Prusa style vs CoreXY

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dan3008
Posts: 34
Joined: Sun Jul 09, 2017 4:52 pm

Prusa style vs CoreXY

Post by dan3008 » Tue Sep 19, 2017 4:49 pm

Hi guys

I've designed both a coreXY and prusa style 3d printer.
My main focus was, I want interchangeable hotends, Dual Extruders, and a large (300mm*250mm minimum) print bed.

Still cant decide on the design i'm going for... So I wondered if anyone can offer any advice. Maybe if you've had both before?
As far as I can tell, the bigest differences are:
Prusa style are cheaper
corexy are more study and faster

anyone got anything else to add to that?
Before anyone suggests a CR 10. I know, but 2 things, 1 I want to build it myself (works out cheaper anyway) and 2, I have a lot of electronics gift cards I can use at a lot of palces, but nowhere that sells CR 10's

Tsunamijuan
Posts: 21
Joined: Mon Jun 19, 2017 5:34 pm

Re: Prusa style vs CoreXY

Post by Tsunamijuan » Thu Sep 21, 2017 3:34 am

I think one of the important things you need to think about is how big of a print volume you want, and how fast you want to print.

I personally have never been a fan of the Prusa style design. Now Josef and others have Done amazing work to minimize the flaws of it and create great prints. But Moving both the bed with your print on it is something of a problem in my book. Not to mention with the size of steppers and commonly used and as volume of objects increase there are increased problems with this design. I have also found that there is just generally to much wobble the design in general. You can obviously build more solid versions, but you never fully get around these problems.

Another problem that comes with a moving bed with additive manufacturing is Z wobble. If your printing something that becomes very tall, and makes use of a large amount of Z volume you tend to see more artifacting and less accuracy in these areas. Its even worse if your printing something with a narrow base as it will tend to flex more while printing on these printers. (again you can calibrate it out to a certain degree, but things like filament thickness issues will make this even more difficult to remove from the equation. This problem admittedly isn't exclusive to the Prusa Design, but it made worse on it.

I would say the biggest thing with the Prusa design is simplicity and ease of understanding the design. Not to mention a massive abundance of parts. There are so many clones and mods that its easy to find parts to just bash together to try if your current design doesn't work. Its also very easy on the electronics.

Lets move on to CoreXY

There is a compression effect to core XY printers, This is what can cause a large amount of problems for these printers as the size goes up. Its made even worse if you use cheap non reinforced belts. As you will be forced to massively increase the tension on the belts to make up for the stretching. Additionally if your not reinforcing the frame as you increase the print volume the twisting effect becomes more of a problem. You can get around this by increasing the size of structural components so they resist these forces more. But the larger you push the print volume the ability to obtain quality parts, and inexpensive parts becomes more of a problem. Lets face it we are all on a budget. If you start spending 100$ a ground rod and need 16 of them for your design. Your probably gonna have a budget problem.

One of the great advantages of the CoreXY though is that you can have an extremely low Hotend/Carriage weight. Its been proven that you can easily use composites or other commodity materials rather than ground rods to drop the weight and have great success while maintain a high degree of accuracy even as the print volume grows. Even if your only using light weight options for the Hotend/Carriage carrying axis. You can also use a design similar to what Ultimaker uses for their CoreXY design, and have a mix of hardware to limit the belt runs. (I am not 100% sure of the forces involved during this change though as they differ some from the traditional coreXY design outlined on CoreXY.com).

Additional things to think about-

Enclosure-

Are you planning on printing things that require an enclosure. Materials like ABS, NYLON, Or just really large parts. Are you in an area with an air conditioner blasting effecting print temps. Do you want to quiet the printer down cause your sleeping in the same room, or working in close proximity, or just generally annoyed by the sounds it makes. Core XY's are very easy to enclose, By the nature of their boxy shape. The Prusa Design, is gonna generally require you to put it in something, instead of just slapping a few panels on it. Again another materials cost Issue comes into play here.

Extruder type -

You can admittedly use A direct drive extruder with either of these designs. However if you start stacking multiple direct drive extruders. The coreXY design can have problems with this sooner in large volumes than the Prusa design. As the weight can more quickly become a problem.

If your using a Bowden system, or multi material Bowden the two are pretty much even.

Additionally -

Both designs are fairly forgiving to overall build mistakes and learning. You can be off on how well parts are cut and be out of square somewhat even, and still produce great quality and fairly accurate parts. Part of its the nature of 3'd printing. As long as things stay consistently off its easier. By consistently off I am referring to things like a tweak in the frame or not printing square to the bed. Inconsistent problems would be vibration related problems and flexing, or even problems experienced as the load on the bed increases and things like the bed or frame sag. Your not gonna be able to easily get around inconsistent problems without making changes somewhere.

Hopefully This helps, I could of thrown Delta in there even, But for a first printer i really would advise against it even more so with building it yourself.

dan3008
Posts: 34
Joined: Sun Jul 09, 2017 4:52 pm

Re: Prusa style vs CoreXY

Post by dan3008 » Thu Sep 21, 2017 7:34 pm

Tsunamijuan wrote:
Thu Sep 21, 2017 3:34 am
Hopefully This helps, I could of thrown Delta in there even, But for a first printer i really would advise against it even more so with building it yourself.
Thanks Tsunami, a lot of really useful information there :)

Although, I forgot to mention in my first post, this isnt my first printer ;)
I've already got a Prusa clone (that i built myself) Now I want to build one with a bigger build bed (300*250mm ish), dual extruders, and a bed levelling probe.

I had considered a delta, and indeed, I'd love to make a delta, but for the size im looking at, I decided against it. I know some people (Russ from RWG research) have built ridiculously big delta printers, but personally, I'm not quite up for that challenge yet lol.

speed is less of an issue, but obviously faster is better.

Tsunamijuan
Posts: 21
Joined: Mon Jun 19, 2017 5:34 pm

Re: Prusa style vs CoreXY

Post by Tsunamijuan » Thu Sep 21, 2017 10:29 pm

I just kind of automatically assume lately that most of the posts about building printers are often by people that have never used one. As theres a large percentage lately that this is true for. A large number of the people that are experienced with 3d printing seem to already understand alot of the advantages and disadvantages of designs after a short while of use too.

I agree with you about large deltas. I was planning to build a larger delta however you consume a lot of space due to the arms. So for a large format printer I would of likely been looking at 8' feet tall.

bed leveling probes are nice, but honestly they can be just as much of a nightmare when they don't work right.

You can use FSR (force sensitive resistors) on other designs too if your using a composite bed or want to avoid magnetic sensors. Its fairly common to see them on delta's. But keep in mind a heated bed changes their sensitivity a ton. Plus they can be odd in how they trigger.

Do you have a coreXY design already or building it around another open source design?

dan3008
Posts: 34
Joined: Sun Jul 09, 2017 4:52 pm

Re: Prusa style vs CoreXY

Post by dan3008 » Thu Sep 21, 2017 11:47 pm

Tsunamijuan wrote:
Thu Sep 21, 2017 10:29 pm
I just kind of automatically assume lately that most of the posts about building printers are often by people that have never used one. As theres a large percentage lately that this is true for. A large number of the people that are experienced with 3d printing seem to already understand alot of the advantages and disadvantages of designs after a short while of use too.
too true... while I have experience with my Prusa clone, thats about it. and without having compared it to, its quite difficult to work out the pro's and cons. To be honest, If it was totally just my experience, apart from the hard time levelling the bed, I'd have said it was the best printer ever lol. But since I want to change things, clearly i cant even agree with myself lol...
Tsunamijuan wrote:
Thu Sep 21, 2017 10:29 pm
You can use FSR (force sensitive resistors) on other designs too if your using a composite bed or want to avoid magnetic sensors. Its fairly common to see them on delta's. But keep in mind a heated bed changes their sensitivity a ton. Plus they can be odd in how they trigger.
I'll look into that an an option :)
Tsunamijuan wrote:
Thu Sep 21, 2017 10:29 pm
Do you have a coreXY design already or building it around another open source design?
yes and no... the design I've got so far is based on an older coreXY plotter I have, which I didnt use much. Other than that, I've been looking a lot at the hypercube... So i understand how it works, i just havent actually used a corexy printer yet

Vertigo
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Joined: Mon Jul 31, 2017 9:00 am

Re: Prusa style vs CoreXY

Post by Vertigo » Fri Sep 22, 2017 1:28 am

dan3008 wrote:
Tue Sep 19, 2017 4:49 pm
1 I want to build it myself (works out cheaper anyway)
I certainly dont want to stop you from designing and building your own printer, but, if we're being honest, you're not likely to end up cheaper. If price was your main motivation, I would tell you to buy that CR10. But it will not give you the same satisfaction :).

Other than that, I dont have anything for you, I dont know the first thing about corexy.

dan3008
Posts: 34
Joined: Sun Jul 09, 2017 4:52 pm

Re: Prusa style vs CoreXY

Post by dan3008 » Fri Sep 22, 2017 11:13 am

Vertigo wrote:
Fri Sep 22, 2017 1:28 am
I certainly dont want to stop you from designing and building your own printer, but, if we're being honest, you're not likely to end up cheaper. If price was your main motivation, I would tell you to buy that CR10. But it will not give you the same satisfaction :).
Maybe not cheaper, but with all the gift cards I've been given to spend on bits and bobs, it sure does work out cheaper :)
And yeh, Satisfaction is another big motivator

Tsunamijuan
Posts: 21
Joined: Mon Jun 19, 2017 5:34 pm

Re: Prusa style vs CoreXY

Post by Tsunamijuan » Sat Sep 23, 2017 8:50 am

I would avoid the HyperCube Design if you can for a larger format printer. Even the Hypercube Evo which is stronger has the same flaw that the Hypercube has.

Let me explain, the X axis design for the hyper cube is a clone of the Prusa's X axis. The problem is that it doesnt get support in the same way on a CoreXY. While it does take less space by having the two rods vertical from each other. Because of the way the tension of the belts works. It causes a twisting in the axis. Its slight at small volume and low belt tensions. But once you increase the build volume and belt tensions it becomes very pronounced.

Your better off with having the rod/rails being on either side of of the nozzle. Similar to the design in the picture. In this setup the forces are aligned for less flexing and twisting. Also the nozzle is in the middle of the effected area. So any twisting from the belts not being 100% balanced either due to tension or stepping mistakes, get canceled out.
parallell horizaontal.PNG
parallell horizaontal.PNG (200.68 KiB) Viewed 9791 times
I was always skeptical of the original hypercube design it wasn't till actually trying it in person that I saw just how bad the X axis could be as the sizes increased.

While the amount of space consumed by the printer itself increases in this design. It shouldn't effect the cost much if you make use of Tslot or even Vslot. Infact Vslot is a great choice instead of using the ground Steel rods, as you push into the higher build volumes. Plus its easy to work as your design changes over time.

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lowfat
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Re: Prusa style vs CoreXY

Post by lowfat » Mon Sep 25, 2017 2:10 am

Do you have other suggestions for a CoreXY that uses 3030 extrusion for the frame? I've already ordered everything for a 300x300x500 Hypercube Evo w/ 'dual Z' (but was going to drive w/ a single motor to keep synced).

Tsunamijuan
Posts: 21
Joined: Mon Jun 19, 2017 5:34 pm

Re: Prusa style vs CoreXY

Post by Tsunamijuan » Mon Sep 25, 2017 10:03 am

lowfat wrote:
Mon Sep 25, 2017 2:10 am
Do you have other suggestions for a CoreXY that uses 3030 extrusion for the frame? I've already ordered everything for a 300x300x500 Hypercube Evo w/ 'dual Z' (but was going to drive w/ a single motor to keep synced).
I cant remember what size ground rod he uses for the evo is it 10mm or 12mm for the X axis? I could probably rebuild the design i am working on currently to use the rods. Its not to difficult It changes the dimensions a decent amount. but if you haven't cut anything yet its not a big deal. It also requires a rebuild of the Carriage but not a big deal.

Most of the frame hardware should mostly stay the same, the Idlers position changes some too.

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