Corexy max build volume

moe.adams9093

Hello I have a question can a Corexy machine go up to 500x500 and maintain good print quality . I heard that Corexy max can do only 350x350.

Phaedrux

It would depend on construction and design more than any fundamental of corexy itself. The long belt runs and higher moving mass would be a limiting factor. But at 500x500 you think you'd be printing large objects and would be using a large nozzle, so high print speeds wouldn't be as much of a requirement, neither would "good print quality" perhaps.

deckingman

Mine is 400 X 400 X 900 with a frame that is 600 X 600 but there is no reason why it couldn't be 500 X 500. Moving mass on the XY gantry is about 1 Kg with the 6 input hot end fitted. The UV gantry carries 6 extruders and has a moving mass of about 2Kgs. I've demonstrated printing at 300mm/sec and my default non-print move speed is 350mm/sec. I once printed a coffee table out of taulman t glass (but not at 300mm/sec). So there is no fundamental reason why CoreXY is size limited.

jens55

@deckingman, that is most interesting. I too was thinking about corexy but was told that 300300 was about the maximum viable size due to belt stretch. I like the size of my current CR10-S5. Although most objects I print would fit a 300300, I really like the ability to print bigger.
Do you replace your belts on a regular basis or has it never been an issue ?

o_lampe

@jens55 said in Corexy max build volume:

@deckingman, that is most interesting. I too was thinking about corexy but was told that 300300 was about the maximum viable size due to belt stretch. I like the size of my current CR10-S5. Although most objects I print would fit a 300300, I really like the ability to print bigger.
Do you replace your belts on a regular basis or has it never been an issue ?

@moe-adams9093
With the soon to come acceleration-sensor and the already existing 'input shaping' ringing and resonance from long belts and smooth idler pulleys will no longer be a problem.

Don't go cheap on the belt. Gates GT2 belts are really a world of it's own (also price-wise). Use big diameter pulleys. (if possible run the smooth side of the belt or use GT2 idlers)

deckingman

@jens55 said in Corexy max build volume:

Do you replace your belts on a regular basis

No

or has it never been an issue ?

Correct - not an issue (even when throwing >1Kg around). Oh, and that's with 6mm belts. I had at one time considered using 9mm but as belt stretch isn't an issue using 6mm belts, there is no point.

I'm planning on doing some tests but my gut feel is that there may be some stretching when the belts are initially tensioned, but once tensioned, the incremental load applied in order to accelerate the hot end is not sufficient to cause any further stretching.

Edit. Taking my heavy 1Kg hot end as an example, and given that Force(N) - Mass x Acceleration, then using my default acceleration of 2000 mm/sec^2 we get a force of 1 x 0.2 = 0.2 Netwtons over both belts so about 0.1 Newtons per belt. Which I doubt would lead to any stretching once the belts have already been tensioned. And most hot ends weigh a lot less than mine and many people use a lot lower acceleration too.

engikeneer

@deckingman 2000mm/s^2 = 2m/s^2 so the results come out at 2N over both belts, 1N per belt.

Still pretty small though (about the weight of an apple!) so the conclusion is the same

zapta

Does input shaping make larger CoreXY more feasible?

In the Voron world, the recommendation is not to go beyond 350mm.

Luke'sLaboratory

@moe-adams9093
My largest machine sofar is 622x622x1000 - works great when the firmware works (comon 3.3beta3!)

Its definitely not optimized for low-mass gantry - i use a 2040 beam and its a toolchanger as well!

I don't print at insane accelerations on it - only 2kmm3/s, and the prints come out fine.

I have chosen 9mm belts, to minimize belt stretch.

Recommendations from my experience:
9mm Belts - Genuine Gates
Genuine Idlers
Metal Joints (sag just gets worse and worse the larger you go, so start with the best foundation)
Double shear everything - Motor Shaft, Idler Posts - (this will save alot of headaches from ghosting to actual idler failures)
Mass - Add some kind of damping or just generally increase the mass of the machine - a ~72lb paver stone made my prints alot better and prevented alot of shaking of the frame.

I built a 400x400 machine off of the same blueprint, and run that at 7k accel. My limiting factor is actually the TMC2209's limits of ~1.3A RMS on the D3 mini and the 24v PSU. The 60mm LDO motors aren't even warm yet. Once make an expansion board for 5160's and add a 48v PSU to it, I expect 10k accel.

This all being said -

My design is based off of being able to mount either a Jubilee REL head or the e3d TC head in an any-size configuration. if you were building just the fastest largest single-tool machine, I'd wholly recommend a CROXY design - They scale very well without dropping performance.

@zapta
Input shaping helps everything - it helps a small machine go even faster, or a big machine go faster.

moe.adams9093

Thanks all of you for the suggestions and recommendations.

fma

@moe-adams9093 I'm using 3mm pitch, 9mm width, Gates GT belt, to minimize stretching. Or maybe because I'm using motors/pulleys from an old Stratasys, which was using such belts? Mmm...

Serbitar

I have a 515mm x 515mm x 540mm build volume HevORT which is printing quite well. Mostly its for larger parts where accuracy is important but fine detail isn't critical.
Yesterday i was getting 200mm/s with PLA out of the volcano hotend.