manufacturing

I am a mold designer and have no idea why you would need such information. There are rules of thumb one uses but I have never used any specific calculations for any of the above and I've been designing injection molds for 15 years.

It appears that you may want to be a self-made mold designer. This takes years of experience and knowledge. Is your main objective to specify type and thicknesses of tool steel to be used? Leave it to the experts. There are stress calculations that are run to determine the supporting cavity side wall steel thickness per cavity depth, along with injection pressures and clamping force, to ensure that the side walls will not blow-out. You also have other factors that need to be addressed that I will not go into. Your best best? Talk to your steel manufacturers, for now, and find an expert that can become your mentor.

Good luck.

Maybe some of this might be of interest to you.

Some Common Calculations for Moulding

Shot Volume in cc = Shot Weight in grams / Resin Specific Gravity

Shot Weight in grams = Shot Volume cc X Resin Specific Gravity

Specific Gravity is the weight of one cubic centimeter of the material in grams

Injection stroke mm for shot = Max Injection Stroke mm X Shot Volume cc / Max Machine Shot Volume cc

Percentage of Machine Shot = Shot Volume in cc / Machine Injection Capacity in cc X 100

To find the actual injection pressure from a percentage

Actual pressure PSI = Percentage / 100 X Max Injection Pressure of machine PSI

To find the percentage setting when the required pressure is known

Percent = Required Pressure / Max Pressure X 100

Generally, the preferred shot size is between 10% and 60% of the machine maximum shot

To find the equivalent injection pressure percentage setting for a machine with different maximum injection pressure ( Machines with different screw sizes or by different manufacturers)

New machine percentage = First Machine Percentage X First machine Max Injection Pressure / New machine Max Injection Pressure

PSI = BARs X 14.7

Degrees F = ( Degrees C / 5 X 9 ) + 32

Degrees C = ( Degrees F – 32 ) / 9 X 5

Injection Shot Size in Oz.

This is an obsolete way of specifying the shot size or machine max shot size. The ounces refer to the weight of polystyrene in the shot. Polystyrene has a specific gravity (S.G.) of 1.06. There are 28.4 grams in an ounce.

Shot cc = Shot in oz / 1.06 X 28.4

Some of your information is not correct. The recommended shot size is approximately 80%. If you are dealing with heat sensitive materials and your relative viscosity is quite high then excessive shearing could take place. In addition, the residence time in the barrel is increased 800% more at 10% barrel utilization vs. 80%. Combine the shearing and the long dead time and you can start to degrade the material. The MW changes and therefore its properties also change. Use 80% barrel utilization to be safe.

Clamping pressure will depend on area of parts being molded.

CustomPartNet has some calculators for injection molding here:

http://www.custompartnet.com/calculator/injection-molding

Further information on injection molding and mold design can be found here:

http://www.custompartnet.com/wu/InjectionMolding

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