Calibrating Makelangelo 2 & 3

Home Forum Makelangelo Polargraph Art Robot Calibrating Makelangelo 2 & 3

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This topic contains 17 replies, has 4 voices, and was last updated by Avatar ianmcmill 5 months, 2 weeks ago.

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  • #5955
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    Anonymous

    Here’s a new picture that might explain the calibration a bit better.

    MW: Machine Width
    HW: Machine Height
    PW: Paper Width
    PH: Paper Height

    Pink cross: where pen should be when drawing starts.

    extra board at bottom: so bottles don’t hit the floor.

    #14143
    Avatar
    Anonymous

    I know this is old and hundreds of people have no doubt found this answer…. I’ve dug and I’ve looked and I haven’t found it.
    Where is the start point relative to the motor centers?
    Left-right – center between them – Ok, got it.

    Up-down? ???

    #14144
    Dan
    Dan
    Keymaster

    @Desterline – on the Makelangelo 3 and 5 draw a line between the center of both motors. From the middle of that line, go down 217mm (8.54330709 inches). That is the spot where the pen should start.

    It used to be in the center of the paper, which was crazy annoying to use on the 3. With the 5 it’s on the edge of an A2 sheet, so well placed.

    It’s not friendly for M3s that are very very big – you might not even be able to reach the home position without a ladder. I’ll see about adding a “set your own home position” option for the next release.

    #14145
    Avatar
    Anonymous

    Wow, quick response – Thank you!

    That’s kinda my problem – This is a scratch build that eventually will be on a 4’x8′ whiteboard. I need the vertical dimension as a function of the motor separation so I can scale it to a different size.

    I also need to ask some questions about installing the latest PC side host software – but that may be better asked on a different thread.

    #14146
    Dan
    Dan
    Keymaster

    If you need it, consider making the change and sending me a pull request. I’ll merge your change (after testing) and then it’ll be there for everyone.

    #14148
    Avatar
    Anonymous

    To contribute to the community here….
    I ended up getting reasonable plotting accuracy with a base leg dimension of 32.25 inches and a machine zero point 9.125 inches down from the center of the base leg.
    I was not able to find this point with math. The math lead me to a different point and I still had distortion. It’s likely I was doing the math wrong or not including all the relevant details. I was able to find the zero point without the math, so my process is probably useful to someone.
    I created a very simple DXF file with one horizontal line.
    Plot the file and observe how it is distorted. Smile face distortion means the zero point is too low, frown face is too high. Adjust, set home, repeat. Took about 5 cycles to get the distortion to be less than the tip width of my pen over ~1/2 meter span.

    #14197
    Dan
    Dan
    Keymaster
    #23108
    Avatar
    ianmcmill
    Participant

    Sorry for spamming the forum with calibration and home positions questions but is this post here still relevant or obsolete?
    Especially this answer from Dan “– on the Makelangelo 3 and 5 draw a line between the center of both motors. From the middle of that line, go down 217mm (8.54330709 inches). That is the spot where the pen should start.”
    Does this still apply? Wait I’ll just try it and report back.
    But I just realize that it took me quite some time to figure this home mechanism out. This leads me thinking that there should be a definite guide on home position and calibration. There are a lot of good informations on the forum but they are scattered around. Having them all in a single, easily reachable place would make the life of many people easier.

    #23111
    Avatar
    ianmcmill
    Participant

    Measured 210mm instead of 217mm (don’t know why I withhold the 7mm) from center of the motor shafts down on both Y axes. At this height, center of the board/center of the two motor shafts is home position. Now a horizontal line is straight from what I can tell by approximating.

    How to measure home position on a Makelangelo

    But another question arose from this. The Makelangelo 5 leads the GT2 belt (with the end towards the pen holder) past one of the mountings for the stepper motor. So the angle of the belt is offset by this mounting (the white long thing in which the screw mounts the stepper motor to the board). Do I need to take account for this when I don’t guide the belt this way? Or am I think to much about this?

    #23113
    Dan
    Dan
    Keymaster

    I don’t have a first time guide for makelangelo 3 users. Can I use your picture when I build the guide?

    Here are the existing guides:
    https://mcr.dozuki.com/c/User_Guides

    #23114
    Dan
    Dan
    Keymaster

    As for the leading… I’m glad someone else thinks about this! 😃 I imagine that it does make a difference and I have never com up with a good solution. Without the corner the belt length calculation gets really hairy. With the corner it easier until near the very bottom corners. In those cases I fudge the result. I need to make a video to explain the whole thing. I bet you get what I mean. There’s probably a way to lock the angle down and then the width would be between each “lock”. As it stands I go Center to center of each motor for width.

    #23115
    Avatar
    ianmcmill
    Participant

    Hey Dan, sure you can use the picture. I could make more if you guide me on what you want to see in them. I have no clue on kinematics math and the polargraph mechanism is more like voodoo to me. Though my trigonometry sensor where tingeling. The polargraph by euphy doesn’t have such corner guides. And from user posted pictures of really large polargraphs that do technical drawings like “the one” with the motorcycle drawing which looks really precise, I am not sure how much this corner adds to the belt length calculation.

    TL;DR looking at large scale polargraphed technical drawings on the internet from various different polargraphs, I guess the corner-thing doesn’t really matter.

    #23117
    Dan
    Dan
    Keymaster

    Yeah… it might not mean much, but when I’m in a mood to care about precision (often) it feels wrong.

    #23119
    Avatar
    ianmcmill
    Participant

    I know what you mean.

    #23120
    Dan
    Dan
    Keymaster

    so… why did you go with 210 instead of 217?

    #23125
    Avatar
    ianmcmill
    Participant

    oh I simply remembered it wrong 🙂

    View post on imgur.com

    View post on imgur.com

    The gondola is too light. I haven’t attached a weight. It was just a short test.

    View post on imgur.com

    #23126
    Dan
    Dan
    Keymaster

    Yeah, and that unfinished ply is rough AF. Try a sheet of acrylic or something with a laminated surface.

    #23130
    Avatar
    ianmcmill
    Participant

    You’re right. I had a 500x700mm paper on it but removed it and I was too lazy to apply a new one. The tip of the pen scamper across the ply surface but I just wanted to test the movement.

    Another issue. Might become off-topic.
    The board I am using is 1 inch tick and very heavy (around 20kg). The motors are directly screwed to the board running with DRV8825 in 32th MS. The board acts as a giant resonator. It is pretty loud. I thought about something to reduce noise. I guess there are these options:
    1. Screw the motors to a 10x100mm board and attach this board on top of the drawing board. Then I need to think about how to fix the motor-board to the drawing board so that I can easily use it on any board that I come across. But I am lazy. Soooo next option:
    2. Build some silicone dampers from 3d printed molds. Let a machine do the hard work. Good one.
    3. Buy a lightweight drawing board. Even more suitable for lazy persons :)…
    4. Does reducing micro steps reduce the resulting resonator noise? I know that stepper drivers have a great impact on motor noise. Probably TMC drivers are the most quiet. But I think the attached board has a greater influence on noise. This would be the most cost efficient method + less time consuming. Did I say that I am lazy 😉

    I need to test this.

    As the Makelangelo uses thinner and leightweight plywood I guess getting a “better” board should be the first step.

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