Making a large CoreXY printer Hello, last year I decided I wanted to try to get into 3d printing as a hobby. I started with a Prusa i3 and after a couple months I felt the need to have a larger printer. What I want to print requires a 30cm x 50cm print bed and I felt like I would get the most satisfaction out of making my own printer. I started out thinking I could just scale up a hypercube, but I found out the hard way that it didn't scale up very well. I currently have 2sqft sheet of 1/4 mic6 aluminum for a print bed sitting in a frame measuring 26" x 32" x 50" and am in the process of trial and error in making it all work. The frame is made mostly out of 2020 extrusion, and will be wrapped in wood. I was worried about the strength of the 2020, but it all feels fairly stiff when I bolt on the sides. I had problems with the frame twisting causing the x axis to bind up, but that seems to have been resolved after attaching the wood. I am at a point where I think I need help with my printer as I have spent more on this than I had originally hoped to. My current biggest problem is with the z axis. I had two 1620 ball screws centered on the sides with 10mm rods/linear bearings at each corner. This rocked back and forth too much so I had to scrap it. I do not have any room at the front or back of the print bed for a third ball screw and don't really want to have two on one side as I had a hard enough time finding a belt long enough for the two I have now. I have switched over to having the ball screws at opposing corners with hopes that that will minimize the rocking. It seems like I will have to make the z axis very rigid and with that I am curious if my drive setup for the z axis will be strong enough to move all the weight. I have a single nema 17, 92oz.in stepper with a 16 tooth pulley driving 40 tooth pulleys on the 1620 ball screws. Will that be enough to move what will probably be 20-25lbs without any print? I am also worried about the X/Y setup, I have abandoned the hypercube design and have moved onto mgn12 linear rails. I started to work on designing my own X/Y, but I am concerned that there are odd problems that may come up due to the size. In my initial testing (no belts) I found that PETG flexes too much for my liking and have a roll of carbon fiber PETG. I also have worries about the belt, and how I might keep adequate tension without creating new problems. Are there any decent setups that I could use with my current 2020 extrusion and mgn12 rails? I am getting a little tired of the trial and error stage I seem to be stuck in. [img]https://i.imgur.com/w7af6C6.jpg[/img] https://reprap.org/forum/read.php?397,817215,817215#msg-817215 Tue, 08 Sep 2026 09:06:40 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?397,817215,853050#msg-853050 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,853050#msg-853050
Amazon 2220 GT2 belt]]> gmedlicott CoreXY Machines Mon, 13 May 2019 02:20:01 -0400 https://reprap.org/forum/read.php?397,817215,839714#msg-839714 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,839714#msg-839714





]]> DickH CoreXY Machines Mon, 26 Nov 2018 16:49:31 -0500 https://reprap.org/forum/read.php?397,817215,834745#msg-834745 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,834745#msg-834745
Also, the Amazon vendor 'FidgetFidget' has a dropdown list of all the common sizes of belts, looks like 1524mm is the max.]]> gmedlicott CoreXY Machines Wed, 26 Sep 2018 16:01:08 -0400 https://reprap.org/forum/read.php?397,817215,833929#msg-833929 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,833929#msg-833929 DickH CoreXY Machines Mon, 17 Sep 2018 21:54:17 -0400 https://reprap.org/forum/read.php?397,817215,832623#msg-832623 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,832623#msg-832623 dual roller trick helps against racking.
IMHO you could live with a single ballscrew and a cantilevered bed with that gimmick at both sides of the bed.

Video]]> o_lampe CoreXY Machines Sun, 02 Sep 2018 02:49:45 -0400 https://reprap.org/forum/read.php?397,817215,832611#msg-832611 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,832611#msg-832611
I am now back to messing with the Z axis, I am just unhappy with everything I have tried so far. I want to say that the 10mm rods I am using are just undersized for what I want, but at this point I don't really feel like buying more stuff again. At the moment I am trying two 10mm rods with longer linear bearings on the outside with a 1620 ballscrew in the middle. This setup is mimicked for each side. The problem I have with this is that I can get this to rock up and down a couple degrees and I think it is due to some flex/give in the 10mm rods. This does take a little bit of force, maybe more than the weight of anything I would print. I have not tried coupling the left and right sides together to see how hard it would be to move, maybe it would be fine. I intend to make a 2020 frame to couple everything together, with a 1/2" thick piece of MDF attached for added rigidity. This is all getting pretty heavy for the z axis, easily 30lbs of weight. On the topic of weight, I am realizing that this printer is going to end up weighing ~200lbs by the time I am done.]]> DickH CoreXY Machines Sat, 01 Sep 2018 18:15:03 -0400 https://reprap.org/forum/read.php?397,817215,831339#msg-831339 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831339#msg-831339
P.S. drilling is NOT boring ;-)]]> JoergS5 CoreXY Machines Thu, 16 Aug 2018 01:29:55 -0400 https://reprap.org/forum/read.php?397,817215,831335#msg-831335 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831335#msg-831335
Quote

I have problems boring exact holes in aluminium...

@Joerg
boring = langweilig
drilling ( holes ) = Löcher bohren
:)

Schönen Tag noch
Olaf]]> o_lampe CoreXY Machines Thu, 16 Aug 2018 00:31:57 -0400 https://reprap.org/forum/read.php?397,817215,831319#msg-831319 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831319#msg-831319
Sorry, I was not observing enough. And he uses small pulleys, which supports your words.]]> JoergS5 CoreXY Machines Wed, 15 Aug 2018 14:19:01 -0400 https://reprap.org/forum/read.php?397,817215,831318#msg-831318 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831318#msg-831318 Let's say you manage to print at 800 mm/sec. In a small machine the extruder is going to be putting hot plastic on top of hot plastic, so even if the extruder can keep up with the acceleration/speed, the resulting print is going to be poor quality.

The problem with big bearings for pulleys is the mass. Every time the belt moves, you have to spin the mass of the pulleys, too, and 4 of them plus their 12 mm axles will be on the moving Y axis.]]> the_digital_dentist CoreXY Machines Wed, 15 Aug 2018 14:12:50 -0400 https://reprap.org/forum/read.php?397,817215,831317#msg-831317 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831317#msg-831317 Edit: ok, I checked the video again: the speed test is without extruding :-)

I found a ball bearing fitting could be a 6301: 12x37x12, so you need only one at each place, even with 9 mm belt. I would use a 12 mm shaft directly with locking rings.

In a CNC forum I found an information about so called "ballige Kugellager" (english: spherical/crowned/convex bearings?). They are thicker in the middle and self centre the belts. But they are not cheap.]]> JoergS5 CoreXY Machines Wed, 15 Aug 2018 13:58:31 -0400 https://reprap.org/forum/read.php?397,817215,831288#msg-831288 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831288#msg-831288
There's nothing stopping you from using 40 mm pulleys with glass core belts. The only problem there is how do you make the pulleys? You could try to print some pieces that fit over bearings, but if your print isn't really good, it may produce defects in the prints your machine produces. Imagine a seam that puts a little extra tug on the belt every time the pulley rotates, then multiply that by at least 8 for all the pulleys in the mechanism.]]> the_digital_dentist CoreXY Machines Wed, 15 Aug 2018 09:06:47 -0400 https://reprap.org/forum/read.php?397,817215,831280#msg-831280 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831280#msg-831280
I want to be flexible with pulley sizes on the stepper because I don't know which speed is possible maintaining a good quality print. It will be trial and error, I did not see a mathematical model anywhere to decide this. For example, is it possible to use 60 tooth pulleys on the stepper and run full speed?

Same uncertainty is with pulley diameter also: I thought about 40 mm diameter pulleys and using steel belts. But I don't know whether this is better than the glass fiber solution.

This uncertainties are the reason why I try to build a system which I can change fast, to allow experiments. So my goal is to use a highly modular system (Z totally separated from XY, and both from he frame).

I agree with you that if a solution does not fit, then construct another one. That is the reason why I have to build a small CNC machine first now. I have problems boring drilling exact holes in aluminium...]]> JoergS5 CoreXY Machines Wed, 15 Aug 2018 07:50:35 -0400 https://reprap.org/forum/read.php?397,817215,831278#msg-831278 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831278#msg-831278
To me, adding more pulleys is a lot more trouble than measuring the belt thickness. If you're going to tension the belts by moving the motors anyway, why not put them in the correct left-right positions and make sure the adjustment only moves them in Y (use the slots in the frame as the guide for the motion)? I've seen some builds where people actually put in two pulleys and bend the cable path 90 degrees so that moving the motors in X tensions the belts. If you did that, you could change pulley sizes on the motors, and change belts without regard to thickness because the extra pulleys will keep everything that needs to be aligned in place.

I think it's like making screw-adjustable tensioners. You can do it, but you only have to tension the belts once, so is it worth the trouble of a complex design? If the parts that mount the motors and pulleys are all printed, it isn't difficult to change the dimensions and just print another part if you decide to change from a 16 tooth drive pulley to a 20 tooth pulley, for example (but why would you ever do that?)]]> the_digital_dentist CoreXY Machines Wed, 15 Aug 2018 07:24:20 -0400 https://reprap.org/forum/read.php?397,817215,831275#msg-831275 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831275#msg-831275
Quote
the_digital_dentist



I want to rebuild your CoreXY construction but think about a modification, adding two pulleys:
[attachment 106621 coreyadditionalpulley.jpg]

The stepper can be a bit more right (left stepper) or more left (right stepper).

The additional pulleys are good for:
- easier align the three pulleys which must be in one line (4 identical housings, no belt thickness calculations, one pulleys axis line)
- tensioning of stepper is easier, as the position is not critical in X direction

What do you think?
]]> JoergS5 CoreXY Machines Wed, 15 Aug 2018 05:42:28 -0400 https://reprap.org/forum/read.php?397,817215,831259#msg-831259 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831259#msg-831259 o_lampe CoreXY Machines Wed, 15 Aug 2018 00:41:08 -0400 https://reprap.org/forum/read.php?397,817215,831192#msg-831192 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831192#msg-831192 DickH CoreXY Machines Tue, 14 Aug 2018 07:25:38 -0400 https://reprap.org/forum/read.php?397,817215,831096#msg-831096 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831096#msg-831096
You're going to need a metal bracket/fork to hold the pulley itself because there's no way to remove the tension on it. If you're going to keep putting tension on the adjuster parts (the pulley frame, etc.) you'll have to print them rotated 90 degrees (and use lots of support material) so that the tension is pulling along the layer lines. Everything will have to be bulked up, too. It would be better if you put the adjuster parts outside the enclosure so the belt tension puts some of them into compression.

You aren't going to need so much adjustment range to tighten the belts. You should be able to simplify the design a lot- like remove some of those extra pulleys that are going to greatly increase the load on the motors.

You can tension the belts at any of the locations shown in the image below:



If you push on the belts at the back and/or sides of the machine, you don't have to bend the belts around multiple pulleys at the corners. Pushing against the belts can be done using printed parts that are in compression, so they'll be much better able to handle the stress, and the belts won't have to wrap around the pulleys you use to do the pushing. It might be easier to redesign the clamps at the extruder carriage to allow tightening the belts there.

It seems you've sort of designed the machine in a backwards sequence. You designed/built the enclosure first, and now struggle to make the corexy mechanism fit and still preserve the desired build plate area. Maybe in your next printer, you can design the corexy mechanism first to achieve the motion you want, then design and build the enclosure around it. You may have to give up some of your print area to make a mechanism that fits in the enclosure. One thing I would recommend is that you try to reduce the number of pulleys that the belts have to wrap around.

I recently put together a large corexy mechanism driven by cables and designed the motor mounts and corner pulley mounts to fit in the Y axis parallel frame members. That arrangement lets me tighten the cables simply by sliding the motors or the corner pulley mounts back, then locking them in place using t-nuts that fit in the slots in the frame members. It would be even easier to apply that technique to a stacked belt driven system, and in fact, I may convert the cable driven system to a belt driven system due to some difficulties I'm having with the cables.
]]> the_digital_dentist CoreXY Machines Mon, 13 Aug 2018 07:33:51 -0400 https://reprap.org/forum/read.php?397,817215,831079#msg-831079 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831079#msg-831079
I think this is what I am going to go with for belt tensioning. This will replace my corner pulley brackets and will be bolted to the 2020 extrusion and to the wood backing. The tensioner will be adjusted on the back of the printer by adjusting a nut that draws the tensioner pulley in. This gives me about 1.25" of belt tension before it bottoms out. I think this is my best option as it doesn't effect print volume, it would have been easier to adjust tension with the steppers but they are mounted remotely to give a little extra room on the x axis. I have ordered the needed bolts, I wont be able to try it out until they show up,


]]> DickH CoreXY Machines Mon, 13 Aug 2018 05:19:58 -0400 https://reprap.org/forum/read.php?397,817215,831013#msg-831013 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831013#msg-831013
I wrote a blog post that goes into tensioning belts in a corexy machine (along with other relevant topics). There are several places you can do it, but you must not mess up the parallel relationship between the belts and the guide rails when you adjust the tension.

You normally buy belt in whatever length is available and cut it to the size needed with scissors. You'll have some left over for another project.

The X axis runs backwards probably because you have told the controller the wrong location of the endstop switch -i.e. you've set it up for left hand rule coordinates. It doesn't matter how the motor is mounted. An individual motor can be reversed by reversing the connections to it or by a minor change in the firmware configuration. In a corexy mechanism, you can't just reverse the connection to change the X direction because both motors work together to define the motion. If you reverse the direction of one motor by flipping the connector over, you'll swap the X and Y motion.

When you set up a corexy machine, the first thing to understand is right hand rule coordinates. CAD and slicers use RHR coordinates, so your printer must also use RHR coordinates or prints will come out mirrored. I recommend you set up the center of the bed as the machine's origin so that all slicers will drop prints at the center of the bed without having to make any custom gcode for each slicer you may use. The second thing to understand is that you must set the hardware and firmware so that the extruder carriage moves toward the endstop switches when you send a "home" command. The switches can be put at either end of either axis, just put them where it's convenient for you to either mount them or wire them. Once the extruder hits the switches, you assign ordinate values at each axis that will put the printer's origin at the center of the bed. I wrote two blog posts on setting up corexy machines. Start with this one, then read through this one. The first post deals with getting things moving in the right directions using RHR coordinates. The second with putting the printer's origin at the center of the bed. I used a SmoothieBoard and Duet in the examples, but the concepts are the same and apply to any controller. I should probably combine the two into a single post...]]> the_digital_dentist CoreXY Machines Sun, 12 Aug 2018 10:08:58 -0400 https://reprap.org/forum/read.php?397,817215,831001#msg-831001 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,831001#msg-831001
Something I am going to need to fix is that my X axis moves backwards. I assume this is due to my motors being mounted upside down. Is this something that can be corrected easily with the duet controller?]]> DickH CoreXY Machines Sun, 12 Aug 2018 08:58:29 -0400 https://reprap.org/forum/read.php?397,817215,830527#msg-830527 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,830527#msg-830527
Oh well...

You're on the right track, I could probably offer a few critiques, but I'm hardly an expert and am still tinkering with my own custom corexy.

Best of luck!]]> obelisk79 CoreXY Machines Tue, 07 Aug 2018 13:12:09 -0400 https://reprap.org/forum/read.php?397,817215,830489#msg-830489 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,830489#msg-830489
About the crossing belts... timing belts are intended to operate on pulleys with parallel axles with the belt running perpendicular to the axles. If you change the angle of the belt on the pulleys by changing the vertical displacement of the pulleys, you will create wear on the belt and the pulleys if they have teeth. You're loading the outer core elements of the belt much higher than the central core elements which will lead to rapid failure of the belt. There is absolutely no reason whatsoever to cross the belts in a stacked belt corexy mechanism. Tensioning the belts can be done by moving the motor mounts or corner pulleys in the Y direction, applying idlers at the outer segments or the back segments, or at the attachment to the extruder carriage (by pulling the belt in the X direction). You can't tension the belts individually- changing tension on one will change the tension in the other, no matter where or how you adjust the tension, even if you just move one motor mount, or pull on one belt at the extruder carriage.

So many people look at the original coreXY implementation and see crossing belts and think, "my belts better cross":



But if you look closely at the other photos, you can see that the belts in the original mechanism are stacked.



While the belts cross paths at the back of the mechanism, they don't cross in the XZ plane. Each belt stays either above or below the other at the motors, corner pulleys, and extruder attachment points. Look at the pulleys on the motors and the pulleys at the ends of the X axis, and the attachment points on the carriage. Two different Z levels, and each belt stays on its own Z level as it must.







The only layout that would require the belts to touch each other at the back of the mechanism is if the belts were both on the same Z level at the motors, the corner pulleys, the Y axis pulleys, and at the carriage attachments.
]]> the_digital_dentist CoreXY Machines Tue, 07 Aug 2018 07:54:52 -0400 https://reprap.org/forum/read.php?397,817215,830474#msg-830474 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,830474#msg-830474 DickH CoreXY Machines Tue, 07 Aug 2018 03:13:20 -0400 https://reprap.org/forum/read.php?397,817215,830458#msg-830458 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,830458#msg-830458
It also looks like there isn't nearly enough tension on the belts. If you don't pull them tight, the inertia of the mechanism will, briefly, every time motion starts/stops changes direction, like a big spring. You'll get exactly the opposite of what you wanted when you bought steel core belts.

I noticed that you crossed the belts at the back of the machine, but the belts appear to be stacked. In a stacked belt setup, there's no need to cross the belts, and it implies that each belt is starting at one level and ending up at another. Belts don't work well that way. The axles of the pulleys should all be parallel and the belt should run perpendicular to the axles. The only time the belts would have to cross is when they both occupy the same Z level. I wrote a blog post on corexy set up that might have some useful info for you.]]> the_digital_dentist CoreXY Machines Mon, 06 Aug 2018 18:29:31 -0400 https://reprap.org/forum/read.php?397,817215,830398#msg-830398 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,830398#msg-830398 They need bigger pulley diameters or they brake easily.]]> o_lampe CoreXY Machines Mon, 06 Aug 2018 05:14:03 -0400 https://reprap.org/forum/read.php?397,817215,830385#msg-830385 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,830385#msg-830385





]]> DickH CoreXY Machines Mon, 06 Aug 2018 03:58:47 -0400 https://reprap.org/forum/read.php?397,817215,821994#msg-821994 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,821994#msg-821994 DickH CoreXY Machines Sat, 12 May 2018 20:53:04 -0400 https://reprap.org/forum/read.php?397,817215,821936#msg-821936 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,821936#msg-821936
And yes, you will definitely need some means of adjusting belt tension. In the XY stage the belts should be at about the same tension. After you tension the first belt, pulling the second belt tight increases tension in the first belt, so don't set the first belt too tight initially. If the tensions are not close to each other, the X axis will tend to shift so it is not orthogonal to the Y axis, so after you tension the belts, you will want to verify the orthogonality of the X and Y axes. You may be able to do that using a machinist's or carpenter's square, or you can just print a square and measure the diagonals, which should match if the X and Y axes are orthogonal. If they are not orthogonal, you'll adjust one of the belt tensions a bit to bring them back to square.]]> the_digital_dentist CoreXY Machines Sat, 12 May 2018 08:36:32 -0400 https://reprap.org/forum/read.php?397,817215,821924#msg-821924 Re: Making a large CoreXY printer https://reprap.org/forum/read.php?397,817215,821924#msg-821924




]]> DickH CoreXY Machines Sat, 12 May 2018 04:52:30 -0400