The speed with which prototypes are being made these days is fueling interest in making production molds the same way. And early returns indicate successes could be near. ``We're after a prototype-speed process that can run the first 1,000 parts, but also has the potential of running high volume,'' said Andrew Santin, president of family-owned Santin Engineering Inc. of Newton, Mass.
Santin Engineering, which makes prototypes and models, is part of a consortium developing technologies to bring products to market more quickly. Santin refers to rapid production mold making as ``the next phase'' in the consortium's schedule.
``That's our ultimate goal, but we're working now on the customer who needs the 1,000 parts. We're looking at time and large expense savings,'' he said in a June 16 telephone interview.
The consortium includes Pitney Bowes Inc. of Stamford, Conn.; 3D Systems Inc. of Valencia, Calif.; Cemcom Corp. of Baltimore; and Glastic Corp. of Cleveland. Members are making their contributions at cost, with Pitney Bowes' funding, Santin said.
``It's a very open group. We're not secretive because we think if we have a viable process we all can benefit from it. There's nothing new, we're just pulling things together and being innovative about it,'' he said.
Santin said stereolithography has improved in its accuracy and surface finish, and nowadays tools can be cast off stereolithography parts for production of what he called ``a decent injection mold.''
The consortium has built a number of tools by putting a nickel skin, or shell, on a stereolithography part, he said.
``The aim is to form a relatively uniform wall of nickel, controllable in its hardness, with no shrink and with the exact surface detail we need that will stand up to the molding materi-als we want to try,'' Santin said.
He explained that the relatively thick nickel shell is backed with ceramic.
``A nickel-faced tool is a long-life tool. If it is done properly with integrity, it won't crack or degrade,'' he said.
``The next stage is nickel electroplating. We've produced one tool and we're about to produce our second. We can plate right on the [stereolithography] part, back it with ceramic and injection mold right into that tool,'' Santin said.
The consortium has been working on making injection molds with a Cemcom-developed process called chemically bonded ceramic. In one project, a 9,000-pound tool was built for prototyping a major thermoset component for a large Pitney Bowes mailing machine. The project's goal was to change the machine's largest metal part, which was die cast aluminum, to plastic.
The target was building the mold within six weeks after an stereolithography pattern was available at one-third the cost of conventional production tooling. When the consortium's total 20-week lead time project was accomplished in seven weeks, the group had proof it had a reliable system, Santin said.
The prototype part's tooling was made using a high-strength, chemically bonded ceramic material cast directly over a stereolithography part. The ceramic was cast in a standard steel mold frame from D-M-E Co. of Madison Heights, Mich., for a strong encasement for the chemically bonded ceramic material.
``The biggest advantage of ceramic is it provides us with a no-shrink condition. The ceramic can be tailored so that it shrinks zero, or a little bit, or even expands when it cures,'' he said.
``We take a [stereolitho-graphy] part and pour one side, flip it over and pour around [the part] again. But now we're also pouring up against the other ceramic side, so we're pouring our parting lines. Because we do not have shrink, we've got a net shape fit,'' he said.
``That's a problem you can't overcome with some of the processes like cast metal tooling. We didn't have to trim or anything to get it to fit together. We closed this 9,000-pound tool and started shooting.''