Take control of those “sticky” parts
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 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. Slide Universal Mold Release fits the bill for this application.
2) Will parts require sonic welding or be finished by painting, hot stamping, screen printing, pad printing, vacuum metalizing, electroplating, etc.? Some releases cause adhesion problems. Often the lack of good adhesion is not apparent until after the part is in service. If any molded parts are to be decorated post-molding, be certain to use a “paintable” mold release agent.
3) Are FDA approvals required? Medical molding and parts for food applications may require a release that has FDA approval.
4) Is UL recognition required?
5) Are you molding a solvent sensitive resin? Styrenics such as ABS, Styrene, Polycarbonate, SAN, etc. are sensitive to chlorinated solvents that can cause surface blemishes or stress cracking. Polycarbonate is well known for stress cracking after the part is put in service.
How do you evaluate a release?
Now that you have narrowed your choices, you should perform a production trial. Here are a few tips to make the results helpful.
1) Plan an evaluation. To get meaningful results be scientific with appropriate standards and procedures.
2) Do the test using your toughest part. If that looks good, try it on other parts molded with a variety of resins.
3) Make sure that you have a benchmark for comparison. If you are spraying every sixth shot on part X, see if you can do it with every seventh or eighth. Each additional cycle without spraying can add up to a significant savings.
4) Be certain to thoroughly clean the mold and remove all traces of the old mold release.
5) Be sure that molding conditions do not change during the trial. It is best to set up and make evaluations of all releases during one press operation session.
6) After picking the most effective release(s), run the test with a single full can and record the number of parts that are molded. Now you can determine the cost effectiveness of the release.
Lastly, don’t purchase a release based on the cost per can. If a release isn’t effective, saving pennies may cost you big money in productivity. In addition, look closely at just how much is in each can. The actual amount in each can of release may vary between products and manufacturers. What you are really interested in is how many parts can be molded for the dollars spent on release.
Now that you have the facts established by your release evaluation, you can calculate the best release for the buck for that particular resin and part.
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