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

Similar Threads:

• Steel Base 3 Axis using plans from Tadas25
• New Machine Build- Steel Base 3 axis (phase 2: Construction)
• News 2014 NASCC : The Steel Conference & World Steel Bridge Symposium
• Build Thread- CRP2448 Rebuild: Welded Steel Base and Rackmount Electronics
• Granite or steel surface plate for machine base?

[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.

[Eddymeister]

Hey Fellas...
I've noticed you've idea of LVL's as a structure and briefly noticed the cons on stiffness...
I'm a chippie by trade and if you're looking for an alternative but still in the realm of timber, you could use what we call over here in Australia a Hyne Beam F17C...

LVL's are basically thick ply rip down to create a beam... A Hyne beam is laminated timber to create the beam... Essentially its solid timber stacked upon one another and glued...
The benefit of this is a huge reduction in deflection... There are engineered with a camber already within them but a cabinet maker should have a surfacer/planer that'll straightened it...
You can get them any size too... 195x65mm would probably have three times the mechanical strength of 2 150x45 LVL's together...
Just a thought..
Just a thought...

[bobmagnuson]

Materials for the base have been ordered, delivery next week which gives me time to finished up a couple other things.

Anyone have any opinion on leg levelers? I want to get them on the base while its in an inverted position. I found these on Ebay, but I don't know if they are strong enough... Item 360298814286.

And since I'm asking opinions... What about the bracket that will hold the 8020 to the base? It will be embedded into a 1/4" recess in the main beams with epoxy and screws. I'm still waiting on a few manufacturing quotes, but it appears I may have to do these myself. Steel or aluminum?

Oh and a final image of what it will hopefully look like in another month or so.

[jwolin]

Hey, love your design! If you don't already have a blog, I'm starting a website called cncmentor.com where members can create a free blog to document there progress. It's JUST getting off the ground, but it'd be cool if you added your progress to the site. EVERYTHING is Free and OPEN SOURCE. ALWAYS.

[sharbold]

Bob

Very nice design. I have most of the material setting in the shop to build a similar design using LVL and CNC router parts. Here are the feet I purchased for my table.

G7159 Machine Mount - 3" 1600 lb. Capacity

Sam

[bobmagnuson]

Thanks Sam. It was your build thread that got me thinking about the LVL route.

[sharbold]

Bob

I am currently using a ShopBot which I build back in 1999. Back then they sent plans to build the table from 2x framing lumber. Instead of using framing lumber I decided to use LVL which worked out great. On my new machine I made changes from the original to stiffen the table. I will be making a few more changes after looking at your design to incorporate some of your ideas like closing in the legs with plywood and adding the 8020 to fasten the CRS to. Business has really picked up for us which is good for the pocket book but has not left any time for working on my machine. So you will most likely have your machine up and running before I get started building.

Sam

[bobmagnuson]

While I don't have anything really accomplished yet, there is a bit of forward progress to report.

I found legs that should work very well, about $4.50 each after shipping. Not too bad. They have a 2 1/2" base, and I believe a M20x2.5 stud.

I also found a source to manufacture the brackets that will hold the 8020 extrusion to the rails along with the brackets for the legs. They will be manufactured tomorrow and I should have them early next week.

The leg bracket is just a nut welded to a 3 1/2" x 4" piece of 1/4" steel. 4 small holes to attach to the underside of the leg and a through hole under the nut for the stud to pass through.

Now if I just had something to put them on.

[ger21]

For my feet, I use hockey pucks mounted with carriage bolts. To mount them, I epoxy a long coupling nut into the bottom. Very good grip, and vibration damping too.