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TrueUp Kit Version

Discussion in '3D printers' started by Keith Davis, Mar 24, 2017.

  1. Keith Davis

    Keith Davis Veteran
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    The belt does not connect to the y idler, it wraps around the idler and the pulley. The belt connects to the anchor screw in the center of the build plate. TrueUp Glide Build Plate Assembly
     
  2. GeoMetJosh

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    Oh dear, I asked the wrong question XD. I am a little confused how to attach the y-belt to the anchor screw. I took photographs of how I attached it. Did I do it correctly?
    20170418_164820[1].jpg 20170418_164812[1].jpg
     
  3. Keith Davis

    Keith Davis Veteran
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    Wrong. No need to wrap the belt around the anchor screw. Just lash the belt to the screw as it passes by the screw. It's not going to slip if the zip tie is tight. By wrapping the belt you have shortened it's overall length, which you do not want.
     
  4. GeoMetJosh

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    Ok, so I tried again. Just lashing it against the belt seems to twist it somewhat. Is this correct? 20170418_175839[1].jpg 20170418_175823[1].jpg
     
  5. Keith Davis

    Keith Davis Veteran
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    Wrong again, sort of. You have the belt teeth against the anchor screw - that is correct. But, the connection of the zip needs to be on the other side of the screw so it is between the two strands of the belt. As you have it, that connector will drag on the side walls of the Y rails. That "kink" is immaterial.
     
  6. GeoMetJosh

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    OK, I think I got it this time. I thought I would upload a final pictures 20170419_120026.jpg 20170419_120049.jpg , in case it helps anyone.
     
  7. Keith Davis

    Keith Davis Veteran
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  8. GeoMetJosh

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    So to get perfect holes for the Z Uprights and Y Rails for the first step (TrueUp Glide Frame Assembly) I created some jigs. All you do is attach the jig to the rail using the tapped center hole and a M5 screw and M5 slide t-nuts. Then you drill the holes with a 5mm drill bit.

    Here is a picture of one set up. Note that you also screw an M5 screw into the threaded rail. I don't currently have a rail that has been threaded, so I wasn't able to attach one in these pictures 20170419_125307[1].jpg .
     

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    #38 GeoMetJosh, Apr 19, 2017
    Last edited: Apr 19, 2017
  9. GeoMetJosh

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    I also created a two jigs for the MK3 build plate. First you attach jig one to the MK3 build plate using M3 screws. Then you drill out the 4mm, 5mm, and 7mm holes. Then you remove jig 1 and attach jig 2 to the plate with a M5 screw in the 5mm whole and a M7 screw or M7 drill bit. Then you drill the 5mm hole, add another M5 screw to secure the jig, then drill the last 7mm screw.

    Note you will need a fairly large printer to make these jigs. If anyone wants I can try breaking them down into smaller prints. Enjoy!
     

    Attached Files:

    #39 GeoMetJosh, Apr 19, 2017
    Last edited: Apr 19, 2017
  10. Keith Davis

    Keith Davis Veteran
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    Thanks!!

    I've spit the long one and rotated two of them and included all of them (rail & plate jigs) in the "extra" folder in the STL zip

    http://3dwrx.com/TrueUp/kit-stl.zip
     
  11. Elmo Clarity

    Elmo Clarity Journeyman
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    Keith, In the kit assembly guide, there is very little information about the Z End Stop screw other than to thread it in. There is no information as to how long the screw is suppose to be, if a nut is embedded into the guide, or any information on the knobs. Is there a link somewhere with that information? I checked out the TrueUp instructions and it didn't say much there either.
     
  12. Keith Davis

    Keith Davis Veteran
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    The assembly manual is for assembling a kit that I ship. I ship that part already assembled.

    So, here's why I ship it assembled - it has to be done right. First, take that long screw, put a 3mm washer on it, stuff it through the bracket hole, top to bottom. Put a M3 nylon lock nut on it and tap the nut into the cavity to start it. then suck that nut all the way in with the screw. It has to be sucked in tight. Remove the screw. Now put the screw through the colored wheel, another M3 nylon lock nut, and again suck that nut all the way in with the screw, It too has to be tight. Then add a regular m3 nut to the screw as a jab nut and run it tight against that nylon nut. Prepare the lock wheel by embedding a M3 screw in it's cavity. Point that srcew UP and thread that lock wheel onto the long screw about 1/4" from the colored wheel. Now run the screw back through the bracket hole, top to bottom. It's ready.
     
  13. Elmo Clarity

    Elmo Clarity Journeyman
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    Are there STL files for the parts other than the glide?
     
  14. Elmo Clarity

    Elmo Clarity Journeyman
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    I would appear that my printer made the hole for the nut just a little bit too big. Can only get it to spin around in the hole. Will have to try reprinting the part.
     
  15. Keith Davis

    Keith Davis Veteran
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  16. Elmo Clarity

    Elmo Clarity Journeyman
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    Must have over looked them. Will go back and check again. Thanks.
     
  17. Hedgehog

    Hedgehog New
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    I wonder if an eye bolt and j-bolt attached to it aren't a better option to fix the timing belt?
     
  18. Elmo Clarity

    Elmo Clarity Journeyman
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    For my build, I designed a belt clamp to use so I didn't have to use a closed loop belt.

    Y Axis Belt Clamp.png
     

    Attached Files:

  19. GeoMetJosh

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    So my x-axis and y-axis are working great. However, I am having a very hard time getting the z-axis to work properly. When I home the z-axis, the nozzle comes down towards the bed for the fast home, than does a weird bobbing motion (backlash?) as it proceeds with the slow home. Has anyone else seen this behavior? Unfortunately, this messes up the first couple layers as the nozzle doesn't actually rise for the first few layers. After the first few layers, it seems to work OK. I have recorded a video of the behavior below, its a little hard to see but the nozzle makes a strange circular motion.
     
  20. Keith Davis

    Keith Davis Veteran
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    It looks to me that you might have play between the bushings and the glide body cavity walls (front and back) that the bushing fits in. The first glide files for this had straight walls in the cavity and bushing so they had to be printed just exactly right to remove any play. Even the slightest play between those walls will result in that bobbing action. Later glide files have a slight taper to the cavity walls and the bushing sides so you can just push the bushing down until it wedge-seats against the walls. The way to know if you printed the ones that are tapered is the bushings have a notch at their bottom.

    [​IMG]

    Look at your glide file's bushings. If the bushing does not have that notch, you need to reprint and replace both glide bodies and 4 bushings.

    Later glide files also have a fake nut (no threads) for each Z axis screw After seating the nylon nut up into the body nut cavity push the fake nut up against the nylon nut and tighten the set screw against that fake nut. This prevents the nylon nut from any movement if your nut cavity and nut are not a press fit. Any play between nylon nut and the nut cavity can also contribute to bobbing.
     
  21. loglow

    loglow New
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    Some notes regarding these: I printed my tapered glide bushings slightly wide, then sanded them down for a perfect fit with no play. Also, I used an M5 drill bit in a tap holder to create small indentations in the back-center of each bushing. These little notches for the set screw prevent the bushing from slipping up or down relative to the glide body.
     
  22. Alessandro Parisi

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    Good printer... I like it!

    A question for Keith Davis: if I want to change the heated bed with an MK2 314x214mm alluminium type (and place it in landscape mode) what I have to change in your project?

    I think:
    - enlarge the X profile frame parts to contain the 314mm length bed
    - change the closed belt size (what's the new length??)
    - change the support plate to something else (advice??)
    - I don't know if I need to change some firmware parameters (bed size)
     
  23. Keith Davis

    Keith Davis Veteran
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    Add 100mm to the 20x60x250, 20x20x250, 20x20x300
    Add 200mm to the X & Z belts (the Z must be a close loop, the X can be open end)
    Get two of your MK2 314x214mm alluminium type, use one for the build plate and one for the heatbed. When drilling wheel holes in the build plate, drill down on the element side to exit on the bare side or else the exiting drill bit will snag the traces and make a horrid mess.
    No need for firmware changes, just change bed size in Slic3r & Repetier.

    All of my workshop TrueUps are MK2 314x214mm PCB heat beds, BUT, I do mine portrait mode. That way all I do is add 100mm to the Y rails and 200mm to the Y belt. I use a 214x214 build plate. My 214x314 PCB has 214x214 mount holes as well as the 214x314 mount holes. So I just mount the PCB so the extra 100mm hangs off the back of the build plate. Since I binder a mirror to the heat bed to print on, adjusting the rear mount screws adjusts the rear of the 314mm heat bed too. It's cheap, easy, and was a conversion, not a design

    [​IMG]
     
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  24. Alessandro Parisi

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    Thanks for your advice, I'm consider to modify my printer as yours.

    I've another question:

    I see the gear ratio for Z screw (16:20) 20 teeth pulley and 16 for motor, and I read your explain about the microstepping for Z and the resolution of 0.05mm. Can you explain me the connection between gears ratio and microstepping remove (full step)?? I don't understand very much.

    In my project I've 20teeth GT2 pulleys for both screws (trapezoidal T8x2) and motor
     
  25. Keith Davis

    Keith Davis Veteran
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    What is important is the pitch of your screw. Pitch is how far a nut will move on one revolution. We want a full 1mm, or even 2mm, travel per revolution. If it moves 1mm per revolution then one revolution of the motor will equal 1mm. And, each of the motor's 200 steps will move 0.005mm. If your pitch is 2mm then each step moves 0.010. Both are acceptable for a Z axis.

    Since a M8 threaded rod has a 1.25mm pitch, we need to gear it down to where one revolution of the motor produces 1mm of travel. 1.25 / 5 = .25. .25 X 4 = 1. So we need a 4/5 ratio and a 16/20 tooth pulley match does that. If your T8x2 screw has a 2mm pitch, you do not need to gear any change, you will have a 0.01 travel per motor step no matter what pulleys you use if they are matched.

    The reason behind this is you never want to use microstepping for a Z axis. Microstepping is terribly inaccurate, it was developed for smooth movement, not positioning. Unlike steps, mIcrosteps are not real positions in a motor, they are merely current fluctuations. On a Z axis a motor is likely to jump to the next full step instead of stop on a microstep. By having a 0.01 or 0.005 travel you can set layer heights in those minute graduations, ensured that it'll move by full steps only. If you needed to set a layer height at 2.75 you'd get 2.75 layers. If you are moving by microsteps because your pitch is not an even step pitch, you would get .full step layers instead of 2.75 layers. This is not theoretical, you can print 100 layers and measure the difference.
     
    #55 Keith Davis, Apr 27, 2017
    Last edited: Apr 27, 2017
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  26. Alessandro Parisi

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    That's all clear now, so on MKS Gen I need to set a "1 Full Step" for the Z motor using the jumpers under driver!
    Now in Italy it late night.. go to sleep :) tomorrow I'll get much more reading...

    Thanks so much!!
     
  27. Elmo Clarity

    Elmo Clarity Journeyman
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    So in regards to the Z steps and using a lead screw. A lot of the screws, like the ones from OpenBuilds, are 2mm screw pitch, but that is the distance from one groove to the next. Because the screw has 4 starts, there are 4 separate grooves. So one rotation of the screw would move the nut 8mm. So, with 1:1 on the gears, one rotation of the motor would be 8mm on the Z axis. So 8mm / 200 steps = 0.04mm per step. Is that math correct?

    [​IMG]

    I am using a 20T pulley on the motor and 40T ones on the screw giving me a 2:1 ratio meaning my steps would be 0.02mm. From what you said, that is too large of a step?

    And does it matter if the driver uses microsteps to get to the full step location?
     
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  28. Keith Davis

    Keith Davis Veteran
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    No, I use 1/8 step on Z. On MKS-Gen that's two jumpers for a A4988 driver. You could use 1/32 microsteps even. Again, the microsteps are for smooth movement, not positioning. 1/32 will give practically silent movement, but 1/3 runs at a fraction of the current needed for turning the screws so your voltage would need to be really hot. 1/8 has plenty of current and still smooth motion for a Z axis.

    But what is important is that the pitch and layer resolution are equal to full steps.If pitch and layer resolution are both equal to full steps, then you are starting and stopping on a full step. It then doesn't matter how many microsteps you use to get from point A to point B, what matters is that you are moving from full step position A to full step position B, not A to B plus some fraction that could only be reached by a microstep (B.03).
     
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  29. loglow

    loglow New
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    EDIT: Hah. Keith, you literally answered my question while I was asking it! Thanks. (Summary: I didn't realize that using microsteps to get from one full step to the next was just as accurate as using full steps, only smoother, and therefore preferable).

    This explanation makes sense, but why does your assembly guide indicate 3 jumpers (for 1/16 microstepping) under the Z driver, as opposed to no jumpers (full step)? Also, why does your firmware configuration have 1600 for the Z axis steps/mm (shouldn't this be 3200 for 1/16 microstepping)?

    On my current build (using M8 rod for the Z axis & 4:5 gearing) 3 jumpers (1/16) & 3200 steps/mm in firmware is producing the expected motion distances.

    Are you suggesting that it would be preferable to switch to no jumpers (full stepping) & 200 steps/mm in firmware? If so, would you expect this to require a change to that driver's current trimpot setting?
     
    #59 loglow, Apr 27, 2017
    Last edited: Apr 27, 2017
  30. Alessandro Parisi

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    That's true, my lead screw is T8x2 start 4 also, so each entire revolution moves the nut of 8mm.
    With my actual configuration is 1:1 (20T - 20T) what I need to config for driver step? Better to change pulley (and closed belt too) or setting different driver divider?
     

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