Tripropylene glycol monomethyl ether (TPM) dissolves liquid resin, making it effective for washing parts printed on Formlabs SLA printers. Depending on your use case and work environment, TPM may be a viable alternative to isopropyl alcohol (IPA) for washing parts using the Form Wash or the Finish Kit.
TIP:
Read the support article Tripropylene glycol monomethyl ether (TPM) for more information.
Wash process
TPM can be used with the Form Wash or the Finish Kit.
TIP:
Follow the Form Wash workflow in the support article Using the Form Wash and the Finish Kit workflow in the support article SLA basic finishing steps.
To wash parts in TPM:
- Fill your wash containers.
- Form Wash: Fill the Form Wash wash bucket with TPM. Fill a separate container with water.
- Finish Kit: Fill one wash bucket with TPM. Fill the other wash bucket with water.
- Wash your printed parts as you would with IPA. Follow the guidelines in our support article Form Wash time settings as a baseline.
- Use longer wash times if necessary—some resins do not absorb TPM or swell as much with exposure to the solvent.
- Let the prints drip dry thoroughly.
- Rinse the prints in the water bath until all remaining TPM has dissolved. Clean IPA can also be used to rinse.
TIP:
To make the water rinse more effective, add a small amount of dish soap to the water (less than 2.5 mL (one teaspoon) for the Form Wash wash bucket). Adding dish soap also prevents any excess resin from depositing on the walls of the container.
- Let the prints air dry. Parts printed in certain resins, such as Clear Resin or Tough 2000 Resin, may come out of the water bath with a cloudy appearance. The parts will regain their normal appearance as they dry.
The surface of the part may have a waxy feel until it is fully dry. Some resins, noted below, may have additional surface waxiness for up to a week if they are not post-cured. When post-curing, follow the recommendations in the support article Form Cure time and temperature settings for each resin. Printed parts washed in TPM will feel indistinguishable from parts washed in IPA once they are post-cured.
Cleaning the build platform
If the build platform has also been washed with TPM, clean the build platform thoroughly before using it again.
- Wash the build platform with soapy water until all remaining TPM has dissolved.
- Rinse off any remaining soap with clean running water.
- Dry the build platform with a clean paper towel.
- If necessary, remove any remaining resin or TPM residue from the build platform using a paper tower wetted with IPA, then wipe the platform dry again.
Replacing used TPM
TPM can dissolve roughly three times the amount of resin as IPA before losing efficacy. If a thin film of resin remains on printed parts after washing with TPM, the solvent is overly contaminated with resin and should be replaced. Replace the TPM in your Finish Kit rinse bucket or the Form Wash as you would replace IPA.
TIP:
Wash prints in two stages to extend the lifetime of the TPM.
The water bath will eventually have too much TPM dissolved in it to be effective and will need to be replaced. Water and TPM that have been exposed to resin should be disposed of in accordance with local regulations.
Purchasing a hydrometer for TPM
NOTICE:
The hydrometer packaged with the Form Wash does not measure the correct range of specific gravity for use with TPM. A hydrometer that can measure a specific gravity of 0.962–1.000 can be used to measure the resin concentration in the TPM. When the specific gravity of the used TPM is above 1.000, it will not be fully effective as a final wash.
When purchasing a hydrometer to measure the resin concentration of TPM, consider the following recommendations:
| SPECIFICATION | RECOMMENDATION |
|---|---|
| Specific gravity range | 0.962–1.000 |
| Length | Shorter is preferred for usability |
| Scale subdivisions | 0.001 0.002 0.0005 is too specific |
| Top scale | ≥1.000 |
| Example | Thermco GW2538 Thermco GW2539 Thermco GW2559X Brannan 10/403/0 |
Effect of TPM on resins
Washing prints with TPM and a water rinse will yield different results depending on the resin used.
| RESIN | EFFECT |
|---|---|
| Standard resins (Grey Resin, Black Resin, White Resin, Clear Resin) |
Resin remains waxy when printed with a layer thickness of 50 microns or 100 microns. Post-curing removes the waxiness. Without post-curing, the waxiness goes away after about a week. |
| Castable Resin | Resin remains waxy when printed with a layer thickness of 50 microns or 100 microns, but the waxiness goes away after 3–12 hours. |
| Castable Wax Resin | Resin comes out of the wash clean and free of waxiness, requiring no post-cure to remove waxiness. If your parts remain sticky after washing in TPM, Formlabs recommends post-curing for optimal casting results. |
| Color Resin | Resin remains waxy when printed with a layer thickness of 50 microns or 100 microns. Post-curing removes the waxiness. Without post-curing, the waxiness goes away after about a week. |
| Draft Resin | Resin remains waxy when printed with a layer thickness of 50 microns or 100 microns, but the waxiness goes away after 3–12 hours. |
| Elastic 50A Resin | Resin remains waxy when printed at any layer thickness. and requires post-cure. Post-curing removes the waxiness. |
| Flexible Resin V2, Flexible 80A Resin | Resin remains waxy when printed at any layer thickness. and requires post-cure. Post-curing removes the waxiness. |
| Grey Pro Resin | Resin comes out of the wash clean and free of waxiness. |
| High Temp Resin | Resin comes out of the wash clean and free of waxiness. |
| Model Resin | Resin remains waxy when printed with a layer thickness of 50 microns or 100 microns, but the waxiness goes away after 3–12 hours. |
| Rigid Resin | Resin comes out of the wash clean and free of waxiness. |
| Tough Resin 2000 Resin | Resin comes out of the wash clean and free of waxiness. |
| Tough Resin 1500 Resin | Resin remains waxy when printed with a layer thickness of 50 microns or 100 microns, but the waxiness goes away after 3–12 hours. |
Compatibility with Formlabs products
Formlabs biocompatible resins
CAUTION:
Formlabs biocompatible resins have not been tested with TPM. For full compliance, post-process biocompatible resins in accordance with the Instructions for Use for the specific resin. If a manufacturer chooses to deviate from recommended instructions, it is the manufacturer’s responsibility to confirm performance and biocompatibility for their applications.
Finish Kit
TPM is compatible with all Formlabs resins in the Finish Kit rinse buckets.
Form Wash
TPM is compatible with all Formlabs resins in the Form Wash. The hydrometer packaged with the Form Wash does not measure the correct range of specific gravity for use with TPM.
Form Cure
The Form Cure does not vent air while operating, so any evaporated solvent will condense on the heater, fan, and internal surfaces. If a print that still has TPM on it is placed in the Form Cure, the TPM will evaporate off the print and condense on the inner surfaces of the Form Cure. This can occasionally cause clouding on the reflective surfaces. Always let prints fully dry (whether they have been washed with IPA, TPM, or water) before placing them in the Form Cure.