Cracks in garage flooring; what do you think?

[phryxis]

My buddy and I are going to be getting a CNC milling machine and putting it in my garage. I have some cracks running through the area that the machine is going to sit, and we wanted to know what you guys thought we should do about them.

Here is a picture:



and one to show where the cracks are:



The machine will be facing with its back up against the rack on the right.

any info would be great!

[lovebugjunkie]

No photo

[Geof]

What type of machine? A knee mill has a base that is very rigid and it does not matter if it is not evenly supported all the way around and the machine does not even have to be levelled. Similarly a Haas MiniMill has a very rigid base and it does not need to be levelled. Bigger machines do need a stable floor and they must be levelled to ensure that the entire machine is not distorted but it is not likely you are going to fit a big machine in that space.

[SirSmash]

If it's for aesthetics you can tile the floor or get a large mat, you can get garage sized mats to cover that. If not then I wouldn't worry about it, it's not like you'll place the CNC machine and half of it's going to fall into the earth. Pretty much all shops have cracks in the floor.

[phryxis]

thanks for your replies!

we are looking to get a CNC mill that weighs roughly 6500 pounds.

[kawazuki]

Originally Posted by phryxis thanks for your replies! we are looking to get a CNC mill that weighs roughly 6500 pounds.

Wow! 3 Tons! Spread over what sort of area of base? Here in the UK a typical garage slab of 6" thickness would be unlikely to exceed 500lbs / ft sq capacity so anything less than 13 sq ft base area might tax the slab anyway?

[Caprirs]

It will probably be fine. However, you will want to re-check for level and tram periodically in case the floor/ground settles over time. As Geof mentioned, if the machine is a full size VMC, the deflection of the base will affect how accurate the machine is.

[steveg]

phryxis Do the cracks appear to be all the way through the slab ?
If so you would be placing your machine on three different independant
floors. depending on the machines capabilities this will never be satisfactory,
it would almost never be level or square.

The best solution for a floor is to install a concrete pad per the manufacters
specification.

Having said that I have installed dozens of small to medium sized
machining centers and lathes on SOUND 6" floors with completely
satisfactory results.

[chich2]

You will find that the manufacturer of a 3 ton machine will specify a concrete slab more than half a meter deep. In saying that I run a 3.5 Ton machine on a 150mm (6") slab but I Am building a large 200mm UB 29 support frame to go under it and spread the weight. My slab is only 4 years old as well.

An engineer would tell you to get a concrete saw and cut your mill footprint into your floor. Put lots of extra cuts inside this foot print and then use a jack hammer to break it out. This would be followed by digging the hole deeper and re-poring the footing with a high MPA concrete and steel bar. A lot of work I know, but the proper way to do it.

You may find that when you move your mill into position, you will add more cracks to your floor along the way.

Good luck,
Chich

[phryxis]

thanks for the replies everyone!

Originally Posted by kawazuki Wow! 3 Tons! Spread over what sort of area of base? Here in the UK a typical garage slab of 6" thickness would be unlikely to exceed 500lbs / ft sq capacity so anything less than 13 sq ft base area might tax the slab anyway?

Ah, I see. the machine's base area is about 33 sq ft, so perhaps it could be ok.

Originally Posted by Caprirs It will probably be fine. However, you will want to re-check for level and tram periodically in case the floor/ground settles over time. As Geof mentioned, if the machine is a full size VMC, the deflection of the base will affect how accurate the machine is.

yeah, definitely afraid of the ground settling in.

Originally Posted by steveg phryxis Do the cracks appear to be all the way through the slab ? If so you would be placing your machine on three different independant floors. depending on the machines capabilities this will never be satisfactory, it would almost never be level or square. The best solution for a floor is to install a concrete pad per the manufacters specification. Having said that I have installed dozens of small to medium sized machining centers and lathes on SOUND 6" floors with completely satisfactory results.

yes, the cracks do appear to be all the way through.

Originally Posted by chich2 You will find that the manufacturer of a 3 ton machine will specify a concrete slab more than half a meter deep. In saying that I run a 3.5 Ton machine on a 150mm (6") slab but I Am building a large 200mm UB 29 support frame to go under it and spread the weight. My slab is only 4 years old as well. An engineer would tell you to get a concrete saw and cut your mill footprint into your floor. Put lots of extra cuts inside this foot print and then use a jack hammer to break it out. This would be followed by digging the hole deeper and re-poring the footing with a high MPA concrete and steel bar. A lot of work I know, but the proper way to do it. You may find that when you move your mill into position, you will add more cracks to your floor along the way. Good luck, Chich

thanks Chich, it looks like we may have to look into cutting the mill foot print and pouring the new concrete.

better do it right the first time!