Multiple Super Weird Failure Modes

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EricPeterson
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Joined: Tue Aug 18, 2015 6:15 pm

Multiple Super Weird Failure Modes

Post by EricPeterson » Thu Feb 21, 2019 8:04 pm

I started getting filament sticking in the throat of the hot end during setup. This is a single extruder V4 24 volt M2 that's run several hundred kg of ABS and PLA through four different nozzles on two different hot ends. It's got a number of mechanical mods to make it more robust -- a miniature I-beam under the longer rail bracket, a redesigned extruder motor mount, aftermarket fans -- but no electrical or code mods. Just wouldn't extrude. I noticed that the temperature of the hot end was drifting down. I'm using S3D, so I manually set Extruder temp again to 245, and it seemed to come back up... but then the downward drift would start again and filament started to bind, the drive gear chewing a little crescent out of the filament.

The hot end had a lot of hours on it, and the nozzle was pretty worn from cleanings and use. I installed a spare. On reboot and starting up S3D, I couldn't get a good connection. Rebooted Win10 PC and M2. Restarted S3D 4.1.1. Connected manually -- under Win10 I notice it never automatically connects, which seemed to be the rule under the old Win7 installation. Wanted to adjust the gap first so I started heating the build plate to 100. Temp ran up to 54 degrees, and then the extruder temp readout zeroed from ambient and the platform temp started falling. Set it to 100 again. Climbed to 65... and then started falling back towards ambient.

Restarted M2 and S3D. Got a good connect. Ran autotune M303. Autotune seemed to complete OK, quick, and I saved the loop constants via M500. Set platform temp to 100. Platform temp climbed to 40... and then started to fall back to ambient. Tried again... climbed to 60 and then started falling back.

Tried some platform jog commands -- not the extrude + or - because extruder temp was too low to allow extrude motion .... and S3D echoed "Printer stopped deu to error. Use M999 to reset and then reset temperature."

Issued M999. Platform heater indicated still ON. Rebooted M2 and S3D. Got a good connect. Issued command to heat platform. Issued command to heat extruder. Extruder heated to 180 and then started falling back to ambient. Platform heated to 70 and then started falling back to ambient. Re-issued both temperature demands, and both platform and extruder started to climb back to demanded temps.

Got plate and extruder heated to 100 and 245 respectively. Fed new ABS filament of a type we use all the time. Feed acts weird, comes out in fits and spurts like it's sticking. Seems like the nozzle just isn't hot enough, but it shows 245. Then... "Printer stopped deu to error. Use M999..."

Rebooted S3D and M2. Seems to be working OK now. Platform holds temp. Can extrude manually and seems like I'm getting good melt and feed.

Ambient is constant -- commercial facility. We have five M2s... been running them for years. Never saw anything like this before. What happened? And can I trust the machine to start some bigger printers?

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ednisley
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Re: Multiple Super Weird Failure Modes

Post by ednisley » Thu Feb 21, 2019 11:57 pm

EricPeterson wrote:
Thu Feb 21, 2019 8:04 pm
What happened?
Sounds like the cartridge heater is failing, so replace it.

While you're at it, replace the thermistor, because some of the symptoms implicate it, as well.

They're not exactly consumables, but they don't last forever. It seems like you've been removing and replacing the nozzle on a regular basis, so you've been joggling those fragile wires more than they can withstand.

Until you replace the heater & thermistor, tag that M2 as Down for maintenance - DO NOT USE.

EricPeterson
Posts: 21
Joined: Tue Aug 18, 2015 6:15 pm

Re: Multiple Super Weird Failure Modes

Post by EricPeterson » Thu May 02, 2019 8:32 pm

Yep. That was one problem. Thank you. The hot end was bad, heater and sensor both. The replacement we had in stock was DOA with a bad connection to the sensor out of the bag. A second replacement allows the M2 to heat and hold temperatures perfectly, and the control interface -- S3D -- shows good solid temp readings through the ranges. No more temp disconnects, zero readings, or similar issues.

Other project responsibilities kept me from looking at this for a few months. Just finished putting it back together after checking the temps with the replacement replacement hot end assembly. Now the X and Y axes work perfectly, and it heats and holds temperature perfectly, but the z-drive is loose -- chatters and backslips when driving and doesn't hold when idle -- and the extrude drive won't activate or drive at all ( yes,with the hot end indicating a full 245 degC). And, ah, and this is new. The computer won't detect the correct USB port to the printer any more when S3D starts up. Used to keep the selection of the USB port persistent... now it has to be set every blessed time. Comm monitor interface shows commands are getting through via the USB link, but the extrude drive appears to be dead. And the z-drive is still operating at vastly reduced torque. If I turn the speed way, way, way down it will actually run... but it still can't hold. Anything other than a minimal bump down at normal operating speeds makes it stall and slip.

Just had my tech in here who maintains the units. He's never seen this in any of the units. Wiring all looks good. The wiring to the lift motor isn't subject to any flex....

Have we blown a motherboard?

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ednisley
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Re: Multiple Super Weird Failure Modes

Post by ednisley » Fri May 03, 2019 2:34 pm

EricPeterson wrote:
Thu May 02, 2019 8:32 pm
And, ah, and this is new
From the look of it, you've been fiddling around with that printer in a big way, which can cause all manner of problems while solving others.

If you've made any slicer configuration / software / firmware changes, restore the original versions. In the firmware, verify the motor current settings and suchlike.

Take a look at the RAMBo power connections, because nobody expects the screw terminals to work loose. Glitchy power causes all manner of interesting problems.

You may have disconnected either or both of the Z-axis and extruder motors with the power on, which can destroy the driver chip on the RAMBo board. Although you didn't deliberately disconnect the motor, that makes no difference: all it takes is joggling the connectors with the power on; we all do it occasionally and mostly it doesn't matter.

Verify the cable connectivity by taking everything out of the braided loom (which is a major pain), then closely inspecting the wires and connectors for damage, perhaps measuring the resistance while flexing the wires. If you find a destroyed wire or connector pin, then you've found the problem. Unfortunately, wire failures can cascade to the driver chip.

If everything looks good, then it's most likely the driver.

As far as the USB problems go, if you're using Windows, then all bets are off. Had any updates recently? [sigh]

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