Hello Friends,
We currently inspect our incoming pallets according to IPC-TM-610 for bow and twist. Normally pallets will come in that are twisted and we send them back to the board house confident in our testing. Today we recieved a pallet that was bowed. According to IPC the discription of a bowed pallet is a specimen rectangular in shape that has a cylindrical curvature and four corners are touching one plane.
To test for maximum allowable bow percentage one must first determine on what axis the bow occurs one being length while the other being width. Based on this determination you will then be able to use the proper formula to test the specimen. For instance if you experienced a board with bow in the length direction you would use the formula RL=L(B)/100 where:RL=GO/NO-GO feeler guage, L= Length of the board and B=Maximum allowable twist pecentage determined by IPC-T-50). From the calculation you would get the maximum allowable bow that you would use to measure the outside perimter of the board in the length direction. This is where we have our problem the pallet is showing little or no deflection on the perimeter all the deflection occurs in the center of the pallet. My question to you is, what formula do I use to determine maximum allowable bow the Legth, Width, or a combination of the two?
Please advise if this is the right action to be taking for this particular circumstance? I beleive that the v-scoring could be causing our board to bow. The v-score spec allows for a remaining web thickness of .015". The v-score web does fall within spec but it does not remain in the center of the board thickness. for example if this | | represents the board thickness and this >< |. Please advise if the v-scoring might be our problem and if there are any IPC test methods to determine acceptability.
Much Thanks, Jacob Lacourse
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