LS Mtron's ONE MuCell line is designed for Trexel's foaming process

By Karen Hanna 

With the introduction of its newest injection molding machines (IMMs), LS Mtron is lining up solidly behind foam. 

In partnership with Trexel, LS Mtron has launched its ONE MuCell series, the first IMMs on the market specially designed to handle MuCell molding, Trexel’s physical foaming process for making lightweight parts.  

“The molder would have all of the features needed for foaming, and some of the most important attributes have been given extra attention, such as tie-bar spacing, precise position control and back-pressure control, and a long screw,” with a L:D ratio of 23:1, said Trexel President and CEO Brian Bechard. 

Trexel, which has offered the MuCell process and technology for 25 years, is partners with 20 IMM OEMs that can provide MuCell-compatible machines, Bechard said. 

"What LG is doing here is mainly making it easy for their customers to buy a standard-configured machine that has been optimized for MuCell," he said.

Available with clamping forces from 550 tons to 3,600 tons, ONE MuCell presses have several features that make them ideal for the process, said Peter Gardner, business director of LS Mtron Injection Molding Machine USA.

“The following three features directly affect MuCell performance: screw design only for MuCell foaming, high-pressure system and an injection unit optimized for foam molding,” Gardner said. 

In addition to its ONE MuCell series, which comprises 10 machines, LS Mtron is touting its One Stop Solution for foam molding, with molds, auxiliary equipment and complete turnkey manufacturing cells.

Gardner said foaming is increasingly popular among molders of automotive parts, sound and heat insulation, home appliances and packaging.  

Compared with conventional molding, MuCell reduces the injection pressure required to fill a part; however, molders can still equip their machines for high-pressure molding, to produce thinner parts or achieve faster injection speeds. 

The amount of resin and weight MuCell applications can save compared with conventional parts varies, Bechard said. 

“Typically, we are getting density reductions in the 8 to 10 percent range (although in some cases we have seen much higher and much lower numbers), but often weight savings is driven by part designs optimized for foaming,” he said. “With lower injection pressures, reduced material viscosity and homogeneous filling through foaming, instead of through pack, we can often enable part designs that have thinner walls.”    

The exact benefits depend on the part, he said. 

“It is not atypical for a MuCell-foamed part to have 8 percent density reduction, but a design that uses 22 percent less material, resulting in a total of 30 percent weight reduction from the same part molded traditionally,” Bechard said. 

ONE MuCell presses are designed to control the positions of the tie bars, screw and clamp with precision, Gardner said. They also are capable of core-back movement, in which the core side of the mold retreats, initiating the foaming process and facilitating the creation of a large cell foam core and stiffer, lighter-weight part. 

In addition, the machines have a screw that produces a foam of uniform quality, composed of a mix of molten resin and a fixed quantity of dissolved nitrogen in a super-critical-fluid state.  

“Through high-speed injection, it is possible to control the formation of the foam structure,” Gardner said. 

Though built for MuCell foam molding, LS Mtron’s machines aren’t restricted to lightweighting applications, Gardner said. 

“Non-foaming (solid) application is possible without converting to a standard injection molding machine,” he said. 

In addition to its foaming-centric features, the machines boast a design that simplifies mold changes. They are equipped with a control from Keba Group AG, Linz, Austria, designed for user convenience. 

Karen Hanna, senior staff reporter  

[email protected] 

Contact:  

LS Mtron Inc., Norcross Ga., 678-395-4389, www.lsmtron.com 

Trexel Inc., Wilmington, Mass., 781-932-0202, www.trexel.com