Revolutionary Linear Drive System - Page 2


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%
Multiple Choice Poll.
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Thread: Revolutionary Linear Drive System

  1. #13
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    Quote Originally Posted by svenakela
    The big linear guide manufacturers (INA etc) have guides with built in decoders, wich gives an absolutely no-backlash positioning. The only minor thing is - the price...
    But at the last tech fair I visited there was a Chinese guide manufacturer that had the same solution but to a price that was reasonable. Still not cheap, but very interesting if precision is an issue.

    Regards,
    Sven
    svenakela,
    What is the web site for the INA manufacturer? Also, what is the name and web site for the chineese manufacturer the makes cheaper but similar devices that you mentioned?



  2. #14
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    Default Roller chain/sprocket inside out

    It's said there's nothing new under the sun...

    I Look at this and I see a roller chain drive. The only difference is that the "sprocket" has been turned in to a "rack"; and the roller chain itself becomes the pinion.

    Since I've had good luck in the past with roller chain drive; I'll probably just keep using that inexpensive system; knowing that this "update" confirms what I've always felt about its suitability for axes driving...

    Ballendo

    P.S. Allan, Are you an employeee of Nexen?

    The comments farther down suggest that the pitch error of ballscrews and nuts needs to be corrected by encoders. I disagree; and feel that there is some advertorial going on here... It--lead error-- is pretty simply accounted for by adjusting the steps per unit to accomodate this increasing or decreasing error. The rolled thread techniques used for precision rolled ballscrews will favor a lead error over a cyclical error, since lead error is EASILY reduced/removed; whilst cyclical error is the bane of every linear motion drive system.

    From what I can see, the nexen drive will have the same issue od "lead" error. It will be due to the pinion PD not being perfect. And can be accomodated the same way.

    The problem with chain and this nexen drive is that it has an uneven speed of motion. The pinion is essentially a polygon instead of a circle; and since the effective radius changes for any polygon inversely to the number of sides, there WILL be uneven motion speed. The "Rack" tooth profile will attempt to minimise this, but it will still be there.

    The epicycloidal flank shape of gears is designed to eliminate this by providing a constant diameter circle at the PD where two gears intermesh. This flank shape is also designed to minimise relative sliding motion between the gear flanks to minimise wear. The nexen drive will suffer from the same wear effects as roller chain, albeit perhaps to a lesser degree since the rollers of the pinion ostensibly have better bearings than the ones used in small roller chain. But over time the rollers will wear and their diameter will no longer fit the rack tooth profile exactly. And the rack profile will similarly wear and no longer match the roller diameter. Without a means of compensation backlash will result. Since there is not a "wedging effect" as found in "normal" rack and pinion--the root of the nexen tooth form appears to match the roller diameter exactly--there appears to be no ability to "deal with" this wear outside of replacement.



    Quote Originally Posted by allanconway2
    Nexen has a new revolutionary linear drive system that is similar to rack and pinion but eliminates it's short comings. This makes it a better choice for many applications that typically use traditional rack and pinion, ball screws, and linear motors. See attachment for details.




  3. #15
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    I think the single most determining factor in a " home built CNC " or a hobby use machine is availability. We like ballscrews because they are cheap and plentifull. I dont see a very large number of people on this forum buying things new, unless they are surplus items. Im sure if you dumped a ton of "Revolutionary Linear Drive Systems" on the surplus ebay market, they would become very popular overnight.

    Halfnutz

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  4. #16
    Registered JavaDog's Avatar
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    Quote Originally Posted by Halfnutz
    I think the single most determining factor in a " home built CNC " or a hobby use machine is availability. We like ballscrews because they are cheap and plentifull. I dont see a very large number of people on this forum buying things new, unless they are surplus items. Im sure if you dumped a ton of "Revolutionary Linear Drive Systems" on the surplus ebay market, they would become very popular overnight.
    Unless, of course, they are cheap as **** new. I know, I know...wishful thinking.

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
    Check Out My Build-Log: http://www.cnczone.com/forums/showthread.php?t=6452


  5. #17
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    I work for INA USA. I don't have anything to sell, just my 2 cents. Actually I work out on the shop floor. As far as price goes, you will never beat China! Coolman here is a link ----> http://www.ina.de/inaupdate/homepage4_gb.asp?flash=1 Do a search for Linear at the bottom of the page. Im not really sure what svenakela is refering to
    The big linear guide manufacturers (INA etc) have guides with built in decoders, wich gives an absolutely no-backlash positioning.
    INA has so many products.



  6. #18
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    I looked at these Nexen rack/pinion. I opted not to use them simply because they couldn't take the power of the 640 oz steppers I planned to use. If you jump up to the next size pinion, then you loose resolution, its a dog chasing its tail type thing.. to get the resolution you'd need to up the reduction, which up's to torque which means you need a bigger pinion.. etc etc..

    I settled on steel rack/pinion... besides.. its cheap and you can purchase it locally..

    Jerry

    JerryFlyGuy
    The more I know... the more I realize I don't
    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  7. #19
    Gold Member dertsap's Avatar
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    Quote Originally Posted by allanconway2
    Nexen has a new revolutionary linear drive system that is similar to rack and pinion but eliminates it's short comings. This makes it a better choice for many applications that typically use traditional rack and pinion, ball screws, and linear motors. See attachment for details.

    thats a nice system and anyone with a cnc mill can easily build that system ,ive seen it a while back and its been stuck in my head for a while now, the rack can easily be made out of 6061 layed on its side ,contour the profile ,then hard anodized , same goes for the pinion housing with dowel pins pressed in , considering a 6061 bike sprocket can take the abuse , it would take a long enough time to wear the rack out , and its light weight easy to machine

    OH CRAP now im rethinking my current router design im working on



  8. #20
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    I run 0.8" PD X and Y rack gears on a NEMA 34 5' x 10' CNC router. I'm not that enthused about the microstepping needed to smooth out movements. The motors barely turn, about 40 rotations for the 100 inches of travel it has. Yes, it has hit 1200 inches per minute, but most of my work is in the 100 inches per minute range. It would only exaggerate the issue with a larger pitch diameter. Ballscrews are like a free gearbox being added, multiplying torque, increasing resolution (reducing microstepping), and driving an axis, what a deal! The Nexen system looks better and less noisy than a rack system, but with the increased PD, router users will run out of stepper pulses and mill users will run out of torque. I'm a free torque multiplying, increased resolution, drive my axis guy.

    Jim



  9. #21
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    pinion gear systems suffer most from lack of contact area. A single line of contact under less than ideal lubrication will always lend it's self to a short "high precision" service life.

    Ball screw systems would represent multiple point contact. The stress strain (deflection) values would be an interesting comparison.

    CalG



  10. #22
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    There are no long wearing aluminum chain sprockets on the countershafts of modern motorbikes.

    The rear sprockets have many teeth in play at once.

    Just to compare systems



  11. #23
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    I recently came across this thread, and it caught my attention. A rack and pinion system that accurate and efficient has got to have potential, right? So I got a few quotes on this system for a machine I am building (a VMC).

    Comparable in price to ball screw? My a**!... If your still reading this thread and are interested in RPS, expect to shell out about $3500/per axis (36" axis, 700-900ipm, 2500/lb expected max dynamic load)... and that price is before before you get into all the little things (mounting brackets etc.) Building a decent scale 3-axis machine with this system, expect to spend $12,000 (roughly my whole budget for this project) in power transmission...

    What a joke... On the bright side they say its good for 30million hits lol...

    Well, I just figured if anybody else bumped into this thread I might save you some time...



  12. #24
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    if pins are stationery, then they are sliding on teeth..
    and if so then I have doubt about how much is it resist wear..

    the good side of, always at least two teeth connecting..

    compared with pinion and rack, pinion has an evolvens surface, what is not same like an arc..

    bicycle chains has "rolling pins" in the chain.. and certain way they are not sensitive for a minimal backlash


    I wouldn't compare with ballscrews.. I would be very much interesting for the first haas mill using this system instead ballscrews

    a plotter or a printer, wheres no load, there mightbe used, but those are working with timingbelt very well..



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