Ideas for really large machines

discussion of design changes / improvements / suggestions
WillAdams
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Ideas for really large machines

Post by WillAdams » Sat May 09, 2015 12:49 pm

Okay, thought we could use a thread to brainstorm for this sort of thing.

Assuming I’d want to build and had the budget for a large 48 x 96 machine, the best idea I can come up w/ for it is:

- 2 full sheets of plywood and / or MDF? w/ suitable additional material to make a torsion box (see below for thickness)
- 2 full sheets of plywood cut into sixths to be bolted at corners and sides, sandwiching the full sheet and fastening the tubular steel
- some sort of tubular steel which the torsion box would be matched to in thickness — this would make a sub-frame sandwiched by the cut up plywood and would be fastened appropriately through

Put all of that together, bolt the machine’s frame to the tubular steel sub-frame, paint / seal all the wood

I’d then have to mount that all to a wall, and would rig a counter-balance / weight system w/ pulleys for the gantry — there would be a pair of magnets at the top which would operate a clip to hold the gantry at the top when it was moved to there w/ an electromagnet setup which would disable the clip when the machine was powered up.

Anyone have any better ideas?
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Woodworker
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Re: Ideas for really large machines

Post by Woodworker » Sat May 09, 2015 1:11 pm

Build a bigger shop? It might be easier. Seriously though I rearranged my entire shop and sold several machines so I could fit a 1.8M x 1M machine. I haven't built it yet but the space is there.

Because of the weight I think there would significant issues with it overhead. To raise and lower, I would use a winch normally mounted on a truck or jeep connected to pulleys.
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WillAdams
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Re: Ideas for really large machines

Post by WillAdams » Sat May 09, 2015 2:00 pm

Sorry, wasn’t clear — I meant lift the machine up on edge and bolt the bottom of it to the wall, fastening it there, out of the way.

The pulley counter balance system would then be for the gantry, to eliminate the drag of gravity on it. The clip / magnet system at the top would be to hold the gantry out of the way when loading material.
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Improbable Construct
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Re: Ideas for really large machines

Post by Improbable Construct » Sun May 10, 2015 12:37 am

You can buy MDF in 5'x10' (actual 61"x121"). I used 2 sheets to make my 61"x61" torsion/vacuum table.
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orangezero
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Re: Ideas for really large machines

Post by orangezero » Mon May 11, 2015 7:01 pm

https://www.buildyourcnc.com/item/cnc-m ... rettyPhoto

At first I thought you were talking about something like the above link. You just mean tilting it up and out of the way when not in use?

Did you see this?
http://hackaday.com/2015/05/08/portable ... ce-saving/


I've never seen a cnc table that could be lifted straight up, using four ropes/chains at the corners. How high is your workshop? :)

What rails are you using for your linear motion?

WillAdams
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Re: Ideas for really large machines

Post by WillAdams » Mon May 11, 2015 7:25 pm

Yes, I meant something along the lines of the lean machine --- but I'd just fasten it to the wall and be done w/ it.

Missed the portable workbench. It's interesting. Surprised there isn't some opensource version. There is this: https://github.com/akaziuna/cnc-standin ... -workbench

I've been thinking about building a Milkman's Workbench....
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halfnormal
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Re: Ideas for really large machines

Post by halfnormal » Tue May 12, 2015 1:15 am

WillAdams wrote:Yes, I meant something along the lines of the lean machine --- but I'd just fasten it to the wall and be done w/ it.
I have a ReTraact-it work bench http://www.retraactit.com/index.cfm?page=167 that was bought from Sam's Club years ago. It is no longer available as far as I know. I did call the new owners of the product but they had not starting to produce it yet. (that was a few years ago.) If you look at the pictures, it is an easy design to reproduce. It is a great bench and still in use today.
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Dave
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Re: Ideas for really large machines

Post by Dave » Tue May 12, 2015 2:26 am

WillAdams wrote:Sorry, wasn’t clear — I meant lift the machine up on edge and bolt the bottom of it to the wall, fastening it there, out of the way.

The pulley counter balance system would then be for the gantry, to eliminate the drag of gravity on it. The clip / magnet system at the top would be to hold the gantry out of the way when loading material.
Wall mounting the machine with a vertical work surface sounds like a neat setup to me. 8-)

I would skip the clip/magnet system, just because it sounds fussy and there is a risk of damage if the machine moves but one of the clips is caught. In theory, if you do a good enough job with your counter-balance system, you shouldn't need the clips - just make the counter-balance fractionally stronger than gravity, so that the gantry naturally moves upward and out of the way on its own. (Or stays put after you position it there.)

You might also look into springs or elastic/bungee for the counter-balancing instead of weights and pulleys. It would accomplish the same effect (neutralizing gravity), but without *doubling* the mass of the gantry in the process. I would think that adding so much mass would mean more work for the stepper motors, as well as make things more prone to overshoot and limit your positioning speeds.

===================

All that being said, I'll propose something else. :mrgreen:

Why not just build your machine so that it is oriented 90-degrees rotated, with the gantry moving left/right instead of up/down? Then you can simply park it to one side, and not worry about gravity. The downsides are that you would have a rail on the bottom to lift your material over, and you would have to manage the dust control so that it didn't build up on that bottom rail.

WillAdams
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Re: Ideas for really large machines

Post by WillAdams » Tue May 12, 2015 2:39 am

Dave wrote:Why not just build your machine so that it is oriented 90-degrees rotated, with the gantry moving left/right instead of up/down? Then you can simply park it to one side, and not worry about gravity. The downsides are that you would have a rail on the bottom to lift your material over, and you would have to manage the dust control so that it didn't build up on that bottom rail.
Mostly because if I did that, the first time I tried to load something it would slip, hit the rails and knock the machine out of square.
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orangezero
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Re: Ideas for really large machines

Post by orangezero » Tue May 12, 2015 10:49 pm

It seems almost every example of vertical cnc machines of any size I can find have the gantry in the vertical position as well. Do you have experience working with these type of machines?

I'm just guessing, but it would seem to be just as likely to knock a hanging horizontal gantry out-of-square as your concern of a lower rail on a vertical gantry getting knocked out-of-square.

I always thought these were cool. Is there already an example of a vertical shapeoko? I don't think I've ever seen one.

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