Nozzle Overheat Alarm

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Protolink3d
Posts: 25
Joined: Thu Aug 29, 2013 7:33 pm

Nozzle Overheat Alarm

Post by Protolink3d » Thu Mar 05, 2015 1:33 pm

Hi guys, I own two Up Plus machines that I use for my rapid prototyping business. I am looking for some help please. I have recently started getting problems with perceived nozzle overheating alarms that stops the printing or does not even allow it to start. I say perceived because I have tested the PT100 of the nozzle and rang out the ribbon cable for continuity and signalling of the temperature signal to the motherboard. All is OK and it is definitely not the nozzle that actually overheats.

At first I thought it is because of a momentary open circuit from the PT100 (Loose wire or dry joint) which would cause the resistance to spike up and thus be perceived by the control software as a high temp. But I have tested the sensor and it is fine. I have also swapped complete print heads and then the problem disappears for a few weeks and then come back. So it is happening on two different print heads intermittently.

So I get nozzle overheat alarm on my Up software and the printer just freezes there.

Can anybody give me some ideas where to look next please ?

pleppik
Posts: 336
Joined: Sun Dec 11, 2011 2:14 pm

Re: Nozzle Overheat Alarm

Post by pleppik » Thu Mar 05, 2015 6:03 pm

I've seen this problem a few times, and it's always been a loose/broken wire on the temperature sensor causing occasional open circuits.

Since you've already swapped the print heat, the loose wire isn't there. But you could have a loose wire in the same circuit which tests OK when the printer is off but occasionally jiggles open because of the vibration as the printer is operating. I'd keep pursuing that direction, since it seems the most likely problem to me.

Neal
Posts: 32
Joined: Sat Oct 06, 2012 2:26 pm

Re: Nozzle Overheat Alarm

Post by Neal » Fri Mar 06, 2015 12:07 am

I concur with the loose or bad connection to the temp sensor theory. I had the same problem and wiggling and re-tightening the cable would resolve it for a while. Eventually I replaced the cable and it hasn't been a problem since then (several months ago).

Protolink3d
Posts: 25
Joined: Thu Aug 29, 2013 7:33 pm

Re: Nozzle Overheat Alarm

Post by Protolink3d » Sat Mar 07, 2015 9:36 am

Hi guys,

Yes I was also of that frame of mind. I am an instrument Technician by trade and PT100's are very familiar to me. 99.9% of the time we have temp spikes or spurious temp alarms on a control loop is because of loose connections on the RTD loop. Thus that 113 odd ohm spikes up and the motherboard thinks high temp. I replaced the head and after a few weeks it started happening again with the second head. Then I put the old head back and it was fine, few weeks later it happened again. Yesterday I stripped the machine.

Took the opportunity to clean out thoroughly and grease the rails etc. I did a good continuity check through the ribbon cable to the plug on the motherboard side and did not find any anomalies. Even when bending and twisting the the ribbon cable. So machine back together and off we go. 4 successfull prints of a bout 5 hours each later and no proble. Maybe I re-seated something that was loose although I did not find anything that felt loose.

Thanks for the feedback.

juancr
Posts: 90
Joined: Sat Jul 28, 2012 10:19 am
Location: Spain
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Re: Nozzle Overheat Alarm

Post by juancr » Tue Mar 10, 2015 7:49 pm

Hi!
In my case I think it is because rust is created between the terminals of the temperature sensor. I fix the problem scratching the space between the sensor terminals, but unfortunately, the problem comes back after some time. I changed the sensor two times and the problem still is there, only some times, not every time I print.
I have to say that the place were I live is very wet, raining almost everyday :-( . I have never had this problem until I moved to my new town.
Regards,
JuanCR
(You should know I do my best with my written english ;-) )

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