Aluminum Base for XXL

Ohio Diesel still haven’t learn from there customer complaints about their method of shipping / packaging the heavy aluminum plates.

I figure, they are the only ones selling aluminum plates for the XXL and therefore know that we Shapeoko owners want a aluminum plate.

I truly hope another competitor can offer a aluminum plate for the XXL and put Ohio Diesel on the bottom of the consumer lists.

What a way to do business …

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Looking at your photo it looks like by the bolt holes, that you retained the crossbars? Is that the case? My midwest plate comes in monday so I am formulating my plan. Thanks!

Do you think the 7075ASHT500 has higher strength than the cast aluminum? Also, did they machine it for you? And what was your exact cut dimensions?

Yes I did keep them, I figured it wouldn’t hurt and may help with keeping the y axis extrusions in the right place.

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Im not totally sure on the strength aspect but I fortunately work full time in a large cnc machine shop so we machined it here! I attatched the .dxf I made up for someone else that asked for it as well.S.dxf (438.2 KB)

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I’ve been looking at the Ohio Diesel base plates for my ShapeOKO XXL as part of my upgrades toward cutting aluminum with hobby accuracy. I have noticed that a lot of people are now buying the extruded aluminum base plate (PwnCNC kit, etc). Both are expensive to me so I’m probably over-researching it. Does one have a structural/stability advantage over the other? It looks like the 1/2" plate option is easier to install.

Extruded base plates should sag and deflect a lot less than flat ones because they weigh less and have a higher second moment of inertia.

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I wouldn’t really want to rely on a single, relatively thin, flat plate of anything to maintain rigidity and positional accuracy over the size of the XXL baseboard & spoilboard. A nice chunk of aluminium as the top plate for a structure of, say, aluminium extrusion beams underneath providing the rigidity and adjustable levelling feet under that, now you’ve got a base.

On big mills the table is generally a thick steel casting with sufficient depth to provide rigidity and stability.

Since bolting down the baseboard of my XXL it’s a different machine. I deliberately included a layer of rubber as a material with a high loss-coefficient so that any vibrations that do occur get damped out quickly.

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Thanks! I should have mentioned that I plan on using the mat + torsion box combination below the metal bed and remove the 4 feet on the corners. I’ve read your thread above and several others and got a lot of valuable ideas outside of which way that I want to go for the aluminum bed material.

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Great, in that case the Aluminium sheet is moslty about a stable top surface for you to work from.

If you don’t have the ability (or a friend who works in the right place) to machine the plate flat then it might be worth considering a cast and pre-milled flat tooling plate, that’s what lots of the DIY CNC crowd seem go with as an easy way to get a reliable flat surface.

Have you checked out https://www.cnczone.com/forums/ and http://www.mycncuk.com/forums/282-Gantry-Router-Machines-Building?s=70d57618799f7f1f45dd0122ece83b86 for discussions on what people have used in home-built CNC routers?

So when I say bed, I just want to replace my stock MDF with something that will not cause me problems down the road. I currently have T-rails and waste board so I am wanting to replace all of that with an aluminum base with either threaded holes (1/2 sheet aluminum option) or T-slots (80-20 extrusion option). I would then top that with a waste board where needed or a vise when cutting aluminum. I already have all the work-holding equipment for a bench mill. From what I’m gathering, the 1/2 aluminum doesn’t seem to offer any advantage in this situation, correct? Thanks for the links! I’ve not looked closely at them for this particular question.

Aha, I think I am starting to understand…

A solid 1/2" plate would provide a very solid base. You would, of course, have to drill and tap it for your workholding but good taps make that a bearable task. I’ve just looked up the price of a 10mm tooling plate large enough for an XXL however…

There’s also the 80/20 as you say, have you looked at the extrusions designed as machine bed with built in T-slots which might be cheaper but less structural. You have a rigid box underneath so it only needs to be sufficiently rigid over the spanning distances which is much easier. The other advantage of these over the solid plate is that if you mess up, bend it by over tightening a clamp or similar it’s cheaper to fix.

From what I’ve experienced and measured so far the V wheels and belts are the primary constraint for the machine and unless you plan to go full HIWIN and ballscrew it would be hard to tell the difference between a well braced extrusion base and a solid chunk of metal.

HDPE on top for a spoilboard surface?

Thank you Liam! This is exactly the information that I was looking for.

HDPE looks like a good option. So far, I’ve just used pieces of MDF because I’ve been doing more experimentation, engraving, wood cutting so far to get my tool chains in place.
Now I’m wanting to start cutting on aluminum with the ShapeOKO so I’m upgrading parts to get there. (HDZ, torsion box base, rubber mat, replacement for the MDF base plate). As you pointed out, unless build a new machine, the ShapeOKO is a nice jack of all trades but not suitable for precision work. I enjoy modifying this thing as much as I do using it. :smile:

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Jumping in here–I’ve been trying to address sag in the middle of my XXL per some of the previous discussions on this forum.

So far, I got the rubber mat from Harbor Freight and installed that on top of my torsion box, and removed the feet from the ShapeOko itself.

I still have the stock MDF spoil board that came with the XXL, and sacrificial 3/4 in piece of MDF on top of that with threaded inserts.

The sacrificial piece is ready to be replaced–my original thought was get another piece of MDF about 32" square, 3/4 in thick, drill it for threaded inserts and run a surfacing pass over it to make sure it’s level. That’s what I did originally, but I still got sag in the center with the bed off the torsion box.

If I get a piece of HDPE–would this go on top of the original spoil board? Or do I replace the original spoil board with HDPE, and then I put the sacrificial MDF on top of that? Recommended thickness of HDPE?

I’ve found that it’s easier to consider sag / rigidity and the spoilboard material separately.

Also, it’s not just sag to worry about but pull-up and vibration during clamping and cutting, there are upward forces too. Just propping the middle of the baseboard up only addresses one of these three problems.

The way I’m looking at the machine;

Structure
Supporting the baseboard of the machine such that the key working parts are held in position WRT each other is first, to whatever level of rigidity and vibration damping you feel is required. This can be done with minimal surgery by attaching or bracing the steel straps of the machine to a base such as a torsion box.

This is literally the foundation, if this isn’t sufficiently solid and rigid you’ll just be putting band-aids on symptoms not treating causes further up the stack.

Baseboard
Then you want some layer which allows you to fix the spoilboard and workpieces in place, this is the Shapeoko baseboard. This can be MDF or there’s various extrusions that can be used. Whatever this is it needs to be strong enough to bolt to the base and resist the clamping forces you expect to apply to it as well as holding on to the threaded inserts or whatever else you plan to use for fixing.

Shapeoko uses this baseboard as part of it’s structure because it’s a free-standing machine so these boards bolt to the steel frame and mostly provide anti-racking for the steel base in the plane of the baseboard to stay square. They are not able to provide any useful rigidity in the Z axis but being MDF they have a good loss coefficient and damp vibration modes in the steel. If you’ve bolted down your steel frame you no longer need to rely on the baseboard for anti-racking or vibration damping.

Depending upon your intended use MDF may not be the material of choice for the baseboard. If you want to run coolant sprays etc. then something not MDF that can cope with water would likely be better.

Spoilboard
Finally you want a spoilboard surface whose job is to be skimmed flat periodically and allow the mounting of your workpieces or jigs. Acetal type materials let you use adhesives (I think), HDPE may be less accomodating here. Holes cut in the right places to access the clamping points in the board below etc.

Does that help at all?

Great information. As I’m considering the 80/20 extrusions for the new base material, I’m wondering if I should put extra slot nuts in the extrusions to allow me to fasten them to the torsion box from below.
Also, @Gray do you mind referencing the HF mat that people are using? I want to make sure that it is the type that I’m thinking about. I have closer places that I have bought ‘horse mats’ from for various purposes. I want to make sure that I’m using a known good solution.

Acetal (Delrin) apparently doesn’t bond well either.

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That’s a rather handy chart.

I was going on a couple of observations (including the guy with the over-oiled moustache) about double sided tape sticking to it well for machining, so not so much about permanent gluing, rather workholding.

I’ve ordered some for testing so I’ll find out for myself soon.

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It’s the Anti-Fatigue Foam Mat Set, 4 Pc., for $8.99.

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For the record, it’s page 2 of:

https://www.eplastics.com/Plastics_Material_Selection_Guide.htm

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