December 29, 2015

Polishing Your Metal-Bearing 3D Prints

When 3D printing with metal-bearing filament on the LulzBot TAZ 3D printer, suspend the filament reel across the top frame extrusions. This allows the filament to feed directly into the extruder, minimizing the chances of binding or snapping. To make this easier, print the spool mount found in our Four 3D Printable Modifications for your LulzBot TAZ tutorial (Modification #3).

One of the best features of metal-bearing 3D prints is the ability to polish the surfaces to remove 3D printing layers and to bring out the shine. There are three main ways to accomplish this, each of which has it's benefits and costs.

Use of Personal Protection Equipment (such as masks, aprons, and eye protection) is strongly recommended.

Method 1: Manually filing, sanding, and polishing

 

Use a metal file or a sanding block for flat areas on the printed object. Use sandpaper for curves and details. Start with a metal file or coarse sandpaper(100-400) grit. Use finer and finer sandpaper until you achieve the desired finish. A fine reflective shine can be achieved with sandpaper in the 2000 grit range. Polishing with ultra-fine sandpaper (4000-12000 grit) can further refine the finish and sheen. Ultra-fine grit sandpaper can be found at your local hobby shop and is readily available on-line. Finish the job with a metal polishing compound.

 

Tips:

  • Use an upside-down mouse pad or silicone baking mat to help hold your flat 3D printed object in place.
  • Use a sanding block or metal file for flat surfaces.

Pros:

  • Cost Files, sandpaper, and polishing compounds are the least expensive polishing options available for post-processing your 3D printed objects.
  • Reasonably fast Manual sanding, filing, and polishing is the quickest way to achieve the look you want. Rather than taking hours in a tumbler, a little bit of hands-on work gives you a better finish, faster.
  • Dimensionally accurate Manual sanding and polishing allows for fine, detailed attention and minimizes potential heat build-up. Many metal-filled 3D printing filaments are based on PLA. Use of a high-speed rotary tool, even on low, can cause the printed object to warm to the glass-transition temperature and warp.
  • Preserves fine details Manual sanding and polishing allows you to finely preserve and highlight small areas and details, unlike other indiscriminate post-processing methods.
  • Flat surfaces If your 3D printed object has flat areas, manual sanding and polishing works perfectly. You're able to preserve and correct any flat areas, leaving clean and crisp edges and planes.
  • Safe for fragile items 3D printed objects with small towers or thin walls can be warped or even damaged by the use of powered or automated equipment. Manual sanding and polishing allows you to use careful, light pressure to preserve fine items.

Cons:

  • Hands on time Even though this method is reasonably fast, it still requires dedicated hands-on time on each printed object. If you are post-processing a large amount of objects, tumbling may be a better solution.
  • Dust Filing and sanding creates dust. Use of a face mask or other personal protection equipment is encouraged.
  • Polishing compounds can be messy Use of polishing compound or jeweler's rouge can be messy, and even may stain clothes or skin. Use of gloves, aprons, eye shields, or other personal protection equipment is encouraged.

Method 2: Rock tumbler or vibratory polisher

 

 

Start with a coarse tumbling media like screws or rough stone. Use brass plated screws for bronzeFill 3D printed objects and use stainless steel screws for Stainless Steel 3D printed parts. Smaller screws can reach smaller areas. Eventually the screws can be worn and will need to be replaced. Coarse stone can be used in the tumbler, but will leave a coarse, stone-like finish that can be polished away. Use of personal protection equipment like gloves and a face mask is encouraged, as the tumbling method will generate dust and debris.

 

Pros:

  • Minimal interaction needed Once filled with the appropriate tumbling media, you can typically turn on the polisher leave it running for 8-12 hours.
  • Polish multiple 3D printed objects at the same time If you have a large amount of objects that need to be polished, a tumbler/vibratory polisher will handle multiple different 3D prints at the same time.

Cons:

  • Slow Typically you'll have a run time of 24-36 hours, or more to achieve the desired finish.
  • Need to monitor For safety's sake, never leave the polisher/tumbler unattended.
  • Indiscriminate wear The tumbling action causes the printed object to roll around within the polishing chamber against the polishing media. This action typically only polishes the outside surface of your printed object. Inset areas, holes, and other low points may not be polished.
  • Noise Vibratory polishers can be loud during operation, as can smaller tumbling polishers.
  • Dust If your polishing media can be used dry it will create a lot of dust, which is released when the polishing chamber is opened. Use of a face mask or other personal protection equipment is encouraged.
  • Polishing media residue If the tumbling media requires the use of a liquid (typically water, soapy water, or water with citric acid) it will leave a grainy liquid in the polishing chamber and on the printed objects. There may be environmental disposal concerns depending on the polishing media and filament material used.

Method 3: Use of a rotary tool/polishing wheel

 

 

Use a sanding tool bit to wear down any visible layers and achieve an even surface. Once sanded, use a cloth polishing wheel or tool bit to apply a polishing compound. Evenly work the printed object until the desired level of shine is achieved.

Alternatively, you can mount cylindrical prints onto a mandrel. With the printed part rotating in place, you can sand and polish the item with more care and stability.

Pros:

  • Speed Much faster than filing, sanding, or polishing by hand.
  • Preserves fine details The use of a fine-tipped pointed sanding or polishing tool bit allows you sand and polish hard to reach areas.
  • Cost Typically sanding and polishing tips are inexpensive and last longer than sandpaper.

Cons:

  • Warping due to heat Sanding or polishing too fast, or in the same are for too long can lead to warping of the 3D printed part. Thin areas or fine detail can absorb heat built up through friction and can deform or break off.
  • Dust Sanding with power tools can create airborne dust. Use of a face mask or other personal protection equipment is encouraged.
  • Polishing media residue Polishing compounds can be cast off the tool and may splatter the user and the surrounding area. Use of a face mask or other personal protection equipment is encouraged.