I had a few sample pieces of ceramic coaster which I had wanted to attempt to machine in some way. The most notable characteristic of the stock material was that the coasters had a matt finish and when carving with a DDE bit (and liquid soap to aid friction reduction) they appeared to be made from quite a soft material. One could not mark the coasters with a fingernail scratch but they took pencil marks very well and it was difficult, if not impossible, to remove pencil marks completely by using very vigorous scrubbing techniques with a nylon scouring pad.
I wanted to use the DDE 90° bit and it did engrave the ceramic material quite easily but the finish was not what I would call satisfactory. I had set the depth for a single pass at 0.2mm but the pattern, although clear, was not deep enough. I suspect that I should be making multiple passes to achieve the well defined edges I want to see. The two examples shown are just ok but they could use more work. Speed was 500mm per minute and I would not be temped to push the RDZ DDE bit any faster. Its spring is not as strong as the MC Etcher spring and the tube holding the bit is longer.
Short video clip of the DDE process:
The repeated pattern decreasing in size was the first attempt. I had used a viscous cutting and tapping oil that was brown in colour and it proved impossible to remove. This accounts for the stained appearance of the engraved areas. The red highlight indicates a coarse lined area that I saw on my previous attempt to engrave slate. The same bottom right corner too so that is something I need to analyse and chase down.
The flower pattern was the second attempt and it looks cleaner because I used liquid soap as the lubricant rather than a deep brown oil. The bottom right highlighted area shows the coarseness of the bit. (Is this just the engraving toolpath in CC. I guess the next experiment is to use just a pocket toolpath for the engraving and see whether that will make a difference. The small highlighted areas show the construction of each leaf and I was surprised to see that the engraver had made that line deeper. In any event, another test piece rather than a piece to give to friends.
My lack of success with the DDE bit on this new to me stock material made me consider other approaches. I thought the material was possibly soft enough to machine. The jig I had made was an exact fit and would have held the workpieces firmly with 5mm of the workpiece below the jig surface. In the end I decided to try and engrave this matt ceramic workpiece with the JTech 4.2Watt laser and Lightburn. I used a power setting of 100% and a traversal speed of 250mm per minute.
The first image is of the plain coaster in the MDF jig.
The second image is an outline of the leaf pattern I had previously tried to etch with the DDE bit. It looks sharp and clear with some sign that it was not quite central in the software when viewing the top and the the top left.
The third image is the coaster with the repeating but decreasing pattern after engraving.
The final image shows the laser at 100% power.