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Why are my carriages loose?

Discussion in 'General Talk' started by Troyerta, Nov 20, 2014.

  1. Troyerta

    Troyerta New
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    I'm building off of the pinion example build shown here: http://openbuilds.com/builds/v-slot-belt-pinion-example-build.97/

    but with a 20x20 rail, and the mini v plate. The same exact set of components is shown being assmebled in the first build video shown here: http://openbuilds.com/builds/mini-v-linear-actuator-build.48/

    So - its all gone together nicely so far. Things 'fit' well enough except for the carriage itself. It seems that the eccentric spacers don't actually adjust tight enough for the wheel to securely bite the rail. It gets close. But I need another .5mm before there is no "play" on the rail.

    Have I done something wrong? Has anyone else seen this with the mini-v plate before? I may be understanding something!

    Attached is a photo of what I built so far.. notice anything wrong?
    downsized_1113141643.jpg
     
  2. munchit1

    munchit1 New
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    have you tried monting 90 deggrees into the next track?, dunno after that.
     
  3. blahh

    blahh Well-Known
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    Are your eccentric spacers mounted correctly (the right way around) and in the correct holes?

    Post a couple more photos so we can see more clearly.
     
  4. munchit1

    munchit1 New
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    ahh yes..free spining out of the holes in the plate.
     
  5. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Not a great photo but everything looks appropriate. You might contact the store letting them know of your issues and ask it they can set up a mockup to see if they can dublicate the problem. You can either email contact@openbuildspartstore.com or use the contact form on the about us page (or both). There may be a tolerances issue at the fabricator level that hasn't been called to their attention yet. Providing an order date may help them test the proper batch.
     
  6. slittle

    slittle Journeyman
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    Troyerta, The mini v plate should have 2 small bore holes and 2 large bore holes. The eccentric spacers have to go to the larger bored holes so the bolt has enough room to travel as it rotates to achieve its fullest possible adjustment. If the eccentric's are in the smaller bore hole this would limit the bolts travel to adjust. If you just stick a bolt in the holes you will see quite a bit difference in how much movement their is from small bore to large bore.
    Something to check, you may have already tried this. Just suggesting a possibility. The video shows the proper orientation of the plate, bolts and eccentrics. Hope this helps.
     
    #6 slittle, Nov 22, 2014
    Last edited: Nov 22, 2014
  7. DiggerJ

    DiggerJ Master
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    Any chance your axle bolts may be coming or are staying loose? The picture seems to show the bolts aren't long enough to get to the locking part of the nuts. Just an observation.
     
  8. LozK

    LozK New
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    Hi Troyerta, did you solve this problem at all?

    I have just built a Mini V Linear slide, and closely followed the video (Mini V Linear Actuator Build, published on Sep 29, 2014 by kram242) and I have found that I can't get my carriage tight either.

    All of the parts are in the right places and you can see the bolt heads rotating in a full circle (from above the carriage) as the eccentric spacer nuts are rotated, but even when in their most "innermost" position, the carriage never becomes completely tight. Does this mean that parts are not the right size? I thought that these things would all be made the same?
     
  9. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    It is hard to say where the problem lies but it may be a supplier tolerances issue. Which wheels are you using (black or clear) and what size rail are you pairing them with?

    As a stop-gap measure, I would suggest loosening the non adjustable wheels, pushing them as tightly as possible toward the inside and re-tightening them. There are generally a couple of tenths of a mm of slack that can be removed there and this may be sufficient to solve the problem.
     
  10. Troyerta

    Troyerta New
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    The bolts were long enough.

    The problem was definitely in the eccentric spacers. So whether its a design issue, or a manufacturing issue - it doesn't matter to me anymore.

    I was using the black mini v wheels and all.

    Adjusting the non-adjustable wheels in towards the center as closely as possible did not provide a noticeable difference.

    As you can see, the load on the sled a NEMA 17, but on the other side, I mounted large laser with its heatsink. This balanced the weight on the sides of the sled, but it only encouraged the wobble, and made prints look like hell. See the top row with the wobble in dot height.

    I ended up lining the rail with electric tape to fill the gap. I lined both sides, and the sled felt very tight as a result. If your stepper mototrs don't have enough current at this point, they won't be able to move. If you can't do more current, just rip off the tape from one of the sides of the rail and it should give you somewhat of a balanced improvement. It took about an hour to do. Use one long continuous strip of electrical tape per wheel run, so you should be able to do it with only 4 long strips per sled. See T-Swift for end results. Makes for a nice reproducible setup.

    G78_FullLine.jpg machine.jpg full.jpg
     
  11. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    The tape idea is good creative thinking. :thumbsup:

    You could also drill out the fixed holes to 1/4" and fudge the bolts over. This will provide about .65 mm of closure which should be more than enough.
     
  12. DiggerJ

    DiggerJ Master
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    On a side note, I really like the looks of your printing on the laser!
     
  13. Tweakie

    Tweakie OpenBuilds Team
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    Nice work with the laser @Troyerta :thumbsup:

    Tweakie.
     
  14. Val Cocora

    Val Cocora Veteran
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    Had the same wobbling issue this last weekend, but on a 20x80 v slot rail. Never happened before.
     

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