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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.

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Crystallinity In Layman’s Terms

In a recent e-mail, I received this question regarding crystallinity…
Sam A
Can you explain Crystallinity in layman’s terms? Also how the process affects it.
My Response
In essence… crystallinity is a phenomenon where segments within the polymer chain either (1) align themselves in an orderly, structured fashion or (2) align themselves with portions of adjacent polymer chains in a similar fashion. These semi-crystalline structures tend to improve properties such as strength, barrier, and impact.
These semi-crystalline structures do not exist when the polymer melt is above the melt temperature. As the polymer temperature drops below the melt temperature, these semi-crystalline structures begin to form. The faster the polymer cools, the fewer semi-crystalline structures appear. Likewise, the slower a polymer cools, the higher the degree of crystallinity within the polymer.
One if the biggest factors regarding crystallinity is dimensional stability… Since semi-crystalline regions are more dense than the polymer in the amorphous state, higher degrees of crystallinity create higher shrinkage. The more even the cooling, the more even the shrinkage, and therefor the more dimensionally stable the part will ultimately become.
Additional Thoughts
Keep in mind, the same principles apply to both extrusion and blow molding. Ultimately, any process change that increases melt, mold, or die temperature will decrease the rate of cooling… resulting in an increase in crystallinity. This is one reason why it is always important to think twice before making a temperature change in your process.
-Andy

The Science Of Training – An Executive Audiobook

New Executive Audiobook:
I have just released an audiobook on professional employee development entitled ‘The Science of Training’.
You can listen to it here:
You can also download it here:
Sample Excerpt:
Just to give you a taste of what is covered… Below is a short transcription from the middle of this executive audio CD:
Many companies also make the mistake of training only their “key employees.” You know the people I am talking about… these are the go-to-guys and gals at your plant on whom you rely to get everything done. While these few ‘key’ employees may become much more knowledgeable than their co-workers, this disparity could trigger some negative tensions. Also, the production personnel get into the bad habit of always running to the ‘go to guys’ to get things done – instead of solving the problem themselves.

In reality, these people are relied upon again and again because they are reliable. I have spoken with employees who have gone for three and four years without taking a vacation. I bring this up because you have probably heard, or even said the phrase… ‘If I train them, they will just leave’. Well, if you just train your key employees then they will leave. The reason is… you are sending the message of… ‘I want you alone to learn this, implement this, and add this to your overwhelming list of stuff you already have to do’.
As always, feel free to give me your feedback and comments.
-Andy

Remedy For A Walking Machine

In a recent trade show, an attendee asked me this unique question…
Attendee
What would cause my machines to ‘walk’? The floor is level, but a couple of my machines will still move.
Note: For those new to the industry, a ‘walking machine’ physically moves away from the original position where it was installed. This movement may be as little as a couple millimeters or as much as a few inches.
My Response
First, always level the machine by placing the level on the tie bars. Always make sure you check all 4 tie bars. Many people make the mistake of levelling the machine by the base of the platens. Some of the best systems use a rotating laser with a group of sensors placed on the tie bars to measure the tie bars relative to each other. 
Second, check the parallelism of the platens. This can be easily measured both when the mold is open as well as when the mold is closed. The best way to check this is to have an expert come in and use a computer assisted system which can accurately measure the parallelism, twist, linearity of the platens at rest, under tonnage, as well as during platen movement.
Third, check the lubrication system. Any busted or leaking seals, as well as blocked lubrication lines may cause abrupt movement of the platen. This is often evidenced by a series of rings or streaks on the tie bars. You may also feel a vibration when touching the machine as the mold opens and closes.
Additional Thoughts
Over time, ANY awkward platen movement that is not linear and level may cause the machine to ‘walk’. This can become very costly as it can often cause tie bar strain, platen twist, and uneven clamping. You must implement a routine schedule for checking the levelness, parallelism, and lubricaion of the machine, since any of these can cripple or ruin your molding machines.
-Andy

Are Trade Shows Good For Your Employees?

Over the years, I have seen a significant decrease in production workers at trade shows such as the most recent NPE. For those who may never think to send their employees to trade shows, I would like to provide a few resons why it can be helpful to you.
The Plastics Industry
Most employees think of themselves as just an employee at a company that makes cases, bottles, buckets, cases, bags, pellets, etc. As a result, they approach their job with the zeal of a clerk. Sadly, most people working in the plastics industy never realize there is a plastics industry!!!
Industry Appreciation
Although employees may not learn skills that will directly relate to their job, they will realize that they are a part of a much larger industry. Giving a person the opportunity to meet representatives from material, machine, and equipment suppliers…  provides a great appreciation of the plastics industry.
Accepting Responsibility
This is not the time to wine and dine your employees with excess. The atmosphere can be fun and friendly, but it should also remain professional. Always delegate some responsibility to your employees… It keeps their focus and may give you a whole new perspective.
Let’s suppose you are evaluating a few different machines for purchase… You may ask your technicians to evaluate the controls while you concentrate on the specifications and costs. In your review, one brand of machine may have the best cost and specifications, but your technicians find the machine controls confusing, thus anticipating push-back from their fellow employees. With their feedback, you may choose a machine with similar benefits, but with the added benefit of your technicians returning to the plant with rave reviews… resulting in a sense of excitement and anticipation for the new machine. This small insight such as this can easily return the investment of the trip.
Increasing Morale
Ultimately, such activities foster a sense of appreciation and good will for your company. If you open your employees’ eyes to the plastics industry and give them a participatory role, they will be grateful for the opportunity.
-Andy

Water Condensation and Mold Sweat

In a recent e-mail, I received this question regarding mold sweat…
Altaf B
When we set the water chiller temperature at 10ºC or less, we get water condensation on the mold cavities. Could you help us avoid this condition?

My Response
Mold sweat is condensation which appears on the mold. Water condenses on the mold surface when the mold temperature is lower than the dewpoint of the air.
The dewpoint is the temperature at which water precipitates out of the air in tiny droplets. This vapor can collect on the surfaces of the mold. To reduce condensation, the mold temperature can be increased, or the dewpoint or temperature of the surrounding air can be decreased. 
Another way to decrease the dewpoint is to control the climate in the molding area. Blowing dehumidified air at the mold reduces the dewpoint…which lowers the possibility of condensation.
Additional Thoughts
In reality, it’s always advantageous to control the temperature and humidity in the molding environment. Not only does this help prevent mold sweat… this also reduces material and process variations as well as improve the overall working environment for your employees.
-Andy

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