Injection molding machine supplier Sodick IMM by Plustech is entering the metal injection molding (MIM) space with its new Micro MIM (m:MIM) line. Described as a precision metal powder injection molding machine, m:MIM is based on the company’s V-Line melt preparation and delivery system with a newly designed injection unit dedicated to micro MIM molding.
Sodick Plustech says the precise fill control and high injection responsiveness result in net-shape parts that do not require secondary processing while overcoming the material’s challenges, including narrow process windows, easy flashing and quick solidification. Plustech Vice President Kohei Shinohara introduced the technology in a presentation at Molding 2023 in Minneapolis.
Shinohara said the Micro MIM (m:MIM) design would have to address the challenge of metal powder infiltrating spaces between the injection plunger and cylinder, causing galling and injection malfunction. With conventional anti-galling approaches, only the same level of holding pressure as conventional machines can be applied, and filling density cannot be increased.
To address this, Sodick Plustech applies a patented design in the m:MIM. This includes using highly lubricated steel for the injection sliding components, which leaves the structures less susceptible to damage from metal powder. In addition, the plunger-style injection unit can achieve high injection holding pressure and temperature control at the plunger’s rear, which reportedly improves the injection process’ stability, while reducing the amount of discharged material. A scraper ring that goes around the injection plunger enables a resin seal to form, which makes higher pressures possible.
Sodick Plustech notes there is no backflow during injection with the V-Line injection unit, with the injected material’s velocity matching the velocity of the plunger. The company adds that because the plunger is short and lightweight, the initial injection speed response is faster than the conventional reciprocating screw with resin.
In tests compared to standard inline MIM injection systems, Sodick Plustech said its two-stage injection resulted in parts with no burrs or flow marks, including a smooth gate area. In addition to cosmetic benefits, Sodick Plustech said this results in less part-weight variation.
The company conducted a spiral flow experiment to investigate the machine’s impact on melt flow, taking a 10-shot sample at two different velocity settings: 20 cc/sec and 4 cc/sec on a conventional MIM machine and the m:MIM. For 20 cc/sec, the conventional machine’s spiral flow length came in at 100 mm vs. 130 mm for m:MIM. For the 4 cc/sec run, m:MIM produced a 57-mm-long spiral flow compared to 12 for conventional. “There’s a big difference in the slow-fill process and our observation is the longer flow lengths are due to the high-response plunger injection,” Shinohara says.
The m:MIM package will be available on four machines: the LP20EH3, GL30 and GL60 hybrid presses, as well as the MS50G2 all-electric machines, with clamping forces from 22 to 55 tons and injection volumes from ½ to 1.8 ounces. Initially the company will launch with two injection unit sizes, with plans to add two more — one bigger, one smaller — down the road.
