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.

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.

Is P-20 An Adequate Steel For Glass-Filled Nylon?

In a recent e-mail, I received this question regarding tool steel…
Kevin W.
Is P-20 an acceptable steel material to hold up to 60,000 annual volume for 10 years. The material is 15% glass fill nylon with 25% talc fill?
My Response
By itself, P-20 lacks the wear resistance to produce half a million cycles using a glass-filled material. A coating of titanium nitride on both the core and cavity should prevent wear on the P-20. Additionally, this coating is gold in appearance… so wear will be easy to identify when more coating is necessary.
Since the gate is a high shear location, it typically receives the most wear. I strongly recommend using a hardened gate insert to avoid welding and repairs in this area. Likewise, if you are using a hot runner gate, you should use a hardened drop rather than machining the gate into the P-20 cavity block.
The biggest caveat to this recommendation is thin wall molding. If the part has thin walls, or requires high injection pressures… P-20 is not likely to maintain its structural integrity for 600,000+ cycles.
Additional Thoughts
Without knowing more about the application and your tool steel supplier, it is hard to recommend a specific tool steel. Depending on availability and price, there are often multiple steels that will suit your application. A good supplier should be able to review your application with you and recommend a metal that will meet your specific needs.

12 – The Elements of Great Managing

Recently, I have read a great book entitled ’12 – The Elements of Great Managing’ by Rodd Wagner and James K. Harter. In this book, the authors discuss the twelve simple concepts managers use to create quality employee experiences. I highly recommend that any manager adds this book to their summer reading list.

In this book, there is a great amount of relevant information but I wanted to mention the twelfth element – which is to provide ‘Opportunities to Learn and Grow’. As you know… people resist change. In this book, the authors make the argument that they feel that monotony is even worse than change – talk about a catch-22!
I bring this up because, any manager needs to create an atmosphere where their employees can learn and grow. Don’t just give your employees educational opportunities, but also familiarize them with the jobs of others and those around them.
In actuality, if you treat your employees professionally… they will act professionally. Adversely, if you treat your employees like mindless drones… you will not get the best out of your workforce. Always keep this in mind when you move forward with your workforce development initiatives.

2nd Stage Time vs. 2nd Stage Pressure

During a recent webinar, I received this great question…

Webinar Participant
Do you recommend running at different pressures when performing gate seal studies?

My Response
You should first determine the optimum pressure using a relatively large 2nd stage time. This allows you to determine the actual amount of pressure that is required to pack and hold the part. Afterwards, determine the optimal 2nd stage time – once the pressure is established.

Additional Thoughts
Many people overlook the relationship between 2nd stage time and 2nd stage pressure (pack and hold combined). 2nd stage pressure is used to pack out the part and prevent back flow until the gate seals. In comparison, 2nd stage time should only be used to allow enough time for the gate to freeze.


Humans are Creatures of Habits

Yesterday, someone asked me my opinions on day-long training sessions…

I said they are good, but lack the effectiveness of long-term training initiatives due to human nature. Unfortunately, it takes at least three weeks of training and reinforcement to dramatically change a person’s behavior.
What it comes down to is the fact that humans are creatures of habit. You drive to work using the same route, have a cup of coffee or tea, check your e-mails, update your schedule, etcetera. If this sounds like you… then you are also a creature of habit. The point is, behaviors are hard to change. Some mornings you have a meeting at a different time, or have to drive a different way to work, but you tend to go back to your habits.
Don’t get me wrong… classroom training sessions are great, but they have their place. Such training is best when used to expose employees to new ideas and concepts. They also make a great motivator, especially if your workforce has become complacent and needs a ‘pick-me-up’. To get the most out of such a situation, classroom training should be backed up by in-house training, focused on-the-job exercises, and skill development.