Welcome!

The most common defects we encounter are flash and short shots. I would think that these two defects would be complete opposites, so why do we always see both?

I agree that these two defects sound mutually exclusive… the part has too much material with flash, and too little material with short shots. Surprisingly, when these two defects are seen together… it often indicates a poorly established fill, and I’ll explain why.

When establishing a molding process… If the part is completely full during first stage, then the process cannot compensate for variability. A drop in material viscosity will cause too much material to enter the mold during fill, causing flash. A rise in material viscosity will cause too little material to enter the mold cavity, causing shorts. 

When the process is established with a short, then 2nd stage pack is used to fill out the part. any typical variation in viscosity during fill will then be compensated by pack.

The most solid and reliable processes are short during first stage fill… and then packed out during second stage.

-Andy

Such bushings are a great option for the longevity of your tooling. These demonstrate significantly less wear when compared to regular brass or steel bushings.

The only drawback to this option would be with your tooling maintenance department. If they have not used such a system, they should communicate with the manufacturer to ensure they understand the operation and maintenance of such bushing systems.

I always recommend spending a little extra money for the better leader pin bushings. The price might be a little higher, but the long term value far outweighs the initial cost.

-Andy

Regarding eDart Technology… Let me explain a few points for my readers.  In my experience, such technology is best implemented for one of two reasons… 1) to detect and isolate specific part defects such as short shots. 2) to accurately control the transfer from 2nd stage pack to 3rd stage hold using cavity pressure measurements. In both these situations, the mold must be properly instrumented with pressure sensing technology… and your employees need to be trained on the use of such technology before implementation. The learning curve for this technology is steep… so be sure that all your employees have a firm grasp on the fundamentals first.

Regarding Your Question… Based on your line of questioning, my assumption is that you are asking if the eDart will help compensate for the complications arising from running less than 20% machine capacity. A machine running below 20% capacity typically has a residence time of 10 cycles or more. For this reason, the inherent complications resulting from a long residence time such as degradation, property loss, and presence of volatiles will not be affected.

If these were my machines, I would invest in new screws and barrels for the machines before I bought anything else. My approach to technology is as follows… Don’t purchase the latest and greatest until you are 100% sure that 1) your employees are getting the most out of the your equipment, and 2) it will make a significant difference.

With your improperly sized screw and barrel… It is like putting a turbo charger on a car which has a flat tire.

For more information on proper barrel sizing, please read the following entry:

-Andy