K. David Howard is with Ford's Powertrain Operations in Livonia, Michigan. His title is Model Methods Analyst, Advanced CAD/CAM, Applications & Free Form Fabrication Services. A deconstruction of that title tells us that he, among other things, analyzes models and is involved in advanced computer-driven design and manufacturing techniques. Then it gets a bit trickier. Until he starts talking about what is clearly his passion: rapid prototyping technology. When you start with a vat of polymer or sheets of specially treated paper or powdered metal or plastic and end up creating solid-to-the-touch models of components, then it is clear that the subject is free-form fabrication.
Howard has spent much of his time during the past several years working in Ford's Advanced Manufacturing Center (Redford, MI), where over the years Ford engineers have been working to advance the state of automotive manufacturing technologies. There, he and his colleagues have been working with an assortment of rapid prototyping equipment from virtually all of the major vendors.
According to Howard, the Advanced Manufacturing Center has been where much of the preliminary work that the auto maker performed with rapid prototyping technology; people were also trained at the site. Now the equipment is found throughout the organization, within plant sites, such as at the powertrain plant where he works.
A major benefit that he cites for the technology: "It allows us to verify what we are doing." And, equally important: "It helps us save tremendous amounts of time." And time, of course, is money.
Howard explains that one of the advantages of a solid-to-the-touch model over a solid model on a computer screen is the fact that it is tactile, physical, and a representation of what they are thinking about making. He says that a cross functional team can get together in a conference room with a rapid prototyping-produced model and determine whether that is what they have in mind. "This way, problems get solved up front," he notes. And once a determination that the design is a go, then the model can, say, be given to a die maker. "The die maker can't use it to make a die for us," Howard says, "but because they have it in their hand and can look at it, they can quickly determine where the parting lines will be and how much steel they will need to make it. The timing is greatly compressed."
The Explorer Project
One tangible example of where rapid prototyping was a huge advantage to Ford was in the development of a component for the Ford Explorer, the world's top-selling sport utility vehicle. The need was to develop a transfer case housing for an existing 5.0-liter V8 engine. That power plant develops 210 hp at 4,400 rpm. It is available with an all-wheel-drive system. The Explorer was (and is) available with 4.0-liter engines. The 5.0-liter was an option that Ford wanted to offer. According to Howard, after a month's time, when the design for the case was firmed up, models of the transfer case were generated on rapid prototyping equipment. The models were fairly transparent. During a group assessment of the design, one of the people held a model up to the light and saw a feature that required fixing. So they called in the design personnel. "Twenty-four hours later, it was fixed," Howard says. "Otherwise, it wouldn't have been caught before it cost us a considerable amount of money."
Howard says that the use of rapid prototyping for the transfer case developed helped Ford bring the 5.0-liter option to market 13 months earlier than had been anticipated. That represents huge amounts of money in sales.
Another example: the development of a rocker arm for a high-output, 302-engine. A print of the rocker arm was given to five companies for quote. Four of the five responded with bids ranging from $1.10 to $1.20 a piece. Next, Ford engineers went back and made a computer solid model of the design—and found a problem that was fixed—and then made rapid prototype models that they sent out to the same five suppliers. Compared to their original quotes, the four companies reduced their price by 25%. And the fifth company, the one that didn't even make a bid, came in at 60 cents.
One of the capabilities that Howard is looking forward to is to go from the model straight to molds for die casting. The present hold up: "We need tolerances of ±0.001 in. for die casting. The rapid prototyping equipment provides a tolerance of ±0.0035 in. right now," Howard says, adding, "People can use it now for creating die casting dies—but not ones that Ford wants to use."
Rapid Prototyping Tips (Sidebar)
Chances are, you might need to avail yourself of the services of rapid prototyping contract shop. So to get an idea of what it is that you might want to look for, we talked with Alan R. Peterson, vice president, 3-Dimensional Services (Rochester Hills, Michigan). 3-Dimensional Services has been in the rapid proto-typing business since 1992. The personnel there use, or are familiar with, all of the major systems. Here are some of the things that Peterson suggests.
Do More With Your Data. Often the process starts with a part drawing. So the contract firm turns the 2D information into 3D information ("We like to do this in solids," Peterson says), then creates an .STL file that is used to run the rapid prototyping machine. Then it is onto making the model. Peterson suggests that the physical model that's created shouldn't simply be the object of the exercise. Yes, it is important to have one for design verification. But he notes that the information generated can be used for finite element analysis for testing, or as a source for the tooling supplier. What's more, there have been cases where the rapid prototype models are used for system testing, actually standing in for a conventionally manufactured part.
Know the Costs. "There is no rule of thumb when it comes to pricing," Peterson says. "We competitively quote with many companies all of the time. I've seen quotes range 400% from the highest to the lowest." He suggests that you check the service offerings made by the vendor. For example: will the rapid prototyping source just make a part, or will it perform the quality control checks and finishing, too?
In terms of the physical costs, Peterson says that the Z-height has the biggest effect on the cost. The taller it is, the more expensive it is. Another variable is the volume of material used. He notes that the polymer resin used in the company's three SLA machines from 3D Systems costs about $600. The paper material employed in the two Helisys laminated object manufacturing (LOM) systems they use costs $2.50 per pound. He translates that into a comparison wherein a gallon of resin is equal to 25 lb. of paper. (Does this mean that the economy-minded should insist on LOM? No, Peterson answers. Different types of systems have advantages for different types of parts.)
Timing? "Average-sized parts"—about the size of a breadbox—"take two to three days," Peterson says. "Complexity has nothing to do with it. Just Z-height."