"Selling Time:" Invest Cast 3
3-D printed investment casting patterns
Investment casting has historically been a long, drawn-out affair, and a very costly one too. The methodology requires custom-making a tool, or die, to form a wax model of the piece you want to produce – an expensive and time-consuming process. Prototyping for investment casting was equally troublesome. "In the past, customers had to find a service bureau [or contract manufacturer] to get a pattern made at great expense," explained Bill Walker, President of Invest Cast Inc., specialists in production quality prototypes and volume production metal investment casting headquartered in Minneapolis. "Then you’d have to beg a foundry to deal with this one- or two- or three-off sample." Even if you could find a company to produce them, the resulting castings were often prone to being set aside due to the very low volume. "Usually the lead time for getting a tool built is anywhere from four to eight weeks," Walker said. "Then you might find out you need to change it after your sample run." That could mean even more time and money.
An investment casting shell formed around a 3-D printed wax pattern - it's then heated to melt the... [+] model material away, leaving a void to pour the metal part
Walker knows all this firsthand. His father, Bill Sr., started Invest Cast in 1981 with a single plant in Minneapolis. Bill Sr. retired in 2011, at which time Bill Jr. and his two brothers bought two more facilities, in Wisconsin and Texas. In 1998, Walker decided to play around with a new technology: 3-D printing. He ran into immediate trouble with his business partner – his father. "After many arguments, he allowed me to purchase the equipment and sell the patterns to the business," said Walker. "I invested everything I’d ever saved - $50,000. I spent our entire savings on this equipment and began printing prototypes." He bought the Thermojet printer from 3D Systems, which was designed to make wax-based 3-D pieces for design, concept validation, or demonstrations. Walker realized that the wax print material meant he could immediately print investment cast prototypes without the need for the initial die – models that could take the place of the wax molds that were the basis of the investment casting process, saving weeks of work. "My initial idea was to send a casting along with a quote to the customer, in order to enhance sales," Walker explained. "We had had contact with over 2,000 customers, and I sent out postcards advertising prototypes in days rather than weeks to introduce the concept. The phone just started ringing and it has yet to stop!"
Pouring the metal for the final part into the mold
Invest Cast was one of the first foundries to bring prototyping in-house. The business took off immediately. Four months after purchasing the original Thermojet printer, Walker bought a second one. Not long after, he invested in a 3D Systems Select Laser Sintering (SLS) printer, which supported a much larger build platform, increasing the range of part sizes Invest Cast could offer. It uses polystyrene rather than wax, which was a cheaper material at the time. Invest Cast continued to add printers as the business grew, and they’re now running seven of them, along with two new ProJet MJP 2500 IC printers. The business is up to $30 million in sales overall, and Walker foresees it growing to more than $50 million in coming years. Prototypes account for up to half of sales at the Minneapolis facility each month, with that part of the business growing rapidly.
Walker sees a strong future for the technology. "The new wax printers are incredibly accurate and highly detailed, which is what I – and our customers – like about them," he said. "If we could drive the cost of the materials down, I could picture that rather than having rooms full of tooling, there’d simply be a data center that holds all your three-dimensional files. You’d pull up the data files as you need them, and have the printers run and make production patterns. That's where I think the potential is."
A room full of investment casting shells
That being said, Walker is realistic, offering that the technology still has a long way to go for most production applications. "For very small detailed parts, where you can get 20 or 30 patterns on a build platform, it's ready to go right now – it's feasible to do that as we speak, right now, in a low-volume scenario." But for larger parts and high volumes, production printing is still a long way off.
But that being said, modern prototyping with 3-D printers gives near-production capabilities as far as the quality of the parts themselves. For example, one of Invest Cast's customers makes nail guns. "I can give them a new design, a new housing, in three or four days," said Walker. "It allows them to test the product by putting the product in the carpenter's hands for a brief period of time. And a lot of times they’ll order many variations of a current design, and after testing it allows them to pick the best-performing product before they invest $3 million into their die-cast tooling to go into full production."
3-D printing is also excellent for singular custom applications of high value. "A large aerospace company had a one-off project years ago where we built some custom clips to hang a thermal blanket around a fuel cell so they wouldn't have to remove the rocket-powered vehicle off the launch pad in bad weather," Walker explained.
Invest Cast will keep the focus of their 3-D printing applications on where they’ve had lasting success, however: prototyping. It's there where Walker sees continuing benefits for his customers, in the weeks he can save a customer versus old prototyping methods. "That part of the business, I’ve always referred to it as ‘selling time,’ if you will."