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V-Slot Custom Rack & Pinion

Discussion in 'General Talk' started by Adam Filipowicz, Apr 14, 2018.

  1. Adam Filipowicz

    Adam Filipowicz Veteran
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    Hey Guys

    Ive been skimming the board looking for Rack & Pinion ideas
    I would like to come up with a design that will nest in and centre itself into V-Slot channels
    looking to start some brainstorming/discussion

    I am no engineer,, just a hack with Fusion 360
    so if someone can draw this up better please do!

    perhaps we can get this spec'd out and have a company produce them for us.

    using 20 pitch/20 pressure angle for this mockup
    let me know your thoughts

    holes to be 5mm Diam with 9.2mm for head to clear, 3mm depth
    Spacing 50mm apart
    Machined ends so they can be stacked

    Thoughts on making these from Aluminum instead of steel

    these parts originally came from McMaster Carr
    McMaster-Carr

    McMaster-Carr

    cbeam rack 1.JPG cbeam rack 2.JPG cbeam rack 4.JPG
     
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  2. ChristopherBishop

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  3. Gary Caruso

    Gary Caruso OpenBuilds Team
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    there was a thread of a possible uhmw rack with brass pinion a while back..But the pics were censored out of openbuilds :D
    Aluminum has bad wear characteristics, makes for black residue all over everything.. and for strength nylon or uhmw is good enough with superior wear resistance with no lube requirements.
    But yes this has to happen some day! I played with the idea of making my own rack sections out of 1/4" HDPE, even made a sample that worked out well, but i would have to make a bunch of it and build another system to test it!
     
  4. Jonathon Duerig

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    The CNC Router Parts rack and pinion works well with C-Beams. That is how my current machine is set up. Steel racks, steel wheels. It isn't terribly cheap, but probably cheaper than custom fabrication.
     
  5. Adam Filipowicz

    Adam Filipowicz Veteran
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    can you post a pic of your current setup
     
  6. Gary Caruso

    Gary Caruso OpenBuilds Team
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    I agree the cnc router parts ones are very good, But there are a ton of chinese suppliers who make plastic racks that would suite our load needs, just a matter of finding one the right size and quality.
     
  7. Adam Filipowicz

    Adam Filipowicz Veteran
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    also the CNCRouterparts Belt reduction looks very large.. hoping perhaps for a direct drive.. or gearing down a Nema 23 via 5:1 planetary or worm gear.
     
  8. Mark Carew

    Mark Carew OpenBuilds Team
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    Hey guys, I want to jump into this discussion. We have been working on this goal as well in hopes we can all work toward an idea that we can call an OpenBuild standard. Racks are the logical next step for the OpenBuilds system and it would be great to be able to use something pre-made to save on custom but I think the advantage of making them to spec designed for the system will have its own benefits. Staying true to the OpenBuilds way with the idea of keeping it simple we were thinking here of spring tension direct drive (use motor tuning to get proper accelerations) Also thinking less thick racks especially with steel, which to be honest in it self may be over kill for the system, but trying different materials that allow for out side use as well as smooth operation, for instance nylon racks. Lets remember all the cool things we are already able to do with the belt and pinion style system so racks will only be an added plus to the ideas of machine building.
    We have been experimenting with a few ideas but most are over kill steel racking so we want to hear some of the applications and ideas you guys may have. This is a great discussion and a look forward to seeing how it weighs out.
     
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  9. GrayUK

    GrayUK Openbuilds Team Elder
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    We would need a rack that had screws in the bottom of it, the heads of which would, as in the style above,
    slide snuggly into the slot beneath it, and then simply put a plate at each end, holding it in place. SIMPLES! :thumbsup::thumbsup:
     
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  10. Adam Filipowicz

    Adam Filipowicz Veteran
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    Since most of these machines are fairly low load, looking at other materials is a good idea.. how about Delrin, its easy to machine.
     
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  11. Jonathon Duerig

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    Adam, this is the same machine I mentioned in another thread about this about a year ago:

    https://openbuilds.com/threads/rack-pinion.9874/#post-57134

    Coming up with systems explicitly designed to work with C-Beam seems like a good idea, though. When I did this, I was mostly concerned about what I could build myself based on what was available. If there had been something available that explicitly made for use with OpenBuilds, it would have reduced my nervousness would have obviated a few workarounds I had to do to make everything work. If somebody wants advice and confidence about what works for making a machine today with CNC router parts and C-Beams, I'm happy to advise. But in the longer term I'd love it if there were standard rack-and-pinion plates and parts available at the OBPS.

    Regarding materials, the benefit of steel here isn't the strength, IMO, it is the durability. Right now the plastic wheels are the weakest link in the system in terms of long term durability. When I rebuilt my machine last year, I had to replace all of them. And I expect to need to replace them again at some point. I would expect a plastic rack-and-pinion system to wear even faster. But the disadvantage of steel is weight. I need bigger motors just to move my gantry around even when not carving. I'm not sure the right trade-off here. But atm, the steel works well for me.

    I'm not sure what the best gear reduction is. I think the CNC Router Parts are 3:1 for NEMA 23 motors. It is precise enough that the only issues I have with reproducability are if the material itself moves or deflects. And it moves fast enough that I don't feel like the rapids are slow. But if somebody presented me a machine with direct drive or with a 5:1 reduction, I don't know that I'd really notice.

    -Jonathon Duerig
     
  12. Mark Carew

    Mark Carew OpenBuilds Team
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    Delrin could be an option but to be honest although POM will give us great sliding wear, we need a higher impact as well and like Jonathon mentioned on a rack you would not want the wear that delrin will give.. We were thinking of going much harder and testing out NYMETAL or nylon66 it has high wear. The idea would be to use perhaps aluminum rack with nylon 66 pinions if replacements are needed years down the line it would be an inexpensive pinion and not the whole rack. just ideas at this time, but testing will tell a lot more.
     
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  13. Adam Filipowicz

    Adam Filipowicz Veteran
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    Work in progress
    5D3_2896.jpg
     
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  14. Mark Carew

    Mark Carew OpenBuilds Team
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    Look great @Adam Filipowicz can you share more info on this rack and pinion. I would love try it out this side as well.
    Thanks man :)
     
  15. Adam Filipowicz

    Adam Filipowicz Veteran
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  16. Ronald van Arkel

    Staff Member Resident Builder Builder

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  17. Gary Caruso

    Gary Caruso OpenBuilds Team
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    Nice, that's exactly what i want!
     
  18. Adam Filipowicz

    Adam Filipowicz Veteran
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    can you share info on these parts. what are they, where are they from?
     
  19. Ronald van Arkel

    Staff Member Resident Builder Builder

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    Hello Gary and Adam,

    The above images were just a design and never produced due to the lack of interest. Gary found the "uhmw rack with brass pinion" topic with no Images so I though to post them again.
     
  20. Adam Filipowicz

    Adam Filipowicz Veteran
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    Thank you, can you share the design files with me? also what Pitch is this rack
    and how many teeth are the pinion?
     
  21. Ronald van Arkel

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    Sorry Adam, I can not share the design as it is not sold on openbuildspartstore.com or an OpenBuilds design, also still Alpha. Please continue with what you were doing, seems there is some interest for your design.

    The images show a Module 1 rack and pinion, the rack is 410.7mm long, 10mm in height, 20mm width. Pinion is 20t, 19mm width custom made.
     

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