If 3-5% of the attempted parts placed are dropped, you have a serious problem...that's 1 part dropped for every 20 or 30 placements. Does it mean that it drops the part in the scrap bin and then successfully places the same part or would the board come out of the machine with missing parts?
We have an 11 year old Quad and we see a missed part out of the machine once every few months. You are undoubtedly running many more boards than we are but 3-5% is totally unacceptable even if it were 3-5% of the assemblies had a missing part. Do all of your machines have this problem or just one? You need to find the problem or get better equipment. There is no sense in creating assemblies with this many defects.
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