Prototyping plastic automotive interior components can be tough. On top of their functional needs, these parts usually have stringent cosmetic requirements that can rule out the use of rapid prototyping machines. And the most obvious alternative, injection molding the parts in the end-use plastic, can take too long and cost too much to satisfy automakers. Ortech Inc., which designs and manufactures remote keyless entry systems and locksets, recently discovered a quick, inexpensive way to get the molded prototypes it needs.
On recent projects the company has turned to molded prototypes from Protomold, whose Rapid Injection Molding service can transform solid CAD models into molded parts in as little as three days. In some ways, Protomold's system differs very little from traditional mold making and molding methods. The company uses high-speed CNC machines to cut aluminum core-and-cavity sets. And it uses conventional molding machines to produce parts in a full range of engineering plastics, either from its own stock or custom compounds supplied by its customers.
The real difference between Protomold and a traditional molding shop comes down to software. The company has developed its own web-based mold design system that gives it a big speed advantage. In a matter of hours, the software reviews a solid CAD model of a molded part and spits out a report that evaluates whether the part has the right size and shape for the rapid injection molding process. The same report, which is emailed to the customer, will also contain a detailed price quote.
Once a user does decide to pull the trigger and buy some parts, the company's software generates tool paths for the core-and-cavity set. At this point, about a day into the process, only a quick review by a human engineer stands between the CAD file and a cut tool. According to Brad Cleveland, Protomold's president and CEO, the standard turnaround time is 10-15 business days. For more money, Protomold will turn around the parts in as little as three days.
The process does have limitations with overall part and feature sizes (see sidebar). Yet in many cases, the process can make parts that are indistinguishable from the production parts. And in Ortech's case, the ability to get real molded parts makes a big difference. Brian Bolton, the company's product development manager, has tried "the whole gamut" of rapid prototyping systems and not found any that can both hold Ortech's dimensional tolerances and meet its cosmetic requirements-which can include color and texture matching plastic key and lock components to the rest of an automotive interior. "Even with prototypes, we can't give our customers something that looks like it was cobbled together with duct tape," he says.
Over the years, Bolton has come to believe that actual injection molding is the best way to prototype injection molded parts. "I liked the fact that we could get prototype parts from Protomold in the same kind of material as our production parts," he says. And that's not all he likes.
The speed of the system played a big role too. Bolton first used the Protomold service when working on new entry and ignition systems-keys, locks, and bezels-for the Saab sports utility vehicle. The key represented Ortech's first attempt to integrate both the remote keyless entry electronics and the ignition immobilizer transponder into the key head. Bolton recalls that Ortech had less than a year to develop the system.
A year may sound like a lot of time, but design revisions ate up a lot of it. Bolton recalls that General Motors, Saab's parent company and his direct customer, had asked Ortech to help develop a key quickly by using keyless entry electronics and a battery borrowed from earlier programs. In the past, these electronics had been packaged in a key fob, so Ortech engineers went about squeezing them within a two-piece PPE/PA key head, along with the transponder for the ignition immobilizer. It's not an easy repackaging job. "The location of the electronics is crucial," Bolton says, explaining that even a few thousands of an inch difference in the relative location of the electronics, battery, and key blade can determine how well the transponder ultimately couples with an antenna in the ignition lock.
Anatomy of a Key: Virtually all car keys today have some sort of electronics in them. These new ones developed by Ortech for a forthcoming Saab sports utility vehicle integrate both the remote key-less entry circuit board and a transponder for the ignition immobilizer.
Yet it was matters of form rather than function that ate up most of Ortech's development time. Bolton says that GM had already signed off on Ortech's solid models of the key head when Saab's styling department stepped in with some requirements of its own. The designers undoubtedly came up with a more attractive key, but they proposed some key head contours that would have prevented Ortech engineers from successfully packaging the electronics. After many design iterations and weeks of compromise, Saab's stylist and Ortech's engineers had a design that satisfied both teams. "The problem is that process ate up all of our slack time and then some," says Bolton. He estimates that all the design iterations left Ortech without good prototypes just three months shy of having to produce actual production parts. "All the waffling doesn't change the day when we have to put the parts on the loading dock," he says.
So he turned to Protomold "out of desperation" after determining that traditional tooling methods wouldn't be fast enough.
Real Parts in Days
And his decision paid off. Bolton started by uploading his solid CAD models into Protomold's web-based quoting system. "The upload process was simple," he notes. "And the system accepted our native Pro/E files, which is not the norm for us." A day later, Bolton checked his email and found an HTML report containing price quotes for tooling, set-up, and the parts themselves.
The report also included a design analysis that flagged areas of Ortech's parts that would not work with Protomold's process at that time. For example, Protomold's milling process leaves larger radii than that found on some features in Ortech's part model. And at the time, Protomold's process didn't support side action tools. "That was a problem for us since virtually all of our parts have some sort of undercut," he says. In this case, the snap-fit features that bring the key shell halves together need an undercut.
The report, however, made it pretty easy to identify those areas of the Protomold parts that would have to differ from the production design. Bolton gave the report high marks for how it used color and "an intelligent view" of the part model to graphically flag the problem areas. With the report in hand, Bolton decided that, for prototype purposes, he could live with the radii changes and do away with snap-fit features in favor of a glued assembly. So he placed an order and had real parts in hand just ten days after he started the process.
Contact Senior Editor Joseph Ogando at [email protected].
|//Check out the links below for more info//|
Information on Protomold or to register for the company's free Rapid Injection Molding Journal:
For a look at some sample reports from the company's automated design and quoting system:
For other rapid prototyping technology mentioned in the News section in this issue, go to page 40, or