Vertical based cnc plasma comments and suggestions?

[Oracle_9]

Hi,

I am planning to make a cnc plasma cutter. I already have the hypertherm 100.

For now, I am looking at the mechanics firstly.

Due to my limited ground floor space, I am considering making the CNC vertical based, rather than traditional horizontally based.

I am planning to use squar steel tubing for the framework and gantry.

Either 4ft high x 8ft long or 8ft high x 4ft long.
There would be a lightweight grantry style setup.
The part will be clamped onto a vertical base of some sort.

I think the machine would travel easier in the left-right direction, but up and down I think there would be some problems, due to it carry the load of the gantry. But maybe a simple counter weight may remedy this, or maybe not needed at all.

Concerning plasma cutting, well, it would situate the cutting path so that the start and finish of the cutting will happen on the "top" of the part so that it will hold the part in place, as if its hanging, and then it drops to the ground.
This would be for smaller parts and thin sheets. I guess for larger, and thicker parts, they would be oriented more towards the bottom.

Anyway, I am interested in peoples views and comments of vertically based CNC. And any tips or recommendations to watch out for. Thanks.

Also, any comments of what torque steppers is recommended for this applications? I will belt train reduce it.

[BobWarfield]

Fascinating project!

I do think you run the risk of not getting the cuts in the right order and the part falling to the ground prematurely. However, this is a matter of your programming and under your control. It's just an additional complication to using the tool. I'm also not sure whether the plasma cutter behaves any differently with regard to the quality of cut or what happens to the dross in a vertical situation. I'd experiment with that by hand before investing in building a table.

With all that said, I think the main issue is that gravity no longer works in your favor. This is going to impact how the gantry and other parts flex, what sort of railing system everything rides on, and so forth. Personally, I'd go with surplus THK rails from eBay if you want to build this way as I think that cleans up the flexure issues surrounding the railing system itself.

I would also consider a slight lean, rather than making it perfectly straight up and down vertical. I would run the gantry up and down rather than left to right as I think that gets you a better geometry regarding flexure and so forth. Also better if you want to make things 4' x 8' with the long dimension horizontally.

I don't know that you need to counterweight. The gantry shouldn't be that terribly heavy, you can run a little stronger step motors, and if it rolls left to right the heavy part doesn't go "up hill".

I'll be interested to watch this one unfold.

Best,

BW

[Oracle_9]

Thank you for the comments. I havent thought about how the plasma behaves and the quality of the cut metal when done in this direction. I will have to experiment with this in the comming weeks.

I was thinking of about 10 degrees for the tilt. So there is some little clearance for when the parts would drop down.

I have to look at some prices for the linear rails. Originally I was thinking of using the "grinded shaft" material, like 1.25" or 1.5" diameter. But maybe the rails would be cheaper, I have to do some looking into this.

I should mention, that I am probably will use the rack and pinion (spring forced) method of propulsion, since the prices for ballscrews for this application is too expensive.

I've been looking around, and maybe 1200oz/in for moving the larger mass; the gantry assembly, and 400oz/in for the moving of the torch head.

I agree that there will be an issue of flexing, but where and when is the question.

If all else fails, I would go for the more traditional horizontal flat bed method.

[Apples]

I use 2 1200oz steppers for the long axis and 1 270oz for the short axis and the z axis. My gantry weighs about 100lbs.

Peter
Australia

[energyforce]

240lb gantry, 1000ipms, 1 450ozin (approx) servo. Horizontal gantry though. If it was vertical, my gawd i need something probably 10 times larger at 240lbs!! (shudders)

Its all about the reduction. Make sure you get the right amount of reduction and a good inertia ratio.

[diarmaid]

Unfortunately I dont have any advice to contribute, but this sounds really interesting. Please keep us updated. Pictures of plans and/or the build would be great to see. Good luck with it!

[Oracle_9]

There is a third option which might be a compromise between vertical and horizontal. I remember sometime reading that someone here posted a build log of some sorts of having the framework and misc, build/bolted vertically onto the wall. But it has only an arm type gantry stick out horizontally, thus functionally like a horizontal and freeing up ground floor when not in use. And I think the wood or something was temporary laying on the ground when in use. I dont remember where his log is, but I think it was a router of some sorts. Anyway, it was neat, and thats was partly my inspiration, which I still remember.