Cold nozzles reading 240° C

Jetguy
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Re: Cold nozzles reading 240° C

Postby Jetguy » Tue Aug 21, 2018 6:27 pm

Again, there now appear to be 2 separate faults.
#1 has been and the topic of this thread is that the mainboard cannot detect a 14 wire cable break carrying the thermocouple temp sensor data back to the mainboard. That's why when it breaks the same previous temp is reported rather than an error message or a high or low temp. This is extremely dangerous because again, the same valid (within a normal expected range) temp is reporting even though we know full well that's not the actual hotend temp. Since the mainboard makes the decision of heater on or heater off based on the reported temp (temp control 101), then it cannot make a safe valid decision if it does not know a fault condition from a normal condition. Software cannot "fix" that.

#2 Now, we have some reports of not ONLY the 14 wire cable failing (previously a ribbon cable on the N series), but now, the much heavier wire and larger connector that has not been a problem on the N series- we have a proven failure on at least one Pro2 series.

Again, cannot stress enough, these faults are different and should not be lumped together under a support item because the results and troubleshooting are VERY different.
If a heater cable break connection- worst that happens is you cannot heat and your print fails.
If your 14 wire temperature data cable carrying the info on the hotend temp breaks and the mainboard hardware fails to detect it, then firmware has no chance in hell of detecting it, and now you can have a heater completely out of control. it will either go cold or go hot, but again, with a constant and false temp as the input to the heater control system, if it doesn't know constantly the actual hotend temp- it then cannot "control" it.

Ilia T
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Re: Cold nozzles reading 240° C

Postby Ilia T » Thu Aug 23, 2018 8:54 pm

Same issue here. We bought new Raise 3D Pro2 Plus 3D printer. We did a few printer works with no issues including pretty long work with big parts. But after a few prints we found the filament jams somewhere in middle of long printing work.

Here are our findings I hope can help to solve the issue as soon as possible.

Here is the video with one of printing job the issue happened.

https://www.dropbox.com/s/rk0nj3525fljj ... s.mp4?dl=0

It happened with all filaments including Raise3D premium PLA filament.

As you can see nozzle temperature is significantly higher than the target temperature (215 C) and jumps between 270-290 C. Please note that both nozzle temperature jumps the same. But the right nozzle should be cold. The filament is jammed because of it looks like the real nozzle temperature is lower. The machine reads for some reason wrong temperature (higher than real temperature) and does not heat the nozzle so the filament is cold and jammed in the nozzle.

After I stopped printing work the nozzles temperature on the display instantly dropped to 37 C. That is weird and I'm do not know if this is cable or contacts related issue or software glitch or something else.

Image



Another thing we found might will give you glues to the issue source. We found that the extruder board is sensitive to temperature. The chamber of the printer is getting pretty hot and stepper motors near the board is getting hot too. So maybe this is the clue in the issue. Or maybe not.

Here is the video to demonstrate the board temperature sensitivity. We set both nozzles temperature to 220 C and blown warm air from heat gun at low temperature setting on the board. You can see how this affects on the temperature reading on the video.

https://www.dropbox.com/s/z18ei09e5cfxe ... e.mp4?dl=0

We also performed test with cold compressed air. Here is another video. You can see that this affects reading too.

https://www.dropbox.com/s/dg9kkk6wgsvju ... e.mp4?dl=0


Wiggling the wires on the board or manually moving the print head around do not affect temperature readings.



Another thing out EE engineer noticed is that the colorful fires plug in the extruder board has inappropriate wires gauge (too small) or wires style (single line wire) crimped in the connectors. The connectors and wires can come loose or lost contact with each other after some temperature expansion cycles and printer head moves

Image



For safety related issue quick fix could be on software level. The algorithm at least should sens inappropriate or weird or unexpected temperature sensor reading behavior. Say if board sends energy to the nozzle and sensor does not reflect temperature raising during 10 sec it aborts the printing job and sent message to the screen to inform user about the issue. Or if the temperature jumps like crazy up and down more than 10C during short period of time it aborts the printing job and sent message to the screen to inform user about the issue. There is a lot of ways to do it on software level.

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Vicky@Raise3D
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Re: Cold nozzles reading 240° C

Postby Vicky@Raise3D » Fri Aug 24, 2018 7:35 pm

Ilia T wrote:Same issue here. We bought new Raise 3D Pro2 Plus 3D printer. We did a few printer works with no issues including pretty long work with big parts. But after a few prints we found the filament jams somewhere in middle of long printing work.

Here are our findings I hope can help to solve the issue as soon as possible.

Here is the video with one of printing job the issue happened.

https://www.dropbox.com/s/rk0nj3525fljj ... s.mp4?dl=0

It happened with all filaments including Raise3D premium PLA filament.

As you can see nozzle temperature is significantly higher than the target temperature (215 C) and jumps between 270-290 C. Please note that both nozzle temperature jumps the same. But the right nozzle should be cold. The filament is jammed because of it looks like the real nozzle temperature is lower. The machine reads for some reason wrong temperature (higher than real temperature) and does not heat the nozzle so the filament is cold and jammed in the nozzle.

After I stopped printing work the nozzles temperature on the display instantly dropped to 37 C. That is weird and I'm do not know if this is cable or contacts related issue or software glitch or something else.

Image



Another thing we found might will give you glues to the issue source. We found that the extruder board is sensitive to temperature. The chamber of the printer is getting pretty hot and stepper motors near the board is getting hot too. So maybe this is the clue in the issue. Or maybe not.

Here is the video to demonstrate the board temperature sensitivity. We set both nozzles temperature to 220 C and blown warm air from heat gun at low temperature setting on the board. You can see how this affects on the temperature reading on the video.

https://www.dropbox.com/s/z18ei09e5cfxe ... e.mp4?dl=0

We also performed test with cold compressed air. Here is another video. You can see that this affects reading too.

https://www.dropbox.com/s/dg9kkk6wgsvju ... e.mp4?dl=0


Wiggling the wires on the board or manually moving the print head around do not affect temperature readings.



Another thing out EE engineer noticed is that the colorful fires plug in the extruder board has inappropriate wires gauge (too small) or wires style (single line wire) crimped in the connectors. The connectors and wires can come loose or lost contact with each other after some temperature expansion cycles and printer head moves

Image



For safety related issue quick fix could be on software level. The algorithm at least should sens inappropriate or weird or unexpected temperature sensor reading behavior. Say if board sends energy to the nozzle and sensor does not reflect temperature raising during 10 sec it aborts the printing job and sent message to the screen to inform user about the issue. Or if the temperature jumps like crazy up and down more than 10C during short period of time it aborts the printing job and sent message to the screen to inform user about the issue. There is a lot of ways to do it on software level.


Please reach to our technicians to figure the reason of the issue you are currently facing with.
Out of safety concern, please do not run any long print until the issue has been solved in case improper overheating.

And thanks for your suggestion. We are currently trying to develop a fix from software side. Hope can achieve some result as soon as we can.

KS_Husker
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Re: Cold nozzles reading 240° C

Postby KS_Husker » Mon Aug 27, 2018 4:49 pm

Man, I hope they get this temperature issue resolved soon. I'm wanting to buy one of these printers as well, but I'm not so sure because I keep reading about this problem everywhere. Raise, Please get this fixed quickly. This is a big deal. I am also in the process of having my employer buy a couple of these machines and I don't want them to think I steered them the wrong direction with their purchase!!

Jetguy
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Re: Cold nozzles reading 240° C

Postby Jetguy » Mon Aug 27, 2018 6:53 pm

KS_Husker wrote:Man, I hope they get this temperature issue resolved soon. I'm wanting to buy one of these printers as well, but I'm not so sure because I keep reading about this problem everywhere. Raise, Please get this fixed quickly. This is a big deal. I am also in the process of having my employer buy a couple of these machines and I don't want them to think I steered them the wrong direction with their purchase!!


And to that, I say I will not accept this as a software only fix, I know better. If that is raise3D's official answer, that they are going to attempt the cheap way out and patch software and pray it prevents a serious safety condition (keep in mind, this does JACK SQUAT for printing and or not being able to print due to a legit hardware failure), then this is still now firmly listed on my do not buy this printer list.
It will remain there until an acceptable hardware fix is tested and proven- potentially combined with additional software patches, but software cannot be and will not be the acceptable only fix.

I offered to fix this for them. I offered to test and provide details and engineering fixes. They refused.
Figure it out- here is the line in the sand. I'm not buying one and again, I'm telling others not to buy this printer.
This is beyond not acceptable. The answers you fellow customers are getting are not technically acceptable. You take it because you may not know any better, you might not be on the level of hardware and firmware understanding, but seriously, listen to what I'm saying, I'm the one who came up with a fix for the similar problem on the N series. Relying on software patches to identify a condition where 2 boards (the remote thermocouple extruder head breakout and the mainboard actually controlling the heater) might stop communicating (broken cable or failing connection) mid print and just so happens to be controlling a heater in the process is NOT acceptable. And then it appears at least one user, maybe more has troubles with the heater cabling on top of this mess. If it was just one user and fluke, that would be one thing, but a little reading and searching in the forum, this is a real legitimate problem.

Other manufacturers handle such faults properly. Let me show you an example by SeeMeCNC. They had a wiring fault for missing grounding and they offered a PROPER hardware fix and proper safety bulletin. http://forum.seemecnc.com/download/file.php?id=15815 You don't see Raise 3D doing that for N series owners and sure as heck, they are trying to sweep this under the rug for Pro2 series owners. They want this thread quiet and to just go away. I mean really, who tells users to stop printing, and then isn't also issuing safety bulletins and offering proper fixes- Raise 3D, that's who.

Again, just want to make it clear- look at the very title and first post of this thread. You have a machine that you know the nozzle is cold and the mainboard is reading a temperature that is different than the actual extruder really is. Since the mainboard makes a decision of heater on or off, and is not throwing an error message because the reported temp is within reasonable and somewhat expected constraints, the motherboard has NO idea it's not getting a real valid temperature report. And yes, while they can and SHOULD implement firmware checking that the heater should rise a certain temperature in a certain time period- that doesn't fix the problem. It's just secondary safety layerworkaround because at the end of the day it's still guessing based on the data the mainboard is actually seeing. Your function is only as good as your data. A proper hardware mod INSTANTLY the second there is an interruption throws a fault condition. This is simply how it should be and why this lesson was not learned from the N series is beyond logic and reason. Further, I asked about this BEFORE a single user had one of these Pro2 series and I was lied to by tech support saying this was fixed/resolved. In other words, either tech support didn't know or they were forced to give an answer by management and marketing, and now that answer is proven to be a lie. I'm not standing for this and neither should you.

Ilia T
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Re: Cold nozzles reading 240° C

Postby Ilia T » Tue Aug 28, 2018 12:11 am

Vicky@Raise3D wrote:Please reach to our technicians to figure the reason of the issue you are currently facing with.
Out of safety concern, please do not run any long print until the issue has been solved in case improper overheating.

And thanks for your suggestion. We are currently trying to develop a fix from software side. Hope can achieve some result as soon as we can.

We already contacted Raise3d technicians. Thank you for the update.

I do not know if somebody tried this solution. We designed and printed support bracket for the 14 wires cable. During print-head motion this cable wiggles the plug and the crimped connectors in the plug. This support bracket holds the portion of the cable and prevents the cable wiggling and flexing in the near the plug area. We did not test big prints yet. Will see if it helps.

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Vicky@Raise3D
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Re: Cold nozzles reading 240° C

Postby Vicky@Raise3D » Tue Aug 28, 2018 4:31 am

About hardware side, there has Pullup Portection originally included in Pro2's controller board which is used to trigger an Error when reaches to max value when losing connection of ribbon cable. Which is similar to the thermal protector add-on on N series' printer.
About software side, based on the strong CPU of Pro2 series, we are going to add an optimized software thermal protection, which is used to compare the real heating progress with the defined one. If they don't match with each other, it will trigger an Error too.

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Vicky@Raise3D
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Re: Cold nozzles reading 240° C

Postby Vicky@Raise3D » Tue Aug 28, 2018 4:36 am

Ilia T wrote:
Vicky@Raise3D wrote:Please reach to our technicians to figure the reason of the issue you are currently facing with.
Out of safety concern, please do not run any long print until the issue has been solved in case improper overheating.

And thanks for your suggestion. We are currently trying to develop a fix from software side. Hope can achieve some result as soon as we can.

We already contacted Raise3d technicians. Thank you for the update.

I do not know if somebody tried this solution. We designed and printed support bracket for the 14 wires cable. During print-head motion this cable wiggles the plug and the crimped connectors in the plug. This support bracket holds the portion of the cable and prevents the cable wiggling and flexing in the near the plug area. We did not test big prints yet. Will see if it helps.



For the coming batches of Pro2 series printers, we have added extra fixtures to tighten the ribbon cable to avoid moving of the connector on terminal.
2.jpg
1.jpg

Jetguy
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Re: Cold nozzles reading 240° C

Postby Jetguy » Tue Aug 28, 2018 11:14 am

Vicky@Raise3D wrote:About hardware side, there has Pullup Portection originally included in Pro2's controller board which is used to trigger an Error when reaches to max value when losing connection of ribbon cable. Which is similar to the thermal protector add-on on N series' printer.
About software side, based on the strong CPU of Pro2 series, we are going to add an optimized software thermal protection, which is used to compare the real heating progress with the defined one. If they don't match with each other, it will trigger an Error too.


Vicky, how can this be? Now admittedly, I do not have a control board set because Raise3D will not sell one or loan one, however, the results users are having basically say this cannot be true that there are pullup resistors.

This condition would then be impossible.
Again the title of this thread, nozzles read 240C at the mainboard, the physical nozzle is cold.
If using Analog thermocouple amps AD597, then it's 10mV per degree C, so logically analog voltage is 2.4V. If you used a pullup, let's say to 3V and the cable opened circuit, then the pullup pulls it to 3V = 300C. Maybe 3.3V pullup and the reason I say that is that because I know your new processor is a 3.3V logic. That's really not high enough as a scheme to support the printer temps you say it will reach you must be using a 5V full scale 0-500C, meaning the pullup should be to 5V (provided the ADC pin can handle 5V). When the cable opens circuit, then the mainboard and thus the LCD should instantly say near 500C for second (because the reported temp is rising fast and likely triggers the max limit and may show that screen before 500C) point being, the instant the cable is unplugged it should go into safety.

Bottom line, if you want this to stop, prove to me and your customers by making a video. Demonstrate by powering on the printer, waiting for it to boot, showing it is reporting room temp. Then command the extruder heater to heat to 215C. Wait for it to reach 215C, then unplug the 14 wire connector. The printer MUST go into safety mode the instant the cable breaks connection and should report a max temp error(or you can have a custom error message, but should trigger on max temp), then I might believe there is actually the resistors you say that are there are there. Again, to date, the users and owners of this printer are posting reports that say exactly the opposite, the printer does not go into error mode, the printer mainboard does not know when the cable breaks, the mainboard is often caught displaying the last good temp read before the cable break occurred. That all is clearly pointing that these resistors are not there. So either you have the most messed up firmware on the planet, or you have some other serious problems, but again, the fact this topic even exists is a serious fault.
Last edited by Jetguy on Tue Aug 28, 2018 11:52 am, edited 1 time in total.

Jetguy
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Re: Cold nozzles reading 240° C

Postby Jetguy » Tue Aug 28, 2018 11:29 am

Also, any user willing to prove the point, can you instead if Raise3D will not make the video.
Again, it's as simple as unplugging a known low voltage mostly signal cable (there is 12V fan power in the cable but it's running fans at roughly 0.4-0.5A combined for all 3 fans) while the printer is on, the risk is limited but the goal is to prove your printer has safety built in and performs as expected. If it passes, great, you have a good safe printer as Raise 3D is implying. If it doesn't, we have a serious problem on our hands. More important, you as a user should understand this and why this is so serious as again, if the mainboard cannot detect this cable break, then this can and will cause a problem if the cable breaks mid print. Again, the printer should instantly go into max temp error the second that cable breaks connection if there are proper resistors installed and they are pulling up to 5V logic which represents 500C. That in turn is double safety because firmware won't allow a temperature set point that high so it a sure bet that 500C is higher than your setpoint during a print, so the heater is instantly off when reported temp is higher than set temp (that means no special safety firmware is required, it fails safe by default). Again, the problem is, these very problem reports and posts by actual Pro2 owners not only indicate that this is not happening, but go a step further and say that like the N series with the fault, a previous valid temp read (in this case 240C) was read when we know the nozzle is cold. That is the identical problem as seen in the N series because the analog voltage signal is basically stored in a capacitor in the analog to digital conversion section of the processor. It's high impedance and with no pull up resistor, it wants to remain the previous value. You might get spurious readings as the cable makes and breaks connection attempting to thus change the voltage at the ADC and change the reported temp, but the point being, it's not throwing an instant error the first time the cable breaks connection.

The whole reason for harping on this is 2 things:
#1 safety- this is simply the accepted safety fault requirement for a remote thermocouple due to the risk of thermal runaway.
#2 your print failure- if the fault is not detected the instant it happens and does not go into safety error condition, that then forces a save point and stops the printer. The theory is, you now have a save point and once you fix the cable or connector, in theory you can restart the printer (again, you just did a cable repair to fix the fault) and print recovery option exists to resume the print where it left off. The opposite side of the coin and what we are seeing as a result is if the break in communication of the actual hotend temp is not detected the instant it happens, then your printer continues to try to print. The nozzle will either heat up uncontrolled or cool down depending on the relationship of the reported temp to setpoint temp at the time of the break. Actual less than setpoint= heater on, = to or greater than setpoint = heater off. Again, your printer continues to "attempt" to print during this undetected fault period, and your print suffers either extruder extrusion from the nozzle cooling off and jamming, or overheats the filament in the case of uncontrolled heating. Even if they have this other firmware based safety fallback condition that is checking for the heater to rise a certain temp when the heater is on, that code does not work well right around the setpoint temp and by default in all previous code examples, only works 10C away from the set point. In other words, your extruder would have to be 10C cooler than the setpoint, for the safety code to even be invoked. If they make it tighter say 5C or less, then you run the risk of false positives, when the extruder PID is not well tuned or influenced by fans. That's why I keep harping- firmware alone cannot be the ONLY safety. It only catches the extremes and then only when a hardware fault like and ADC that keeps reading a temp within range it's not going to trigger a fault.

If those pullup resistors existed- then this is the story you guys would be telling, your printer stopped, came up with an error message. You fixed the cable, powered on the printer and were able to resume the print. That's how it should work and that's exactly what I helped to develop for the N series. So why isn't the Pro2 acting the same way?
Last edited by Jetguy on Tue Aug 28, 2018 12:02 pm, edited 1 time in total.

Jetguy
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Re: Cold nozzles reading 240° C

Postby Jetguy » Tue Aug 28, 2018 11:41 am

Again, the scenarios that could explain this topic of a printer reading 240C while the nozzle is cold:
#1 ADC pin is floating with no pull-ups and thus reads the last known good temp that charged it to 2.4V and is not discharging or charging to a higher voltage via pullup or pulldown resistors. This seems the most logical of all since we know users have messed with cables and then the printer appears to work for a time before the cable breaks connection again.

#2 Somehow, beyond logic or reason, the AD597 analog thermocouple amplifier is putting out 2.4V exactly when in fact, the thermocouple is known to be cold. A shorted thermocouple reads room temp or zero depending on when the short happened, an open circuit thermocouple reads 500C because that is a built in safety condition check of the AD597. So again, this would indicate a blown AD597 if this is the source of the 2.4V, but that then would mean to fix this printer, you would have to replace the AD597 by replacing the extruder head breakout. You could not print with this printer and messing with the cable would not solve the problem.

#3 The ADC port of the processor at the mainboard was damaged and internally is stuck reading a fixed temperature. Again, this would require mainboard replacement for this printer to ever print again. The mainboard simply would read 240C every time you turned it on, regardless of whatever input voltage was applied to the analog pin from the remote thermocouple breakout temp sensing. This includes the safety pullup resistors when the cable is unplugged while the printer is on. Again, if cable plugged in or cable unplugged resulted in the same temp displayed, then this typically indicates a blown ADC and thus as a replaceable part, the mainboard would be considered bad.

Jetguy
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Re: Cold nozzles reading 240° C

Postby Jetguy » Tue Aug 28, 2018 3:27 pm

More technical digging on what we can find in public domain.
Looking at a mainboard picture from a supplier the processor is an STM32H7 series. I can only make out to about STM32H743 from zooming in on the picture and know it's one of the quad flat pack style pin packages (not a BGA).
Motion-Controller-Board-50405013A01.jpg


The AD597 is a 5V logic chip http://www.analog.com/media/en/technica ... 96_597.pdf
A picture of the breakout from a supplier shows in fact it is an AD597
Extruder-Connection-Board-50405008A02.jpg


I'm trying to validate the analog pin compatibility of the processor with 5V signal scheme from an AD597 (because in fault mode, the AD597 outputs the same source voltage to indicate a fault). From what I can find, the data sheets are saying an FT labeled pin could take your processor base source voltage (3.3V) and then add +4V as the max. So in theory 0-5V is in that range of 0-7.3V.

Working theory is that if Raise 3D says is true, and there are pullup resistors, they might be connected to 3.3V source (since that would be nearby the processor since that is the processors main voltage) That would only pull up to 3.3V AKA 330C reported temp. Since they would be high value resistors, the net load could keep the resulting actual analog pin voltage lower and that might be the 240C or 2.4V. Either way, that means the resistors are not performing the function we need them to- throw a clear out of range temp report voltage- such that firmware can differentiate a now bad and disconnected state from a proper valid temp report- or that they just aren't there and we are talking crossed technical details.

Another situation that could be true, say the pin is only 3.3V allowed, so clamping diode circuitry to limit voltages higher than 3.3V is applied. That leakage could explain why a 3.3V pullup high value resistor like a 1meg could sag and only pull up to about 2.4V, or, say they did use a 5V pullup and again, for whatever reason clamping to prevent ADC damage limits the voltage but since the pullup is weak, instead of a clearly out of range signal above 300C, we instead get this 240C signal. 240C is well within expected and perfectly normal temperature range.

Either way, from where I sit, the lesson wasn't learned from the N series. The new mainboard is not detecting the cable break instantly, pullup resistors or not. Since the cable can break connection (this is just a reality we have to deal with) it's imperative that the hardware level can detect this state and give the firmware some way of detecting the fault. N series can now do it, the expectation is that a Pro2 would be even more robust. The Pro2 problem reports by actual users simply tells a different story.

This is why beta testing and outside independent testing is required to prevent things like this from hitting actual paying customers who are having problems that simply should not exist on a new improved version of the printer.

The point still stands, I cannot endorse or recommend this printer, based on technical knowledge and confirmed user problem reports. Until that changes, until proven by Raise 3D and an independent user or owner of the printer not associated with Raise 3D, I cannot agree this safety is to the level I demand.

Jetguy
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Re: Cold nozzles reading 240° C

Postby Jetguy » Tue Aug 28, 2018 4:07 pm

Ilia T wrote:Another thing we found might will give you glues to the issue source. We found that the extruder board is sensitive to temperature. The chamber of the printer is getting pretty hot and stepper motors near the board is getting hot too. So maybe this is the clue in the issue. Or maybe not.

Here is the video to demonstrate the board temperature sensitivity. We set both nozzles temperature to 220 C and blown warm air from heat gun at low temperature setting on the board. You can see how this affects on the temperature reading on the video.

https://www.dropbox.com/s/z18ei09e5cfxe ... e.mp4?dl=0

We also performed test with cold compressed air. Here is another video. You can see that this affects reading too.

https://www.dropbox.com/s/dg9kkk6wgsvju ... e.mp4?dl=0


Wiggling the wires on the board or manually moving the print head around do not affect temperature readings.


I might be able to explain this:
http://www.analog.com/media/en/technica ... 96_597.pdf
A thermocouple amp chip and a thermocouple actual temp sensor, there are some baseline things about them found in the data sheets.
#1 A thermocouple is a relatively simple device made of 2 very specific types of metal wires, welded together at the sensing end. The wires themselves generate a tiny voltage proportional (and right here is the key to all of this) to the difference in temp of the very wire at the sensing end junction (the 2 wires welded together) and the other end of the wire. In other words, it measures the difference in temperature at hot end side compared to the junction at the screw terminals of the breakout board. Since that breakout board is near the extruder head and heated by ambient temps inside the printer- not to mention the nearby extruder motors, again, you are measuring the difference in temps between the hotend and whatever temp the screw terminals are.
#2 The thermocouple amp chip was designed around this problem above and is self compensating. It has an internal laser trimmed and calibrated at the factory internal temp sensor of the chip itself. Again, these are designed at the factory and custom laser trimmed to be extremely accurate hence why sold as a chip they can claim plus or minus 4C accuracy between any 2 chips. The key here is, the data sheet also says the screw terminals must be very near the chip itself. Again, the idea being the chip knows it's own temp, and based on the proximity the screw terminals are assumed to be the same temp as the chip.
#3 which is how the chip takes a relative difference of hot end temp and the screw terminals, and turns that into a signal that is relative to room temp. Again, the thermocouple measures the difference between the hot end and the screw terminals on the breakout, then the actual thermocouple amp chip is factory calibrated to know it's actual temp, and from that it's adding that chip temp to the differential temp to get the actual hotend temp

When you blow hot or cold air near or around the thermocouple amp you can and likely are disturbing the steady state and also the assumption that the screw terminal junction is the exact same temp at the thermocouple amp chip itself. The screw terminals have mass and are covered in a plastic housing. The bare and very small thermal mass of the thermocouple amp IC can change temp faster due to hot or cold air blowing than the screw terminals would right beside them. Since you are offseting a known assumption (chip temp=screw terminal temp) this would then offset the temperature reported.

We are literally dealing with the pros and cons of using a thermocouple, and the issues associated with a long cable distance to the extruder head.
If they had used thermistors- then much of this problem in catching a fault would not exist, but then the tradeoff of thermistors are non-linear devices and accuracy between printers comes into play. Again, we could debate this pros and cons all day, but this one, because it's a resistor, open circuit break in the wires is obvious, shorting is obvious- the 2 fault conditions are very easy to detect.
VS
Using a thermocouple that given following the data sheet, can be as accurate as 4C between any 2 printers when following all the rules

But there are also 2 thermocouple options.
One is what we have, mount the amp at the extruder head, and this allows flexible normal copper wire to make the 1 meter or more connection back to the mainboard. The pro of this is that it's easy to build the printer, easy to change a thermocouple, easy to use nice easy copper wire back to the mainboard. The con is- potential for the exact problem- detection of a failed cable between the remote amp and mainboard.
OR
Run special extra long thermocouples that go all the way from the extruder head, through the cable chain, all the way over a meter to the mainboard and have the thermocouple amp there. The issue with this is, most thermocouple wire is not stranded (because it has to be very specific metals) cannot have any connectors or breaks in the middle with any other metal connectors, and would be not only expensive, but a pain to replace when they failed and fail they would- faster than any ribbon cable problem.

TheDude
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Re: Cold nozzles reading 240° C

Postby TheDude » Wed Aug 29, 2018 4:49 am

Hey all, is there a resolution to this issue from Raise3D? How can the rest of us new owners test and detect this issue? Where is the hardware/software fix?

Ilia T
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Re: Cold nozzles reading 240° C

Postby Ilia T » Wed Aug 29, 2018 4:30 pm

OK, tonight we printed 12 hours work with a bunch of parts all over the tray and had no issues. Hope the bracket has permanently fixed the issue.

KS_Husker
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Re: Cold nozzles reading 240° C

Postby KS_Husker » Wed Aug 29, 2018 7:11 pm

Wow Jetguy. You obviously know your stuff when it comes to electronics. I sure hope Raise takes note and listens to what you are saying. Safety is never something that should be compromised. I will hold off on any purchases until I am sure that this issue has been "Properly" addressed.

Thank you for your time you put into this board.

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Vicky@Raise3D
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Re: Cold nozzles reading 240° C

Postby Vicky@Raise3D » Thu Aug 30, 2018 4:52 am

We do have pull-up resistor designed originally on Pro2 series motion controller board, and set max limit of temperature as 330C.
During heating, once the cable gets disconnected, although there shows no error message, the heating will be stopped. We will add error message for this issue in next version of firmware.
q.jpg

Jetguy
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Re: Cold nozzles reading 240° C

Postby Jetguy » Thu Aug 30, 2018 8:57 am

Vicky, thanks for the try here, really sad that it comes to this, but explains a lot.
So it is some of what I described, it clamps up to 3.3V, but then also pulls to 5V????
It's 4Am, so forgive me here if I don't get the first analysis right, but it appears to clamp the the potentially 5V signal we can and will get from the AD597 output and that's not great for the AD597 output side. Again, we know per the data sheet, an AD597 will throw a 5V high signal when a thermcouple is open circuit. That is a fault that could easily happen- especially given folks are taking down their hotends to correct jams. Again, based on what I see here, the diodes clamp that from 5V to 3.3V and that's part of what you describe. But then , there is a 10K ohm resistor in series, and then a 1 meg pullup to 5V. That would attempt to pull the circuit up to 5V, but still be clamped by the diode. That all then goes into a buffer or ESD chip (still trying to find the specs), then into another 10 Ohm resistor, then to the analog processor pins.

The problems with this circuit:
The signal input range from the AD597 remote thermocouple out on the breakout is 0-5V, however, there are clamping diodes to 3.3V right in the middle of this circuit coupled to a 5V pullup on the inside of the circuit. Then a buffer or maybe that's an ESD protection array (again, still trying to get the details, it is 4AM) and then more resistors for the processor analog input pins. I'd say from the resistor values alone- it's not doing what you think and say it should do. In theory, since it is pulled to 5V, error condition is greater than the clamp voltage of 3.3v. It would be below a 4V max value if that was the max for those pins and likely is for other digital pins, but based on my understanding, there are 5V tolerant pins, not to mention, you are using a 5V signal based thermocouple amp. As such, the first thing I would test is remove the diodes clamping to 3.3V (D19 and D20). That then opens the circuit up to operating full 5V signal range. Alternatively, if you want some protection, break the 3.3V connection and connect the diodes to 5V source to clamp to the much more logical 5V range. My concern is those diodes interfere with a critical temp signal that you are getting from the AD597 and as little as 10mV interference is enough to begin offsetting the reported temp. It also clamps the 5V signal of an AD597 output, and say there are resistors in series, all I'm getting at is even more offsets, just flat out bad behavior. That output of the AD597 is less than happy if you clamp it to 3.3V. I'd call that a pretty serious flaw.

Here's what I think happened. I think somebody built the circuit, then said Oh crap, this 3.3V processor, we have to clamp to 3.3V max on ALL pins, and then added this clamping to this circuit, without testing the actual real world consequences. As such, it's not giving you the AD597 full output of the remote thermocouple amp of 5V and limited to range signal of 3.3V, but due to losses, the resistors, it's instead going to 2.4V AKA 240C and that's why you aren't throwing error messages and that's why might have a problem detecting a fault state.

Again, it's way early, I need to put this into a circuit, see what it does in a simulator, build the physical circuit based on the components you have listed, run some actual real world tests (because as much as I love sims- never trust them for something this critical with an analog voltage signal and something as little as a 10mV) and see what this does, but regardless, to see a known 5V signal range, clamped to 3.3V, still include 5V devices on either side of that, you guys have me scratching my head and anyone else probably should take a look here, but to me, that is a bad idea even if you consider it "working". I get the intent, protect the processor and expensive mainboard, but at the cost of what it does to a critical temperature signal and that signal is what decisions on heating are based on? Again, this is early morning first look at a circuit to find why users are having such trouble, why the printer is not going into an error mode on cable failure, why the N series now works the way it should and why Pro2 series isn't doing the same thing. Yes, some of it might be firmware, but this points at hardware, and the limitations here of a 3.3V clamp give you little room between your 300C advertised temp limit and a hard voltage reporting limit of only 30C higher. Again, we have a margin of only 30C here, to decide real condition or out of range condition. That's a pretty narrow margin. I also not 100% convinced, that if the intent was to clamp to exactly and I mean exactly 3.3V, the 5V pullup and resistors form a voltage divider making the actual voltage outside of clamping range. But I also don't know the losses in the circuit yet (that buffer or ESD IC) and those clamping diodes have a curve to them as well, and so there is an analog voltage when this is not connected to the external remote AD597 (the broken cable state) and I think that voltage is then not 3.3V. Higher or lower, but not 3.3V. And, this topic, of a 240C temp report definitely supports that theory.

If you've also learned nothing else, and I was going to post this last night, when you start lowering the time and deviation range on the safety code- you get caught in this false positives trap and just start making customers angry with false positive trips of the safety code and that stops them printing. They get mad, you force the hand and safety code is backed off or removed, and we are back where we started.

I'm trying to guide you to a safe and now proven on the N series, way of detecting a fault and not tightening the safety code range to the point that begins to cause issues. viewtopic.php?f=3&p=36373#p36373
Remember when on the N series, we had firmware 1.1.1 because in around 1.1.2 or whatever that release was, you began to turn on safety code and people kept getting hung on error messages, so you reverted back to 1.1.1 with no safety code at all?
Let's take the notes, learn from the past, and do this right.

Again, we got the N series to a point where I'm completely comfortable it works and is in fact safe (provided a user does install the safety board). Let's get the Pro2 series to the same state.

Jetguy
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Re: Cold nozzles reading 240° C

Postby Jetguy » Thu Aug 30, 2018 2:12 pm

I'm still shaking my head hours later. If the problem is the board must limit to 3.3V signal range, then a 3.3V thermocouple amp and thus resulting 3.3V signal range should have been implemented rather than using the 5V AD597. The AD8485 is just such an equivalent 3.3V unit and uses a smaller 5mV per degree signal scheme, to better fit in the 0-3.3 range being clamped in this mainboard design.

If the pin of the processor really is only 3.3V tolerant, again, to me, the system design and the use the 5V pullup and 5V AD597 is flawed.

If the pin is allowed 5V range (and according to what I'm reading in the data sheet, FT pins are the analog pins), then the diodes clamping to 3.3V are not required and should not be there in a signal chain.
According to what I can find, this is the note from the processor family data sheet.
Pro2 processor rating.jpg


Take it with a grain of salt, I don't have all the schematics, only a small section of the circuit.
Both what I see, and what Vicky said points to a 3.3V limit caused by diodes 19 and 20. That in turn would clip any signal and limit it to 3.3V even though the AD597 would attempt to output voltages up to 5V and especially in a fault condition of open thermocouple.
That in turn, coupled with the 300C advertised temp capability of the printer, means there is only 0.3V between maximum reported temp from a printing standpoint to maximum voltage ever allowed of 3.3V AKA 330C. That leave no headroom for overshoot that might naturally occur (say 5-7C overshoot when first heating from cold) and how much margin of safety can you really have to then say everything from 310C and higher to 330C is error condition and that's what the pullups do when then cable breaks.

Again, I can only go by user reports, this information, what research I can take from data sheets and my own knowledge and background, but to me, this just is not my expectation that this is a circuit I'm going to say is OK. It's just not.

Again, if we go by the problem reports:
the firmware is not going into a safety fault mode when these cables are breaking
the reported temp is not out of range enough, so I'm having a hard time seeing how firmware is going to differentiate if the pullup is not doing what is intended, and that is pull it out of range to the point that fault condition is obvious and unmistakable. Instead, we seem to have a failure of the combined circuit- largely caused by the clamping diodes, to potentially cause the fault signal to be in normal printing range 240C.
The circuit certainly has the potential to cause exactly what I'm seeing in the problem reports on real printers.
We are back at, I have issue with the circuit and while now shown that there are resistors in place- the rest of the components in the circuit may invalidate the values chosen of those resistors, and cause the function and result they are intended to produce to not trigger the safety condition as intended. Firmware is only as good as the data set it can make the decision on, and if the circuit itself is not producing the conditions and thus data we can differentiate a valid signal and a fault condition from- I fail to see how firmware can effectively solve a hardware (electronics) issue. If anything, the new info makes me even more against this problem, it's a failure here to put such a circuit that could affect the true reported temp of the thermocouple amp. To me, that's just crazy. To then further this, the rating and official sales page saying 300C as a capability, the temperature reporting headroom here is just too close for my personal comfort.

Nope, I'll take an N series mainboard set with a thermal protection board any day over this new Pro2 series. I know what an N series can and will do, I know the safety works as I intended and demand for all printers.

TheDude
Posts: 33
Joined: Tue Jul 17, 2018 2:45 am

Re: Cold nozzles reading 240° C

Postby TheDude » Thu Aug 30, 2018 6:17 pm

Vicky,

We really need some firm and final root cause, interim and permanent corrective actions ASAP please.

Please advise Raise’s timeline on this as many of us will otherwise have to move the path of Jetguy in that no response or slow response means no solutions coming.

I suspect that several of the “jams” being reported by us on other threads are fully or in part directly related to this issue, vs chasing cooling fans, etc that may make the problem worse.

If raise stands up and provides the above in full commitment to solve the problem, we’ll rally behind you, else we have to walk and advise others the same.

Thanks for your prompt attention in advance!


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