Printing Cylinders with a Cartesian Printer

There will certainly be an occasion where you will want to print a cylindrical object with your 3D printer. You will have to decide how to orient the cylinder with respect to the Z axis.

With a Cartesian style printer the X and Y axes are horizontal and the Z axis is vertical.
*Side note - yes axes is the plural form of axis. 
If this sounds like your printer, you only have one good choice on how to orient your cylinder. Let me explain.

You can choose to print the cylinder so that the major axis is parallel with the X, Y, or Z axes.
Let's first consider X axis.
The cylinder will be laying on it's side like in the picture below.

The problem arises when you slice your model. The cylinder becomes 'pixelated'. The larger the layer height, the lower the 'resolution' of your pixelated cylinder.
For example, if our cylinder was 1" in diameter, and we printed at 0.2 mm (~.008") layer height, the cylinder would have about 125 layers. The picture below is a representation of what this would look like.

You can see the rough edge, and you would have small overhangs, ultimately leading to a rough surface finish and poor print quality. 

Printing on the Y axis would give us the same results, so how about the Z axis?

The resolution of the cylinder would be controlled by the stepper motors. Typical printer stepper motors can have a precision of 1.8 degrees or 200 steps per revolution. So what does that mean for us? 
It will greatly improve our resolution, but by how much, you ask? Let's figure it out.
The pulley cog on my printer is roughly .375" in diameter. So 1.8 degrees of rotation on a .375" pulley produces .006" of linear motion.

Huh, the stepper motors produce linear motion of .006", while the layer height is .008". That doesn't seem like that much of a difference! Well, some really smart guys have come up with microstepping. Without going into too much detail, this allows a stepper motor in our application to achieve 1/8 of a step. So that would be .00075", about one order of magnitude smaller than our layer height. 
I tried to show this in CAD but it was too small to appreciate. I had to scale it up 120 times. Think of it as a polygon with, by my estimation, over 200 sides. Nearly a circle to the naked eye.

Here is a comparison of two prints. #1 was printed vertically, #2 was printed horizontally.

Today's lesson is to always print cylinders oriented in the Z axis.
Please feel free to add to the discussion or ask any questions. 
Thanks for reading!

3D PrintingSteam Labs