First CNC Project, 80/20, 3 Axis. What Do You Think?

Hello everyone:

This is my first post. I've been researching CNC's for several years now, and am finally ready to build one in earnest.

I was hoping to get some feedback from you regarding my design before I take the plunge and start buying parts. I appreciate your input.

The frame will be made out of 80/20. It's dimensions will be approximately 921mm X, 771mm Y, 369mm Z. It will be held together with joining plates and M6 to M10 bolts.

I've planned to use the RM2005 ball screws provided by linearmotionberings on ebay.

The steppers are the 380 oz-in steppers with the 3/8" shaft provided by cncrouterparts' kit which includes a Gecko G540, and the power-supply.
(1) Is that enough torque?

The guideways are Hiwin's HGW25CA from solar.jean via ebay.

I haven't settled on a spindle yet. I'll probably go with the inexpensive 2.2Kw Chinese one to start off with.

I plan to build a simple PC to run LinuxCNC.

(2) I would really like to know if I will have good rigidity with the 80/20. Most of the frame is 25-2525.

(3) Furthermore, I'm using 1/4" 6105-T5 aluminum for the interface plats. Do you think this will provide enough rigidity?

I plan to use the machine for hobby projects; cutting aluminum, wood, foam and maybe some mild-steel.
(4) Do you think this machine with the 2.2Kw spindle could handle that?

What do you think readers? Am I ready to buy, or back to the drawing board?

Again, your attention is appreciated!

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Way too tall, thin, and flimsy.
And go for dual Ballscrews and steppers to drive the x axis. I've used a central screw like in your design and get wracking and have to deal with a raised table - not worth it. Your design will be more rigid without the raised table.

Steel cutting requires mass, abd can rarely be achieved with a router type machine.
Aluminum is doable if you build a rigid machine. See the cnc router parts designs, or kronos robotics.

Thanks for the info. I was worried about the hight myself. I made it so tall to possibly accommodate a 4th axis.

Hello again:

Thanks to pippin88 suggestions, I've gone back into SketchUp and rebuilt the machine. I'm more satisfied with this design. It now has two steppers and screws for the x. It relies less on custom machining, which is good for me. What's more, I've tried to make it more ridged. Removing the raised table and lowering the z-axis helped to give the machine a lower center of gravity, and I think a more solid design.

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If you honestly want to machine aluminum on this machine you are not even clost to a riding machine for that. More importantly rigidity starts from the bottom up. It is sort of like building a house, without a solid foundation it won't last. I would suggest doing some research on the Internet looking for machines that have good reputations for machining aluminum. Frankly on your first machine I wouldn't even bother with trying to achieve much on steel.

You can certainly make a viable machine out of 80/20 or similar extrusions, however when you say you want to machine aluminum you really need to think long and hard about machine stiffness. This means larger cross section extrusions and a lot of attention to how they are put together. Also even though 80/20 is nice stuff you may want to consider steel tubing or aluminum structural extrusions to moderate costs. The use of 80/20 style extrusions can become pretty expensive and frankly isn't needed everywhere in a design. In some places such as the Z axis and the Y axis saddle it might make more sense to use aluminum tooling plate. Tooling plate isn't impossible to work with in a home shop so don't dismiss it as too difficult.