By Cindy Macdonald, associate editor
"Our rule of thumb is that every dollar spent on rapid prototyping ... yields approximately $10 in cost savings and revenue gains," says John K. Lawson, senior vice-president of engineering, technolog...
“Our rule of thumb is that every dollar spent on rapid prototyping … yields approximately $10 in cost savings and revenue gains,” says John K. Lawson, senior vice-president of engineering, technology and human resources at Deere & Company (Moline, IL). He told attendees at last year’s SME Rapid Prototyping and Manufacturing Conference that Deere is using design tools such as rapid prototyping to improve functionality and quality in its products, while reducing cycle times and costs.
So are many Canadian design firms and manufacturers.
“We’ve seen an increase in the use of rapid prototyping,” reports Rick Figueiredo, a partner in Rapid Prototypes Inc. (Woodbridge, Ont.). “The market is more educated and aware. It’s an easier sell, and it’s not just the big companies using it.”
Most of RPI’s customer base is automotive, and the prototypes are generally used for concept modelling and early visualization. The service bureau has a Stratasys Fused Deposition Modelling (FDM) machine, which extrudes resin in thin layers to form a part.
“Customers like the fact that the prototype can be made in ABS because the properties are similar to what the final part will be,” says Figueiredo.
GET IT RIGHT THE FIRST TIME
“The best way to speed up product development is to get it right the first time,” says John Cherry, site director for Compression/Percept Design Inc. (Waterloo, Ont.). “It’s the loop backs and second iterations that really slow things up. Using prototypes, you may in some case have to do more work during the CAD design phase, but usually it keeps the project going in straight lines.”
“The time that it takes to create a functional prototype is the key. You need parts for inspection and testing,” explains Millan Yeung, group leader, Shape Transfer Processes Group, National Research Council’s Integrated Manufacturing Technologies Institute (London, Ont.).
With the tools available for rapid product design, says Yeung, designers can get to the functional prototype more quickly, and can feel free to make revisions and improvements at that stage because a new round of prototypes and tooling takes only days. “I can see how prototype tooling really helps speed product development. Designers can have tooling within a week, and it won’t cost an arm and a leg.”
Compression/Percept Design is a frequent user of rapid prototyping technology. The design firm employs stereolithography (SLA), selective laser sintering (SLS) and urethane casting in RTV molds. “A lot of our jobs involve taking a concept right through to the toolable 3-D CAD file,” says Cherry. “As we are refining the design, we often turn to an SLA model.”
The majority of Compression/Percept’s recent workload has been electronics and wireless communications devices. In one recent project, prototypes were used to help the design team and the client assess the appropriate depth and size for finger grooves in an electronic device.
“It’s as if the high-tech companies have reached a certain point with their technical attributes, and now they want to step up the visual appeal,” he says.
“The prototypes are really for the client. We use SLA in the early stages to assess form and fit, and aesthetics, so the client knows what the end product will look like. In the later stages, we’ll often put circuit boards and keypads into the prototype.”
Cherry comments that the SLA material is somewhat brittle for functional prototypes; Compression/Percept turns to nylon SLS parts to make more durable prototypes. Both of these processes are attractive, from a cost perspective, for one to three parts, he says. If more parts are needed, they output a master in SLA, then cast a rubber tool and inject urethane to make parts. The prototyping is done at Compression/Percept’s California bureau.
“Urethane is more attractive on a cost per/part basis when you need ten to 15 parts,” says Cherry. The material has comparable properties to ABS, can be tinted to different colors, and is often used for parts that are undergoing field trials.
TAKE YOUR PROTOTYPE TO THE WEEKLY MEETING
Hetherington Welch Design Ltd. (Richmond Hill, Ont.) is another industrial design firm that makes extensive use of prototypes. “It’s an integral part of our design development process,” says Scott Grant, a partner in the firm and member of the Association of Chartered Industrial Designers of Ontario. “We request a stereolithography model about once a week. We have weekly meetings with the client, and have the SLA part there to discuss it. Clients love them.”
He says marketing representatives will often run off with the prototype to show it to clients, or have a digital camera at the meeting to e-mail photos immediately. “People want to be kept in the loop and informed every day,” he says.
Having a physical part is also a benefit with non-CAD literate clients. “Scale is a little irrelevant in a computer image. Having the part in your hands puts things in perspective. People have become preoccupied with infinitesimal detail because CAD allows us to do that. The prototype injects a little reality back into the process.”
“The downside is that SLA parts we give to clients often come back in a thousand pieces, and sometimes this worries them,” says Grant. The designer has to reassure clients the SLA material is not representative of final part properties.
Once the design is agreed upon, Hetherington Welch designers will often have a prototype produced by CNC machining. Many of the firm’s current projects are security systems and associated electronic devices, so it is important to have functional prototypes for impact testing, static dissipation tests, pull testing (relating to wire installation) and installation assessments.
Grant says it is also useful to have prototypes when discussing mold design with moldmakers, and production issues with molders.
CANADIANS MAKE STRIDES IN RAPID TOOLING
Size limitations that have plagued rapid prototyping and rapid tooling are being challenged by a proprietary technology developed by Advantage Engineering (Oldcastle, Ont.). The company casts an alloy around a pattern to create a mold suitable for injection molding. “We have no size restrictions on this process,” explains Matthew Reid, vice-president of business development. “We built our own casting furnace so that we are not limited by furnace size either.”
“There’s a lot of interest in our ART tooling process, because it allows you to shoot production-intent resins and part volume can be in the hundreds.” On larger molds, says Reid, ART tools can be produced in less than half the time of a conventional mold.
Using ART, Advantage is able to create tools for fascia and interior automotive panels.
Moldmakers sometimes turn to Advantage for an ART tool when they can’t meet tool build deadlines, says Reid. The low-volume tool can be built and turning out parts (for shows or testing) while the production tool is still being built.
Yeung and his team at IMTI have been exploring rapid prototyping since 1989, and have a number of innovations to their credit. They pushed the limits of DTM’s RapidSteel process and built the largest tool ever created with that method. A collaborative project with Siemens, the tool weighs 100 lb.
IMTI has also developed its own process for quickly creating low-volume production tools. A nickel or copper coating is deposited onto a polymeric mold made from any type of rapid prototying system; IMTI uses its stereolithography (SLA) units from 3D Systems (Valencia, CA). Metal coated tools can be used as inserts for injection molding, or as electrodes for EDM. The process is suitable for molding up to about 50 parts of most resins, up to and including ABS and polycarbonate. Fabrication time for a typical mold is about one week and cost is usually under $10,000.
For medium- to high-volume production tools, IMTI uses a similar metallization technology to create a thick nickel shell from a rapid prototyped model of the mold’s obverse. The shell is back supported by metal-filled epoxy. Cooling channels or other elements can be imbedded. Yeung estim
ates the mold is durable enough to mold 5000 to 10,000 parts.
Another rapid tooling method for medium- to high-volume tools being developed at IMTI is rapid precision casting. The process involves vacuum-assisted investment casting of tool steels. It provides a high level of precision. The surface finish is excellent and requires little polishing.
TOOLS OF THE TRADE
Advances in materials for prototyping are one area that could spur even more use of the technology, and expand the applications.
3D Systems is releasing this month a “next-generation durable material” with polypropylene-like properties. The company predicts this material will substantially reduce the product development cycle by offering end-use properties right out of the SLA machine.
Several new Parts-in-Minutes polyurethanes that cure quickly and offer a unique combination of high impact strength, flexural modulus and heat deflection temperature are now available from Ciba Specialty Chemicals Corp. (East Lansing, MI). The RP 6486 R/H grades are suitable for casting tough, durable prototypes or short-run functional parts with performance characteristics similar to polyethylene, polypropylene or other polyolefins.
Ciba has also made available in North America Cast-IT 2000 epoxy, a castable material with the strength, high glass transition temperature and good thermal properties needed for injection molds. The epoxy system has good fluidity for pouring over the master model, and produces a high quality surface that can be polished to achieve a metal-like finish.
The newest rapid prototyping system from Stratasys Inc. (Eden Prairie, MN) has a build envelope of 10 x 10 x 16 in., and incorporates WaterWorks, the support system that dissolves when immersed in a water-based solution. The FDM3000 can build models in a variety of materials: ABS, high-impact ABS, elastomer and investment casting wax.
WHEN PROTOTYPING BECOMES MANUFACTURING
At the other end of the spectrum from near-production prototypes are concept models that can now be created in hours by 3D printers, such as 3D Systems’ ThermoJet solid object printer and Stratasys’ Genisys Xs.
The Genisys Xs is quiet, small and light enough to be set on a desk. As it becomes quicker and less costly to produce one-off parts with this technology, the realm of personal manufacturing is on the horizon. “With future generations of the ThermoJet printer, users could easily custom-design and print a chess set or a toy, create a model of a new invention, or download a file from the Internet to print out a replacement for a broken plastic appliance part,” says Mervyn Redgley, director of product management for 3D Systems. “That’s when we enter the realm of personal manufacturing.”
Solid object printers can also be used as a “3D fax” to receive files from other cities or continents, for output within hours as a solid model. This is especially valuable for global projects that must operate in a multi-national, multi-cultural environment.
KEEP THE CLIENTS HAPPY
“Clients are definitely a lot happier when products are designed in a digital environment, with prototypes,” says Grant of Hetherington Welch. “The tangible benefits are that we educate our clients much more and that we have more physical samples to test for assembly issues, etc.
“We still use tools as simple as foam blocks — sanded, filed and glued — to make prototypes at the early conceptual stages. It’s less technological, but the sooner we can put form to ideas, the sooner we can capture the imagination of the client and keep the project directed.”