Design guidelines

Quick reference

Thinnest wall

0.8 mm (1.2–2 mm for everyday parts)

Material around a hole or between holes

At least 1 mm

Screw clearance hole

Screw size + 0.4–0.6 mm (M3 → 3.4 mm)

Sliding fit (lids, slots)

About 0.25 mm gap per side

Overhangs without support (plastic)

Up to about 45° from vertical

Largest plastic part in one piece

325 × 320 × 325 mm

Largest resin part in one piece

230 × 144 × 350 mm

Larger parts

Split into up to 16 pieces

Colors in one plastic part

Up to 5

Walls and thin features

• Minimum wall: 0.8 mm. That’s two lines of plastic, the thinnest wall we print reliably. It’s fine for covers and boxes that carry no load. 1.2–2 mm is a good everyday wall; 3 mm and up for parts that carry load.
• Leave at least 1 mm of material between a hole and an edge, and between two holes. More is stronger: for a screw that’s tightened hard, leave about one screw diameter.
• Thin pins, tabs and posts stick out and snap easily. Make them thicker than you think, add a fillet where they meet the body, and keep tall thin posts short.
• Fillets on inside corners spread the load. A bracket with a rounded inside corner is much stronger than one with a sharp 90° corner, because cracks start at sharp corners.
• Text and logos: raised (embossed) text prints more cleanly than cut-in text. Keep letter strokes at least 0.8 mm wide; letters about 5 mm tall and up read well. For the finest text, choose resin.

Print direction and strength

Plastic (FDM) parts are built in layers, and they’re strongest along the layers and weakest across them, where one layer can peel from the next. Think of a stack of paper: easy to split apart, hard to tear across.

• Example: an L-bracket printed lying on its side has layers running around the bend and is far stronger than one printed standing up, where the bend sits across the layers.
• We print your part the way it sits in your file, unless lying it on another side needs less than half the support. Slicer projects (3MF) always keep your orientation. So if direction matters for strength, save your file the way it should print.
• Choose a stronger setting for parts under load: Strong adds walls and fill, Heavy is nearly solid. Most strength comes from the walls, so a thicker wall in your design helps as much as a higher setting.
• Resin parts are solid and nearly equally strong in every direction.

Holes, clearances and fits

Printed holes come out slightly smaller than drawn, and parts that fit together need a little room. Draw clearance holes for screws a bit larger than the screw:

• Sliding fits (a lid, a part in a slot): leave about 0.25 mm per side. Our Parts Builder uses 0.25 mm for its lift-off lids.
• Press fits (a pin, magnet or bearing pushed in) depend on the material and size. Print one test part first, or draw the hole a little small and ream or drill it to size afterward.
• Sideways holes (running horizontally) print slightly less round than vertical ones, and big ones need support inside. A teardrop or diamond-shaped top lets them print without support.
• Screws into plastic: for self-tapping screws, draw the hole near the screw’s core diameter (about 2.5 mm for M3) and let the screw cut its thread. For parts taken apart often, use heat-set threaded inserts: draw the hole to the insert maker’s size. Printed threads work for large sizes (about M8 and up); small threads are better tapped or inserted.
• Two printed parts that fit together: leave a gap of about 0.2–0.3 mm per side for a snug fit, more for a loose one. In resin the gaps can be smaller.

Clips, snap-fits and hinges

• Snap-fits and clips need a material that bends before it breaks: PETG in plastic, Tough resin for small, detailed ones. Avoid PLA and carbon fiber plastics for anything that flexes.
• Make the flexing arm long and thin rather than short and thick, and add a fillet where it joins the body.
• Print clips so the arm flexes along the layers, not across them (see print direction above).
• Thin “living” hinges (one thin strip that folds) don’t last long in rigid printed plastic. Use a pin hinge, or a flexible material such as TPU.

Overhangs and supports

• Plastic (FDM) prints build up from the bottom. Faces that lean out more than about 45° from vertical, and bridges over open space, need temporary supports underneath.
• Supports leave rougher marks where they touched. Keep the faces that need to look good facing up or vertical.
• Chamfers instead of rounds: a 45° chamfer on the underside of a ledge prints cleanly without support, where a rounded edge would not.
• Short bridges (a flat span between two supports, like the top of a slot) print fine without support; long ones sag.
• Parts that would need support everywhere (sculpted shapes with no flat base, thin curved shells, parts designed for injection molding) often come out better in resin.
• Supports are included in your price: a part that needs less support costs less.

Maximum sizes

• Plastic (FDM): 325 × 320 × 325 mm (12.8 × 12.6 × 12.8 in) in one piece; 300 mm wide when a separate breakaway support material is needed.
• Resin (SLA): 230 × 144 × 350 mm (9.1 × 5.7 × 13.8 in) in one piece.
• Bigger parts can be printed in up to 16 pieces. The seams show and we don’t glue the pieces together; the price page shows how it would be split and asks you to confirm. If you can, split it yourself at a natural line and add pins or a lap joint so the pieces line up.
• Parts Builder parts: up to 250 mm on the longest side.

Warping on large and long parts

Some plastics shrink as they cool, which can lift the corners of big parts. In our production this matters for ABS, ASA and polycarbonate. PLA and PETG print flat at any size.

• Long, narrow parts (at least 2.5× longer than wide): risk above 120 mm. Sharp corners make it worse.
• Round parts: risk above 200 mm across.
• Other shapes: risk above 180 mm, or when the part covers more than half the build plate.
• A project with several separate parts is judged part by part, not by the size of the whole group.

When a part is at risk, the price page suggests a fiber-filled plastic that stays flat: PET-CF (stiff), PET-GF (tougher) or Nylon CF (heat). Rounded corners also help.

Designing for resin

• Resin captures far finer detail than plastic: small text, sharp edges and textures come out crisp, with almost no visible layers.
• Resin parts are always solid, so very large, bulky resin parts cost more. Big simple shapes are usually better value in plastic.
• Supports touch the underside and leave small marks; we orient parts to keep them off the faces that matter. Sanding removes them.
• Most resins soften around 50–65 °C. For heat, see High-Temp and Tooling resin, or choose plastic.

How to lower the price

• Choose the lowest strength that does the job: Economy or Balanced for models and prototypes.
• Choose PLA when the part has no heat, outdoor or impact needs.
• Give the part a flat base and avoid big overhangs, so it needs less support.
• Order several at once: the price per part drops from 5 parts and the setup is shared.
• Multi-color: color in a few spots costs far less than a color change on every layer.
• Hollow out bulky parts in your design (keep walls thick enough), especially in resin, which prints solid.