table design problem

I need a table like attachment.

the table could move up and down slowly and controlled by computer. like 0.1mm or 0.2mm per step.


and there is a slide on the table, a small table on the slide, the small table could easily be moved on one direction.


Any one have cheap solution on this

how much does that cost?


the size of the table is about 1m * 1m



Thanks,

Since the slide is between the two plates, like that, then the surfaces of the two ought to be rectificated in uM (microns) range, which is either hard or impossible to do at 1m size. Just to find a company that has a surface rectification machine able to work with 1m pieces is a challenge. Havent heard of anything like that myself but something like a naval yard or companies that make ship engines could have something like that. And the middle point would have to be a support structure to keep the balls equidistant, like in high gauge bearings, and same with errors in uM range. Good luck with that. The price estimate would probably come in package with a heart attack.

What would be the reason to not have a "classic" slide system (like skates slides, linear bearings on rods, etc) on top of the first plate, and the second plate would use those instead. Lots of solutions over the net. Any particular reason as why wouldnt those work for your application.

NoobMan Wrote:
-------------------------------------------------------
> Since the slide is between the two plates, like
> that, then the surfaces of the two ought to be
> rectificated in uM (microns) range

I'm not sure what you mean by 'rectifacted'. I checked [en.wikipedia.org] but that didn't help.

Care to expand my vocabulary?

... look for "rectification" - it's meant as improvement or update ... or shave the surfaces even with microns accuracy ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Hard for me to explain, english isnt my language either. Searched youtube for some vids and here is one [www.youtube.com]
Other than that if you see more on youtube, there are some typical rectification operations done on a mill or lathe for example. In those cases it would be about the name of the operation, but not quite a machine dedicated for that.

When you mill a surface the working surfaces wont be flat, the cutting tool wont flatten it enough, even the horizontal cylindrical ones. Or when you drill a hole, same thing on the hole walls. So when something better is needed, the surfaces will to go into a machine specially designed to make a better surface, or in fact would try to, because there isnt such a thing: some errors will exist regardless.

Would be the place here to say that "probably" metal working down to hundreads or tens microns range is more specific to bearings area than to usual metal working. Check datasheet for a good bearing and see how low tolerances are like that, and actually they have to be that low because otherwise it would wear much much faster. Because bearings are moving parts. Afaik, to achieve that in bearings workings there will be a cylindrical rectification machine (or process), and these machines might get to this degree of precision, but again are circular and fairly small diameters. In extremes, machines like these (again afaik) are very costly, very heavy and mean machines, usually these will be inside a room which has the foundation that makes a common body with, foundation will be specially designed to resist and sink their vibration, including sometimes the room will be sound-proof and even will seek to break the sound of the machine itself in parts. Working in uM range is extreme business. But thats how they do it, in the big picture.

A machine to make a planar surface rectification does exist, is quite common, but usually has a small working area (not 1m anyway) and also its tolerances wont be the ones from bearings industry, but will be at least few orders of magnitude worse. Because these are used where the surfaces need to be just good, coz these are plane surfaces and usually are stationary pieces (table surfaces, guideways, points where 2 pcs have to match exactly, etc). Usually these planes are not moving parts (not working surfaces like bearings are). Hence, it wont need the precision class bearings need.

In this context you can see why i personally think that a rectification machine that has to meet these: be planar, work 1m pieces, have bearing class tolerance - this machine ought to be extremely rare, in the case it even does exist.

Thats how i view it, but you should also know that at the end of the day i dont know much either, and i have been wrong before - and in a huge number of cases.

Bottom line (imo). Dedicated bearings do exist for any job there is, and this is for more than just one reason. They bring much more than precision and reliability, its also down to maintenance. Change 4 bearings, pay 40$, and a man does it in 1 hour. Even if your table would be "do-able" ... when table slide wears out (which with the usual planar machine will happen like 100 times faster than any of classical bearing solution), what will you do then? Pay tones of extra money and wait few weeks or months for ... another set of tables?

Edited 2 time(s). Last edit at 09/28/2011 02:08PM by NoobMan.

Hmm that's about what I suspected you intended by the word, but I still didn't see a reason for it. Then I realized that we had two interpretations of the picture. I believe, and I'm sure you will correct me if I'm wrong, that you saw the large table moving up and down within the plane of the image - I do as well - and you see the small table moving left and right within the plane of the image. It follows then that the top surface of the large table and the bottom surface of the small table require a high degree of flatness, the bars a high degree of cylindricity, and all of the surface finishes need to be very fine.
However, if you interpret the motion of the small table as into and out of the plane of the image, then off the shelf linear bearings, bars, and bearing mounts should be more than sufficient.
Perhaps the original poster can clarify.

The only detail that would concern me is the moment created by the cantilever of the small table. How much load will the table see, and where will the load be positioned?

Tyro

Yup the Z movement was of no concern for me, my whole point was about those 2 tables that are supposed to slide on top of each other, in a manner of a bearing "wanna-be". That would make whole surfaces to be "working surface", together with those balls or cylinder w/e those are. "Working surface" is a term that means something happens there, friction, erosion, temperatures, etc, and thus it needs to have certain better surface properties than an ordinary surface. Otherwise the whole system will be compromised. That means all these surfaces need to be perfect like in the typical bearing surfaces class tolerances. Which again, is pretty hard to get, to say the least. And even if you do that (probably at huge expense), what happens when they get worn off, would have to pay for another set.

There are lots of ways to do things like that, like tones of solutions for example here [www.skf.com]〈=en but none of them will involve working surfaces of 1m2 area in one piece like that, i believe it wont be hard to see why.

What i think is that it cannot be feasible at any level.