How Do You Polish Clear Resin?

SLA

With a stereolithography 3D printer like the Form 3, you can additively manufacture transparent objects and polish them to be optically clear.

The Form 3 (and larger Form 3L) print Clear Resin with a print process called Low Force Stereolithography, which reduces peel forces on parts, producing fewer rough surfaces for improved surface finish.

Clear Resin can be used to show off geometries, showcase internal details, create clear prototype parts, and in optics, fluidics and consumer applications.

Polish Formlabs Clear Resin

To polish Clear Resin and make it optically clear, follow these steps:

Step 1: Wet sanding

What you need:

  • Water
  • 800 grit and 1,200 grit sandpaper

Wet sanding creates a smooth, even surface finish for polishing. Working from rough to ultra-fine grits will give you the best finish.

How to do it

Immerse your sandpaper in water for 10 minutes. Starting with 800 grit, sand your 3D printed part in a straight line motion for 10 seconds, moving the part, not the paper. Stop when the part is evenly sanded and move onto the next grit.

We recommend starting with 800 grit sandpaper and moving on to 1200 grit for an ultra-smooth finish.

Step 2: Acrylic cleaner and cork

What you need:

  • Acrylic cleaner, such as VuPlex
  • Corkboard or cork sanding block

Acrylic cleaner and cork finely abrade the surface of the part, removing imperfections in the finish and creating a smooth, glossy finish.

How to do it

Place the corkboard on a flat surface. Spray the cork and part with acrylic cleaner. Using the same motion as for wet sanding, rub your part against the cork with 10 second passes. What you are looking for is a smooth, near-transparent surface finish.

We recommend using a cork sanding block with the corkboard, which will help you get into overhangs and areas the board won’t touch.

Step 3: Polish with a microfibre cloth

What you need:

  • Dry microfibre cloth

Polishing with a microfibre cloth is the buffing stage, where you buff off the polish residue (acrylic cleaner and resin) and buff the part.

How to do it

Using a clean microfibre cloth, hold the part in one hand and buff it using the other. The faster you buff, the more transparent the finish. For greater transparency, clamp the part in a plastic vice and work the cloth with both hands.

If at this stage the part isn’t clear enough, redo the acrylic cleaner and cork stage, working the part faster to achieve greater clarity.

Step 4: Spray an acrylic coating (optional)  

What you need:

  • Rubber gloves
  • Aerosol acrylic spray, such as Krylon

Acrylic spray is a sealant that seals the polished finish, providing a permanent protective coating that will not yellow or regrade.

How to do it

Put on a pair of disposable rubber gloves. Hold or suspend the part and spray it evenly, allowing 10 minutes between coats. Spray two coats, ensuring even coverage. Don’t let the coating drip or you’ll get a poor finish.

Although optional, the acrylic spray will help to preserve the polished finish of your part and improve its abrasion resistance.

Step 5: Inspection

Now that your part is polished and sealed, you can inspect it with your eye.

Hold the part up to a light and inspect its clarity. Is the surface finish even? Are there any imperfections?

You can always redo the polishing stage if you need to, but keep in mind that polishing removes layers of resin. If you need precise parts, factor polishing into your designs with extra thickness, so you have leeway.

To find out more about polishing Clear Resinrequest a Formlabs sample, call us on 01765 694 007, send us an email at sales@additive-x.com. Or book a discovery call with our Formlabs specialists Elaine Rutledge or Tammy O’Neill.

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