the documentation, depends on the
type of production.

Types of Production

Depending on the output volume and the character of production organi

zation, one distinguishes between: u n i t p r o d u c t i o n , s e r i e s p r o -

d u c t i o n a n d m a s s p r o d u c t i o n .

Eache of the abo ve types covers a range of s ituations , and intermediate

cas es occur . Thus , depending upon the number of types of products which
are produced and on the quantity of products in a production s eries , series

production can be large - series or small - s eries . Mass production can be

organized as flow-line mass production.

U n i t p r o d u c t i o n involves the manufacture of single products or of

small batches mf products (s everal pieces ), with large time intervals be

tween successive runs . Universal equipment and devices and general -pur
pose tools are us ed, permitting the proc essing of parts of various dim en

s ions and diverse configurations .

Personnel engaged in unit p roduction must have high qualification, be

cause of the diversity in the operation they must perform .

this type of production the details of the technological processes are

not worked out in advanc e . The general s equence of ope rations is pres cribe d

f o r most parts , and only for particularly comple x parts are the processes

worked out in more detail .

Costs are high and production is slow under unit-production conditions .

S e r i e s p r o d u c t i o n involves the manufacture in batches of s everal

products which alternate periodically. One or several operations are car

ried out at each workplace , and either the entire batch of parts pas s es from

operation to operation together, or it is divided into groups .

S m a 11- s e r i e s p r o d u c t i o n is characteris tic of plants producing

various products in s mall batches .

The equipm ent used in small- s eries production is mainly universal but

special devices and specialized cutting tools and measuring instruments

are also us ed to a l imited extent. The processes for small-s eries produc

tion are worked out in detail, and norms and rates are fixed .

Operations are associated with available equipment of a particular type,

or even with a particular machine .

La r g e - s e r i e s p r o d u c t i o n is characterized by the same basic

features as those which characterize small - s eries production , but consider

able differences exist b etween the two typ es of production.

The diversity in the parts manufactured is smaller in large- s eries pro

duction. The s eries are much larger and the pro duct designs are more

stabl e in time . Special devices , cutting tools and measuring instruments

are us ed liberally, and this investm ent in tools is usually economically

justified . Production costs a r e lowered, and the p roduction-time cycle

shortened in large - s eries production as compared with small - series pro
duction.

Ma s s p r o d u c t i o n is the s teady production of uniform products .

The elem ents of work have a narrowly specialized character, and a specific

operation is assigned to each workplac e .

Wide u s e i s made i n mass production of specialized and automatic m a

chinery, special cutting tools and m easuring instruments , and a variety o f

automatic and mechanized ins truments and devices .

The large investments involved in the p reparations for mass production

make it ess ential that the product design, the technological process , and

the equipment design be worked out carefully and thoroughly.

Because the same operation is constantly repeated at a given workplace,

and becaus e special equipment is widely us ed, the personnel quickly master

the operation entrus ted to them and achieve a high rate of p roductivity.

Production costs are lower in mass production than in any other type of

production proces s .

The large investm. nt necessary for the preparation o f mass production

is justified economically by the increas ed output and the lower production
costs .

Becaus e only one operation is performed on each machine, s etup time

is saved and it is pos s ible to achieve higher rates of equipment utilization

than in other types of pro duction.

If the workplaces (machines ) are arranged in accordance with the sequence

of operations , the part will pass directly from workplace to workplace and

emerge completely proces sed after the final operation.

In order that this flow be possible, all operations must take the same

amount o f time . In practice, however, the time required by the various

operations is usually not the s am e for all of them and both technical and

o rganizational measures are taken with the aim of equalizing the time re

quired by the different operations : improvement of the design of clamping

devices in order to reduce the loading tim e, introduction of multiple- chuck

ing devices , etc . In particular cases c ertain ope rations may be c onducted

in parallel at s everal workplaces .

A mass production process in which the work is c onducted along a flow

line is called f

o w -

i n e p r o d u c t i o n.

The most important problem in flow-line production is the synchroniza

tion of operations , to ensure that all operations require the s ame time or

a multiple of it. The number of product units or parts coming off the con
veyor per unit of time serves as an index of the flow-line productivity.

Plant Structure

Each plant is divided into shop s , each of which has a given class of equip

ment, and wo rkers and engineering pers onnel having specialized in s imilar
fields .

The following are some of the types of shops: stamping, automatic ma

chines , mechanical coating, (electroplating, lacquer - coating), heat treat

ment, ass embly, etc .

The shops in which parts are produced and ass embled are called b a s i c

shop s .

Plants making pocket- and wris twatches have the following basic s hops :

preparatory shop, s tamping shop, automatics s hop, plate -and -bridge shop,
cas e shop�' (cases, dial s and hands ), escapement shop (sometimes called

"movem ent" shop ), mechanical shop ( gears, barrel parts and pallet levers ),

coating shop (electroplating), heat-treatment shop, and ass embly shop .

The entire proc ess of watch manufacture, beginning with the raw mate

rial and ending with the finished product, takes plac e within the basic shops .

In addition to the basic s hops , each plant has a u x i l i a r y s h o p s which

provide production s e rvices .

Some examples of auxiliary s hops are the tool shop, the m echanical

maintenance shop, the power shop, and the construction- maintenance shop .

The plant man�gement compris es the following departments for produc

tion control:

1 . The production- dispatching department plans the work s chedules of

the production shops and supervises the fulfillm ent of the plant ' s production
program . The manager of the production- dispatching department is the

production manager and all the basic s hops of the plant are under him .

2 . The chief-production engineer ' s department is charged with design

ing the technological processes and supervising their application in produc
tion. This department establishes the technical norms and rates for the

processes, designs the production equipment, and sets consumption s tand

ards for the basic and auxiliary materials .

3 . The chief - designe r ' s departm ent is charged with designing the prod

ucts to be manufactured by the plant (in this cas e - watches ).

A watch laboratory is attached to this department for the purpos e of

tes t�ng both watches produced by the plant and prototypes of new designs

to be introduced into production.

4 . The technical- supply department supplies the plant with all basic and

auxiliary materials .

5 . The chief- m echanic ' s department is charged with machinery mainte

nance and with keeping the buildings , installations and power system of the

plant in working condition .

The technical - control department i s responsible for the compliance

with technical instructions in the shop s , tests the rna terials received by the
plant and inspects the finished products .

MACHINING ACCURACY

Machining accuracy is of utmost importance in instrum ent- making tech

nology and is especially important in watch manufacture .

Processing accuracy is unders tood to refer to the degree to which the

finished parts correspond to the form and dim ens ions specified by the draw

ing.

Variations in the dim ensions of parts produced can result from many

factors which influence the manufacturing proc ess . Inaccuracy in the

•

The plate-and-bridge shop and the case shop are combined in some '" atch plants inro one plate-and-case shop.

machine or cutting tools, tool wear, inhomogeneity of the material being

processed, and deformations in the machine, the tool or the part during

processing, are a few of thes e factors .

Errors

In the process of machining all parts of the machine, the tool and the

blank are subjected to cutting forces which caus e deformations . In drilling

deep holes the drill is deflected from the desired hole axis; in turning shafts

or axles between centers on a lathe the axles bend, etc .

Deviations in the dim ensions and the form of the parts being made are

due to caus es such as thos e described above; these deviations are usually

called errors ard are classified as being of the systematic or of the random

typ e .

A n error i s called s y s t e m a t i c i f i t i s constant for all the parts of

a given batch or if it changes in a regular manner within the batch.

Thus , if holes are drilled using a drill which is 0 . 2 mm larger than it

should be, all the holes will be larger by 0 . 2 mm than if they had been drilled

with the correct drill . This will be a systematic error. A nother example

of sys tematic error is that resulting from the wear of the cutter, which

leads to a pro gress ive increas e in an external diameter or a progress ive

decreas e in an internal diameter of a machined part.

An error is called r a n d o m if it has different values for different parts

within the same batch and is not subject to any apparent law. Holes drilled

by the s ame drill will have various dimensions , due to various factors of

random origin.

The systematic errors are determined by analytic - calculation methods

and the random errors are determined statistically. A formula is known

which establishes the relationship between the various elements of the

sys tem machine- tool - part and can be us ed for the analytical method .

However, this method i s inconvenient becaus e l engthy computations are

necessary for each factor . For example, 72 factors are known to affect
hobbing.

It is difficult to determine the combined influence of several s imulta

neously operating factors or primary errors using analytic - calculation

methods . Calcul ation methods are, for these reasons , being widely s up

plemented by s tatistical  m ethods  of investigation.  According to the statis
tical  methods ,  the totality of  many phenomena is  treated  rather· than  indi
vidual phenomena o r  factors .  The  process  of investigation is  split  into  two

stage s - collection of experimental data ,  and its  proces s ing using the methods
of mathematical  s tatistics  and the  theory  of probability.  We  will  illustrate
the  application  of this  metho d  by  a  concrete  exampl e .   Let u s  assume  that

a batch of 1 0 0 parts has been manufactured according to an established

technological process .

If the dimension in question

(d=

1 0 m m ) is meas ured in a batch of parts

processed under uniform conditions , we will obtain different values of the

dimension in the different parts , varying between a maximum of 1 0+0 . 014

1 0 . 0 1 4 mm and a minimum of 1 0- 0. 0 1 2

9 . 988 m m .

Content .. 1 2 3 ..