Mass Finishing for FDM Parts
Process multiple Fused Deposition Modeling (FDM) parts simultaneously using one of these tested mass finishing techniques. By abrading the stepped outer layers in an action called “cutting,” mass finishing removes a mere 0.0015 to 0.003 inches of material, so you can achieve a smooth finish without sacrificing accuracy.
Stratasys has tested vibratory and centrifugal barrel mass finishing systems with a variety of media. Consider these guidelines as you work with your supplier to choose the right mass finishing system.
Suitable for all FDM materials, vibratory machines are available in tub and bowl shapes of various sizes. Stratasys prefers bowl systems for their gentler processing and uniform smoothing action, but tubs can be used with some added precautions.
Standard tub-shaped systems process parts more aggressively, which reduces cycle time, but increases the risk of damage. As a best practice, add plastic or metal rods to protect parts from damage that can result from media lodging between the parts and the tub wall.
Also, make sure the tub is large enough for media to flow freely in all directions. Mount long parts in a fixture to prevent distortion due to processing torque.
Centrifugal barrel systems
Centrifugal barrel machines smooth parts built in any FDM material by tumbling them in a rotating drum. Compared to vibratory systems, barrel systems are better suited for parts with fine details or delicate features.
Mixing media works well with some machines and parts, but certain media combinations may create an imbalance as the barrel spins.
Consider the size, density and geometry of your typical parts when choosing media. Small parts require small media, and highly detailed or fine-featured parts require angular shapes that can reach recessed surfaces.
Stratasys tested ceramic, synthetic, plastic and corn cob media on FDM parts with the following results. These types of media should be usable on all FDM materials. However, Stratasys recommends testing parts with your chosen media prior to full scale operation to ensure acceptable results.
Used for cutting or polishing, ceramic is the heaviest and most aggressive media option. It is best suited for the toughest FDM materials – PC, ULTEM 1010 resin, ULTEM 9085 resin and PPSF – but it can create a glossy surface on any FDM part built without delicate features.
Plastic media is best suited for smoothing. This media is less aggressive because it’s softer and lighter than ceramic.
Synthetic media is lighter than plastic or ceramic and reduces the risk of damage. If the weight of ceramic or plastic media might break thin walls or delicate features, synthetic media may be a good alternative. However, cycle times will increase because of its lighter weight.
Ground corn cob can provide a final polish on FDM parts. You can quickly wash away any resulting discoloration.