Just when you think you’ve seen it all in the 3D printer world, something new pops up! [Nicholas Seward] posted a video of RepRap Simpson, his latest project. Simpson is a delta robot – but unlike any delta we’ve seen before. Previous offerings vertical rails on which the arms travel. As you can see, this design mounts three articulated arms directly to the base of the printer, using steel cables as part of the joint mechanism.
Judging by [Nicholas’] posts on the RepRap forums, Simpson’s grounded delta design has already gone through a few revisions. The basic geometry though, has remained the same. [Nicholas] calls this edition a “Proportional Gear Drive Joint Simpson”. The name may not roll off the tongue, but the movements are incredibly smooth, organic, and fast.
As with any delta design inverse kinematics play a huge role in the software. [Nicholas] is trying to simplify this with an optical calibration system. For the adventurous, the equations are posted on the forums, and a python Gcode preprocessor is posted on Thingiverse.
Even Simpson’s base received special attention. It’s built from a water jet cut piece of basalt. We like the use of opposed helical gears on the large joints, as well as the guitar machine heads used to tension the cable drive. One thing we are not sure of is the longevity of system – will cable stretch play an issue? Will the printed parts suffer wear from the cables? Only time will tell.