On the Right Path - A Case Study

Despite the simple functionality of small electrical connectors made from plastic, the tooling used to injection mold such parts is highly complex and often costly. However, following the recent installation of a Pathtrace EdgeCAM off-line programming system, The Alan Group (Sussex, Great Britain), a specialist tool and moldmaker, has been able to streamline its production of electrodes and multi-cavity molds.

Supplied by Pathtrace Engineering Systems (Southfield, MI), EdgeCAM now is used to program. The Alan Group's vertical machining centers. As a result, this allowed program preparation to be reduced by up to 50 percent and reduced some six-hour machining cycles to just two hours. In addition, now the company can take on highly complex machining tasks that it could not have handled before.

The Alan Group is comprised of four companies and is acknowledged as one of Europe's leading plastics engineering and injection molding specialists. Almost 80 percent of its tool and component production is directly exported.

Two of the companies in the group are FineMoulds and Alan Grinders. The latter employs 55 people and has particular expertise in the production of tools and molds for small electrical and electronic connectors used in computers and tele-phones. FineMoulds produces injection molded parts for a wide range of customers.

The design and manufacture of injection mold tooling for plastics connectors can be extremely complicated - with many of the forms, profiles and angles required on these small components being particularly intricate. Tolerances are as tight as five microns and the complete multi-impression tooling - which can have up to eight cavities - must be capable of consistent production of millions of parts.

Virtually all of the connectors produced have pins or slots arranged to enable the physical connection to be made. This means the injection molding of such slender features - on parts as small as 12 mm x 3 mm - requires very sophisticated tooling with high attention to detail.

The Alan Grinders operation has built up considerable expertise in this area during the last 25 years by combining the skill of its designers and toolmakers with the latest technology in the form of 3-D CAD, CNC wire and solid sink erosion. It also has progressed in the use of both high-speed and hard metal machining techniques.

EdgeCAM is used to program two vertical machining centers: Mikron WF 31D and BostoMatic 32GS. These are used to produce a wide range of electrodes, bolster plates, inserts, cavities and various parts for gates and runner systems. Compared with manual data input routines, through the use of macro canned cycles at the machine control, EdgeCAM already has cut programming time by up to 50 percent on complex ejector plate work, and by approximately one-third on a number of insert plates and certain styles of electrodes.

In addition, EdgeCAM enabled the company to accept more complex tooling assignments - such as the machining of intricate pitched electrodes used for the progressive erosion of fine features. One such tool, which looks like a thick comb with offset teeth, involves machining 60 slender upstands from a solid 20 mm x 30 mm x 300 mm long copper block.

Each upstand is extremely fine, being just 0.4 mm in diameter. The machining over its 16 mm length has to be accurate to within 0.01 mm. Prior to the installation of EdgeCAM, the electrode would have been progressively built-up from separate elements. Now, the entire tool can be programmed in just 60 minutes using EdgeCAM's step and repeat area clearance routines, which fully support islands. The complete machining cycle takes four hours on the BostoMatic.

The machining of complex, copper runner electrodes on a vertical machining center also has been optimized through EdgeCAM, and now takes around two hours versus the five or six hours it took when they were previously ground using expensive rotary wheel dressers to generate the stubby, truncated gear tooth form geometry.

By hard metal machining at spindle speeds of 16,000 revs/min, small parts such as cores for mold gates can be completely roughed out prior to finish machining using the solid sink vertical EDM. This revised dual operation process is far quicker and more economical than the many hours previously allowed for eroding the complete cavity.

Not only is the software used on tool and mold production, but EdgeCAM also has opened other subcontract machining opportunities. Alan Grinders is attracting business now from the Formula 1 motor racing sector. In fact, it was one such motor sport component that helped convince Alan Grinders that EdgeCAM was the best programming system for the type of work it now undertakes.

Initially, Alan Grinders shortlisted four CAM systems from which two suppliers were asked to provide demonstrations. "It seemed logical to use the F1 component for the evaluation process," says CNC programmer Glen Fowler. "This particular fuel system component had a 50 mm2 bell-shaped housing, which involved machining complex 3-D profiles along with quite intricate internal filets, radii and chamfers. If I manually programmed this job, it would have taken me the best part of a week," he says.

While both CAM systems produced a program for this job, the speed and simplicity of EdgeCAM impressed them. Glen Fowler continues, "EdgeCAM created the basic model in a little more than five minutes and the complete program was up and ready to run within the hour."

An additional benefit of EdgeCAM allowed Alan Grinders to move into larger areas of mold work that it could not have tackled before. One example is the production of a 32-impression cavity block for the handle of a new disposal razor. "We just could not have machined this size and complexity of mold without EdgeCAM," explains Dave Mackinnon, the company's other main programmer.

Machining the razor mold involves considerable 3-D profiling on a tapered form and the production of finely detailed rib lines on the curved sides. "All-in-all, there were more than 2,000 different surfaces to be generated on one half of the mold," he explains.

"With EdgeCAM we were able to produce the complete program for machining the 32-impression razor handle mold in less than five days."