What's Wrong with Octoprint?

 I started a 3d print running from Octoprint, as I often do, and after 30 minutes of printing, the printer halted.

Octoprint had tried to send messages a number of times and they went unacknowledged.  I didn't have the serial.log enabled, so that was all the information that I got.  I enabled the serial.log and tried 3d printing again.  Thirty minutes later, the Creality Ender 3 Pro halted and there was a notification on Octoprint of too many communications timeouts.

At least this time I had a log file. I scanned the log file and found six failed attempts to communicate.  No other helpful information was in the file.  Now what?

I came across an odd recommendation suggesting that it could be the Ender 3 LCD cable position causing communications issues.   I moved the cable and tried 3d printing again.  A 2 hour print ran successfully!  Problem solved!  Not quite.

My next 3d print, 3.5 hours long, failed after 2.5 hours.  Same issue, too many failed communications attempts.  

I tried a new USB cable. I tried using a different microUSB card.  I tried using a different USB port on the Raspberry Pi 4 running Octoprint.  I tried uninstalling and reinstalling the serial port driver.  I tried a whole new install of Octoprint.

It must be the Raspberry Pi 4, it does run a bit warm.  Nope, it wasn't the Raspberry Pi 4.  That left only the Creality Ender 3 Pro as the culprit.

I checked wire connections and especially ground connections on my Ender 3 Pro.  I even considered making my own noise shielding with aluminum foil wrapped around the LCD cable and grounded but fortunately, I tried something on a whim first.

I removed the 3d printed plastic cover for the back of the LCD that I'd 3d printed 2.5 years ago.  

As I began to remove the screws that held the cover to the back of the LCD, I noticed that one screw was very loose and the other three srews were not much better.  Oh well, cover removed and LCD screws tightened down, I ran a 7 hour 3d print.  Because I was tired of wasting filament, I ran the Ender 3 Pro dry.  No filament.  I used the same settings as always but I wasn't wasting any more plastic.

It worked!

I examined the back of the LCD a little more closely and realized that the LCD ground connection to the frame was dependent on those 4 mounting screws. Loose screws could jiggle and create a ground make/break cycle that could worsen with vibration. 

I got rid of that LCD back cover.  I may find or make another one that doesn't use the LCD PCB screws for mounting.  Then again, maybe not.

If you're having communications trouble with Octoprint to your 3d printer, always check every single ground connection and path.  It never occurred to me that grounding to the LCD could affect serial communications, but only because I haven't looked at that area of the printer for over 2 years.

Setting up a new Creality Ender 3 Pro 3d Printer

     I have caught the 3d printing bug.  However, I did not want to spend a lot of money on something right away.  Besides, as my wife says, "I am thrifty."
      I bought the Creality Ender 3 Pro because I had read about the few improvements included in the pro version that were not in the standard version.  First is the magnetic bed, I'm not sure if it justifies the $40 price premium, but the 1 year warranty and support and the improved extruder does justify the price premium for me.

       The first bit of advice that I could offer in setting up the Creality Ender 3 Pro is to first use the foldout manual to identify everything and lay it out and then put the foldout manual away.  It can be followed by a person determined to interpret the images, as I was, or a person ignorant of the build video that comes with the unit on the micro SD card.  Plug in the micro SD card adapter and watch the build video.  It is much easier to follow than the multifold manual.
      After finishing the build I was unable to level the bed. the left side was lower than the right by almost 1/3 of an inch!  I took the bed off to see if the bed frame below was that far off from level.  It was!  Argh!
     So I examined the bed frame closely and concluded that it had to be the X-axis bar carrying the printer head that was not level.  I was correct.
     In my mind, if you have rollers riding a frame and the holes are aligned then the parts must have been created to be square to each other.  This is not true.  BTW, I'm an electronics and IT guy not a mechanical engineer as should be evidenced by that last statement.
     I watched a few setup videos, there's nothing about this issue from Creality BTW, and I learned about the concentric nuts.  Concentric nuts on the Creality Ender 3 printers are used to move specific rollers a range of about +- 1/8 of an inch.  They function similarly to a cam on a camshaft.

     I moved the X-axis to the top and measured each side to check for square.  It was off by 1/3 of an inch.
     I tried adjusting the concentric nuts on each side of the X-axis.  I had to loosen the lock-down nuts a little of course, which I almost forgot to do.  I never did get the X-axis square.  Every adjustment resulted in either the X-axis being loose or much too snug to move. I finally compromised with being 4 mm from square with the assumption that the bed could be levelled to that.
     As I began levelling the bed, I noticed that one corner of the bed was higher than the rest, even completely cranked down.  I examined the bed mounting again and noticed that the spring with the bed connector mount was compressed more than the others.  That bed connector mount compressed the that corner spring about 1/8 of an inch.  No wonder the one corner was higher than the rest and the other 3 corners felt weak and wobbly.

     I added spacers to each of the other 3 bed corners to match the corner with the bed connector mount.  Now I could finally align the bed!  I adjusted each corner to be just 1/2 millimeter from the bed and at last I was ready to print!
     The print for the cat model ran for 5 hours and 43 minutes. The top of his head was cut off just below the ears.  The filament that came with the printer, which is not on a spool, had tangled and had not fed through the printer for the last 10% of the print.

     To make the best of it, I sanded the hole in the top of the cats head and used the resultant container as a toothpick holder.
     I retried the cat model print out after untangling the filament and stringing it out like a telegraph wire - I really did not want to hand my wife another cat with the top of his head cut off.  The print went well and the quality is actually impressive.

     I must admit that I thought that 3d printing was finally ready for the average person because it is so affordable now.  The pre-built models offer less frustration certainly but if anything needs to be replaced or becomes misaligned then it could become frustrating for the non-hobbyist.
     Some day 3d printing will be as easy as using a toaster and as cheap as an inkjet printer and as maintenance free.  It's too bad that we still have years before we reach that point.