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Plastic Processing is about plastic truly sees

The old school understandings around processing are pretty much proven the wrong way to work and knowledge more than 10 or 15 years old is way out of date, get current. There is much written about and many good trainers who can help bring your processing ability to state of the art. I recommend this as I continue to find that too little of good engineering practice is being used to the detriment of everyone involved. Strong and robust methods will bring rewards ten-fold back not to mention a bit of excitement at how the trade is changing.

Much of this discussion has been around bit's and pieces, using a DOE approach will gather these and augment the data set. In turn this will help shed huge amounts of light on the problem AND reveal areas you might have thought were OK. I can not overstate how valuable this approach is. Done well and you won't be back asking this type of question... not that that is bad.

Remember, processing is about what the plastic truly sees not the machine settings. Knowing the true plastic settings will allow you to move the tool around (mostly) and produce good parts. Always remember that the press only measures values at a secondary or tertiary relationship to the plastic. This is what scientific molding corrects.

The best practice method is to make an air shot and then measure the temperature of the resulting melt pool with a needle pyrometer - if you don't have one don't feel too bad because 80 percent of the injection mold shops I walk into don't have one either - just go and buy one today – it's the only way that you will find the right temperature - the machine controls only tell you the temperature of the metal of the barrel where the thermocouples are and almost always are significantly different from the measured melt pool.

Old School processing, using machine settings as true is what I refer to as "Faith Based" Processing.

It's about the plastic not the machine, the true melt temperature is the 30-30 check. The best way to check it is to check the melt after the machine runs a few cycles. This way you get a true melt from the screw running under a full load. If you do it on a purge shot you may not read the true melt. You can also sensor the injection mold with temperature sensors to read the melt of the plastic when it enters the mold cavity. I have found this to be very helpful also. This will show you the shear heat from the barrel into the injection mold as it goes through whatever runner system the mold is equipped with.

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