Designing for 3D printing
From wall thickness to fit clearances, from hole diameters to print orientation; what you need to know for your part to print right the first time.
Quick reference
| Guideline | FDM | SLA | SLS | MJF | PolyJet | SLM / DMLS |
|---|---|---|---|---|---|---|
| Minimum wall thickness | 0.8 mm | 0.5 mm (supported) / 1 mm | 0.7 – 1 mm | 0.5 – 1 mm | 1 mm | 0.4 – 1 mm |
| Smallest detail | 0.4 mm (nozzle diameter) | 0.2 mm | 0.5 mm | 0.5 mm | 0.3 mm | 0.6 mm |
| Minimum hole diameter | Ø 2 mm | Ø 0.5 mm | Ø 1.5 mm | Ø 1 mm | Ø 1 mm | Ø 1.5 mm |
| Overhang angle | ≥ 45° from horizontal; flatter surfaces need support | ≥ 30° from horizontal; flatter surfaces need support | Unlimited (no supports needed) | Unlimited | Unlimited (gel support) | ≥ 45° from horizontal; flatter surfaces need support |
| Clearance for moving parts | 0.3 – 0.6 mm | 0.2 – 0.4 mm | 0.5 mm (moving parts) | 0.4 – 0.6 mm | 0.2 mm | 0.3 mm |
| Text and logos | Embossed ≥ 0.6 mm, engraved ≥ 0.8 mm | Embossed ≥ 0.3 mm, engraved ≥ 0.4 mm | Embossed ≥ 1 mm | Embossed ≥ 1 mm | Embossed ≥ 0.5 mm | Embossed ≥ 0.5 mm |
| Escape hole | — | Ø 3.5 mm drain hole in hollow parts | At least two Ø 5 mm powder escape holes in hollow parts | Ø 5 mm powder escape hole | — | — |
| Typical tolerance | ±0.5% (lower limit ±0.5 mm); industrial ±0.3% | ±0.15 – 0.5% (lower limit ±0.1 mm) | ±0.3% (lower limit ±0.3 mm) | ±0.3% (lower limit ±0.2 mm) | ±0.1 mm | ±0.1 – 0.2 mm |
Values are starting points; they vary with machine, material and geometry. When you send your file, our engineers check its manufacturability.
If walls are too thin they break, bend or fail to form during printing. Walls connected on two sides (supported) can be thinner than walls connected on one side (unsupported). In FDM, choosing wall thickness as a multiple of the nozzle diameter (0.4 mm → 0.8 / 1.2 / 1.6 mm) gives the cleanest result.
In FDM and resin printing each layer is built on top of the previous one. Surfaces flatter than 45° from horizontal (overhangs) need supports; surfaces at 45° or steeper print without supports. Horizontal sections spanning mid-air between two points (bridges) can usually be printed unsupported up to 10 mm in FDM. Powder bed technologies (SLS, MJF) need no supports.
Small holes shrink slightly when printed. Because the top of a horizontal hole forms an overhang, it can be designed as a teardrop in FDM. Bringing holes that need precise diameters to size by drilling or reaming after printing is the most reliable approach.
Parts that fit into each other or move relative to each other need clearance; otherwise they can fuse together or assembly becomes difficult. The clearance is chosen according to the technology and the type of fit.
For embossed and engraved text, letter thickness and depth must be above the technology's smallest detail value. Fonts with consistent stroke width and no serifs come out cleaner. Keep the width-to-depth ratio around 1:1.
FDM parts are weaker between layers (Z axis) than within the layer plane (XY). In load-bearing areas, choose a print orientation that keeps the force parallel to the layer lines. Clips, hooks and thin protrusions are the areas most prone to breaking along the layers.
Sharp internal corners cause stress concentration and cracking; on large flat surfaces sharp corners increase warping. Adding fillets to internal corners and chamfers or fillets to external corners improves both strength and print quality.
Small threads printed directly in plastic parts wear quickly. For connections that are taken apart often, heat-set brass inserts, nut traps or self-tapping screws are more durable. Printed threads generally work well from M6 upwards.
In resin and powder bed technologies, hollow designs save material and cost; however, the liquid resin or powder trapped inside must be drained. At least two escape holes are needed for this. In FDM, hollowing is handled automatically by the infill ratio.
Parts larger than the build volume can be split into several pieces and joined. Adding dovetails, pins or locating features at the split lines makes alignment easier. At TAİ Robotik, large parts are often produced in one go on high-capacity industrial FDM machines.
Materials such as ABS, ASA, PC and nylon shrink as they cool; the corners of large, flat parts can lift off the bed. Breaking up long flat surfaces with ribs, rounding corners and using uniform wall thickness instead of thick blocks reduce warping.
STL, OBJ and 3MF files are used for printing; STEP is ideal if dimensions need checking or editing. When exporting STL, too low a resolution makes surfaces faceted and too high makes the file unnecessarily large. The model must be closed (watertight, manifold) and units must be millimeters.
Good to know
Generally 0.8 mm (supported) and 1.2 mm (unsupported) for FDM, 0.5 mm and 1 mm for SLA, and 0.7 – 1 mm for SLS/MJF. Thicker walls are recommended for load-bearing parts.
In FDM, about 0.3 mm clearance for a tight fit, 0.4 mm for a normal fit and 0.6 mm for a loose fit is a good starting point. 0.2 – 0.4 mm is enough in resin printing.
STL, OBJ and 3MF are enough for printing. If dimension checks or edits are needed, we recommend also adding the STEP file.
Design overhangs at least 45° from horizontal, avoid long bridges and draw horizontal holes as teardrops. Powder bed technologies (SLS, MJF) need no supports at all.
Upload it and our engineers will check its manufacturability and prepare your quotation.