I'm looking into the possibility of making a machine to aid me in circuit board assembly. I don't want to make it too complicated or I end up designing a machine that I can get off the shelf anyway or I end up reinventing the wheel and spending all of my time on the new wheel design instead of the projects I want to make with the thing.

I need to move a table in X and Y with an accuracy of 100µm (50µm would be nice but like I say I don't want to reinvent the wheel). The table will move around under a gantry that will have the part picker/placer on it that will travel in the Z. The reason I am not planning the table to move in one axis and the picker on the gantry in the other is that I want to avoid the risk of having parts fall off my picker that is pneumatic but it's an option if I can sort the picker out to be as robust as possible and if it solves a load of other problems.

200x300mm movement should be enough but given space that could be a bit bigger. I've been thinking something along the lines of a couple of those sliders with bearings in them on each axis with a stepper motor controlling them.

I don't know if what I want exists off the shelf or if I should just settle on cobbling my own together.