3D Printing Design Guide: Nylon Material
This guide is written for design engineers and buyers who need nylon parts that hold tolerance and survive service loads. It covers wall thickness, hole sizing, thread design, warp control, and the point where a nylon part should be machined instead of printed. Read it and you can pick a process and set geometry with confidence.
What this guide covers
Nylon is tough, cheap to print, and unforgiving about geometry. Most failures trace back to a wall that was too thin, a hole that closed up, or a part that warped off the build plate.
Which nylon, and what it does well
Nylon is a polyamide. In 3D printing the common grades are PA12, PA11, PA6, and glass or carbon filled PA12. PA12 is the default for powder bed processes because it has low moisture pickup and a wide sintering window.
PA11 comes from castor oil and prints with slightly better elongation, which matters on snap fits and living hinges. PA6 and PA66 are stronger and stiffer but absorb more moisture, so a printed PA6 part can grow 0.5 to 1 percent after a few days in humid air. Filled grades add stiffness but reduce elongation.
Toughness is the reason engineers pick nylon over PLA or standard resin. A PA12 bracket can flex and return without cracking. Chemical resistance is good against oils and fuels, moderate against alcohols, and poor against strong acids.
- 1PA12Best all-round choice for SLS and MJF. Low moisture pickup, good dimensional repeat.
- 2PA11Higher elongation. Use where the part must bend or clip repeatedly.
- 3PA6 / PA66Stronger and stiffer, but moisture growth is a real problem on tight fits.
- 4Filled PA12Glass or carbon fill raises stiffness. Expect lower elongation and more abrasive wear.
Wall thickness, holes, and bosses
Minimum wall for SLS and MJF nylon sits around 0.8 mm, but a 1.5 to 2.0 mm wall is where the part behaves. Thinner walls cool fast, curl at the edges, and give you a floppy result. Thick sections above 4 mm hold heat in the core and risk internal porosity during sintering.
Holes come out undersized. The laser beam or fusing agent leaves a slight lip and unmelted powder clings to the bore. As a rule, add 0.2 mm to the diameter on holes under 5 mm and 0.3 mm on larger ones, then ream or drill critical bores. Below 1 mm diameter, expect the hole to close or fill with powder.
Bosses need support at the base. A boss with a wall thickness matching the main wall and a fillet of at least 0.5 mm at the root will survive handling. Drain holes in the boss top let trapped powder escape during cleaning. Skip them and you ship a part that rattles.
- 1Nominal wall1.5–2.0 mm is the sweet spot for stiffness and warp control.
- 2Hole compensation+0.2 mm under 5 mm, +0.3 mm above. Drill critical fits.
- 3Boss root fillet0.5 mm minimum. Sharp roots are the first thing to crack.
- 4Powder escapeAdd 2–3 mm drain holes in closed cavities and tall bosses.
Practical design limits for printed nylon
Values assume SLS or MJF with PA12. Tighten or loosen them depending on load direction and fit class.
| Feature | Design value | Notes |
|---|---|---|
| Minimum wall | 0.8 mm | 1.5–2.0 mm for parts that carry load |
| Maximum solid section | 4 mm | Above this, risk of internal porosity |
| Minimum hole | 1.0 mm | Below 1 mm it may close with powder |
| Hole compensation | +0.2 to +0.3 mm | Drill or ream fits tighter than ±0.1 mm |
| Minimum slot width | 0.6 mm | 0.8 mm if the slot is deep |
| Thread engagement | 2 × diameter | Use inserts for repeated assembly |
| Draft on vertical faces | 0.5° | Helps powder removal, not release |
| General tolerance | ±0.3 mm | ±0.1 mm achievable on small flat parts |
Threads, inserts, and fits
Printed threads work for one or two cycles. A formed thread in PA12 is soft, and the crest wears down after a handful of assembly passes. For anything that is opened more than three times, design a pocket and press in a brass heat-set insert. Set the boss outer diameter at roughly twice the insert diameter so the wall does not split on installation.
Snap fits need strain relief. Keep the cantilever strain below 1 percent for repeated use and under 2 percent for a one-time snap. Add a radius at the root and taper the beam toward the tip. A beam that is the same thickness along its length will concentrate stress at the base and break there.
Clearance fits behave differently than on machined metal. A printed nylon bore is not round to better than 0.1 mm, so a nominal 0.2 mm clearance can become an interference fit after moisture growth. Design 0.3 to 0.4 mm clearance for sliding fits, and test a first article before committing to a full run.
When to print nylon and when to machine it
Printing wins on organic shape, internal channels, and low volume. If a part has a lattice, a curved duct, or a geometry that would need five setups on a mill, printing is the cheaper path at 10 to 100 pieces. Printing also lets you combine a bracket and a clip into one part with no fasteners.
Machining wins on tolerance, surface finish, and material choice. A nylon bushing that must hold ±0.05 mm, or a part that sees continuous sliding wear, belongs on a lathe or mill. GreatLight machines nylon and other plastics to ±0.005 mm with finishes down to Ra 0.2–0.8 μm when the drawing calls for it.
A common pattern is to print the prototype, test the fit and function, then machine the production parts from PA or POM bar stock. The printed part proves the geometry in a day or two. The machined part holds the tolerance for the life of the product. Mixed approach, one supplier, less risk.
If you are unsure, send the drawing. We will flag thin walls, closed cavities, and features that cannot hold tolerance, then tell you which process gives the better part per dollar. Free DFM analysis comes back within 12 hours.
Common questions from engineers
How much does a printed nylon part shrink?
SLS and MJF nylon shrinks roughly 3 percent during cooling, and the machine software compensates for it. What you cannot compensate is uneven shrink from thick sections, which pulls the part out of shape.
Keep sections uniform and the as-built tolerance of ±0.3 mm is realistic on most parts.
Can I vapor smooth or dye a nylon part?
Dyeing works well and gives an even color through the surface layer. Vapor smoothing is not practical on nylon the way it is on ABS, because the solvents that attack nylon also soften the part.
For cosmetic parts, bead blasting gives a uniform matte finish and hides layer lines better than dye alone.
Why did my nylon part warp off the build plate?
Warp comes from a temperature gradient across the part. Long thin sections cool faster than thick ones and curl at the ends. Sharp corners concentrate the same stress.
Add ribs instead of thickness, round the corners, and orient the part so its longest dimension lies flat on the plate.
Is printed nylon food safe or biocompatible?
Standard PA12 powder is not certified for food contact or implant use. The porous surface traps bacteria and cannot be cleaned reliably.
If the application is medical, we machine the part from a certified grade under ISO 13485 and document the material lot.
What is the largest nylon part you can print?
Build volume depends on the machine, and large flat parts are limited by warp more than by envelope. Long thin panels above 300 mm usually need ribs or a split design.
Send the model and we will tell you if it fits one build or needs to be segmented and bonded.
Can printed nylon be machined afterward?
Yes, and it is common. Printed blanks are often face milled or drilled to bring a critical bore or mounting face into tolerance.
Machining a printed part works well on flat faces and through holes. Avoid machining thin printed walls, since the cut can chip or delaminate the sintered surface.
Send your nylon part for a free design review
Upload a STEP file and we will check wall thickness, hole sizing, and process fit, then quote printing or machining, whichever gives you the better part.
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