From the by Graham Montgomerk 0/ /7 Yoj /f)to ?C a I
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There's a terrific draughtsman in here says Edbro's technical director. He's talking about computer-aided design and how his company benefits from it
COMPUTERS have become very much part of our daily lives, even if we are only aware of them when told that we have received the wrong gas bill because of "computer error."
In the engineering world, computers are taken very seriously indeed; they are invaluable in the number-crunching exercises which used to take hours and now take minutes.
The latest use of the computer is in computer-aided design and computer-aided manufacture, or Cadcam for short. Before any operator gets nervous that his latest 38-tonne pride and joy has been designed solely by computer, the message is: don't worry. The emphasis here is on computer-aided.
Edbro in Bolton has recently installed a Cadcam system to speed up its drawing office work and to take a lot of the routine time-consuming tasks out of the basic design process.
Edbro started to evaluate Cadcam in November 1981. The company had been trying to rationalise for some time, but the proliferation of chassis variants was against this. The recession had led to a cutback in staff at Edbro so, in effect, what was required was increased productivity from the drawing office.
Computers had been in use at Edbro for some time but they were desk-top computers for calculations and mainframe in conjunction with universities for stressing. On the production side, the desk-top computers were used for preparing numerical control tapes.
John Worton-Griffiths, Edbro's technical director, decided that training courses in Cadcam were too long and so he looked around for an independent ad viser who, however, had no brief to recommend any particular system. The selected consultant came once a week for the first two months to help Edbro study the various systems available. A vigorous evaluation procedure saw the list of systems whittled down from 70 (1) to 12, and finally down to four.
A written specification of the Edbro requirements was then sent to each of these four cornpanies.
Government support is available to companies who, like Edbro, want to expand their operation. But this grant has to be justified on a commercial basis before any help is forthcoming. The support is one third of the cost of "certain investments in computer-aided design, computer-aided manufacture and computer-aided testing." It specifically excludes production equipment.
There are limits to the total amount of money available anc there is also a proviso that nc company will qualify for such E grant if it has already started or a Cadcam project.
Following Governmental ap proval, the Edbro board madE the decision to go ahead anc purchase a system from the UN company Cambridge Interactive Systems (CIS), who were subsequently taken over by the American company Computervision, The Edbro system is a mixture ol nationalities — UK software and a French plotter for example — and as such Edbro had to de. dare to the Government the origins of all the hardware and software.
The whole system has widet connotations than just design, and will eventually be used in sales and marketing as well. It was for this reason that Edbro ordered the CIS system as a "starter," which could be added to in the future.
The company will not disclose how much it spent in starting on the Cadcam path, but it admitted that the system purchased was in the "medium category."
In the computer industry "small" refers to a system costing up to £100,000, "medium" covers the £100,000 to £250,000 sector, while, at the top end of the scale, "large" (otherwise known as "aircraft spec") means anything over the quarter million mark.
The essence of computeraided design is that as much of the routine work as possible is taken out of the draughtsmen's hands. Current Cad systems are as near to the draughtsman's own pencil as possible but do not take away his individuality as a designer.
Information from past experience in tipping gear (now called "hoists" at Edbro), bodywork, pumps and so on is all stored in the computer along with the specifications of chassis in current production.
As far as the latter are concerned, some manufacturers are more detailed than others in the sense that these companies operate similar systems and are thus able to supply the input direct in the form of floppy discs which saves Edbro having to programme every new model into its computer. It is here that having software systems which can "talk" to one another is a tremendous advantage.
As can be seen in the accompanying photograph, the draughtsman has a joystick type of control and also a "puck." The latter is centred (by means of cross-wires) above the pre-programmed command on the chart. The drawing's lines are put on the screen using the joystick. I hate to draw a comparison with "Space Invaders" but there is a certain similarity!
Previously every chassis had to be detail:Arawn by hand, a practice Edbro discontinued in the mid-Seventies — because it could not cope with the number of drawings — by moving to standard drawings not-to-scale. Having now an extensive range of chassis stored in the computer, Edbro can go back to oneoffs properly detail-drawn to scale.
To see the Cad system "draw" a chassis from its memory bank is a fascinating experience. The Mercedes-Benz chassis, complete with body, was drawn and displayed on the screen in seconds, with a print-out available if required. Some of the more up-to-date chassis builders provide Edbro with the software in such detail as to show fuel tanks, air tanks and pipework.
Edbro stresses that there is still plenty of scope for design flair — and in cases like this it is necessary to distinguish between draughtsmen and design draughtsmen. John WortonGriffiths suggests that "the guy will still sit down and get the basic design thought out well before he presses a button."
Although the chassis manufacturers — and Edbro itself — are building up information in the memory banks on current and future designs, one problem is how many of the old designs should the memory hold. With the number of designs Edbro has produced in the past, this is a large problem.
The saving in effective manpower through using Cadcam is tremendous. If Edbro receives a request for a body or a hoist, the computer will search its memory (in seconds) to see if a similar design has been made in the past. Even if the identical component has not been produced, it might be able to come up with something which could be used as a basis.
This saves relying on the draughtsman's memory and saves somebody leafing through drawing office records. Having decided that such a component is already on record, a press of a button will display the drawing on the screen.
If an operator asks for a body and gear which is incompatible with his choice of chassis — be it related to bodylength, axle loading or whatever — then the computer is self-checking and will produce a graphical representation of what could go wrong. This obviously saves Edbro a lot of time in drawing and calculation to demonstrate that the chosen specification is impossible.
The Cadcam system draws to metric dimensions. It can reproduce a component in three dimensions, and can also come up with a sectioned drawing through the same component. There is nothing here that a draughtsman cannot do — it is just that the computer-based system does it so much more quickly.
The other aspect to be considered is the Cam side of Cadcam. This means computer-aided manufacture and is an area in which British industry is being encouraged to invest. Edbro sees it as being an integral part of the company's future, for it will bring design and manufacture closer together with the aim being a better product at a lower cost in a shorter time.
Edbro is going to use Cam to produce a computer model of the component which can be used by the production engineers to produce the NC tapes. Currently, 50 per cent of this design time is spent in putting the drawing up on the screen. Although the computer can do this in a fraction of the normal time, it cannot remove the stage altogether as the production engineer needs to incorporate the tool paths for the particular machine that will be used in producing the component.
Investing in a Cadcam system is not for the faint hearted; as well as being expensive it can also bring labour problems in its wake. There is no doubt, however, that such systems can take a tremendous amount of drudgery out of the drawing office and allow a company to become more efficient.