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Figure II.13: Wipe sample of a conveyor belt

Figure II.13 shows a wipe sample taken from a conveyor belt of an injection moulding machine. The background was a paint wetting failure of automotive body components. It had been assumed that after injection moulding the raw polymer parts may have been contaminated by substances that are transferred from the conveyor belt between injection moulding machine and transport container. Therefore, the DOE was to investigate the mobile substances that are present on the surface of the belt and check if they can be responsible for the paint defect. Of course, cutting out a section of the belt and transfering it to the laboratory is not a realistic choice. So dry wiping has been chosen to sample the belt surface. This procedure needs analytical grade cellulose or paper which absorbs the particles but also greases, separating agents, additives and residues of cleaning procedures. It should be wiped cross wise over the whole belt. It is important that the target area of the sampling device is never touched by the fingers. Directly after sampling the wiping tissue should be stored in a clean laboratory glass vial for transport to the lab.