Compliant Lab Jack

This fully 3D-printed lab jack was developed as a university project with the goal of using a compliant mechanism instead of conventional joints to achieve smooth operation with zero backlash. Despite its flexible TPU parts, it has a maximum payload similar to conventional designs and does not bend under load. Fine-tuned tolerances allow for smooth and precise height adjustments. The top surface has M4-sized mounting holes arranged in squares with side lengths 20, 40 and 60mm for attaching equipment.
 

Specs:

• Max payload: 20kg (while still adjustable)

• Min height: 46mm

• Max height: 104mm

• Travel: 58mm

• Plate width: 96mm

• Plate length: 190mm

• Mounting options: M4-sized holes with 20, 40, 60mm spacing

• Total weight: 250-300g (depending on print settings)

• No supports

Parts and Assembly
All parts are available as STL and STEP files, while some parts need to be printed more than once. The file “Lab Jack Assembly.step” contains the whole model and can be used as a reference if opened in a CAD program. Due to the asymmetric thread shape, the thread can only be inserted in one direction, which is indicated by an arrow. The compliant parts need to be attached last, together with the plates.
There is also a separate version of the compliant parts available for printing with PETG. However, it will have limited travel and maximum payload compared to the TPU version.
You only need to print one set of compliant parts — either the TPU or PETG version.
 

Print settings
The 3MF project files are grouped by filament type and contain all the parts needed with custom print settings.

For example, the seam inside the holes was adjusted to allow for smooth rotation of the thread shaft:

For the PETG version of the compliant parts, it's beneficial to print the outer perimeter first, because otherwise the surface can be uneven, which creates stress points when the parts are bent. Also make sure the seam is not at the bending points.

The model includes custom-designed supports where necessary, so no slicer-generated supports are needed:

 

Filament
PLA is recommended for the thread and rods for high stiffness, TPU (98A) for the compliant parts and PETG for all other parts.