The stoppers are one of the most complex parts of the autotester. The key part is the stopper unit.
This is printed with supports, so the first step is to remove all the supporting material.
Next, we want to add rubber stoppers to each of the tips, using the same technique with heat shrink tubing that we used on the mixer valve (see here).
Next, the 2 pieces of 281mm extruded aluminum are attached to the sides of the stoppers. M5 screws and T-nuts (or alternatives are used).
Next the stopper guide is slipped onto the extruded aluminum. The gap between the top of the stopper unit and the bottom of the guide should be about 98mm.
We will add the stopper catch plate later as part of the overall assembly.