Tips and tricks for 3D printing resin and supports

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  Key takeaways
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  Pick the orientation before you touch a support
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  Set exposure in bands, then dial in
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  Support contact size, density and placement
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  Hollow parts need drain and vent paths
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  Wash, remove supports, then post-cure
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  Step by step: from file to finished part
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  Choosing settings by part type

Orientation decides where supports touch, how much cross-section each layer has, and how hard the part is to clean. A flat part lying on the build plate has a large first-layer area. That area peels hard, and the peel force distorts the bottom face. Tilt the same part 20 to 35° off the plate and the cross-section per layer drops sharply. Peel force drops with it.

The tilt angle is a trade-off, not a rule. More tilt means smaller layers and less distortion, but it also means more supports and a longer print. For a part under 50 mm tall, 20 to 25° is usually enough. Taller parts, or parts with a large flat face, need 30 to 35° so the flat face does not run parallel to the plate.

Keep critical faces away from the plate. A face that must sit flat against a mating surface should point up, or at least sideways. Downward-facing details that touch supports will show witness marks. If that face is a seal groove or a bearing seat, orient it so supports land on a non-critical surface instead.

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  Avoid large flat areas parallel to the platePeel force scales with cross-section. Tilt until the projected area per layer is small.
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  Point cosmetic faces upUpward faces cure against air and stay smooth.
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  Check the tallest cross-sectionIf one layer is much larger than the rest, that layer is where the part will tear.

Resin exposure is not a single correct value. It depends on layer height, resin color, printer light source and temperature. Start with a band, print a test, then move in 0.1 s steps. For 405 nm LCD printers at 50 μm layers, normal exposure usually lands between 1.8 and 2.5 s. At 100 μm layers, 2.5 to 3.5 s is a common range.

Bottom layers are different. They bond to the build plate and must survive the first several peels. Six to eight bottom layers at 20 to 30 s is a normal starting point. Too few bottom layers and the part breaks free mid-print. Too many and the raft is hard to remove without cracking the part.

Temperature matters more than most people expect. Resin at 20 °C cures slower than resin at 28 °C. If a print that worked in summer fails in winter, warm the resin to 25 to 30 °C before starting. A small heater in the enclosure is enough.

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  50 μm layersNormal 1.8 to 2.5 s. Bottom 20 to 30 s.
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  100 μm layersNormal 2.5 to 3.5 s. Bottom 25 to 35 s.
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  Clear and white resinsNeed more light penetration control. Test before committing to a long print.

Support tips do two jobs. They hold the part against peel force, and they break away cleanly at the end. A tip that is too small fails mid-print. A tip that is too large leaves a crater you cannot sand out on a small feature. For most engineering parts, 0.2 to 0.4 mm contact tips are the working range.

Tip size should follow the feature it touches. A 0.2 mm tip is enough for a 1 mm boss or a thin rib. Use 0.4 mm tips under heavy overhangs and at the start of a bridge. If a support lands on a cosmetic face, drop to 0.2 mm and add a second support nearby instead of enlarging the first.

Density is about peel load, not coverage. Random supports at 60 to 70% density under a heavy region are stronger than a sparse grid. For islands that appear mid-print, place a support directly under the island. Do not rely on a nearby support to catch it.

Add bracing between tall supports. A single 40 mm support column will flex during peel. Two columns joined by a cross brace resist that flex. This is the most common cause of a clean-looking model that shifts halfway up.

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  Contact tip range0.2 to 0.4 mm for most parts. Smaller for fine features, larger for heavy overhangs.
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  Add raft clearanceKeep the first support contact 0.2 to 0.3 mm above the raft so it does not weld.

Hollowing saves resin and reduces peel force, but it creates a closed volume. Uncured resin trapped inside will slowly leak, swell the part and ruin the surface weeks later. Every hollow part needs at least two openings. One at the lowest point during printing, one at the highest.

Wall thickness of 2 to 3 mm works for most parts up to 100 mm. Thinner walls flex during peel and can crack at support contact points. Thicker walls waste resin and add weight without adding much strength.

Drain holes should be 3 to 5 mm for small parts and 6 to 10 mm for large ones. Place them where they will not show after assembly, or where you can plug them with a matching pin. After printing, drain the part for several minutes, then flush with IPA before post-curing. If the part still feels heavy, it is not empty.

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  Two holes minimumOne low, one high. A single hole traps air and blocks drainage.
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  Wall thickness2 to 3 mm for parts up to 100 mm. Thicker for larger parts.

Order matters in post-processing. Wash the part in IPA before removing supports. Soft, partially cured supports bend instead of snapping, and bending pulls resin away from the surface. Two washes of 3 to 5 minutes each in clean IPA work better than one long wash in dirty IPA.

Remove supports with flush cutters, not pliers. Cut at the contact tip, not at the part surface. Then sand the nub with 400 grit, followed by 800 grit if the surface is visible. Let the part dry fully before post-cure. Trapped IPA will boil and blister the surface under UV.

Post-cure time depends on resin and part thickness. A common range is 2 to 5 minutes per side in a 405 nm cure station, or 30 to 60 minutes in sunlight. Over-curing makes the part brittle and yellow. Under-curing leaves a tacky surface. Test on a small coupon first.

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  Wash first, cut secondSupports snap cleanly only after the surface resin is gone.
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  Dry before UVAny IPA left inside a hollow part will blister during cure.