Improving surface aesthetics of glass-filled engineering thermoplastics is one of the Holy Grails of injection molding. Last year, we showed you the heat-cool process under development at the Sabic Innovative Plastics’ Polymer Processing Development Center in Pittsfield, MA. The key to “heat-cool” or “variotherm” as it’s known in Europe is to heat the mold surface above the material’s glass-transition temperature (Tg) prior to injection, and then rapidly cooling the tool to solidify the molded part. Various devices and techniques are used to boost surface-side mold temperatures. The Sabic engineers use a superheated water system from Germany’s Single Temperiertechnik (sold in the USA by KraussMaffei) that can deliver water at 200C (400F).When I toured the Trexel development lab in Woburn, MA earlier this year, I learned of another approach. Trexel continues to work on improvements in machine conditions that will enhance surface appearance. These include injection-speed profiles, gate sizes, and mold and melt temperatures to get the improved surface.
Trexel says it can produce “piano-surface” parts with a mold temperature approach shown last fall in Germany. Hofmann Werkzeugbau GmbH is using the variotherm approach that uses either dry steam or water to heat the mold prior to the injection of material and then cools the mold down with water.
Additionally, BASF, Rhodia and DuPont offer foaming grades of appearance nylons for applications such as under-the-hood rocker covers. The grades are also useful in power tools, Trexel President David Bernstein told me in a tour of the lab.
Generally speaking, a mold must be equipped with thermocouples that are close to the molding surface to monitor temperature for efficient heat/cool process control. In addition, it’s recommended that the injection mold, the molding machine, and the thermal/cooling controller must be integrated. Sabic Innovativre Plastics built its own control unit to integrate each element. Attention to tool design is also helpful: the time required to heat and cool the tool is a function of the steel’s mass. Sabic recommends inserting, rather than cutting, cavities and cores into the mold plates to help minimize mass. These inserts should be insulated from the cavity and core retainer plates using air gaps and insulation material whenever possible to reduce heat loss and improve efficiency.
As the 3D printing and overall additive manufacturing ecosystem grows, standards and guidelines from standards bodies and government organizations are increasing. Multiple players with multiple needs are also driving the role of 3DP and AM as enabling technologies for distributed manufacturing.
A growing though not-so-obvious role for 3D printing, 4D printing, and overall additive manufacturing is their use in fabricating new materials and enabling new or improved manufacturing and assembly processes. Individual engineers, OEMs, university labs, and others are reinventing the technology to suit their own needs.
For vehicles to meet the 2025 Corporate Average Fuel Economy (CAFE) standards, three things must happen: customers must look beyond the data sheet and engage materials supplier earlier, and new integrated multi-materials are needed to make step-change improvements.
3D printing, 4D printing, and various types of additive manufacturing (AM) will get even bigger in 2015. We're not talking about consumer use, which gets most of the attention, but processes and technologies that will affect how design engineers design products and how manufacturing engineers make them. For now, the biggest industries are still aerospace and medical, while automotive and architecture continue to grow.
More and more -- that's what we'll see from plastics and composites in 2015, more types of plastics and more ways they can be used. Two of the fastest-growing uses will be automotive parts, plus medical implants and devices. New types of plastics will include biodegradable materials, plastics that can be easily recycled, and some that do both.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.