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Problem : This could just as easily fit in the "Electronics" section, but a couple of years ago at another company, we had a Model 48 Irwin thermoformer that would get servo boards fried about once a week. After observing the operating personnel running the machine, I noticed that when someone would load a roll of sheet (60 mil RPET), they would go to the Microphaser (main micro-processor controller) and hit a button to start the next roll. I noticed ESD (static) sparks of up to 1 1/2 inches come from the operators finger to the keypad. This would go through the front panel and eventually fry one or more of several servo boards at $1500 each
Solution : Knowing that the building in general and machine in particular had poor grounding due to poor soil conditions in the area, I had to come up with a way to discharge the operators before they discharged themselves into the computer and servo boards. I made a device that consisted the following: A 7/16 X 3" hex head bolt stuck through a 1" long soft die spring. A 2" long 1/2" dia. PVC pipe with a 1/2 X 1 reducer on one end with a short piece of 1" pipe and a cap with a 5/8" hole drilled in the cap glued into the reducer. On the other end of the 1/2" pipe was a 1/2" male adapter. A 2" X 2" X 3/4" Aluminum plate with a hole drilled and tapped for 1/2" NPT in the middle. I put the bolt/ spring assembly in the pipe assembly (minus the cap), Then glued the cap in place thereby trapping the bolt with the head pushed against the cap with the hole from the inside. I then screwed the other end of the pipe assembly into the aluminum block. I mounted the whole thing to the side of the control cabinet where I had scratched of some paint for the bolt to make contact. When an operator loaded a roll of sheet onto the machine, they were to push this "button" until it bottomed against the cabinet. When they pushed this button against the opposing force of the spring, it made better contact with the skin of the finger and insured that the spark from the static discharge occurred between the other end of the bolt and the cabinet. This served 2 purposes. 1. It kept the operators discharged and the servo boards safe. 2. It prevented the operators from having the hell knocked out of them from the static. This went a long way in aiding with compliance with the requirement that this button be used before contact with the panel.
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Problem :What is the difference between crystalline and amorphous polymers?
Solution :In general, crystalline polymers are more difficult to process, have higher melt temperatures and melt viscosity's, and tend to shrink and warp more than amorphous polymers.
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