This topic contains a solution. Click here to go to the answer

Author Question: Explain the purpose of a preplasticizing unit. What will be an ideal ... (Read 30 times)

PhilipSeeMore

  • Hero Member
  • *****
  • Posts: 561
Explain the purpose of a preplasticizing unit.
 
  What will be an ideal response?

Question 2

How does high crystallinity in a resin affect the way the resin is injection molded, including any post-molding operations that might be done?
 
  What will be an ideal response?



Related Topics

Need homework help now?

Ask unlimited questions for free

Ask a Question
Marked as best answer by a Subject Expert

brittrenee

  • Sr. Member
  • ****
  • Posts: 321
Answer to Question 1

In some operations, chiefly where the melting of the resin is the limiting factor in decreasing the cycle, a second barrel or chamber is added to the injection molding machine. This second chamber is the collection point for the melted resin as it exits from the screw or ram melting unit. The second chamber has a ram injector that can push the melt of resin into the mold even while material is being introduced from the melting unit. The combination of a continuous melting operation and an on-demand injection operation can speed molding significantly in some cases.

Answer to Question 2

Crystallization normally gives materials a sharper melting point. That is favorable in injection molding because it makes the material easier to heat to a uniform viscosity. Furthermore, the crystallinity usually means that the material will cool and solidify more sharply, thus decreasing the time that the material must be cooled. After the part is removed, residual crystallization is common. This continuing crystallization can distort the part. Therefore, cooling fixtures are often needed to ensure that the part will crystallize and complete cooling without part distortion.




PhilipSeeMore

  • Member
  • Posts: 561
Reply 2 on: Aug 19, 2018
Wow, this really help


covalentbond

  • Member
  • Posts: 336
Reply 3 on: Yesterday
Gracias!

 

Did you know?

Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.

Did you know?

Less than one of every three adults with high LDL cholesterol has the condition under control. Only 48.1% with the condition are being treated for it.

Did you know?

In most cases, kidneys can recover from almost complete loss of function, such as in acute kidney (renal) failure.

Did you know?

Your skin wrinkles if you stay in the bathtub a long time because the outermost layer of skin (which consists of dead keratin) swells when it absorbs water. It is tightly attached to the skin below it, so it compensates for the increased area by wrinkling. This happens to the hands and feet because they have the thickest layer of dead keratin cells.

Did you know?

In 1886, William Bates reported on the discovery of a substance produced by the adrenal gland that turned out to be epinephrine (adrenaline). In 1904, this drug was first artificially synthesized by Friedrich Stolz.

For a complete list of videos, visit our video library