First time build - Steel Frame CNC Router

[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.

[examorph]

Dean - Cheers again for the help, good to know I can cut thru 10mm steel plate simply with an angle grinder! I haven't ordered anything yet so good spot on the motor, will get in the 6.1Nm to be on the safe side. Do you have any recommended suppliers as I dont think CNC4You do this and also, will it work fine with AM882 Drives?
I lifted up the spindle slightly but think this, like many other things might have to be one which gets put right during the build.
Attachment 17430
Do you think I am in a position now where I can start getting some of the linear motion stuff in from Fred Lee and start looking at local suppliers for the frame materials? If so, could you please cast your eye over the below list to make sure I haven't cocked anything up?

Linear Rail -
2 x Hiwin HGR20- 300mm linear rail
2 x Hiwin HGR20- 600mm linear rail
2 x Hiwin HGR20- 1000mm linear rail
12 x HGH20CAZ0C Hiwin block

Ballscrew -
1 x SFU / RM 1605-L250mm Overall length- C7 ballscrew with a ballnut with end machined and increase dimension F on end machining to 25mm for pulley
1 x SFU / RM 1610-L650mm Overall length- C7 ballscrew with a ballnut with end machined and increase dimension F on end machining to 25mm for pulley
2 x SFU / RM 1610-L1050mm Overall length- C7 ballscrew with a ballnut with end machined and increase dimension F on end machining to 25mm for pulley
4 x BK / BF 12 support for ballscrew


Some things I am not too sure about are if the reference is right for the narrower carriages, if the Z0 pre-load is what is normally gone for and also if the end machining info is right?

[Boyan Silyavski]

Hi, a bit of advice.

I see sth strange in this machine. May be i am wrong, but before buying and spending and cutting material, better do a continuity check. Element by element the way you will mount it together and check if thats possible and the difficulties.
I do that with whatever i build and in spite of that some times is difficult in real life to mount things together, there was an element in my first machine that cleared mere 1-2mm or it would not enter. Even that i have checked that 10 times .So dont use just copy paste, Hi but move the elements as they will be moved in real life.

My rule of a thumb is to leave clearance holes at least 1.5mm bigger in diameter, better 2mm. Cause the paint, the welding, etc... And when you weld, aim at precision, dont be in a rush. I have welded 1 meter machine under 1mm precision and 3 meter machine around 1mm. Its not a joke. And it was one of the first thing i welded. By the way 250A mig is best for home fabrication and costs about 350euro on ebay. Later when you can could change gun and cable with a brand one. Thats what i did.

Buy more material and use extra cut to size pieces as hard stops so you could achieve precision mounting. later you would use them for sth. And steel is cheap.

You need light preload, not 0 preload for the bearing blocks. Wider block serve nothing more than easier to mount usually for the gantry legs. On Z almost always the normal blocks are a must. Make sure you buy the long carriages.

[examorph]

Hi Boyan, thanks for the advise. I looked at the design again and the main areas I think may cause me some headache are lining up the x axis bearing supports with the gantry sides (as clearances are small) so guess there will be a lot of back and forth with the hand file for this, and another area was the ball screw bearing support depths on the x axis being difficult to line up without a mill, so I reduced these in width and made them into spacers with thru holes instead (nut/bolt onto box section), allowing me to again skim them down easily with a file if required.

Also, I noticed that I could extend the rails on the x axis all the way along the box section and reduce the length of box section to better utilize the full length of the ball screw, so the X axis rail is now 1050mm. Front hard stop was easily added with a bit of 50 x 50 box section but for the back, I used 10mm plate as anything over the back face would get in the way of the belt. Not sure if this will be enough?
Attachment 17469Attachment 17468Attachment 17470
For the carriages, should it be 'ZA' pre-load? Also how do you define the longer carriages in the part reference and what is the length of these so I can double check the models please?

[Boyan Silyavski]

Yes, ZA preload. BST Automation aliexpress, Fred if you have not figured the provider. You could use my name as reference and he will give you the right prices. Most of the people here buy the stuff from him. Alsmost always he has the best price and most importantly packs very well and stands behind if there is an error or fault

Hard stops also could be 4 big bolts or small plates welded at the sides that the plate that attaches to the ball screw hits them at end of travel. Your looks ok, just dont like the plates at the back of table, better as in front- box section.

The main mission of the hard stops /according to me/ apart of stopping the machine travel, is to stop it at that moment say just 2cm before ballnut travel ends. They must be nearly as possible square as i mount there the limit switches and they are my reference of squareness. So i use straight edge and make them truly square and weld them at the end when gantry is mounted and squared. If you understand what i mean

So i see the real beauty when the machine frame length or say distance between hard stops at the end of frame is = (desired travel) + 2cm
where travel = ball screw length - length of the gantry legs) + 2cm

So i know i have not wasted spinning mass that does nothing

[examorph]

Boyan - Thanks for the advise, I will look into the distance and confirm the 2cm as per your comments.

Are there any advantages to using the longer type carriages? Models are based on the shorter ones 'CA', and using the longer 'HA' type carriages will further reduce the cutting area.