Austin’s built Transfer Machines
Mr Horace Holbeche, was Chief General Superintendent of Jig and
Tool Design at Longbridge, and was responsible for the design and
manufacture of the Austin Transfer Machines and Unit Machines.
Through his expertise “The Austin” was able to automate the
machining of the major engine components which kept costs down. He
was born in 1901 and was a pupil at Kings Norton Secondary School
(later Kings Norton Grammar). On leaving school he went to work at
“The Austin” and stayed there all his working life, retiring early
at the age of 67 because he could not agree with the policies of
Lord Stokes. He was mortified that a company like BMC should
effectively be taken over by Standard Triumph.
This article uses extracts from a paper presented jointly by Mr
Holbeche and Mr F Griffiths, who was Chief Project Planning
Engineer, to the Coventry Section of the Institution of Production
Engineers on Tuesday November 16th 1954.
How it all started
One of the most pressing
problems facing production engineers in the mid 1950s and which is
still the case today. Was the need to manufacture articles more
cheaply, and in ever greater quantities. Only if costs are kept
down can a company sell at a price which will stand up to
increasing competition at home and abroad. The motor car industry
is one in which competition is fierce, and one in which costs must
be kept low in order to bring a semi-luxury article within the
reach of all. It is therefore, an industry which must be forever
trying to make "something for nothing".
Showing how individual standard single
machines were linked together.
In the early 1950s machine
tools and production methods had not really changed. Because in the
war years it was safer to use the money available to invest in
known methods of production. It must be remembered that the main
costs in producing even the smallest component are two-fold, raw
materials and labour costs. Taking the raw material cost such as a
castings or forgings you are looking at a cost of about £45 per ton
(1950 prices), and resold for scrap at about £5 a ton. We are thus
paying £40 per ton for metal which we do not want, and which costs
us a lot of money in labour and capital costs to remove. To give an
instance of what this can amount to, here are some figures for the
material wastage’s with some of our components.
For every 2 tons of metal put into the Forge not much more than 1
ton finishes up as the machined product. For every 2 tons of
castings poured approximately 1 ton finishes up as a machined
product. For every 3 tons of bar put into the Automatic Shop only 1
ton emerges as the finished product.
The amount of money spent
per year both in Capital and Labour, for useless work, is therefore
very considerable. Fortunately, we are now beginning to receive
some benefits from improved methods of casting and forging due to
shell moulding, and investment processes in the foundry, squeeze
forging methods in the forge, and cold heading to replace bar
autos. It is hoped that, in the near future, the amount of metal
which must, of necessity, be left on the component will be no more
than can be easily removed in "sizing and finishing" operations.
Improvements in these basic processes are bound to affect the
amount and type of plant required for machining operations. We
must, therefore, be prudent as to the type of machine which we
install, and it would obviously be wise to restrict capital
expenditure as much as possible during this transition
period.
However, we cannot afford
to stand still, we must not refrain from replacing worn out
machines, or from attempting to improve our machining methods. It
seems logical, then, to buy only machines which can be built of
basic standard units, quantity produced, and therefore much less
expensive, which will be easy to construct and maintain, and minus
all the universal trimmings which the normal machine seems to carry
and which are not required for line-flow work. These machines would
on the other hand be easy to adapt from one operation or job to
another as changes take place.
The Position at the End of the War
At the end of the WWII we
had a lot of plant in our factories which had been bought anything
from ten to twenty years previously. This plant had been in
continuous use, first on car production, and then, during the War
on Government contract. Some of this plant could be used again
after overhaul, but quite a lot needed to be replaced. Speaking
generally, the standard machine tools, such as millers, drillers,
turning and boring machines had reached a high state of efficiency.
The skill of manufacture, as far as accuracy was concerned, had
been “built in” to the machine and did not now lie with the
operator. The operator's skill lay in his manual dexterity in
loading and unloading jigs and fixtures and operating his machine
controls. With new machines coming along that had an automatic
cycle, it was now possible for an operator to now handle more than
one machine. The actual cycle time had also been reduced through
the use of air operated jigs and fixtures, with the operator
already handling his maximum number of machines.
As far as manufacture was concerned, the cost of producing was
mainly a labour cost, and depended more on the number of machines
an operator could handle than on the length of the operations
themselves. The aim, of course was to keep the operator busy for
the whole unit cycle time, taking into account loading and
unloading times, walking time (if any) and fatigue and rest
allowances. This unit time is of course fixed by the required
production rate per hour. As to all intent and purposes speeds and
feeds as used in the production factories are, and have been stable
for the last 20 years, and as any considerable alteration to these
speeds and feeds is not yet discernible, we can say that we must
turn to other aspects of producing to make any considerable saving.
For continuous high production it does seem that speeds and feeds
should go down, rather than up, as tool changing can quite easily
become a major consideration apart from the possible high cost of
tool replacement. As can be seen from the previous statement that
appeared to us, that the labour content of the job would have to be
the main approach to make any considerable savings. The best way to
do this would be to make loading and unloading and machine control
automatic and to transfer the job automatically from one machine to
the next, and so enable any one operator to increase his
productivity by covering more operations. This could be done either
by putting automatic devices between standard machines or by
building complete transfer machines.
So at first it was
necessary to look at putting automatic devices between standard
machines, which would allow an operator to look after more than one
machine, thus reducing labour costs, it was not a great step
forward in reducing costs.
Possibility
of Making Machines of Standard Units
At this stage it seemed
sensible to design standard units that could be linked together as
this type of transfer machine could be more cheaply built than
using standard machines link up together with
automation.
It was necessary to design
these units which would consist of the following elements, units,
bases, unit beds, ends, columns, electrical panels, etc along with
self-contained driving and feed power units. These could be mass
produced in a few sizes to suit the range of work we were liable to
encounter. There would be other advantages as each size of power
unit could be made to do a variety of operations according to the
attachments fitted. With slight modifications to the controlling
trips and electrical gear, we could mill, drill, and bore with the
same size heads.
A bonus with this system
would be that maintenance problems would be eased if the various
parts were standardised, and we would not have to carry such a
diverse stock of spare parts.
Different
Makes of Transfer Machines
Having decided to go with
principle of unit construction transfer machines, the next thing
was to consider their construction in more detail. So what was
around at the time, well the Americans had been working on this
type of machine for some time, mainly in connection with the
production of cylinder blocks, and similar large components. As a
result of this, their machines had no moving fixtures, merely
transferring the component between stations and having separate
clamping arrangements at each station. Our intention was not to
confine ourselves to cylinder blocks and large components, but to
cater for a number of small parts also. We therefore decided that
the component should be held in a fixture which would be bolted to
a platen, and that the platen should be indexed through the
machine. In this way our machines would be more universal and
easier to change over from one component to another if
required.
In France, Renault had also developed their own type of transfer
machine. They had standardised units, bases and columns and also
used platens. There was one major advantage which they appeared to
have and that was that between each two-station working section
they had inserted a bridge piece. This served the dual purpose of
making alignment of the machine length unimportant, and also
providing space for the tool setter to get in to make tool changes
or adjustments. We decided that although this method might be the
best, it was, on the other hand, wasteful of floor
space.
Decision Relating to the Production of Transfer
Machines
Having decided to build
transfer machines and the broad principles of constructions, the
next question was actual manufacture of all the various parts. We
had made the first machine ourselves in order to get some idea of
the problems involved, but did not wish to go into large scale
production as we were essentially in business to manufacture motor
cars. So an exhibition was arranged with a large number of
components that we thought were suitable for production on this
type of transfer and unit machine.
There were no British
machines at that time which could compare with our proposed method
of construction. As we had designed and built a transfer machine to
do milling, drilling, countersinking, and reaming on one of our
front suspension components. This machine had all the working
stations on the top and one side only, with the other side clear
for tool setting and changing. However, as the component had to be
worked from both sides it was necessary to turn the fixture round
on the machine and this of course meant two stations solely
occupied with this operation. This type of design, whilst good from
the tooling point of view, was ultimately modified as being too
wasteful of floor space. All the later machines having work heads
on both of the centre beds, and sometimes
overhead.
At this stage various
machine tool manufacturers were asked to send representatives for
the purpose of evaluation, and for the possibility of co-operation
in producing the required units. They were told that, ultimately,
these machines would be installed on all types of work throughout
the factory. We are glad to say that Messrs. Archdales of
Worcester, were interested and ultimately joined with us in the
extensive programme which was embarked upon.
It was necessary to look at the various costs between standard
machines linked together, and a transfer machine. The capital cost
of the transfer machine worked out at £25,903 against £30,850 for
the standard machines; a saving of roughly £5,000. If we looked at
the floor space needed for each system, again the transfer machine
came out on top requiring 390 sq. ft. as against 500 sq. ft for the
other machines. If we then look at the overall costs over a two
year period. Yet again the transfer machine in costs per hour came
out on top at £3 13s. 3d., with the conventional system costs at £4
8s. 9d. The labour required to operate the transfer machine is two
operators, one loading and one unloading, the cost per hour being
11s. 0d. The cost of the labour on the standard machines is £2 17s.
2d. There is one further point to note about this comparison, the
transfer machine will produce 3,000 components per week against an
output from the standard machines of 2,500 per week. So to sum up,
in replacing standard machines by a transfer machine we have
increased output from 2,500 to 3,000 components at a total saving
of £123 per 40 hour week. So it will be seen that reality has
justified the dream. The example given above is of an actual
machine which is now running on A40 Cylinder Block production, but
when the decision to use transfer machines was made, we had of
course to work on estimates only. However, as the saving seemed to
be worthwhile, our Directors decided to go ahead with the
production of transfer machines.
Problems of Manufacture
The manufacturing programme
that was approved by the board consisted of producing the following
items, 50 pairs of ends, 200 - 2 and 3 station beds, 700 consoles,
500 columns, 1,200 unit heads, 1,200 control panels and numerous
multi heads, fixtures, etc. It was decided that while Messrs.
Archdales should produce the ends and beds other outside
manufacturers would produce all other requirements except the unit
heads which would be produced at the Austin Motor Company in the
North Tool Room.
For this purpose a special machine shop was set aside with its own
personnel and management. The reason for this was twofold. In the
first place we were going to produce quite a large number of units,
and they would be wanted fairly quickly, and secondly it was
thought that the only reasonable way in which costs could be kept
down was to manufacture on a mass-production basis. Accordingly the
shop was provided with its own machines and equipment with Jigs for
boring and other operations, in the same way that we would equip
motor car component production lines.
Altogether the capital cost involved in setting up the Unit Head
Shop, as it is called, cost in the region of £60,000. The total
number of units manufactured to date is about 2,150. These have
been used on both transfer and unit machines.
When all the necessary parts for a new transfer line had been
manufactured. They would be sent to Dalmuir building, where the
line would be assembled. This gave the opportunity to check out the
running of the line, iron out any problems etc. When the line was
running satisfactory, it would be striped down into its various
units and then rebuilt in its final production location at
Longbridge.
Apprentice Brian Marsh (RHS) hand scraping the surface for
flatness. Dalmuir 1955
Electricians training on how to maintain the Control Panel
Team Meeting
_____________
Both views shown without
the Unit Heads
Points of Interest Regarding Transfer
Machines
Multiple
Indexing
On
every machining line there are always one or two operations which
take longer to perform than the rest. For various technical reasons
it is not always possible to break these down into smaller time
factors or steps, and so, on a transfer machine, the cycle time is
governed by these particular operations. We have found a method of
overcoming this difficulty by duplicating the stations with the
longest times and providing a compound indexing system which
enables the overall machine to be run as a unit, and which by
shortening the time cycle, allows a transfer machine to produce
more by the addition of a few stations instead of duplicating the
whole machine. Another point is that it is a fairly simple matter
to rotate the component through 90 deg. both in the vertical or
horizontal planes in order to work on other faces of the component.
The governing factor will be how much of the fixture is left after
allowing for all cutter clearances.
Apart from the technical
side there are other points arising from the use of transfer
machines. Firstly, it is extremely difficult for operators from
stock-piling work between machines, owing to tool changes, personal
reasons, breakdowns and discrepancies in floor to floor times of
adjacent machines. The floor space so occupied represents
production space, rent, buildings, lighting, heating, etc., whilst
the stock also represents idle capital. The ideal condition is to
have the smallest quantity possible in the manufacturing pipeline,
that is, of course, one component per machine. The transfer machine
goes quite a long way towards meeting this ideal, admittedly it
sometimes breaks down, or has to be stopped for tool changes, but
there is no out of balance of stock created between the beginning
and end of the machine, only strategic stock being required between
the transfer machine and the next machine.
The question of consistent
quality production from a transfer machine requires an entirely new
approach. The present method where an operator is loading and
unloading a group of individual machines has led to the habit of
the patrol inspector, using the operator as an auxiliary inspector.
The transfer machine, of course, does not allow this because as far
as the operator is concerned, what happens between him and the
other end is out of his control. To safeguard this position, it is
necessary to put in gauging and clearing stations, which, by use of
the latest Sigma type of gauge, can stop the machine should out of
size tolerances be detected.
Shop Organisation
It
is essential that an efficient shop organisation should be built to
back up transfer machines if the best is to be got out of them. In
this connection three points stand out. Firstly, if the machine is
to produce accurately and consistently components, tools must be
kept up to a good standard. It is necessary, during the trial and
pilot runs, to carry out an analysis of the life of all the tools
on the machine between regrinds, and also the total life. From this
can be determined the maximum interval which can be allowed between
tool changes. It is a good policy to stop the machine at definite
times in the day and change certain tools before proceeding with
the next run. Tool changing can be assisted, to a great extent by
the use of setting gauges. For instance, we provide a drill setting
gauge for each multi-head so that the new drills can be set to the
correct length in their adjustable holders before insertion to the
multi-head. In the same way boring and other tools can be pre-set
before fastening in the machine. To help this we also provide tool
cabinets for each machine, which contain a complete set of tools
and setting gauges for each station.
The second point concerns inspection. As mentioned before, we can
fit automatic gauges at vital points on the machine, but this is
not enough in itself. There must also be a check by means of a
patrol inspector who will test occasional samples to see that
deterioration is kept under control.
The third point is maintenance. In order to keep production at full
blast, a team of men must be trained who know the machines well and
they must be backed by an ample supply of spares. Should a unit
head break down it should be possible to whip off the defective
unit complete and substitute a new one in a short period. As so
much depends on the electrical switches, relays and interlocks, the
electrician is obviously a key man in this team, and will become
more important as development proceeds. Of course, the question of
maintenance is simplified by the standardisation of the various
machine parts.
_____________
THE DESIGN OF TRANSFER MACHINES
Presented by H. W. Holbeche
In going on to a
description of the design of transfer machines, it must be
emphasised that there is no one solution to the problem, and to
describe all the variations in design would be beyond the scope of
this paper. The aim, therefore, has been to give a technical
description of the B.M.C. machines and the reason for the adoption
of specific designs.
Three
Main Types
There are three main types
of transfer machines, the straight line type, the rotary indexing,
and the horizontal drum type machine. In order to obtain any of
these machines in a reasonable time it is essential to standardise
the various constituent parts, and the first necessity is to have a
range of unit heads which can drive the tools and supply the
necessary fast and slow traverse motions to those
tools.
There are various types of
unit heads, and the method of traversing may be hydraulic, cam
operated, hydro-pneumatic, or mechanically by lead-screw. In the
search for a completely universal unit head it was decided to adopt
the screw feed principle in preference to the hydraulic principle,
partly because this type of head is the only one which can be used
satisfactorily for tapping, in addition to the usual drilling,
boring, reaming, etc.
Austin
Unit Heads
Five sizes of unit heads
were designed, all having the same basic design, ranging from the
small No. 0 Unit, suitable for small drills and high spindle speeds
up to the No. 3 size for heavy work involving drill pressures up to
10,000 lbs.
Drilling
‘B’series cranks in No 5 machine shop
STRAIGHT LINE TRANSFER MACHINE
There is a difference of
opinions as to whether platens should be used for carrying the
work, or whether non-platen machines are preferable. In the case of
the platen type machine, a fixture is attached to each platen. The
component is loaded in this fixture and the component fixture and
platen are indexed from station to station along the length of the
machine. The platen has to be accurately located and clamped at
every station, and unless this location is extremely accurate, it
will be realised that work done at one station may not be relative
to the work done at a previous station.
In the non-platen type of
machine there is a clamping and locating fixture permanently fixed
at each station; the component is transferred from station to
station, located and clamped. An advantage of this method is that
there are no platens to return to the loading end. Another
advantage is that the pilot bushes for the tools or pressure plate
are incorporated in the fixture or bracket which carries the
component locations, thus giving greater accuracy. This system is
most suited for handling components such as cylinder blocks and
cylinder heads, and some types of gearboxes; in fact any job which
has a suitable face or faces to locate from. It is, however, almost
impossible, or at any rate very difficult to machine such
components as exhaust and inlet manifolds, connecting rods, axle
cases, valve rockers, etc., on a non platen
machine.
As one of the desired
features of the proposed machines was that they should be
constructed from standard sections carried in stock and be capable
of application to any type of component likely to be required, the
platen type of machine was decided upon. Subsequent experience and
the quest for completely automatic machines requiring no operators
have shown that there is a need for both types. On investigation it
was found that the design of the transfer bed for the platen type
of machine could also be used without alteration for the non platen
type.
Platen type machines can be
run by one or two operators depending on the relative machining and
loading times. If the loading and unloading times together are less
than the machining time, then the machine can be run by one
operator provided that the platen with its fixture and component
can be returned automatically to the loading
station.
Machine
Construction
The backbone of the machine
is to built up from a number of centre beds, each bed having either
two or three stations, together with a loading station at one end
and an unloading station at the other. The machine is completed by
attaching to the centre beds the necessary branch beds on which are
mounted the unit heads, columns, etc.
Platens
The work holding fixtures
are mounted on standard platens. These platens are grooved at the
sides and slide along the machine on keep plates bolted to the
machine beds. The platens are transferred from station to station
by a transfer bar pulled by a hydraulic cylinder, the standard
distance of transfer being three feet. To the transfer bar are
attached small blocks, which engage hinged pawls projecting from
the underside of the platen, along with bushed location holes for
positioning the platen accurately at the stations. The transfer bar
positions the platens only approximately, vertical plungers
operated by hydraulic cylinders through toggles, locate the platen
accurately, and clamp it upwards against the keep plates. There are
four clamping plungers at each station, two of which also act as
locators for the platen. It will be noticed that it is the
underside of the keep plate which forms the vertical location, so
that wear on the plate or the platen caused by sliding action does
not affect the accuracy of the location. This feature is the
subject of a patent taken out by Messrs. James Archdale & Co.
Ltd.
Transfer Machine in East Works for ‘A’
series blocks
_____________
It must be remembered that Austin were
among the pioneers of the automatic transfer system, which aims at
combining in one machine, operations usually performed by a series
of separate machines with separate operators.
Having a transfer line has many cost advantages. A typical transfer
machine producing cylinder blocks for A.40 engines, which has
replaced a line of 13 other machines. Is now producing 3,000 blocks
a week compared with 2,500 turned out by the standard machinery. It
cost a total of £25,903 against £30,850 for the standard machines.
Yet it has cut operating costs from £4 8s 9d. an hour to £3 13s.
3d. and labour costs from £2 17s. 2d. to 11s an hour. The total
saving in addition to higher output is £123 per 40 hour week. This
particular line needed 110 square feet of floor space less than the
system it replaced.
Only two operators are required on the transfer machine one loading
and one unloading. And the progress of every component through the
13 different processes is traced and checked on control panels
which are a blaze of red and green lights. To speed the supply of
transfer machines, Austin's have built their own machine tool
department. More impressive plant is also being designed, one
machine can now take the place of 25 others.
Austin's have helped to produce for BMC, three transfer machines
which carry out all but 20 of 100 major processes in manufacturing
a cylinder block. The machines are controlled by an electronic "
brain " and turn out a virtually finished block every 3.25
minutes.
Mr F Griffiths Austin's chief production development engineer, has
given this forecast of the future: "The transfer machine will take
in the raw material at one end cast it or forge it, machine it and
deliver the finished component either to the assembly point or
ready painted and packed for despatch.