Simple Solutions That Work! Issue 13

DEFECT PREVENTION 39 3D PRINTING O ne of the most commonly heard reasons that foundries have put off adopting 3D printing, in any format, is the misperception that “it doesn’t work.” Well, this misperception is sort of like running around barefoot, swinging a tree branch and declaring that footwear doesn’t work either. You don’t want to wear super insulated duck boots for a summer marathon run, and you can’t reliably wear stiletto heels while fishing for striped bass on a jetty. You have to run the right printing process, use the right kind of materials, and use all the right settings to get defect free castings out of any process. Doing a little up- front simulation work to make sure the casting and rigging are set up right before you even start picking a 3D printing process is an even better idea. Continued on next page WILLIAM SHAMBLEY President NEW ENGLAND FOUNDRY TECHNOLOGIES ARTICLE TAKEAWAYS: • Expanded design freedom doesn’t fix bad geometry • You’ll have the least defects if you adopt the 3D printing process that fits most directly into your existing foundry process • The wrong materials selection can lead to defects every time • Not all applications will require the same settings, even on the same printer and materials So here’s 4 rules of thumb to help you prevent defects when using 3D printing in your foundry: 1. Know your casting - good casting design is good 3D printing casting design. Expanded design freedom doesn’t magically fix bad geometry. Take time to run a naked simulation of the casting before you design the tooling to analyze for predicted shrinkage or porosity defects. Tools like SOLIDCast exist substantially to help us understand our castings better and prevent all manners of defects right at the outset. Use 3D printing to build rigging for all kinds of interesting solutions after you’ve decided where the problems are. 2. Match your processes - the various 3D printing processes match up better to some casting processes than others. These days, there are mountains of information available from the AFS, manufacturers of 3D printing systems, universities, service providers, etc. There are charts to help you decide which process to use based on part complexity, number of parts in a run, existence of tooling, and part size. To keep it really simple, try this: What process fits into your daily operation? If you blow cores, you can use core boxes printed out of plastic or metal. Investment casting? You can print waxes on several printers, based on your surface finish, ash, shell and speed requirements. Ramming green sand, no-bake, etc. with hand or machine? Yes, you can 3D print plastic or metal tooling on a variety of systems – some with more hand work than others. Or print sand cores. Or synthetic sand cores. Or print molds. You’ll have the least defects if you adopt the 3D printing process that fits most directly into your existing foundry process. Unless you’re really ready to take a leap forward. Then go with something like the SLM Solutions equipment and print fully dense metal parts directly from CAD.