3D Printer - Some Lessons Learned

I am sure that I am no where near done having my printer learn me lessons but thought that I would take a minute to capture some of those learning's to date:

• Seems obvious, but, turn things off when making hardware changes!   As in unplug the power and the USB connection!
• Probably obvious to someone that knows electricity, but, unplug the printer before soldering something (like a control or power lead) that is connected to the printers electronics!
• When doing calibration prints keep a careful record of each print and the conditions for that print.   You might even want to go so far as to save individual config files for the slicer you are using.
• Don't mix PLA and ABS in the same nozzle.  I am not completely sure this is backed by any one else but I am convinced that I had a mega clog as the result of this practice.
• "ABS Goop", which is some ABS dissolved in acetone, makes a good bed prep for printing PLA.
• A clean bed results in a clean printed surface!
• PLA is a lot easier to work with than ABS.  In my case I had much less issue with warping, adhesion, and as a bonus everything was faster given a lower bed temperature.
• Printer enhancements for ease of adjusting the level of the bed early is highly advised!
• Once you have done the above you can do a rough adjustment of height using the piece of paper method and then print a bed leveling exercise to get the rest of the way.  I print this file pausing to adjust the overall bed height then resuming while often adjusting corners with the printer running.
• Timing belts should be tight.  This is another thing that might seem obvious but I ran for quite a while with belts that were a lot looser than they should have been.

It feels like I am missing some things ... which I will come back and add as I remember them.

Random / Occasional Axis Slips

My printer is in it's terrible twos.   It went through a period of printing stability and still has its moments.....until an axis decides to randomly slip or skip.  I have been working on this for weeks and have tried everything that I can find on this board (at least I think)!  As I said, the printer will have moments of stability where it will print for hours with no issue and pretty good quality.  The X-axis is the favorite to slip but the Y and Z will occasional join the fun.  It does not always happen on a long print as it has been known to happen early in a print as well. 

Here are the things that I have tried and/or ruled out:

I have adjusted the trim pots from just over stall to a quarter or more turn past stallI have swapped stepper drivers
I have moved the x-axis to the second extruder slot
I have upgraded power supplies
I have added a big cooling fan to the electronic stack
I have ensured that my timing belts are not slipping
I have made sure that the carriages move with minimum resistance
I have slowed everything down when I slice the part

 What else is left to try?!?!?   Could it be the Ramp board ... or the Arduino?  They are the only things that I have not replaced or been able to rule out!   Frustrating!

One thing that occurs to me, that is easier to remedy than a swap out of electronics, is connecting the printer to a cleaner power supply.   I just happen to have one (that also converts from 220V to 120 and offers filtered power at 220V) so that is in the circuit now.

Someone on the RepRap Forum has suggested possible EMI issues, if not in power, then I don't know how I would solve!?!?

[Update] I have gone ahead and replaced the Ramps board and the printer has been behaving since including finishing a seven hour print with no hiccups.   Fingers crossed.  

[Final Update] Printer has been stable.  It was either the Ramps board, or possibly, a wiring fault that got corrected when I replaced the Ramps board.   Not sure if I will ever know!