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Discussion in '3D printers' started by Carl Feniak, Sep 29, 2014.

  1. Tweakie

    Tweakie OpenBuilds Team
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    Two motors, each with their own drivers and sharing the same Step and Direction signals and two motors being run by the same driver is not good practice. (More details in Section 7 here http://www.openbuilds.com/threads/electronics-101.693/)

    Tweakie.
     
    #91 Tweakie, Oct 22, 2014
    Last edited: Oct 22, 2014
  2. DarkAlchemist

    DarkAlchemist Well-Known
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    Exactly my point. I wish I could get away from it and they say that using two drivers, instead of one, causes sync issues even more. All I know is that two motors using the same driver is just bad all around.
     
  3. Tweakie

    Tweakie OpenBuilds Team
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    Who says ??

    Tweakie.
     
  4. DarkAlchemist

    DarkAlchemist Well-Known
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    Well, Josef Prusa for one. I asked him why he went with two motors driven by a single channel (driver) and that was his answer to me.
     
  5. Tweakie

    Tweakie OpenBuilds Team
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    Just modified my original post, after re-reading it, to correct my error.

    Basically, when using two motors to drive a single axis you need to have one driver for each motor, they need to be slaved, they need to be 'homed' to synchronize position and you need to manage any disable events applied to the drivers (i.e. homing again after any disable event or not using disable at any time during the current job run).

    Tweakie.
     
  6. DarkAlchemist

    DarkAlchemist Well-Known
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    More work with a better outcome. As it is Z had to be turned up to almost double (strange it wasn't exactly double) what the other drivers current was. I am just surprised the Z driver hasn't blown.
     
  7. Giuliano M

    Giuliano M Well-Known
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    Yeah, there is that - I'm basing the idea off of something like this:

    http://q3dprinter.com/rxl.htm

    Again the linear bearings are what constrain the platform to rise/fall equally at each corner.

    With 8 V-wheels at each corner, they'd have to have some level of clamping force to prevent the wheels from deforming or preventing the ends from racking.


    The other thought I was having was to rotate the Z plate by 90 degrees, and use the wider 40mm portion of the rails as the bearing surface rather than the narrower 20mm surface.

    Or possibly the addition of the harder polycarbonate wheels: http://openbuildspartstore.com/openbuilds-xtreme-solid-v-wheel/
     
  8. DarkAlchemist

    DarkAlchemist Well-Known
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    On a 3d printer do you really think you would need that?

    One thing I never understood are these printers with only one side supported and the X axis moves to the side with no support. Ahem, yeah, you would never catch me buying something like that, lol.

    Here is another joke (poor people who bought, or are buying it) but a printer by QUBD is made out of laser cut cardboard EVEN THE HOTEND is supported with cardboard. *shudder* :(
     
  9. Giuliano M

    Giuliano M Well-Known
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    Probably not, I'm mostly looking into it for the H-gantry / Core XY system and trying to design something that can do a 300 mm cubed build volume.
     
  10. DarkAlchemist

    DarkAlchemist Well-Known
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    My next build I am going for a bigger heated bed as 200x200 is just a smidge too small to do the things I wish to do. Oh, and I am going to try to get more even heat which is a bit of a task but I do have some ideas.
     
  11. Giuliano M

    Giuliano M Well-Known
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    I think I've come up with a variation on this that I am liking.

    It's more or less the same, except that the box frame and Z gantry are both rotated 90 degrees, and a the XY belt paths are mirrored/flipped/inverted with the crossover belts riding along the inside of the back frame rather than on the outside of the back frame.

    All of the purple 20x40 lengths are 500mm, easy pre-cut lengths - the rest are cut shorter.


    I may decide to replace the Z gantry wheels with a set of the Mini-V end plates, and / or the mini-V rails and wheels: http://openbuildspartstore.com/mini-v-plate/
     

    Attached Files:

  12. JCPhlux

    JCPhlux Well-Known
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    Part of the purpose of the design is that you eliminates ghosting that come from the y axis shifting back and forth.
     
  13. DarkAlchemist

    DarkAlchemist Well-Known
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  14. JCPhlux

    JCPhlux Well-Known
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    Ghosting a.k.a. Vibration a.k.a. ripple a.k.a. shadow is the axis vibrating as it attempts to come to a stop. Any number of mechanical things in that chain will contribute to it, the springiness of the belt and rigidity of it's mount, any bounce back from the stepper and even mechanical rigidity of the entire frame along that particular axis. You can combat it by lowering the moving mass, stiffening the mechanics, lowering the speed, and/or lowering the acceleration.

    This design lowers the moving mass.
     
  15. DarkAlchemist

    DarkAlchemist Well-Known
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    Ahh, yes and that can get pretty high. You will see that in the print as the lines will be wavy.

    I am lucky as that is the only issue I have never had.

    Oh, how hard is this design to have a level bed? On my I3 rework I had to go to Automatic Bed Leveling as I could not ever level it (using a dial indicator) and I spent over 200 hours (sometimes over 16 hours in a single day) trying to level it. Flat it is (has to be for ABL to work) but never level.
     
  16. Ryan W

    Ryan W New
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    Looking at your design for my first 3d printer build. I've been doing research into reprap designs, specifically the prusa i3 design. I looked into the i3v from makerfarm, which lead me to Openbuilds, and to your C-Bot design.

    I've looked into kits such as the iv3 from maker farm, the Prusa i3 Rework from Replikeo, and other prusa kits. I'm on a budget so I would source all the parts separately to save on costs.

    That being said, since this is my first build, do you think I could get your c-bot built correctly, or should I go with the a widely supported reprap design? I realize reprap would be a good learning experience, but I'd rather learn on your design.
     
  17. DarkAlchemist

    DarkAlchemist Well-Known
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    I have an I3 Rework Single Frame (Aluminum) and let me tell you go with the c-bot. I spent over 200 hours trying to level my bed alone and I never managed it so I had to go to ABL (Automatic bed leveling) and man was that a chore to implement. It was such a chore (I am no dummy about electronics and programming) I had to go to a forum to get help and all of that is just the tip of the iceberg in the garbage issues I have had to deal with. I use 8mm chromium steel rods from Mitsumi (the 22 dollars a piece ones (not including shipping)) and using the V-Rail system you can eliminate the need for that. In my instance the C-Bot would be less expensive with a fair amount of less trouble too.

    Now, the only issue with the C-Bot, for me, is cutting the extruded aluminum perfectly straight and cleanly. C-Bot is less demanding with that due to the printed parts but that brings up an issue for you if this is your first printer...how are you going to get the printed parts??? With an i3 the parts, and all in one kits, make it very easy to have something but there are no c-bot rp sources that I know of so as a first printer it would be very hard to source that.
     
  18. Ryan W

    Ryan W New
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    Thank you very much for your input.

    I have a Da Vinci 1.0 that I should be able to print decent parts with. I've been playing with it for the last couple weeks. Mostly learning the ins and outs of loading custom Repetier firmware on it, and doing some small prints. The little blue pick axe in my profile picture I printed with the Da Vinci.

    You have motivated me to continue filling out my own BOM and see what my final cost will be and go from there.

    Thanks again!
     
  19. DarkAlchemist

    DarkAlchemist Well-Known
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    "Looking at your design for my first 3d printer build."

    Ahhhh, I took that to mean this was your first printer so you should be golden then and you will be much happier using a printer designed around V-Rail than any I3 and all of its variants. That is my opinion at least.
     
  20. Carl Feniak

    Carl Feniak Journeyman
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    Was off on vacation. I will finally get to work on some build instructions.
    Depending where you are at there are a few options for getting printed parts for your first reprap printed (assuming kits aren't available like for the prusa and mendel).
    -fellow reprap printers in your area; try reaching out on the reprap forums
    -maker/proto shops, it seems they are popping up in all major cities and you'll be able to get in person advice
    -public libraries in certain areas are getting 3D printers!

    I've never had issues leveling the bed in either of my printers. This is my approach:
    -Assuming the frame you are working from has been squared off during the build process, the first step is to level the moving Z frame relative to the XY plane which I do by measuring the vertical distance from rear Z bar to the static rear belt pass through bar and equalize the distance on each side by adjusting the lead screws. This should checked before making adjustments to the build plate level in the future but errors here from future offline movement of your lead screws will be corrected for in live tuning your first layer height.
    -Then I pre tension all 4 corners of the build plate adjustments so they are fairly rigid but still have some range left in the spring (you are probably not using springs with your heavy build plate). Visually level the bed based on the bolt lengths to give a very rough level.
    -Next I move the hotend nozzle to the corner with the XY endstops and tune my Z limit switch to the height of that corner by using the standard paper thickness method and repeatedly homing the Z axis in between adjustments. I don't adjust the spring/screw assembly here.
    -Without Z homing, move the nozzle across the build plate (to all corners) and roughly adjust the build plate bed leveling screws to get a rough, but finer level so the nozzle does not impact anywhere.
    -Move the hotend back to the start and repeat the Z homing and paper thickness technique for that corner.
    -Now without Z homing, move the nozzle across the build plate (to all corners again) and finely tune the build plate bed leveling screws to get the hotend nozzle to just grab the piece of paper.
    -Double check all 4 corners and repeat adjustments if necessary (shouldn't be needed)
    -Check the center of the bed. If all four corners are good but the center of the bed isn't then you glass plate if not perfectly flat. If it is only slightly out you can compensate with a thick first layer height.
    You are good to go...
    I mentioned live tuning. I am not referring to adjusting the bed leveling screws/spring we just tuned above. What I am referring to is fine adjustments to the Z axis lead screws while the first rounds of the printer are being printed. Due to repeatably issues of the Z axis endstops in position accuracy I've found slight manual adjustment of the two lead screws in unison allows me to get the right amount of first layer squish. However, if for some reason the bed is out of level in the left/right direction then an imbalanced adjustment to the lead screws can be made to correct as well.
     
    Guilhaume likes this.
  21. Ryan W

    Ryan W New
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    Carl,

    Going over your BOM, I calculated about $400 in Openbuilds parts. Is that correct?
     
  22. Carl Feniak

    Carl Feniak Journeyman
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    I've noted multiple sources for many of the items so this question is a bit hard to answer. For example, you can purchase the power supply from the open build store, ebay, at a local electronic store, or re-purpose an old computer/xbox power supply. All have different costs and pros and cons.
    In general, I'd say $300-470 + shipping.
    Sadly I only came across V-slot a week after the kickstarter ended, but if I had contributed (and I would of) then I'd get a permanent 10% off. Alas. Worth having a chat with sales, maybe for such a large order they'd be willing to give free shipping (depending on your location) or 5% off. :) Worth an email anyway.
     
  23. Carl Feniak

    Carl Feniak Journeyman
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    Here are a couple parts you might find useful for your Z axis since you went with the 20x20. I haven't changed my printer to them, but wanted to design them for consistency with the CoreXY parts.
     

    Attached Files:

  24. Keith Davis

    Keith Davis Veteran
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    Carl, I know this is going to sound crazy, but I love the color blue for your printed objects. Where did you get it? I want to buy some.
     
  25. Carl Feniak

    Carl Feniak Journeyman
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    Bad news. This is where I had purchased it, unfortunately they just significantly reduced the colors they carry about 2-4 months ago. They no longer carry it.
    http://revolution3dprinters.com/
     
  26. nexty

    nexty New
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    hey guys, good job after
    3weeks I've received the V-slot - so I will start cutting them anysoon,

    looking for the motor,

    is those are the one suggested ? (68oz)

    Nema 17 Stepper Motor,2Phase, 68oz, 4wires

    Step Angle: 1.8 degree


    Voltage: 3.1VDC

    Current: 2.5A/phase

    Resistance: 1.25Ohm/phase

    Inductance: 1.8mH/phase

    Holding torque: 0.48N.m 68oz-in

    Rotor inertia: 68g-cm2

    Detent torque: 280 g-cm

    Number of wire leads: 4

    Weight: 0.36Kg

    Length: 48mm

    just wanted to make sure I order the correct one :)
     
  27. Carl Feniak

    Carl Feniak Journeyman
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    I thought I had 86ozin motors but I missread. They are 68ozin. My motors are: 42HS48DF02
    I am happy with these but would consider getting a larger one if you are going with a direct drive extruder in a bowden setup like mine. That said I am not having issue yet but feel I will once I start increasing my print speeds. If I do have issues I may just switch to a geared drive.

    Here is a good explanation of the numbers:
    http://www.3xmotion.com/2008/stepper_motors.pdf
    upload_2014-11-8_15-24-26.png
     
  28. nexty

    nexty New
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    what is you're current speed with you're actual printer if you don't mind asking?

    looking at that sheet, the one I was looking are pretty low, not sure if its the right motor, the goal is to print faster with high accuracy has I have already a K8200 printer at home that I'm happy with
     
  29. Carl Feniak

    Carl Feniak Journeyman
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    I am printing at 120% (x 1.2) the below. I think you will be fine with those motors for the XYZ as my motors are just warm and have no cooling at all. The extruder is quite warm at these speeds, though it is working hard with 5mm retraction. If you want to achieve 150%+ of this, I'd say just switch to a geared extruder (like a greg's wade's) so you don't risk missing steps with the higher backpressure. There are lots of designs out there.
    upload_2014-11-8_17-33-11.png
     
  30. nexty

    nexty New
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