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Long Hold Times on Electric Molding Machines…

I received this as a follow-up question for a previous blog posting on The Future of Plastics…

Ed
We are adding a new machine this year and we are looking at a electric machine. Our biggest concern with electric is the hold time. Due to our thick wall parts we use extended hold times. Does anyone have any experience using extended hold time with a electric machines?
My Response
In reality, jobs with long hold and/or cooling times are very well suited for all-electric molding machines. In a hydraulic molding machine, the hydraulic pump is always providing significantly more hydraulic fluid flow than is necessary to mold the part. Even when a multiple stage, variable, or servo-driver pump is used, hydraulics are a relatively inefficient method of transferring electric energy to linear or rotary motion when compared to all-electric molding machines. These losses are amplified when you consider the added costs of water for the heat exchanger as well as additional maintenance expenses.
The latest news in all-electric molding machines is almost always focused on higher speeds, tonnages, and pressures intended to get all-electric molding machines into newer markets such as packaging and automotive where profit margins are razor-thin. As a result of this hype about the latest and greatest, the molding companies take for granted that the average injection molder already knows all the general benefits and how it applies to their own operation.
Additional Thoughts
Industries such as robotics and automation are doing a good job in teaching the consumers about the benefits of servo-motor driven components. Many molders are replacing simple items such as pneumatic sprue pickers with high-efficiency servo-motor drive versions. When I hear molders tell me things like “I’d get an electric machine if I were doing more automotive” or “My cycle times are too long to justify an electric molding machine” it shows that the industry should return to the basics and teach it’s potential customers more about the fundamental benefits of all-electric molding machines.
We recently created a series of training programs focused on all-electric molding machines to help educate molders about the functionality, benefits, and optimal processing of all-electric molding machines
-Andy

Company-Specific Training…

Recently, a potential customer mentioned this comment…

Caller
I like the idea of training my employees about extrusion, yet I need something specific to my operation and I don’t have time to create it.
My Response
First off, generic extrusion training is always better than no process training at all. As one of our customers called it, “It gives them a plastics frame of mind”. In most cases, supplemental systems such as on-the-job training materials can be created very easily, and most online training systems can be customized and modified easily.
Additional Thoughts
It is always better to train your employees than not train them. Whether it teaches fundamentals, or company-specific details… it helps provide the information necessary for critical decisions making.
-Andy

Can Low Melt Temperature Cause Flash?

Yesterday, I was asked this question…

GH
My tech told me that we were getting flash as a result of a low barrel temperature. An increase in barrel temperature fixed the problem, but I don’t know why, could you explain?

My Response
It may seem counter-intuitive, but flash could be the result of a low melt temperature or a high melt temperature.
If the temperature of the melt is too low, the viscosity will increase and the pressures required to fill the mold may be too high. This high pressure can exceed the clamp tonnage resulting in flash near the center of the mold or near the gate.
If the temperature of the melt is too high, the melt viscosity will drop – especially if the material degrades. This drop in viscosity may allow too much material to enter the mold during 1st stage fill, resulting in flash. A decrease in melt viscosity may also cause the material to flash during 2nd stage packing.
Additional Thoughts
Keep in mind, the focus should be on the actual melt temperature, which is a process output, instead of barrel temperature settings, which is a process input.
-Andy

Plastic vs. Plastics…

While consulting, a technician asked me this question yesterday…

John
I’m confused, are we making parts out of ‘plastic’ or ‘plastics’. Which is correct? What is the difference?

My Response
The word ‘Plastic’ refers to something which is flexible or malleable. Although most synthetic polymers are flexible, there are a many materials which also have these properties including lead, butter, clay, and beeswax.
The word ‘Plastics’ refers to polymeric materials… these can be synthetic or natural, thermoset or thermoplastic, and semi-crystalline or amorphous.
Additional Thoughts
In the industry, the two terms are used almost interchangeably. Much of the industry literature has completely ignored the difference between the two since few people actually know the difference between the two term. I have used the word plastic in place of plastics because it reads better in many cases. For example, ‘The best plastic for the application is ABS‘ reads better than The best plastics for the application is ABS’.
-Andy

Don’t Give up on Your Employees…

I received this in an email from a technician at a very busy blow molding company…

Lori
I talked to my company and they said they do not need any training. I have been on the job for four months and I still do not have the basic concept of how to process plastic. At this point I’m very discouraged, frustrated, and ready to give up.

My Response
Your company is quite fortunate to have an employee like you that wants to learn and do the best possible job. Our industry needs more people like you. (the remainder of my advice was specific to the person)
My Concerns
I correspond with people such as this all the time. Most employees want to do a good job, but they must be given the tools necessary to perform their jobs well. In most cases, people like this end up leaving the company they are working for. They either find a company willing to support their desires to learn, or they leave the industry all together in search of a field which will satisfy the thirst for knowledge and growth. It is my opinion that companies should hire eager & ambitious employees and provide an environment that allows such people to grow… this is the best way to position your company to best handle the challenges that lay in your future.
-Andy

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