Concrete Slab thickness for CNC Machines

[danielm]

The place that I work for is moving into another bldg next spring. The property is already paid for so its a done deal as far as I know.

 

I just was told that the place only has a 4" slab floor and now I'm getting nervous. Our biggest machine is a 60,000lb Okuma HMC. 4" seems pretty thin to me.

[Mr. M]

Yup, I wouldn't put that on a 4" slab

[Joe788]

That seems a little thin. Having a contractor chop a hole in the floor and pour two feet on concrete isn't that expensive.

 

The machine will probably be fine if the floor is old, and you anchor it nicely. The issue will be the poor little Haas Mini-mill (or any other machine) that's sitting next to it, trying to cut a finish pass when that 60,000lb Okuma is changing pallets.

[uncle_dolan]

"Standard concrete floor slab thickness in residential construction is 4 inches. Five to six inches is recommended if the concrete will receive occasional heavy loads, such as motor homes or garbage trucks."

 

found this online on a very quick search. 4" sounds too thin to me... I think you are right to be a little concerned.

 

Brendan

[Newbeeee™]

I would definately get some soil samples taken for a machine of that weight. It also all depends upon water table level.

Worked at a place that had new floor put in, and the contractors just cut straight through the drains. So when it rained, the water had nowhere to go except to saturate the slab which lifted the very expensive epoxy floor coating (non breathable).

4" can be ok and I wouldn't have any probs putting a machine onto some 3/4 boiler plate pads (12" square). Spreads the load over area and all that.

Putting 2ft thick slabs is ok, providing the soil below the slab is ok. No good pouring onto quicksand...just means the whole slab moves.

[JerryBenoit]

I would contact a rep for that machine or a similar one and ask them? 4" as already stated is thin, I work at a shop that the fork truck broke the floor with a 4" slab.

 

Jerry

[Guest]

I would contact a rep for that machine or a similar one and ask them? 4" as already stated is thin, I work at a shop that the fork truck broke the floor with a 4" slab.

 

Jerry

 

Have we worked in the same shop perhaps

 

We put a new Mori NV5000 on the floor, the standard floor was 4", we dug out and iirc, we had poured a 12" concrete and rebar pad, it may have been closer to 18 but it's been awhile. Another place I worked, and Okuma LC-40, a solid 18 of concrete and rebar.

 

4" is NOT going to do it, it "might" hold depending what's under it but you'll chase tolerance and machine squareness ALL the time.

[GoetzInd]

We have a Makino A51 (17,200lbs) on the thin part of our floor which is coincidentally 4". We were getting a LOT of vibration compared to it being on a thicker slab. We recently had holes drilled all around the machine and low viscosity concrete injected. It helped a little but still not nearly as good as it was.

 

Mike

[danielm]

Have we worked in the same shop perhaps

 

We put a new Mori NV5000 on the floor, the standard floor was 4", we dug out and iirc, we had poured a 12" concrete and rebar pad, it may have been closer to 18 but it's been awhile. Another place I worked, and Okuma LC-40, a solid 18 of concrete and rebar.

 

4" is NOT going to do it, it "might" hold depending what's under it but you'll chase tolerance and machine squareness ALL the time.

 

 

Yep. The neys have it. A 4" slab a happy CNC machine does not make especially after reading this:

 

http://www.emastercam.com/board/index.php?showtopic=31503&st=0&p=202329&hl=+concrete%20+slab&fromsearch=1entry202329

 

 

My manager is bringing this up at a meeting with the biggies on Monday. Should be interesting.

[Guest CNC Apps Guy 1]

In one of your manuals (usually the installation manual) there should be specs for a proper floor. I'd put a Robodrill on a 4" slab and that's sbout it.

 

For a 65k# machine, you're probably lookign at 18~24" with rebar and anchors, etc...

 

 

This is the one area I see sooooooooooo many people skimp on, and of course, when the machines hav issues it's because the machine is a POS not the fact it's on a potato-chip thick floor. I see it all the time, flatness and squareness issues, machine vibrates, etc...

 

 

DO A PROPER FLOOR!!!!!!!!

 

 

 

[spade117]

4" is definitely not enough.

 

 

Another alternative would be to use a large plate that would disperse the load a little, but even that isn't a great idea.

[Guest CNC Apps Guy 1]

4" is definitely not enough.

 

 

Another alternative would be to use a large plate that would disperse the load a little, but even that isn't a great idea.

 

 

We do this at trade shows often when we're on 2nd floors. Good TEMPORARY solution.

[gcode]

You definitely need to have a foundation build for that machine.

As James said, the specs should be in the machines installation manual.

I'm guessing they'll want at least 3ft of concrete. Someone else mentioned the water table

If you've got a high water table, you'll have problems as well.

I've seen a machine sitting on a 15ft thick slab of concrete, that was really floating on the water table.

It was a big gantry mill, and a laser tracker could see it moving up and down along it's X axis as you

rapided back and forth.

 

It will cost some $$$ up front but if you don't do it, you will pay for not doing it EVERY SINGLE DAY.

 

We just put in a big VTL ( 200 hp 140" table 900K pounds)

They dug a hole 50 feet deep, lined the walls with a double row of cinderblock and poured 30 ft of concrete.

The foundations cost $80K.

The machine tool builder deemed it marginal but acceptable..

[Mr. M]

For the big Okuma horizontals it's probably a spec for a 36" slab. You could probably get away with 24" if you had that, but not 4

[Newbeeee™]

Just to be clearer after reading these...we put a leadwell 760ap on a 4" floor on boiler plate with no probs. Faster machines may move/slide so would want bolting down.

If the soil sample (ie under the slab) is good, I wouldn't hesitate to put a 40" size vertical on a 4" sat on boiler plate.

But 60000lbs requires a serious floor.

[crazy^millman]

Gcode what about the $1 million foundation for the 220' SNK at JCM? Not sure if that is the correct number since it was done before I was there, but I heard that number floated many times.

[gcode]

Gcode what about the $1 million foundation for the 220' SNK at JCM? Not sure if that is the correct number since it was done before I was there, but I heard that number floated many times.

 

 

I don't know.. the foundation was done and they were building the machine when I started.

The number I got was $8 million complete, but I don't know how much of that was foundation

[Newbeeee™]

Crazy/G

You chaps got a pic/link for that machine? What a beastie.

[GoetzInd]

You chaps got a pic/link for that machine? What a beastie.

 

http://jcmcorp.com/wp-content/uploads/2010/11/machine_4_900x600.jpg

[Newbeeee™]

WOW! I'm asuming that's a 'full size' operator in the pic

 

How do you get on with coolant / swarf flying everywhere with this style of machine?

Also, any ingress into the ways or motors (the red caps look very exposed)?

[gcode]

WOW! I'm asuming that's a 'full size' operator in the pic

 

How do you get on with coolant / swarf flying everywhere with this style of machine?

Also, any ingress into the ways or motors (the red caps look very exposed)?

 

look closely... the part is so wide only the center spindle has enough travel to machine the part..

 

and you can see there are rubber chip deflectors on both sides of the spindle.

you can also see it's still making a huge mess

[Lukasas75]

Yes, it is really to thin, just because it may break up. I recommend you to sthrenghten it by concrete floor, and you can make it using these professionals help- http://www.omnistata...rindys-835.html , just because they helped me when I had the same problem, they even can arrive and look, maybe you don't need to strenghten your floor. Good luck