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Optimum Injection Speed 3
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dwightdixon
Materials
Injection speed is dependent on the type of material and its ability to shear thin as well as the potential for surface defects caused by filling too fast thru sharp flow transitions. Start by consulting the materials supplier and then let the machine tell you when you are going too fast and limiting out the injection pressure. Slow it down, if you are getting jetting or surface delamination.
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- #3
Dwightdixon,
As you mentioned "let the machine tell you when you are going too fast and limiting out the injection pressure" How to find it that we are going too fast or too slow? Are you referring to any viscosity curver? if so please explain in detail.
As you mentioned "let the machine tell you when you are going too fast and limiting out the injection pressure" How to find it that we are going too fast or too slow? Are you referring to any viscosity curver? if so please explain in detail.
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- #4
check out
also check out
read articles on
These will give you a lot of information about plastics processing. After you got your basics down let us know if you have a specific questions.
also check out
read articles on
These will give you a lot of information about plastics processing. After you got your basics down let us know if you have a specific questions.
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1
- #5
patprimmer
New member
Injection speed is always a compromise.
Basic rule of thumb is to inject as fast as possible without causing problems.
Filling to fast can cause:-
Burns from shear.
Burns from gas traps.
Poor surface from jetting.
Poor surface from turbulence over sharp edges.
Over pack and flash from hitting the mould full point with to much inertia in the screw.
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.
Basic rule of thumb is to inject as fast as possible without causing problems.
Filling to fast can cause:-
Burns from shear.
Burns from gas traps.
Poor surface from jetting.
Poor surface from turbulence over sharp edges.
Over pack and flash from hitting the mould full point with to much inertia in the screw.
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.
The question is what the injection speed is to fill the cavities. If it is a hydraulic or an electric machine is irrelevant.
The injection speed depends, as mentioned above on the material rheology. It also depends on the part design and requirements and the mould design, specially the type of gate and dimensions. A mould flow analysis may help.
For the part of "let the machine tell you", I agree, but there should also be a way to determine it theoretically while the mould is in its design face. I would like to see a post with some formulas. When the mould is already built, visit (no affiliation). They have free and paid stuff to come up with the right injection speed and other set up parameters.
Mauricio Benavides
Injecnet Solution Inc
The injection speed depends, as mentioned above on the material rheology. It also depends on the part design and requirements and the mould design, specially the type of gate and dimensions. A mould flow analysis may help.
For the part of "let the machine tell you", I agree, but there should also be a way to determine it theoretically while the mould is in its design face. I would like to see a post with some formulas. When the mould is already built, visit (no affiliation). They have free and paid stuff to come up with the right injection speed and other set up parameters.
Mauricio Benavides
Injecnet Solution Inc
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