First time build - Steel Frame CNC Router

[DigiSoft]

You can check out my thread I am almost finished with my machine.
It is 90% steel

http://www.mycncuk.com/threads/5237-...LD-please-help

[examorph]

Dean - Thanks for clearing things up for me, I will be doing some aluminium work on it but was going to go down the route of using a mist rather than flood cooling, will this still be OK with the ply wood sealed base and spoil board setup? Also, probably a silly question but what are the typical depths for the ply wood base and spoil board? Just checking as I want to make sure I leave enough space bellow the spindle.

DigiSoft - Thanks for the link, I remember seeing it previously. Really nice buildd!

[JAZZCNC]

Provided you seal very well then yes with Low qty mist then yes Ply will be fine. Problem then comes from your Spoil board. Even Low volume Mist still creates mositure which gets into spoil board which isn't sealed. Often MDF is used for spoil board because it's cheap.

Really if your planning on using any wet kind lube often, even with air, then you'll want something that's resonably stable.

Depths are usually a multiple of sheet sizes so 18 or 25mm etc.

[cropwell]

I had a resin impregnated board on the floor of my trailer. It seemed indestructible. I was wondering if that would make a good base as it is waterproof.

[routercnc]

Going back to your sketch in post#19, I would extend the side pieces forward so it matches up along the whole side of the X bearing plate. You can then pickup another bolting point on the front X bearing between the 4off vertical bolts for the X bearing.

This side piece extension would be triangular in shape and fill in from the top of the gantry down to the end of the X bearing plate.

It would then (optionally) be triangular back out to the ballnut mounting point, or just go straight back.

This would provide much more support for the gantry onto the bearings for not much effort (apart from a bit more material).

[examorph]

Dean - Cheers for the advise. I swapped over the carriages for the narrower ones on the x axis and drew up the frame as per the setup you recommended using 4mm external rads on the section. Only thing I added was the box section running along the back (between the two x rail support sections) to let me mount a bearing for the belt onto (same as yours on post #7 here).

Routercnc - Thanks for the great idea, I updated the design with the following adjustments:

• Extending the plate 20mm short of the full bearing plate to keep standard sizes (200mm width x 300 height)
• Instead of being triangular back to the ball mount, I made rectangular cutouts on each side as any other way caused it to clash with the aluminium x axis ball-screw bearing supports and as a result, reduce working area.

I am going to try get access to a mill for this, but if all else fails are there any other options for cutting the steel plates?

Attachment 17424Attachment 17426Attachment 17425Attachment 17427
Gantry weight (just side plates and box section) is coming out at roughly 17.5kg @3mm wall thickness. When put together with Z axis, spindle and motors, will this handle OK with the one 3.1Nm motor on the x Axis?

Also, I checked the z extension using the 25mm tall bed/spoil board and the below image shows the spindle end going slightly into the bed at full extension. Would it be worth changing the 100 x 50 box section under the x axis rails to 120 x 50 or maybe higher?

Attachment 17428

[JAZZCNC]

I am going to try get access to a mill for this, but if all else fails are there any other options for cutting the steel plates?

Yes easy done without Mill. Print templates stick on steel with spray mount then get some 1mm Cutting discs for grinder which will slice thru that plate like Hot knife thru butter. Follow the lines and away you go will take about 20min per side.

Gantry weight (just side plates and box section) is coming out at roughly 17.5kg @3mm wall thickness. When put together with Z axis, spindle and motors, will this handle OK with the one 3.1Nm motor on the x Axis?

No you'll need either a ratio to increase torque or larger motor. I'd suggest 6.1Nm Nema 34 for X axis and run the whole machine with 65-70V.
Now here's the beauty of this system if you have one already and want to try using Nema 23 3.1nm motor then it's not going to cost you a fortune if doesn't work.
Use nema 23 motor with 1.5:1 Ratio (if using 10mm pitch screws) to increase torque and if it doesn't work then just replace motor with 34 and bore the pulleys to fit new shaft size which will be same or larger than 23. Depending on how you make the motor mount then you may need to alter or change this also.
68Vdc is at the bottom end you'd run nema34 motor and top end for nema 23 so will still give you decent performance so very little risk or cost involved.

Also, I checked the z extension using the 25mm tall bed/spoil board and the below image shows the spindle end going slightly into the bed at full extension. Would it be worth changing the 100 x 50 box section under the x axis rails to 120 x 50 or maybe higher?

How deep.? But in any case I'd lift the Spindle mount up slightly because it's a little low, You only need the Spindle Collet nut sticking slightly below the bottom plate. The slightly higher spindle mount doesn't hurt stabilty and offers some flexabilty if you need to slide the spindle up or down. Which you some times may want to do if using tall material.
I wouldn't sacrifice Strength having too large an extension or hieght for the few times you'll probably need full extension.