Thermal Curing
Salt Baking
6min
Salt baking is the process of packing parts in salt during the baking process. The primary purpose of packing parts in salt is to act as a fixture to prevent deformation of the part during baking.
- Salt baking supports and preserves delicate features and thin parts.
- If a part needed supports during printing, the same features may require support in the oven.
- Carbon recommends using an additive free salt with grains no larger than 0.2 mm.
- Salt can be filtered and reused.
- Reuse for up to 1000 bake cycles. Replace when salt is discolored, picks small bits of resin and/or retains an odor.
- Salt will stick and cure to any areas not thoroughly cleaned.
- Salt cured to a part cannot be washed away.
- Salt can contaminate parts not salt baked. Keep salt packing area away from standard baking area.
- Some resins are not compatible with salt baking. Refer to the specific resin protocols for information.
1
Prepare the parts
- Thoroughly wash and dry the part per standard washing protocol.
- When applicable to the resin, flash cure the part in your UV oven before salt packing per resin specific protocol.
- This secondary UV cure (flash curing) lightly cures the outside of the parts and helps reduce salt sticking to the parts during baking.
- Flash curing is not recommended for FPU to maintain material properties.
2
Add salt to baking pan
- Half-fill a baking pan with sifted salt.
- Keep salt baking equipment separated from other baking supplies.
- Thin, flat parts are prone to warping during baking. To minimize warping, these parts can rest directly on the tray with salt added on top only.
3
Nestle parts in salt
- Nestle the part in the salt by lightly wiggling the part back and forth.
- Select a packing orientation that supports overhangs and delicate features.
- Thin walls of parts often work best when oriented vertically, with the salt supporting the sides of the wall.
4
Cover parts with salt
- Use wire strainer to sift more salt to cover the part completely. The strainer removes clumps of salt or other larger bodies from the salt in the pan.
- Sifting is important to properly support the parts. Clumped salt may leave support gaps.
5
Prepare the tray
1. Tap the container on the bench to settle the salt.
2. Cover baking pan with nonstick foil to contain the salt and prevent it from contaminating the inside of the oven.
6
Bake
- Place pan in the oven on the lowest rack to ensure no salt spills onto other baking parts.
- Or designate an oven for salt parts only.
- Bake according to resin thermal cure requirements.
7
Remove parts from oven
- When baking is complete, wearing heat-resistant gloves, remove the pan from the oven and allow it to cool (~27º C).
- Cooling prevents the part from warping when you take it out of the salt.
- Cooling can take 60+ minutes for a full pan of salt.
8
Remove salt from cured parts
A superficial layer of salt remains on the part after baking that needs to be washed off.
- Remove part from salt by emptying pan into a strainer to separate out parts.
- Rinse off salt with warm water.
- Dish soap may be added to a bath of warm water to facilitate washing.
- Lightly scrub the part with a toothbrush as needed to remove residual salt.
- Use compressed air to dry the part and remove any excess salt.
Clumpy white residue that does not rise away may be present on the part. This is a result of salt adhering to resin residue left on the part after washing.
- This can be an issue around holes and openings that can trap liquid resin which seeps out during baking before fully curing.
- To minimize the chances of seepage, use swabs or compressed air to fully clean holes before baking.
To remove the salt residue:
- Use sanding or scraping tools appropriate to the part geometry.
- Baked-on salt is no longer water soluble.
- Typically, Carbon recommends reprinting the part and taking extra care to clean the problem areas before baking.
- Do not put the platform in the oven. The heat from the oven will damage the platform and require factory reservicing.
