Polyurethane is used for its excellent noise abatement, chemical resistance, and physical properties. Typically, polyurethane parts are made by casting or reaction injection molding. PU Rigid 650 Resin is developed with a hybrid chemistry which allows it to be compatible with Formlabs SLA printers.

Parts printed with PU Rigid 650 Resin have extremely high impact strength and the physical properties of polyurethane, making them ideal for end-use applications that are intended to be exposed to harsh conditions.

PU Rigid 650 and PU Rigid 1000 Resin have been evaluated as a skin contacting device in accordance with ISO 10993-1.

PU Rigid 650 Resin prints at 50 microns and 100 microns.

See the table below for a comparison of relevant material properties:

To learn more about the performance properties of Formlabs resins, refer to the library of material properties data sheets.

The workflow for PU Rigid 650 Resin is more complex than other Formlabs SLA materials. Formlabs recommends the purchase of additional third-party supplies to ensure printing success with polyurethane resins.

Formlabs recommends the use of a dry cabinet for improved climate and moisture control while printing and storing PU Rigid 650 Resin and PU Rigid 1000 Resin.

There are multiple possible workflows when printing with a Formlabs PU Rigid 650 Resin, depending on your needs and available resources. You can print with a dry cabinet or in ambient conditions, and you can print using automatic resin dispensing (as with other Formlabs resins) or by manually filling your resin tank (not available on the Form 2).

PU Rigid 650 Resin is sensitive to heat and moisture. It is shipped in an aluminum bottle with an empty resin cartridge. Once the aluminum bottle is opened, the shelf life of the resin is approximately one month.

Once the resin is poured into a cartridge or tank, sustained exposure to moisture in the air starts to cure it, and its viscosity increases until printing is no longer possible. The period when the resin viscosity is within a viable printing range in the resin tank or cartridge is called pot life.

Left: PU Rigid 650 Resin that is still viable. Right: PU Rigid 650 Resin that is no longer viable.

To determine whether the PU Rigid 650 Resin in a resin tank is usable, drag a spatula or other flat, blunt tool along the bottom of the tank. If the resin pours into the gap left by the tool, it is still usable. Alternatively, use a Zahn cup #5 viscometer to determine if the resin viscosity exceeds 2000 cPs. Change the resin in the resin tank or add fresh resin from the resin cartridge if the viscosity exceeds 2000 cPs.

Before starting a print, prepare your resin and printer.

If you are planning to print using Automatic filling, fill the resin cartridge:

1. Shake the aluminum bottle of resin to ensure it is thoroughly mixed.
2. Unscrew the vent cap on the top of the cartridge. Use the funnel included in the resin kit to pour resin from the bottle into the empty cartridge.

3. Screw the vent cap back on. The resin’s pot life in the cartridge ranges from seven days to four weeks, depending on the ambient humidity and temperature outside the cartridge.

If you are using the Recommended or Modified workflow, install your printer in your dry cabinet:

1. Place the printer in a dry cabinet and level the printer.
2. Set the humidity to the lowest setting in the dry chamber.
3. Insert the cartridge, resin tank, and build platform into the printer.

Install or update PreForm, then set up the next print job.

To prepare a model for printing in PreForm:

1. Open a model.
2. Select the resin, resin version, and the desired layer thickness.
3. Select Automatic filling or Manual filling, depending on how you plan to dispense resin into the resin tank. Formlabs strongly recommends using Automatic filling.
4. Orient to preserve fine details.
5. Generate supports.

6. If you are using Manual filling, check the required resin volume for your print.
   1. If your print requires more resin than can safely be used with the manual filling option, PreForm displays the message Overfill Condition Detected in the Printability pane. Switch to Automatic filling and prepare the resin cartridge to continue with the print.
   2. If PreForm does not display Overfill Condition Detected, you can proceed with manual filling. Take note of the estimated volume of resin required for the print. Shake the aluminum bottle of resin to ensure it is thoroughly mixed. Measure that amount of resin from the aluminum resin bottle using a clean graduated cylinder or scale, then pour the resin into the resin tank.
7. Send the print job to the printer.
8. Start your print.

The Form Wash and Form Wash L agitate the solvent bath and remove parts from the bath after a set time. Wash printed parts on the build platform to prevent damage. Wash parts in PGDA for two minutes and use compressed air to blow the solvent off parts. Repeat if necessary.

Remove parts from the build platform after washing in PGDA. Carefully slide a removal tool or a scraper knife under the beveled edge of the raft. Slowly peel to separate the parts from the build platform. Clean excess liquid resin from the build platform with a spray bottle of PGDA or isopropyl alcohol.

Parts can be dipped in an n-Butyl acetate bath for no more than 15 seconds to speed up the evaporation of PGDA. Use compressed air to blow excess n-Butyl acetate off the parts. Do not use a Form Wash bucket for the n-Butyl acetate bath, as it has not been tested with high concentrations of the solvent.

Place parts on parchment paper or a similar non-stick surface in ambient conditions for at least 24 hours to allow all remaining PGDA to evaporate. Ensure that all solvent dries before post-curing, as this may affect surface finish.

PU Rigid 650 Resin must be post-cured in a humidity cure chamber. For more information about recommended third-party supplies, see the support article Recommended tools and supplies (PU Resins).

The post-curing cycle for PU Rigid 650 Resin is longer than other Formlabs SLA resins. Post-curing time depends on part thickness.

Formlabs recommends post-curing most parts without supports. Supports are more difficult to remove after they are post-cured. However, due to the low green strength of the material and the elevated temperatures at post-cure, some geometries are prone to sagging or warping slightly before the material is fully cured. Parts with such geometries should be post-cured on supports.

To post-cure parts printed in a Formlabs PU Rigid 650 Resin:

1. Carefully remove supports using flush cutters.
2. Optional: Sand off support marks.
3. Make sure parts are completely dry before post-curing.
4. Set the humidity chamber to 46 °C and 70% relative humidity.

5. Ensure that the oven light is turned off. Having the oven light on during the post-curing cycle may negatively affect the mechanical properties of your printed parts. You can control the Anova Precision humidity oven’s light using its companion app. Consult your oven’s user manual for more information.
6. Place parts on clean parchment paper or a similar non-stick surface laid on the shelves in the humidity chamber. The non-stick surface prevents parts from sticking to the shelves.
7. Leave the parts in the chamber for the time listed in the table below to achieve optimal mechanical properties. Leaving parts in the humidity chamber for longer than the recommended time does not adversely affect them.

Maintain your resin tank and PGDA between prints to ensure a successful and consistent workflow.

Cleaning the resin tank

Before continuing to print, Formlabs recommends checking the resin tank interior for any cured resin or debris that can interfere with subsequent prints. Please refer to the instructions for inspecting the resin tank interior on a Form 3, Form 3+, Form 3B, Form 3B+, and on a Form 2.

Replacing or recycling PGDA

PGDA solvent will eventually become saturated with solidified resin particles due to resin curing and will no longer be effective at washing your parts. Formlabs recommends replacing your PGDA solvent when you start to notice small particles of cured resin on your parts after a wash cycle. In general, this begins to occur after printing and washing parts using 10 liters of resin or after several weeks of solvent usage in a Form Wash.

You can replace your resin-saturated PGDA with fresh PGDA. Alternatively, you can filter the solidified resin particles from the PGDA and reuse the solvent. To filter your PGDA:

1. Place a 75 micron paint filter over a clean bucket large enough to contain the used solvent.
2. Pour or pump the PGDA mixture from your Form Wash or Form Wash L through the paint filter into the bucket. Wait one day until the mixture is completely filtered. Dispose of the filtered solid particles and re-use the solvent.

• PU Rigid 650 Resin usage guide [en] [de] [fr] [it]
• PU Rigid Resin Quick Start Guide
• Recommended tools and supplies for PU Rigid Resins
• PU Rigid 650 Resin safety data sheet (SDS)