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ms. student Member Posts: 2 |
posted August 22, 2004 08:43 AM
  
hi! I am an IE student. my thesis is about quality control in plastic extrusion. I really need help in further understanding the extrusion process and its defects. I need information about the causes and solution for defect types such as color deviation, pinholes, uneven thickness and unsquared sheets. If anyone could give me solutions on preventing such defects, it would really really help me. I would really appreciate anyones help because I am having a difficult time understanding the technicalities of the process...Thanks IP: Logged |
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Tom C Moderator Posts: 360 |
posted August 22, 2004 09:45 AM
Dear MS Student, I feel some connection to your question as I have a BSIE, lots of extrusion experience, and some QC background. First, how do I say this nicely? You have bitten off way more than you can chew. Extrusion is a fairly complex non-linear process involving chemistry, changes in phase, mechanical considerations and lots of fluid flow issues with non-newtonian fluids. Quality control involves defining what is "normal", determining whether "normal" meets the product requires, and then monitoring the process and product to determine whether "normal" is being produced. If the product is determined to not be "normal", then corrective actions are required. Additionally QC can include actions to improve the state of "normal". Becasue of the prior mentioned multitude of process aspects, it is often very difficult to determine the reason "normal" is not being made in extrusion. Add to that the fact that there is usually significant variation in the starting condition of raw materials (chemical properties, viscosity, particle size, moisture content, and temperature) there may be a complex interaction of the process with any change in the raw materials. As you can see the universe of extrusion problems and solutions to those problems can be quite large. I would suggest picking one quality issue and focusing on that, for example film thickness. There is plenty of information out there about measurment and control techniques. Film thickness is a little more straight forward than some of the other QC issues you proposed. My email address can be found at the top of this message. Tom Cunningham IP: Logged |
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ms. student Member Posts: 2 |
posted August 22, 2004 01:49 PM
Dear Mr. Tom C, Well I would just like to thank you for responding. At least now I have an idea on what aspect I should focus on. I am so clueless with the technicalities. I do understand the process. But I'm really overwhelmed with the amount of information I have been able to collect from researching. Most of time I'm not able to understand it. With film thickness, what are the possible causes? From what i understand so far, it is probably caused by wrong die adjustment. But I'm trying to look for a more specific causes. I'm so sorry if my "ignorance" is really annoying. I just need a more simple explanation and I'm not getting it in any book or web site.I hi\ope you wouldn't mind further answering my questions. Thanks, IP: Logged |
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Tom C Moderator Posts: 360 |
posted August 22, 2004 03:43 PM
I'm a little perplexed by your answer. I have 25 years of extrusion experience and $250,000 worth of extrusion simulation software and I feel as if I'm just beginning to have some understanding of the extrusion process. Perhaps you will have more luck. Tom C IP: Logged |
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zabielski Senior Member Posts: 328 |
posted August 24, 2004 07:01 AM
ms. student: Seems to me that you should first study the extrusion process before doing anything else. You want simple answers for a complex subject, and don't seem to want to settle for anything less. Me thinks you ought to perhaps change your Major to pyscoanlysis. IP: Logged |
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Steve H Moderator Posts: 311 |
posted August 24, 2004 05:04 PM
Ms, Tom has pretty much laid out what you are getting into. If you want to get a handle on film extrusion, get a hold of TAPPI's Film Extrusion Manual, www.tappi.org (it's about $125), I'd also search every resin makers site for blown film extrusion guides and troubleshooting guides. Try getting an internship with a company extruding blown film. Steve [This message has been edited by Steve H (edited August 24, 2004).] IP: Logged |
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