Surface finish help

Discussion in 'Investment casting Ceramic shell method' started by ka_6772, Apr 11, 2020.

  1. DavidF

    DavidF Administrator Staff Member Banner Member

    I've been clear coating mine, but its painstakingly slow. I put on about 5 coats and wet sand between coats.
     
  2. ka_6772

    ka_6772 Copper

    I didn't have much luck with paint for smoothing. Now I'm just trying to seal. At least these parts are faster to just sand the metal. My thought was to put 5-10 gallons in a plastic tub. Dip and drip. I have recently got Simplify3d at work. I think I'm going to buy it for myself to take care of some of the holes using the variable print settings.
     
  3. DavidF

    DavidF Administrator Staff Member Banner Member

    S3d is great!! Major improvement on my prints.
    I go with a 100 micron layer height on every print..... well just about :p
     
  4. Jason

    Jason Gold

    Interesting the slurry dissolved the shellac. Was it water based shellac? Why not run a test block during the next batch? Do each side of the block with a different method, but mark it well.
    Bondo, wax, thick paint, shellac, sanded smooth, clear coat.
     
  5. ka_6772

    ka_6772 Copper

    I skinned over the holes with shellac and the shellac was smooth. The casting has the layer and support lines visible. Previous castings that I used shellac on were sanded before coating. Maybe that's why I didn't notice before. Alcohols are supposed to be the only thing that dissolves shellac. From experience, Suspendaslurry doesn't like isopropyl.

    Kevin
     

    Attached Files:

  6. Jason

    Jason Gold

    Where did the alcohol come from? The slurry doesn't like any liquid until it's been fired.
     
  7. ka_6772

    ka_6772 Copper

    AFAIK alcohols are the only thing that dissolves shellac. I don't think modern slurries use alcohol for emissions reasons but something ate my shellac in this instance. I have pics of smooth shellac before investing and the casting looks like there was none ever applied.
     
  8. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Might be a pH related issue?

    K
     
  9. ka_6772

    ka_6772 Copper

    I thought I'd give you guys an update. I've been messing with my CNC machine and relearning the CAM software I haven't used in 5 years. Here's a pic of a failed print of the fixture. I have the real one shelled up and ready to cast.

    Kevin
     

    Attached Files:

  10. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Lookin good Kevin. I'm having to relearn some software to and it was a few months not years ago for me!!

    Best,
    Kelly
     
  11. dennis

    dennis Silver

    Alkali dissolves shellac, e.g. sodium carbonate will remove it completely. It's how I clean my jars, in fact - add washing soda to the usual dish soap.
     

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