Pressure or Force

[NEngineer]

To patprimmer,

Machine: Compression Molding
Material: Thermoset Plastic / Rubber
Process: Compression Molding

Let me clarify more on this. Say for example you have two different tonnage machines one is 75 Ton and other is 500 ton.

Now you have made one part on 75 tonnage machine with force showing on gage 70 ton while pressure is 2000 PSI. Now if you want to use that mold on 500 tonnage machine, what will you set on gage? e.g. 70 tonnage of force or 2000 PSI. If you set 70 tonnages, your pressure is not 2000 PSI and if you set 2000 PSI then your force is not 70 ton on 500 tonnage machine.

Please support your answers with examples............

 

[patprimmer]

You need to set at 70 tonne.

What line pressure achieves that depends on the machine. The information for calculation will be in the machine operation manual. Modern machines probably have a direct read out in tonnes clamp somewhere in the control system.

It really does depend on the machine and your die setters should be trained to understand the operation of the machine.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[NEngineer]

Patprimmer,

Have you ever worked with Rubber Compression Molding Machine or Thermoset Plastic Compession Molding Machine?

 

[patprimmer]

Yes, but not much. 99% of my experience is thermoplastics.

It is still a hydraulic press.

You still need a certain pack pressure on the resin as it cures.

You can still damage things or get distortion in elastomer mouldings if you over pack.

I can only work with quality of information provided.

The calculations involved are simple high school physics and maths. like Pi times radius squared and force equals pressure times area.







Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[NEngineer]

Patprimmer,

I was in the same impression that thermoplastics and thermoset works same.It is not simple as you mentioned.

This is not just calculation. It is what you establish for your operators.

I know the calculation since very long. If you haven't work on thermoset elastomer compression molding, please don't guess!!!!!!!!!

As per you knowledge with thermoset, to provide you quality information is take toooooooooooooooo long!!!!!!

Any way thanks for your info.

 

[Demon3]

Pat gave an excellent answer to your problem as stated. You asked only about pressure with no mention of thermoset verses thermoplastic, curing time etc. Now you complain? That sounds a little ungrateful. The only parameter of importance is pressure unless you have not stated your question properly. In that case Pat is not to blame.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[mauriciob]

NEngineer
I am also a thermoplastics person with no experience in thermosets. I hope I don't get slammed for trying to give you an answer

If the hydraulic pressure areas were the same (I suppose they are not), the difference in the hydraulic pressure could be due to the difference in the weight of the upper platens of the machines (I am assuming it is a vertical machine). If the diameters are different, then it will be both the platens weights and the cylindrical area.

Mauricio Benavides
Injecnet Solution Inc

http://www.injecneering.com