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Plastics/Calculating Shot size/weight


Romeo wrote at 2013-10-10 11:54:55
By my calculations you will need at least a 500 Ton press for this job!  If the part is that dimension you may not even be able to fit mold into a 350 JSW.  You need to also know the barrel capacity of your machine and the part weight(actual or theoretical) to determine if you have enough shot in the machine.  The SG(Specific Gravity) of material is also needed.  In your case PP is from .85-.95 so you can use .90.  Keep in mind OEM uses Styrene to guage barrel capacity, Styrene=1.05.  For a good rough estimation you take PP(.90) divide by 1.05 then multiply machine capacity Oz this will tell you how much PP you can hold in your machine and if you have enough shot.  Like the answer above 80% of shot allows proper melt characteristics to mold a good part.  Hope this helps.


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Robert Tomlinson


Tooling design,design for manufacture,tooling procurement,machine design,machine procurement,
Processes injection moulding,injection blow moulding,extrusion blow moulding, process control,productivity improvement,Quality,Decoration,Assembly,Automation.Thin wall moulding expert.


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