Argthtjtr

3D-printing newbie here. I have a Geeetech's Prusa i3 mk2 B.

I'm trying to print this: https://www.thingiverse.com/thing:1358311

That's a mold, with 2 external parts and a core. The exterior prints wonderful. But the core is too messy. Take a look at this:

What riddles me is that the side parts, and the pole's base, print fine; so this does not look like a bad calibrated printer, but something else entirely. My guess is this is some precise tuning I don't know yet.

I've been trying to print that little pole without success for over a week now. Tried all this:

• Changing the slicer program (I've used Ultimaker Cura and Slic3r prusa edition)


• Tuning the e-steps for avoiding over-extrusion.


• Tuning the z-steps, so the nozzle doesn't melt the last layer when printing a new one.


• In the same sense, changed the nozzle heat.


• Tried lots of different layering, speed, walls, bridging, and quirks configurations.

So far, the best I got is a little pole not-too-deformed so I can make my part anyway, even when the pole is not well printed. But after seeing lots of videos and reading lots of tips online, I still don't understand how to tune my print for that simple little pole.

Other that tips, what I would really like to ask is if somebody has a name for that problem I'm facing, so it would be much more easy to search for my tuning options.

So... any clue how to fix this?

Basically, you print too hot (and fast) without enough cooling. The deformed small pin in your image is a perfect example of depositing new layers onto too hot (not cooled down enough) prior layers.

You can easily solve this by printing two identical parts spaced apart from each other. This allows the layers to cool before the next is deposited.

From mastering Ultimaker Cura:

When printing a series of small parts, print them all together. The
travel time between the parts is often enough time for the layers to
cool without changing your settings.

If you do want this to print as a single piece, you need to:

• 
  tune down hotend temperature (use the minimum temperature that gives good print results, printing a temperature tower will help to determine this),


• 
  increase minimal layer time (may not always work as speed will not be lowered under the minimum printing speed) and


• 
  increase part cooling fan percentage (or print a better fan duct that allows for more cooling air to reach the print; many fan ducts are too convergent, the pressure increase is then too big for the fan to effectively push air through it).

The other answers have addressed the heat problem. The other risk is that a rod printed vertically like this is prone to snap, because the weakest axis is between layers.

I often rotate pieces like this and print with the rod horizontal. You then have to remove the support and/or brim material, and probably do a bit of sanding to get it properly round, but the final part will be much more reliable (not break).

The thin core gathers too much heat in the printing process. If you need to print slender objects, either:

• Print several. This is the most simple solution and best for beginners.


• Increase cooling. A better cooling solution or increased fan speed often can help to get thin or delicate objects printed.


• set minimum layer time to slow down the printer automatically on layers with low cross-sections. If too small, it could pause on the edge of the print, which could leave scorch marks.


• If you know a little more about your printer and got your retraction dialed in, you can go more advanced: set minimum layer time to 10 to 15 seconds and activate the accompanying Z-hop. This will prevent the scorch marks, but you might need to make sure you don't string.

This way the part has a chance to cool down between printing layers.