PAINT BORER 518 USB
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BAE 518 USB
8 Special measuring problems
8.1 Delamination
Brittle coating materials or coatings with poor adhesion to the base material often result in
boreholes where the boundary between the coating and the substrate is not circular but
rather irregularly bounded.
Several holes should then be drilled in the sample. Take as many measurements as
possible at each hole. The largest measured value for the layer thickness is then a good
approximation of the true thickness.
There are some additional steps that may be helpful when working with poorly adhering
coatings:
•
The delamination issue is especially acute when the drill bit just penetrates the
boundary
between the coating and substrate.
Therefore, it is better to drill as deeply as possible into the substrate.
•
Always drill intermittently. Do not drill in a single stroke. Blow away the residue chips
between the individual drilling strokes. This interrupted drilling method is especially
important for tough substrate materials (e.g. certain types of plastic), because these
tend to form large chips.
•
The mechanical properties of soft plastic substrates are not favourable for drilling. Such
materials can be drilled better if they are cooled (in a freezer or with a cold spray).
When using cold spray, protect the coating surface with aluminium foil against the
harmful solvent.
