Nozzle temp 5 degrees low

[Penged]

Hello all,
I have my stock ROSTCK V2 running smoothly and all of a sudden my nozzle temp stalls out about 5 degrees below the target temp and will not go above 190. I attempted to run the auto tune (changing to target temp to 190 instead of 200) with no luck. Thanks in advance.

[Windshadow]

Suspect that one of the heating resisters has failed.... consider replacing them with a can heater

[Polygonhell]

Either the resistor has failed or you just don't have good PID values in the EEPROM.
Ensure PID Drive Max is set to 255 in the EEPROM.
If when you set the temperature to say 210, does it go over 190?
If it does, the issue is just the PID values, auto tune uses the existing values as a starting point, it's quite possible to tune these the hotend will not reach temperature. Manually reduce I and D and try again.
If with the heater set to 210 it still doesn't go past 190 and the PID DRIVE MAX is set to 255' then you likely have a bad resistor, you can verify by reading the resistance with the wires disconnected from the board, it should be about 3 ohms if both resistors are good.

[Penged]

As I thought about it I remembered it started acting up after a power failure. Between that and it's inability to go past 190 makes me think its a bad resistor ( possibly blown when the lights came back on). I'm going to use this as an excuse to upgrade as suggested by Geneb in this post.

http://forum.seemecnc.com/viewtopic.php ... 5&start=25

[Windshadow]

Penned,
Geneb has a step by step you tube video for this upgrade of the stock hot end
https://youtu.be/xvXKt3xDt4E
I used the eBay links he provided in the read me for the file and the parts arrived quickly

[Penged]

Oh cool, thanks Windshadow

[Penged]

As a follow up, I had a bad resistor. In the process of doing to Geneb upgrade. Is it still recommended to wrap the ceramic heater in foil or would I be better off with high temp RTV? Wish me luck.

[Windshadow]

I drilled and tapped for a set screw to hold the can tightly to the side of its hole

[Penged]

Your a brave man, I done see much real estate to drill and tap a hole with. I was also thinking about using duct tape( the metal kind). Did you fill in the hole on the opposite side with anything? I was thinking it might be a good idea to help keep the temp more stable.

[Xenocrates]

I drilled and tapped it from above. Seems solid enough. Using a standard M3 tap, it does OK. a finer tap, say a wee little 3-56 UNF would do even better, although that means it's not E3D compatible.

[Windshadow]

just as Xeno said from the top with a M3 as i had it to hand from doing the thermistor
and i had an M3 set screw handy (though you could use an M3 standoff as was used for the potted thermistor and cut some of the top off to make a thin hex head...)

I have boxes of assorted fasteners some even sorted into labeled bins

Whenever something like a fax machine or a inkjet printer dies i take them apart.... partly for the parts but mostly to see how they were put together.... i have been taking stuff apart since i was about 5 years old and got some real tools... mostly they work after i put them together too

though as Xeno said from the side with a slightly finer thread like 3-56 i am sure would be OK
If you wanted to you could coat the heater can with some arctic silver thermal paste as used on heat sinks if i have to change it I expect i will as i found a tube of in when i was looking for something else in my box of dismantled old PCs stuff.

[Penged]

I have also been dismantling machines from an early age. I also have a printer i scavenged waiting to be dissected.
I also thought about thermal paste.
What are your thoughts on making your own threaded themristor using JB weld and a standoff. I wonder if the JB weld is sufficient to give accurate readings.
I appreciate all the input from the forum. There is not a chance I would have been able to get this far on my own.

[Eaglezsoar]

I have also been dismantling machines from an early age. I also have a printer i scavenged waiting to be dissected.
I also thought about thermal paste.
What are your thoughts on making your own threaded themristor using JB weld and a standoff. I wonder if the JB weld is sufficient to give accurate readings.
I appreciate all the input from the forum. There is not a chance I would have been able to get this far on my own.

You can make your own threaded thermistor using the JB Weld and a 3mm threaded standoff but the temperature cannot go above approximately 280 Degrees Centigrade because
of the epoxy. It would work fine in the original hot end because it cannot approach those kinds of temperature anyway. If you make your own threaded thermistors make sure
that the bottom glass of the thermistor is touching the standoff before applying epoxy for maximum heat transfer to the thermistor.
If you place a ceramic cartridge in the default hot end you will indeed have an empty hole and you need not put anything into that hole.
I use mine to heat my salami.

[Penged]

Ok well I replaced the thermistor and the resistors, flashed the firmware and now my nozzle temp reads 1024. where did I go wrong?

[Polygonhell]

You probably have a thermistor lead shorted against something, probably the heater wire.
Unplug it from the board, and measure the resistance it should be about 100KOhms if it's not shorted to anything.

[Penged]

I have a broken wire in my thermistor.

[Penged]

It could be the configuration changes you just made, but assuming those are correct, you either have an open circuit or a short in the thermistor wiring.
Disconnect it from the board and measure the resistance with a meter, it should read ~100KOHms at room temperature.
If you think it's the firmware changes you can pretty much pick any of the 100K thermistors preconfigured in the firmware and they should read without 20 degrees of accurate, if they still read def, it's the wiring.

fixed and checked the thermistor wire and Im good to go there. How do I pick a thermistor?

[Polygonhell]

If it's working with the changes you've made (from the other thread), I'd just go with it.
You do want to take it up to about 200C and then check what the actual temperature is.
If the table is good it should be close.
If it's "miles" off you either live with it knowing the difference, or you have to tweak it in the firmware to make it accurate.

[Penged]

Its still stuck on the nozzle temp being 1024. Do you think I should change the firmware back to the original and work from there?

[Polygonhell]

It's probably easier to debug if you go back to known working firmware, it'll likely only be ~20C off.
But unless the table your using is totally borked or you somehow messed up the thermistor pins in the firmware the odds are you still have a wiring issue or (less likely a bad analog pin on the RAMBO).
Does the fixed thermistor wiring have it reading 100KOhms at room temperature?
You can also test the firmware/RAMBO side to see if it's working by wiring a 100KOhm resistor across the thermistor pins, and seeing if you get something reasonable from the display.

[Penged]

The thermistor reads 115 from the plug at the board. I am completely mystified by the software side of all this so I was leaning on Xenocrates to help me with the firmware changes. That being said I am not 100% confident I did as instructed. Silly question, the thermistor has no polarity correct?

[Penged]

I figured it out. I think i forgot to change what table I was using in the CONFIGURATION.h file. Running the PID autotune now. Thank you for the help