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.

Cushion Monitoring: Variation & Setting Limits

One of our more advanced customers just asked these questions…

Jim M.
Monitor the shot-to-shot variation (cushion)… if it is not consistent, can I increase the back pressure?

What tolerance should I be able to hold on cushion, e.g. I am hitting 0.20” cushion, what should I be expecting to repeat, i.e. what min & max. on the alarm?

Our Response
If the cushion is varying greatly from shot to shot, then back pressure may be an issue.
The cushion will vary over time…and many companies will set a variation of approx. +/-5% of the material used to fill the mold.
An example would be this:
Overall shot size = 110mm
Target cushion = 10mm
Material used = 100mm
Upper cushion limit = 15mm
Lower cushion limit = 5mm
Additional Thoughts
The purpose of a cushion is to give your process the breathing room it needs to compensate for material variations so the screw does not bottom out. It’s similar to keeping a safe distance between your car and the car in front of you in traffic to compensate for variations in traffic and one’s response time. This acts as a buffer to prevent a wreck from happening.

If You Teach a Man to Fish…

A good friend of mine offered up this excerpt from a recent company newsletter…

Ron Z.
“….if you teach a man how to fish, you feed him for life.” This adage is the very essence of training. The reason some managers or supervisors get drained is because they don’t delegate. They don’t delegate because they feel they don’t have anybody to delegate to who’s adequately trained or maybe… it’s job security. Either way, training is vital in any organization especially if you or anybody wants to move up within. If you don’t train somebody under you to take over, you’re not going to move up. You need to train somebody to replace you. Did I say, “Getting Replaced?” Yes, I did. It’s scary, I know, but think about it. Unless, there’s somebody available to take over what you’re doing, whatever organization you’re working for will keep depending on you to keep on doing the same thing you’re doing right now and probably forever.
Additional Thoughts
Ron has some great points on how critical it is to create a cue of knowledgeable and capable employees in your workforce. Once you train your employees to where you wish them to be… you should then make advancement training available. Your intent is to create a cue of people waiting to advance professionally. You encourage this in many ways. For example, the first person trained for the job can be eligible for the promotion. They can also fill in when someone is sick or goes on vacation. This reduces much of the stress in the workplace.
Many forward-thinking companies are adopting a policy that each employee should have someone learning to perform their job, as well as be training themselves for another job. Their performance reviews are partially based on both their progress as well as the progress of their protégé.

Great Books for Managers and Facilitators

Here is a list of recommended books that are great reading for managers and facilitators…

Please feel free to comment with other books you feel apply.

Developing Employees Who Love to Learn
Tools, Strategies, and Programs for Promoting Learning at Work
By Linda Honold
Published By: Davies-Black 2000
Strategies for Delivering Knowledge in the Digital Age
By Marc J. Rosenberg
Published By: McGraw-Hill 2001
The AMA Handbook of E-Learning
Effective Design, Implementation, and Technology Solutions
By George M. Piskurich
Published by: AMACOM 2003
The ROI of Human Capital
Measuring the Economic Value of Employee Performance
By Jac Fitz-enz 
Published by: AMACOM 2000
Trainers in Motion
Creating a Participant-Centered Learning Experience
By Jim Vidakovich
Published by: AMACOM 2000
Leadership Lessons from West Point
Teaches valuable lessons from a military perspective.
By Major Doug Crandell (Ed.)
Published By: Jossey-Bass 2006
12: The Elements of Great Managing
Creating and sustaining high quality employee experiences.
By Wagner Rodd, Harter James K.
Published By: Gallup Press 2006

Dynamic Check Ring Repeatability Test

One of our more advanced customers brought to us this observation…

Jim M.
It is interesting that this test does not utilize the pack & hold portion of the cycle; just the fill portion.  Experience shows, especially with high 2nd stage pressures, that the screw will drift, and some reflection of that would be a good indication of check ring holding.  Your thoughts…?
Our Response
Every check ring will leak and drift. What is most important in maintaining a consistent fill is the repeatability of this leak. The Dynamic Check Ring Repeatability Test is intended to measure this variability in this leak during fill. In most cases, if the drift is variable during 2nd stage, it will also be variable during fill. Although each process is different… if the screw does not bottom out, and cushion varies less than 5% of the overall shot size from shot to shot, usually the amount of drift is not a major factor.
Additional Thoughts
It is always great to hear someone asking such highly technical questions because it means they are focusing on the finer points of processing rather than subjects of general knowledge.