Corexy belt path question I am working on modding/creating a Corexy. I have read about the corexy kinematcs, but I am not sure I really understand all of it. Anyway, I am thinking to modify the belt path to look like the drawing below. The standard belt path is blue and red. I am wanting to modify the red path and the blue path both to move just the motors. They would then follow the purple path. There would still be 2 belts, it is just the positioning of the motors I am wanting to move. The plane of the belt path would not change, just the x,y positioning of the motors. Since the belts new red and blue belts would be the same length would the corexy motion still function properly? Sorry for the crude diagram, I just did this quickly in paint. mod_embed_images_loadimage('60de2987a6240d92b79fbdc5caf2b1e0', '/forum/thumbcache/026/6ab/ca9/993/4fb/217/3e2/a3d/65b/2c4/82_800x400.png', 'http://forums.reprap.org/file.php?397,file=91140,filename=newbeltpath.png', 'https://reprap.org/forum/addon.php?397,module=embed_images,check_scaling=1,url=http%3A%2F%2Fforums.reprap.org%2Ffile.php%3F397%2Cfile%3D91140%2Cfilename%3Dnewbeltpath.png', '', 751298, 800, 400, 'Loading image ...', false); https://reprap.org/forum/read.php?397,751298,751298#msg-751298 Sun, 15 Mar 2026 22:55:14 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?397,751298,882453#msg-882453 Re: Corexy belt path question https://reprap.org/forum/read.php?397,751298,882453#msg-882453
I built a cable drive corexy mechanism for the first generation of my sand table and eventually gave up on the cable and went to stacked belt drive.

Here's a motor mount that maintains a constant angle winding and unwinding from the drive pulley:



Video of the operation here: [vimeo.com]

More details here: [drmrehorst.blogspot.com]
]]> the_digital_dentist CoreXY Machines Sun, 14 Mar 2021 21:38:11 -0400 https://reprap.org/forum/read.php?397,751298,881681#msg-881681 Re: Corexy belt path question https://reprap.org/forum/read.php?397,751298,881681#msg-881681 shanehooper CoreXY Machines Thu, 18 Feb 2021 20:00:10 -0500 https://reprap.org/forum/read.php?397,751298,751608#msg-751608 Re: Corexy belt path question https://reprap.org/forum/read.php?397,751298,751608#msg-751608
Quote
sigxcpu
@o_lampe: I would really like a software feature that creates belt lengths out of thin air :)

Jaaa, I was focused on the sin/cos problem too much.. 8-)]]> o_lampe CoreXY Machines Sun, 26 Feb 2017 02:43:09 -0500 https://reprap.org/forum/read.php?397,751298,751515#msg-751515 Re: Corexy belt path question https://reprap.org/forum/read.php?397,751298,751515#msg-751515 sigxcpu CoreXY Machines Sat, 25 Feb 2017 13:59:42 -0500 https://reprap.org/forum/read.php?397,751298,751447#msg-751447 Re: Corexy belt path question https://reprap.org/forum/read.php?397,751298,751447#msg-751447
I have been using twists in the X and Y belts in my Cartesian printer and it has never caused problems. The important thing is that the length of the twisted section is constant, otherwise the twist will cause the belt tension to vary. Belt teeth running over plain idlers cause the belt to vibrate.]]> dc42 CoreXY Machines Sat, 25 Feb 2017 08:06:36 -0500 https://reprap.org/forum/read.php?397,751298,751411#msg-751411 Re: Corexy belt path question https://reprap.org/forum/read.php?397,751298,751411#msg-751411 stepper position offset correction in firmware. Much like probe offset.
32bit controllers would be able to handle the extra CPU load.]]> o_lampe CoreXY Machines Sat, 25 Feb 2017 04:13:40 -0500 https://reprap.org/forum/read.php?397,751298,751402#msg-751402 Re: Corexy belt path question https://reprap.org/forum/read.php?397,751298,751402#msg-751402 n9jcv CoreXY Machines Sat, 25 Feb 2017 03:00:37 -0500 https://reprap.org/forum/read.php?397,751298,751398#msg-751398 Re: Corexy belt path question https://reprap.org/forum/read.php?397,751298,751398#msg-751398
Another way to look at it:
- the movement axis is a side of a triangle S1
- the belt is the hypotenuse of the triangle I
- the distance from the motor shaft to the movement path is the other side of the triangle and it is constant. S2
- the belt angle between S2 and I (at motor shaft) is A

The length of the Y axis should be S1 = I but in your drawing it is S1 = I * sin(A). So, to have S1 = I, sin(A) should be 1, therefore A should be 90 degrees.

[attachment 91158 corexy.jpg]]]> sigxcpu CoreXY Machines Sat, 25 Feb 2017 02:43:34 -0500 https://reprap.org/forum/read.php?397,751298,751392#msg-751392 Re: Corexy belt path question https://reprap.org/forum/read.php?397,751298,751392#msg-751392
1) I am just taking some/most of this from FB2020 corexy design. It shows a twist in the belts. On an I3 and on a delta I ran the ribbed belts on 625 bearings, and never had a problem with the ribs on the bearings. Never needed to twist a belt to get the flat side of the belt on the pulley. So can the same be done with corexy, even though there are more pulleys? If so then a twist would not be necessary. I also like the idea of NOT twisting the belt. So any opinions on if the diagram without a twist would work properly?

2) I am certain you are right about the motor placement, but I can not reconcile why? Just moving the motors to the purple position, if the motor moves the belt 1mm, then the carriage would still move 1mm - sure the belt is longer and you have to ensure your Y rods and Y carriages do not get pulled to the side, but if that is designed correctly, then why would this not work. I am sure I am missing something, and I am NOT an engineer, only a tinkerer LOL. I am just trying to understand this point better.]]> n9jcv CoreXY Machines Sat, 25 Feb 2017 00:53:59 -0500 https://reprap.org/forum/read.php?397,751298,751389#msg-751389 Re: Corexy belt path question https://reprap.org/forum/read.php?397,751298,751389#msg-751389 the_digital_dentist CoreXY Machines Sat, 25 Feb 2017 00:06:53 -0500 https://reprap.org/forum/read.php?397,751298,751379#msg-751379 Re: Corexy belt path question https://reprap.org/forum/read.php?397,751298,751379#msg-751379 prot0typ1cal CoreXY Machines Fri, 24 Feb 2017 21:33:40 -0500 https://reprap.org/forum/read.php?397,751298,751301#msg-751301 Re: Corexy belt path question https://reprap.org/forum/read.php?397,751298,751301#msg-751301 Ryan_M CoreXY Machines Fri, 24 Feb 2017 12:19:57 -0500 https://reprap.org/forum/read.php?397,751298,751298#msg-751298 Corexy belt path question https://reprap.org/forum/read.php?397,751298,751298#msg-751298
Sorry for the crude diagram, I just did this quickly in paint.


]]> n9jcv CoreXY Machines Fri, 24 Feb 2017 12:07:18 -0500