We have experienced major problems with the surface that has been polished also having been blasted, see Figure 1. It is only at very low pressure that we are not able to see blasting craters in the surface.
The polishing agents and blasting sand used during the very first trial runs have been analysed. It was proven that the polishing agents also contained sand. When the entire system was very carefully cleaned, sand was found inside the pump - probably remnants from the first runs. There is also a risk that dust from the water jet cutting machine, located in the same room as the polishing equipment, contributes to the contamination of the polishing agent. Now that the reason for the blasting effect has been identified, we can eliminate it and concentrate on improving the polishing process.
Analysis of polished surfaces
An optical profilometer, NPFlex, has been purchased and is to be installed in mid-September, see Figure 2. It makes it possible for us to measure the surface roughness and obtain high resolution 3D images of the polished surfaces. The profilometer that we finally purchased has a large work area, which means that we can measure the surface roughness of finished products such as large bowls. The lens has a long working distance which means it is possible to measure down into cuts, for example. Read more about the new equipment here.
If a surface that
we have polished with Sillitin (Figure 3) is examined, it is possible
still to see ridging caused by the grinding. We have not removed a sufficient
amount of material to get rid of the grinding ridges but other irregularities
have been reduced so the surface begins to look shiny.