My V-King Pro 3d (with belt driven z)



  • After having built a HEVO, and always struggling with the lead screws (somehow the ones I got were always bent) I went looking for something else and stumbled upon the V-King: https://github.com/RoyBerntsenDesign/V-King

    I liked the idea of a belted z, and went ahead and built one. I like the simple approach, most extrusions are 500mm. You can buy a kit from ratrig with 12x500mm extrusions, and then you just need some more extrusions for the bed frame (another 4x500mm) and x-axis (480mm). In standard config you get about 340x390 build volume. With the worm gear setup, the bed doesn't drop when power is off.

    I first built the original frame and used it. After a few months of use, I decided to do some small modifications: I replaced the openbuilds corners (didn't like m) with 3-way brackets from ebay and added a second z-motor setup. My build volume is now app 340x340 and each corner of the z axis is driven by a belt. I could easliy add an extra one or two z motors and have automatic bed levelling.

    Further details:

    • Duet Wifi
    • 0.9 steppers on x and y
    • Bondtech extruder with capricorn bowden
    • E3d Chimera+
    • Gates belts on x and y
    • Minimal use of cloned parts

    Below is a pic of the build, and a pic of the first print after the rebuild.

    0_1533553312907_IMG_20180805_123828_1.jpg
    0_1533553423743_IMG_20180805_094637_1.jpg


  • administrators

    Looks good! The 4-leadscrews 4 belts driven by a single motor is a good solution, if you have bed-leveling screws or some other way to get the bed level, and a frame rigid enough to ensure that it stays that way.

    Do you have problems with the bed dropping under its own weight when the machine is powered down?



  • @dc42 said in My V-King Pro 3d (with belt driven z):

    Looks good! The 4-leadscrews driven by a single motor is a good solution, if you have bed-leveling screws or some other way to get the bed level, and a frame rigid enough to ensure that it stays that way.

    Do you have problems with the bed dropping under its own weight when the machine is powered down?

    This printer doesn't have leadscrews. It does have bed levelling screws and those work fine. I like the possibility of three or four independant z motors, but that would require a Duex5.

    The bed does not drop at all when powered down. Not even if I try to push it down.



  • @bartolomeus How is the Z axis geared? I see the motor at the back and the shaft coming out at 90 degrees... Is that a printed gearbox? What's inside it?

    I use a belt lifted Z axis, too. It uses an OnDrives Rino 30:1 worm gear reducer. I tried making a printed gearbox to use a cheap Chinese worm gear set, but had problems with the gear quality making it unsuitable for use in a 3D printer without some firmware mods to correct cyclic errors in print layer thickness.



  • @mrehorstdmd said in My V-King Pro 3d (with belt driven z):

    @bartolomeus How is the bed geared? I see the motor at the back and the shaft coming out at 90 degrees... Is that a printed gearbox? What's inside it?

    It's a worm gear and a toothed gear. Gear reduction is 20:1 (or 1:20 ,not sure, anayway steps/mm is 1600). They are mounted in a printed 'gear box' and connected the an opposite wide with a 5mm rod. The belt itself rides on a standard 20t pulley.



  • @bartolomeus What gears did you use?





  • @mrehorstdmd said in My V-King Pro 3d (with belt driven z):

    @bartolomeus
    I use a belt lifted Z axis, too. It uses an OnDrives Rino 30:1 worm gear reducer. I tried making a printed gearbox to use a cheap Chinese worm gear set, but had problems with the gear quality making it unsuitable for use in a 3D printer without some firmware mods to correct cyclic errors in print layer thickness.

    Ah! I read your article. After the rebuild, I haven't printed something with which I can check. Although, personally I really like the surface of the calibration cube in the pic in the first post.



  • @bartolomeus The gear box I tried to build used some much larger and apparently poorer quality gears from China. I'll have to order a set of your gears and give them a try. 20:1 might be a little low for the mass I have to lift and keep from dropping but it will be worth a try. Thanks! Did the gears' dimensions match the drawing?

    Can you post a photo of your gearbox?



  • Just out of curiosity guys, but what if anything does a belt driven Z axis give you vs say 3 fine pitch single start screws driven by a single motor?



  • @deckingman For me it's personal preference. I could not find high quality lead screws for my HEVO, and the ones from china were mostly bent. Also, for me, this frame with belts is easier to assemble, easier to align, it uses less/ smaller printed parts. It also makes it easier to build with mainly genuine parts, instead of cheap lead screws and cheap linear bearings.

    @mrehorstdmd Heres a pic of the gearbox. It isn't MY gearbox, I didn't design it.

    0_1533576860760_IMG_20180806_192631.jpg



  • @deckingman Belts don't come bent, so they don't cause Z wobble. I know, if you use decent quality parts and build everything correctly, Z wobble isn't a problem with screws, but the vast majority of printers are built neither correctly nor using quality parts. Since belts don't create lateral forces that cause the bed to wobble, a belt lifted Z axis should work with 8mm end-supported guide rails that would flex like wet noodles with bent lead screws (though vibrations might still cause the bed to shake). Belts are a lot cheaper than screws, and can be set up for arbitrary lengths.

    Belt lifted Z axis designs benefit from worm gear reducers that increase resolution, multiply motor torque, and stop the bed from dropping when motor power is cut. Print quality depends on the quality of the gears used as flaws will repeat with every rev of the worm and disc gears.

    By the time you add the cost of a worm gear reducer and the belts and pulleys, using a belt drive for the Z axis may not be any cheaper than using screws. I have about $140 in the worm gear reducer and shaft in my printer, so it might have been cheaper to use screws instead of belts. That's why I've been looking to make a worm drive unit using cheap gears. The one I made was about $40 all-in to replace that $140 Rino (surplus price $108, new price $850) and its shaft, so would make belt lifted Z axes much more practical.



  • Thanks guys - I'll stick with my (unconstrained) screws though.



  • If you always got leadscrews that were bent, why did you not just straighten them, it's a very simple thing to do.



  • @calvinx said in My V-King Pro 3d (with belt driven z):

    If you always got leadscrews that were bent, why did you not just straighten them, it's a very simple thing to do.

    ,.....and if the screws only provide lift (the job they are supposed to do) and aren't constrained, they won't fight with the guides and cause issues, even if they are (slightly) bent. I know this from experience after a bit of an accident ( replacement screw is on its way but the prints with one bent screw are coming out just fine)



  • @deckingman I am not saying one solution is better than the other. I just like this setup and it's working very well for me.



  • @bartolomeus yes that's fine. Each to there own. I was responding to other comments about bent screws. I don't see anything wrong with your belt driven z axis, equally I don't have a problem with my screw driven one. Two different ways to achieve the same thing, neither of which is better or worse than the other IMO.



  • @mrehorstdmd Have you ever considered a 3d printed worm gear? Would it be strong enough and more precise than a cheap metal worm gear?



  • @bartolomeus No. I'm not a fan of printed gears, especially not where precision and accuracy are needed. 3D printing can do a lot of stuff, but it can't do everything.



  • @mrehorstdmd How about using mod.8 gears vs mod1? (https://kyouikugearjapan.trustpass.alibaba.com/product/50026277888-230595559/Worm_gear_shaft_Module_0_8_Stainless_steel_Made_in_Japan_KG_STOCK_GEARS.html?spm=a2700.icbuShop.prewdfa4cf.1.134a236dhzD8e3)

    I am very happy with my print quality, but I think thre is room for improvement. That's why I'm looking for higher quality gears. There are a few, bust most with 6mm bore shaft. These are about the only one I could find with 5mm bore.


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