Is CoreXY really better when compared to the i3 Cartesian styled machines? In this post, we'll attempt to give you an unbiased overview on the distinctive advantages of a CoreXY machine and the less-than-ideal disadvantages that an i3 Cartesian style machine has.
We will do it by discussing some of the prominent problems that people usually face and see how a coreXY machine can resolve some of the problems on an i3 style machine.
The movement mechanics of an i3 styled machine:
If you are not familiar with with an i3 styled machine is, the Prusa Mk3s, Creality Ender 3, Artillery sidewinder and many others are all considered i3 machines. They operate in a similar fashion which each axis is individually controlled.
In other words, when printing along the X axis, only X motor will work to move the hotend along the X axis. When printing along Y, only Y motor will work to move the heated bed (hotend remains stationary) along the Y axis.
Now that you understand how the X and Y works on an i3 machine, just imagine how X and Y works when it's lifted off the printing surface, layer by layer. In other words, Z motor individually controls the X axis gantry (heated bed remains on the same level)
The movement mechanics of a CoreXY styled machine:
If you are not familiar with a CoreXY machine, here is a very simple overview.
Just from the name itself, you may have guessed that at the core of a CoreXY machine, the X and Y motors work together to keep things moving. On the other hand, an i3 styled machine, we learn that all the axis are controlled individually.
And because the X & Y motors work together in a CoreXY, they're usually mounted on the same plane. This means they are not mounted away from each other, unlike an i3 styled machine.
As for the Z axis, instead of moving an entire X gantry upwards on an i3 styled machine, a CoreXY machine would lower the heated bed instead.
Now that you have a basic overview on how a i3 styled machine and a CoreXY machine work, let's take a look at a few common 3D Printing issues and how a CoreXY machine can provide a solution for them.
3D Printed Artefacts on Y Axis:
In an i3 machine, the heated bed get gets swung around along the Y axis. While it will appear that nothing can get seriously wrong with such a setup, it is not uncommon to see print artefacts along the Y axis when printing speeds get faster than ideal.
These artefacts happen because of the vibrations that get can get induced to the heated bed being swung to and fro, fast. While reducing jerk and acceleration will help, it is almost impossible to reduce the vibration and ringing (3D printing artefact) completely, unless of course you slow down the print speed.
So the heavier a heated bed on an i3 styled machine, the more induced vibrations you're going to see.
On the other hand, on a typical CoreXY setup, the heated bed does not get swung around. Instead, the heated bed only moves up and down as explained earlier on.
This means that regardless of your heated bed's weight, a heavy piece of glass as a printing surface or even printing a 100% infill mandalorian helmet should not induce noticeable ringing effects on your printed part.
So on an i3 design, regardless of the weight of the heated bed, you cannot eliminate ringing unless you print slow (45-70mm/s).
But on a CoreXY, you can comfortably print 90mm/s without noticeable rings since the bed doesn't move.
Z Wobbles & Layer Inconsistencies
In an i3 machine, the Z motor is actually responsible for lifting the hotend, layer by layer as the slicer sets it to print. However, this is far from the truth as the Z motor doesn't just lift the hotend but the entire X axis as well.
That means that as the layer height increases (the taller your print), the higher your entire X Axis would be and the X axis doesn't just include the hotend. It includes the weight of the extrusion, the bolts and nuts, the hotend & if you have direct drive, the extruder motor as well.
Now imagine this; As your X gantry gets higher, the more unintended vibrations the machine is going to produce. These vibrations will then have to be transferred somewhere. In this case, it gets transferred to your hotend, and then your printed object.
If you cannot see the analogy, let us demonstrate with a flag pole.
There are 4 rectangles and from the bottom, we have green, yellow, blue and red.
The flag is only used as an example. Let's assume the flag is the load. In this case the load refers to the entire X gantry. Let's assume wind is the motor that keeps your X Axis moving.
Now the stronger the wind = the faster your motors move = the faster you print.
Image the flag in all the 4 different positions.
In the green position, it's near the ground where the pole is anchored on the ground. Usually, these are the first few layers where we watch the print like a hawk. Nothing goes wrong most of the time.
As your Z height increases, the load now moves to the yellow zone. You would feel vibrations on your extrusion should you lay your hands on it but it may not be enough to cause visible 3D printed artefacts on your print yet.
As it moves up higher, you approach the blue zone. This where if your printing speeds are fast, you may start seeing issues on the object you're printing. Unless your Z Axis are reinforced with Z supports; Most of time they do not come reinforced out of the box. You have to buy Z supports from 3rd party vendors.
As the Z height reaches the top and the same printing speed resumes, it is almost guaranteed that you will see wobbles. Wobbles bad enough to cause poor printing results and layer inconsistencies. Have a doubt?
Look at any flag on a flag pole on a windy day, even the toughest reinforced flag pole will still be shaking hard if it's only anchored on one end; on the ground.
Now let's take a look at a CoreXY machine and see how the design combats this problem.
As mentioned earlier on, both X and Y motors are mounted on the same plane to control both X and Y movements together. This means that these do not move or change Z height positions as the slicer requires it to.
And since the Z motor only moves the heated bed up and down, that means all of the motors can be mounted in place. In other words, there are no movements of any motors when the nozzle needs to move in the X, Y or Z direction. A Nema 17 motor can weigh up to 250 grams!
And since the motors are fixed, you can guess that the 3D printing plane is always the same as well. No up and down movements along Z (i3 styled design) and the only moving plane should be your heated bed.
And since your heated bed only goes down with the help of gravity, we mitigate and reduce unrequired vibrations as well. So keeping the moving mass's inertia down? Checked.
This means little-to-none visible Z wobbles should be seen on your prints!
We will like to say that CoreXY isn't something revolutionary. CoreXY was never made popular because some companies wanted to make 3D printers as affordable as possible and that was how the i3 design came about.
While it may appear that a CoreXY is superior in terms of 3D printing performance, it also comes with it's own set of problems as well.
There are more alignment work to do and more maintenance. Because there are more things that are moving, things also get worn out faster.
However amidst all these, a well assembled and tuned CoreXY machine will out-print and i3 machine at faster and higher speeds in any day.
Of course, there is nothing with i3 machines if you prefer to print slowly. But if you want something more out of your 3D Printer and have the desire to tune for better prints, then you definitely want a CoreXY machine.
If you have the Creality Ender 3 and have always wanted to try a CoreXY kit but not wanting to buy another machine, you may want to check out our KAY3D CoreXY Conversion Kit.
It includes everything that you need when to change your Ender 3 into a true and true CoreXY machine.