Thread: Possible New Build, altered JGRO design...

Hi everyone, I've been around these forums for some time now, following some fantastic builds and hopefully learning something, I guess we'll see over the next few months.

Many years ago I was a CNC programmer working banks of huge mills and lathes. I used to take drawings on paper, manually redraw them on the newly acquired computers and then manually write the programs required to machine the thousands of parts the company manufactured. For the last 15 years I have worked in conctruction though, after having gotten sick of the manufacturing industry.

I have taken the JGRO plans and converted most of them to metric, and I have redrawn all of the parts to suit my needs(just a couple more to do). I plan on making a CNC router around a couple of 'rules'. I will make it primarily out of MDF, and the size of the machine is heavily designed around standard sheet sizes. Ideally having a working area of around 800mm x 900mm.

The purpose of this thread is two fold:
1.) It will follow the design and build, through to completion of my machine,

and

2.) I need to use it as a basis for checking my own research.

I have researched extensively but am still NOT confident of the decisions I have made, this being said I'm hoping I may post my ideas and have the collective brain of this forum give me their thoughts?

Planned Specs below:

Footprint of machine(Approx)
1000mm(Width(Y)) x 1100mm(Length(X))
Working area(Approx)
800mm(Y) x 900mm(X)
Z Axis travel
150mm
Bearings/Rails
Leaning towards fully supported rail with split bearings along X(20mm rail and bearings) Y & Z leaning towards rails and sealed bearing blocks(20mm rails and bearings)
Linear Drive System = Ballscrews
I don't know enough to make a decision on size. I'm currently looking at a 16mm ballscrew on Ebay because the cost looks OK, not too expensive but more importntly not too cheap. I don't know enough to decide on a single ball screw on each axis, or single on Y and Z with double on X to carry the weight of the gantry without racking?
Spindle/Cutter
Makita 6.35mm trimmer, I have the 6.35mm laminate trimmer which I will try initially
Electronics/Motors
Gecko G540 stepper controller package from Homann Designs
G540 Stepper Controller Package (inc 3 x 269 oz.in Motors) [CC-03] - US$480.00 : Homann Designs!, The preferred CNC Component Supplier

I don't plan on milling any steel at all, all of my work will be in timber. Although I can't rule it out as it seems everyone who has built a machine so far has gone on to make a 2nd, 3rd, 4th machine etc: out of aluminium or similar.

I guess my biggest questions initially are rail/bearing sizes and drive screw sizes/requirements.

I know zilch about the electronics/motors but it seems so many people use the G540, that I can't go wrong???

Anyway, that's anough for the first post. I've attached a 2D image from SketchUp from a couple of weeks ago. The cutting bed actully has sides now, the sides of the machine along X are much higher and I've removed the holes you see in the ends which would have housed the rails. I have also semi finished the Z assembly but now wish to make final decisions on components before I go any further with the model.

Cheers

Gav