Revolutionary Linear Drive System - Page 5


View Poll Results: What is your prefered high precision linear drive system?

Voters
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  • Ball Screws

    154 63.37%
  • Rack And Pinion

    33 13.58%
  • Linear Motor

    20 8.23%
  • Lead Screw

    22 9.05%
  • Nexen's Roller Pinion System

    12 4.94%
  • Other

    15 6.17%
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Thread: Revolutionary Linear Drive System

  1. #49
    Member handlewanker's Avatar
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    Default Re: Revolutionary Linear Drive System

    Hi, as soon as anyone mentions resolution it immediately gravitates to .01mm accuracy, no matter how big or small the machine, whatever.

    If you had a small 3020 type router made with Hiwin linear rails and top market ground balls screws, that would be "normal" or up to expectation, but if you are in the realms of a 5 meter long table router and got .01mm accuracy that would be stupendous.

    The size ratio between small and big apparently is not a factor in the equation, but at 16 1/2 times the size, the scaled comparable accuracy for .01mm would be ,165mm, and you could get that from an aluminium built machine by expansion and contraction on a hot day or when frozen

    Big ball screws are the way to go if your pocket is deep enough and .01mm is in the air, otherwise the chain is only as strong as the weakest link.........the other way is to use encoders and know where you're at even if you can't accurately step the way from end to end on long travels.

    Backlash can't be cured by fitting an encoder, even if it adds movement to compensate for lost movement etc, and backlash is a bogey when climb milling anywhere.

    I think there has to be a sliding graph for the expected accuracy of travel and applied to the size of machine when doing a DIY model, from small to very big.......large commercial models are expected to attain the .01mm out of the box......the mega bucks price tag ensures that.
    Ian..



  2. #50
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    Default Re: Revolutionary Linear Drive System

    you re right..

    that was only example.. but in reality hard to imagine any serious manufacturer use this roller system versus a ballscrew..

    -----------------------------------------------------------------

    probably fitting 150 pices of 100 mm gauge wouldn't work to checking the 15 meter length :-)
    for precise machinery the only way is the linearscales..

    rotary encoders will copy all error from screws..



  3. #51
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    Default Re: Revolutionary Linear Drive System

    But if its a known error, its easy to use pitch error compensation. All depends on what its being used on. Don't think it would be stiff enough on a high speed machining center, but may be fine on routers, lasers and waterjets that really don't need the stiffness.



  4. #52
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    Default Re: Revolutionary Linear Drive System

    Hi, DIY people are not really in the class of serious manufacturers in the hobby sense, as in they only want to make a one off and hope to us it as such, but as soon as you start going big, the exponential curve of lack of accuracy become the biggest problem too.......how do you measure anything over 300mm with any degree of confidence without having the facilities of a temperature controlled environment.

    I think the reason why short pieces and lots of them are in this design, is because you can measure and make short pieces relatively accurate and also align them one to another over a length to be accurate more than you could cut a long rack and hope to have it anywhere near to the ideal for close tolerance production.....but provided you can measure the overall length to detect accumulated dimension creep etc.........you'd still need to have measuring equipment to detect the overall length of the racks.
    Ian.



  5. #53
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    Default Re: Revolutionary Linear Drive System

    Hi....pitch error compensation only works when you know if the overall length of the segmented parts is in error.

    You could measure one segment and find it had an error of .05mm overall.......joining segments together does not eventuate in an exact accumulation of the ,05mm times the number of segments........that's the ideal World.

    I think the Nexen system is costly and for those that need it as opposed to rack and pinion or long ball screws etc.

    Making either the rack or the pinion to the Nexen design would be a compromise in accuracy......it could be done but the end result is not guaranteed.

    A lot would depend on the alignment of the pinion to the rack segments, and over a long length that means in line and perfectly pitched.........measuring the pitch over a long length is a problem of metrology, whereas the alignment is a total "fits where it touches" scene......the carriage must ensure that a linear contact with the pinion and rack is maintained 100% at all times or you'll lose pitch if the pinion moves away from the rack by even a few hundredths of a mm.

    I think even a simple steel rack and pinion needs a resiliently mounted back up roller to keep the pinion meshed with the rack or it'll have loose and tight spots that defeat the object of the exercise.
    Ian.



  6. #54
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    Default Re: Revolutionary Linear Drive System

    Pretty easy to measure long distance accurately. Just need a laser system. Ive done 20ft travel machines myself. Not a diy solution though.



  7. #55
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    Default Re: Revolutionary Linear Drive System

    Heh Heh......I would think that anything 20 ft long would be difficult to measure accurately by any means......you'd first have to have a standard that was set at 68 deg C in a laboratory to ensure what you were measuring with was able to actually give you an accurate reading and were talking in terms of .01mm accuracy as said before.

    As I also said, large items probably don't require to have the tolerances that small items need......certainly not to + - .01 mm sizes, and working with a router those tolerances most probably will never occur for any work anticipated.

    As we're discussing the Nexen drive as opposed to actual measuring means, if it can be made less expensive then possibly more people would use it by choice.....more people....more turn over....a less expensive product.

    Ball screws would be in the gold class if only a few people used them instead of the Acme threaded screws for transmission, so in the first instance, anything used in place of the mass produced ball screw has a tough act to follow, and the Nexen drive system is in that category.

    So, do you gain any more accuracy or travel speed over a long distance with a Nexen system as opposed to a plain and simple rack and pinion or even chain drive with the chain being the static member.

    If the answer is "not all that much"......where is it going and for what reason?

    I don't think being potentially backlash free has a big tick in the must have box if the cost is also on the high side.....making a rack and pinion fit tighter will also reduce any backlash.

    When I work with a manual mill I always nip up the lock on the dovetail slides to ensure that the slides don't wander, and for fast traverse it just runs as free as the slide way dovetails are adjusted to......the same applies ,to rack and pinion....tight set for feed work and slack for fast traversing etc will ensure the ideal World without spending mega bucks..

    If you want a perfect World you need to have a perfect system, so tight for feed work and slack for fast traverse, and how that is accomplished is the price you have to pay, but you have to accept compromise and draw the line somewhere.
    Ian.



  8. #56
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    Default Re: Revolutionary Linear Drive System

    We shoot for 10 microns over that length. Lasers have weather stations, so they can comp for small deviations. Shop is at 68, this shop is +/- 2 degrees usually, not the precision shops that hold within 1.
    I still think this design will show some camming or cyclic error trying to interpolate a circle.



  9. #57
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    Default Re: Revolutionary Linear Drive System

    Hi, I don't think the manufacturers would have marketed it if it showed design faults.

    You would actually need to go out and buy into the system to find out if all the blurb was true and then do extensive testing to prove otherwise.

    The object of having this design as opposed to a regular rack and pinion or ball screw is relying on the integrity of the manufacturer to take advantage of the attributes and justify the cost.......extensive testing should never come into the picture, that is..... fit it and forget it.
    Ian.



  10. #58
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    Default Re: Revolutionary Linear Drive System

    Quote Originally Posted by handlewanker View Post
    Hi, I don't think the manufacturers would have marketed it if it showed design faults.

    You would actually need to go out and buy into the system to find out if all the blurb was true and then do extensive testing to prove otherwise.

    The object of having this design as opposed to a regular rack and pinion or ball screw is relying on the integrity of the manufacturer to take advantage of the attributes and justify the cost.......extensive testing should never come into the picture, that is..... fit it and forget it.
    Ian.
    I'm not sure why this is even being talked about, it's close to the same price as a Ground Ballscrew, has some backlash, should never be compared to a Ballscrew, it is however better than a rack & pinon but the hobby user will use the cheaper rack & pinion, I have seen them working on a large scale, and they work very well, it's like all means of motion they have there place, and that is where they are being used

    This drive system could never be used where a Ballscrew is needed, for precision positioning so don't compare the two, there is no comparison

    Mactec54


  11. #59
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    Default Re: Revolutionary Linear Drive System

    Hobby router: 100 um
    Hobby mill: 10 um
    Precision mill: 1 um
    Optics machine: 100 nm
    Semiconductor fab: 1 nm
    You pays your money and gets your choice.

    But that roller system - I think it sank in the market. Haven't heard it mentioned for years.

    Cheers
    Roger



  12. #60
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    Default Re: Revolutionary Linear Drive System

    overall beyond an interesting approach, its expenses, and way less effective than already in use solutions.



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