[turner0908]

I'm working on my design for a new CNC wood router. I currently have a small wood router cnc I built last year, but it's a different design and I'd like to build something better. I've pretty much bought all the mechanical and electrical parts already, but I have not started cutting or building anything yet. I'm looking for advice on my design. Here's the general design sense:

- I wanted to have at least a 24" x 48" working area.
- I'd like to have around 6" of Z clearance and I want to have an optional rotary axis eventually
- Will be mostly for cutting wood for a side business we have. If I can cut aluminum that's a bonus.
- Trying to work within a reasonable budget - need to use some cheaper materials such as MDF instead of making it all metal.

For the X-Axis, I have (4) SBR 15-1500mm linear rails and (2) SFU1605-1500mm ballscrews
https://www.ebay.com/itm/SBR-15-1500...72.m2749.l2649
https://www.ebay.com/itm/Ball-Screw-...72.m2749.l2649

For the Y-Axis, I have (2) HGR20-900mm linear rails and (1) RM1605-900mm ballscrew
https://www.ebay.com/itm/2X-Linear-R...72.m2749.l2649

For the Z-Axis, I have (2) MGN12-400mm linear rails and (1) RM1605-300mm ballscrew
https://www.ebay.com/itm/ZYLtech-MGN...72.m2749.l2649
https://www.ebay.com/itm/ZYLtech-Pre...72.m2749.l2649

I also have some 25x50mm aluminum extrusions to work with (5 pieces that are 1000mm or so in length)
For my motors, I have (5) NEMA 23 2.8A 269oz.in stepper motors and TB6600 drivers
This is my spindle https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I have an Arduino Mega2560 R3 + RAMPS 1.6 board for controls
I have bolts/screws for hardware and 12VDC & 24VDC power supplies, wire, limit switches, terminal blocks, etc for all my wiring and controls
I plan to use 3/4" MDF for the main structure and bed. I plan to use the aluminum extrusions I have for the Y axis horizontals.




My main concern in the Y axis vertical gantry plates. I can't afford thick aluminum plates, so I'm hoping to use 3/4" MDF and keep it stiff by having the dual rails on both sides of the X axis and using aluminum extrusions for the Y horizontals.
Can anyone evaluate my design and let me know what you think? I've attached a picture, but I can also upload a Fusion 360 design file if that helps.

[ger21]

3/4" sides will always flex.
If you want to make them stiffer, you could laminate 3 pieces of 1/4" MDF together, or two pieces of 1/2".

[peteeng]

Hi Turner - 2x3/4" = 1.5" thick columns would be the go. Can be tailored around the top with pockets but the bearing area and middle definitely need to be thick. Plywood is twice as stiff (or more) as MDF but twice the cost. Maybe better to use ply? eg formply is stiff and you don't have to paint it at the end? Only seal the edges...Peter

[routalot]

Any reason why you couldn't trim the MDF flush with the back face of the extrusion on the gantry,allow the extrusion to extend as far as the stepper protrudes and then bolt an MDF web to the back face?It could be fixed to the side plate of the gantry by a piece of angle or a wooden batten and glue.

[peteeng]

Hi Turner and use aluminium angles for the extrusions? Need more support at the extrusion to timber connection. Probably don't need 4 cars and two rails each side as well. The square cars are quite stiff. You need heavy preload cars if possible. Std preload is not enough.... More bracing between the top and bottom gantry beam or try to use one large beam....

I always wonder how to get the rails parallel when they are mounted on the sides? Do you commit one side so its a master then wiggle the other side, then screw it together? Peter

[turner0908]

Hi all, thank you for your input - it's appreciated!

- I ended up buying 3/4 birch plywood. For the vertical, I think I'll keep it 3/4 thick but add webbing or angle to the side to stiffen it up. Routalot, your idea is pretty good, I'll see how that might work out.
- I will also add more bracing on the Y axis gantry beam.
- I already bought the rails for the X axis so I have enough rails to keep 4 cars and 2 rails on each side. Is that a waste? I was just worried 1 wouldn't be enough for each side.

[ger21]

- I already bought the rails for the X axis so I have enough rails to keep 4 cars and 2 rails on each side. Is that a waste? I was just worried 1 wouldn't be enough for each side.

If they aren't aligned perfectly, they can bind.

[pippin88]

2 rails on each side is a waste.

The load rating on these things is much more than your machine will generate or tolerate without falling apart.

[routalot]

Isn't it curious how many builders seek great rigidity along the machine and then neglect to consider that the end plates will be subject to similar loads when cutting across the table?It would be a strange design that had significantly weaker steppers on one axis and would make cutting circles an interesting experience.So often we see gantry end plates that are 3/8" aluminium and dual slender extrusions joining them and then we get to the topic that always makes me smile-a very long Z axis travel.This project doesn't have that as a desired feature but so many people fail to take into account the leverage imposed by a high gantry or the limited access into a corner with the Z operating close to the table.I just wish more prospective builders would read peteeng's thread about his new design and the level of engineering behind it.