I was just wondering if anybody can offer me any tips or advice for a project I am working on at the moment. We have been carrying out shot blasting using various abrasives to improve the surface roughness of some polypropylene parts that we are making for the medical industry (1m to 2.5m diameters). Various abrasives have been tested such as garnet, glass bead AB 177-297 and 801 AC, brown aluminium oxide 80/100 and 180/220, white aluminium oxide 70, 120 and 180/220, kiln dried sand, blasting grit (came free with the Sealey shot blasting gun), Honite 13 glass bead, Type 2 plastic media (Urea Formaldehyde) and Type 5 plastic media (20/30 and 30/40 acrylic).
White aluminium oxide 180/220 and acrylic blast media gave us the best results. However, when an electron microscope was used to find the surface roughness of some polypropylene samples that had been blasted with aluminium oxide 180/220, we found that the surface roughness was around 2.5 microns Ra, when it needs to be 0.8 microns Ra.
We therefore still need to improve the surface finish considerably. Does anybody have any suggestions of how we can do this? We are currently carrying out more shot blasting testing with aluminium oxide and plastic media. We are also looking into dry ice blasting.
Also, we would like to be able to measure the surface roughness of our samples on-site while we are carrying out trials. I am therefore looking into hiring/buying a surface roughness testing machine. Can anyone recommend UK companies who might be able to help with this?