Finishing SLA

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Finishing SLA
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Priming SLA

• It is advisable to spray a thin base-coat on the
  prototype part before sanding
• Give the part an even colour, reveal the
  unevenness, holes, cracks and other surface
  defects which are difficult to spot
• Act as a marker so that in subsequent sanding, it
  is easy to visualise which areas had been sanded
• Reveal contaminations such as uncured resin on
  the part

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Can Spray Demonstration
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Sanding

• Sandpaper is a form of paper where an abrasive
  material has been fixed to its surface it is
  part of the "coated abrasives" family of abrasive
  products
• Used to remove small amounts of material from
  surfaces, either to make them smoother (painting
  and wood finishing), to remove a layer of
  material (e.g. old paint), or sometimes to make
  the surface rougher (e.g. as a preparation to
  gluing)
• Waterproof or wet/dry sandpapers use a resin bond
  and a waterproof backing

Adapted from http//en.wikipedia.org/wiki/Sandpap
er
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Grit Size

• Grit size refers to the size of the particles of
  abrading materials embedded in the sandpaper
• ISO 6344 is an international standard covering
  the materials sizes and tests regarding sandpaper
  and other similar coated abrasives. It has three
  parts
• ISO 6344-11998 Coated abrasives, sizes and
  tests
• ISO 6344-21998 Macrogrit, P12 to P220
• ISO 6344-31998 Microgrit, P240 to P2500

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Grit Designation
ISO/FEPA Grit designation Average particle diameter
Material removal P60 0.269 mm
Material removal P80 0.201 mm
Sanding finishes P100 0.162 mm
Sanding finishes P120 0.125 mm
Final sanding before painting P150 0.1 mm
Final sanding before painting P180 0.082 mm
Final sanding before painting P220 0.068 mm
Sanding finishes between paint coats P240 58.5 µm
Sanding finishes between paint coats P360 40.5 µm
Sanding finishes between paint coats P400 35 µm
Sanding finishes between paint coats P600 25.8 µm
Sanding finishes between paint coats P800 21.8 µm
Finishes before buffing P1000 18.3 µm
Finishes before buffing P1200 15.3 µm
Finishes before buffing P1500 12.6 µm
Final sanding before buffing P2000 10.3 µm
Final sanding before buffing P2500 8.4 µm
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Material removal

• Use 60 to 100 for material removal
• Use a rigid sanding block whenever possible
• Wrap the paper around half-round or round
  sanding-block to shape concave surfaces
• Dry or wet sand
• Use the hand to feel the surfaces

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• Face by face
• From large face to small
• From flat face to pronounce
• Keep small protrusion and fillets untouched

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• Use chisels to clean negative sharp corners

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Sanding finishes

• Change to 200 - 400 paper
• The base-coat will be removed gradually to reveal
  body material
• The target is to replace previous coarse
  sandpaper strokes with finer strokes
• The progress will be fast at the beginning and
  will slow down when the surf

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Progressive Sanding

• A Thoroughly sanded away all previous strokes
• B Leave a trace of previous strokes
• C Change sandpaper pre-maturely
• D Use finish sanding to ratify unevenness of C

A
B
C
D
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Spray Painting

• Adjustment
• Cleaning before spray
• Types of paint
• Paint mixing
• Sequencing the strokes
• Spraying direction and movement
• Cleaning after spray
• Drying

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