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September 1, 2001

5 Min Read
Reality check: PIM is not PIM

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Smith Metal Products proved that plastics injection molders can successfully move into powder injection molding when it won this year's metal injection molding Grand Prize at the Metal Powder Industry Federation's annual international conference and exhibition. The parts, molded for Intuitive Surgical (Mountain View, CA), are a 17-4 PH stainless steel needle driver and distal clevis for a robotic, minimally invasive endoscopic surgery system. Molding offered a 90 percent cost saving compared to CNC machining the parts from stock.

Why should plastics injection molders consider powder injection molding metals and ceramics? One who has successfully made the switch has a simple answer—higher profit margins. "In plastics, you're fighting for pennies, sometimes for tenths or hundredths of a cent. It's not a real fun market to be in any more," says Ron Carlson, division manager of Smith Metal Products (SMP, Lindstrom, MN). 

SMP is a division of Plastics Products Co., a successful plastics custom molding operation also based in Lindstrom. In addition to boosting the bottom line, Carlson says adding powder molding to its portfolio can help a plastics molder bring more value to existing customers while at the same time opening the door to a much larger customer base. 

However, even though plastics injection molding and powder injection molding share similar initials, that is basically where the similarity ends. In a presentation at the PIM 2001 international conference in Lake Buena Vista, FL earlier this year, Carlson discussed key issues molders should carefully evaluate before taking a powder on plastics. 

Regarding the cost of getting involved, Carlson says the capital investment is not necessarily too high—not initially, that is. "How much do you want to do in-house and how long do you have to make it profitable? It is an ongoing investment, and that is not an easy sell. You may have to buy a furnace and other equipment before you have a sale. You are not going to learn enough if you try to do it too fast or too cheaply." 

Materials and Molding 
One thing plastics injection molders should consider is whether or not to make feedstocks or buy them. Carlson recommends that newcomers to molding metals and ceramics buy feedstocks, just as they buy plastics resins and compounds. Feedstocks suppliers can offer assistance in a number of areas, not the least of which is proper feedstock selection. 

Compounding feedstocks in-house poses a number of trying questions. For example, which technology should be licensed? Are personnel on staff experienced in metallurgy and compounding, and is the proper compounding equipment in place? Who are the material suppliers? And, have preparations been made for powder handling, storage, and lot certification? 

When it comes to capacity utilization, should a molder use existing machines to mold feedstocks or buy new ones? "Machines must be capable of molding to tighter tolerances than plastics machines," says Carlson. Metal and ceramics are more abrasive and molded parts can often be smaller and more complex than plastic parts. So there are differences in compression ratios and shot sizes, screws and barrels, and in purging and cleaning requirements. 

Depending on the type of feedstock being run, there also can be significant differences in auxiliaries, particularly in granulators. Secondary finishing equipment also may be required, like systems for drilling, tapping, deburring, and coining. Carlson says tooling challenges are comparable for both processes. 

Powder injection molding involves a lot more than just buying a new molding press.

A Different Kind of Plant 
As with feedstocks, Carlson says the question of whether molders should debind and sinter parts in-house must be considered. Toll debinding and sintering services are available from furnace vendors on a cost-per-part basis, which can be an economically advantageous choice for beginners. Choosing to debind and sinter in-house might eventually prove more profitable, but several factors must be considered, not the least of which are the type of methods used, the type of equipment required, and the possible safety and health regulations that must be met. 

Will the debinding and sintering be batch or continuous? How big will the systems be? How will the types of systems selected impact lead times? And what type of gas handling and cooling requirements will be involved? The proper storage of gas, solvents, and acids also is a key issue. "Find out all the regulations up front. It might not be a problem when you are starting out and your part volumes are small. But volumes can increase fast," Carlson says. 

Powder injection molding involves a lot more than just buying a new molding press. Carlson says a number of other special building enhancements have to be considered. Molders must carefully evaluate their current building capacity and optimize plant layout for optimum process flow. Air evacuation and materials handling systems should be primary concerns. 

Whether inspection and testing is to be done in-house is another decision molders must weigh. Plastics molders deciding to do it on their own may have to familiarize themselves with unfamiliar types of analytical instruments, such as microhardness testers and helium pycnometers. 

Total Process Control 
Finding the right people to make the operation successful can be challenging. Schools are a good place to look for qualified personnel. Retraining internally is another good option, Carlson says. 

"I would rather develop new people internally than go head hunting at existing powder molding shops," he explains. Perhaps the biggest people problem he has encountered is getting the sales force on board when going from plastic to powder, particularly sales reps. "Training plastics sales reps is tough. They are back at square one." 

In summary, Carlson says there are lots of decisions that have to be made. He strongly advises that those wishing to make the move remain "emotionally stable" when encountering the changes. "Never assume a part is a 'no brainer,'" he adds. 

Most of all, Carlson reminds plastics injection molders that powder injection molding is not just about molding. It is a multiple-step process requiring total process control. "All steps in the process are critical," he says. 

Editor's note: Ron Carlson will discuss what it takes to do metal injection molding at IMM's Molding Technology 2001 conference Oct. 1-2 in Chicago, preceding Plastics USA. For more information, go to www.immconference.com. 

Contact information
Smith Metal Products
Lindstrom, MN
Ron Carlson
(612) 257-2767
[email protected]

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