So… we will use a special motion system
In a CoreXY system, the gantry is mounted in a very special way. Motors are stationary and great speed and stability is possible.
The picture below shows a CoreXY implementation
On top you see motors A and B and these are fixed in position. On the left and right there is a linear rail (vertically) and on the blocks of these rails there is 1 extra rail mounted horizontally. For this machine we will use Chinese MGN12 rails and blocks.
You can also see 10 pulleys on this picture. These are
- 2 GT2 20teeth pulleys mounted on the stepper motors
- 6 GT2 20teeth idler pulleys (the lowest 6 on the picture)
- 2 GT2 smooth idler pulleys
The GT2 20teeth pulleys fit nicely onto the 5mm shafts of the stepper motors. By installing 1 straight up on motor A and another one upside-down on motor B we will create 2 belt planes (more info later)
Using this technique (of integrated bearings) you can just mount these easily on a pin and they’ll work like intended.
You also need 2 SMOOTH idler pulleys. These are mounted on the horizontal axis (the 2 upper pulley idlers) and have to be smooth because…. well… have a look at the schematic. These pulleys will not be on the toothed side of the gt2 belt but on the smooth side. Therefore, it is best to use smooth idlers for this.
This CoreXY system has some nice advantages.
First of all, the motors are stationary. So we also don’t have any problem with moving motor wires. This makes machine design a lot easier. Secondly, because the motors are not moving, the whole gantry becomes very lightweight. The only weight it will carry is 1 700mm MGN12 rail with block + the laser head (+- 40grams). Because of that lightweight gantry system, it is possible to move the laser head at very high speeds without a lot of inertia.
If you look again at the schematic above, you’ll notice 2 colors of gt2 belt. And yes… there are 2 different belt paths in CoreXY. If you would look in a horizontal position, then you’d see that the green belt is running a little higher than the red one (or the other way around). This is needed, because at the bottom of the schematic, the belts cross eachother.
Read more on the next page….. (navigation see below)