CNC made aluminum angle, flat bar and square tube.
Hi, this is my first post and I'd like some input on something.
I built my fist CNC out of MDF but even with my best efforts it has "some!" deflection. Most of the pieces I make I have to give it a little extra (1 or 2 mm) to make them "fit".
So I decided to make one entirely of aluminum and keep my costs to minimum.
I try to steer away from 80/20 extrusions because of their cost, so I gave aluminum angle a shot.
I have not bought any parts yet but I designed it in solidworks.
My biggest question is in regards deflection coming from the 1/4" thick, 2" per leg angles attached to the 4" x 36" x 1/2" plate in the gantry. These will be attached with nuts and bolts (not shown in the pics).
On the second pick you can see how the SBR rails will be attached, in order to mount the the Z axis, made also of 1/2" thick aluminum.
I plan on milling mostly wood and occasionally aluminum.
Re: CNC made aluminum angle, flat bar and square tube.
It took me reading a few times to figure out where you were describing your concerns. Refer to angle as "2 x 2 x 1/4" (or however thick the legs are). Or, "2 x 3 x 3/16 angle".
Angle stock is not precise, especially the inside of the angle like you have it modeled. The outside of the angle is better and closer to 90*. I would use the outside surfaces to bolt to, if possible. To keep the current design, I suggest machining the inside leg that's bolted onto the 1/2" gantry. Even better, I would bolt 1/2 x 2 (or bigger) on the top and bottom with countersink screws before I used angle. The downside is that you'll have to drill and tap some blind holes. It looks like you'll be tapping some blind holes anyway with the end plates.
Re: CNC made aluminum angle, flat bar and square tube.
Brandon, thanks for your input.
All the aluminum angles are 1/4" thick. The ones on the gantry for the X axis are 2" per leg.
After a lot of thinking I decided to change the design once more. I figured there would be a lot of hole drilling, and that gives a lot room for things not been squared and so on.
The new design uses less material.
I am using a 3 inch C-channel to support the rails in the Y axis and eliminated the aluminum angles in the gantry. The rails of the X axis are directly attached to the 6" x 36" half inch aluminum plate of the gantry.
I also reinforced the gantry supports on the Y axis, where the linear bearings go, by putting one aluminum angle on top of the other, as well as the ballnut support.
I'm still steering away from misumi or 80/20 aluminum extrusions. Nothing against them, I actually love them, but... that's another story.
Overall I think is a better design, but there is always room for improvement.
Re: CNC made aluminum angle, flat bar and square tube.
Shrug* I hate angle...I'd replace all the angle with flat bar but that's just me. You could make the gantry more rigid by adding a brace to the back side but you could add that later if needed. Could you lower everything? Seems like everything is pretty high if you're just going to be milling sheets of wood.
Re: CNC made aluminum angle, flat bar and square tube.
Thanks, I'll make some changes and get back to you as soon as I finish.
My fist CNC was made out of recycled MDF, you know, cheap bookshelf, Ikea stuff, etc.
I've been adding several components over the last couple of months, the last ones being the 1610 ballscrews, which mate it way faster than before. I don't burn endmills any more.
In the pictures I still have the threaded rods bought in HD. Very very slow.
It works out fine for stuff that doesn't need accurate measures like signs or engraved letters or logos, but is not very precise when I need something to be as close to the CAD measurements as possible.
Here are some guitar pics I made from broken cymbals.
Re: CNC made aluminum angle, flat bar and square tube.
Here is the latest model.
I decided to do away with the angle for the Ballnut supports and go with a proper ballnut housing, they are not that expensive (Chinese on Ebay, $30 for 4).
I mounted the linear rail inside the C channel, and attached the linear bearings directly in to the gantry sides, no more angle in those.
The motors on the Y axis are mounted also to the side with 1/2 inch aluminum plate that is anchored to the C channel.
I added 2 inches to the gantry plate (x axis) to be able to use most of the rail, and the back support is made of a 2" x 6", 1/2 inch aluminum plate instead of the angle.
This design also lowers the X axis. The effective travel is 47" on Y, 28" in X and 5" on Z.
The only place I left the aluminum angle is in the motor support in the Z axis. I find it easy and convenient since I think that most of the stress in the ball screw will be in the BK/BF supports that will are bolted to the 1/2" aluminum plate.
I agree with you that the gantry will need a brace to increase rigidity, what would you recommend for it, angle, square tube, C channel ?
I think this CNC design is progressing great. Thanks for your input.
CNC made aluminum angle, flat bar and square tube.
Reply with Quote
