starting from scratch- router 1st project

[JAZZCNC]

I was not enthousiast with those spacers but this is in my opinion the only way to adjust the position of the rails afterward... Because the lower Hiwin blocks are fixed first with positon guaranteed by the machining of straight edges, I still need to be able to adjust the rails... And here is the role of the spacers.

Well that's worse than expected then because really you want referenace edges in the Front plate not just the back plate.!!

One way I use to maximise clearence with thin material and low rails etc is to not cut the referance edges into the material and sit the rails and bearings direct on the plate face.!!. . . . To give the reference edges you want for the rail and bearing alignment you then machine and press aluminum dowels into the plates half way on the reference edge you then machine these Dowels half way and flush with material to create the reference edge. This way you save machining and keep the strength of the plate plus have an accurate referance edge to work from. It's also much quicker than milling full length slots.

If you use Ground machine plate then this technique ensures you get the best accuracy from the plate because even the best milling can't match a ground surface to mount the rails on.!

Related to the reduction of the thickness of the motor holder, this is necessary due to the relative short length of the axes. Mechanicl strength will still be plenty because belt tension effort combined to pulley position is only generating low flextural torque.
However, have you some suggestions (little drawing appreciated) about how to design this part in a different way ?

Regards the Motor mounting then just offset the motor and flip.!
See the pic of Cad model for one of the little machines I build and if you want to see the real thing I can take a picture for you.! The bracket is wide and square because I put a cover over the Z axis and it fastens to this plate, to reduce weight pockets are machined in the under side along with a pocket for the Motor.