Temperature does not rise

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Roy93
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Temperature does not rise

Postby Roy93 » Fri May 26, 2017 12:47 pm

Hi.
I have a problem that the temperature does not rise to the setting after replacing the nozzle.
The temperature rise stops at the set temperature of -10 ° C when loading the filament.

When I replaced the nozzle, I truned the screws of the following photographs. Will this affect the temperature?
無題.jpg
無題.jpg (43.9 KiB) Viewed 2686 times


Also, is there any information on stagnation at the set temperature of -10 ° C?
Thank you.

Roy93
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Re: Temperature does not rise

Postby Roy93 » Fri May 26, 2017 3:25 pm

This problem occurs when loading and unloading filaments. It does not occur during printing of model objects.

Jetguy
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Re: Temperature does not rise

Postby Jetguy » Fri May 26, 2017 4:22 pm

First tip, stop using the load and unload filament menu item and hand insert or retract the filament. As an operator, you should have an understanding of how the loading a pressure should feel as the filament reaches the nozzle. You also should always feed at least 10mm of filament or more before unloading. This forces the melted filament out of the nozzle before you pull up on the filament and failure to do this means pulling that melted filament out through the filament path and is a source of pretty bad jams.

There is information on stagnation- specifically, PID loop is not active in firmware UNTIL 10C difference between target and actual temps. In other words, the firmware applies PID settings- also in firmware ONLY once in the 10 C range. So under 10C, that's 100% heater on rising. PID loop range would turn down the heater from full on based on PID values. P for proportional is the first value based again, on the difference between target temp and actual temp. So if you are stuck at 10C below the target, that means P value is not "strong enough" such that even at 10C away, the heater should be nearly 100% PWM on. As you get closer to 0C difference, PWM is dropping, again, a proportional value. I or integral value in PID is TIME based. The idea is, the longer you sit in the 10C PID is active difference, and you still haven't reached setpoint temp, then I is rising over time. This makes the heater add more PWM percentage on, to whatever value the proportional gain is. Finally, D value, derivative, is used to SLOW the rate of heating nearest the setppoint. The idea here is D is a combination of opposite proportional and time based like I. So it's seeing how fast the change in temp is over time from far away from the setpoint to nearer the setpoint. It subtracts PWM on time from the overall heater value.

Follow this scenario.
The heater is commanded to a setpoint from a cold start.
The heater is turned on by firmware because the sensed temp is greater than 10C less than the setpoint so heater is 100% on.
As the sensed temp is within 10C of the setpoint, PID values in firmware are used rather than bang bang ON/OFF. So Again, P takes the difference between set temp and actual temp and applies a proportional value to make the heater less on as it nears the setpoint. Example 100% on at 10C difference, 90% on at 9C, 80% 8C, and so forth all the way to off at setpoint. The issue is, if radiation, convection, and actual extrusion are always drawing heat from the system, 0% on means the heater block and nozzle would immediately cool. This is why you see a positive value in proportional, there is going to still be some percentage of on value, even when the heater is at target temp exactly. Otherwise, you'd get that ripple and unstable temp control around the setpoint. I value is what is actually getting you there to the setpoint. If you only had P and it wasn't perfectly tuned, you might NEVER reach setpoint. That's again, because as you get closer to setpoint, the heater is turning down on P value alone. I value says hey, let's get there already, we've been waiting a while and not reached setpoint. So again, it's dynamic because it's time based. The longer you are not at setpoint, the higher it wants to turn the heater on. However, if you ONLY had P and I, then the heater would be full blast on from I value saying "let's get there fast" and overshoot the setpoint resulting in way too high a resulting temp swing. So this is why it's PID, the D sees that rate near the setpoint and slows down both P and I value on heater on, and that way, you approach the setpoint nice and gradual, easing right to the actual setpoint.

So here lies the problem. Stock firmware does not have EEPROM enabled, and thus settings are hard coded into the firmware. PID as an example. So, the factory chose defaults based on the hardware they had at the time of firmware creation. Over time, different heaters, different details on the heater blocks, thermal barrier tubes, and as always, individual printer construction have small but different effects on the rate of heating, the thermal conduction loop from the heater back through the block to the thermocouple as the temp sensor. Depending on YOUR specific details, you can make changes that slow the rate of conduction between the heater and block or the heater block and thermocouple, or even the airflow from the fan. That can lead to a condition where the default PID values are NOT well tuned for your system. That is when you would see the P value allow sag, and then depend on the I value to see it sit there not rising in temp and kick in a little boost and finally reach set temp. That's the good thing about PID- even a badly tuned system, the values should eventually wind up enough to get the temp. However, on a really badly tuned system, yes, even PID function cannot solve everything,

So all that said, if you messed with the hotend, Ensure the heater and thermocouple are well seated in the heater block, making GOOD mechanical and thermal contact, ensure the setscrews are snug ***Caution, do NOT overtighten and crush or deform the tube heater and tube thermocouple as this makes them impossible to remove later and/or strip out the setscrews) Snug, not insanely tight. The goal is good thermal contact. In addition, insulating the heater block with ceramic and kapton tape is the preferred method and solves a couple of other thermal issues too.

Roy93
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Re: Temperature does not rise

Postby Roy93 » Fri May 26, 2017 5:45 pm

Hi Jetguy.
I appreciate your advice.
Do you know the role of the golden screw at the position of the arrow in the photo?
It does not seem to be related to thermal sensors and so on.

Jetguy
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Re: Temperature does not rise

Postby Jetguy » Fri May 26, 2017 6:08 pm

It is simply used to tension against the threaded thermal barrier. Do not tighten it IMO as it damages the threads and serves no purpose.
It anything I wish it was not part of the design. The seal is the thermal barrier screwing down into the block from the top and the nozzle screwing up into it from the bottom. I know why they think they put it there, but again, does more harm than good and is a part users like yourself do not even understand how or what it could do, and the cause of much frustration.

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walshlg
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Re: Temperature does not rise

Postby walshlg » Fri May 26, 2017 6:11 pm

Roy93, not sure if I am seeing this right but it looks like your isolation tube might be out too far (this is NOT likely the problem with tenperatures), the arrow is right in the way to see but make sure that the shoulder of the isolation tube is about 1mm higher than the top of your hot block. If not in far enough then the nozzle cant seal against it and your get a terrible mess of leakage out the top!

Jetguy
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Re: Temperature does not rise

Postby Jetguy » Fri May 26, 2017 6:41 pm

Again, they call it the throat tube, other companies and in general tutorials, it called the thermal barrier tube. Why? Because it's job in life is to connect the hot plastic melting heater block, heater cartridge rod, thermocouple, and the nozzle (AKA the Hot End) to the central crossing block and feeder system above (AKA the cold end). Again, the job is to connect the plastic melting smoking hot parts, to the rest of the machine that must stay cold. The thermal barrier is made either from stainless steel or in the case of this brand, titanium because those 2 metals are poor conductors of heat. That way, they still connect mechanically, but slow the rate of heat conducted upwards. That said, slowing the heat is not stopping the heat. As such, the heatsink and fan is required to transfer any heat that does conduct across to the air, rather than rising and heating up the cold end and feeder section. This is the same reason you can have a stainless pot on a stove, and it has a stainless handle, and even though it's all metal, all touching, you can pick up a stainless pot with stainless handle without protection and the handle is barely warm. The total surface area of the handle and the poor rate of conduction means it does not reach the same temp as the actual pot.

Back to the extruder, the thermal barrier tube or throat tube is simply threaded with an M4 thread into the heater block. The nozzle is an M6 thread and screws into the heater block from the bottom. This means, the central bore in the aluminum block is 4mm threaded on the top and 6mm thread on the bottom. The 2 parts are screwed in so they mate in the middle and tighten against each other forming a seal. It may not be obvious, but with 1.7mm filament being less than 1 inch in cross section surface area, just a few pounds of force from the feeder pushing down creates well over 1K PSI (because again, the area is less than one square inch and we have more than one pound of pressure pushing down, and so that 1K PSI will try to find any leak it can between the throat tube and the nozzle. This is why assembly of the hotend is so critical.
Throat_Tube_V2_1024x1024.jpg


So here lies the problem with that brass screw you mentioned. The aluminum heater block is a relatively soft metal. That combined with the rather small surface area of the M4 thread on the end of the thermal barrier tube, the fact the heater block is a stepped bore with half being M6 and half being the smaller m4, and then now we have this brass setscrew and matching threaded bore mating from the side into the M4 threaded bore vertically. This means that from the side, at least a portion of the aluminum threads in the M4 bore are not even there when these 2 bores meet at right angle. Add to that heat and pressure, and the forces of the filament trying to push the entire hotend off the thermal barrier AKA through tube, and then even more, the nozzle tip banging and dragging away left and right through print material and occasional knocks and hits- that M4 joint and threads in the heater block can be a weak point. I recently had to replace the ENTIRE hotend on both extruders at the local Makerspace on the N2 there because users had changed the nozzles a few times, tightened it down, or failed to make good seals (so both loose and tight assembly errors) and over time, this ripped the threads right out of both heater blocks. Add to that, the brass setscrew slowly destroyed the threads of the expensive thermal barrier tube and bam- now out $160 for two destroyed hotends.

I'm just saying, as a new user, really understanding the parts, the relationships, the proper assembly methods, what is impotant, what is not important, it's a lot to learn and there are TONS of stories here of users damaging multiple hotends and at $80 each, it's no laughing matter. However, same users then complain why it cannot be made stronger, they simply do not understand the thermal and mechanical aspects of this- you cannot willy nilly change the design. Things must be a certain way for a reason. So the point is, be careful, follow the guides, and whatever you do, don't crank or manhandle this setup- because it will cost you money. Do it wrong, it causes a leak, users panic, that leads to frustration and more error, then parts are damaged. Too tight, it fails, causes a leak, and the cycle repeats. There is a narrow range of "the right way and the right way only" that you get this without leaks and without damage.
https://www.raise3d.com/pages/instructi ... assembling

Roy93
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Re: Temperature does not rise

Postby Roy93 » Sat May 27, 2017 6:56 am

Hi walshlg,Jetguy
I appreciate the detailed explanation. Probably, I think that trouble has occurred by turning the brass screw. However, there is nothing wrong with the printing of model objects. Only when loading and unloading the filament occurs the phenomenon of -10 ° C. Also, once the model has been printed, the filament loading and unloading will also normally reach the target temperature. It is very strange ...
I would like to see the situation in this state for a while.
Thank you very much.

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JohnSays
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Re: Temperature does not rise

Postby JohnSays » Fri Jul 07, 2017 3:11 pm

Just found this thread and I have my two cents to back up what JetGuy says about the brass set screw. DO NOT TIGHTEN IT. Just barely snug it to keep it from falling out. I actually don't know if it can just be left out. That would be my preference. I have destroyed two heat blocks by trying to salvage the stripped allen head. I have two more heat blocks with the stripped allen heads and have not yet attempted a repair them.

When the hot ends arrive from R3D, the brass set screws are way too tight and getting them out is not even a possibility because the brass is too soft once they get stuck in there with thermal expansion and contraction. I have been able to get the hot end apart and clean up the threads with a tap. I need a die for the thermal barrier tube threads. That can get damaged when drilling out the brass screw. I was having trouble unscrewing the thermal barrier tube. I heated it with a torch and it loosened right up. The tightness was due to unmelted plastic.
Last edited by JohnSays on Sat Jul 08, 2017 1:33 am, edited 1 time in total.
- John

2 Raise3D N2 Duals, Bondtech BMGs, adjustable table, Panucatt SD2224 drivers, run-out sensor, thermal overload protection, Firmware 1.1.9ABH - with Lin_Advance, Palette 2 Pro, Custom E3D hot end and ultra-light carriage and printer head

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Gwen
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Re: Temperature does not rise

Postby Gwen » Fri Jul 07, 2017 7:49 pm

My 2 screws are also dead because they are too tight and too fragile. A simple press on the key alen and you round the impression. So, I have a head that is blocked in rotation. I think I will have to drill and tapping to the top diameter because I do not want to buy a hot end at 120 €.

The list of hangings is dying on my N2.

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JohnSays
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Re: Temperature does not rise

Postby JohnSays » Sat Jul 08, 2017 1:34 am

Just be careful when you drill out the brass screw. You can damage the threads on the thermal barrier tube. I nicked mine this time, but I was able to clean them up with a jewelers file. Not hurting the threads in the first place would be better <g>.
- John

2 Raise3D N2 Duals, Bondtech BMGs, adjustable table, Panucatt SD2224 drivers, run-out sensor, thermal overload protection, Firmware 1.1.9ABH - with Lin_Advance, Palette 2 Pro, Custom E3D hot end and ultra-light carriage and printer head

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walshlg
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Re: Temperature does not rise

Postby walshlg » Mon Jul 10, 2017 3:03 pm

BTW, the allen wrenches we received are soft and they might have rounded, try another one before drilling

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JohnSays
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Re: Temperature does not rise

Postby JohnSays » Mon Jul 10, 2017 5:01 pm

Yes indeed, but I am using some nice German WiHa wrenches. The allen wrenches that came with my 2nd N2 this last Feb are of much higher quality than the ones I got a year before that. So the new wrenches are okay.
- John

2 Raise3D N2 Duals, Bondtech BMGs, adjustable table, Panucatt SD2224 drivers, run-out sensor, thermal overload protection, Firmware 1.1.9ABH - with Lin_Advance, Palette 2 Pro, Custom E3D hot end and ultra-light carriage and printer head

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Gwen
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Re: Temperature does not rise

Postby Gwen » Tue Jul 11, 2017 3:18 pm

Ah ah, JohnSays ! You mean that everything is changing over time on a Raise3D printer. Personally I do not have time to laugh, I prefer to send everything back as my boss asked me. In addition he puts me a glue, where can I find the European standard certificate !? Can someone help me...

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JohnSays
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Re: Temperature does not rise

Postby JohnSays » Wed Jul 12, 2017 2:15 am

Yes, many things are changing over time with the N2. Like any complex set of systems, the first is not as good as the last IF the company providing the equipment continues to strive to make a better product. 3D printers are complex and many lessons need to be learned. Companies like MakerBot aren't even doing as good as Raise3D. Perhaps Ultimaker is, but even those users are replacing their extruders. Maybe Type A.. no, no enclosed build area. Prusa? No, too small and not enclosed. Sigh.. Who has the perfect machine without flaws?
- John

2 Raise3D N2 Duals, Bondtech BMGs, adjustable table, Panucatt SD2224 drivers, run-out sensor, thermal overload protection, Firmware 1.1.9ABH - with Lin_Advance, Palette 2 Pro, Custom E3D hot end and ultra-light carriage and printer head

dmtulsa
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Re: Temperature does not rise

Postby dmtulsa » Mon Jan 14, 2019 11:56 pm

I know this is an old thread but someone doing a search may find it and the thread has some good info and advice.

How I solved some of the these issues. I make my own heat blocks using 5/8 x 5/8 alum stock then mill it to size. I also use bigger 5/32 Stainless steel set screws to hold the heater and thermocouple snugly. I get rid of the barrier tube R3D uses in favor of more generic types. To do this I boar a 7mm hole in the heat block then machine a mild steel rod a few thousandth's bigger OD and drill the ID for a 6mm tap. Press it into the aluminum block. This way the nozzle and throat tube align correctly even after many nozzle changes . After a few nozzle / throat tube changes the factory threads in the aluminum block ware, cause misalignment and other issues. I haven't had a jam since in that area. I also make the top piece that goes up into the extruder housing and generic Stainless Steel throat tubes screw into it, Heat sink in between of course.
It really makes a robust system. I'm sure there are better ways but this is cheap and works
As far as the PID goes I just send the m303 and then put the kp ki kd values in the firmware. I too had many problems of it not getting to temp in the past.
Doug.

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JohnSays
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Re: Temperature does not rise

Postby JohnSays » Tue Jan 15, 2019 1:46 pm

Please post detailed pictures. I would like to see what you are writing about.
- John

2 Raise3D N2 Duals, Bondtech BMGs, adjustable table, Panucatt SD2224 drivers, run-out sensor, thermal overload protection, Firmware 1.1.9ABH - with Lin_Advance, Palette 2 Pro, Custom E3D hot end and ultra-light carriage and printer head


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