[luis.amortegui]

Hello to everyone

First of all I want to thanks everyone in this forum for all interesting and valuable information, knowledge and experience published here.

Right now i'm developing a CNC, principally for plasma and routing acrylic and other plastics, wood, foam and maybe ¿milling aluminium?
Attached there are some screenshoots of my design.

Some features are:

- Size: 1200x2000.
- Power: Two steppers of 300lb-onz in the y axis.
One stepper of 580lb-onz in the x axis.
One stepper of 300lb-onz in the z axis.
- Timing belt 1:3 (x and y axis).
- V-Bearings for x and y axis.
- Linear bearings and round shaft for z axis.
- Rack and pinon for x and y axis.
- Ball screw of 5mm pitch in z axis.
- Frame of T-slot aluminium extrusions.

Right now i have three concerns about it:
* First one is the backlash between rack and pinion, because isn't a way to adjust the center distance between them.
* Second is the sturdiness of the frame for milling aluminium. I'm preparing some models for simulating through FEA but it takes time.
* And last one is the tolerance in the guiding system (V-Bearing and track); i think i will put in each guide (4 v-bearings) two concentrical bushings and two eccentric bushings for adjusting and minimize the clearance.

I don't know if i'm being paranoic but i think that are the main concerns.

Am asking for your opinions, critics and advices related with the project.

Thanks in advance, and all opinion are welcome

Luis

PD. Excuse my english, but isn't my first language

[Arthurmetal]

Hi Luis,
I think you concerns are right:
unless your racks are perfectly parallel to the Vrail you may aspect backlash on your pineon. In my opineon you better have the pineon pressed into the rack by a spring.
Why not turn the Vrails upright? The V-bearings will be self alining and the load of the gantry handled much better by rail and bearings.
No experience here with aluminium extrusions.
Some feeling tels me your setup might be a little to light for milling.
Excuse my english, but isn't my first language either.
Arthur