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Beginner to rail systems/cnc in general.. couple questions on parts.

Discussion in 'General Talk' started by xl97, Jun 8, 2018.

  1. xl97

    xl97 New

    Jun 7, 2018
    Likes Received:
    Hi gang-

    This is my first foray into cnc/rail systems (this is not for a CNC machine, but for an automated bar bot project)

    I was initially going to get this kit:
    V-Slot® NEMA 17 Linear Actuator Bundle (Belt Driven) (1000mm with stepper)

    However.. I dont really care for how the stepper and idle pulley are on the ends.. which make that piece difficult (in my mind) to mount to some upright 'stands/legs' (think of a capitol letter "H")..

    So upon some more research, I discovered the belt & pinion system. This eliminates the wasted space and clean mounting issues when having the stepper/pulleys on the ends, protruding out/past the rail/beam itself.

    I was directed toward this project and parts list:

    And I have some questions I could use some help with.

    I'm not really 'stuck' on using the V-slot rails.. I would be open to using just two round bar/rails... but being new to all this, a kit seemed like it would cost more, but also include things I wouldnt know about/forget about.

    I actually kind like that approach better.. since I can have the stepper and belt be IN BETWEEN the two rails.. (and hence I dont need to worry about the size/placement/footprint of the stepper motor compared to the rest of the project 'frame').. but having to worry about mounting plates...etc would be a PITA I think? (maybe those more experienced in this area can direct/guide me to a system kit like that?)

    1.) If going the belt & pinion route.. what i your 'real' travel? (ie: how much of each side/end do you give up in inches?)

    2.) The wheels in the kit:
    OpenBuilds Solid V Wheel Kit Solid V Wheel Kit

    Are NOT what is shown or talked about in the videos? The videos use an inner V cut wheel.. to help keep the belt in the channel perhaps? Which are we supposed to use?

    3.) The parts list also talks about these 3m 6mm screws:
    M3 Screws 6mm http://openbuildspartstore.com/socket-head-screws-m3-25-pack/

    ** But the link is broken.... I also have read that some of the screws for kits need to be '10mm' ones and they are too short otherwise to secure anything? Is this still true? (a little misinformation out there and for noobs its hard to tell what is what)

    *** I also noticed some of the parts on the list say 25 packs.. but really are only 10 packs... do you NEED 25 of them? (so multiple items are needing to be ordered?)

    I like the belt & pinion approach as mentioned.. but I'm a little leery about the footprint of the stepper itself.. (and how its mounted..... how big are these things? are the measurements in MM? it doesnt say on the image)

    Is there a specific way/orientation the rail/wheels should be when under load (mine will have a very small load/weight..but I'm still curious).... do they need to be 'up-right'? as in the wheels need to be up-right and be vertical in the rail? or can you turn it on its side? (so the rail is more 'flat' and the wheels are more or less laying down? 'horizontal' riding along the rail system?

    I guess I'll stop here as to not overwhelm you guy or myself! LOL

    I'm hoping to get this ordered as soon as I have a nice game plan/direction.

    Thanks for any feedback!
  2. Rick 2.0

    Rick 2.0 OpenBuilds Team
    Staff Member Moderator Resident Builder Builder

    Dec 20, 2013
    Likes Received:
    You basically lose the width of the plate which for the one shown is 88mm. So for a 1000mm section you'll come up just shy of 36". When you figure a small gap at each end so you don't smack the end brackets it's probably best to assume around 35"
    The example you're working from is a very old example, created prior to adding the Solid V Wheels to the OpenBuilds system. The Solid V Wheels though are the recommended wheels for using the belt/pinion method as they support the belt better where it is pulled up from the track to loop around the pinion.

    Again the example is a very old example. The shop has recently started packaging screws in packs of 10 rather than 25. All screws can be found here Hardware - Screws - OpenBuilds Part Store Once you have selected the type of screw needed the length can be selected on that specific type's page.

    Yes the images are in millimeters. (In imperial units though a Nema 17 motor is 1.7" square, Nema 23 is 2.3" square, etc. But you still have to do metric conversion on the depth as different models have different depths)

    For light loads it doesn't really matter. For heavy loads and constant use though it is best that axle be horizontal (similar to an automobile).

    And please note there is no specific reason to order a kit if the parts in the kit don't specifically meet the needs of your project. The kits only exist to simplify the ordering process. Financially there is generally very little difference between the kits and ordering the same specific parts a-la-carte.
    MaryD likes this.

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