My Ormerod burned...

Sigh...

Today I left my Ormerod printing alone for a while (30 minutes more or less) and when I came back I found smoke coming out from the extruder.
I turned it off immediately, and then turned on again to let the fan cool down the extruder.

The photos talk by theirself...

What I've found is that the termistor is not read properly anymore, Pronterface shows "T:-17"...

What shall I do now? :-(

I printed a lot in the last days, without problems... the only thing I made yesterday was updating the firmware to the latest in the duet branch, and last commit on GitHub says "Updating thermistor values".... Could it be connected to my problem?

Thanks,

Rosario

The change made to the thermistor calculation affects the reported extruder temperature. Previously, at around 200C the reported temperature was about 12C too high, so the extruder temp was about 12C lower than you asked for. At temperatures below 25C, the temp reading was too low, which explains why most of us saw the reported temperature as lower than expected when the extruder is cold.

I had a print hang on me once due to the attached computer going into sleep mode. It appeared that the extruder temp climbed to 300C (which is what the web interface was reporting), then the firmware decided it has a temperature measurement error and turned off the heater. So all I had was a ruined print and some burnt PLA on the print and on the nozzle.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
The change made to the thermistor calculation affects the reported extruder temperature. Previously, at around 200C the reported temperature was about 12C too high, so the extruder temp was about 12C lower than you asked for. At temperatures below 25C, the temp reading was too low, which explains why most of us saw the reported temperature as lower than expected when the extruder is cold.

I had a print hang on me once due to the attached computer going into sleep mode. It appeared that the extruder temp climbed to 300C (which is what the web interface was reporting), then the firmware decided it has a temperature measurement error and turned off the heater. So all I had was a ruined print and some burnt PLA on the print and on the nozzle.

So it shouldn't be a firmware-related problem...

My printer was printing from SD Card (no PC connected) when the problem occurred... So it shouldn't be related to the PC sleep mode either.

Hi Rosario,

Don't panic (yet) ! the hotend is remarkably robust - mine got hot enough to melt the bracket that mounts it onto the x carriage one day. The next day I dismantled the hot end to check the thermistor and to clean out the nozzle with a drill (to remove the charred plastic, which is something you might need to do now - Maplin used to sell, and probably still do, a set of micro drills from 0.3 to 1.3 mm in diameter). The ormerod was powered up at the time, but not printing it suddenly sprang to life when I disconnected the thermistor and the cartridge heater glowed orange before spitting out some flames and smoke (it was pretty quick). I killed the ATX power as soon as I saw it happen and presumed the whole thing would need to be replaced (the thermistor was reading odd values when I switched it back on). But that was before christmas - the machine is still printing (I had to make a new bracket). RRP updated the temperature monitoring shortly afterward.


I suggest you try reconnecting using only USB power (with the ATX switched off) and see if the thermistor values have returned to normal, then turn on the ATX and try heating the bed and nozzle to something tame while monitoring their temperatures with an external thermometer (preferably a thermocouple on a compatible multimeter, again Maplins have these for a reasonable priice) and check to see if the measured temperature matches the reported temperature.

by the way, if the thermistor was burned out and "open circuit" you'd have a reported temperature of -273.2 if it was short circuit, the reported temperature would be ridiculously high - you might need a new one, but it could just be that the beta in the new firmware is not right for your device and it reads kower than it should (mine reads sub-zero at 19 degrees ambient, and around 5 at 23 degrees, but I don't have the firmware update that has the new betas yet)

Ray

Quote
rosario
My printer was printing from SD Card (no PC connected) when the problem occurred... So it shouldn't be related to the PC sleep mode either.

I use a mac and repetier host (and as I said above not the latest firmware) if I'm printing from SD card and disconnect. the print stalls until I reconnect (I can get it to continue by repeating connection/disconnection but there does seem to be some interdependency so I always leave mine connected and awake - roll on a reliable and useful web interface!)

Ray

Hi Rosario

This is exactly why I started the over temperature shutdown thread. The response from RRP seemed to be that this had all been gone into before. Whilst the firmware behaves reliably then not too much of a problem but this is clearly not the case with Ormerod at this stage.

Rory

Looking around the internet, I came across drop-off resistors as a possbile (though probably unreliable solution - back in your thread the suggestion that mounting a reliable cut-off on the heatsink seems much better) - basically they used to rely on solder melting to prevent valves burning up, and would solder resistors in current/temperature sensitive places with no external support, when they got too hot the solder melted and the resistors dropped off (who knows where they landed!)

Ray

Quote
rayhicks

Quote
rosario
My printer was printing from SD Card (no PC connected) when the problem occurred... So it shouldn't be related to the PC sleep mode either.

I use a mac and repetier host (and as I said above not the latest firmware) if I'm printing from SD card and disconnect. the print stalls until I reconnect (I can get it to continue by repeating connection/disconnection but there does seem to be some interdependency so I always leave mine connected and awake - roll on a reliable and useful web interface!)

Ray

The same problem as you from the web interface, but I've been able dozen of prints from SD card without the PC connected with Pronterface (launching SD Print, then clicking on Disconnect and unplugging the USB cable).

Quote
rayhicks
I suggest you try reconnecting using only USB power (with the ATX switched off) and see if the thermistor values have returned to normal, then turn on the ATX and try heating the bed and nozzle to something tame while monitoring their temperatures with an external thermometer (preferably a thermocouple on a compatible multimeter, again Maplins have these for a reasonable priice) and check to see if the measured temperature matches the reported temperature.

Today I tried again with with only USB power and also with USB+ATX power, but the thermistor is still reporting -17.
Pronterface reports an error about thermistor on its console, see attachment.

Time to get a new thermistor + ptfe sleeving perhaps?

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
Time to get a new thermistor + ptfe sleeving perhaps?

I definitely think so

Quote
rosario

Quote
dc42
Time to get a new thermistor + ptfe sleeving perhaps?

I definitely think so

I'll try to find a replacement in an electronic shop in the nearby, otherwise I'll ask to RRP if they could kindly send me a replacement.
Do you know which thermistor it is and where I can fnd PTFE sleeving?

Thanks!

Hi rosario

Sorry you've had problems! I have received your emails, and I am (slowly) catching up, so I will reply. It looks like the hot end survived, though I think testing it by hand first would be a good idea, once the temperature readings are correct.

I suspect the thermistor has failed. If you have a spare resistor of 100k ohms (or even a range of resistors down to 1k ohms), you can remove the thermistor, and check that the Duet is functioning correctly by putting the resistor(s) in it's place. Don't run the machine like this, though! It's just to check the Duet is working properly. It should report different temperatures with the different resistors. If they all stay at -17C, check the wiring (particularly the hot end plug where it joins the loom) for bad connections.

You can test the thermistor, if you have a multimeter. It's resistance should be around 100k ohms at room temperature (20C) and the resistance will drop as it gets hotter - hold it between your fingers to test.

Send me an email with the parts you need, we will replace them under warranty.

Ian
RepRapPro tech support

Hi Rosario

It is a 100K thermistor, NTC type with a beta of 3950 +/- should work fine. It looks like a little glass diode, very cheap.

Dieter

Ormerod #257

In case you want to self-source:

This is the thermistor we use: [www.digikey.co.uk] Beta = 4138
The PTFE heatshink is quite specialised. It is 1/8" diameter (about 5mm when flat, unshrunk) clear PTFE heatshrink, 4:1 shrink ratio. I don't have another source for this - we get it from China!

Ian
RepRapPro tech support

Edited 1 time(s). Last edit at 01/11/2014 05:56AM by droftarts.

interesting that the error is an index out of range error, as if it can't access temps[0] which seems to be holding the set temperature for the extruder - I don't have any experience analysing the pronterface console messages, or any insight into its workings, but it may be that it shows a pronterface configuration error?

Quote
droftarts

The PTFE heatshink is quite specialised. It is 1/8" diameter (about 5mm when flat, unshrunk) clear PTFE heatshrink, 4:1 shrink ratio. I don't have another source for this - we get it from China!

Would this RS 330-4765 be a suitable alternative? It has a lower shrink ratio, but unshrunk internal diameter is 2mm shrinks to 0.6mm, good to 250 C operating temp.

---

RS Ormerod #472

Good find, tim_h! There is also a 3.2mm diameter version from RS, which is closer to 1/8" (3.175mm) - [uk.rs-online.com]
This will be a bit closer to ours, I think. The 2mm stuff may make the thermistor too loose in the hot end. I will ask RS to send me some to test.

Ian
RepRapPro tech support

Edited 1 time(s). Last edit at 01/11/2014 07:18AM by droftarts.

Isn't the 250C operating temperature a bit on the low side for ABS printing?

I also found this UK supplier of PTFE heatshrink. It also says max operating temp is 250C, but 400C for short periods.

Edited 1 time(s). Last edit at 01/11/2014 08:20AM by dc42.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

It looks like the same stuff, Tyco Raychem TEF-R.

From the data sheet it also states upto 400C for short periods.

---

RS Ormerod #472

That heatshrink should be fine for ABS. Extruding temperature is around 220 to 240C depending on filament. Above that it will be too liquid.

As the current hot end design has a PTFE nozzle liner (also with around a 250C operating limit), we don't suggest using it for higher temperature materials such as polycarbonate (300C usually). There are other (unfortunately incompatible with our x axis mounting) 'all metal' hot ends in the reprap world that don't have PTFE liners, but they are often long and quite expensive, as they need to be polished internally for a smooth filament path (otherwise the filament sticks). We've been working on our own version intermittently, but it's an engineering challenge!

Ian
RepRapPro tech support

Quote
droftarts
Hi rosario

Sorry you've had problems! I have received your emails, and I am (slowly) catching up, so I will reply. It looks like the hot end survived, though I think testing it by hand first would be a good idea, once the temperature readings are correct.

I suspect the thermistor has failed. If you have a spare resistor of 100k ohms (or even a range of resistors down to 1k ohms), you can remove the thermistor, and check that the Duet is functioning correctly by putting the resistor(s) in it's place. Don't run the machine like this, though! It's just to check the Duet is working properly. It should report different temperatures with the different resistors. If they all stay at -17C, check the wiring (particularly the hot end plug where it joins the loom) for bad connections.

You can test the thermistor, if you have a multimeter. It's resistance should be around 100k ohms at room temperature (20C) and the resistance will drop as it gets hotter - hold it between your fingers to test.

Send me an email with the parts you need, we will replace them under warranty.

Ian
RepRapPro tech support

Thanks Ian for your reply!

I made some tests and:

- I checked the termistor with an ohmmeter, and it seems it has gone...
- I put some different resistors (1k, 10k, 48k, open) in place of the thermistor, and on pronterface nothing changes
- I cheched all the wiring (hot end plug and wiring to the duet) and everything seems ok
- I downloaded from GitHub the last version of Pronterface, but nothing changed

Quote
rosario
- I put some different resistors (1k, 10k, 48k, open) in place of the thermistor, and on pronterface nothing changes

Try connecting a resistor securely, then resetting the Duet, then connecting Pronterface. I've observed that once a temperature error is detected, the firmware doesn't necessarily recover when the temperature is in-range again.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Probably best to start with 100K, and as dc42 says, reset Duet after connecting, once it sees an open circuit it seems to lock out.

---

RS Ormerod #472

If the thermistor has shorted to 12V when the heater failed, then the ADC input on the Due may also be damaged. Unless you can reroute to a different ADC pin, it may need a board replacement.

---

What is Open Source?
What is Open Source Hardware?
Open Source in a nutshell: the Four Freedoms
CC BY-NC is not an Open Source license

Quote
bobc
If the thermistor has shorted to 12V when the heater failed, then the ADC input on the Due may also be damaged. Unless you can reroute to a different ADC pin, it may need a board replacement.

Though this is certainly still possible, we've tried very hard to limit the chances of this happening, by using good connectors and insulating things as much as possible. That's why I suggested testing the temperature sensing with known resistors. If that is what has happened, it's the first Ormerod that has managed to do this!

We got very tired replacing Melzis because of shorting the 12V to 5V, due to dodgy soldering, or mis-connecting wires! It's why we went with looms for the wiring, and it's also much easier to build. Though people are always finding new and interesting ways of breaking their repraps...

Ian
RepRapPro tech support

Quote
droftarts

Quote
bobc
If the thermistor has shorted to 12V when the heater failed, then the ADC input on the Due may also be damaged. Unless you can reroute to a different ADC pin, it may need a board replacement.

Though this is certainly still possible, we've tried very hard to limit the chances of this happening, by using good connectors and insulating things as much as possible. That's why I suggested testing the temperature sensing with known resistors. If that is what has happened, it's the first Ormerod that has managed to do this!

We got very tired replacing Melzis because of shorting the 12V to 5V, due to dodgy soldering, or mis-connecting wires! It's why we went with looms for the wiring, and it's also much easier to build. Though people are always finding new and interesting ways of breaking their repraps...

Ian
RepRapPro tech support

Dear Ian,
I'm sorry of what is happening, even if I don't feel "guilty" in any way, at all.
I don't think I did something wrong. I didn't do anything to "find another interesting way of breaking my reprap".
My reprap has been printing for hours without any problems.
Yesterday, I didn't change anything on my reprap. Just turned it on.
I'll try to check again tomorrow all the connections with my multimeter, and try again with the resistors.
I'll write back.

Edited 1 time(s). Last edit at 01/11/2014 11:56AM by rosario.

Sorry Rosario, I didn't mean to imply that you did anything wrong - it's just an expression, and a general comment, not specifically directed at you. You have nothing to be sorry for! I just meant we tried to make the Ormerod easier and safer to build than the Mendel and Huxley machines. With the Ormerod, when things go wrong, it really is 'new and interesting'!

Ian
RepRapPro tech support