Welcome to Our Community

Some features disabled for guests. Register Today.

Designing T-Bot

Discussion in 'DrawBot' started by Rakesh Raghvani, Sep 18, 2018.

  1. Rakesh Raghvani

    Rakesh Raghvani Well-Known
    Builder

    Joined:
    Sep 18, 2018
    Messages:
    7
    Likes Received:
    5
    Hello,

    Is it possible to use one gantry plate in-between two v-slot linear rails (20x60mm) so that it can be moved along the X and Y axis?

    I want to build a T-Bot similar to this design H-Bot…Just for fun at Buildlog.Net Blog, but I don’t know what gantry size I require, and I’m not sure whether it’s possible to have wheels on both sides of the gantry using the same holes.


    Thanks
     
  2. Rick 2.0

    Rick 2.0 OpenBuilds Team
    Staff Member Moderator Resident Builder Builder

    Joined:
    Dec 20, 2013
    Messages:
    2,098
    Likes Received:
    969
    Absolutely. Here is an example for C-beams but a similar approach is viable for the belted example you referenced.



    You can download this example XY plate file here C-Beam XY Example Plate.zip
     
  3. Rakesh Raghvani

    Rakesh Raghvani Well-Known
    Builder

    Joined:
    Sep 18, 2018
    Messages:
    7
    Likes Received:
    5
    Thanks Rick 2.0, that’s exactly what I want. However, I don’t have a CNC machine to make my own part – yet!

    From openbuildspartstore.com, what gantry would I require, to achieve similar results? Is there anything else I need to consider, such as bolt sizes etc?

    Apologies in advance with the questions. I’m new to v-slots.
     
  4. Rick 2.0

    Rick 2.0 OpenBuilds Team
    Staff Member Moderator Resident Builder Builder

    Joined:
    Dec 20, 2013
    Messages:
    2,098
    Likes Received:
    969
    Unfortunately there is no single plate that will do the trick. You might be able to make it work with a couple of V-Slot Gantry Set - Universal mounted back to back which would actually be similar to the referenced example. You will need 4 extra wheel kits, 4 extra M5x25 screws and 4 additional 6mm stand offs. You will also need to drill (4) 5mm holes in the plates for the additional wheels.

    Personally, I would take a scrap of 4mm aluminum and make/drill the plate myself. Hand made plates are really not that difficult.
     
  5. Rakesh Raghvani

    Rakesh Raghvani Well-Known
    Builder

    Joined:
    Sep 18, 2018
    Messages:
    7
    Likes Received:
    5
    I think taking a sheet of aluminium and drilling a few holes would be the easier option.

    Thanks again.
     
  6. Rakesh Raghvani

    Rakesh Raghvani Well-Known
    Builder

    Joined:
    Sep 18, 2018
    Messages:
    7
    Likes Received:
    5
    Here's my plate. Wasn't that hard to make after all!

    IMG_20181015_203850.jpg IMG_20181015_203819.jpg
     
  7. Rakesh Raghvani

    Rakesh Raghvani Well-Known
    Builder

    Joined:
    Sep 18, 2018
    Messages:
    7
    Likes Received:
    5
    After purchasing the various V-Slot parts and building a suitable gantry plate, I’ve now managed to build my T-Bot. The T-Bot will eventually be used as a drawing machine, similar to AxiDraw, but using SlushEngine Model X LT and Raspberry Pi 3. Here’s my first working version on YouTube. My next task is to read G-Code and make to T-Bot move according to the coordinates.
     
    MaryD likes this.
  8. Rakesh Raghvani

    Rakesh Raghvani Well-Known
    Builder

    Joined:
    Sep 18, 2018
    Messages:
    7
    Likes Received:
    5
    I’ve made a T-Bot similar to this design. Using stepper motor driver L6470, I can control the movements e.g. up/down, left/right and diagonally using the equations shown here corexy, via the L6470 command MOVE(direction, number_of_steps) using MAX_SPEED(100 step/s).

    If I move from (0, 0) to (400, 400), both stepper motors move at a constant speed, and reaches (400, 400). Great.

    If I move from (0, 0) to (400, 100), then I need to reduce the speed of one of the stepper motors by 4 times (400 / 100 = 25 step/s). Fine.

    However, if I move from (0, 0) to (400, 300), I reduce the speed of one of the stepper motors by 1.3 times (400 / 300 = 1.333 step/s). Slight issue here, MAX_SPEED only accepts integers and therefore the linear path it follows is not correct – one stepper motor will stop before the other, and a diagonal line is not drawn correctly.

    Is there a way of resolving this issue?
     
  9. Rakesh Raghvani

    Rakesh Raghvani Well-Known
    Builder

    Joined:
    Sep 18, 2018
    Messages:
    7
    Likes Received:
    5
    Update,

    As I was unable to use the methods provided by the L6470 chip, to do what I wanted. I have now used Step Clock mode instead. I have written methods which allows me to rotate the stepper motors a step (i.e. 1.8 degrees); using Bresenham’s line algorithm to draw diagonal lines without having to decrease or increase speeds.

    Here’s a little video, which follows some basic coordinates.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice