CoreXY for bed instead of extruder(s), for small printer? For a printer with a small printing area (for example 100x100mm) and more than one extruder, in your opinion would it make sense to have a coreXY to move the small bed and have the (direct) extruders lifted only vertically? https://reprap.org/forum/read.php?397,551578,551578#msg-551578 Tue, 14 Jul 2026 20:59:01 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?397,551578,606749#msg-606749 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,606749#msg-606749
Next, fast movement and resolution are difficult to achieve at the same time (due to flex of parts, resonances etc.). You would need a very stable and sturdy printer. If you are willing to sacrifice speed, you can build a printer with very good resolution without shelling out obscene amounts of money.

The pulleys also have slop. You can order zero backlash ones to increase precision.

I have a pulley belt system on my printer, effectively doubling the resolution and precision. It is not compatible with CoreXY, as far as I know.
Because the belt moves half the distance per revolution of the motor as compared to a direct belt system, the positioning error gets cut in half.
You can theoretically increase the number of idlers to achieve even higher precision.
Another effect is that you only need a fraction of torque to move your printhead. The disadvantages of the pulley system are longer belts, slower maximum speeds and more parts / higher complexity (but the parts should still be cheaper than a preloaded ball screw).
With a 0.9° stepper, 20 teeth GT2 pulley and 2* mechanical advantage pulley system, I get 0.05mm / full step. Positioning error due to stepper repeatability alone would be (0.05mm * 0.05) / 2 = +-0.00125mm. Of course, you have to factor in tolerances of other parts, too.
The precision at the moment sucks, though, because I seriously really should retighten everything and recalibrate my printer, lol.]]> uGen CoreXY Machines Fri, 08 Jan 2016 13:05:53 -0500 https://reprap.org/forum/read.php?397,551578,584773#msg-584773 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,584773#msg-584773
Quote
J-Max
I will watch carefully to use proper terms in the future ;)

Me too :)]]> cristian CoreXY Machines Sun, 15 Nov 2015 17:14:42 -0500 https://reprap.org/forum/read.php?397,551578,584637#msg-584637 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,584637#msg-584637
No problem mate, you're right, many terms are confusing for unskilled people.
I will watch carefully to use proper terms in the future ;)

++JM]]> J-Max CoreXY Machines Sun, 15 Nov 2015 11:27:27 -0500 https://reprap.org/forum/read.php?397,551578,584592#msg-584592 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,584592#msg-584592
Many people, including native English speakers, often misunderstand the meanings of and misuse the terms I was explaining. When you get down to tens of microns, they all get jumbled together and hard to separate.]]> the_digital_dentist CoreXY Machines Sun, 15 Nov 2015 09:38:21 -0500 https://reprap.org/forum/read.php?397,551578,584573#msg-584573 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,584573#msg-584573
Delta have uncontinuous resolution, depending of distance of the effector from the pillar.
At the centre you have less resolution.



Anyways, whatever the architecture of the machine is, you can increase by any mecanical process
the number of steps per millimeter of your printer.
But, as I said above, you will be quickly limited by the FDM technology.
Even with a 0.1mm nozzle, 0.025 layers, and 0.001mm per step,
you will of course be able to print more details,
I can't remember if anybody pushed the resolution that far,
but I guess you will soon reach soon the limit of the technology.
I belive you will never be able to reach a 0.1mm precision on the part.

@the_digital_dentist, please appreciate english is not our first spoken language. (probably you could already guess)
Sorry if we look to don't understand the difference and we use a word instead of another sometimes.
Maybe you can trust us enough to understand that we make the difference in our mother language.
But feel free to tell us when we say something with the wrong word, it will help us to make ourselves more understandable. ;)

++JM
]]> J-Max CoreXY Machines Sun, 15 Nov 2015 08:24:53 -0500 https://reprap.org/forum/read.php?397,551578,584556#msg-584556 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,584556#msg-584556
Quote
the_digital_dentist
I think that some of you guys are confusing precision, minimum feature size, minimum step size, resolution, and accuracy.

Thanks for the clarification. My objective is then getting the best resolution for a small bed printer.

Quote
VincentM
Quote
cristian
For a printer with a small printing area (for example 100x100mm) and more than one extruder, in your opinion would it make sense to have a coreXY to move the small bed and have the (direct) extruders lifted only vertically?

Not a CoreXY, but a Delta:
[www.diyouware.com]

Interesting. Does this give better resolution than a coreXY?

Quote
bunbun
As your title CoreXY for bed instead of extruder, for SMALL PRINTER. For me, it is talking about designing a small printer that in moving bed. Not a moving small bed printer.

My fault, what I meant was "small bed printer". It is indeed true that if the bed is moving, the printer itself will be much bigger than the printing volume.]]> cristian CoreXY Machines Sun, 15 Nov 2015 07:43:26 -0500 https://reprap.org/forum/read.php?397,551578,583812#msg-583812 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,583812#msg-583812 bunbun CoreXY Machines Thu, 12 Nov 2015 22:45:22 -0500 https://reprap.org/forum/read.php?397,551578,583414#msg-583414 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,583414#msg-583414
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bunbun
Main problem of moving bed instead of moving extruder is space efficiency. When you design a printer with moving bed, you need at least 4X bed surface area for bed movement.
Let say you designing a printer with print size 100X100X100 by moving bed. Then your printer size will be at least 250X250X250 (bed movement plus bearing, motor, etc.).
In same case, if you design it in moving extruder mode. Then your printer size can be controlled in 200X200X200.
If the printer be enlarged to a bigger size, the different will be enlarged dramatically.

How is it a MAIN problem? Getting longer aluminium extrusion and higher quality linear guiding system is not a problem.
You can mount a bed above the belts and motors to save space.
And it is not like a printer has to fit in a limited space next to the other components. So there is zero problem in this.

And if one wants a large bed then moving it is not a good decision and that is not what this thread is about. Red the subject of the thread where small bed is mentioned.]]> Edvardas CoreXY Machines Thu, 12 Nov 2015 06:22:34 -0500 https://reprap.org/forum/read.php?397,551578,583302#msg-583302 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,583302#msg-583302 Let say you designing a printer with print size 100X100X100 by moving bed. Then your printer size will be at least 250X250X250 (bed movement plus bearing, motor, etc.).
In same case, if you design it in moving extruder mode. Then your printer size can be controlled in 200X200X200.
If the printer be enlarged to a bigger size, the different will be enlarged dramatically.]]> bunbun CoreXY Machines Wed, 11 Nov 2015 22:41:21 -0500 https://reprap.org/forum/read.php?397,551578,583157#msg-583157 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,583157#msg-583157
Quote
cristian
For a printer with a small printing area (for example 100x100mm) and more than one extruder, in your opinion would it make sense to have a coreXY to move the small bed and have the (direct) extruders lifted only vertically?

Not a CoreXY, but a Delta:
[www.diyouware.com]]]> VincentM CoreXY Machines Wed, 11 Nov 2015 13:00:11 -0500 https://reprap.org/forum/read.php?397,551578,580830#msg-580830 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,580830#msg-580830
My printer has a 400 um nozzle, which limits the minimum feature size that is printable. That is easily modified by changing the extruder nozzle.

Accuracy is a measure of how close the print is to the design size. If you tell the printer to draw a 4mm long line, does it come out 4mm long? In the picture of the calibration cube from my machine a few posts up, the designed size was 100 mm and the printed size was 99.89 mm. That was printed before final calibration (that's what printing the cube is for).

Precision is the ability to hit the same coordinates over and over (such as the corners of a cube) and has nothing to do with the accuracy or minimum step size of the printer. The effect of imprecision in the X and Y axes is for layers to be slightly misaligned which is ultimately a surface quality issue unless the machine is grossly imprecise. The effect of Z axis imprecision is variations in layer height that can likewise show up as a surface quality problem. Thinner layers will be squished wider and thicker layers will be narrower. Here is a photo of the edge of one corner of that same calibration cube (they all look like this one) which was printed in 250 um layers:



This picture was taken with my cell phone camera coupled to a microscope. The camera has some pincushion distortion that makes the center portion of the print appear to sag, but that is strictly an optical effect that does not exist in the actual print. If the precision were poor you would see the layers not stacking up so nearly perfectly, looking like a miniature version of Z axis wobble that we've all seen so many pictures of thanks to common use of bent threaded rods and flexible guide rails and printer frames. I don't have a measurement of the precision exhibited by the positioners in my machine, but you can see from the picture that the deviation from a straight line drawn along the bumps at each layer is a tiny fraction of the layer height. I believe that my printer's precision is limited not by the mechanism but by minor variations in filament diameter that cause slight over and underextrusion that is indistinguishable from mechanical positioning error.

Here is a photo of the edge of the flutes on a vase (https://www.youmagine.com/designs/spiral-vase--2), a design which is a real printer precision torture test:



Minimum step size is what printer makers usually quote as "resolution" and is a function of the drive electronics and things like pulley diameters and screw pitches/leads. Resolution is actually the minimum distinguishable movement on the nozzle as seen in the print, and is limited by but not necessarily equal to minimum step size. If the minimum step size is 20 um in the X axis, can you see the difference in the print when plastic is put down on one layer at X=122.320 mm and the next layer is at X=122.340? Resolution could also be interpreted on a single layer- can you measure a difference between the lengths of a line that is supposed to be 100.000 mm long and one that is supposed to be 100.020 mm long?

The resolution can't be better than the minimum step size, but it isn't necessarily equal to the minimum step size either. Since we're talking about numbers in the 10s of microns range, everything has an effect including the basic precision and accuracy. If the machine can't put the nozzle at the target coordinate reliably, the resolution will be poorer than the minimum step size would indicate. Most printers with flexible frames, sloppy bearings, flexible guide rails probably have resolution that is much worse than their minimum step sizes. As rigid as my printer is, and as precise as its bearings are, I am pretty sure that my printer's resolution is likewise limited by the machine's overall precision which is in turn limited by the precision in the diameter of the filament. I have not tried to measure the resolution in my printer, but in case anyone is wondering, the steps per mm in the X, Y, and Z axes are 321.45, 1286.43, and 529.92 which by inversion translates to 3.11 um, 0.777um, and 1.89 um per microstep. I feel safe in saying that the overall resolution is worse than those step sizes would indicate, but I don't know how to accurately and precisely measure such small values, so we'll never know for sure.
]]> the_digital_dentist CoreXY Machines Fri, 06 Nov 2015 11:46:40 -0500 https://reprap.org/forum/read.php?397,551578,571626#msg-571626 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,571626#msg-571626
Quote
J-Max
Why not a XYbed ? It shoulld work anyways.

Well the idea (not necessarily a good one) was to have more than one direct extruder (no Bowden). In that case, a small bed may be lighter than the extruders with motors.]]> cristian CoreXY Machines Fri, 16 Oct 2015 18:11:10 -0400 https://reprap.org/forum/read.php?397,551578,571612#msg-571612 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,571612#msg-571612
Yep, I remember.
On a small printer, it realy does not matter.
I still don't think it's a good idea.
One of the more interesting thing about the CoreXY
is the still bed which moves only on the Z axis.
You want to move the lightest thing, because it's easyer and it can be fast.
Otherhand, moving beds always need some space to move.
If you want it small, you want the bed to move only on the Z axis.

Why not a XYbed ? It shoulld work anyways.

++JM]]> J-Max CoreXY Machines Fri, 16 Oct 2015 17:37:47 -0400 https://reprap.org/forum/read.php?397,551578,571046#msg-571046 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,571046#msg-571046
Quote
Edvardas
Have you considered a material to make a bed platform of? I tried to google hoping to find plenty of information on people using all kind of different materials on cartesian printers to lighten Y axis but came with nothing.
Aluminium-foam sandwich (dibond) came to my mind as it is light and stiff.

For a first prototype, I was thinking to stick to a classical cold glass bed. More ideas are welcome...

Quote
J-Max
The printing bed don't need to be light on a CoreXY printer.

better have a look at the subject of the thread then :)]]> cristian CoreXY Machines Thu, 15 Oct 2015 13:14:33 -0400 https://reprap.org/forum/read.php?397,551578,570923#msg-570923 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,570923#msg-570923
Dibond have some foam PVC inside.
It's not compatible with the heatbed.

6mm aluminium works great, or try some PEI plate.
The printing bed don't need to be light on a CoreXY printer.

++JM]]> J-Max CoreXY Machines Thu, 15 Oct 2015 07:47:51 -0400 https://reprap.org/forum/read.php?397,551578,570857#msg-570857 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,570857#msg-570857
Have you considered a material to make a bed platform of? I tried to google hoping to find plenty of information on people using all kind of different materials on cartesian printers to lighten Y axis but came with nothing.
Aluminium-foam sandwich (dibond) came to my mind as it is light and stiff.]]> Edvardas CoreXY Machines Thu, 15 Oct 2015 06:24:12 -0400 https://reprap.org/forum/read.php?397,551578,570318#msg-570318 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,570318#msg-570318
Quote
J-Max
A DLP printer (resin printer with video projector instead of SLA -laser)
can be achieved at reasonable price, because there's only one axis, one guide.
You just need to find one way to project any UV image.
There's a lot of inexpensive examples on the DIY community.
Definitely, for jewelry or precision figurines, you want a resin printer.

I think you are right. Thanks for the link, I didn't know SLA printers were so cheap to build (although resin is not so cheap). The problem is that nowadays there are very nice plastic filaments for FDM (wood, metal, all kinds of flexible filaments, etc.) but not so much for SLA (and many resins are quite expensive). Moreover, I have been told that some of them are very sensitive to light even after curing: the surface becomes quite ugly over time. Finally, I don't know how brittle resin objects are.

Quote
J-Max
The values are estimated.
Some calculators are less optimist than me : [nathan7.eu]

There is no mention of precision in that page. If you refer to the extrusion diameter or the smallest printable feature, this is definitely not a measure of precision (in itself).

Quote
J-Max
Fluctuations are mostly stable, you can feel them by the touch but you can't eyeball it.
But it exists. IMHO, to have some very precise mecanics won't help over 100µ.
You won't notice any improvement because of the filament thing.

Probably you are right, although 100µ would be way better than the precision of my current printer. :)

Quote
J-Max
Some people believes in a heavy structures and precise guides for 3D printing.
For example the_digital_dentist's son of megamax..
His machine is very good and pretty interesting too.
Otherhand, some light machine can achieve close results with less precise/expensive components.
Please note, the son of megamax printer don't reach 50µ precision,
even if that eperienced repraper has come as far as possible with components/expenses. ;)

the_digital_dentist has influenced a lot my understanding of 3d printing. :)
His machine is quite big, I would not expect it to reach 50µ precision. On the other hand, a very small machine built with the same philosophy may have better chances.]]> cristian CoreXY Machines Tue, 13 Oct 2015 17:25:26 -0400 https://reprap.org/forum/read.php?397,551578,570086#msg-570086 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,570086#msg-570086
A DLP printer (resin printer with video projector instead of SLA -laser)
can be achieved at reasonable price, because there's only one axis, one guide.
You just need to find one way to project any UV image.
There's a lot of inexpensive examples on the DIY community.
Definitely, for jewelry or precision figurines, you want a resin printer.

The values are estimated.
Some calculators are less optimist than me : [nathan7.eu]
Fluctuations are mostly stable, you can feel them by the touch but you can't eyeball it.
But it exists. IMHO, to have some very precise mecanics won't help over 100µ.
You won't notice any improvement because of the filament thing.

Some people believes in a heavy structures and precise guides for 3D printing.
For example the_digital_dentist's son of megamax..
His machine is very good and pretty interesting too.
Otherhand, some light machine can achieve close results with less precise/expensive components.

Please note, the son of megamax printer don't reach 50µ precision,
even if that eperienced repraper has come as far as possible with components/expenses. ;)

++JM
]]> J-Max CoreXY Machines Tue, 13 Oct 2015 09:53:22 -0400 https://reprap.org/forum/read.php?397,551578,570027#msg-570027 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,570027#msg-570027
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dc42
I have no experience of CoreXY designs, but I am guessing that stretch in the long belts may be a limiting factor. If it isn't, or it can be overcome, then I think you should be able to achieve better than 50um resolution (but not accuracy) in the XY plane. You may need to use 0.9deg/step motors to get higher incremental torque, and small enough pulleys to get a high steps/mm factor.

Belts stretch is one of my main concerns indeed. My suspect is that in most of printers the precision of the positioning system is in general much worse than its typical resolution. This is what I see in my printer at least, where I have a micro-step resolution on the horizontal plane of about 13µ (if I remember correctly), while I can say by eye that the overall precision can't be better than something like 300µ (and I am not talking about the worst case...). Somehow such a high resolution is wasted: I could probably disable micro-steps and get equivalent results, besides a fancier surface look caused by small ridges on the external perimeters.

A more stable structure in my case would definitely help. But still it would be interesting to know what are the real limits of belts, given a reliable printer structure. I started making some measurement to be able to calculate at least an order of magnitude for that (excluding backlash given by teeth, if present), we'll see if I get somewhere.]]> cristian CoreXY Machines Tue, 13 Oct 2015 07:40:01 -0400 https://reprap.org/forum/read.php?397,551578,570016#msg-570016 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,570016#msg-570016
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J-Max
You can't reach your model's dimensions within 10µ with a FDM printer.

:(
I am becoming aware of that...

Quote
J-Max
It's not depending of the mecanics, but of the fused filament technology itself.
There's an aleatory factor with fused filament.
You need to squeege the filament on the previous layer to make a good bond.
So, if you have a 250µ nozzle maybe your filament path will be +-275µ
depending of various factors, like speed, vibrations, heat variation,
fused filament expansion, and many little random parameters.

If we are talking about the worst case, I totally agree (still wondering where you get those numbers :) ).
However the "average case" can't be so bad, otherwise nobody could obtain decent surface look at layer height lower than 0.5mm.
In my opinion, several printers+slicers can obtain an overall precision of 100µ or better if you do not consider the most critical points or conditions (sharp corners, retraction points, etc.).

In any case, the worse the precision of the positioning system, the worse will be the overall precision including filament extrusion. So having a precision of 10µ for mechanics, if achievable, would be already a fantastic starting point and I would be very happy with that.

Powder printing is interesting, but it seems to me less feasible at the moment (not considering industrial products of course).
SLA gives wonderful results but it is out of my budget, and I don't know how delicate are the printed objects and their surface.

Quote
J-Max
Just a question Christian, what is that printer for ?

Well, officially for small plastic jewelry. In reality, it is my personal crusade to get the best precision out of homemade (or home-assembled) FDM technology given a reasonable budget (which is not 300€, but not even 2000€).]]> cristian CoreXY Machines Tue, 13 Oct 2015 07:12:34 -0400 https://reprap.org/forum/read.php?397,551578,569802#msg-569802 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,569802#msg-569802
Quote
cristian
Quote
dc42
You can often get better resolution than 150um in the Z direction from an FDM printer, but not usually in the X and Y directions, because the extrusion width is typically about 400um.

The problem for me is not just the resolution. It is true that details smaller than 400µ cannot be printed with a standard nozzle, but if the positioning system allowed a precision of 10µ along X and Y, then a vertical wall printed at 50µ layer height would really look good, even if the layer width is 400µ. Conversely, with a precision ( ~= repeatability) of 150µ, a vertical wall printed at 50µ looks horrible independently of the chosen layer width I think.

My delta printer has a resolution of better than 25um in the Z direction (i.e. I can move it in 25um Z steps and detect that it moves - I haven't tried smaller steps), which means it should be around 12um in XY. At present there is some backlash in some of the Traxxas joints that spoils the XY resolution in some prints, but I should be able to overcome that.

I have no experience of CoreXY designs, but I am guessing that stretch in the long belts may be a limiting factor. If it isn't, or it can be overcome, then I think you should be able to achieve better than 50um resolution (but not accuracy) in the XY plane. You may need to use 0.9deg/step motors to get higher incremental torque, and small enough pulleys to get a high steps/mm factor.]]> dc42 CoreXY Machines Mon, 12 Oct 2015 18:46:15 -0400 https://reprap.org/forum/read.php?397,551578,569781#msg-569781 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,569781#msg-569781
Well, I gess there's missunderstanding between resolution and precision.
Resolution is what the printer theoricaly can give.
Precision is what the part is compared to it's virtual 3D model.
You can't reach your model's dimensions within 10µ with a FDM printer.

You need a damn good SLA or Powder printer to get close to that !

It's not depending of the mecanics, but of the fused filament technology itself.
There's an aleatory factor with fused filament.
You need to squeege the filament on the previous layer to make a good bond.
So, if you have a 250µ nozzle maybe your filament path will be +-275µ
depending of various factors, like speed, vibrations, heat variation,
fused filament expansion, and many little random parameters.

On a SLA printer, the path is created by a laser, which is thinner than any FDM nozzle.
If you use a quality laser module properly focused, then you get much better results.
Theres some light diffusion in the resin, but it smooths the parts edge.

There's an example of a good FDM print :


And now an example of a good SLA print :


Just a question Christian, what is that printer for ?

++JM
]]> J-Max CoreXY Machines Mon, 12 Oct 2015 17:36:33 -0400 https://reprap.org/forum/read.php?397,551578,569780#msg-569780 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,569780#msg-569780
Quote
cristian
Quote
J-Max
A single 300mm C0 ballscrew is more expensive than most of the reprap kits.

If it worked well, the price may even be fine with me

After seeing the price for a preloaded C3 ball screw from Misumi I am no longer so sure that it is fine...]]> cristian CoreXY Machines Mon, 12 Oct 2015 17:30:43 -0400 https://reprap.org/forum/read.php?397,551578,569771#msg-569771 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,569771#msg-569771
Quote
dc42
You can often get better resolution than 150um in the Z direction from an FDM printer, but not usually in the X and Y directions, because the extrusion width is typically about 400um.

The problem for me is not just the resolution. It is true that details smaller than 400µ cannot be printed with a standard nozzle, but if the positioning system allowed a precision of 10µ along X and Y, then a vertical wall printed at 50µ layer height would really look good, even if the layer width is 400µ. Conversely, with a precision ( ~= repeatability) of 150µ, a vertical wall printed at 50µ looks horrible independently of the chosen layer width I think.]]> cristian CoreXY Machines Mon, 12 Oct 2015 17:10:51 -0400 https://reprap.org/forum/read.php?397,551578,569761#msg-569761 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,569761#msg-569761 dc42 CoreXY Machines Mon, 12 Oct 2015 16:55:14 -0400 https://reprap.org/forum/read.php?397,551578,569756#msg-569756 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,569756#msg-569756
Quote
J-Max
Christian, you can't reach a 10µ precision with any FDM printer IMHO.
The best you can expect is +-150µ. You'd rather look at SLA or DLP printers.

Okay, now I am starting to understand what you expect from a fdm printer and why belts are fine in your opinion.
I think that in some cases repeatability can be better than 150µ, otherwise nobody may really get good perimeters at 200µ layer height. But in general I agree that most printers cannot achieve much better than that (I suspect that my current printer is worse, actually).

Quote
J-Max
A single 300mm C0 ballscrew is more expensive than most of the reprap kits.

If it worked well, the price may even be fine with me (and 120mm ballscrew would be enough for the small printer I am trying to build). But wouldn't it be too slow then?]]> cristian CoreXY Machines Mon, 12 Oct 2015 16:50:40 -0400 https://reprap.org/forum/read.php?397,551578,569560#msg-569560 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,569560#msg-569560
Christian, you can't reach a 10µ precision with any FDM printer IMHO.
The best you can expect is +-150µ. You'd rather look at SLA or DLP printers.

A 10µ precision printer is obviously expensive.
Only C0 preloaded ballscrews allow that kind of transmission precision.
A single 300mm C0 ballscrew is more expensive than most of the reprap kits.
You must be very precise when building and squaring the machine too !

Look at first quality manufacturer's printers,
and if you find a 10µ capable machine, look at the retail price ;)
That's what we're talking about here.

++JM]]> J-Max CoreXY Machines Mon, 12 Oct 2015 10:49:05 -0400 https://reprap.org/forum/read.php?397,551578,569277#msg-569277 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,569277#msg-569277
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J-Max
Christian, what precision would you expect ?

For my needs, accuracy is probably not as important as precision, reason why aluminium profiles may work for me as well. On the horizontal plane, I would like to print reliably at 0.25 mm layer width, while vertically I would like to reach 0.05 mm layer height, which is the main limiting factor. I guess I am looking for precision in the 10 micron scale then?]]> cristian CoreXY Machines Sun, 11 Oct 2015 16:15:14 -0400 https://reprap.org/forum/read.php?397,551578,569251#msg-569251 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,569251#msg-569251
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Ryan_M
Hey guys, I'm not an engineer or anything so I'm hoping you can clear something up for me as I'm following along... Why are belt tensions being expressed as a torque value in Nm? Wouldn't a belt under tension strictly be a one dimensional force that should just be in N? Sorry if this is a dumb question.
I realy don't know. Maybe it's because of motion and speed while N is for a still mass ?

Chrstian, I got that values from manufacturer's specs.
FDM technology allows some kind of precision,
but you can't reach extreme precision too.
V-slot and belt drives fits the precision FDM can provide.
Christian, what precision would you expect ?

++JM]]> J-Max CoreXY Machines Sun, 11 Oct 2015 15:18:45 -0400 https://reprap.org/forum/read.php?397,551578,568546#msg-568546 Re: CoreXY for bed instead of extruder(s), for small printer? https://reprap.org/forum/read.php?397,551578,568546#msg-568546
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J-Max
Un nordiste... Bon, on te garde quand même... ^^

Les Chti sont sympa, oui, mais moi, je suis pas Chti, je suis Italien !

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J-Max
Christian, don't be affraid about the belts. Belts are not elastic stuff.
Stretch values of 0,4% max are in extreme issues, just before beaking.

Then I guess the belts of my printer are quite low quality: I can easily stretch them about 1.5% and I am far from breaking them.
I have no idea of their origin (they came in a kit). Where did you get info about 0.4% max elongation?

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J-Max
A GT2 6mm quality belt allows 120Nm !
You won't get the quarter of that on your printer, even with preload or friction.

I don't know how to interpret N*m, I would expect newton only in this context, since belt dimensions are given.
And I don't know how to explain my concerns further: the problem is not the maximal elongation of the belts, but the displacement caused by perturbations along the belts, which consist in accelerated and decelerated loads, friction, etc. This article is an interesting read, although lacking a lot of info about the setup they used.

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J-Max
You should consider the V-slot technology too.
That guides are quiet and very sturdy too.

Aluminium profiles are usually not guaranteed to be really straight. I know that "in practice" they are straight "enough" for most purposes, but maybe not for the precision I hope to achieve (or maybe yes, who knows?).]]> cristian CoreXY Machines Fri, 09 Oct 2015 13:33:14 -0400