Plastics Training & Technology Blog tag:blog.traininteractive.com,2009-05-03:/plastics_training_technology_information//4 2012-05-14T19:43:31Z This informative blog is a location for plastics professionals to communicate, discuss, and comment on Plastics Training & Plastics Technology. To comment, click on a topic and choose the 'Leave a Comment' option at the bottom. Please email blog@traininteractive.com or call (978) 957-0700 to open up a new discussion. Movable Type Pro 4.25 Understanding Jetting... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.374 2012-05-14T19:45:00Z 2012-05-14T19:43:31Z I was asked this question the other day when discussing molding defects...StudentWhat actually causes Jetting?My ResponseThis defect occurs when the polymer shoots into the mold and does not create a smooth laminar, or fountain, flow as it first enters the... Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2
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...? tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.373 2012-05-10T19:40:00Z 2012-05-10T19:38:34Z I was asked this question by a student the other day...BobCan you please define Micro-Molding?My ResponseI have seen this defined as small parts around 1 milligram or less. In practice, I have seen it refer to parts much larger than... Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2 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... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.372 2012-05-08T13:55:00Z 2012-05-08T13:52:21Z I was asked this during NPE...ManagerMy 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 ResponseRunner technologies which balance the shear... Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2
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... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.379 2012-05-02T14:05:00Z 2012-05-02T14:06:37Z Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2
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


]]> Verifying a Consistent Silicone Process... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.377 2012-04-27T17:12:28Z 2012-04-30T13:14:28Z I was asked this question the other day...Quality ManagerWhat is a good way to ensure a silicone molding process is consistent?My ResponseOne good way to check the consistency of the process is to routinely measure the part weight. A consistent... Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2
Quality Manager
What is a good way to ensure a silicone molding process is consistent?

My Response
One good way to check the consistency of the process is to routinely measure the part weight. A consistent part weight indicates the same amount of material is injected and packed each cycle. This wont necessary tell you what is wrong or has changed, but will be a good indicator of process shift.

-Andy
]]> Differential Cooling... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.370 2012-04-25T20:40:00Z 2012-04-25T20:43:22Z I was recently in a discussion with someone who was heavily involved in a molding trial...EngineerWe just went through a series of trials to reach the correct molded part dimensions on a part, and it turned out we needed to... Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2
Engineer
We just went through a series of trials to reach the correct molded part dimensions on a part, and it turned out we needed to use four different temperatures to achieve this. What mold cooling information should we be documenting for this?

My Response
Regarding the mold cooling, you should first have a detailed diagram of the cooling line/themolator layout. This diagram should document the coolant temperature entering and leaving the mold for each temperature profile. Over time, you should consider adjusting the tooling to accommodate these complications.

-Andy
]]> Spiral Flow Test for PP... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.369 2012-04-23T15:45:00Z 2012-04-23T15:43:48Z Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2
YM

Is there any standard (ISO or ASTM) that can be reference for a polypropylene spiral flow test?


My Response

Yes, there is a standard for this within ASTM D-4101. If you are looking to publish the results, then this can be very helpful. Unfortunately, the conditions, flow rates, and pressures used may not directly replicate your processing conditions. In practice, most of the companies I have dealt with create their own procedure based on the conditions of their process.


For example, if they are looking to compare the viscosity of two grades of material. they might replicate the melt temperatures and flow rates of the actual product, and measure the difference in pressure at transfer to represent viscosity.


Another company I have worked with uses many older, pressure-controlled, molding machines. This company uses a constant pressure with position transfer. The change in injection time and flow distance provides excellent information for comparing one material grade to another.


Additional Thoughts

Basically, I recommend you review the standard procedures for the spiral flow test, but adjust the test parameters to meet the specific needs of your production facility. The key factor is to perform a test which provides information which helps the production department.


-Andy



 


]]> Restarting Your Training... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.368 2012-04-19T16:25:00Z 2012-04-19T16:21:23Z I was approached during NPE the other week by a manager...ManagerWe used to do On the Job training, but now we do nothing for our employees. How do we get started again?My ResponseThe first step is to start training, even... Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2
Manager
We used to do On the Job training, but now we do nothing for our employees. How do we get started again?

My Response
The first step is to start training, even if it is something as simple as cross training. For example, you could have a technician assist in some mold PM's to learn more about tooling.

Your employees will never get into the mindset if you never do any training. Employees want to do a good job, but they need the necessary intellectual tools to succeed.

Additional Thoughts
I understand that there is much more to effective plant-wide employee development than this, but any training is better than no training at all... and you have to start somewhere.

-Andy
]]> Part Sticking and Machine-Independent Documentation... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.365 2012-04-16T15:00:00Z 2012-04-16T14:59:25Z Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2
Issue
The mold has run without issues for years. Now the parts stick in the mold almost every shot, there is more flash, and the cushion is much lower than recollection. All the machine and temperature settings are the same, but the result is much different. Could this be a check ring issue?

My Response
The check ring is more commonly an issue if the sticking is intermittent… which this seems not to be the case. My initial suspicion is that there is too much material being injected or packed into the mold. Second, the mold or melt temperature might be higher than usual. There are a wide host of items which could contribute to this problem... but investigating these first might give a good idea as to the cause of the defect.

Additional Thoughts
This could also be chalked up as a documentation issue. Since we don't know the melt temperature, 1st stage fill time, part weight, or other machine-independent parameters during the good runs, we cannot quickly identify 'what changed' between then and now. 

If you or anyone you work with would like to learn more about process documentation... we have some free multimedia webinars on scientific molding which can be viewed at http://www.traininteractive.com/free/webinar/player/

-Andy
]]> Rule of Thumb for Packing... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.354 2012-04-11T13:10:00Z 2012-04-11T13:10:03Z Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2
JH
What is a good rule of thumb for second stage packing?

My Response
In the old days of pressure-controlled injection molding machines, the first stage pressure was used to completely fill the mold slowly while a lower pressure (approx. 40-60%) was used to compensate for shrinkage while waiting for the gate to freeze.In the newer machines, if the mold is completely filled during first stage, then the old 40-60% rule of thumb is often applicable.

If a scientific or decoupled type of process is being used, where the mold is not completely filled during first stage, then there are many factors which play into the final second stage packing pressure. Essentially, the only rule of thumb is to select a pressure which produces an acceptable part. The first stage injection pressure should have no bearing on the second stage packing pressure. I have seen thick parts using second stage packing pressures as low as 25% of the pressure at transfer, and I have seen thin-walled parts use as much as 125%.

Additional Thoughts
The fundamental underlying basis of good injection molding is to separate mold filling from mold packing. This means you should first establish a good fill, and then establish your part packing.

-Andy
]]> Training Certificates... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.361 2012-04-09T17:25:00Z 2012-04-09T17:23:02Z Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2
Manager
Two of our techs recently received training certification, but I don't see any real change between them and the other technicians.

My Response
Most certifications are based on the participants ability to pass some tests in a class setting. This process is beneficial in introducing new techniques and ideas to the employees, but seldom helps in changing the employees behavior. Most experts believe it can take many months to effectively change behavior. As a result, you must implement a broad reaching approach to training which not only teaches the new concepts, but reinforces the correct behavior over time.

Additional Thoughts
In the case of plastics processing, the employee needs to know how to process, practice the knowledge, and have the right processing and troubleshooting techniques reinforced by those in the workplace.

-Andy
]]> NPE 2012 Passes... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.362 2012-03-29T13:50:00Z 2012-03-29T13:46:44Z Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2 http://www.npe2012guest.org/?e=314

For more about NPE2012, please visit: http://www.npe.org/

-Andy
]]> MFI and Regrind... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.367 2012-03-28T13:25:00Z 2012-03-28T13:26:05Z This question arrived as a follow-up question to a recent post...NMI am new to the business and an independent broker. In automobile parts (I deal with travel trailers, RV's, automotive and such) does MFI make a difference? Recycled or virgin?... Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2 This question arrived as a follow-up question to a recent post...

NM
I am new to the business and an independent broker. In automobile parts (I deal with travel trailers, RV's, automotive and such) does MFI make a difference? Recycled or virgin? We are trying to cut costs, and it seems a lower MFI and recycled product is cheaper.

Regrading MFI
MFI is essentially a measurement of how much of a particular material flows through a capillary under a given load during the course of 10 minutes. The stresses and shear rates present in this test are not indicative of most plastics processes. If you want more comparative data you can acquire rheological data from the manufacturers... or request samples and actually preform some comparative rheological tests using your actual production equipment.

Regarding Regrind
You always need to first determine whether the use of regrind poses a liability issue with your customers. You should determine the relative quality of the regrind. Depending on the application, you can choose from a wide range of Rheological, physical property, and performance testing methods.

Some related posts on rheology and physical properties:
]]> Create a Training Portfolio... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.360 2012-03-26T14:10:00Z 2012-03-26T14:07:32Z Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2
Building a Training Portfolio
Every time your employees complete a step in their training plan or make an advance in competency, it should be documented and retained by the employee. We suggest that you create a personalized binder that the employee can use to store items such as training certificates, worksheets, training aides, photographs, and documents. The intent is to create a personal portfolio which the employee can use to demonstrate not only what they learned, but what they have applied.

-Andy
]]> NPE 2012 West Hall, Booth #472... tag:blog.traininteractive.com,2012:/plastics_training_technology_information//4.363 2012-03-22T13:15:00Z 2012-03-22T13:10:26Z Andy Routsis http://blog.traininteractive.com/mt/mt-cp.cgi?__mode=view&blog_id=4&id=2 NPE 2012, please visit us at Booth #472 in the West Hall.

Stop by to discuss training, technology, plastics, or anything else you wish to review.

At our booth, you can also pick up your free copy of our new pocket guide entitled:
'The Injection Molding Reference Guide'

I also recommend you take advantage of our free passes (a $120 value): http://www.npe2012guest.org/?e=314

-Andy
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