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    I have to make a wheel for an encoder. The wheel will count distance on sheets of steel. I was thinking an aluminum wheel with a rubber coating on the outside. I am just not sure what rubber i should use and how i should mount it. Any ideas ?

    Rob

  • #2
    Hot steel, cold steel, oily steel,wet steel, big pieces, little pieces? With ALL THE DETAILED INFORMATION provided, I would pick Grandma's old faithful. neoprene. Want to get fancy try silicone or nitrile.
    By the way, how long is a piece of string?
    Duffy, Gatineau, Quebec

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    • #3
      How about an o-ring fitted into a groove? Or several o-rings side by side if you need width. A stretch fit and maybe a bit of super glue to make sure it doesn't slip.

      You can also buy o-ring material and make your own lengths up using super glue.

      Urethane is a good alternative to rubber when it comes to getting tyres made, a range of hardnesses available. A lot more expensive and difficult than an o-ring though!

      Edit: I was referring to getting urethane tyres cast, but now I recall we used urethane cord to make tyres also, you can buy this cord in a range of diameters (larger than o ring material, e.g. 6mm, 8mm, 10mm and up), but you need to hot melt join it. It requires a special tool to do it properly, and it is difficult to get the join absolutely smooth. Suppliers usually make to order. As used for light driving bands etc.
      Last edited by Peter S; 06-06-2010, 09:58 AM.

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      • #4
        more info for Duffy.

        Well i gave you pretty much what i have. I do know it is a steel froming company. They convert sheets of steel into steel studs, in some machines, in others they do other stuff. Oil is used to lubircate the forming tools, but i was not told if the encoder is going on the in or the out of the machine.

        How would you mount the neoprene?



        Peter S

        Cool idea. I did not think of that. I would be concerned that the o-rings would slip but i have used some glues, especially that o-ring glue, that really bonds. I like that idea. The customer could change them easily if they break.

        Rob

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        • #5
          My first impulse would be to use a commercial encoder from BEI or similar. That makes life MUCH easier for the poor schlep who has to repair the machine ten years down the road.

          Second to that I'd, make the disk out of black delrin.

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          • #6
            I would think a commercial wheel built to known dimensions (to ensure a source of replacement parts) would be a good idea. Skateboard wheels come to mind as a family of readily available wheel. You may require a larger scale but those are also available. Once you have a replaceble wheel of known specifications you need only adapt your encoder to the wheel.

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            • #7
              You would think the motor moving the sheets of steel for the steel studs would be the most likely candidate to receive the encoder wheel - and for that there is a wealth of ready made / off the shelf encoder wheels ready for your application

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              • #8
                Trouble with using a wheel of whatever diameter is what tolerance on length is acceptable for wear on whatever facing due to friction??Would have thought that an adjustable length stop was more acceptable.

                Regards Ian.
                Last edited by Circlip; 06-06-2010, 02:31 PM.
                You might not like what I say,but that doesn't mean I'm wrong.

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                • #9
                  What's to be the diameter of the wheel- Maybe convert a hockey puck. That's some pretty hard rubber. Should wear well.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                  • #10
                    Encoding

                    Wear and slippage are problems here.

                    A 1mm error in diameter will be 1 x pi = 1 x 3.1416 = 3.1416mm in circumference and linear travel.

                    The smaller the wheel diameter the larger the number of turns of the wheel in a given length.

                    There is no allowance/s for wear and slippage.

                    Inertia may need to be considered as well.

                    The tolerance to length needs to be considered.

                    If the "studs" mentioned are wall studs, I'd guess that cropped/finish length tolerance/limits will be pretty tight as regards length per any individual pieces and for a whole batch. I'd imagine that a 10 foot stud would need to be in the order of 120 +/- 0.005" = 119.995/120.005".

                    As I understand it, an encoder will only measure angular step-to-step and this will be translated into the linear equivalent so the linear tolerance zone will need to be allowed for in the roller/wheel sizing and tolerancing and encoder step angular displacement.

                    I'd imagine that there will be some guaging and limit stops for setting and stopping as well.

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                    • #11
                      Originally posted by spkrman15
                      Well i gave you pretty much what i have. They convert sheets of steel into steel studs, in some machines, in others they do other stuff. i was not told if the encoder is going on the in or the out of the machine.
                      Rob
                      On the converting of sheet to studs, is the material coming off a coil and being cut to length or is it actually sheet steel?
                      The other question I have is, is the forming process a press brake or a roll mill?

                      The Co. that I do work for from time to time has three roll mill lines and a press brake. On the roll lines the material comes off a coil then goes through a straightener . The material length is measured as it comes off the straightener and is then cut off with a flying cut off that is in front of station one of the roll former.
                      I added a disc brake to the last station of the straightener on one of the lines recently and also worked on the clutch for the flying cut off, but did not pay any attention to how the length measuring is performed. I don't recall any encoder wheels on the material though.

                      Steve

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                      • #12
                        Comes to mind that you could fashion a two sided wheel on which to mount an o-ring. Side one would have the hub and the main groove to mount the o-ring, plus whatever encoder pattern, and the second side would tighten up against the side of the o-ring. You'd assemble with a certain amount of tightening to begin with, then surface grind the o-ring to a specified diameter so it can roll out a distance accurately. As it wears, tighten the thing a tad and check it against a known length from time to time.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                        • #13
                          some good ideas

                          thanks guys i have been reading the responses.

                          I will answer a whole bunch of questions with one simple answer. This is not my design. The elctrician i get alot of work from has asked me to build a wheel for his Omron E6C2-C encoder.

                          I want to do the best job for my customer with the limitations they have put on me.

                          I am hoping to find something at the local supplier i can buy or easily modify. I wanted feedback from the board so i have a better idea of what to look for.

                          Thanks for all the replies. I have even considered a knurled wheel. I just don't want it to damage the metal going in or coming out.

                          it is a roll forming machine, with the metal coming off of a roll. If it is the machine i think it is.

                          Again thanks for the feedback. any more suggestions i am all ears

                          Rob

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                          • #14
                            I'd be concerned about oil.....

                            it makes the wheel slip, and it eats some rubber compositions, and swells up others. Either problem affects accuracy.

                            Since all you need is to make the wheel, find a material that is the least sensitive to oil, and preferably get it in a standard form, like an O-ring, etc.

                            A toothed whee;l would slip less if spring-loaded etc.... I doubt it would damage the material free-running, but you might ask. It would need to be hardened within an inch of its life though, as it is harder to replace, and wear would be bad.
                            1601

                            Keep eye on ball.
                            Hashim Khan

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                            • #15
                              Something else comes to mind- if there's going to be a problem with the point contact of the wheel slipping, you could always use two wheels- cogs, actually- and run a toothed belt around them. The belt is what rides on the steel you are measuring. Of course, this method is prone to debris getting in the teeth, and it may not be easy to get it calibrated.
                              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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