New offerings from MuCell inventor Trexel allow injection molders to take on the foaming process without committing to the heavy lift of adopting more specialized equipment or sacrificing throughput.
Designed to be used as an add-on to both standard and specialized molding screws, Trexel’s new Screw Tip Dosing Module, also known as TDM, replaces the traditional screw tip and mixes gas as part of the MuCell process, which reduces part weight through foaming. To handle the high pressures required by the MuCell process, Trexel also has released a new gas injector, the SCF, that can use a standard melt pressure port.
Trexel President Brian Bechard predicted that the TDM, which eliminates the need for one of two nonreturn valves, will permit more molders to adopt the MuCell process. The TDM “offers a flexible, modular solution and makes it easier and less expensive for customers to implement and realize the benefits of MuCell molding,” he said. It is easily reversible for users who want to perform conventional molding on the same machine.
Before the release of the TDM, there was only one way to run MuCell — with a plasticizing unit specially made by Trexel or designed to its specifications. While new machines could be retrofitted with a special screw and barrel, Bechard said that about 80 percent of the time, molders started from scratch.
The TDM is a screw-on adapter that gives molders greater flexibility. It can be used with an extra-long barrel or with a barrel extension provided by Trexel or screwed onto a shorter screw in an existing barrel. With it, parts manufacturers can take on the MuCell process, without replacing their presses’ screws and barrels.
The TDM also addresses a serious shortcoming of the conventional MuCell process — diminished throughput.
“Big advantage of TDM is that we no longer see the throughput reduction associated with the typical MuCell screw,” Bechard said. “Where we would see the output of a traditional MuCell screw be about a 30 to 40 percent reduction versus solid molding, the TDM has comparable output to a standard injection screw.”
The TDM provides more options to molders of products, such as thin-walled packaging, that were previously constrained by concerns about capacity. Because it uses one nonreturn valve rather than two, it also addresses previous concerns regarding screw wear and fiber length, opening the MuCell process up to molders of products reinforced by long glass fibers (LGF), he said.
And, Bechard said, because the SCF gas injector is designed to cope with gases under high pressures, it eliminates the need for a center check ring and burst disc in conventional MuCell screws and barrels, as well as TDM setups.
“By eliminating our center check ring, we eliminate the greatest wear item and greatest cause of fiber breakage in LGF applications,” he said. “So, for those applications where MuCell was at a disadvantage, it will now be a stronger candidate.”
While molders have been performing the MuCell process for decades using conventional MuCell equipment, Bechard said he expects the TDM to make a dramatic splash in the market.
“Conventional MuCell is perfectly suitable for many applications and has been in successful commercial use for 20 years, but we expect that eventually all new MuCell implementations will use this new approach, as it has processing and cost advantages,” he said. “We expect this development to lead to a larger MuCell market.”
Karen Hanna, copy editor
Contact:
Trexel Inc. Wilmington, Mass., 781-932-0202,
