Dramatically reduced lead times, massive reductions in scrap, the elimination of collisions and all engineering and production departments able to handle higher volumes of work with the same manpower may sound too good to be true. But that’s what manufacturers like IPE and Mayflower Aerospace are achieving, essentially by directly connecting engineering design systems to machines on the shop floor.
Although the biggest benefits of such CAD/CAM links to DNC (direct numerical control) machines will obviously be realised by companies manufacturing many different and even unique components, many others will also welcome the much greater flexibility that comes from, for example, faster job changes, greater accuracy and the rest. Further, by reducing the idle time that a component spends sitting on the shop floor, CAD/CAM integration is a useful additional enabler of lean manufacturing.
Traditionally, machining programs are developed by industrial engineers and machine operators – an approach that’s both time consuming and expensive. Since it’s also prone to human error, it involves several proving runs – itself expensive when one aerospace component can require up to 750 hours of machining – and still entails risk of scrap and machine damage.
At first sight, passing a program directly from CAD to the machine shop would appear to overcome some of these problems, but it’s not as easy as it sounds. 18 months’ work involving multiple technology vendors is par for the course – and that’s because there are several steps that are absolutely vital. First, for example, the design needs to be accurate in terms of size, scale and geometry. Human operators and engineers can add intelligence when they interpret drawings, but a directly connected machine will make exactly what the designer’s drawn – mistakes and all.
Next, a machining program needs to yield all the desired results – not just in terms of producing the finished part, but also avoiding expensive collisions. And finally, that program needs to be communicated to the machine. The preferred route should be a direct network link, but that’s not the sole goal. The benefits of CAD/CAM/machine integration flow not from the difference between carrying a memory card or disk to a machine on the shop floor, but from the ability to produce a program within a shorter space of time and, crucially, know it will work.
Time and confidence
And that’s really the most important point – having the confidence that the production program won’t result either in collisions that could cost tens of thousands to repair, or in scrapping a part that could represent similar value. Hence, every sophisticated manufacturer we speak to today agrees that CNC verification, using simulation technology, such as that from Vericut or Delmia, is a key link in the chain from drawing board to finished part.
At aircraft seat manufacturer IPE, engineering manager Brian Spalding says: “We run all our models through verification. We use Vericut – it tells us whether the program has any errors, and even creates a virtual video of the sequence of operations. This is a boon for operators, who can view it to know what to expect. Now, we very rarely need to use resin to check programs, which saves us a great deal of time.”
Sounds simple, but there are issues with implementing the technology for CAD/CAM integration, and it represents a significant cultural challenge for operators, engineers and management alike. “You have to get from the jobbing mentality of machine shop people to them believing that the system works and they’re now part of a production machining team,” says aerospace design-to-manufacture operation Mayflower Aerospace’s team leader for NC, Kevin Cutsforth.
Part of that is change, and part confidence. Because verification provides a full simulation of a machine, Mayflower decided this would be the best first step to deal with those head on. Says Cutsforth: “The first objective was to get a good piece of engineering on the machine – so we started out with VNC [Delmia Virtual NC simulation] first, so we knew that what we were getting to the machine was right. It’s gone down very well – we’ve proven that what’s good on VNC is good on the machine.”
Meanwhile, Vericut again is proving successful at an oil and gas equipment manufacturer that wished to remain nameless, as one of its Six Sigma 'black belts' explains. "Before, we would have to wade through programs and try to detect collisions: now we use Vericut, and we're aiming to give the operator a program that will produce the component right first time."
Hot agenda item
At its UK plant, around 50 shop floor machines – from small turning, to large boring machines – make equipment for sub-sea operations. "It's pretty much an engineer-to-order shop," says our contact, and his big issue here is integration to make the design-to-manufacture processes work faster and more smoothly. Currently, the firm uses separate CAD and CAM systems since, as he says, "There isn't really a single supplier that can provide a seamless CAD and CAM system as a turnkey system." Thus design engineers produce drawings and specifications for components on one system, and then industrial engineering works with CAM engineers to build the machine programs.
"It is now a hot agenda item to have seamless CAD to CAM and DNC integration," says our man. "Core benefits will include a reduction in the lead-time spent producing the engineering drawings. Our work is increasing, and we want to do 20–30% more with the same people. We are also looking to improve the efficiency of the people on the shop floor, and as components can cost £20–30,000 we must avoid scrap."
Returning to IPE, one of it’s key initiatives was to link its Pro-Engineer solid modelling package with Pathtrace’s EdgeCAM offline programming system. That was “initially customer-driven to cut lead times,” explains Spalding. “We can now just transfer Pro-Engineer models straight from CAD to CAM.”
But there’s more. The firm employs 222 people manufacturing aircrew seats for parent company IPECO, and provides a subcontract design-to-delivery manufacturing service to civil and defence aircraft customers such as British Aerospace, Alenia Marconi Systems and GEC. After the CAD to CAM transfer, there’s one more important step before programs are verified and sent to one of the two computers that provide the DNC link to shop floor machines.
“A post processor takes into consideration the age of the machine and the type of tooling to be used, then automatically adjusts the speeds and feeds accordingly,” explains Spalding. “This means all similar machines are compatible. For example, a vertical machining centre with a pallet is compatible with any other vertical machine having a pallet.”
As a result of that, with MRP automatically triggering a program download to generalised shop floor machines, only six inspection reports have been filed for scrap in the last year. “That is less than half a per cent, which is a massive improvement,” says Spalding. “Missing holes and chamfers are a thing of the past.” And there are clear advantages in terms of machine utilisation and plant flexibility and responsiveness.
Cost savings, like those that come from reduced proving runs and cast iron guarantees that there won't be collisions causing expensive downtime and repair bill, are significant. But there's a great deal more value to be had if you follow it through. Our oil and gas equipment manufacturer, for example, expects to be able to knock 30–50% off the five months or so lead time that today's design and engineering approach entails.
But you'll need to be prepared to work with several vendors and face a struggle winning over all parties. Time for a clear vision.
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