Using an FDM printer and PLA or ABS, without adding support material. What modifications can I make to improve how steep an overhang my printer can print before it starts having problems?
The obvious first answer is to add a cooling fan, increasing the airflow over the freshly-extruded material ensuring it solidifies. What other things can improve it?
Does lowing the temperature help? Raising it?
Does speeding up or slowing down the print head help?
Does increasing/decreasing the extrusion diameter, or layer height help?
There's an answer here that holds some of the same concepts. Regarding your questions:
- Does lowering the temperature help? Raising it? : Yes, lowering the temperature can help. I've found that it is best to stay closer to the lower end of the material's melting point and just a bit above the point. Not only does this help with potential over extrusion, but also shortens the time it takes for the material to cool (refer to the link above). However, this could cause clogging if your temperature is too low. Keep an eye on your drive gear to see if there is too much friction while at lower temperatures. Increasing may keep the drive gear from "eating" your filament.
- Does speeding up or slowing down the print head help? : I prefer to print slower, most of the time, to allow the material to cool a bit more to avoid curling/warping (I primarily print with ABS, so it matters more). You might be able to give and take between temperature and speed. Consider if your nozzle is cooler and your speed is up, bridging gaps might yield the same results as if you proportionately swap these two values. This concept may only matter if you are in a pinch to get the part done. Again, I prefer slowing my machine down as it allows current/previous layers to cool more before continuing. This can be especially helpful with overhangs when paired with lowering your nozzle temperature.
- Does increasing/decreasing the extrusion diameter, or layer height help - I assume that extrusion diameter equals layer height (not difference in nozzle diameter, aka swapping nozzles). I'm not completely sure, but I think this depends on the part as well as slicing engine settings. For me, MakerWare is pretty good about proportionately adjusting extrusion steps with layer height, so I see an equal change in the width of the extrusion. I would think that in general, a larger layer height would yield a larger extrusion width. This would be helpful when printing overhangs, but may not be helpful when printing bridges (a larger strand will retain heat longer than a smaller one).
Hopefully this helps, please comment if you need more information/clarification.