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Tech Tip March-A 1996

Volume:

The question that I have is how is your barrel calibrated on your molding machine of choice? What is it that you set your shot size to? What is the scale that you are using on the machine? Is it in mm or inches or what? Why is it not in cubic inches or cubic centimeters? What are we shooting into the mold? A volume of something is it not? If we have a vivid imagination, would we not see the barrel as a big syringe? We can get disposable syringes for pennies and they are calibrated in cubic measurement, yet the molding machine is not calibrated.

If it sounds as if I have questions, I do. We have accepted again what the manufacturers sell us, and not put in our request for a system where we can go from one machine to the next and set up a shot size the same, even though the barrel size is different.

Why change? Do you move the tools around from one press to another? If we have the shot size in cubic inches (or cubic centimeters), would it not be easier to move around? Thus when we go from press A to B we now know where the shot is going to have to be. This then eliminates the guess work during set up and saves time.

To convert what you have is as simple as adding an additional scale to your present one on the press, and calibrate it to cubic measurement ("pi R Squared" times the length will give the cubic volume per that length). Place this scale below the other and now everyone can get used to what the new scale is and set-ups become better. Best yet, is if the machine comes with it. Of course you need to put this change onto the setup sheet and use it. Should you do this and use it, then your time for set up and change over will be reduced.

Thanks for the time.

Steven L Silvey
Sr. Technical Service
General Polymers