Recently we have been searching for some clear plastics which have high strength and can maintain good transparency even when wall thickness is relatively large. We were unable to find a good material which could fit our Plastic Design specifications of high stress crack resistance and has a good color blend ability in spite of being transparent. This is where we came across Grilamid TR90 and Grilamid TR55. Both these transparent plastic grades are excellent polyamide thermoplastics which possess the qualities of an engineering polymer, although they are transparent. We have added them into our list of the chosen resins for Electrical parts, electronic parts, car parts and other automobile parts and other similar applications in domestic appliances.
The technical data sheet of Grilamid, both TR90 and TR 55 provides us with essential properties that Grilamid possesses, and renders it as the best choice of transparent material. I have often seen a lot of clear plastic parts cracking and bending too much, but Grilamid has got rid of this problem in transparent plastic processing.
Now I will provide you with a few basic runner and gating design guidelines for Grilamid injection molding processing that should be incorporated into tooling and molds. Although this information is available freely on the Grilamid website, I though it would be good to share it here to save time of those reading this article. To achieve an optimal mold-fill and to avoid sink marks, a central gate at the thickest section of the moulding is recommended. Pin point gate (direct) or tunnel gates are more economical and more common with technical molding.
To avoid premature solidification of the melt and difficult mould filing, the following points should be considered:
Gate Diameter: 0.8 x thickest wall section of the injection molding part
Runner Diameter: 1.4 x thickest wall section of the injection molding part (but minimum 4 mm)
The drying time for Grilamid is a bit long, which is understandably so, as most of the clear resins require a long drying time to avoid bubbles and air traps due to moisture. It needs a Desiccant dryer and the drying time needs to be over 5 hours with a temperature of 80 degrees Celsius. If you use a vacuum oven, you need to dry it for at least 8 hours at the same temperature.
Will continue with this post later when we actually mold the Grilamid part to update with the optimum injection and processing conditions on our plastic processing equipment. Make sure that you bookmark the site to get updated information on Plastic Injection Mold Design for various polymers.
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