Guides
3D printing guide
Written for engineers choosing a process and preparing files for it. Covers FDM, SLA, SLS, MJF, and DMLS, the tolerances each holds, and the design rules that decide whether a printed part works.
Basic rules of 3D printing
Printing builds a part one layer at a time, upward. Nearly every design rule follows from the fact that each layer must be supported by the one beneath it.
Rules that follow from building in layers
On FDM and SLA an overhang beyond roughly 45 degrees from vertical needs support, and supports leave witness marks and cost time to remove. Powder processes need none.
- An overhang beyond roughly 45 degrees from vertical needs support on FDM and SLA. Supports leave marks and cost time to remove.
- Powder processes (SLS, MJF) need no supports, so overhangs and internal geometry are free.
- Strength is lower across layers than along them. Orient the part so load runs in plane, or say which direction carries load.
- Large flat areas parallel to the build plate tend to warp. Break them up or orient them at an angle.
Features and thicknesses
Layers bond to one another less strongly than the material within a layer, so a part loaded across the layers fails sooner than the same part loaded along them.
The bead or the cured line has width, and it is laid on the inside of an internal contour and the outside of an external one. Holes therefore print undersize and pins print oversize, typically by a tenth to a quarter of a millimetre depending on process. Anything that has to fit is either drilled or reamed after printing, or drawn with the offset already applied.
- Give every wall a real thickness. A surface with no thickness cannot be printed.
- Thin walls and tall thin features are fragile during printing and during support removal.
- Small embossed or engraved text needs adequate depth and stroke width to survive, and engraved usually survives better than embossed.
- Holes print undersize on most processes. Ream or model them oversize if the fit matters.
- On powder processes, enclosed cavities trap unsintered powder. Add escape holes.
Designing for the process you chose
The same model does not print equally well on every machine. A part designed around SLS, with internal channels and no draft, may be impossible on FDM without heavy support. Choose the process before finalizing the geometry, not after.
Our machine limits
| Process | Build volume | Layer | Minimum wall |
|---|---|---|---|
| FDM | 300 × 300 × 400 mm | 0.1–0.3 mm | 1.0 mm |
| SLA | 335 × 200 × 300 mm | 25–100 µm | 0.5 mm |
| SLS | 340 × 340 × 620 mm | 80–120 µm | 0.8 mm |
| MJF | 380 × 285 × 380 mm | 80–120 µm | 0.7 mm |
| DMLS | 250 × 250 × 325 mm | 20–60 µm | 0.5 mm |
Minimum embossed or engraved feature size is roughly 0.6 mm wide and 0.4 mm deep on polymer processes. Below that, detail closes up during finishing.
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Other 3D printing guides
Materials used in 3D printing
In printing, the material and the process are chosen together. A material is only available if a process can run it, so this is organized by process.
Basic rules of 3D printing
Printing builds a part one layer at a time, upward. Nearly every design rule follows from the fact that each layer must be supported by the one beneath it.
Good practices for 3D printing
Printing is forgiving of geometry and unforgiving of assumptions. These are the habits that avoid surprises.
Good practices for 3D printing
Printing is forgiving of geometry and unforgiving of assumptions. These are the habits that avoid surprises.
Preparing files
- Send STEP where possible. STL discards units and curves, and a coarse STL export shows as faceting on the printed part.
- If sending STL, export at a fine enough resolution that curved surfaces are smooth.
- Check the model is watertight before sending. Gaps and inverted faces cause slicing failures.
- State units explicitly. It is the most common cause of a part arriving at the wrong scale.
Choosing sensibly
Geometry that needs heavy support on FDM or SLA is often free on a powder process, so process choice and geometry should be decided together.
- Print for fit, form, and low volume. Mold for anything where tooling pays back across the volume.
- Do not specify a printing process by habit. State what the part has to do and let the process follow.
- Ask for a standard finish unless the part is cosmetic. Post-processing is often a larger cost than printing.
- Order a single part first when geometry is unproven, then the batch.
Avoiding rework
- Say which surfaces are cosmetic so support marks can be placed elsewhere.
- Design assembly clearance rather than relying on printed accuracy.
- If a printed part is a step toward a molded one, design it with draft and uniform walls from the start, so the same model can carry forward.
- Confirm color and finish expectations in writing. Dyed parts vary between batches.
How we work
Files are reviewed before anything is printed, and anything that will not survive the process is raised then rather than shipped and explained afterwards: unsupported overhangs, walls below the process minimum, and features that will close up in finishing.
Parts ship as-printed with supports removed and witness marks dressed. Bead blasting is standard on SLS and MJF, dyeing is available in black, and vapour smoothing, primer, and paint to a color reference are quoted on request. Turnaround is 2 to 7 working days on FDM and SLA, 5 to 10 on SLS and MJF, and 2 to 4 weeks on DMLS.
Common questions
How do you handle IP protection for uploaded CAD?
This is a question every buyer should ask and few suppliers answer clearly on the page. What matters is where files are stored, who has access, how long they are retained, whether an NDA is signed before or after quoting, and under which jurisdiction any dispute would be heard. Ask for those five answers in writing rather than accepting a general reassurance, from us or from anyone else.
More
Other 3D printing guides
Materials used in 3D printing
In printing, the material and the process are chosen together. A material is only available if a process can run it, so this is organized by process.
Tolerances in 3D printing
Printed parts do not hold tolerance the way machined parts do. Accuracy varies with the process, the material, the size of the part, and its orientation in the build.
Basic rules of 3D printing
Printing builds a part one layer at a time, upward. Nearly every design rule follows from the fact that each layer must be supported by the one beneath it.
Let’s get started on your part
Send your CAD files and target volumes. We come back with a price, a lead time, and any design notes that would reduce either.