• Pivot on an axle that is fixed to the upright
• Transfer and scale movement from the motor to the hand

Each arm is made of eight linkage sections. The wooden linkage sections are milled on a CNC machine.

The strips for the linkages were cut from a piece of 2" thick hardwood. These were prepared on a table saw. The strips of wood are 1/4" thick.

The first step in milling is to fix a spoil board to the mill. The linkages will be fixed to the spoil board with screws, this photo shows the spoil board being center drilled to make holes for those screws. This is the code used to drill the holes.

The linkages are screwed to the spoilboard. The location of these holes is not critical. This steps shows the linkages being drilled.

The linkages are fixed to the spoil board using pins. A through hole has been drilled though the pin, and a screw goes through that hole and fixes the work-piece to the spoil board.

I am using LinuxCNC for my CNC controller. The motors are driven by a Gecko 540 Stepper Motor Driver. I generated the G-Code for this linkage using a Python script.

It takes 12 minutes to mill these four linkages. The machine needs a total of 16 linkages. So, making the machine requires repeating this process four times.