Thermoformers typically have not had much choice in materials for making prototype molds to test new product designs. That's changed with the introduction of Hyvac-LCM (Lightweight Composite Material) from CMT Materials Inc. (Attleboro, MA). "There has been a big gap between aluminum tooling for production and wood or MDF to make prototype molds or molds for short runs," said Conor Carlin, Hyvac Sales & Marketing Manager. "Wood or MDF isn't suitable for plastics. What we've developed is an alternative to wood with performance closer to aluminum."
Hyvac-LCM is a new composite mold material that allows thermoformers to optimize material distribution, reduce or even eliminate chill marks, reduce tool weight and simplify mold production for cut-sheet thermoforming. The product consists of a smooth syntactic outer shell easily formed over a porous inner core of composite beads. The porous core allows vacuum anywhere in the tool by drilling holes in the outer shell.
Carlin had samples on display at the SPE Thermoforming Conference, which ran from Aug. 31 to Sept. 2 in Atlanta, and he explained to PlasticsToday how Hyvac-LCM works. The sample of the wood prototype mold had numerous holes drilled in the bottom to allow for the vacuum. By contrast, the Hyvac-LCM mold uses tiny composite beads that permit vacuum suction without needing to drill holes in the bottom of the mold—just two tiny holes are drilled in the syntactic shell on top of the mold.
Hyvac-LCM offers ultra-low thermal conductivity and improved material distribution. The fused shell and composite bead core provide high strength for durability. It offers rapid mold construction, and the syntactic putty is stable at room temperature for extended periods of time, then cures overnight at 280° F.
The product is available in kit format, allowing the user to machine a tool from a drawing model or fill a negative cavity pattern. The kit contains one gallon of syntactic putty (enough to cover 300 square inches with the recommended ¾-in. starting thickness) and 0.5 ft3 of reinforced, high-temperature spheres, resin and catalyst (enough to make a 6 x 12 x 12 in. block) to make the porous core. Putty and porous core material may also be ordered separately to more closely match specific job requirements.