Printer stopped before finishing print

I've just done a lengthy print job, and the Ormerod stopped just before finishing. It has either finished or nearly finished laying down filament. It didn't execute the standard commands at the end of the gcode file to move the print head and turn off the heaters, it left the print head in contact with the work and the heaters on. Has anyone else experienced this?

Edited 1 time(s). Last edit at 12/24/2013 06:03PM by dc42.

It has happened to me once only, printing from the SD card. I thought at the time that either slic3r had been interrupted during g-code generation or that uploading to SD had failed. In fact it is in one of the pics I posted earlier (the offset X0, poor surface finish and 1/4 of the height of the finished part). That day i restarted the print (uploaded again and launched an SD print). Never happened since so hard to tell if we have done something wrong or if it is a bug.

For info, have printed around 25 parts and had the problem once...

You might want to take a look at this topic which describes how I've solved my random printing hang-ups: Duet 3.3V supply quality

Or then again, maybe not :-( That's the trouble with intermittent faults; you do something that in theory might help - and lo and behold the fault seems to go away. But not so much the following day.

Today I can't get through this particular print without it stopping part-way through each time.



I've tried using the supplied ATX, a 25Amp Bench supply and with Duet powered by USB. No combination has proved to be reliable.

Not so clever is that the heated bed remained hard-on in one instance. The Hot end is also typically left running with PWM fixed at around 20% 1KHz period. I tried some freezer spray on it to see if the loop was running but it was just stuck at the same duty cycle. Unsuprisingly both the USB serial interface and network interface remain unresponsive.

A quick poke of the reset button brings it all back instantly.

Edited 1 time(s). Last edit at 12/28/2013 09:58AM by Radian.

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RS Components Reprap Ormerod No. 481

Radian

Well when you put all your eggs in one basket. If the Processor crashes you loose control of everything. It might be nice to have a watchdog which will knock the heaters off if the processor is no longer functioning. I am thinking of possibly using a seperate controller to regulate the bed temperature. I did notice a very cheap temperature controller on ebay a few days ago. The sort of thing I have used at work cost about 50 pounds and use an NTC, I have been able to achieve 0.1 K temperature stability using these. It would be necessary to keep the thermistor connected to the Duet so it knows when it is ok to print.

Rory

The processor has a builtin watchdog timer that can reset the processor if it isn't kicked for a while. It should be a simple matter to enable this in the firmware, along with a status indicator to indicate whether the last reset was caused by power on, reset button, or watchdog.

Ian, are there any forums where we can suggest improvements to the Duet firmware, and improvements to the Duet electronics?

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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].

This whole affair reminds me of an occasion many years ago when I was involved with one of the first businesses to acually run on PC. It was a laser game centre. If the PC Crashed then the game was over and all the customers money had to be refunded. I was the sound and lighting contractor. They mentioned that the PC sometimes crashed so I built them a mains filter unit and they seemed happy. Later they built another centre miles away and the problem was so bad one of the partners was all for closing down. They asked for my help so I said being so far away I can only go once and install the ultimate solution a UPS. Well they were delighted and more than happy to pay a hefty fee for my days work.

We don't really know what the problem is, brownouts are one suspect where the mains is briefly interrupted possibly not visible to the naked eye but enough to stop a processor. Power supply regulation is another suspect when the heater bed switches off the 12V rail surges up to 20v for several nanoseconds apparently, presumably it could equally drop to say 4 volts briefly when the bed switches on. The processor itself may not loose power but if it commands a motor output which then does not respond properly an error could occur. The idea of running the processor from a seperate supply such as a powered USB seems appealing. This could be made battery backed more easily. Firmware would still be needed to recognise the mains failiure and pause printing untill power and temperatures are restored.

Rory

Edited 1 time(s). Last edit at 12/29/2013 05:00AM by Rory166.

Quote
Radian
Not so clever is that the heated bed remained hard-on in one instance. The Hot end is also typically left running with PWM fixed at around 20% 1KHz period. I tried some freezer spray on it to see if the loop was running but it was just stuck at the same duty cycle. Unsuprisingly both the USB serial interface and network interface remain unresponsive.

A quick poke of the reset button brings it all back instantly.

That is very interesting, sounds like similar problems I have seen at work. The fact the PWM continues means the SAM peripherals are still being clocked and have not been reset (due to watchdog or power on reset). However, the software becomes unresponsive either due to a bug in the software (stuck in a loop somewhere), or the processor core has had a voltage dip and had locked up (e.g. PLL lost lock) or has executed some duff instructions and ended up running junk code outside programmed code.

The "stuck in brownout" state is quite nasty, because the CPU does not reset nor does the software run correctly. However, turning on the hardware watchdog in the SAM (mentioned above) is effective. Additionally turning the Brown Out Detect function helps to handle the condition much more cleanly. In the SAM you can also get the Reset condition at start up and act accordingly.

We use all of these features in our motor controllers, which have to cope with all kind of nasty EMC/ESD conditions. In our case, we do a "hot" restart and fly catch the motor, so the reset can be invisible. That is probably not possible in the printer case, because the state is lost. At least the controller could tell the host "I've had a watchdog reset etc", and possibly recover.

Of course, this does not identify the cause of the brownout (if that is the case), it could be something like a voltage spike causing a latch up in the CPU, etc. Really the CPU should be able to run clean even in this type of application. I also wouldn't rule out a firmware bug until all causes have been found, might even be my first avenue of investigation. Even something simple like flashing an LED in the main loop could help diagnosis.

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Quote
dc42
The processor has a builtin watchdog timer that can reset the processor if it isn't kicked for a while. It should be a simple matter to enable this in the firmware, along with a status indicator to indicate whether the last reset was caused by power on, reset button, or watchdog.

Ian, are there any forums where we can suggest improvements to the Duet firmware, and improvements to the Duet electronics?

Apart from this forum, I suggest raising an issue in the respective Github tracker?

Or the other way, clone the repo, make the improvements, then send pull request

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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

USB lead and PC end connection considerations.

In another post I mentioned I used a mBed processor module [mbed.org] and I recall some issues they/we had that 'could' affect some builds here, so might at least be worth being aware of this.

USB leads are not equal in quality.
Try a different lead as lead issues can affect the power voltage drop and signal performance.
It's hard to visually identify 'quality', so select a trusted brand name.
Some users found the shorter leads (for obvious reasons) are better.

USB ports.
Apparently the typical laptops/PCs built for Windows 7 are much more fussy on the leads that work reliably. Win XP era builds are much more tolerant.
Possibly related to the above if your laptop has ports with a choice of support USB 3.0/2.0 or USB 2.0 only then try to use the USB 2.0 port as these 'seem' to be more suitable for USB 2.0 type peripherals.

I realise this doesn't affect SD card issues, but as it may affect printer communications I thought this was a good post topic.