steven's blog for plastic mold and plastic molding

Why do some parts just refuse to let go? Well, there are a couple of possibilities. It might be a mechanical situation like an undercut. Or it might be chemical adhesion. The result is pretty much the same. The part doesn't come out freely, "hangs up," is damaged, deformed or has a surface blemish. Regardless, it impacts cycle times and cuts into your profitability. A plastic mold release might be the best option to keep stubborn parts in check. How do you pick the right mold release? There are many types of mold releases: silicones, paintables, vegetable oils, PTFE's, waxes, etc. Here's how to choose. 1) Are you looking for a "universal" release to help avoid having several release agents in your plant? This will probably give you a less than best release for some jobs. But you can avoid possible part contamination if you use a single all-purpose release. 2) Will parts require sonic welding or be finished by painting, hot stamping, screen printing, pad...

plastic mold machines Hourly Rates Dipped Custom injection molders’ machine-hour rates dipped 1.3% on average in the second quarter of the year, according to 122 plants responding to our latest semi-annual survey. Rates have been dropping since the end of 2000. About 12% of respondents said their rates were lower in the second quarter than in the quarter before. Only 5% raised rates, and 83% did not change them at all. However, there were some signs that business was turning the corner at midyear. Molders’ average machine capacity utilization rose about 1.5 percentage points to 53%—still very low by historical standards. Almost 40% of respondents said their capacity utilization increased in the second quarter, versus 31% whose utilization was lower and 29% whose utilization was un­changed. This was the first time since early 2000 that more shops were gaining business than were losing it. Southeastern molders again enjoyed the highest capacity utilization, while those in the West had th...

plastic molding parts design March 22nd, 2009 Plastic injection molding is the primary process for manufacturing plastic parts. Plastic is known to be a very versatile and economical material that is used in many applications. Although the tooling is expensive, the cost per part is very low. Complex geometries are possible and limited only to mold manufacturability. Your computer monitor, mouse and keyboard are injection molded plastics. Injection molding involves taking plastic in the form of pellets or granules and heating this material until a melt is obtained. Then the melt is forced into a split-die chamber/mold where it is allowed to “cool” into the desired shape. The mold is then opened and the part is ejected, at which time the cycle is repeated. Design Considerations Part design should include draft features (angled surfaces) to facilitate removal from the mold. Depending surface length draft angles down to half a degree are reasonable. Typical draft angles should be about 1 ...