Printing printer parts in PLA

Hi all,

I need to print a few upgraded pieces for my Prusa i2 and would like to have some advice regarding the best settings for those prints.

I'll be using PLA in 3mm, can chose between a 0.35 and 0.5mm MK5B J-Head and print on a heated bed smeared with stick glue (no issues at all with 1st layer adhesion). The slicer will probably be the Cura engine that comes with the 14.07 version but I also use Kisslicer.

The advice I'm seeking concerns what may be the best/optimum layer height, extrusion width, infill percentage, infill pattern, support type and density, piece orientation on the bed, printing speed/acceleration, printing temperature (if it has an impact on the structural strength of the pieces) and any other factor that could impact the ability of the printed part to withstand the rigours of being part of a Prusa i2 printer.

Maybe this is already discussed somewhere else but I was unable to find anything by googling it.

Thanks in advance for your advice.

I'm using a .4mm J-Head on an i3, and here are the settings that work well for me:
.3mm Layer Height
Honeycomb infill @ 10-20%
60mm/s infill
20-30mm/s perimeter
195 °C print temp
70 °C bed temp
No supports (kinda a pain)
And around .6mm extrusion width (but I just let Slic3r auto set the value)

Hope that helps!

Colder print temperatures affect layer adhesion and can weaken the part, but much depends on the filament. From one batch to another of PLA, I've had to increase print temperature by 5-10 degrees to get reasonable layer adhesion. I would experiment with printing temperatures to determine what works best for you, but I find 195 nozzle temp best for what I'm using right now.

Regarding nozzle size, 0.35mm will take a really long time to print parts. 0.5 will be fine for most of the parts. If you have gears with fine tooth detail, consider switching to 0.35mm for just those parts.

Layer height won't have much impact on anything but printing time, however the fewer the layers the less chance of delamination under stress.

Infill obviously has an impact on strength; my personal preference is honeycomb and I would suggest no less than 30% infill for structural parts. I don't know if Cura supports the honeycomb infill parttern, though.

Regarding piece orientation on the bed, it depends completely on the part being printed. Try to orient it such that any stress is perpendicular to the run of filament. For example, if you're printing something long and thin, it will bend and break very easily along the long axis if it's built with multiple layers perpendicular to the long axis, instead of parallel (hope that makes sense).

First of all thanks for the advice and suggestions. I'll try to do some trial prints to determine how best to do this.

In the meantime I continued to google for more information and came over a study made by Joshua Pearce, an associate professor of Material Science and Engineering, regarding the quality of 3d printed parts and how certain fabrication settings influence that quality. He used (almost) the same methodology used to assess the mechanical properties of metal worked parts and his conclusions are indeed very interesting. The main conclusion being that, and I quote, "3-D printed components from RepRaps are comparable in tensile strength and elastic modulus to the parts printed on commercial 3-D printing systems".

If anyone is interested the full study can be found here.

Another study by (amongst others) the same person regarding the Life-Cycle Economics of Distributed Manufacturing with Open Source 3D Printers can be found here.