As stated in one of my earlier blog posts, I have begun a new series on injection molding processing. I want to share a bit of this with you in order to get you to stop by and see what's new in this section of my website. Here's an excerpt on the latest addition to my site.
Some basic injection molding surface defect identification cause and troubleshooting - Let's begin by listing some of the common defects, their possible causes, and some things we might be able to do about them. One thing to remember is that as with all injection molding processes and machines, this can vary greatly from part to part, and machine to machine. Now that we have the proverbial disclaimer out of the way, let's begin, starting with the visual types of defects.
Defect - Blush - a dull spot or blemish, most commonly found near a gate or other extreme stress or high sheer areas of the part. It also will often have a grainy appearance on a smooth surface part..
Potential causes - melt temperature, barrel temperatures, hot runner temperature, back pressure, mold temperature, fill speeds, valve gate firing position, decompression settings, polish of mold surface, resin build up on mold surface, and a plugged vent.
Potential corrections - Fill speed faster or slower in proper segment, barrel temperatures up or down, hot runner temperatures up or down, back pressure increase or decrease, decompression increase of decrease, if applicable, valve gate firing positions advance or delay, correct mold polish if dull, clean the mold surface if resin or volatiles are present, and open or close the vents as needed.
Simple isn't it? For the answer visit my site at http://www.wm8c.com/plastic_injection_molding_xi.htm
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2 comments:
What about using the right purging compound between runs?
http://unitemp.wordpress.com/
While I definately agree that purging compounds have their place for very stubborn problems, most of the time they really aren't neccesary. I've found that a good abrasive regrind such as acylic will do the job nicely most of the time. Again, it depends on the resins you are using as well as colors, etc. Pekutherm is a good product though and thanks for posting!
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