So from the marketing page
https://www.raise3d.com/collections/acc ... ent-sensorWhile this is a bundle, there are 2 totally separate and not exactly related parts here.
THIS is the filament out detector
In this picture included in the bundle that really should not be a bundle is this.
While both will plug into the mainboard, they are NOT plugged together or related in any way.
The filament detector just detects if filament is in the middle of the that sensor. That's all it does. If turned on and printing and that sensor detects no filament, it pauses the print.
The OTHER safety board is a totally different story. It plugs in at the mainboard and the ribbon cable then plugs into it.
It's purpose in life is to correct a safety limitation of the mainboard in that it cannot detect when the ribbon cable is broken or unplugged mid print.
Again, let's really get to the crux on this.
Cables can and will fail. You can say all you want that it should be engineered better, but across every brand of 3D printers for the last 10 years, there is one thing in common and that is cables that flex (and since the extruder must have cables to it and when it moves, they flex over and over and eventually will wear out or fail).
The second part is, that locking connectors should be used on all cables- especially ones that flex. The ribbon cable to extruder head breakout that is carrying the super critical temperature reporting information of the hotends does NOT use a locking connector as currently supplied on all raise 3D N series printers. There are details that are printer version specific on cable routing, but all of these printers are subject to both flex failing of the ribbon cable and unplugging of the connector at the extruder head breakout.
The third part that makes this a problem is that the cable fault may not be detected mid print. This is where this goes from an annoying failure to outright dangerous failure. This is due to an overall architecture design of both the mainboard and the extruder head breakout board. Again, the issue is that at the very most basic logic level of just reading the voltage on these pins, if the cable comes unplugged or broken wire connection mid print, the mainboard still thinks it got a valid temp report. No firmware update can fix this hardware failure to detect a fault. What this means is that mid print, if you have an intermittent connection in this critical cable, that OBTW has no locking connectors, and flexes every time the extruder moves, the firmware may go trough periods of time where it has NO idea the actual temp of the extruder heaters. However, it is still able to power those heaters and turn them on based on the simple logic of what is the reported temp (which in failure is the last temp read) is that higher or lower than setpoint? That in turn determines the power sent to the heater. This is why we see BOTH types of failure. If at the time of the break in connection, if the heater was 2 degrees below setpoint or even one degree, the firmware thinks it should be heating up trying to reach the setpoint. However, over time, since it is not getting a feedback of the rising actual temp of the heater, it just keeps on heating well past the desired setpoint. The other way it happens is then say it connects for a second and gets this now too hot temp report. That stays and keeps reporting it's higher than the setpoint thus turning off the heater. But the cable is broken or not connected. So the real temp is dropping like a rock, the firmware thinks all is normal and you are near the setpoint and you eventually get a jam because the extruder cooled off.
And here is where the user can get confused and very frustrated. You turn off the printer or reboot and suddenly you may or may not have a bootup failure for mintemp. This all depends on if the extruder is moved to a point where the wires flex or the connector makes contact again or not on bootup. Power on from completely off is the ONLY time that a ribbon cable fault is detected. This is because the system starts up from off with no voltage. If the cable is not connected then it never gets that first voltage signal for a valid temp across the cable. However, if the cable is flexed just right, or the connector is just barely making contact- then the firmware boots thinking all is OK so you start a print.
Again, it's all about failure detection. The system can and will detect if the thermocouples are disconnected from the extruder head breakout. This is because the onboard chips that read the thermocouple on the tiny extruder head breakout board constantly check the thermocouple. Again, if that connection breaks it is detected. But if the ribbon cable between the 2 boards breaks connection, that is NOT detected mid print.
So that is what the safety board is all about. That board and locking cable set plugs directly into the mainboard for the ribbon cable. Then the ribbon cable going up to the extruder then plugs into the locking connector on that board. Basically it puts the device inline in the circuit. The idea is that since this DOES have locking connectors, is installed at the mainboard where it does not flex or bend or vibrate, the device has a low chance of breaking connection to the mainboard and as said before, this is because the mainboard cannot sense the loss of connection by itself. However, that device changes the circuit and the isntant the cable to the extruder head breakout fails in any way, now a maximum temp voltage is sent to the mainboard and read by the firmware. That does 2 important things. #1 it instantly turns off the heater output because reported temp is way higher than set temp. Even if no other safety code invoked, by the shear nature of what that function does it fails safe. The second part is, by exceeding the maximum safe reported temp, the system knows there is a fault and stops the print. Rather than like before dragging on and still trying to print, now in a fault, we have a proper function and stop.
