Two mystery issues: x-axis endstop & extruder temperature

Hi!

First of all, sorry for my bad English. Obviously I am not native English speaker but I hope the message is transmitted.

I have two issues with my Wanhao Duplicator i3 Plus printer:

1. X-Axis end stop is triggered all the time no matter if it is pushed down or not. As you know it is located in the left side of x-axis. The x-axis does not go home as told but moved a few millimeters to right. I can manually force the print head to move left but it will crash to the carriage eventually. I solved the status of end stops by using M119 command and other switches worked as they should. It did not change the situation when I pushed the switch by finger.

2. Extruder temperature is stuck at 210 °C. When I turn the printer on the thermistor claim the temperature to be that 210 C but I can clearly tell the heater block is not heated at all. If I set the temperature to for example 100 °C the temperature won't decrease. If I set it greater than 210 the heater will start to heat the temperature. After a while the user interface says there is error in temperature and the heater is turned of.
Things I have already done:

- I checked all the wirings and connections in case of short circuit or bad connection but no luck there.
- I suspected that the firmware was spoiled someway so I updated both firmwares (motherboard and LCD screen) but no changes to better
- Switched the end stop switches with y-axis but the same symptoms occurred.
- Thermistor changed with no influence.
- Mother board changed couple of months ago. After that the printer worked fine.

Do you have any suggestions what to try next? If something was not clear I will try to explain it more precisely. Thanks in advance!

Seems like your endstop might be wired NC when your controller expects NO or vice versa. Either that or a possible short/open circuit (i.e. try some continuity testing),

Extruder issue seems like a faulty thermistor or a mismatched thermistor to thermistor table in firmware. 210 degrees is odd, I usually get 0 or some negative/300+ degrees from a short or open circuit on the theristor. You can test the thermistor's resistance to see if it matches what you have set in firmware using a multimeter.

I will check the wiring in case of short circuit one more time. Its funny because the end stop problem appeared suddenly with no warnings after working properly for a long time. And the problem occurs only in X-axis. I used M119 command to check the status of the end stops and all other worked well except the x-axis. The status was "triggered" no matter if its pushed it or not.

I will check the thermistor and get back with results. I assume the thermistor table should be ok because updating the firmware couple days ago did not change the matter. I used this one 3.0.1 version of ADVi3 (https://github.com/andrivet/ADVi3pp-Marlin/releases).

I am afraid that the both issues are because of broken processor but the question is what is causing it because I already replaced the motherboard once because of burned regulator.

That clears up/gives a bit more info on the end stop issue (I had a bit of trouble understanding some things in the first post). Sounds like a failure of the end stop, possibly due to wire fatigue. First check to see if the endstop works correctly with a continuity tester (i.e. check that connection is established and broken as the switch gets pressed and released), then measure continuity right up to the board (past the connectors to make sure the wire hasn't broken inside the connector plug.

Did the thermistor issue appear after a firmware update or just one day without any changes to the machine? I somewhat doubt it's a processor issue, otherwise I think you'd had even more issues.

Some quick and dirty tests you can do to help isolate the issue is check the x endstop by plugging it into the y axis endstop connector (and plug the y axis endstop into the x axis connector). This should tell you if its an issue with the endstop/wiring or the board. If your board supports 2 thermistor inputs you can also try connecting the thermistor to the second input to help narrow down that issue as well.

It's very possible the thermistor wiring has broken, I've done it more than a few times myself.

Thanks Trakyan!

I tried to change the switch with y-axis and the issue remained with x-axis. So basically I plugged the X-axis switch to Y-axis and it worked well. Vice versa, the Y-axis switch showed status "triggered" all the time when plugged to X-axis. So I assume the switches are good.

Then the next question is if there is some problems in wiring. I looked through the wiring with multimeter and I was not able to find any short circuits or bad connections. I also unplugged the x-axis end stop from the motherboard and checked the status. It was still "triggered"! So this is very odd.

This is why I suspected the firmware and board.

The thermistor issue appeared just one day without any changes to the machine. With this also, I unplugged the thermistor from the board and checked the "temperature". It was still 210 °C. Using multimeter I measured the resistance of the thermistor and it was 100k and the firmware has corresponding values.

Any thoughts?

endstop.... yes that is either board or firmware looking at wrong pin, or endstop plugged into wrong place.

I would check the soldering around the endstop plug for bad soldering

Edited 1 time(s). Last edit at 08/09/2018 09:06AM by Dust.

Since the endstops are confirmed working, and the result is the same with no endstop plugged in at all, I'd have to guess the connector on the board is broken. If you switch the firmware from NC to NO (or vice versa, I don't know what your current setup is) and you get the same result (except now it never triggers), I'd be almost sure it's the board having a short or open circuit between the traces/connector. Without replacing the board you can try plugging the endstop into another connector (i.e. instead of xmin use xmax) and switch the pins in firmware.

Since the board reads 210 degrees with no thermistor, that must be the open circuit value. However, since you measured 100k across the resistor leads there isn't an open circuit there. There's an open circuit somewhere, you can narrow down exactly where it is with a multimeter/continuity tester but there's no guarantee it's fixable. Just as with the limit switch you can reconfigure the pins and use the second thermistor input if your board has one.

Ok, now we have limited the issues to board. The board is this one:
[www.3dprima.com]

and the printer uses also interface plate and ribbon cable between the motherboard and interface board:
[www.3dprima.com]

I tried to look for different pins that could be used to test the pins but couldn't find any. There are no pins for the x-axis endstop in the motherboard because the signal is transmitted using interface board and ribbon cable.

I did not find any short circuits from the interface board and not from the ribbon cable either so we can assume the fault to be in the mother board. I will contact to the manufacturer and ask their opinion because I'm running out of ideas :/

Thanks!

I can't say I've seen that board before, and I don't really understand what that interface board does and what it interfaces with.

That's a really weird board though, the Z and Y endstops are on the main board but the X axis isn't. As far as spare pins go, I'm guessing the EXT pins aren't used as there isn't a connector there, so you could use those. That being said if the manufacturer offers to replace the board that will probably be much less hassle.

Yes me either. It is basically combining all the wires from extruder to one place and then the data is transferred to motherboard using the ribbon cable.

I took contact to the manufacturer and they said the problem is because error in motherboard but they weren't willing to send new board for free. I contacted also to dealer and their custom service was great. They understood the problem and sent a new motherboard immediately.

Let's hope everything goes as planned and the problems disappear with new motherboard.

Thanks to everybody for effort and your time. I really appreciate it

No worries, glad to hear the problem is (hopefully) resolved!