Using Castable Resin
Castable Resin is optimized for the best burnout performance, but developing a specific burnout and casting process is up to you. Formlabs offers guidelines for a process that has worked well during testing.
Castable Resin allows you to print in Fine Detail, with a material created specifically for direct investment casting. This resin burns out cleanly with no ash or residue, making it perfect for jewelry.
Fine Detail Print Settings
These settings are available when using Castable Resin (FLCABL02) and printing on a Form 2. These settings were optimized for printing jewelry, with a focus on achieving the features and detail that matter to jewelers. For the majority of designs, printing with the 50 micron layer height provides the best results and superior print speeds. The following table suggests when you may want to choose 50 or 25 micron layer height settings respectively.
|Prongs||> 0.4 mm|
|Filigree||> 0.2 mm|
We've tested the burn-out schedule below with great results using R&R Plasticast with BANDUST. This investment was developed specifically to work with photopolymers like Castable Resin.
If you are experiencing difficulty with this burnout curve, you can try:
- Extending the 30 minute suggested Hold time at 350 °F / 177 °C.
- Post-curing parts for longer. We suggest a minimum of 120 minutes, but thicker pieces especially will need more time. This step is critical in preparing prints for burnout.
- If you cannot use R&R Plasticast with BANDUST, look for an investment recommended for use with photopolymers. You can also experiment with bonded investments, like those typically used for Dental applications.
1. Preparing a Print for Investment Casting
Print and Finish Your Part
Casting is both a skill and an art form. For successful results, the design of the piece to be cast is as important as the material it's printed with and cast into. It is important to design for material flow when modeling, avoiding sharp corners and moving from thick to thin profiles on the same piece.
Follow the standard post-print procedure:
- Allow part to fully dry after removing from the IPA bath.
- Post-cure Castable Resin prints (detailed instructions) for a minimum of 120 minutes at a 45°C temperature under a 405 nm wavelength light source. Curing times vary with the specifications of each UV light source. Small UV sources like home UV nail dryers may take up to 8 hours to properly cure parts, while industrial UV curing ovens may take only a few minutes. Some equipment may cure parts more evenly if they are rotated midway.
Post-curing is an essential step in preparing your part for casting. It will make the print stronger, leading to a crisp, cast piece. Skipping this step could lead to poor burnout performance.
- Carefully remove support material from your print.
- Gently sand away any support marks so they do not appear in your casting.
Unlike other Formlabs resins, do not finish the print with mineral oil after sanding.
Prep the Model for Casting
- Add wax sprues and gates to the print as you would for lost wax casting. Ideal positioning will vary with part geometry.
Instead of adding wax sprues post-print, you can build them into the part directly using your CAD design software.
- Attach the part to a rubber sprue base using softened wax. Make sure the wax is as smooth as possible.
- Attach a casting flask to the rubber sprue base.
2. Preparing the Mold
- Weigh and mix the investment according to the manufacturer's instructions.
- Degas the container with mixed investment in a vacuum chamber.
- Pour investment into casting flask.
- Degas the filled casting flask in the vacuum chamber again.
- Place filled casting flask on flat surface and allow to dry according to manufacturer's instructions.
- Remove the rubber sprue base and allow investment to dry for another 2 hours.
- Place casting flask in a furnace and heat according to the burnout schedule provided above.
Not following the burnout schedule provided may result in damaged parts.
- Remove the mold from the furnace.
- Cast as you normally would.
Casting is an involved process. For best results, work with a casting specialist.