In a drone or a mobile robot, every plastic part is a compromise between mass and shock resistance. SLS allows geometries that would be impossible or expensive to machine, such as internal ribs, hollowed sections and lattice structures, and makes them from materials that do not shatter on a hard landing.
PA11 is the usual choice for parts that take impacts, because it has an elongation at break of 40% and a notched Izod impact strength of 71 J/m, against 11% and 32 J/m for PA12 (Formlabs data sheets). PA11 CF adds stiffness for arms and frames. TPU 90A is an elastomer used for vibration dampers, guards, feet and gripper fingers that have to conform to the object.
For grippers and end effectors, SLS allows print-in-place mechanisms and lattice structures that act as springs. Formlabs recommends lattice openings of at least 8 mm and open faces, so that the powder can be removed. Below that size, powder stays trapped inside and the part comes out heavier than you calculated.
Why SLS
- The strength-to-mass ratio is good, especially with PA11 CF and hollowed sections.
- Lattice structures and organic shapes print without supports.
- PA11 and TPU 90A absorb shocks without cracking.
- Joints and mechanisms can be printed fully assembled, with clearance between the parts.
- One-off parts and small runs are practical for robot prototypes, competitions and research.
Parts we often print
- Drone arms and frame plates
- Camera and gimbal mounts with TPU 90A dampers
- Housings for batteries, flight controllers and receivers
- Gripper fingers and bodies, including soft grippers
- Enclosures and covers for mobile and educational robots
- Pads, feet and guards in TPU 90A
- Mounts for lidar, ultrasonic sensors and depth cameras
Design tips
- Openings in a lattice structure need to be at least 8 mm and the faces need to be open, otherwise powder stays inside.
- Closed hollow sections need at least 2 powder escape holes, each at least 3.5 mm in diameter.
- For print-in-place joints in PA11 or TPU 90A, leave at least 1 mm clearance between the parts.
- Fix motors and heavy components with threaded inserts fitted into the part, instead of printed threads.
- You can make TPU 90A softer in specific areas by replacing solid material with a lattice, a method Formlabs also recommends.
The full rules are in the SLS design guide.