MJF is a forgiving process, but a little design for manufacture goes a long way towards a clean result. Getting wall thickness, hole sizes and clearances right means your part comes out strong, accurate and ready to use without the cost and delay of a second attempt. These are the details that quietly separate a part that just works from one that disappoints once it is in your hands.
The guidelines below apply to most PA12 work through our MJF & SLS printing service. If you would rather hand the whole design over and have it done properly from the start, our CAD team can prepare fully print ready files for you, with the rules already baked in.
Get wall thickness right
Very thin walls can warp or come out fragile, while overly thick solid sections waste material and trap heat during fusing, which can affect quality. For most parts a wall around one to two millimetres is a sensible minimum, with three millimetres or more in any structural areas that carry load. Getting this balance right pays off in both strength and cost across the whole part.
Where you need real stiffness, ribs are far more efficient than simply thickening a wall. A pattern of ribs adds rigidity without the material cost or the heat build up of a solid block, and it keeps the part lighter, which also helps with nesting and price when you come to order a batch. As a simple starting point, aim for uniform walls wherever you can, since sudden jumps from thick to thin sections cool at different rates and can leave visible sink marks or slight distortion. If a thick boss is unavoidable, shell it out and add ribs so the wall stays roughly even throughout the part.
Holes, pins and small features
Small holes can close up slightly during fusing, so it pays to design holes a touch oversize or to plan on drilling any critical bores to their final size after printing. Tall, thin pins are best avoided wherever possible, as they are weak and can break during powder removal and handling before the part ever reaches you.
Embossed and engraved text both work well in MJF, which is genuinely handy for part numbers, logos and branding, provided the features are not too fine to resolve. Keeping such detail above a sensible minimum size ensures it survives blasting and stays legible for the life of the part.
Orientation and warping
How a part sits in the build affects both its accuracy and its finish, so it is worth thinking about before you commit. Large flat areas are more prone to slight curling than compact shapes, and adding ribs or gentle curves stiffens those panels so they hold their form through fusing and cooling.
We handle orientation for you on every job, balancing accuracy, finish and packing density to get the best overall result. If a part has a critical face or a feature that must stay crisp, tell us and we will position it in the build to favour that requirement.
Clearances for moving and assembled parts
MJF can print assemblies and moving parts in place, which is one of its more impressive tricks, but they need the right gap so the powder clears out and the parts actually move freely afterwards. Plan these clearances deliberately rather than hoping a default works, because trapped powder can lock an assembly solid.
- Allow around 0.4 to 0.5mm clearance for moving parts.
- Add escape holes so trapped powder can be removed.
- Avoid fully enclosed hollow voids with no exit.
- Test snap fit clearances with a small sample first.
Let us review your model
Send your file through and get a quote and we will check wall thickness, holes and clearances before anything is committed to the build. Catching a problem on the screen is always far cheaper and faster than catching it on the bed, and our review of these details comes as standard.