The holy grail—making plastic parts without tooling—is within reach

I recently had the opportunity to attend an open house at Interlink Engineering LLC, a contract engineering firm in Phoenix, AZ, that provides 3D design, product design and development, and engineering services using SolidWorks. The company also recently brought in an HP 4200 Multi-Jet Fusion (MJF) 3D printer and will be a reseller of this machine in the four-corner states and Nevada.

The purpose of the open house was to showcase the capabilities of the HP 4200 MJF. Justin Smart, a mechanical engineer for Interlink, told attendees that while the company has no intention of becoming a 3D printing service bureau, it will provide potential customers with 3D-printed sample parts to demonstrate the HP 4200’s capabilities to help make a sale.

Mark Shokut, an application engineer for HP, first explained the MJF 3D printer’s design, which consists of three modular units: A printer, the build unit and a processing station. The modularity and flexibility of the HP 4200 enables continuous production. After the build is finished, the build unit can be removed to let the parts cool and a second build unit can be inserted into the printer. The parts on the first build unit are taken to the processing station while the second build unit is operating.

A fusing agent used during the printing process absorbs energy from the lamps and a “detail” agent in the processing station improves the surface quality of the parts, Shokut explained.

What I observed is that HP’s MJF is the closest 3D printer yet to being a high-volume parts production printer, the holy grail of additive manufacturing. That is accomplished by “nesting” as many parts as possible in the build chamber to increase the cost effectiveness of each part. While other 3D printers have build chambers large enough to hold many smaller parts that can be built at once, the HP 4200 MJF system stacks, or nests, parts. For example the bottom layer consists of 20 parts but four layers are produced for a total of 80 parts. The software allows for the gaps between the nests.

Additionally, the printed layer’s packing density optimization creates better parts. “[Through] packing density you get more parts, which equals less cost and less part diversity,” said Shokut. “Also, less density means more parts and lighter weight. Packing density is important because this machine is meant to be a production printer.”

There are no draft constraints, as there would be with injection molded parts, and no gate considerations. Nesting deep ribs are not a problem, either, as there are no concerns with surface sinks.

Shokut stressed that 3D printing is “design-driven success” that opens up the process window to get better parts. “In 3D printing you design for the process,” he said.

Interlink Engineering’s Smart gave a presentation called “Skipping the Tooling,” which I’m sure won’t make moldmakers happy. If 3D printing is disruptive to moldmaking in any way, it is in the area of making pilot molds for trials and part iterations. “3D printing is ideal for developmental parts, and has  economic and time advantages, and increased performance of the parts,” Smart told attendees. “New product development takes about half the time to design for MJF compared with injection molding, which means it shortens development cycle time dramatically.

“If you’re looking at four ideas and trying to decide which works best, with 3D printing you can make all four iterations in a few hours or days with no tooling,” Smart added.

Other advantages to 3D printing parts include the fact that sharp corners and undercuts are not a problem. There are no parting line considerations and no ejector pin marks, and no lifters or slides needed; no runner systems and sprues to result in material waste. Currently, Interlink is building parts in PA 11 and PA 12 and it gets about 20% unused powder using PA 12.

Another big advantage is part consolidation. Smart gave an example of Interlink combining six components into a single unit using AM. With injection molds costing $140,000, the piece part price was $26.10. Without tooling and combining six parts into a single unit, the part price was reduced to $7.88.

With break-even at 55,000 parts, and 110,000 parts on the latest HP MJF printer, 3D printing is getting extremely cost effective. “If you need fewer than 55,000 parts, you need to be doing 3D printing,” Smart advised.

I was truly impressed with the advances HP has made with the MJF 4200 printer, which has a much better opportunity for high-volume part printing than is currently being offered. I’d say that moldmakers could benefit from this technology in a big way by providing this value-added process for product development and short-run production. Given the cost savings and the advances in polymer materials for 3D printing, pilot molds will soon be a thing of the past.

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