Do CoreXY belts need to be of equal tension? April 21, 2016 02:53AM |
Registered: 9 years ago Posts: 1,035 |
Re: Do CoreXY belts need to be of equal tension? April 21, 2016 07:57AM |
Registered: 8 years ago Posts: 776 |
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realthor
Hi guysI have a bit of a dilemma here: in a corexy setup, do I have to make sure belts have the same tension on both sides?
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As far as I can tell, having them adjusted differently can help squaring the top -which is notoriously difficult to square as one can't install cross bracing in there- and also (maybe) can be used for other artifacts in prints (oval circles,etc).
Re: Do CoreXY belts need to be of equal tension? April 21, 2016 08:56AM |
Registered: 9 years ago Posts: 1,035 |
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lkcl
If the belts are tensioned differently they will have different characteristics and different effects, which will cause minor odd variations resulting in odd and unpredictable patterns, head movement... yeah. definitely.
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lkcl
the coffeetable guy [forums.reprap.org] has come up with a great way to do stiff bars without needing corner-bracing: offset bars with bolts going through
it can be done... and it is absolutely essential that you find a way, if you want decent prints.
Re: Do CoreXY belts need to be of equal tension? April 21, 2016 11:17AM |
Registered: 11 years ago Posts: 553 |
Re: Do CoreXY belts need to be of equal tension? April 21, 2016 11:22AM |
Registered: 9 years ago Posts: 1,035 |
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gmh39
You can use a single length of belt (assuming you are not using the 2 plane method), connect the ends to the x carriage, tension the belt with the motors (or really anywhere), and secure the belt to the carriage again to effectively form 2 individual belts. That should give you the same tension in each section of belt.
Re: Do CoreXY belts need to be of equal tension? April 21, 2016 11:27AM |
Registered: 11 years ago Posts: 553 |
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realthor
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gmh39
You can use a single length of belt (assuming you are not using the 2 plane method), connect the ends to the x carriage, tension the belt with the motors (or really anywhere), and secure the belt to the carriage again to effectively form 2 individual belts. That should give you the same tension in each section of belt.
I am using the 2 planes so I can't apply this method, have to find another one. Thanks for chiming in.
BTW: here's my Thingiverse 3D Printer Design: [www.thingiverse.com]
and here's a better 3D viewer @ Sketchfab: [sketchfab.com]
...Also the X Carriage I linked above, in a Sketchfab viewer: [sketchfab.com]
Re: Do CoreXY belts need to be of equal tension? April 21, 2016 12:56PM |
Registered: 11 years ago Posts: 651 |
Re: Do CoreXY belts need to be of equal tension? April 21, 2016 03:13PM |
Registered: 9 years ago Posts: 1,035 |
Re: Do CoreXY belts need to be of equal tension? April 22, 2016 09:00AM |
Registered: 8 years ago Posts: 776 |
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realthor
I find it very difficult to add a tensioning system elsewhere in the corexy path. I don't have pockets/slots in the motor mounts that would allow adjusting tension. I have designed slots for lateral adjustment so I ensure square belts for the corexy setup. Adding perpendicular slots to those is close to impossible.
[attachment 76848 ScoutCoreXY-XYSteppers_MountsAreAdjustable2.png][attachment 76849 ScoutCoreXY-XYSteppers_MountsAreAdjustable3.png]
So I have finally decided to add it straight to the X carriage. One bolt+nut is not such a weight penalty. And you have the advantage that with that single bolt+belt-gripper-slide you adjust both belts' tension.
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But I got the advice on google groups that I should be able to adjust both belts independently which is for me quite surprising.
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The fact that one can square the top plane of a corexy printer using belt tension is a happy surprise but if that brings artifacts in the print due to different tensions in the belts than it's not such a sweet deal.
Re: Do CoreXY belts need to be of equal tension? April 22, 2016 10:43AM |
Registered: 9 years ago Posts: 1,035 |
Re: Do CoreXY belts need to be of equal tension? April 23, 2016 11:09AM |
Registered: 8 years ago Posts: 776 |
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realthor
1) My setup is just like Smartrapcore regarding the belts lines. Only the side of the motor belt that goes to the Y Carriage and the side of the belt that goes from the idler to the Ycarriage need to be dead straight. The other side, the outer long belt doesn't need to be parallel with anything. It only needs to not catch on itself when the Y carriage approaches the idler. I am pretty sure I have that ok, if not else at least because Smartrapcore works.
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2) If both lengths of belt are equal and the frame is square then adjusting them independently would only make room for error (ex: different tensions in each of them due to human error, like thinking you hear the same tone when "striking the chord"
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3) I have a lot of adjusting elements, from the clamps themselves that can "slide" on the square tubing to the Y Rod hole which is larger than the diameter of the rod and fine adjustment can be done by turning the screws in the 3(or 4)-point-adjusting mechanism.
The design challenge I have now is designing a jig (3d printed + metal bushings) to drill the tubes at precise positions and at straight angles so that when fastening the frame everything comes up square.
The other challenge is developing a "procedure" to make everything straight and square.
Re: Do CoreXY belts need to be of equal tension? April 23, 2016 11:59AM |
Registered: 9 years ago Posts: 1,035 |
Re: Do CoreXY belts need to be of equal tension? April 23, 2016 12:59PM |
Registered: 8 years ago Posts: 776 |
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realthor
Yes, a bit harder, but I like that. It also gives the possibility to overcome many build errors, which I believe a DIYer with a hacksaw and a cordless drill will make. Not everybody will have factory cut aluminum extrusions and maybe they are not absolutely needed in all situations... but hey, if they are cheap enough people will not complicate their lives with ALU tubes anyway.
Regarding the dead straight lines of belt I admit they look good, but they are again not necessary. As I said, as long as the teeth don't catch on each other it's fine.
Re: Do CoreXY belts need to be of equal tension? April 23, 2016 03:15PM |
Registered: 9 years ago Posts: 1,035 |
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lkcl
let me be absolutely clear: the statement that you have made is 100% wrong. if you do not believe me, and cannot work it out in your mind that the tension in the belts will vary as the carriage goes back and forth if the belts are not directly aligned and at 90 degrees when coming out of the x-ends, then you will find out *why* this matters so much when it comes to actually trying to print.
Re: Do CoreXY belts need to be of equal tension? April 23, 2016 08:21PM |
Registered: 8 years ago Posts: 776 |
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realthor
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lkcl
let me be absolutely clear: the statement that you have made is 100% wrong. if you do not believe me, and cannot work it out in your mind that the tension in the belts will vary as the carriage goes back and forth if the belts are not directly aligned and at 90 degrees when coming out of the x-ends, then you will find out *why* this matters so much when it comes to actually trying to print.
I thought I was pretty clear that the lines of belt that come and go from the X carriage should be straight.
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That is common sense I never disputed that. I have them dead straight in my design. I am talking about the outer line, the line that goes from motor to idler... .
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If you are saying that that one should be dead straight too then I can't argue because I don't have hands-on experience but I can't see how that one would cause any change in tension.
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The system I am using is exactly this one:
Smartracore, Frax 3D and several others seem to use this design:
Re: Do CoreXY belts need to be of equal tension? April 23, 2016 11:08PM |
Registered: 9 years ago Posts: 1,035 |
Re: Do CoreXY belts need to be of equal tension? April 24, 2016 02:51AM |
Registered: 8 years ago Posts: 776 |
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realthor
OK, your concerns are valid with different builds. So, to stop linking other designs and make room for deviating the discussion, here's the Sketchfab link to my printer STL:
[sketchfab.com]
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I am in the process of moving the corexy steppers' vertical members (columns) outside to have a symmetric arrangement so I will upload a slight variation soon but this one is good enough to see what's straight, what's level, etc. I can tell you from the start that the line of belt coming/going to the X Carriage bearings are dead straight and that the bearings on X carriage, Idler and motor pulley are perfectly arranged vertically.
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Edit: btw, both motor mounts and idler mounts can be adjusted vertically by sliding them on the vertical members before tightening the square clamp on the alu tubing.
Re: Do CoreXY belts need to be of equal tension? April 24, 2016 06:08AM |
Registered: 9 years ago Posts: 1,035 |
Re: Do CoreXY belts need to be of equal tension? April 29, 2016 01:08AM |
Registered: 8 years ago Posts: 776 |
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realthor
Sometimes I wonder what link have I directed you to...or that I'm lost in translation.
I have no threaded rods, I only have belts for X, Y and Z.
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Anyways those are more difficult to spot unless I'll someday make a video about it.
Re: Do CoreXY belts need to be of equal tension? April 29, 2016 03:38AM |
Registered: 9 years ago Posts: 1,035 |
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lkcl
sorry - i don't use proprietary software (so am not going to download a file i can't edit or view... because it's proprietary), and likewise a proprietary browser plugin is required to view the model in a web browser, so i got a very unclear 2D render - from a fixed perspective - which i could not do any zoom or rotate on.
I don't dare to write in a wiki about something I haven't yet demonstrated or prototyped...soryy it might be a while until I have one.Quote
lkcl
understandable then that without any kind of specifications in the usual places (best place for which is the reprap wiki) i would assume quite a lot. sorry!
Re: Do CoreXY belts need to be of equal tension? April 29, 2016 07:14PM |
Registered: 8 years ago Posts: 776 |
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realthor
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lkcl
sorry - i don't use proprietary software (so am not going to download a file i can't edit or view... because it's proprietary), and likewise a proprietary browser plugin is required to view the model in a web browser, so i got a very unclear 2D render - from a fixed perspective - which i could not do any zoom or rotate on.
You only need a modern open source browser with OpenGL ...or something like this. I use latest Firefox, so open source too.
I don't dare to write in a wiki about something I haven't yet demonstrated or prototyped...soryy it might be a while until I have one.[/quote]Quote
lkcl
understandable then that without any kind of specifications in the usual places (best place for which is the reprap wiki) i would assume quite a lot. sorry!
Re: Do CoreXY belts need to be of equal tension? April 30, 2016 03:05AM |
Registered: 9 years ago Posts: 1,035 |
Re: Do CoreXY belts need to be of equal tension? April 30, 2016 01:32PM |
Registered: 8 years ago Posts: 776 |
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realthor
no worries, those are good points. I'll try to learn how to use the wiki and start a page for ScoutCore.I'd rather document and change a single page than cluttering the forums anyway.
it's a confusing environment to choose between instructables, github, reprap wiki, thingiverse, etc ... Is there a CoreXY category in the wiki? I might need some guidance to it :-s
BTW:: @lkcl : the sketchfab model is downloadable should you want to study it in your STL renderer of choice. Here's the download link again: [sketchfab.com]
Edit: as far as I can see, the reprap wiki is very poor with the documentation of the successful builds I am seeing on the forums (G&C, Vulcanus, FuseBox, etc ...none of these already built, tested and proven ones is there)
Re: Do CoreXY belts need to be of equal tension? April 30, 2016 02:27PM |
Registered: 9 years ago Posts: 1,035 |
Re: Do CoreXY belts need to be of equal tension? April 30, 2016 04:01PM |
Registered: 12 years ago Posts: 5,796 |
Re: Do CoreXY belts need to be of equal tension? April 30, 2016 09:25PM |
Registered: 9 years ago Posts: 1,035 |
Re: Do CoreXY belts need to be of equal tension? April 30, 2016 10:27PM |
Registered: 10 years ago Posts: 83 |
Re: Do CoreXY belts need to be of equal tension? May 03, 2016 05:15AM |
Registered: 8 years ago Posts: 776 |
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the_digital_dentist
If you start posting stuff to wikis every time you make a change to something, you'll be spending all your time posting stuff to wikis and none of it developing your project. I tend to save the documentation at the end of a project so I don't waste time documenting things that change a lot throughout the process.
Re: Do CoreXY belts need to be of equal tension? May 03, 2016 05:18AM |
Registered: 8 years ago Posts: 776 |
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realthor
Wow, I don't understand anything from there ... I'm completely unfamiliar with wikis. I'll have to do some reading.
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Edit: nice documenting there.... trying to get my head around it.
Edit: Do I need to PM an admin to open a page for me?
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How do I do it otherwise? I'll copy the code from your link and start from there.
Re: Do CoreXY belts need to be of equal tension? May 03, 2016 06:27AM |
Registered: 9 years ago Posts: 1,035 |