New Machine Build- LVL or Steel base??

[bobmagnuson]

I though I would start a new thread for my machine build, especially since it hasn't gotten off the drawing board. Might as well start at the very beginning, right?

A little background...

The machine will be a 5x10 router, used mainly for cutting cabinet parts. I'll use Ahren's solutions for linear motion, rack mounting and gantry support. The electrical portion of the design is still up in the air.

I've come up with a couple ideas for a machine base. I've run the idea's past JoeSantos, CarveOne and Ahren, getting their feedback on both and adjusting where necessary. Now it's time to solicit opinions from a greater audience.



Option 1 - Steel base and table frame.

Base-
~6" square tubing legs
~4" square tubing cross members

Table frame -
~1 1/2" x 3" steel tube

Table frame would be bolted to base allowing for shimming if necessary.

Pros - STRONG, stiff frame. The way it should be done.
Cons - expensive ($1800), I haven't welded (learning curve), warping of the base from welding, can I keep it square?

Option 2 - LVL base

Base would be constructed of 7 1/4" x 1 3/4" LVL's with doubled up LVL's for legs. Epoxied and bolted together.

Pros - Strong, cheaper solution ($450), easier to work with.
Cons - Stiffness?

So there they are. I havn't even gotten off the drawing board and I'm presented with a dilemma. Do I go the steel route or LVL? They both appear to be good choices, however each has their draw backs.

I welcome any feedback, suggestions, etc.!

Thanks for taking a look, hopefully this will be a build to remember. Either for its success or miserable failure!

Bob

[ger21]

I prefer wood myself, as it's easier to work with. My 4x6 machine will use a wood base. But I make my own "LVL"s, from resawn 2x4's. The legs on my current machine were made this way, and are rock solid, and still dead straight after 6 years.

laminated wood is straight, stable, and heavy. All are good things for a CNC machine base. The biggest drawback, is attaching hardware to it. Bolting components to wood will usually compress the wood fibers. This can cause uneven rails, or parts to become misaligned.One solution is to bond metal mounting plates to the wood with epoxy. I'll be using linear rails on my machine, bolted to CRS steel which will be attached to the frame with screws and epoxy.

Looking at you're drawing, I'd add some stretchers in the middle of the legs or lower, and probably some angle braces as well, just to stiffen up the whole thing.

[bobmagnuson]

Thank for the input Gerry. I'll see what I can add to stiffen up the base.

I know what you mean about attaching anything to wood. I added a closeup of what I'm thinking regarding attaching the 1530 to the frame. The red bracket would be attached with screws and epoxy to the frame and the 1530 would bolt onto that. Brackets would be slotted to allow a little bit of adjustment if needed.

Bob

[dfmiller]

Bob,
Nice looking design.
I would think that a wooden approach has lots of advantages. I think Gerry's suggestion of more cross bracing is a good idea. As many triangle as possible.

The wood will dampen any vibrations. Ensuring you have adequate sections to give acceptable deflections is a must. A torsion box top will stiffen it very nicely. And of course surfacing the top will make it flat.

I wounder how inserting end grain material into the connection points would work. Of course this might be counterproductive as the wood will move differently with moisture. I guess a good sealing of the wood will minimize the moisture movement. Then gluing in dowels where ever you gong to bolt might work.


This is all conjecture on my part.
Looks great.

Dave

[bobmagnuson]

Tweaked the design a bit.

I went with a 14" lvl on the long axis. That will allow me to tie into the legs better. I also added inside and outside 'sheeting' making the legs almost like a torsion box. I think that coupled with the additional contact area that the 14" lvl provides should make this very solid.

Thoughts?

When all the seams, holes, etc. are filled with Bondo, sanded smooth and painted candy apple red, it should be smokin!

[dfmiller]

That will be slick. Are you going to leave any passages for cables etc.I like the design. It should be rock solid. I wonder what the resonant frequency of it will be?

dave

[bobmagnuson]

Dave, I hadn't thought about that, good catch. I could certainly add something, plus since it's wood, I can manipulate it quiet easily.

I would think the resonance would be quite low. The wood should absorb sound and hopefully not transmit.

[PaulRowntree]

I like the boxed in look, which should block racking parallel to the long axis. Have you added any triangulation to prevent side-to-side racking?
Is your floor area truly flat ? Would adjustable feet be useful?
Cheers!

[bobmagnuson]

Paul, my floor is pretty level, but I'll use something like a Barry Mount leveler. As for lateral movement across the short axis, I have the legs running up into the base. See the attached image. Hopefully that will be enough.

Bob

PS... And on second thought, I could use 14" LVL's on the end of the short axis as well. Bigger is always better!?!

[dfmiller]

Bob, that looks sweet. A LVL on the end will help but I think some diagonals would really stiffen up the legs.
When are you going to start since it looks like you have a workable table now?
Dave

[bobmagnuson]

Dave, I'll take a look, I'm sure I can add some additional internal bracing.

I hope to start very soon. A couple small jobs in the shop need to get done first.

I'll order the LVL's over the weekend or the beginning of next week and by the time they arrive, I should be ready to start!


Bob

[zool]

You've made a wise choice. As wood also absorbs vibration and is so dense, not much movement in the base. Two or three coats of poly will no doubt help alleviate movement due to moisture. When you attach metal to the wood, use elongated holes so the wood movement does not deform the metal. No doubt in some cases the elongated holes will be in the metal and in some cases it will be in the wood.

If I had it to do again, I would have used wood for my base, probably a combination of maple and apply ply, along with West System epoxy.