Get Your Pressure Right

Hydraulic Pressure vs Plastic Pressure

When we refer to injection pressure, we can be talking about one of two things. We can be talking about hydraulic pressure which refers to the pressure that the hydraulic ram is exerting on the screw or we can be talking about plastic pressure which is the pressure that the screw puts on the melted plastic.

These two are not the same thing and if you specify an injection pressure range on your processing guides, you should only specify hydraulic pressure and you should be very clear about it.

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How Hot Should The Nozzle Be?


Many material manufacturers and suppliers provide processing guides for the materials that they sell. Often, these data sheets are so general as to almost be useless. However, I see a mistake on a great number of processing guides and I think should be corrected. It relates to the nozzle temperature.

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The Trouble With Colors

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Back when everyone was running injection molding machines with plungers, if you needed to color material, you had to have it pre-colored at a compounder. The compounder would melt the natural material down, blend in raw pigments and other additives and then re-pelletize the material.

The advent of screw type injection machines and color concentrates significantly reduced the cost of coloring plastic materials. However, running material blended with color concentrate has its challenges. It has to be mixed carefully and the material has to be processed carefully to get good results. Sometimes, even if you do everything right, you end up with nothing but problems.

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