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  • Linear Rails

    I've been thinking about getting a set of the 940mm rails that Glacern sells. Anyone have any experience with this technology and can describe what ever slop might be present?

    http://www.glacern.com/sbr

  • #2
    Rails

    Dennis.

    Those linear rails are a great idea - but there has to be an effective way of keeping grit etc. off the balls and the ways. A close look at the way the "ways" are protected on grinders as well as ball-nuts etc. on milling machines etc. is a good example.

    They are a variation of the re-cycling ball drives on car steering linkages (power-assisted) as well as ball-nuts on high-precision almost-zero back-lash lead screws in precision (read CNC/NC-control) drives. Almost if not all of the drives I've mentioned have only one "re-cycling ball (nut)".

    The main problem is not only keeping the rails straight but parallel to a high degree of accuracy.

    This is addressed very well on many precision grinders - surface, T&C, cylindrical and universal. This is achieved by having one "way" as opposing "vee-s" with contained/restrained (in a "cage") precision balls balls in the vee and the "way" on the opposite side having flat faces on which either constrained/retained balls or rollers run. This achieves very high accuracy without any significant cross/lateral loading.

    Further, the axis of both the "nut" and the "rail" must be co-incident/parallel to a high order of accuracy to minimise any "twisting" tendency or loads.

    Another perhaps not noticed similar application is in the "vee-way" at the front of a lathe bed - to locate the carriage and tail-stock with respect to the lathe bed axis as well as to carry part of the load and the flat (rear) way that takes part of the load only. Locating the head-stock, carriage and tail-stock with two parallel vee-ways is more accurate but is very much more difficult - and expensive.

    But, all-in-all, those rails are very attractive as regards performance, installation and cost.

    Comment


    • #3
      In my experience the round rails just dont run as smooth at the square type. They are good for stuff like laser cutters and wood routers. But they are really cheap!

      Comment


      • #4
        What you you want them for?
        Those linear bearings with a round guide are not the stiffest ones and not very compact.

        They do come in different preloads. And if the seller doesn't tell you what preload they have nor gives more precise data like static load along the axes, dynamic load, max speed, ... they are only cheap.


        Nick

        Comment


        • #5
          Pass the parcel

          Originally posted by dp
          I've been thinking about getting a set of the 940mm rails that Glacern sells. Anyone have any experience with this technology and can describe what ever slop might be present?

          http://www.glacern.com/sbr
          Dennis.

          They are a very good concept and if used to advantage are very good value as regards reliability and accuracy.

          I am sure that Glacern can supply more technical information if required.

          This Google page may assist:
          http://www.google.com.au/#hl=en&q=li...2ddf24bc56fe27

          This may assist as well:
          http://en.wikipedia.org/wiki/Linear_bearing

          Here is Nick's response (I realise that you have (had?) him "blocked").

          Originally posted by MuellerNick
          What you you want them for?
          Those linear bearings with a round guide are not the stiffest ones and not very compact.

          They do come in different preloads. And if the seller doesn't tell you what preload they have nor gives more precise data like static load along the axes, dynamic load, max speed, ... they are only cheap.

          Nick
          Do you think I should tell him that you want those high precision rails and bearings to complete the conversion of your ("De Walt"?) docking saw to a high-precision surface grinder? Or perhaps a Tool & Cutter grinder?

          Comment


          • #6
            ... to complete the conversion of your ("De Walt"?) docking saw ...
            Did he actually write that or is that a product of your fantasy?
            One reason why I asked what he wants them for.


            Nick

            Comment


            • #7
              A bit of creativity here

              Dennis was discussing converting his docking saw to a surface grinder quite a while ago.

              I chucked in the bit about the T&C grinder - just in case.

              Comment


              • #8
                Dennis was discussing converting his docking saw to a surface grinder quite a while ago.
                Ahhh ... sorry! I forgot that he filters me.
                But after reading this, it's OK.


                Nick

                Comment


                • #9
                  Originally posted by oldtiffie
                  Dennis was discussing converting his docking saw to a surface grinder quite a while ago.

                  I chucked in the bit about the T&C grinder - just in case.
                  I actually did that and it works well. I needed to add a brace to the over arm just as is done on small mills. A problem that arose is the XY table is a bit tall, and add a magchuck to that and you begin to run out of head space. But that isn't what the rails are being considered for.

                  One thing I'm wondering about, strategically, is Glacern has reduced the prices substantially which makes me think they're either dropping the product or there is a "Newer, Bigger, Better" model in the wings.

                  Comment


                  • #10
                    Gliding

                    Dennis.

                    Why not buy a set of rails "as is" from Glacern at the current good price and at least try them for "proof of concept" purposes.

                    Those rails and balls and roller combinations are very efficient as regards low co-efficients of friction. That also have very low static/starting (stiction) friction as well as very low moving/dynamic (rolling) friction.

                    It is quite feasible to have a single recirculating-ball nut and rail (Glacern) with the "other" rail/s being a high quality ground or scraped surface and teflon pad combination too.

                    You might also consider using a "cable and capstan" axial drive if the linear movement requires to be small, cheap and low friction and cost.

                    My longitudinal drives on the table of my grinders vary. The T&C grinders have racks and pinions but my surface grinder has a cable/wire stretched between two pillars on ends of the under-side of the table. The cable is passed around a warping drum as on a crane or a ships capstan. The drum is on the same shaft as my manual driving hand-wheel. The whole longitudinal table movement is very light and smooth and is not too tedious on a long grinding job - all "handraulic".

                    Just a few thoughts to toss into the pot/mix.

                    I am glad that your surface-grinder-from-docking-saw "combo" worked OK.

                    It would be quite OK in some circumstances to use a sanding drum instead of a grinding wheel where it is finish (ie "looks") and not size or "flatness" that counts.

                    Comment


                    • #11
                      Originally posted by dp
                      I've been thinking about getting a set of the 940mm rails that Glacern sells. Anyone have any experience with this technology

                      http://www.glacern.com/sbr
                      Probably going to get Me on the ''ignore list'' but what the hay.
                      I know that bearings come in a variety of stiles, linear, axial, radial, etc.
                      But can a non linear rail actually be had .

                      Steve

                      Comment


                      • #12
                        Dennis,I have some of those rails I bought on Ebay.20mm x 1540mm blocks and rails.Same ones Glacern is selling.

                        At the time they were $150 for one rail and two blocks,so ya they are on sale.However I think the reason why is everybody and there Uncle Lo is selling them now.

                        Like said already they would fine for a router or plasma,but probably weak for anything making chips unless it was something real small along the lines of a Sherline sized machine.

                        The ones I bought I decided to use for something else than the plasma table I had intended them for.I came up with a better,cheaper rail set of my own design for that.

                        Just for an example or five-

                        http://business.shop.ebay.com/Busine...4.l1581&_pgn=3
                        Last edited by wierdscience; 09-14-2010, 11:44 PM.
                        I just need one more tool,just one!

                        Comment


                        • #13
                          Originally posted by oldtiffie
                          Dennis.

                          Those linear rails are a great idea - but there has to be an effective way of keeping grit etc. off the balls and the ways. A close look at the way the "ways" are protected on grinders as well as ball-nuts etc. on milling machines etc. is a good example.
                          Debris probably won't be an issue as this is for a laser burning table. I think some wipers would be a good idea to keep dust down.

                          The main problem is not only keeping the rails straight but parallel to a high degree of accuracy.
                          The idea so far is to use one rail for x, one for y. Even the small ones are too bulky for z, so another solution is needed. The opposite side will be a glide so parallel shouldn't be a problem but they need to be level with each other. Same as a lathe carriage.

                          But, all-in-all, those rails are very attractive as regards performance, installation and cost.
                          I think they have possibilities. I'd have sworn Sol had a video of those rails on the site but I don't see it now.

                          Comment


                          • #14
                            Originally posted by wierdscience

                            Like said already they would fine for a router or plasma,but probably weak for anything making chips unless it was something real small along the lines of a Sherline sized machine.

                            The ones I bought I decided to use for something else than the plasma table I had intended them for.I came up with a better,cheaper rail set of my own design for that.
                            Thanks, Weird - I have a real light load in mind - about what you might expect from a Dremel motor on an xy table. Not much there. I'm looking at other similar products, too.

                            Comment


                            • #15
                              Thanks Dennis for the Post.
                              That is a really good value, even without the sale.

                              Tom M.

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