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Transmittance in molded plastic parts
02-02-2014, 05:48 PM
Post: #1
Transmittance in molded plastic parts
Hello everyone,

I have been working on bringing thermal imaging into our injection molding facility. It's been on my project list for a long time but has either been cost prohibitive or I was not in an appropriate role for developing the system. All things have aligned and I have begun the process of getting key team members certified and collecting baselines for comparison later on. It's become a truly large task because everywhere we look we are seeing different potential applications. We have narrowed our focus at this time to PdM and in process monitoring of the molded parts for defects which will eventually be used towards the goal of parametric release of final goods.

We currently use a large amount of HDPE in our mix of parts that we mold so it seemed like a good place to start in identifying potential areas for improvement with infrared imaging. It didn't take long to notice that the HDPE was transmitting a lot more IR than we had expected. This problem was compounded by its level of transmittance varying during each stage of cooling as the crystallinity of the polymer increased. It has been suggested that a filter specifically designed for HDPE would be the best route and is something that I am looking into but I wanted to check here for advice on alternative ways of combating transmittance. For instance, our parts are all removed from the mold using robots and could be placed anywhere for the IR camera to image. This could be on a surface with a known temp that could be accounted for in the software. This is just one idea I have come up with but I'm sure there must be others.

Purchasing a filter for HDPE could be justified due to our large volume of parts using this polymer but on smaller, low volume jobs running a variety of different engineering grade polymers it would not be practical to purchase a lens for each one. What would the best approach be when inspecting such a wide assortment of polymers?

We had been initially using a handheld model from Testo but recently purchased a Flir A315 for process improvement R&D. I was at the plant working on setting up the external camera trigger on one of our machines and grabbed a screen shot of a few of our parts that show the problem. On the long vertical portion the wall thickness is so low that the plastic is almost invisible compared to the steel temp inside of it and only on the really thick handle portion are we able to get a "good" reading.

   

Any advice would be appreciated. Thanks.
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Transmittance in molded plastic parts - ArikB - 02-02-2014 05:48 PM

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