Binding under gantry blocks

Kyle, thank you for the recommendations. Looks like I have my work cut out over the weekend. So sorry about your finger injury. Very scary, I will be very careful and keep that in mind. Just priced the plywood at HD, this is their premium board.

JENN

It’s okay Nick, join in the fun! I have my work cut out for this weekend. Gonna switch out the MDF for Plywood, and raise my blocks a quarter inch.

JENN

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You may be able to just get away with clamping a piece of angle iron on both sides to add rigidity to the mdf.

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And it’s likely cheaper than plywood at the moment too!

if you have a lumber yard you could switch your top to marine grade Baltic Birch. that is what I used for my Fisher folding table.

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I think doo-hickies is not going to work for me, I’m afraid of just adding more band aids and have issues resurface down the line. I’ve also made a heck of a mess with oil all over. I’m gonna go with the plywood and laminate the top with a 4 x 8 Plas-Tex panel.

Thanks guys!

JENN

MDO plywood is exterior grade and will resist the oil :slight_smile:

Hi Jenn,

you did not mention what kind of construction you have under the table top.

If it is sturdy and rigid, and first of all also large enough to support all the surface and even the corners, then the requirements for the tabletop rigidity becomes of lesser importance.

On the other hand, if your table base is smaller than the desired tabletop, and you have overhang, it depends on how much overhang you have.

One cannot say something about what tabletop to use without knowing on what table base it shall be mounted.

My preference if I had a small table base and would want to put a tabletop on it that is larger than is the table base, which would mean overhang, then my preference would be to build a torsion box of a few inches height in the same size of the tabletop. The material is not of primary importance then, neither for the components of the torsion box, nor for the tabletop.

Plywood may be a good choice, however the thickness depends on the questions above, which I don’t find answered. Just switching to plywood for the tabletop may not necessarily resolve your problem. At a certain overhang, every material will be dragged down.

What you need is rigidity. You may increase thickness, or use a more rigid material, but a torsion box is much more effective in producing rigidity than increasing the thickness of your tabletop. Or than exchanging the material.

You may well build an entire table using MDF, as long it is rigid by design as a whole. See torsion box.

Thanks,

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Or attached to the wall, carve a Mona Lisa in 3D on it.

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I can’t stress enough that any surface, plywood or MDF, needs to be fully supported clear to it’s edge or at least under the four points of load. As others have indicated, any overhang has a potential for distorsion or ‘potatoe chipping’ as Kyle described.

My torsion box table, being constructed soley of plywood that is glued & pocket screwed internally, has shown no movement at all yet. I say “yet” because it is fairly young at about 6 months so far.

Even if it is not practicle to reconstruct the top with column supports you might add about a 4" high vertical plywood frame under the perimeter edges. It is suprising how stiff adding that kind of web makes even fairly thin materials (thus the concept of the torsion box).

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Yes, just have to look at bones, how they are constructed, seen under microscope: Not massive at all, but full of torsion boxes.

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Hi Aiph5u,

You guys have produced mounds of high level advice. I really appreciate every ounce poured in. As for my current setup, well I do have an overhang. Which most likely is why the binding crept in. I am going all out this weekend and I am disassembling my 1F, and starting from the ground up. I have made a list of supplies, 2 x 4, 2 x 6, Plywood, Nuts Bolts, Plas-Tex and so much more. I will be building immediate support directly under the CNC Footers or blocks and addressing all those concerns mentioned.

Thank you so much guys!

JENN

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+1 for using a torsion box construction, I have a 4x8 assembly table and a 4x5 outfeed table that are built this way out of plywood and after 10 years they’re still dead flat

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I have built my table using an MDF top. I don’t have any overhangs but the table is in a shed that is not climate controlled and I live in humid Virginia. I’m getting my machine this weekend and I’m wondering if it would be better for me to just take the MDF top off and replace it with 3/4 in Birch or Maple plywood. What do you think? If plywood is going to be better can I just put it over top of my MDF table top or should I replace the tabletop altogether?

Hi Matt,

I don’t think at all you need to replace it just because of an average of 70% RH, and practically not varying over the year. It’s more if you spill your coffee over MDF or if you place your table in a wet environment or if your MDF is in touch with a humid wall. The point is if your construction is rigid by design and surface is well supported everywhere, then material is of lesser importance. Good luck!

Thanks,

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I built the table that Bruce Ulrich designed (DIY CNC Table Build - FREE Plans! - YouTube), but I’m not sure if the support underneath is really going to be sufficient over time. I also think I may run into the same problem of expanding once you’ve cleaned the rails. So I’m definitely going to raise up the feet 1/4 inch to avoid that.

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Hi Matt,

I had a look at the link, it seems to be a suitable table for the Onefinity cnc.
I would prefer to add diagonals on the legs to add rigidity to the table base, but regarding the tabletop, the MDF board is supported both in the surface as well on the corners. I doubt that there would be sagged areas like on Jenn’s table. If in doubt, you could simply add few more cross pieces or smaller pieces between the cross pieces. You could also add a long transversal or two long diagonal pieces underneath the cross pieces, from short side to short side or from corner to corner, to add stiffiness in the middle of the table. Just in doubt.

What do you mean with “once you’ve cleaned the rails”?

Sorry, I think I said the wrong thing. I meant lubricate the ball screws. I believe that’s part of the regular maintenance. But I don’t even have the machine yet, so this is all new to me and I’m learning. Thanks for taking a look at the link and providing suggestions.

Ah, ok.

I don’t think that a drop of oil would do much harm to the MDF. If you built your table already, I would use it with the MDF tabletop. Did you implement the double wasteboard system where the bottom has threads and the top has through holes?

Hi Jenn did the MDF swell up any from the oil? :man_shrugging:

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