Putting urethane under Mini Mill 2 leveling feet

We are going to be moving out new Mini Mill 2 into place this weekend. Dad wants to put 3/4" urethane pads under 1" thick 12x12 steel plates under all 4 feet.

It's our first cnc machine, and this is something I've not heard of before. We will have a 2004 tm1 next to it running second ops, he thought it would help damped vibrations in the slab.

Do the machines want to "dance" if set up this way?

Good idea? Terrible idea? Meh?

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Do a internet search using the phrase " rubber bearings building" or "rubber bearings bridge".

A thick rubber pad will have compliance in both the vertical direction and shear. The vertical spring constant is determined by the thickness/length ratio of the rubber pad. Rubber bearings designed to be stiff vertically and flexible in shear. are made using a number of thin layers of rubber and steel plates. This is the design used for bridge and building foundations.

sirAIG said:

We are going to be moving out new Mini Mill 2 into place this weekend. Dad wants to put 3/4" urethane pads under 1" thick 12x12 steel plates under all 4 feet.

It's our first cnc machine, and this is something I've not heard of before. We will have a 2004 tm1 next to it running second ops, he thought it would help damped vibrations in the slab.

Do the machines want to "dance" if set up this way?

Good idea? Terrible idea? Meh?

Sent from my SM-G955U using Tapatalk

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Unnecessary and would most likely make leveling a pain.

I could be off but I was under the impression the whole idea was to transfer vibration out of the machine. Hence why large rotating equipment often has concrete pillars all the way down to bedrock.

No rubber............you will likely see more vibration..................not in the floor, but in the machine.

I have done something similar when installing a small Haas mill in a university setting where delicate instruments (S-T microscopes, etc.) were also in use.

In this case, I designed a large single-piece steel plate with welded-in stiffening ribs to go under the mounting feet, with Sorbothane isolating pads under the plate and resting on the concrete floor of the building (not at ground level).

The large plate was to mimic a proper concrete foundation, but without the height and weight that would have added. As one piece, with broad support points for the Sorbothane, we had reasonable ability to level the machine, without significant rocking when in use. Using four smaller, independent plates can allow isolation, but not proper support for the machine itself.

With properly chosen elastomers for the pads, you will get less vibration transferred to the floor, but to do this right you really need to "map" the vibration profile of the mill in use, then chose the elastomers and sizes/placement to match for the right "vibration to heat" performance. Too stiff gives you little vibration attenuation, too soft and it's a wallowy mess.

I have placed bridgeport mills on one inch thick, 8" square pads and liked the results. You could sense movement of the whole machine but was quiet and smooth operating.

I have operated and maintained Mini Mills and their construction is solid in that they do not seem to be affected by exact leveling as say a VF2. I would be concerned about feet sliding on the plate though, rapid axis movements can have a fair amount of inertia.

If it's a new under warranty machine your just giving an excuse for the claim of "improper installation".

All in all I would say not necessary, no advantage rather than simply bad idea. But I would enjoy being wrong.

Dunno about what should go where. Isolate or transfer vibration, but these guys are in that business:


Vibration isolation pads - AirLoc - for machine installation

Step one is going to be determining the weight at each support leg. Step two is choosing a product that meets your isolation goal (frequency and amplitude mostly) at the given weight. Secondarily, excursion needs to be evaluated.

Mason Industries springs to mind, as does Peabody Kinetics. They're both all about noise and vibration control, but that's a two-way street.

When I started work at my college, all of the machines were glued to the floor with a product I think was called "Unisorb". The boss thought it was a great idea. I think it would have been maybe for a washing machine or drill press, but in practice the stuff was a pain. It flattened out and made leveling difficult. We have since got rid of it and the machines sit on steel or cast iron pucks.

It's a Mini Mill.............there's no reason whatsoever to place it on urethane. I don't think there's MTB out there that would suggest placing a VMC on rubber pads..................Every shake and shimmy from cutting and rapid moves will be amplified..............................and 1"x12"x12" plates under each leg? Little over kill eh? Are the floors dirt?

david n said:

It's a Mini Mill.............there's no reason whatsoever to place it on urethane. I don't think there's MTB out there that would suggest placing a VMC on rubber pads..................Every shake and shimmy from cutting and rapid moves will be amplified..............................and 1"x12"x12" plates under each leg? Little over kill eh? Are the floors dirt?

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No, there are times you have to do this. As I said in #6, I had to deal with other groups that were concerned about vibrations interfering with their work. So, whether "needed" or not, we went through the analysis and remediation to minimize additional noise/vibration from the new machine tool.

Sometimes it helps to realize that just because you've never had to deal with a situation doesn't mean that nobody ever has to...

david n said:

............................and 1"x12"x12" plates under each leg? Little over kill eh? Are the floors dirt?

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Lol that's what I was thinking. In my opinion your wasting time and money for nothing. Drop that little machine on the supplied levelling feet and go.