Post-processing—washing, post-curing, removing supports, polishing, painting, etc.—brings your printed parts from the printer to their finished state. For resins used for biocompatible applications, certain post-processing steps may be required as part of producing a biocompatible end part.

For SLA printed parts, post-processing includes washing to remove excess liquid resin left over from the printing process and post-curing, which is often required for parts to reach their optimal mechanical properties.

For SLS printed parts, post-processing includes separating your printed parts from the surrounding unsintered powder and removing the Surface Armor, a semi-sintered shell that minimizes potential thermal inconsistencies which can adversely affect your parts.

In all cases, further post-processing, including polishing and painting, helps bring your parts to their intended functional and aesthetic state.

Formlabs resins cure with 405 nm light, so both our printers and post-curing devices use that same wavelength. Some materials need additional heat to reach their final material properties.

Parts printed in Clear Resin tend to get less clear with exposure to oxygen. To ensure longer-lasting clarity, wet sand with increasingly-fine sandpaper, polish, then seal with a clear spray. For an example workflow, see Polishing Clear Resin for a transparent finish.

There are three main ways to bond 3D printed parts together:

• Epoxy designed for use with plastic
  • Good for large parts
  • Medium impact strength
  • Slower assembly process
  • Choose an epoxy based on needed working time and color
• Cyanoacrylate glue
  • Good for small and medium parts
  • Low impact strength
  • Quick-drying for fast assembly process
• Resin
  • Good for small parts
  • Low impact strength
  • Apply a small amount of liquid resin to the surface to be bonded using a dropper or syringe, then cure with a 405 nm UV laser light pen.

For more information, see our blog post on printing 3D models larger than your printer’s build volume.

There are a wide variety of ways that you can color your SLA and SLS printed parts. For an overview, see our page on post-processing 3D printed parts.

SLA

• Paint your SLA printed parts much like you would other plastic: sand, clean, and prime your parts, then paint using the technique of your choice.
• Print with Color Resin—you can specify a particular color when purchasing the material.
• Add alcohol dye to your resin before printing to print directly in the color of your choice.
• Apply a colored ceramic coating using Cerakote. For more information, see our support article on ceramic coating with Cerakote.
• Electroplate your parts for cosmetic or functional purposes.

SLS

• Adding dye to Formlabs powder before printing is not recommended and may void your warranty. However, Formlabs recommends dyeing parts printed in Nylon 12 White Powder after post-processing to achieve a range of colors. For more information, see our blog post on dyeing SLS 3D printed parts or this customer story highlighting the use of dyed Nylon 12 White Powder in a production environment.
• Apply a colored ceramic coating using Cerakote. For more information, see our support article on ceramic coating with Cerakote.

Yes—you can add alcohol dye to your resin cartridge or resin tank to color your resin. In our experience, Clear Resin works particularly well for this. For more information, see our blog post Guide to Post-Processing and Finishing SLA Resin 3D Prints. You can also purchase and print with Color Resin to specify a particular color.

Supports are a required element of SLA printing. When working with Formlabs SLA printers and removing supports from printed parts:

• Orient parts to reduce the number of support touchpoints needed on fine or detailed geometry.
• If possible, print models directly on the build platform, rather than on a raft with additional supports.
• Update PreForm to use the latest print settings and support generation algorithms. Formlabs works to balance print success with ease of post-processing. New support features, such as crushable lattice supports, help to speed up your post-processing workflow and minimize support marks.
• Use flush cutters or another similar tool to cut supports close to the surface of the part. Work from the outside edge of the support structure and move inward.

The most common reason for parts not coming out clean after washing is that your wash solvent is saturated with dissolved resin. For best surface quality, replace your wash solvent when the resin concentration is too high or when it no longer effectively cleans printed parts.

For best results, consider using a two-step wash process: an initial wash to remove the bulk of the liquid resin followed by a secondary wash to get your parts fully clean.

TPM can leave parts printed in certain resins feeling slightly waxy or tacky. This usually fades over time or after post-curing. For more information, see Washing parts with TPM.

Several factors can cause your printed parts to remain sticky or tacky after post-curing:

• Dirty wash solvent
  • For best surface quality, replace your wash solvent when the resin concentration is too high or when it no longer effectively cleans printed parts.
• Incorrect post-curing settings
  • Formlabs provides Form Cure and Form Cure L time and temperature settings for parts printed in each resin to reach their optimal mechanical properties. These settings are also available as presets on the machines’ displays. Use the correct setting for your material.
• Malfunctioning post-curing unit
  • The Form Cure and Form Cure L use a combination of heaters and banks of LEDs to post-cure printed parts. If any of these components are broken or malfunctioning, the machine will not effectively post-cure your parts and may leave them sticky or tacky. If a bank of LEDs is visibly off during a post-curing cycle or your Form Cure or Form Cure L has difficulty reaching its target temperature, it may need to be repaired. Replacement parts are available for purchase on the Formlabs Store. Contact Formlabs Support or your authorized reseller for more information.

Over time, solvent accumulates dissolved liquid resin, which reduces its efficacy. For best surface quality, replace your wash solvent when the resin concentration is too high or when it no longer effectively cleans printed parts.

When using a Form Wash, a Form Wash L, or a Finish Kit, check the resin concentration with a hydrometer.

• For isopropyl alcohol (IPA), replace the used solvent when the resin concentration reaches 10% or when the O-ring of the hydrometer that is included with the Form Wash (after it is calibrated in fresh IPA) rises above the float's tall wings.
• For tripropylene glycol monomethyl ether (TPM), replace the used solvent when resin concentration reaches 30–32% or when the specific gravity is above 1.0.
• For Formlabs Resin Washing Solution, replace the used solvent when the specific gravity is above 0.975.

When using a Form Wash L, the included solvent monitor measures the resin concentration. The Form Wash L notifies you when the solvent needs to be replaced.

The Form Wash V1 has fixed build platform mount arms and two doors on the sides of the unit for holding tools.

The Form Wash V2 has moveable build platform mount arms and does not have integrated tool storage.

The Form Wash L V1 and Form Wash L V2 are more similar. The Form Wash L V2 comes with moveable build platform mount arms that can accommodate Form 2, Form 3, Form 3L, Form 4, and Form 4L build platforms. You can purchase the Universal Build Platform Adapter to retrofit this functionality onto a Form Wash L V1.

Formlabs has recommended wash times for each resin. In general, depending on the cleanliness of your wash solvent, you can continue to wash your parts as needed until they come out clean. 

Formlabs also provides Form Cure and Form Cure L time and temperature settings for parts printed in each resin to reach their optimal mechanical properties. These settings are also available as presets on the machines’ displays. Refer to the time and temperature settings for your machine for post-curing recommendations:

• Form Cure V1
• Form Cure V2
• Form Cure L V1
• Form Cure L V2

For biocompatibility compliance, Formlabs dental and medical resins were validated with a dedicated resin tank, build platform, wash unit, and post-processing equipment that were not mixed with any other resins. For best results, follow those same requirements. Always follow the Instructions for Use or manufacturing guide when printing with a resin for a biocompatible application.

The best way to prevent warping during post-curing is to leave your part on supports. The support structure keeps the part from warping due to heat and the internal stresses of post-curing.

• Flexible resins are more difficult to sand than more rigid resins. Consider using a hobby knife to trim support marks as close to the surface of the part as possible. If sanding is required, try freezing the part and wet-sand in a bowl of ice water.

• For the best possible surface finish, sand or bead blast your parts after removing supports.