A production line always has small needs, such as a nest that holds the part during inspection, a drilling template, a guide for applying a label or a holder for a tool. Machined from aluminium or POM, parts like these need CAM programming and machine time, and the cost is high compared with the job they do. In SLS the shape of the part comes straight from CAD, with no CNC programming.
Unlike metal, nylon does not scratch painted or anodised surfaces. It is also light and does not rust. For fixtures that have to be stiff or sit near heat sources there are the reinforced grades PA12 GF, with glass, and PA11 CF, with carbon fibre. According to the Formlabs data sheets, PA11 CF has a tensile modulus of 5.3 GPa in the X direction, against 1.85 GPa for standard PA12.
On robots and manipulators mass matters, because a lighter gripper allows higher accelerations or a larger payload on the same robot. In SLS, vacuum channels can be built directly into the gripper body. Sections with no structural role can be hollowed out, and several parts can be combined into a single part.
Why SLS
- The shape of the nest is taken directly from the part model, with the clearance you want, without CNC programming.
- Internal channels for vacuum or compressed air are printed directly into the body of the part.
- Nylon does not scratch the parts it holds and is much lighter than aluminium.
- Locating pins, threaded inserts and metal bushings are easy to integrate, as the Formlabs design guide also recommends.
- The reinforced grades (PA12 GF, PA11 CF) are stiffer and have a higher heat deflection temperature than PA12.
Parts we often print
- Nests for measurement and visual inspection
- Drilling and positioning templates for assembly
- Robot gripper fingers and jaws shaped to the part
- Vacuum gripper bodies with integrated channels
- Guides for applying labels or adhesive
- Holders for tools, scanners and cameras on the line
- Protective covers for sensors mounted on machines
Design tips
- For precise location, use steel dowel pins pressed into reamed holes instead of printed pins. Formlabs recommends slightly undersize holes, brought to size with a reamer.
- For screws that are tightened and undone often, use heat-set brass threaded inserts instead of printed threads.
- Holes and pins come out most accurately with their axis vertical (Z) during printing. Mark in your request which holes are critical, so that we can take them into account when choosing the orientation.
- Internal vacuum channels need open ends so that the powder can be removed. Avoid long, thin channels with many bends, because powder is hard to get out of them.
- PA12 GF is more brittle than PA12, especially between layers. Make fine features thicker and do not put clips on parts in this material.
The full rules are in the SLS design guide.