CoreXY vs Quadrap mechanism Any insights on CoreXY vs Quadrap mechanisms for precision? Any gotchas I should know about with either? I'm starting to think about building another printer and I like the CoreXY mechanism, but I think I want to go tall- 300mm square bed and 1m tall print capability. I have done some searches but have been unable to find anything on a tall CoreXY machines. Has anyone seen/done that sort of thing? https://reprap.org/forum/read.php?397,589599,589599#msg-589599 Sat, 11 Jul 2026 10:25:03 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?397,589599,593526#msg-593526 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,593526#msg-593526
If you have that error in just the Z axis, your layer thickness will vary, causing Z banding in the prints, possibly making it difficult to get parts to stick to the bed reliably, even if the bed is flat and level. So you'll use auto leveling to ensure the first layer sticks. But if the position of Z=0 isn't located precisely, and the bed isn't actually flat (autoleveling assumes it is) autoleveling may not work well. If you have that error in just the Y axis or X axis, layer registration may be off, producing Z banding and making close tolerance parts hard to fit together, and waves, ripple, or other textures may appear in the surface of the prints.

Now imagine all three of those errors at once. Now compound those errors with flex in the machine's frame. How reliable is your printer going to be and what will the prints look like? Yes, I'd say all that sounds about right for the tolerances found in typical 3D printers, judging by the prints I've seen.

How long are bushings going to last when they slide along the rails as much as they do in a 3D printer? What's going to happen to print quality as the bushings wear? One of the big reasons to use ball bushings or linear guides is to reduce degradation in print quality due to wear in the mechanism.

Plastic bushings are usually pretty quiet, at least until they wear and start to chatter. Linear guides and ball bushings do make a little of that steel-balls-rolling-on-steel-rails noise, but it's usually masked by the noise from fans and noise created by vibrations in the drive motors.]]> the_digital_dentist CoreXY Machines Sun, 06 Dec 2015 10:15:45 -0500 https://reprap.org/forum/read.php?397,589599,593355#msg-593355 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,593355#msg-593355
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the_digital_dentist
Misumi's first sentance says it all: "If you need a quick and easy way to facilitate a linear motion profile, the linear bushing is a great choice, especially if you don’t have high tolerance or accuracy requirements. "

They also say "However, these errors are typically small, on the order of a few thousandths of an inch. The setup and maintenance are also very inexpensive compared to other options.' Aren't these tolerances well within what we use in 3D printing?

Moreover, IGUS dry-lin, the bushings I have mentioned, document the offered tolerances and the way their bushings have to be installed to maintain precision. Bushings seem to be adequate for loads that fall within their documented values. Of course linear ball-bearings are very good and offer a much higher upper load limit. I understand that finding cheap linear rail is way better than buying smooth rod for both weight (haven't check if one linear rail is lighter than two smooth rods of same length) and complexity issues regarding parallel installation but they are much more than needed for many carriages (bowden take the load off the carriage, allowing higher speeds, necessary in prototyping applications). Also bushings offer the noise reduction that many require for consumer-grade appliances that we keep in our homes.

At the end of the day, you seem to have a garage/workshop where you do the 3d printing, many of us have some room just next to us. That allows you to have industrial-grade equipment and can go overkill to whatever lengths you please. For me engineering is also about using least amount of material/etc for the needed task, and that's why bushings seem such a good fit. I calculate my carriage weight and size my other components accordingly. I would even use hollow linear tubing if they would be available with the tolerances offered by smooth rods.

In the first posts regarding the quadrap mechanism there were youtube links to machines that used hollow tubes for movement. I get it that they were only examples but I find it appropriate to the task, should the linear tubes be really "linear". But I only know of "linear" aluminum extrusions (T/V-slot profile) or this type of sliding linear rail that can be used as a light-weight alternative to steel shafts or steel rail. Personally my view is that the industry wasn't quite prepared for lightweight applications like FFF and all we use now, or the vast majority are retrofitted industrial standards from the CNC industry. There might be lighter weight linear options but because they are niche, they were too expensive to retrofit.]]> realthor CoreXY Machines Sun, 06 Dec 2015 02:35:02 -0500 https://reprap.org/forum/read.php?397,589599,593342#msg-593342 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,593342#msg-593342 especially if you don’t have high tolerance or accuracy requirements. "
I consider a 3D printer to be a mechanism that requires high accuracy and precision (i.e. tight tolerances), which rules out bushings. Every bushing I've ever seen wiggles on the rail. You can double them up to get more stability, but that increases size. Having to use two round rails increases size/mass, too. I started with brass bushings in my printer a few years ago and quickly replaced them with linear bearings. I finally replaced all that stuff with linear guides about a year ago.

My X axis went from this ugly mess (two 1/2" rails with brass bushings):



to this (one linear guide mounted on a 1" square tube):



If you want high quality output from the printer, the design and parts used to make it also have to be high quality. Look at your prints and be very critical (I like to examine mine under a microscope). How does your print differ from the CAD design? Did the CAD design have those ripples in the surface? Was it perfectly round? Is your print? Are the layers laid on top of each other precisely? Do printed gears fit together and turn against each other without binding? Try to understand how the defects are created and what can be done about them. With FDM printing, most defects can be fixed with quality construction and components, including guides/bearings.

This is what sturdy construction and quality bearings/guides can do:


That's the corner of a calibration cube printed in 250 um layers.

Linear guides don't have to be expensive. Search for "linear guide" on ebay and you'll find at least 10 pages of listings. I recently picked up a new-old-stock 630 mm long IKO linear guide with bearing block for $34 shipped. There's a dealer in Korea who sells hundreds of the things for very good prices, shipping anywhere in the world included. Another in Canada whose listings show photos of what has to be thousands of linear guides and lead screws.

Regardless of architecture, it will probably cost more than $300 to build a machine with a rigid frame and quality guides/bearings and electronics. Quality costs. It always has and always will, because it's worth more.
]]> the_digital_dentist CoreXY Machines Sun, 06 Dec 2015 00:36:46 -0500 https://reprap.org/forum/read.php?397,589599,593328#msg-593328 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,593328#msg-593328
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realthor
Belts are difficult to use in non-linear devices like the one I linked.

@patrickrio:
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patrickrio
The whole point of the discussion is to bring attention to the "gotchas" of installation - and parallel is the biggest gotcha I see for CoreXY when using linear guides. Maybe it is not that big of a gotcha, but I think it may be the biggest one. Adding lips to a design may not cost much, and pretty much eliminates (or at least reduces substantially) all facets of the problem as it exists in the CoreXY mechanism.

Is there anything that can be done for linear rods-based CoreXY to improve parallelism? I am designing my Y carriages myself so I am thinking that maybe my lack of experience will get me to miss something that could otherwise improve my design or make it perform as expected. I see a lot of Corexy designs that are pretty simple, with Y carriages sliding on rods via 2 linear bearings while they have two clamps for the X rods. I don't think one can do it otherwise with rods. Maybe use all-metal/machined carriages for best thermal/wear stability and long life.

I am also thinking of using bushings, maybe the exact igus bushings that one of the machines in the first posts examples is using because bushings have (i might be wrong) better tolerances than linear bearings, at least better than cheap linear bearings. Maybe if compared with same-priced linear bearings (igus DryLin® R - RJ4JP 01-10 goes for Eur4 a pop on amazon.de). But still 10mm linear rods + such expensive bearings are cheaper than similar linear steel rail. I am talking about new ones, I didn't find SH ones around.

Linear bushings are described by Mitsumi as the lower-end cousing of Linear Guides. I thought that they were right there at the top but apparently I was wrong. I guess round shaft is somewhere in the "amateurish" drawer of serious engineering while the former are the de-facto solutions for linear movement. I just don't see such expensive motion systems to make much sense at least in non-commercial 3D printing. Not that I wouldn' like to use them or have them but for most is just like buying a best in class TV and watching from a distance where the pixel density of HD can't really be observed anymore.]]> realthor CoreXY Machines Sat, 05 Dec 2015 23:04:16 -0500 https://reprap.org/forum/read.php?397,589599,593310#msg-593310 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,593310#msg-593310 non-linear then you talk about linear ( in line applications) ?????

No belts are easy to use -- sort of like a flexible rack and pinion
Since they are toothed -- positional accuracy can be maintained

Belts are used in many CNC machines like this:

[www.shapeoko.com]

[s3files.core77.com]

[www.inventables.com]

[www.tool-rank.com]

:S

A timing belt pulley is easy to CAD and 3D print. How large of a pulley are you using?


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realthor

Belts are difficult to use in non-linear devices like the one I linked to because it's difficult to engage a toothed pulley that sits in between to segments of straight line. One would have to insert two additional pulleys that would force the belt go around as many teeth as possible around the large pulley, something like this. Also having such a large pulley like in my design is quite difficult to have it machined. The closest I can think of is glue a belt around it so the other belt has something to engage to.
]]> cozmicray CoreXY Machines Sat, 05 Dec 2015 20:39:18 -0500 https://reprap.org/forum/read.php?397,589599,593169#msg-593169 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,593169#msg-593169
And to your point, I am also using my rails in ways that would make the manufacturers cringe. I am not chastising you for doing the same thing, believe me. However, I do think that when I do my next CoreXY i will likely use a plate like you are. I also think that machining 2 parallel lips might not be very expensive on such a plate. If the cutout and holes of the plate are done by CNC, the parallel lips may only require another automated tool change and two tool passes. In addition to any warranty advantages, the lips make initial setup easier, and make replacing parts easier too. Rail installation only requires clamping rails against the lips and then putting screws in all at the same time as fast as you please, perfect parallel every time with dramatically smaller chance of error. For one off machines and prototypes it may be desired to "skip the lips" for simplicity and iterative advantages, but the more standardized and repetitive a machine design becomes, the more the lips make sense.

Obviously the warranty only matters if you are buying new guides. It seems that the mounting lip are more of an immediate warranty disqualification than anything. If they know you didn't use a mounting lip in a paired guide situation, your claim is immediately disqualified. They also inspect returned guides and parallel failure has an easily recognized wear pattern.

Of all the rail manufacturers I talked to IKO the most and in greatest detail.

The engineer at IKO I talked to said that failed rails due to lack of parallel was the biggest failure mode of installed rails and since it wasn't their fault they didn't want to bear the cost of warranty. He said that the main other disqualification was if the rails were obviously loaded out of tolerance. However, he said that loads out of tolerance were a bit less cut and dried, so disqualification in this case mainly happened in cases of gross overloading. Once again, the wear pattern on rails was a big clue to overloading. Other than this, he said they rarely had problems, and tended to honor warranty claims that DID happen pretty liberally.

I did not get into the warranty weeds in my discussions with other companies, but I assume some similarity.

As for the warping with heat, the lip would probably tend to help with that too..... the screws move slightly in the holes over the length of the rail, but the lip distance from the holes changes very little....

Edit: forgot the 3rd major failure mode IKO mentioned... dirty environment with hard abrasive dust and not installing approved rail sweeps. Once again, inspecting the guides gives teltale signs of this owner caused failure mode.

The whole point of the discussion is to bring attention to the "gotchas" of installation - and parallel is the biggest gotcha I see for CoreXY when using linear guides. Maybe it is not that big of a gotcha, but I think it may be the biggest one. Adding lips to a design may not cost much, and pretty much eliminates (or at least reduces substantially) all facets of the problem as it exists in the CoreXY mechanism.

Best,

Patrick]]> patrickrio CoreXY Machines Sat, 05 Dec 2015 11:10:16 -0500 https://reprap.org/forum/read.php?397,589599,593155#msg-593155 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,593155#msg-593155
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patrickrio
Yes, that is the procedure for getting parallel.... however, some of the manufacturers feel pretty strongly that this is not enough to meet spec. a few of the manufacturers, IKO for example, will not even honor the warranty on their smaller sealed guides if you do not have a mounting lip. I believe this is up to their 12mm rail miniature sealed guides.

I did not have a lip on my design either, and did exactly as you did to get them parallel.

Since I'm buying used linear guides, I don't care about a warranty. It's a simple mechanism. It isn't going to suddenly stop working- the block won't sieze up one day, the balls aren't going to fall out of the bearing block, and the rail isn't going to break in two. All that will happen is motion will get sloppier as the rail and balls wear. It will have to get a lot sloppier to be as bad as bearings on a round rail, so even when the linear guide is out of spec, it's still better than the next best thing. Look at the load specs for even a small linear guide. The loads they are subjected to in a 3D printer are a tiny fraction of their rated loads. They aren't going to wear out in your lifetime. If you don't have the alignment absolutely perfect it doesn't matter. If the thing moves easily (easily enough for a wimpy little NEMA-17 motor to move it) without binding, it's aligned as well as it needs to be. The procedure I used to align the parallel rails in my machine gave very even, smooth motion so I'm not going to worry about it, and I'm going to keep on using linear guides, probably in ways that would make the manufacturers cringe.

What does a linear guide warranty cover? How would you even make a warranty claim on a linear guide? Are you going to track the distance the thing has moved in your printer? How would you do that? Would you provide the design of the printer to the linear guide manufacturer to prove that there are no stresses that exceed the products specs? Do you know what the actual loads are in your printer? How would they be able to tell from your design what the loads are in your machine? Would they bother trying to analyze it?

Here's something to think about- the linear guide is made of steel and we typically mount them on aluminum. What happens as the temperature rises in the machine? The aluminum expands a lot more than the steel- are the rail mounting screws going to slide a little in their holes or is the whole thing going to warp? What happens to your extremely careful alignment even if you have the manufacturer recommended reference lip? What happens to your alignment after multiple heat/cool cycles?

You can worry about all this stuff or you can build your machine and get it working. Even with less than ideal installation, linear guides work better than the next best thing.]]> the_digital_dentist CoreXY Machines Sat, 05 Dec 2015 10:26:21 -0500 https://reprap.org/forum/read.php?397,589599,593124#msg-593124 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,593124#msg-593124
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J-Max
And a good link about the 6 degrees of freedom and accuracy measurement : Ensuring Linear Motion Devices Meet the Needs of the Application
They uses a granite block as reference plate. I guess sadly none of us own one.
But reference can be one stile (or rail) of your structure. But you need to always reference to... that reference.
You should not reference from another element until that element is perfectly referenced with your initial reference.
(Uh... I wonder if I'm understandable...)

Yes, reference to initial reference seems like the best solution as you only need your machine to be parallel to your machine. Perfectly understandable. I wonder how much would such a contraption cost and if it makes sense for us who can't really build machines with the accuracy that such dial contraption would ensure.

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J-Max
Here Spectra line is expensive. (about 16€/roll) I guess anywhere over the world you want Spectra line to save money.
First, even if you can get a cheap Specta spool, you're only saving fiew bucks.
Belts are accurate and pulleys are machined. Printed Spectra pulleys are probably not as accurate.
If quality comes first and price comes seccond, you want belts and pulleys or better.

Belts are difficult to use in non-linear devices like the one I linked to because it's difficult to engage a toothed pulley that sits in between to segments of straight line. One would have to insert two additional pulleys that would force the belt go around as many teeth as possible around the large pulley, something like this. Also having such a large pulley like in my design is quite difficult to have it machined. The closest I can think of is glue a belt around it so the other belt has something to engage to.

The only really bothersome thing with spectra is motor engagement (no teeth) and string walking. Very annoying indeed, loosing a lot of accuracy there :(.]]> realthor CoreXY Machines Sat, 05 Dec 2015 08:10:14 -0500 https://reprap.org/forum/read.php?397,589599,593123#msg-593123 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,593123#msg-593123 patrickrio CoreXY Machines Sat, 05 Dec 2015 08:05:10 -0500 https://reprap.org/forum/read.php?397,589599,593121#msg-593121 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,593121#msg-593121



]]> patrickrio CoreXY Machines Sat, 05 Dec 2015 07:59:37 -0500 https://reprap.org/forum/read.php?397,589599,593118#msg-593118 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,593118#msg-593118

And a good link about the 6 degrees of freedom and accuracy measurement : Ensuring Linear Motion Devices Meet the Needs of the Application
They uses a granite block as reference plate. I guess sadly none of us own one.
But reference can be one stile (or rail) of your structure. But you need to always reference to... that reference.
You should not reference from another element until that element is perfectly referenced with your initial reference.
(Uh... I wonder if I'm understandable...)

Here Spectra line is expensive. (about 16€/roll) I guess anywhere over the world you want Spectra line to save money.
First, even if you can get a cheap Specta spool, you're only saving fiew bucks.
Belts are accurate and pulleys are machined. Printed Spectra pulleys are probably not as accurate.
If quality comes first and price comes seccond, you want belts and pulleys or better.

++JM
]]> J-Max CoreXY Machines Sat, 05 Dec 2015 07:45:42 -0500 https://reprap.org/forum/read.php?397,589599,593114#msg-593114 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,593114#msg-593114
+patrickrio: Regarding the equal tension belts I endorse such tactics and I believe that they should be implemented in more designs that fragment the motion with several belts. Belts are cheap, spectra is even cheaper. I have actually designed such a single-wire Z-lift platform in my "rotary-only motion" experiments but at least on this forum it didn't have much success (maybe too complicated for ensuring accuracy). It has a single spectra line that goes around all the pulleys and is only tensioned in one spot then clamped on each pulley. It is easier with belt because of the teeth that make it so much more easier to clamp.

+DD: I am also building a corexy and am very interested in a good way to ensure parallelism between X and Y carriages. Thanks DD for pointing that out, I haven't come across the procedure so far.

Why does the Quadrap looks so much like the ultimaker's XY arrangement? What is so special about it that it is only now that this design starts to pop in forum posts and 3d printers? I get it that it uses spectra and replaces the linear rods Y with alu extrusions but you can do that with corexy and it looks cleaner and simpler.]]> realthor CoreXY Machines Sat, 05 Dec 2015 07:17:41 -0500 https://reprap.org/forum/read.php?397,589599,592183#msg-592183 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,592183#msg-592183
I agree with patrickrio. Maybe a lot of people here knows already that.
The proper way to set up the seccond rail ils to mount a dial indicator on the first one and measure distance on the full stroke.
Through, the first rail must be mounted accurately too. It's wise to provide a screw adjusting system on at last one plane on each rail.
It's crucial on acurate linear rails, but it's still important on any guide system for the efficiency, accuracy and durability.

++JM]]> J-Max CoreXY Machines Thu, 03 Dec 2015 03:11:16 -0500 https://reprap.org/forum/read.php?397,589599,592090#msg-592090 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,592090#msg-592090
I did not have a lip on my design either, and did exactly as you did to get them parallel.]]> patrickrio CoreXY Machines Wed, 02 Dec 2015 17:42:03 -0500 https://reprap.org/forum/read.php?397,589599,591534#msg-591534 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,591534#msg-591534
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patrickrio

When I was researching my printer, I talked to almost every major linear guide manufacturer (around 10 manufacturers). One very important feature in the CoreXY design when used with linear guides is to keep the Y axis guides perfectly parallel. And they really mean perfectly parallel!!! The most common failure for linear guides in all machinery is apparently not getting guides parallel. Hard linked linear guides (like what we do when clamping the X axis to the Y axis...) have no tolerance for variation in parallel at all. The best guides have an even LOWER tolerance for variation in parallel than the cheaper guides. Several of the manufacturers recommended that you machine perfectly parallel lips on the mounting plate at the inner edge of the two guides. Then you actually clamp the guides against the lips before screwing them into place. Apparently it is almost IMPOSSIBLE to drill holes in your plate accurately enough to keep parallel spec on the best guides. Since I did not use parallel lips, or even a mounting plate, I used cheap Chinese guides that have more forgiving tolerances and are more disposable. I suspect that YOU will be using sealed linear guides which have VERY tight tolerances and will probably require the lips.

I am using two parallel linear guides in the Y axis of my printer. I didn't have much trouble getting them parallel- the procedure for aligning them parallel is similar to aligning round guide rails- you move the carriage to one end of the rails, tighten it down, then move to the other end and tight it down. In the case of linear guides, instead of going to the opposite end, you move it down past the next hole and tighten those screws, and keep going until you reach the far end of the rails. The final adjustment is to loosen the screws in the bearing blocks and move the carriage back and forth a few times, then tighten those screws back down. Though not ideal, it seems to work fine in my printer's Y axis.]]> the_digital_dentist CoreXY Machines Tue, 01 Dec 2015 12:15:37 -0500 https://reprap.org/forum/read.php?397,589599,591160#msg-591160 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,591160#msg-591160 patrickrio CoreXY Machines Mon, 30 Nov 2015 14:33:15 -0500 https://reprap.org/forum/read.php?397,589599,591109#msg-591109 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,591109#msg-591109
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patrickrio
I was also concerned with belt length and also bowden tube length. I therefore really concentrated on keeping my movements tight to the printbed, and the carriage small. Every mm you can shave from either X or Y axis length means 4mm less belts used. You could mount the bowden tube vertically above the printer bed center to shorten the bowden tube for a large printer.

That is some good insight. Your comment about extruder in center just jerked my mind into a solution for a problem of heat enclosing my printer, that I have been boxing with for a week. Thank you.

About twisting belts; The center cord stays the same length so it should have zero impact. It is commonly used and also described in literature, such as here from Mechanical Components Handbook . I also use twisted belts.]]> LarsK CoreXY Machines Mon, 30 Nov 2015 12:00:18 -0500 https://reprap.org/forum/read.php?397,589599,591079#msg-591079 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,591079#msg-591079
I included a design feature in my printer that guaranteed equal belt tensions always. I used 1 continuous belt for both belt paths. you fix the belt ends on one side of the carriage first, and then, when you get the tension right, you just clamp the belt to the other side of the carriage to separate the single belt into 2 functional belts. This requires the belts to be on the same plane of course. BUT with a larger printer like you plan, a belt cross is even less of a problem than it was in my printer (which is to say, ZERO problem, with ZERO accuracy effects and no belt wear problems...). I guess, from reading your posts, that your sensibilities may encourage you toward separate levels for your belt paths.... However I think you will find that a correctly designed belt cross/twist will just work better for you.

I was also concerned with belt length and also bowden tube length. I therefore really concentrated on keeping my movements tight to the printbed, and the carriage small. Every mm you can shave from either X or Y axis length means 4mm less belts used. You could mount the bowden tube vertically above the printer bed center to shorten the bowden tube for a large printer.

When I was researching my printer, I talked to almost every major linear guide manufacturer (around 10 manufacturers). One very important feature in the CoreXY design when used with linear guides is to keep the Y axis guides perfectly parallel. And they really mean perfectly parallel!!! The most common failure for linear guides in all machinery is apparently not getting guides parallel. Hard linked linear guides (like what we do when clamping the X axis to the Y axis...) have no tolerance for variation in parallel at all. The best guides have an even LOWER tolerance for variation in parallel than the cheaper guides. Several of the manufacturers recommended that you machine perfectly parallel lips on the mounting plate at the inner edge of the two guides. Then you actually clamp the guides against the lips before screwing them into place. Apparently it is almost IMPOSSIBLE to drill holes in your plate accurately enough to keep parallel spec on the best guides. Since I did not use parallel lips, or even a mounting plate, I used cheap Chinese guides that have more forgiving tolerances and are more disposable. I suspect that YOU will be using sealed linear guides which have VERY tight tolerances and will probably require the lips.]]> patrickrio CoreXY Machines Mon, 30 Nov 2015 10:51:20 -0500 https://reprap.org/forum/read.php?397,589599,591024#msg-591024 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,591024#msg-591024
How can one end be shifted ? In a CoreXY the belts are in Push-Pull motion.
What a belt gives from one side, It realeases from the other side. It's a balanced system.
Imagine what should happen if you did not put the B belt at all.
Just nothing, even there's full tensioning for one side and none for the other.
I believe as long as no belt is frankly loose you won't have any issue.
If a belt is overtight, as long as the steps per mm are adjusted it will be ok.

Actualy My CoreXY is dismantled for painting, but I will check with two belts at different tension.
However I'm not sure both belts were tighten excactly the same way someday on it.
I did not noticed any shift from one axis.

++JM]]> J-Max CoreXY Machines Mon, 30 Nov 2015 08:26:46 -0500 https://reprap.org/forum/read.php?397,589599,591006#msg-591006 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,591006#msg-591006 the_digital_dentist CoreXY Machines Mon, 30 Nov 2015 07:48:05 -0500 https://reprap.org/forum/read.php?397,589599,590908#msg-590908 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,590908#msg-590908
I guess the_digital_dentist is affraid about belts stretching, not belt resolution (if it's the proper word).
This fear comes for the technical chart of the belt showin "max stretch xx%".
So people think about belts as a bungee thing, what obviously it is not.
Belt stretching appears mostly when the tensioning is close to the rupture.
And it's relatively even as the load/tensioning is stable.

On my CNC mill I drive a 120kg (260lbs) gantry with belts and I reach a repeatability within 0.03mm.
Not bad for 3500mm belts, what do you think ? ;)
You need a very expensive ballscrew to reach the same precision.
There's no secret, you just have to select the right belt for the application.

++JM]]> J-Max CoreXY Machines Mon, 30 Nov 2015 03:31:14 -0500 https://reprap.org/forum/read.php?397,589599,590809#msg-590809 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,590809#msg-590809
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the_digital_dentist
With a delta, it seems the only tricky/critical alignment is setting the guide rails parallel.

Metal corners help a lot to avoid leaning towers in my experience. I don't use guide rails, I use wheeled carriages running on the outside of the extrusions. So I just need to get the extrusions perpendicular to the base - and of course the extrusions need to be straight.

Quote
the_digital_dentist
...But then there's the loooong belts...

The belts in my delta are nearly 2m long each, but I can jog the head vertically in steps of 0.025mm (four 1/16 microsteps) without difficulty. That's good enough IMO.]]> dc42 CoreXY Machines Sun, 29 Nov 2015 17:07:33 -0500 https://reprap.org/forum/read.php?397,589599,590795#msg-590795 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,590795#msg-590795
With a delta, it seems the only tricky/critical alignment is setting the guide rails parallel. The bed can be adjusted so that it is orthogonal to the rails. The effector rods can be made identical lengths pretty easily. But then there's the loooong belts...

Hmmmm.]]> the_digital_dentist CoreXY Machines Sun, 29 Nov 2015 16:24:45 -0500 https://reprap.org/forum/read.php?397,589599,590017#msg-590017 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,590017#msg-590017
Sure stretch is very low, but more important, the resistance is very high,
the manufacturer says 6 times better than standard HTD.
That means you can use smaller belts that runs faster and weight less.
On my CNC I replaced HTD5M 15mm buy HTD3M GT3 5mm which can hold more torque !
Through, it's the best quality of belts I've ever seen, and it is incredibly quiet.

++JM]]> J-Max CoreXY Machines Fri, 27 Nov 2015 15:10:23 -0500 https://reprap.org/forum/read.php?397,589599,589910#msg-589910 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,589910#msg-589910
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J-Max
Hi guys,

...
May I suggest you consider HTD GT3 belts ?

++JM

Hey, why would GT3 be better? Less stretch?]]> LarsK CoreXY Machines Fri, 27 Nov 2015 11:24:42 -0500 https://reprap.org/forum/read.php?397,589599,589891#msg-589891 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,589891#msg-589891
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LarsK

This is not correct. If DC42's does 500mm at 1m tall then to do another 500mm he just makes it 1.5m tall.

Then it still falls within the range I specified of "1.5 to 2.0 meters".

Note that dc42 only claims 540mm build height in the middle-- for true wall-to-wall build height of 1000mm, more height is needed.

As he says, for true 300x300 square build area, again, more height is needed.

I like deltas-- up to a certain point, they're EASIER to get build height out of, and certainly you can build a delta that tall-- but for a full 300x300x1000, coreXY is probably going to be an easier solution to build.]]> grat CoreXY Machines Fri, 27 Nov 2015 10:33:09 -0500 https://reprap.org/forum/read.php?397,589599,589867#msg-589867 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,589867#msg-589867
Your project will be probably one of the most interesting of the coming year.
I'm very excited to see how you will apply or change your previous building principles for this one.

The lenght of the Z axis on a Core XY is not a factor.
It's just a question of guide lenght and orverall strucrue IMHO.

I see no advantages to use a Quadrap system.
4 motors for 2 axis is 2 motors waisted, and an risk of getting out of synchronisation.
You can replace 2 motors by some dual shaft motors or rod transmission. To me it's a wrong good idea.
I feel the same about the ultimaker alike printhead which seems a waste of two more guides.

To me CoreXY is simply more pragmatic, it uses a reduced amount of components.
I believe it overtakes a delta by footprint and building area, with comparable performance and cost.

I know you have your own ideas about machine construction and strucrures.
But instead of using 2040 and metal corners, may I suggest you replace metal corners by just using 2080 for the stiles ?
To me, the rails should be 40x40mm for that height.
The use of a heavy material as pannels is probably a good idea to deal with vibrations on a tall machine.
I say that but maybe you do not want to print fast too. so vibrations should be limited.

May I suggest you consider HTD GT3 belts ?

I will follow your build with interest.

++JM]]> J-Max CoreXY Machines Fri, 27 Nov 2015 09:39:00 -0500 https://reprap.org/forum/read.php?397,589599,589760#msg-589760 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,589760#msg-589760
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LarsK
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grat

Delta's scale poorly, even more so when you're talking 1m Z axis-- My delta is 720mm tall, and has a build height of 280mm.

dc42's delta is 300mm diameter, 480-540mm print height, and is 1m tall. Best case, you're looking at 1.5-2.0 meter tall printer, and you're going to have to make the frame out of 2060 or something similar to get it to work. Even then, the bowden length would be pretty crazy (800-1000mm?).

This is not correct. If DC42's does 500mm at 1m tall then to do another 500mm he just makes it 1.5m tall. In height it scales 1:1. You are thinking about the bed diameter which scales different. You are correct that normal bowden would not be optimal but there are many work arounds for this. See this also

I wanted to mention that there is / was a printer on kickstarter not so long ago that came at least close to the specs (470x435x690) - This one maybe it can serve as an inspiration in parts.

To expand on this:

My delta has a round bed with a printable diameter of 300mm. If that is large enough for you, then to achieve about 1m print height you would need to increase the height by 0.5m as LarsK says. 2040 extrusion should be adequate if you use metal corners. The Bowden tube would have to be lengthened, but by somewhat less than 250mm because the head needs to go another 250mm up and another 250mm down relative to the extruder drive.

However, if you really do want a 300mm square print area, that imples a printable diameter of 424mm, so the diagonal rods would have to be lengthened by about 140mm and the printer would need to be about 1.64m high. This would be more of a challenge to get working well.]]> dc42 CoreXY Machines Fri, 27 Nov 2015 06:38:53 -0500 https://reprap.org/forum/read.php?397,589599,589753#msg-589753 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,589753#msg-589753
Quote
grat

Delta's scale poorly, even more so when you're talking 1m Z axis-- My delta is 720mm tall, and has a build height of 280mm.

dc42's delta is 300mm diameter, 480-540mm print height, and is 1m tall. Best case, you're looking at 1.5-2.0 meter tall printer, and you're going to have to make the frame out of 2060 or something similar to get it to work. Even then, the bowden length would be pretty crazy (800-1000mm?).

This is not correct. If DC42's does 500mm at 1m tall then to do another 500mm he just makes it 1.5m tall. In height it scales 1:1. You are thinking about the bed diameter which scales different. You are correct that normal bowden would not be optimal but there are many work arounds for this. See this also

I wanted to mention that there is / was a printer on kickstarter not so long ago that came at least close to the specs (470x435x690) - This one maybe it can serve as an inspiration in parts.]]> LarsK CoreXY Machines Fri, 27 Nov 2015 06:11:59 -0500 https://reprap.org/forum/read.php?397,589599,589651#msg-589651 Re: CoreXY vs Quadrap mechanism https://reprap.org/forum/read.php?397,589599,589651#msg-589651 [3dprintingindustry.com]
What you need to do is just building a XY drawing platform which can draw 300mm X 300mm and make the whole platform which can lift up and down. Both CoreXY or Quadrap system can achieve this purpose too.]]> bunbun CoreXY Machines Thu, 26 Nov 2015 23:43:26 -0500