affordable with a traditional pattern. According to Poweleit, with sand
printing, as with most other RP methods, designs are not geometri- cally constrained. “We like to say that anything you
can imagine, you can cast, but some- times making the tooling is a little bit more difficult,” Poweleit said. “Te neat thing about these techniques is there’s the freedom from having to create the tooling to get to that geometry.” Te enhanced design freedom is
Robotic sand machining technology can produce molds for large parts quickly and without invest- ment in tooling.
Introducing Customers to RP
Power transmission part-maker Baldor-Maska, Quebec, Canada, had a client that needed a three-week delivery on a nonstandard part, and it didn’t have an existing pattern. In a typical order, Baldor quotes for a pat- tern price, places a pattern order and waits two or three weeks to receive the pattern. After the pattern is delivered, Baldor sends it to the casting supplier to cast the component. “I know that some foundries or
patternmakers use polystyrene when they need a pattern and sample in a short delay,” said Jean Philippe Lefeb- vre, patternshop supervisor at Baldor. “But I didn’t have any relationships
with a foundry that used that technol- ogy, and I didn’t have time to find and contact one.” Instead, Baldor worked with existing supplier Fonderie Saguenay, Chicoutimi, Quebec, Canada, which employed its version of robotic sand machining to provide the part on time. In the process, a robot CNC machines the mold used to pour a part, skipping the time consuming patternmaking steps. According to Lefebvre, since Baldor
needed only one large part and it did not have an existing pattern, using a rapid process made sense. Plus, machin- ing the sand mold allowed for certain design enhancements not possible or
WHICH METHOD SHOULD YOU OFFER?
The most established rapid prototyping methods, such as stereolithography (SLA) and selective laser sintering, often are matched up with the investment casting process. While some small tweaks to the process may be required, many companies find it simple to incorporate the patterns. “Investment casters have done a good job of adopt- ing SLA patterns, and it’s a good way to go from a piece of plastic to a piece of metal,” said David Poweleit, application engineer for the American Metalcasting Consortium. Additive manufactured patterns typically are most cost- effective with smaller pieces, although they can be assem- bled together to produce larger parts. Other RP methods that are better equipped for larger parts have been developed, such as robotically machining sand molds or printing sand molds layer by layer, without first creating a pattern. Sand molds produced via 3-D printing can be a good
42 | MODERN CASTING May 2012
match for small runs of larger parts or for producing multiple small parts at a time. It is not uncommon for sand printing machines to handle quantities up to 200 parts, if they are small enough.
While machining sand molds wouldn’t make economic sense for a long production run, the process can be used to prove out the design before investing in permanent tooling. According to Reg Gustafson, project manager for Clinken- beard & Associates, Rockford, Ill., tooling-less processes eliminate the need to store tooling and provide the opportunity to start up new part numbers faster and run parts in multiple locations, making spare parts on demand and onsite. “Tooling-less methods, such as machining molds and cores, provide a faster and less expensive way to make prototype sand castings with less capital investment in tool- ing,” Gustafson said.
particularly important on one- or two- run orders when tooling for extended production will not be required. Baldor’s first look at sand machined molds has convinced the company to consider rapid manufacturing for future power transmission projects. “If we have rush orders, it’s sure
we will consider [rapid sand mold machining] again, especially for the ‘one-shot deal,’” Lefebvre said. “We don’t use rapid casting on a regular basis, but it would be useful when a customer has an unpredictable request because of a breakdown.”
ONLINE RESOURCE
For an additional article on rapid manu- facturing or prototyping methods, visit
moderncasting.com.
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