Vibration reduction and coolant tables...

[digits]

I am thinking about building a new coolant table for my benchtop mill - with a bit more room for something rather larger than my Super X1-L. Ideally I would like to also reduce the noise and vibration produced during milling for both my and my neighbours' sakes!

The options that spring to mind are:

A) Sit the mill on vibration reducing mounts on top of the coolant tray

B) Bolt the mill down to the table through the coolant tray and stand the table on anti-vibration mounts.

C) Bolt/Stand the mill on something heavy (e.g. concrete bricks) on top of the coolant tray and stand the table on anti-vibration mounts.

I don't really have much idea what would be best in terms of vibration damping, but I don't like B) because it perforates the coolant tray, and I really don't want to be crawling around searching for leaks under a heavily loaded table!

I know it's good practice to bolt the mill down to something heavy, but does it have to be the table itself - the table isn't that heavy at all?

Any suggestions would be most appreciated.

Cheers.

[in2steam]

Originally Posted by digits I am thinking about building a new coolant table for my benchtop mill - with a bit more room for something rather larger than my Super X1-L. Ideally I would like to also reduce the noise and vibration produced during milling for both my and my neighbours' sakes! The options that spring to mind are: A) Sit the mill on vibration reducing mounts on top of the coolant tray B) Bolt the mill down to the table through the coolant tray and stand the table on anti-vibration mounts. C) Bolt/Stand the mill on something heavy (e.g. concrete bricks) on top of the coolant tray and stand the table on anti-vibration mounts. I don't really have much idea what would be best in terms of vibration damping, but I don't like B) because it perforates the coolant tray, and I really don't want to be crawling around searching for leaks under a heavily loaded table! I know it's good practice to bolt the mill down to something heavy, but does it have to be the table itself - the table isn't that heavy at all? Any suggestions would be most appreciated. Cheers.

A heavily loaded table that is light weight sounds like most of your vibration problem right there. Damping is only as good as the surface to which you mount, IHMO if you bolt through a light duty table its still going to vibrate, if you mount pads on the table feet you may absorb most of the vibration depending upon how solid the legs and mounts for the legs. In the end you may need either a heavy table or a more rigid machine. I would/am going to on my new mill use a utlity basin tray and drill holes through it and use double studded mounts. Mind you i am reinforcing the 10 ga steel top with 2x4's under it in order to make it more rigid and heavy and putting leveling mounts on the floor.

[digits]

Thanks for replying.

My current table/enclosure is probaly about 30-40kg, and my machine is about 50kg with a vice on it. I'm guessing my next machine will be in the 100kg range.

I am unfortunately a bit limited as to the materials I can build a table with as I can't weld anywhere and my mill lives indoors on the first floor. My current table is wood/MDF, and I am trying to decide between 80/20 for ease of construction and rigidity or more wood and MDF.

I have had a look at Tormach's DIY wood/plywood table, which seems pretty sturdy even though it is a fraction of the mills 1100lbs. Do you think there would be any benefit in building something similar, but adding an array of concrete blocks just below the table surface - rather like the granite slabs in a pool table?

[in2steam]

Originally Posted by digits Thanks for replying. My current table/enclosure is probaly about 30-40kg, and my machine is about 50kg with a vice on it. I'm guessing my next machine will be in the 100kg range. I am unfortunately a bit limited as to the materials I can build a table with as I can't weld anywhere and my mill lives indoors on the first floor. My current table is wood/MDF, and I am trying to decide between 80/20 for ease of construction and rigidity or more wood and MDF. I have had a look at Tormach's DIY wood/plywood table, which seems pretty sturdy even though it is a fraction of the mills 1100lbs. Do you think there would be any benefit in building something similar, but adding an array of concrete blocks just below the table surface - rather like the granite slabs in a pool table?

Well if I remember correctly its about 2lbs to every kilo so you have a table of around 60 pounds holding a machine of a 100 or so pounds. The weight in of itself is not what you always need to look at. Rigid construction is more important than anything else. I have 80/20 and its not rigid(at joints), similiar materials can be used to make a soild table construction without doubt but 80/20 is more suited to light duty uses like enclosures(its why I have some). If you cannot weld, I would recommend using wood(4"x4" and 2"x4" douglas fir is always sturdy), if you do some studying and with a little elbow grease you can make a very nice sturdy rigid table. Ideally you would have some steel in it esp the legs and table top, becuase wood will move around alot esp with temp humidity changes. Wood will absorb alot of vibration, the problem being is in time it will loosen its joints. When I was taught how to set large machines early on they used wood cribs to keep the machines stable they then would often pour concrete base slab then motar for the final level and tucking. Loose rocks in the table will be of little value if they themselfs are not tied down or together very tightly to make one solid mass which is then tied to the machine and the floor. I built a 4x4 2x4 table earlier this year with an 1.25" MDFcore laminate table top that was used for around $25 in wood and I bought a $30 3" box of wood lag screws. It does not move when I pound on it with a hammer and chisel. You really need to make sure that were the table meets the legs there are not unsupported right angles. Use gussets at all the corners, and I would say most importantly have leveling feet capable of taking all the weight plus 100% that would provide a comfortable margin. My only draw back to my table as it sits right now is that the cement it sits on is not level and I have not put leveling feet unto it so it wobbles when weight is applied in the right spots. leveling feet will be able to compensate for floor uneveness, I use three point method most of the time, never adjusting the fourth leg after firming it up. In the end you want the table one with the machine and the table one with the floor, if its on a finished wood floor you might need to consider rubber mats or pads.
I cannot comment of hte tormach table as I have not seen one, your machine is smaller then then the ones I use and the one I hope to purchase very soon, I am preparing a steel table with steel legs, and adding pine 2"x4" underneath for support and damping. Leveling may be tough and I might have to add additional gussets to the main steel legs as they only mount at 90 degrees to the top surface, so left and right motions from the front maybe problematic. Welding in my case would be prefered but I am afraid that I cannot weld the steel legs, so I may have to bolt them on. I would surf the net and look at what other people have done for there tables.

regards
chris

[digits]

Well, I've built my new table/stand, and while it is very stiff it does actually resonate at the frequencies produced by the steppers

I have mounted my mill on some 12mm thick rubber vibration damping sheet, which does help and I've lined the underside of the table with some soundproofing sheet, but it's still a bit loud for my liking.

Does anyone have any ideas for vibration reducing mounts that will absorb lateral vibrations? I think the rubber is doing a good job of absorbing vertical vibrations, but not lateral ones.

It is quite possible that this might cease to be an issue with my new machine as it is going to use servos and weigh over 200kg/400lb, but I'd still like to have some decent vibration damping feet if possible.

Cheers.

[Pres]

Oh, Lord help you!

Some nice isolation mounts and ideas can be had from the Lord company.
Check 'em out @ http://www.lord.com/tabid/3438/Default.aspx

Pres

[digits]

Originally Posted by Pres Oh, Lord help you! Some nice isolation mounts and ideas can be had from the Lord company. Check 'em out @ http://www.lord.com/tabid/3438/Default.aspx Pres

Thanks Pres - some interesting ideas on there - basically it looks like I need to bolt my mill to a wobbly-jelly on each corner to stop the vibration being transmitted to my table. I don't really want to spend too much more on the table, so I might try hacking up some of this 1/2" rubber sheet I have.

[in2steam]

Originally Posted by digits Well, I've built my new table/stand, and while it is very stiff it does actually resonate at the frequencies produced by the steppers I have mounted my mill on some 12mm thick rubber vibration damping sheet, which does help and I've lined the underside of the table with some soundproofing sheet, but it's still a bit loud for my liking. Does anyone have any ideas for vibration reducing mounts that will absorb lateral vibrations? I think the rubber is doing a good job of absorbing vertical vibrations, but not lateral ones. It is quite possible that this might cease to be an issue with my new machine as it is going to use servos and weigh over 200kg/400lb, but I'd still like to have some decent vibration damping feet if possible. Cheers.

Are you sure you are level at the feet,
check mcmaster-carr page 1308 I cannot post a link here at work.
otherwise
wood....
preferably natural, and hard like maple or beech placed in key places like shiming under the machine.
BTW hiding the vibrations, does not get rid of them, if they are that bad you may end with bad bearings etc, if they are not already.
chris

[Stepper Monkey]

You could always pop over to the engineering forum, followed shortly of course by the inevitable covering everything you own in a two-foot thick coat of Polymer Concrete.

[digits]

Originally Posted by in2steam Are you sure you are level at the feet, check mcmaster-carr page 1308 I cannot post a link here at work. otherwise wood.... preferably natural, and hard like maple or beech placed in key places like shiming under the machine. BTW hiding the vibrations, does not get rid of them, if they are that bad you may end with bad bearings etc, if they are not already. chris

It's not on feet - which may be part of the problem. The mill is bolted to a sheet of 18mm/0.75" thick plywood, which then sits on two 0.5" strips of vibration absorbing mat and then on another chunk of plywood before resting on my table cum bass-box.

My previous table had the mill mounted on a far more wobbly pair of beams suspended over the table surface:

which I guess managed to absorb a lot of small and medium sized vibrations.

I know the key to the problem is reducing/removing the vibration in the first place - I am still playing with speeds/feeds to get smoother cuts, but a lot of the noise/vibration problem seems to be due to the steppers. They are very solidly and squarely mounted to the table, and have flexible couplers and didn't cause me any problems when the table wasn't resonant

I am beginning to think that I need to rework my table top as it is forming stagnant pools of coolant and not allowing the chips to flow to the drain, so I think I might try raising the mill off the table again. How well this will work with a 400lb mill has yet to be seen!

[digits]

Originally Posted by Stepper Monkey You could always pop over to the engineering forum, followed shortly of course by the inevitable covering everything you own in a two-foot thick coat of Polymer Concrete.

If/when I can afford a house with a garage or a garden big enough for a 20'x20' shed, I intend to build a mill table along the lines of a brick barbeque - but using breeze blocks and a 2' thick poured concrete slab with integral drain gutters for the top. This table, despite being big, heavy and expensive is just temporary, so no concrete this time!

[in2steam]

Originally Posted by digits It's not on feet - which may be part of the problem. The mill is bolted to a sheet of 18mm/0.75" thick plywood, which then sits on two 0.5" strips of vibration absorbing mat and then on another chunk of plywood before resting on my table cum bass-box. /..... I am beginning to think that I need to rework my table top as it is forming stagnant pools of coolant and not allowing the chips to flow to the drain, so I think I might try raising the mill off the table again. How well this will work with a 400lb mill has yet to be seen!

Um yeah, you need 4 distinct legs which you can level, haveing a solid base is useless, thats for starters, haveing the machine sitting on a vibration mat is just asking for problems in the long run, again you need distinct mounts. you will not be putting a 400lb mill on this setup, it least not for long.

I would with what you have, do this, take another piece of 3/4 ply(hardwood) laminate it to the other piece(glue and lag bolts would be best). After you have that, take some 1" X 1" 1/8" thick steel tubing, mount the machine to that, in turn mounting that to the plywood. Create 4 4x4 legs, and a 4x4 (you could use 2x4 but I am thinking for heavy loading)base, bolt the legs to the base, a half lap would be best, but I will assume you don't have a saw capable. Gusset the legs from the middle of the table, brace the legs to each other no less the half-way down from the top. This creates a nice shelf in the end you can use for coolant basin. The gussets and the bracing are important, if you don't do them you will be rickety. From there you can shim the legs or if you want to screw in levelers to the bottom of the legs, in my case shiming works well untill I need to move the table. Toss the vibration mat, thats not helping you any, if anything cut it into squares and put it unto the legs of the table. I don't know what ply goes for near you but its around $40 for a 4'x8' sheet here, another $20 for 4"x4" or alternative of 2"x4" bolted together, bolts are around $20. The steel is minimal since you only need about 3 feet, You can use drywall screws, I prefer lag bolts and wood glue, don't use the metal hangers for joints they don't work well its better to be directly bolted, I supose you could use nails, or threaed rod and nuts also. I used 45 mitres at the table corners, but you can butte them, again half laps or mortise and tenon are best but even I know that its not always worth the effort. This is not a 100 year table, but should suit your needs, you can cut a hole and go get some PVC drain tube for the coolant.
BTW this gives you around a 3'x6' table depending upon how you cut plywood, I assum you are much smaller.
chris