A nylon bracket that passed a bench test can still fail in the field if it was built in the wrong orientation, and a part that measured correctly on the first order can arrive noticeably different on the fifth. Powder-bed nylon is one of the few additive routes that carries real service loads, which is also why it deserves more specification attention than the average prototype. This guide covers what to send with an SLS 3D printing service request, how powder choice and build orientation decide strength, how to keep repeat orders consistent, and what a first article should prove before a part is trusted in an assembly.
What should you send with an SLS request?
Send the load case, not just the geometry.
Nylon has enough design freedom that the wrong build orientation can halve the useful strength of a part, so the request should state how the part is loaded and where it must not distort.
A STEP or IGES file gives the shop the shape; the note attached to it gives the shop the intent. Nylon parts are frequently used as functional brackets, housings, latches, and fixtures, and each of those fails differently. A part in bending is sensitive to where the layer planes fall; a part in a sliding interface is sensitive to surface finish and to how much material is left for a machined face; a part that must hold a screw thread needs wall thickness behind the thread.
Four items lift a request out of guesswork. State the load case in one sentence: what pushes, pulls, or vibrates against the part. List the interfaces that must fit other components and how tightly. Say whether the part will be handled repeatedly, since that changes the powder recommendation toward impact-tolerant grades. And say whether this is a one-off or the first of a repeat series, because repeated orders justify recording build parameters that a single prototype does not need.
Accepted formats at 6CProto include STEP, STP, IGES, IGS, SLDPRT, 3DM, SAT, and X_T, and each request is reviewed for manufacturability before production so that geometry problems surface before a build is scheduled. The terminology used to describe powder-bed processes on the drawing follows the additive manufacturing vocabulary maintained by ASTM F2792.
Which nylon powder matches the load case?
Start from stiffness, impact, and heat, in that order.
Unfilled PA12 covers most functional parts, PA11 and elastomeric grades absorb impact, and filled grades add stiffness at the cost of elongation and surface quality.
The powder choice decides how a part behaves long before the geometry does. Unfilled PA12 is the default functional nylon: it is stiff enough for brackets and housings, tolerates repeated handling, and finishes predictably. PA11 and elastomeric powders shift the balance toward impact energy and elongation, which suits parts that will flex, snap, or take a hit in service. Glass-filled grades raise stiffness and reduce creep under sustained load, at the price of lower elongation, more abrasive wear on secondary operations, and a rougher surface after blasting.
Two secondary properties often decide the final choice. Heat tolerance matters for parts close to electronics or in an engine bay, and it varies enough between grades that the service temperature should be stated rather than assumed. Surface behaviour matters where the part slides or seals, because a filled nylon’s texture is different from an unfilled one after the same finishing step.
Published powder properties from platform and material suppliers, including the powder-bed documentation from EOS and 3D Systems, give a comparable starting point for those trade-offs, and the vocabulary used to describe them follows the standards work coordinated through ASTM committee F42.
| Powder | Behaviour that decides the choice | Typical parts |
|---|---|---|
| Unfilled PA12 | Balanced stiffness, toughness, and finish | Brackets, housings, enclosures, fixtures |
| PA11 | Higher elongation and impact absorption | Clips, covers, parts exposed to drops |
| Glass-filled nylon | Stiffness and creep resistance | Load-bearing brackets, stiffening structures |
| Elastomeric / TPU powders | Flexibility and damping | Gaskets, grips, soft-touch interfaces |
| Flame-retardant grades | Compliance-driven behaviour | Housings with a flammability requirement |
How does build orientation change strength and tolerance?
Nylon is stronger along the layers than across them.
Fusing is directional, so a part built flat resists in-plane loads well and can delaminate where a load pulls the layers apart, and orientation also decides which face cools into tolerance.
Powder-bed parts are built by fusing one layer onto the previous one, and the bond between layers is weaker than the material inside a layer. In practice that means a bracket designed to carry a load in the plane of the layers behaves close to the published material properties, while the same bracket built standing on end may fail along a layer boundary under the same load. The orientation decision is therefore a strength decision, and it belongs in the DFM conversation rather than in the machine queue.
Orientation also drives dimensional spread. Long, thin sections cool unevenly and can curl or bow, so a part with a large flat face is usually built at an angle to distribute shrinkage. Where a critical feature sits near the build platform, the thermal history is different from the top of the part, which can matter on tight callouts. Building several parts in the same bed spreads cost, but neighbours change the cooling environment, which is one reason a packed bed and a single-part bed can produce slightly different dimensions.
For functional nylon parts, the practical rule is to orient for the load path and accept the finishing consequences, then record the orientation so the second order matches the first. The geometry rules that interact with orientation, from minimum wall thickness to powder escape paths, are collected in the 3D printing design tips library.
What tolerance and feature limits should the drawing set?
Set tolerances where the part interfaces with others.
Powder-bed nylon holds a general range comfortably but not a uniform one across a large part, so tight callouts belong on mating features rather than on every surface.
Three effects combine on a nylon part. Thermal shrinkage during cooling varies with geometry, so a long dimension accumulates more variation than a short one. Surfaces arrive with a matte texture, so any face that must seal or slide is normally machined or finished afterwards. Small features, thin ribs, and small holes near the powder particle scale can distort or partially fuse, which is a resolution limit rather than a tolerance question.
Drawings that work well in practice identify a datum from the function, apply a general tolerance to the rest of the part, and reserve tight callouts for the interfaces that mate. Features that must be exact are commonly designated for machining after printing, which is a normal hybrid route and worth flagging in the request. Whether a specific callout is achievable depends on the geometry and the powder, so the achievable range for a given feature should be confirmed against 6CProto’s tolerance framework before the drawing is released.
How do you keep repeat SLS orders consistent?
Freeze the grade, orientation, and finishing recipe.
A repeat nylon batch varies with powder condition, bed position, and cooling, so the parameters that produced an approved part have to be recorded and repeated rather than re-decided.
This is the part of an SLS program that buyers underestimate, and it is the reason to treat the first order as a reference build rather than a sample. Four variables carry across orders: the powder grade and its condition, the build orientation and bed position of the part, the finishing steps applied after blasting, and the inspection method used to accept the first batch. Record them and a reorder becomes a production task; leave them unrecorded and a reorder becomes a new project with a new set of results.
Nylon is well suited to repeat runs because the process is largely automatic once parameters are fixed, which is what allows SLS to bridge the gap between prototypes and volume production. The practical consequence for a buyer is that the second order deserves a short confirmation message rather than a fresh discussion: same grade, same orientation, same finish, same acceptance criteria. That message is the difference between a batch that fits and a batch that needs rework.
Where a program will run for months, it is worth asking for those parameters to be held against the part number so they survive a change of project manager on either side.
What drives SLS part cost?
Bed volume, packing, and hand work set the price.
Machine time is shared across everything in the build chamber, so cost per part falls sharply with packing density and with quantity, and post-processing is priced in labour.
The largest input is the build cycle, and it is shared. Parts that nest efficiently, or that can be placed inside the unused space around larger components, cost less per unit than the same part built alone. Tall parts consume height that cannot be recovered, which is why a design that reduces overall height without changing function often reduces price as well.
The second input is post-processing. Blasting removes caked powder and evens the surface, dyeing adds colour, sealing closes porosity, and any machined interface adds a setup. Each of these is labour, and each is optional depending on the application. A part that will be hidden inside an assembly rarely needs the finish that a customer-facing housing requires.
The third input is specification quality. A part that has to be reprinted because a tolerance was unmeasurable or an orientation was wrong costs a full build, and on short runs that single event dominates the total spend. The most reliable cost reduction is a DFM review that catches the geometry and orientation problem before the machine is loaded.
What does a first article sample prove?
It proves the process, not just the drawing.
A first article confirms that the chosen powder, orientation, and finishing route produce a part that meets the interfaces, and it establishes the reference that later batches are compared against.
A useful first article answers four questions. Does the part assemble with the components it meets, in the order the assembly is built? Do the controlled dimensions land within the agreed range, measured by the agreed method? Does the surface finish suit the function, particularly on sliding or sealing faces? And is the part strong enough in the direction it will be loaded, which is sometimes only revealed by a functional test rather than by measurement.
The output of that review should be a decision, not a document. Either the parameters are frozen and the part is approved for repeat orders, or a specific change is agreed and one more sample is built. Approving a first article without recording its parameters leaves the next order to chance, which is how programs end up with a batch that measures differently from the sample that was signed off.
6CProto runs powder-bed processes in the same facility as its machining and finishing operations, which means any interface that needs to be machined after printing can be handled inside the same order and checked before shipment.
What belongs in the SLS inspection report?
Report the interfaces, the finish, and the method.
A nylon part report is most useful when it covers the dimensions that matter, the appearance standard under a stated condition, and the functional checks that a caliper cannot capture.
Dimensional results should name the features measured and the method used, so a second inspector can repeat the same judgement. Appearance should be assessed against a defined viewing condition rather than a general statement, because a blasted nylon surface looks different under direct light and diffuse light. Functional checks, such as a boss accepting its screw or a clip engaging its mating feature, catch the failures that dimensional inspection misses. Where a program needs to relate inspection results to published capability, the measurement methods used across additive processes are described in the NIST additive manufacturing program.
For parts that will be sealed, pressure-tested, or used in a fluid path, the test conditions belong in the report as well, since a result without its conditions cannot be compared to a later batch. 6CProto provides quality inspection reports on request and assigns a dedicated project manager to each order, so the reporting format can be agreed during the DFM review.
When should you choose MJF or SLA instead?
Change process when the requirement changes, not the price.
MJF suits the same nylon parts when batch consistency and fine functional detail matter more, and resin wins when the part is judged on surface smoothness or fine feature resolution rather than on load.
MJF and SLS produce parts from similar nylon powders, and the differences that matter to a buyer are repeatability, surface texture, and detail resolution rather than a material substitution. Where a program needs consistent output across many builds, MJF’s more tightly controlled process is often preferred, and the platform documentation published for HP Multi Jet Fusion describes how those build parameters are managed; where a shape needs the design freedom of a powder bed at lower volumes, SLS is the practical route.
Resin is the right switch in the other direction. If the part is an appearance model, a flow-visualization part, or a component where fine detail and a smooth surface matter more than impact, then SLA resin printing produces a better result, and nylon’s advantages in toughness and thermal behaviour are simply not being used.
The comparison that matters is not which process is generally better. It is which of the two will still be right when the part is ordered again in three months. The wider process trade-offs are set out in the 6CProto guide to SLA, SLS, and MJF for functional testing.
Specifying nylon so the second order matches the first
SLS earns its place on parts that carry a load, and it rewards specification discipline in three places. The powder grade has to match the load case rather than the appearance. The build orientation has to follow the load path, which means telling the shop how the part is loaded. The finishing and inspection steps have to be recorded, because a nylon part is only repeatable if the recipe behind it is repeatable.
Where those three items are in place, powder-bed nylon is one of the most practical routes from prototype to production: no tooling, no support removal, and functional properties close to an injection-molded part at low volume. Where they are missing, the same process produces parts that pass on the bench and move in service. The difference is rarely in the machine.
FAQ
How much does SLS 3D printing cost?
Price follows bed usage rather than material weight. The machine cycle is shared by everything in the build chamber, so cost per part depends on how much height and volume the geometry consumes, how efficiently parts pack together, and how much labour the finishing requires. A part that nests with others and receives a blasting finish only costs considerably less per unit than the same part built alone and dyed. Send the quantity and the finish requirement per surface, and the quote can reflect the actual build.
Can SLS nylon parts be tapped and threaded?
They can be tapped, and it is common practice on low-volume functional parts. The thread should be modelled as a pilot hole sized for the tap, with enough wall thickness behind it to carry the load, because a thread cut into a thin nylon wall strips easily. Where the joint will be assembled repeatedly, a metal insert or a captured nut is more durable. Both approaches need clearance in the model, so confirm the hardware in the DFM review.
Do SLS parts need support removal?
No supports are built, so there is no removal step and no support scars. The equivalent operation is powder removal: loose powder is cleared from internal passages and recesses, and caked material is blasted away. Parts with enclosed volumes need escape paths designed in, because powder trapped inside a sealed cavity cannot be extracted later. This is one of the geometry rules worth raising during the manufacturability review.
How do you specify colour and sealing on a nylon part?
Colour is usually achieved by dyeing after blasting, which penetrates the surface rather than coating it, so the part keeps its texture and does not chip in the way a painted surface can. Sealing is specified separately and is relevant where the part holds fluid, sees pressure, or must be cleaned. Both steps change the surface and therefore any dimensions measured afterwards, so specify them before production rather than after the first batch is inspected.
If a nylon part has to survive a real load and be ordered again later, send the model with the load case and the interfaces that matter. 6CProto reviews manufacturability before production and returns a DFM report with the quote, so powder choice and build orientation are settled before the first build. Upload the file at the 6CProto quote page or send it to projects@6cproto.com.