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This informative blog allows plastics professionals to discuss plastics training and technology. Brought to you by Routsis Training: the plastic industry's premiere training provider.

The Importance of Timeliness…

A manager spoke with me the other day about training and asked this question…

GM
We recently had a processing problem which cost us a large amount of money. I want to address this is one of our weekly meetings, but am not sure if we should talk about it right away, or wait for the dust to settle.

My Response
Processing issues should be addressed in a timely manner… but they should always be used as constructive teaching moments without any blame involved. For instance, if the issue occurred because the polymer temp was too high and was not noticed, you should use it as a teaching moment to discuss the importance of measuring the actual melt temp.
Additional Thoughts
If there was a procedural violation by a single employee, then it should be addressed privately. If it is an oversight common to many of the employees, then you can use the timeliness to reinforce the importance of the procedure.
-Andy

Understanding Jetting…

I was asked this question the other day when discussing molding defects…

Student
What actually causes Jetting?

My Response
This defect occurs when the polymer shoots into the mold and does not create a smooth laminar, or fountain, flow as it first enters the mold cavity. A laminar flow occurs when the polymer enters the mold cavity from the center, spreads out to the edges of the mold surface to allow more material to enter through the center. In the case of jetting, the polymer streams into the mold cavity and shoots forward like a cylinder of polymer with the first polymer to enter the mold continuing towards the opposite wall rather than spread to the nearest wall. 
Additional Thoughts
Jetting, non-laminar flow, can be caused by one of three major factors:
Low Material Temperature
High 1st Stage Injection
Poor Mold Design

-Andy

What is Micro-Molding…?

I was asked this question by a student the other day…
Bob
Can you please define Micro-Molding?

My Response
I have seen this defined as small parts around 1 milligram or less. In practice, I have seen it refer to parts much larger than that… The aspect that seems to differentiate micro molding vs. small commodity molding is the tolerance, application, and fine detail. For example, a gear or motor housing with extremely tight tolerances might be considered ‘micro-molding’ even if it significantly heavier than 1 milligram.
-Andy

Radii in Runners…

I was asked this during NPE…

Manager
My guys want me to look into the ‘shear balancing’ runner technology while I am here… Is this stuff worth it, or do radiused runners work just as well?

My Response
Runner technologies which balance the shear imbalance within the runner system and are invaluable in helping to minimize cavity imbalances. Tricks such as radii runner intersections might improve the imbalance, but I have seen enough proof to know that shear balancing is the most effective method of correcting for runner imbalance.
-Andy

Robotics at NPE…

At the recent NPE I noticed an emphasis on robotics…

Simplifying Robotics
There were many great advances to the programming and interface systems for robotics. Each advancement in simplifying the programming of robotics will improve the learning curve for a setup technician. One manufacturer even demonstrated the ability to have the robot mimic manual physical movements of the operator in real time.
Multi-Function Robotics
With the extensive advances in the speed of robotics, there is a large amount of time that exists between the moment the robot removes the part from the mold and when it is needed again. At this NPE, there was a strong emphasis on multi-function robots which take advantage of their speed by performing multiple trimming, inspecting, and assembly tasks in between cycles. Molders who can take advantage of their robots capabilities between cycles will save time and money over the log time.
-Andy