Hi all, I am reviewing a spreadsheet for estimating part prices via injection molding. I have come across the issue of estimating required clamping force. I know there is a system by which the required clamping force is estimated by multiplying projected area by a pressure factor that differs from resin to resin, but I have not been able to find an extensive list (including GF materials, for example) or a more accurate data table for pressure factors (usually, they give quite a wide range for a given material). Does anybody have any more extensive info on the issue? Thanks in advanced for your help!!

Hi Jordi,
I guess every injection moulder would like to have such a list as holy grail for these calculations. Unfortunately it is still difficult to compile all data thats comes into play in a list. Its not just the material and projected area, it is also the application itself and processing parameters that play an important role. Is it a thin wall part? High injection velocities? What are the cycle time rquirements? Is the mold cooling (or heating) optimal? What kind of barrel do I have on the machine? etc etc. In other words, it makes more sense to look at the specific situation at hand (or maybe you can group it a bit such as thin wall packaging for example were high injection speeds and high cavity pressures are involved) rather than trying to calculate it from a list.. but who knows if somebody made a list......but I guess that list will be pages long. If you have specific info on parts whcih you investigating I am willing to help you out! Regards, Theo

Jordi,

How to calculate necessary force is not a correct question!
The correct question should include the degree of accuracy!
For example in small molding shops the question is usually: " is this machine big enough, or shall I go to the bigger?". So, the accurate figure is of no use (so, why should anyone invest to get it..). A relative calculation is usually enough.

At the most demanding end, the solution is simple. Get a mold flow simulation to get an accurate figure regarding the clamping force!

To perform an approximated flow simulation targeting the clamping force (i.e. accepting a lot of simplifications in the 3D model) is rather simple and fast.