Service Bulletin: Thermistor Issue in Aerostruder and Dual Extruder v3 Tool Heads

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Orias
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Service Bulletin: Thermistor Issue in Aerostruder and Dual Extruder v3 Tool Heads

Post by Orias » Fri Feb 23, 2018 4:36 pm

Thank you for your patience while we investigated and confirmed our findings.

There have been some reports that some printers equipped with the Aerostruder and Dual Extruder v3 tool heads were encountering temperature related error messages, and had difficulty maintaining and/or displaying the correct temperature.

After investigation we found that connectors for the thermistors in some Aerostruder and Dual Extruder v3 Tool Heads were insufficiently crimped by the manufacturer, a defect that was missed in our quality control process. We apologize for any inconvenience this may have caused and appreciate your business.

Based on our recent samples, we anticipate the number off affected units to be 5% of fulfilled orders, or less. Product quality and customer support have always been and remain among our highest priorities. View the full service bulletin for the potentially affected serial number range, steps to diagnose, and a no-cost resolution here.

Visit LulzBot.com/Support for a list of all past service bulletins.

GJennings
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Re: Service Bulletin: Thermistor Issue in Aerostruder and Dual Extruder v3 Tool Heads

Post by GJennings » Fri Feb 23, 2018 7:00 pm

Where is the serial number located? Mine was purchased on 11/30/17, and I can't find any markings on either the toolhead or packaging.

Galadriel
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Re: Service Bulletin: Thermistor Issue in Aerostruder and Dual Extruder v3 Tool Heads

Post by Galadriel » Sat Feb 24, 2018 7:14 am

There should be a sticker placed somewhere on the back of the toolhead where it rests against your extruder mount that will have the complete serial number for the toolhead. I attached an example picture for placement on the Dual Extruder v3.
V3 dual serial number sticker.jpg

GJennings
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Re: Service Bulletin: Thermistor Issue in Aerostruder and Dual Extruder v3 Tool Heads

Post by GJennings » Sat Feb 24, 2018 11:44 am

My V3 does not have a sticker. Not even an e-steps sticker.

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Orias
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Re: Service Bulletin: Thermistor Issue in Aerostruder and Dual Extruder v3 Tool Heads

Post by Orias » Sat Feb 24, 2018 11:59 am

Reach out to the support team at LulzBot.com/Support and they may be able to find your probable serial range based on your purchase method. Include your order number. How is your tool head performing?

GJennings
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Re: Service Bulletin: Thermistor Issue in Aerostruder and Dual Extruder v3 Tool Heads

Post by GJennings » Sat Feb 24, 2018 12:19 pm

The temperature readings are a little noisy, but the toolhead works okay. Printing polycarbonate at 280C shut down once with an over-temperature spike. I wiggled the harness everywhere (sensor to rambo board) but couldn't get the indicated temperature to also wiggle. Of note in my case - the noisy temp readings only occur when the extruder temp is in the range where the PID controller is active (set point +/- a couple of degrees). This leads me to believe that my toolhead doesn't have a crimp problem, more of a system noise problem. I also had similar behavior with my dual V2.

I ended up putting a firmware band-aid on the problem. I added a slew rate filter to the extruder temperature measurement to limit the dynamics to what the system can normally produce (about 3 degrees C per second). So far so good.

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Orias
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Re: Service Bulletin: Thermistor Issue in Aerostruder and Dual Extruder v3 Tool Heads

Post by Orias » Sun Feb 25, 2018 12:01 pm

We'd love to see those changes, where did you make them? Also, what firmware version are you running with that modification?

GJennings
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Re: Service Bulletin: Thermistor Issue in Aerostruder and Dual Extruder v3 Tool Heads

Post by GJennings » Sun Feb 25, 2018 12:12 pm

I PM'd the changes to Marcio about 2 weeks ago (in response to the similar troubles that others are having), but he seems pretty busy at the moment. I am currently using a modded (bltouch and a couple of custom toolheads) 1.1.8.8. The changes are all in temperature.cpp. Here's a trimmed down version of the PM:

If you look at the extruder temperature dynamics, the system is only capable of producing about 1 degC/second of temperature slew. Anything faster than this almost certainly came from measurement noise. The noise itself usually looks spiky (i.e. the occasional noisy reading on top of small PID wander), but the large errors cause the control loop to try really hard. When I was printing polycarbonate I couldn't go above 275C because the glitches would invariably trigger a shutdown.

I was lazy and didn't characterize the temperature update rate with diagnostic messages. I just poked around in the code (I am currently fiddling with 1.1.8.4) and gleaned/guessed that the cycle time was 164 mS. So I made a slew limiter based on that value. I tried limiting the rate to 1 deg/second which kills off everything including ringing in the PID controller (too filtered) and 5 deg/second which lets through more noise than I like. I verified that autotune produces very similar gain numbers with the filter disabled and with it set to 3 deg/second, so the PID controller shouldn't be too irritated. The filter will probably allow a bit higher D gain since it is no longer chasing shadows.

Anyway, here's the code (in temperature.cpp), do whatever you want with it.

Gordon

#define TEMP_UPDATE_PERIOD 0.164
#define TEMP_SLEW_RATE 3.0
float tempslew(float last, float next)
{
static int init = 100;

if(init)
init--;
// updates at 164mS or ??
if(init)
return next; // default nop behavior

if(next > last) // upslew
{
last += TEMP_UPDATE_PERIOD * TEMP_SLEW_RATE; // x deg/sec slew
if(last > next)
last = next;
}
else if(next < last) // downslew
{
last -= TEMP_UPDATE_PERIOD * TEMP_SLEW_RATE;
if(last < next)
last = next;
}
return last;
}

void Temperature::updateTemperaturesFromRawValues() {
#if ENABLED(HEATER_0_USES_MAX6675)
current_temperature_raw[0] = read_max6675();
#endif
HOTEND_LOOP()
current_temperature[e] = tempslew(current_temperature[e], Temperature::analog2temp(current_temperature_raw[e], e));
// current_temperature[e] = Temperature::analog2temp(current_temperature_raw[e], e);

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Orias
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Re: Service Bulletin: Thermistor Issue in Aerostruder and Dual Extruder v3 Tool Heads

Post by Orias » Mon Feb 26, 2018 1:25 pm

Sweet, thanks for sharing!

eirikso
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Re: Service Bulletin: Thermistor Issue in Aerostruder and Dual Extruder v3 Tool Heads

Post by eirikso » Sat Mar 03, 2018 11:10 am

My aerostruder seems to have this exact problem. See the attached image. Would it be possible to solve this with the firmware mentioned here?
Attachments
Screenshot 2018-02-26 08.02.59.png

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