Welcome!

note: For more on a DIII process, please read: Rules for a DIII Process

The advent of highly-responsive all-electric injection molding machines is allowing people to control the process in very unique ways to fit a specific situation. Using the cavity pressure at the end of fill to transfer from velocity control to pressure control can be a great way of controlling the amount of pressure which is received within the mold cavity during the mold cycle.

The biggest concern with this approach is the response of the machine. Most hydraulic molding machines lack the response time to facilitate the correctly use of an end of fill sensor. 

-Andy

Basically, the most common affects that arise from screw wear relate to the increased back-flow over the flights of the screw. This back-flow increases mixing, but also lowers material conveyance and increases residence time distribution.

As the screw wear increases, the number of revolutions necessary to recover the shot will also increase… thus resulting in more shear heating, a higher melt temperature, and possible polymer degradation.

Since the melting and conveying properties of the screw become compromised, excessive screw wear can also cause a significant increase in the amount of energy which is consumed during screw recovery.

-Andy

We have 2 different brands of machines. On one brand, the feedthroat temperature is 85-90ºF, yet the other brand has a temperature of 150-190ºF. Is this difference OK…? and could you comment on what effects the higher temperature will have on the process?

Regarding the Machine Differences – In reality, there is no standard convention for feedthroat temperature measurement. Some machines place the transducer near the cooling lines, some place them closer to the rear heater bands. Additionally, some machines will measure the temperature of the water passing through the feedthroat. In your case, the best way to compare the effectiveness of the feedthroat cooling is to use a surface temperature probe to measure the water temperature entering and leaving the feedthroat on both brands of machines.

Regarding the Effects of Temperature – The feedthroat temperature should low enough to prevent the bridging of material. Always ensure the feedthroat does not get cold enough to induce condensation within the feedthroat.

When such a discrepancy exists between two different brands, it is typically caused by differences in design.

-Andy