Washing Prints

Wash printed parts before post-curing to remove residual resin from the parts’ surfaces.

Washing removes excess liquid resin from the parts’ surfaces and cavities. Comparing a printed part before and after the wash step shows the final part ready for use or post-curing.

Part Washing Overview

Two factors work together to remove the thin layer of liquid resin from the surface of printed parts: solvation and agitation. The solvent dissolves liquid resin, and agitation removes the dissolved resin from the parts’ surfaces, replacing dissolved resin with cleaner solvent.

Formlabs suggests isopropyl alcohol (IPA) as a solvent for washing, and IPA is used as the default solvent throughout instructions. Other solvents have been tested for compatibility with Formlabs resins, but these solvents have not been tested for use with Formlabs’ hardware.

Part washing solutions range from the automated Form Wash to manual agitation with the Form Finish Kit to custom configurations. The options vary in their approach to agitation: the Form Wash’s automated impeller, a hand-sifting motion with the Form Finish Kit’s rinse basket and rinse bucket, or shaking a sealed container. For the best results, agitate parts in the IPA wash throughout the course of the wash cycle. When using the Form Finish Kit with the Form 1+ or Form 2, alternate between aggressively agitating parts and allowing parts to soak. Take care to protect delicate parts and features when agitating the IPA bath.

Formlabs offers multiple systems for part washing: the automated Form Wash, the Form 2 Finish Kit, and the Form 1+ Finish Kit.

Extending Solvent Lifetime

The IPA builds a higher concentration of resin after each wash, as liquid resin from each wash cycle builds up over time. As IPA becomes more resin-concentrated, a layer of diluted resin coats the outermost surface of printed parts after washing. As the part dries, the IPA evaporates and leaves behind a thin layer of liquid resin on the part’s surface, causing the surface to feel tacky. Thus, the part is only as clean as the cleaning solution. To achieve the cleanest parts, replace used IPA with fresh IPA frequently or consider a multi-step wash process.

Maintain separate wash buckets for each resin type or similar colors to preserve the best possible surface quality. Some resin is deposited on the part surface with each wash when using a single bucket for all resin types. When using a single wash bucket for multiple resin types, dark-colored materials, such as Black, Castable, and Tough Resins, will eventually deposit on the outside surface of parts printed in light-colored materials, such as White and Clear Resins. To preserve surface quality when washing parts with all resins in a single bucket, the IPA may require more frequent replacement to achieve the same surface quality as separate wash buckets.

The Form Wash hydrometer measures the quality of the IPA, based on the amount of resin in the bath. Tests have demonstrated that IPA can wash up to 200 parts before replacement, depending on the sequence, part size, and volume of IPA. Alternatively, the IPA’s lifetime can be extended by rinsing the part in stages.

Rinsing Parts in Stages – Optional

The part surface’s cleanliness depends on the cleanliness of the IPA. After removing the part from the IPA, the IPA evaporates and a trace amount of resin remains on the surface. In some cases, a second wash is beneficial. To improve the surface quality – for the best possible finish or for parts that are sticky or tacky to touch – initiate a second wash in cleaner IPA. Start the second wash immediately to avoid the residual resin coating curing in ambient light.

TIP: Consider using fresh IPA in a squirt bottle, like the type included with the Form Finish Kit, to gently rinse the outer surface of parts and hard-to-reach details. The squirt bottle method conserves IPA and can be used after washing parts in a bath.

Formlabs creates the color of each material by designing pigments or dyes in the formulation. Parts printed with pigmented resins, such as Color Resin, can be washed in the same container with low risk of the color staining the solvent, however, uncured resin may wash into the solvent. Rinse parts before washing, or use separate wash buckets to prevent parts printed in dark-colored resin from affecting the surface of parts printed with light colors.

For resins that use dye, such as Castable Resin, the dye from the printed resin stains the solvent. Therefore, use separate containers for dye-based resins and start with fresh IPA when switching from dye-based to pigment-based parts.

Considerations For Specific Geometries

Consider the specific geometry of each part when choosing a method to wash the part and the sequence of steps. Take special steps when washing parts that are large, hollow, concave or cup shaped, or have internal chambers or channels that will hold IPA, air, or uncured resin inside.

Hollow Geometries

Design hollow parts with drain holes for successful printing. During the washing process, the drain hole will allow the IPA to flow inside and clean the internal surfaces. Take care when removing hollow parts from the alcohol bath. Check to ensure that all IPA drains out of the chamber before transferring the part to another surface.

Internal Channels

Thin channels, such as those used in micro-fluidic designs, may not drain entirely on their own. Use a syringe, filled with clean IPA, to flush out internal channels. After cleaning, use compressed air to fully drain and dry the channel.

Large Parts

When using Form Wash and washing parts in the basket, parts will move around with the circulation of alcohol in the wash bucket. Check the path of the basket and inner lid to ensure that all parts can safely raise out of the bucket when the wash cycle completes and the basket raises. Parts that hang outside the basket perimeter may dislodge the inner lid when the wash cycle completes.

Concave Surfaces, Printed and Washed on the Build Platform

Hollowed parts – such as hollowed dental models – printed directly on the build platform can trap resin inside during the wash cycle, when washed on the build platform. Consider washing these parts in the Form Wash basket or adding a second wash cycle after removing from the build platform to remove uncured resin that is not removed when washing on the build platform.

Parts Larger than 1.8 L

IPA can overflow when washing parts that are larger than 1.8 L of enclosed volume. Every part will displace the same volume of alcohol when lowered into the wash bucket. Remove some IPA from the wash bucket before washing a large print.

Drying

Dry parts for at least 30 minutes after washing to allow the IPA to fully evaporate from the parts’ surface. Ensure appropriate ventilation while the IPA evaporates. Observe necessary safety precautions, according to the IPA supplier’s SDS. Options for drying include air drying or forced air. Forced air, such as a fan or clean compressed air, may dry parts more quickly.

WARNING: Be sure to check inside cavities and channels for uncured resin or liquid solvent. Remove residual liquid before drying to avoid fully or partially cured resin in unwanted areas. Compressed air may be helpful to empty internal channels before drying.

Once each part is washed and dried, check the specific material’s post-curing settings. Post-curing is optional for Standard Resins and required for many other materials to achieve their optimal properties.

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Form Wash System Overview