Advice for rigidity upgrade. To profile or not?

Hi all,
Currently loving my machine but would like a smidge more cutting area so I've changed a few parts.
Here is how it currently sits. Y axis rails on 80x40 profiles which are bolted to a large 10mm thick aluminium plate.
https://live.staticflickr.com/65535/...54bf3cdc_b.jpg

I do get some vibration issues when milling. I can actually see swarf bouncing around on the aluminium base plate and the sound isn't great either.

I have a bunch of 40x40 aluminium profile i can use to make a "bed/base". How would this compare to the current build for rigidity?
Other things like steel gantry sides for bracing (to stop it tipping forward on the y axis) and steel side plates bolted to the frame to stop the y axis rails tipping inwards.
Would this help issues at all?
https://live.staticflickr.com/65535/...11dd1044_b.jpg
https://live.staticflickr.com/65535/...d27b2c26_b.jpg

Thanks
Neal

Hi Neal,

The gantry end plates and profile braces will help stiffen but not with 2mm tin sheet. You'll need 5mm plate at least.


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Originally Posted by JAZZCNC

Hi Neal,

The gantry end plates and profile braces will help stiffen but not with 2mm tin sheet. You'll need 5mm plate at least.


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Thanks Jazz. What about doubling or even tripling the 2mm plates? Bolting them all together?
Would the 40x40 profile frame be better than the single 10mm aluminium base?

Cheers

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Originally Posted by Nealieboyee

Thanks Jazz. What about doubling or even tripling the 2mm plates? Bolting them all together?
Would the 40x40 profile frame be better than the single 10mm aluminium base?

Cheers

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I would use a single piece of 5 or 6mm but if you already have the 2 mm plate then triple it up.

I would do both - the 10mm plate to act as the sub base to be tapped into for fixtures etc. then add the 40mm sections underneath ensuring they are joined to each other.. Adding another skin under the 40mm sections (even 2mm steel would be good) to make a sandwich.
But it won’t count for much unless you can tie the base to the sides. Do you need open access both ends ? Can one end be full height shear panel joining both sides and the base ? Or can the corners be triangulated at least rather than squared off as drawn.

Is this a working machine your trying to extend or just a design model your changing.?
Reason I'm asking is because you don't show ballscrews or any linear drive mechanisms for long axis.

Without knowing how this fastened/designed then not much point suggesting alternative ways to stiffen other than what you shown because more than likely clash.

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Quote:

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Originally Posted by routercnc

I would use a single piece of 5 or 6mm but if you already have the 2 mm plate then triple it up.

I would do both - the 10mm plate to act as the sub base to be tapped into for fixtures etc. then add the 40mm sections underneath ensuring they are joined to each other.. Adding another skin under the 40mm sections (even 2mm steel would be good) to make a sandwich.
But it won’t count for much unless you can tie the base to the sides. Do you need open access both ends ? Can one end be full height shear panel joining both sides and the base ? Or can the corners be triangulated at least rather than squared off as drawn.

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Thanks very much. Yes i have loads of 2mm steel plate lying around. I'd rather use that than buy new stuff. Is this what you meant by use the 10mm plate AND the profiles? I have the 10mm plate bolted to the platform created by the profiles. Front view.
https://live.staticflickr.com/65535/...fed89e3d_b.jpg

Now side view. IF I have enough profile i can lay them next to each other touching. But if not I will have to space them as in the second pic.
https://live.staticflickr.com/65535/...64cc1ea7_b.jpg
https://live.staticflickr.com/65535/...6d0312a5_b.jpg

Quote:

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Originally Posted by JAZZCNC

Is this a working machine your trying to extend or just a design model your changing.?
Reason I'm asking is because you don't show ballscrews or any linear drive mechanisms for long axis.


Without knowing how this fastened/designed then not much point suggesting alternative ways to stiffen other than what you shown because more than likely clash.

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Thanks Jazz. Yes this is actually my current machine that I want to extend a little bit, but at the same time add a bit of rigidity. Don't get me wrong, it works great and I can get some decent cuts in aluminium, but I'd like to stiffen it up where i can, using what I have laying around. I removed the linear motion components to clear the clutter in the drawing so you could see which base and profiles i was referrring to.

What you've drawn now will do the job ok and about all you can do given the design. Just use stiff braces, tin sheet isn't good enough and while layering up will help, you could also get resonance from them unless fastened well.
To be honest I'd probably prefer to use 18mm or 12mm ply wood before 2mm tin sheet.

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Quote:

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Originally Posted by JAZZCNC

What you've drawn now will do the job ok and about all you can do given the design. Just use stiff braces, tin sheet isn't good enough and while layering up will help, you could also get resonance from them unless fastened well.
To be honest I'd probably prefer to use 18mm or 12mm ply wood before 2mm tin sheet.

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How about 20mm HDPE or UHMW?

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Originally Posted by Nealieboyee

How about 20mm HDPE or UHMW?

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Yep if you have it.

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Quote:

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Originally Posted by Nealieboyee

Thanks Jazz. What about doubling or even tripling the 2mm plates? Bolting them all together?
Would the 40x40 profile frame be better than the single 10mm aluminium base?

Cheers

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It would help with the lateral rigidity, but it wouldn't be as good as a single thicker plate, as the flexing stiffness (in the flat direction) of a plate increases as something like the 3rd power of the thickness. The thing is that stacked flat plates can slide over each other therefore don't increase the stiffness so much. One thing that might work is if you glued the 2mm plates together with high strength epoxy, this would likely also help with damping a bit, but is obviously a bit of a faff to do :frown:

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Originally Posted by Voicecoil

It would help with the lateral rigidity, but it wouldn't be as good as a single thicker plate, as the flexing stiffness (in the flat direction) of a plate increases as something like the 3rd power of the thickness. The thing is that stacked flat plates can slide over each other therefore don't increase the stiffness so much. One thing that might work is if you glued the 2mm plates together with high strength epoxy, this would likely also help with damping a bit, but is obviously a bit of a faff to do :frown:

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I might have some epoxy I can use. I might be able to get a hold of some 4mm plate. Should be a lot better. Did you get my pm?

For vibration damping fill void between table plates with epoxy concrete.
Sharp sand + 10mm gravel 2to1 by volume and 10 % epoxy. Cheapest i could find was in2 epoxy from easy composites.

I have access to solid works within simulation addon.
I could run some simulations for you.