Why are injection molding machines not as effective for mixing ...

[leilurhhh]

Why are injection molding machines not as effective for mixing additives or other resins as are traditional extrusion machines?
 
  What will be an ideal response?

Question 2

During the operation of an extruder in making thin-walled tubing, several defects have been encountered that appear to be small globules of resin. Investigation of these globules reveals that they will soften but not melt when heated. Explain what these globules might be and suggest two possible remedies for eliminating them.
 
  What will be an ideal response?

[quynhmickitran]

Answer to Question 1

The length-to-diameter ratio

Answer to Question 2

The globules are likely crosslinked resin that has, for some reason, been created within the extruder. One likely cause is that the extruder may be overheating the resin, thus causing some of the material to crosslink. A solution for this would be to lower the temperature. Another solution would be to add thermal stabilizer additive to the resin which could also prevent this crosslinking from occurring. Another cause of the formation of crosslinked material could be non-streamlined flow in the die. This can be investigated by stopping the extruder and carefully examining the die to see if material seems to be hanging up in some location. If that is the case, the die should be smoothed.

[leilurhhh]

Thank you!

[quynhmickitran]

Always glad to help...