Compact CoreXY Build I've started building my CoreXY printer, using a modified arrangement of the belts. My goal with this printer was to get a 200x200 print area, with all the components inside the frame so that I could have a heated build chamber. I also wanted to use all 305mm long 20x20 aluminum extrusions. Ultimately I ended up using 305mm extrusions with 435mm extrusions to get the desired print area. To make the arrangement more compact, I rotated the motors 90 degrees to the side and then rotated the belt crossing 90 degrees to the same side. Additionally, I rotated the belts 180 degrees where they crossed, so they don't interfere with each other. Crossing the belts also eliminates the need for any GT2 idlers - only the back of the belts ride on the idlers. To tension the belts, the two idlers at the top of the Y axis are moved along the extrusions. I'm using 8mm IGUS rods and linear bearings. Initially I had a lot of trouble getting these to run smoothly, but they seem to be working OK now. For stepper motors, I used two surplus NEMA 23 motors left over from my CNC mill. At this point, I have the X-Y stage done and have completed initial tests. I will say that I'm impressed with the speed. With minimal tuning and 12 volts (24 volts planned) I was able to command feed rates of 670 mm/s. Compared to my Taig CNC mill, my current 3D printer, which runs at a maximum of 25 mm/s, that's smokin'. Next I need to wire up endpoint switches and finish designing the z-axis. https://reprap.org/forum/read.php?397,417806,417806#msg-417806 Sat, 07 Mar 2026 19:51:13 -0500 Phorum 5.2.23 https://reprap.org/forum/read.php?397,417806,598534#msg-598534 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,598534#msg-598534 rcengr CoreXY Machines Sat, 19 Dec 2015 10:00:29 -0500 https://reprap.org/forum/read.php?397,417806,598266#msg-598266 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,598266#msg-598266 stratmaster458 CoreXY Machines Fri, 18 Dec 2015 12:33:34 -0500 https://reprap.org/forum/read.php?397,417806,597602#msg-597602 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,597602#msg-597602
Quote
billyzelsnack
When I saw the drawing of your CoreXY respin I instantly knew it was the belt path I wanted to try. [plus.google.com]

I like your machine.]]> rcengr CoreXY Machines Wed, 16 Dec 2015 15:08:11 -0500 https://reprap.org/forum/read.php?397,417806,597590#msg-597590 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,597590#msg-597590
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Skimmy
And get new belts every 3 months?

Not quite. I've been using my machine for over a year and there is still no visible wear on the belts. I'll have to look at my logs for the latest number, but last time I checked I had over 200 hours of print time. I haven't even needed to re-tension the belts.]]> rcengr CoreXY Machines Wed, 16 Dec 2015 14:48:01 -0500 https://reprap.org/forum/read.php?397,417806,597375#msg-597375 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,597375#msg-597375 Skimmy CoreXY Machines Wed, 16 Dec 2015 04:57:15 -0500 https://reprap.org/forum/read.php?397,417806,597374#msg-597374 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,597374#msg-597374 plus.google.com]]]> billyzelsnack CoreXY Machines Wed, 16 Dec 2015 04:46:08 -0500 https://reprap.org/forum/read.php?397,417806,564321#msg-564321 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,564321#msg-564321
The previous version of the z-axis you can find on the first page of this thread, look about 2/3 the way down.

I've attached a picture of my extruder. It's an original design, made from materials on-hand and with my CNC mill. It was only supposed to last until I got the printer going and then I was going to print a more common design. However, it has worked so well that I haven't been motivated to change it.

As you can see from the first picture, there's a hole at the top and bottom to guide the filament but nothing else until the drive gear.

The second picture shows the new grey filament support. It's printing right now so I can't take the shaft support off for a better picture. The nylon feed tube extends right up to the drive gear. On the other side, the Bowden tube extends down to the drive gear, so the filament is constrained over almost it's entire path through the extruder.]]> rcengr CoreXY Machines Tue, 29 Sep 2015 20:11:25 -0400 https://reprap.org/forum/read.php?397,417806,564087#msg-564087 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,564087#msg-564087
Your post is very interesting. It is rare that somebody goes into such depth to investigate problems.

I would like to know more about how your parts looked throughout the process. It will help me in the future if I come across something like it.

Any chance you can take some pictures of your older parts? Especially I am interested how it looked before you fixed the filament issue.]]> LarsK CoreXY Machines Tue, 29 Sep 2015 08:18:50 -0400 https://reprap.org/forum/read.php?397,417806,563889#msg-563889 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,563889#msg-563889
First, in regards to the long arm length on the bed. This does cause some problems, as very small movements at the bearings or z-axis screw are amplified out on the bed. My answer was to pre-load the bearing slightly with an arm on the base of the bed. It's just a printed 608 bearing holder that rides on an extra 2020 extrusion. By bending the arm slightly, it presses the bed to one side.

After trying various changes to my z-axis screw, including moving from a 10mm to 8mm screw, without any results, I finally got around to seriously analyzing the problem. First I printed out some 25mm cubes with single and double walls and did some careful measurements. It was soon evident that my problem was z-ribbing, rather than z-wobble. Each bulge on a side was also matched by a bulge at the same z height on the other side. If the problem had been z-wobble, the side opposite the bulge would be inset. The period of the bulges matched the pitch of the screw.

I put a dial indicator on the bed and jogged the bed down 2mm (the screw pitch) stopping every 0.1mm and taking a reading. When plotted the height variation was obvious. I had an error of about 0.12mm peak to peak. That's a lot when using layer heights of 0.25mm.

After a lot of reading, it seemed that there were 3 main causes of z-ribbing. The most common cause was rounding error when using a imperial screw with metric heights. Since I'm running a metric lead screw and using layer heights that were divisible by full steps, this seemed very unlikely.

The second cause was bed temperature variation, normally due to bang-bang control. I'm using PID control on the bed, so I didn't think this was my problem. I watched the bed temperature read out on Repetier Host and it varied less than +- 0.5 degrees C. I also put a dial indicator on the bed and it didn't move.

The last common cause I found was a misaligned axis and screw. Since I was using the lead screw nut holder to also tie the sides of the bed support together, I thought this might be part of the problem. So first I put a piece of 2020 extrusion between the bed sides. That allowed my to take my z lead screw nut holder and move it around to get the best alignment. As a result, I eliminated about 1/2 of the error (trial 10 on the chart).

To eliminate the rest of the error I tried many different alignments of the lead nut holder. I tilted it, moved it left and right, in and out, all for no real change in the error. I also tried different bearing arrangements: thrust bearing only at the top, 608 bearing at the top, and 608 bearings top and bottom. Nothing improved the error.

Finally after reading about a lot of the different z-screw connectors that fixed other z-ribbing issues, I changed out the coupler. I was running a spiral cut aluminum coupler and I put a rigid coupler made from brass in its place. That eliminated most of the rest of the error (trial 21 on the chart). My dial indicator has graduations of 0.001 inches (+-0.0127mm) so when you add the error bars to the chart, almost every point is within the measurement error.

Even with this small error, z-ribbing was still evident in the printed parts. I tried some other adjustments, but nothing really improved the prints. Plus the error was too small to really track down with the dial indicator that I was using.

At this point I suspect the plastic nut was causing my problems. Maybe the initial running of the screw in the misaligned position caused the nut to wear unevenly. I considered buying another replacement lead screw and/or nut, but I decided I wanted to stop messing with the problem regardless of the cost. So I ordered a stepper motor with an integrated lead screw from Pololu (https://www.pololu.com/product/2268) with a brass nut rather than a plastic one. Installation of the new stepper motor and lead screw eliminated all of my z-ribbing.

I still had some z artifacts, but now they were no longer the same spacing at the lead screw pitch. I had the filament twist out my extruder a couple of times as it got to the tightly coiled part at the end of the reel, so I added a filament guide made using 4" of nylon tubing. It not only eliminated the tendency for the filament to twist out, it also eliminated most of my remaining z artifacts. I guess the filament was wandering side-to-side and causing a variation in the extruded plastic. As a bonus, the filament is much easier to load now.

The printer has in excess of 150 hours on it now. The crossed belts are still working fine, with little wear visible other than a slight shininess to the belts.]]> rcengr CoreXY Machines Mon, 28 Sep 2015 21:04:28 -0400 https://reprap.org/forum/read.php?397,417806,524130#msg-524130 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,524130#msg-524130
Direct rubber on rubber where the belts cross is bound to create some wear. Any updates on the silicone or a separator made out of PLA, Teflon or even a polished steel pin?

Look at how close the Smartrap Core bed is to its rail supports. You had to add quite a bit of arm length and cantilever the bed out to clear the Y slider. How about moving the Z supports and Zscrew to an adjacent side of the cube which allows the bed to be moved closer to the Z rails?

Lots of things can cause Z artifacts. Did you try a dial indicator mounted to the X carriage to look for wiggle and repeatability?]]> to-the-nth CoreXY Machines Sat, 20 Jun 2015 19:16:17 -0400 https://reprap.org/forum/read.php?397,417806,478221#msg-478221 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,478221#msg-478221
If you like the two level belt system, check out this new thread: Smartrap Core The designer has a good job of keeping everything simple. I've spent some time playing with the JSCAD and really liked what I saw. I think if I didn't already have a new a machine that I would build one.]]> rcengr CoreXY Machines Mon, 02 Mar 2015 19:53:20 -0500 https://reprap.org/forum/read.php?397,417806,478028#msg-478028 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,478028#msg-478028 Zavashier CoreXY Machines Mon, 02 Mar 2015 12:33:33 -0500 https://reprap.org/forum/read.php?397,417806,477992#msg-477992 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,477992#msg-477992


This one maybe ?

Mourakami
]]> Mourakami CoreXY Machines Mon, 02 Mar 2015 11:04:28 -0500 https://reprap.org/forum/read.php?397,417806,477586#msg-477586 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,477586#msg-477586 Zavashier CoreXY Machines Sun, 01 Mar 2015 12:10:45 -0500 https://reprap.org/forum/read.php?397,417806,477367#msg-477367 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,477367#msg-477367
I don't see where you made any changes to the drawing you attached. It still shows the belts crossing in the same manner that I'm using.]]> rcengr CoreXY Machines Sun, 01 Mar 2015 05:10:30 -0500 https://reprap.org/forum/read.php?397,417806,477106#msg-477106 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,477106#msg-477106 Zavashier CoreXY Machines Sat, 28 Feb 2015 10:36:14 -0500 https://reprap.org/forum/read.php?397,417806,476862#msg-476862 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,476862#msg-476862 rcengr CoreXY Machines Fri, 27 Feb 2015 21:48:11 -0500 https://reprap.org/forum/read.php?397,417806,476855#msg-476855 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,476855#msg-476855 nka CoreXY Machines Fri, 27 Feb 2015 21:29:15 -0500 https://reprap.org/forum/read.php?397,417806,476846#msg-476846 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,476846#msg-476846
The crossed belts are working fine, but there is some visible wear. After about 30 hours of printing I did a partial tear down and examined the belts. They were slightly shiny along the edges and there was a very fine black dust around the bearings. So there is definitely wear, but I don't expect it to cause problems for a while. If I have to replace the belts after every 200 hours or so it will be OK. I think I might put some silicone grease on the back of the belts and see if that reduces wear.

The speed is just phenomenal. Just running some basic moves with gcode, the printer was easily able to move at 500mm/s without the motors stalling. However, when printing files I was having problems with it missing steps randomly throughout the file. I think the 500mm/s was outpacing either the processing or the buffer in the Marlin software and causing the missed steps, since it didn't seem to be a mechanical problem. I dropped the rapid speeds down to 250mm/s with 125mm/s fill and 80mm/s perimeters for very reliable printing. Also very interesting is that the printer runs reliably with the jerk set to 100mm/s. After running some acceleration calculations, I decided that I really didn't need the 100mm/s and dropped the jerk to 50mm/s to reduce stress on the machine. It still does short back and forth fills so fast that it looks like a sewing machine.

I do have an issue with z-banding. I had the z axis screw supported with bearings at both ends to start, so I knew I would probably have a problem. Unfortunately, even though I changed the screw to free up the bottom end and added some set screws to better anchor the 12mm rods, the problem has just gotten worse.

I've been very happy with the IGUS bearings and aluminum rods. They are very smooth and quiet. I was surprised that if the carriage was slightly cocked that they would jam. But the pull from the CoreXY system is so even that there was never a problem once the belts were on. I would not try and use these bearings for an H-bot setup though. I think the aluminum rods are bending a little too much, causing the carriage to dip when it is in the center. I should have gone with 10mm rods instead of 8mm. The 10mm rods would have had similar stiffness to 8mm steel rods and still would have weighed less.

The remote fan on the hot end is working OK. I think I need a little more flow, the two lowest fins on the E3D are too hot to hold my fingers on. The top of the heat sink is still cool to the touch. So while I've done as long as a 7 hour print in ABS with no problems, I suspect that it would not work for PLA.]]> rcengr CoreXY Machines Fri, 27 Feb 2015 20:28:43 -0500 https://reprap.org/forum/read.php?397,417806,451385#msg-451385 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,451385#msg-451385
After leveling the bed and calibrating the thermistors, it was ready to print. I have to tune the retract settings to get rid of some blobbing, but the dimensions are right on. After using my mill to print for the last 9 months, it is very exciting to see rapids at 500 mm/s instead of 25 mm/s and infill is going at 100 mm/s instead of 20 mm/s. Next is figuring out the end stops and then taming my rat's nest of wires.]]> rcengr CoreXY Machines Mon, 05 Jan 2015 19:42:56 -0500 https://reprap.org/forum/read.php?397,417806,445708#msg-445708 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,445708#msg-445708 rcengr CoreXY Machines Fri, 19 Dec 2014 17:32:50 -0500 https://reprap.org/forum/read.php?397,417806,445702#msg-445702 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,445702#msg-445702
I also re-worked the remote fan to give a little more airflow. By pulling the fan out of housing and putting it in a centrifugal housing, the airflow increased appreciably. Updated STLs have been posted on Thingiverse.]]> rcengr CoreXY Machines Fri, 19 Dec 2014 17:19:40 -0500 https://reprap.org/forum/read.php?397,417806,445692#msg-445692 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,445692#msg-445692 rcengr CoreXY Machines Fri, 19 Dec 2014 16:58:08 -0500 https://reprap.org/forum/read.php?397,417806,445598#msg-445598 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,445598#msg-445598
I don't think the "teeth" on the belt are sufficient to displace the belt and therefore the print.]]> grat CoreXY Machines Fri, 19 Dec 2014 11:37:20 -0500 https://reprap.org/forum/read.php?397,417806,444686#msg-444686 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,444686#msg-444686 rcengr CoreXY Machines Wed, 17 Dec 2014 06:17:14 -0500 https://reprap.org/forum/read.php?397,417806,444586#msg-444586 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,444586#msg-444586 jtoombs CoreXY Machines Wed, 17 Dec 2014 00:43:45 -0500 https://reprap.org/forum/read.php?397,417806,444560#msg-444560 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,444560#msg-444560 ekaggrat CoreXY Machines Tue, 16 Dec 2014 21:55:25 -0500 https://reprap.org/forum/read.php?397,417806,438172#msg-438172 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,438172#msg-438172 Ohmarinus CoreXY Machines Sat, 29 Nov 2014 16:47:18 -0500 https://reprap.org/forum/read.php?397,417806,437893#msg-437893 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,437893#msg-437893
I know there are several discussions regarding cooling a hotend inside an enclosed printer, so this setup should give everyone something to experiment with. The 3D files are posted here: http://www.thingiverse.com/thing:569044 I've put in files for both the v5 and v6, but I've only printed and fit the v5 version.]]> rcengr CoreXY Machines Fri, 28 Nov 2014 19:45:37 -0500 https://reprap.org/forum/read.php?397,417806,431599#msg-431599 Re: Compact CoreXY Build https://reprap.org/forum/read.php?397,417806,431599#msg-431599 rcengr CoreXY Machines Wed, 12 Nov 2014 22:44:17 -0500