Vertical motion
Movement of the 3D printed plate carrier ('Zcarriage.stl') up and down by is made possible by bolting the Z-carriage to an OpenBuilds mini-V gantry which runs up and down one of the extrusions. It is controlled by a T8 leadscrew, attached to the shaft of a NEMA 17 stepper motor mounted at the bottom of the device ('motorholder.stl'). The top of the leadscrew is secured by a 608ZZ bearing at the top of the rail ('bearingholder.stl'). The use of a leadscrew ensures that the Z carriage will remain in place in the event of power failure.
Horizontal motion
Motion of the plate carrier horizontally, into the plates and away from them, is achieved with a NEMA-17 motor that moves a GT2 timing belt, running over two 606ZZ bearings. The belt is attached (beltclampA, beltclampB.stl) to a sheet of stainless steel (again painted with latex for grip). The steel sheet is attached to a second mini-V gantry which moves back and forth over a V slot extrusion mounted on top of the Z-carriage. The length of horizontal movement is determines by the position at which the second piece of the Z carriage (ZcarriageB.stl) is mounted along the extrusion.
Limit switches can be attached for both the X and Z axes to allow automatic homing.
Electronics
An affordable and readily-available solution for controlling the two axes that make up the stacker is to use a 3D printer controller, such as the RAMPS board with an Arduino Mega. These boards connect directly to the stepper motors and also have connectors for endstop switches if these are desired. Control from a computer is then achieved by sending G-code commands through the USB port. Acceleration and maximum speed can be altered to suit the sensitivity of the samples being stored.