Just a few of the hundreds if not thousands of topics regarding thermal protector and ribbon cable failures https://forum.raise3d.com/viewtopic.php ... tor#p53924https://forum.raise3d.com/viewtopic.php ... tor#p54103
Just so we are on the same page, let's repeat some stuff you should know about this printer.
The N series was the first design by raise, and some mistakes were made. They were corrected, but not everyone APPLIED the corrections.
So let's take 5 minutes and understand the control system. The actual heart of the printer is the motion control board. It was derived from an existing open source design called the RUMBA- no not the robot vac bot. https://reprap.org/wiki/RUMBA
. This is a simple board, well known from previous derived designs and used in a lot of printers. In and of itself, nothing wrong or problematic with the board. The issue is that a decision was made to use thermocouple temp sensors which then require a thermocouple amplifier chip to read them, and specifically an analog chip was chosen to send an analog voltage signal to the motion control board remotely from the extruder head.
Well, in doing so with an analog signal carried by a wire that has to flex millions of times during a print- what if and with high likelihood from the flexing that wire breaks?!!! And there lies the issue. In order for the motion control board to know if the extruder head temperature sensor is working, it has to see a CHANGE outside of a valid range of voltage on the connector from this ribbon cable. They left off a tiny resistor to pull the logic pin to either a high or low voltage when the extruder cable is broken or not connected and so the motion board keeps seeing the last voltage even when the cable is completely unplugged!! Since the controller needs that info to control the heater, and worse, it needs it 100% realtime during a print, we get instances where the printer is completely out of control until the firmware finally after a really long time invokes some safety code after it thinks something is wrong- and that assumes you've updated and installed the correct motion control board firmware.THIS IS LIKELY THE REASON FOR A MID PRINT STOPPAGE AND RESULTING SERIAL ERROR.
Again, the cable flexes. If it's intermittent, then some places during flexing it makes connection and no error is detected. Other times, it flexes and the cable is open circuit. Another factor- these do not have latching cable connectors and again, the flexing and so forth, the cable can ALSO come unplugged likely at the extruder breakout board side of the connection. Hot glue or other method is HIGHLY recommended to secure the cable.
And at a minimum, confirm and verify a protector circuit is installed at the motion control board. All it does is add 2 high value resistors to tell the motion control board the INSTANT the cable breaks connection. A simple but IMPORTANT fix especially given this is used in a school situation!!Again, 2 basic known facts:
#1 The ribbon cable is a wear and tear item and WILL fail eventually from flexing.
#2 The stock printer has a known flaw in which it cannot instantly and reliably detect a failing cable and will result in printing errors. A simple add on part was created to fix this design issue.
I guess I should add, understand that the thermal protector doesn't prevent failures of the cable, print stoppages, serial errors. It identifies a cable fault the instant it happens. As a side effect, because it then enforces a stop the instant a cable breaks, it improves print quality because you might well have been printing unknowingly with temperature errors and other unexplained print quality issues caused by a bad or failing cable.
Last, understanding the control system that the front panel is nothing more than a small linux computer running a print server application and console called raise touch which streams serial data in the form of gcode commands over the USB cable to the motion control board.
Because this is a limited protocol of gcode commands and replies, not all errors are robustly labeled and conveyed to the user via messages on the front control panel. A generic serial error is a WARNING and clearly, the message was not understood for the root cause- because who for the love of 3D printing thought replacing the motion control board was the fault??? EPIC FAIL in troubleshooting.
But more importantly, understanding that since the motion control board and it's firmware is what actually runs the printer, understand that that motion control board NATIVELY and even the stock firmware SUPPORTS a directly attached and cheap control panel to actually read and understand directly what the motion control board is doing, and then the entire concept of directly attached memory storage of the gcode file on sd card to be read directly and not streamed line by line the performance and reliability increases dramatically!!!
Right here is a discussion on the performance aspect improvement of how using the Reprapdiscount full graphic LCD controller easily available on Amazon and simply plugging it in and using SD cards can improve small segment gcode performance https://forum.raise3d.com/viewtopic.php ... unt#p27238
$15 on Amazon https://www.amazon.com/Aokin-Graphic-Di ... B07PF297YD
Also, again, the thermal protection to detect even the slightest chance of a ribbon cable failure:https://forum.raise3d.com/viewtopic.php ... mod#p34304
Raise3d's own forum post on the topic https://forum.raise3d.com/viewtopic.php?t=6580
Sadly, the linked page to order it gives 404
old capture of when they had this on the front page
ENSURE YOUR PRINTER HAS THIS!!
Instructions for installhttps://support.raise3d.com/N2-N2-Plus/ ... 3-507.htmlI HIGHLY suggest you contact Raise3D
, demand a thermal protector
, get your money back for replacing a motion control board completely out of ignorance, and get yourself either a spare or replacement ribbon cable and thermal protector
installed along with the $15 full graphic display control board and print from SD card thus bypassing the entire front panel raise touch and potential serial errors. AND both can coexist. You can leave the front panel connected over USB and STILL control and start a print job from the directly attached SD card control panel. The biggest difference is you walking over to the printer and carrying an SD card with the file on it, but that is a very normal and reasonable way to prevent a print failure and also get better small segment performance!!
Also, found yet another discussion on the early resistor modification to the motion board before the thermal protector was available by raise.https://forum.raise3d.com/viewtopic.php ... lue#p20818