The normal surface finish of FDM parts is suitable for most purposes, but in applications where a smoother surface is required, solvent smoothing is an alternative to sanding, filling, and mass finishing.
Solvent smoothing utilizes a chemical agent to smooth a part’s surfaces (Figure 1). This process modifies the surface of FDM parts by eliminating layer lines while preserving feature detail and part accuracy. The smoothing agent can be applied either as a liquid or a vapor and it is quick and nearly labor-free. The finish achieved can mimic that of injection molded parts.
This tutorial is courtesy of Stratasys.
Step 1: Overview
Solvent smoothing is applicable for SR30TM and the ABS family of materials. Parts that have been solvent smoothed may have surface bubbling when exposed to temperatures above 70°C (160°F).
Common applications where solvent smoothing is applicable:
Liquid sealing (low pressure)
Air pressure (low pressure)
Mold masters (i.e., silicone molding, sand casting, investment casting, and thermoforming)
Liquid Smoothing: Dipping FDM parts in a solvent bath yields a smooth, glossy surface finish. It has the advantage of requiring no additional equipment. However, the results are influenced by technique; over-exposure to the solvent will alter feature definition and detail.
Vapor Smoothing: Vapor smoothing requires a Finishing Touch Smoothing Station (Figure 2). The advantages of this method are greater control of feature detail and accuracy by controlled exposure to the chemical solvent.
Step 2: You Will Need
• Glass beaker
• Solvent: IPS Corporation Weld-On 4 or acetone 4.2.
• Finishing Touch Smoothing Station
• MicroCare® Smoothing Station Fluid (SSF)
Step 3: Dip Smoothing
Lightly sand the part to smooth any seams or defects. Remove dust and debris. Fill a glass beaker or other solvent-safe container with solvent solution such as IPS Corporation Weld-On 4 or acetone. Attach a wire or similar material so the part can be suspended. Immerse part in solvent (typically for 15 to 30 seconds). Avoid longer durations as this will cause features to deform (Figure 3).
Ensure that there is no pooling of solvent on the part. Allow part to dry for 15 to 20 minutes. Inspect part. Repeat above steps as needed. Allow the part to rest for 12 to 18 hours to ensure complete solvent evaporation and surface hardening.
Step 4: Vapor Smoothing
Lightly sand the part to smooth any seams or defects. Remove dust and debris. Attach a wire or similar material to suspend the part in the cooling chamber. The Finishing Touch Smoothing Station will signal the completion of the cooling cycle, which typically takes 30 minutes. Confirm that the solvent vapor has risen to the top of the smoothing chamber. If it has not, leave the part in the cooling chamber and wait for the vapor to rise. Transfer the part to the smoothing chamber (Figure 4) for a 15 to 30 second exposure.
Ensure that there is no pooling of solvent on the part. Return the part to the cooling chamber and allow it to rest for 15 minutes. Inspect the part. If further smoothing is needed, repeat the above steps as necessary (typically 2 - 4 times). The part will be dry to the touch after 45 minutes but allow 12 to 18 hours for the part to fully harden and the solvent to completely evaporate.