Trexel Inc. is marketing its Series III MuCell system at manufacturers of small-tonnage injection molding presses - and giving the Series III a smaller price tag to go with it.
Engel Holding GmbH and Arburg GmbH + Co. KG have said they will offer the Series III as an option on their smaller presses. Trexel expects to sign up more machinery makers.
In other news, Trexel has introduced a new screw design for running MuCell to mold parts from long glass fibers.
The Series III marks a change in strategy for Trexel of Woburn, Mass.
``This is the first time we've offered a fully integrated technology package to the equipment suppliers,'' President David Bernstein said in a telephone interview. ``In the past, we've drawn the boundary between the things that are inside their machine that make MuCell work, and the gas system and the interface system that we supply. Now it will be all transparent. The entire package will be inside the molding machine.''
Trexel has a history of licensing press makers, allowing them to use the MuCell microcellular technology on their machines. It has been easier to sell for larger parts, since molders can see a quick return on their investment through reduced resin use. However, for small-tonnage presses, Bernstein said one barrier had been the relative cost of MuCell to the machine.
But he said MuCell's real strength is for small precision parts - by eliminating nonuniform stresses from traditional solid molding, to give extraordinary dimensional stability. Trexel claims internal pressure from the bubbles reduces warping and improves flatness and roundness. It also eliminates sink marks, the company said.
MuCell also reduces part weight and cuts cycle times by as much as 35 percent.
``What we're hoping is the leading [original equipment manufacturers] will put this into their product line, now that it is at a price that is pretty moderate, compared to the price of a molding machine,'' Bernstein said.
Trexel said the pricing for the Series III MuCell, including the microcellular equipment, interface kit and all operating rights, will run between $55,000 and $75,000. There will be no licensing fee for molders.
Trexel first announced the simpler pricing structure at NPE 2006, including the elimination of a separate licensing fee for molders. The company announced the Series III on July 20.
Series III is designed for machines with clamping forces of 120 tons or less that use screw sizes of 40 millimeters or less. Bernstein said the ``sweet spot'' is presses from 60-100 tons.
These days, many of those small-tonnage presses are all-electric.
One key change is an all-electric pulse-dosing technology, which supplies exactly the right amount of gas for each shot. Previous versions of MuCell have used air-driven pumps and continuous dosing, pumping in a continuous amount of gas and then diverting the excess back through the system.
The pulse dosing is more efficient and repeatable - a key feature for molding small parts. The gas supply is fed from a cylinder to a gas piston. An electric-drive linear motor attached to the piston compresses the gas to a predetermined pressure.
``Sometimes you're dosing it at the microgram level,'' Bernstein said.
Trexel said more than 300 injection molding machines are running MuCell worldwide.
MuCell uses compressed nitrogen or carbon dioxide to create microscopic bubbles to lower part weight, reduce fill pressure, improve mold fill and boost cycle time. By carefully controlling temperature and pressure, the gases are brought to a supercritical state. The tiny bubbles form as the melt goes into the mold.
Trexel said the new screw for long-glass-fiber molding with MuCell minimizes damage to the materials, which typically have a fiber length of 12 millimeters or longer
Bernstein said the company combined its experience in injection molding and extrusion to adapt its extrusion screw design, so the screw avoids cutting the fibers during molding.
Engel is installing MuCell and one of the new screws on a 1,000-ton, two-platen Duo press at its technical center and training facility in York, Pa. The press will be available for mold trials using long-glass-fiber materials. The screw design uses a lower compression ratio and reduces shear by incorporating significant changes to the center restriction element and reducing flights on the wiping and mixing sections, according to Trexel.
Trexel said the screw design also will improve the performance of parts reinforced with standard, chopped-glass fibers.