I recently bought a Prusa i3 from a Chinese manufacture, so going in I understood there was likely going to be a lot of work to get the printer running.
I wanted the prints that came off the printer to be the highest quality I could have. This meant I needed to know how to calibrate and optimize the settings for the printer.
Researching the topic online, I found the Triffid Hunter’s calibration guide. I planned on following the guide for calibration, but I ran into many hardware/design issues.
First, the Z-axis endstop was difficult to adjust, causing the nozzle to scrape along the heated bed a few times after misalignment. The endstop was attached to the z-axis smooth rod by a clamp that was tightened by a screw. This setup leads to near impossible calibration of the z-axis, but I did eventually calibrate the z-axis to an acceptable point.
Second, homing sequence also caused the nozzle to jam into the heated bed, possibly damaging it. This greatly exacerbated the process of calibrating the z-axis. Eventually I started to home the Z-axis off the bed, which “fixed” the problem.
Third, when starting to print, the hot-end took a long time to heat up, about 13 min. To put that into perspective, most people I have talked to say their printers heat up in a few minutes and after I fixed my hot-end my printer heats up in about a minute and a half. I originally tried fixing the heater by adjusting software settings including running the PID auto tuning G Code command, M303 P0 S200. After trying a few other software solutions that didn’t change anything, I measured the heater’s resistance and found it’s resistance was about 13 ohms. This meant with a 12 volt source, the power outputted would be about 12 watts, using the equation Power = Voltage * Current. I found some new heating elements online rated for 40 watts and it has worked great, although I only received the heater after gathering the data for this write up.
Fourth, the printer nozzle jammed many times. Often it was due to the hot-end cooling down too much. A few times the nozzle jammed because metal got stuck in the tip. This jam happened soon after the nozzle scraped along the hot-bed. To clean the tip I did a cold clean, which involves heating the hot-end to the melting point for the plastic being used and then waiting for the hot-end to cool down. The cool temperature I found best to work for PLA was 70 C.
Finally, bed adhesion was a big issue, as many 3D printer owners’ know. Knowing about this issue going into this project didn’t help me. I bought some generic purple glue stick after reading that any glue stick that said it was acid free and washable would work. This glue stick gave false impressions, yes it did help the PLA adhere better than nothing, but it still often failed. This led me to try Elmer’s white glue stick at the recommendation of some fellow printer owners. In order for the PLA to stick, the glue stick must be slightly rough, and then I haven’t had a print come off or warp since.
For testing, I created a spreadsheet that would contain every test print I made along with all the setting of the printer for that print. For ease of comparing tests, I also included a note on what I was trying to test. After the print I recorded comments about the print quality.
While trying to diagnose the issues above, I ran some test prints and recorded my findings. I found that increasing the jerk made corners more defined. The drawback to increasing the jerk was it also increased the stress on the printer. Trying to combat the stress on the printer, I found increasing the acceleration while decreasing the jerk kept the definition in the corners while lessening the stress.