Hotend not getting past 160c without extruder fan being blocked off

[n108bg]

I'm having a frairly worrysome issue with my rostock max v2. At the moment, i cannot get the hotend past 160 degrees without having a nice piece or two of kapton tape nearly completely blocking off the extruder, at which point, it will heat up to about 1 degree below temperature and stay there. I'm not exactly sure what the issue is. Any suggestions?

[nebbian]

Is there a PWM Max duty cycle config variable set? In some firmware (Marlin especially) this can be set to 128 instead of 255. This is designed so that you can safely use high powered heaters. In your case, you might have a 20W heater, and so you need to set it to 255.

I'm just guessing though.

[n108bg]

max duty is set to 255. I also tried changing the fuse, now gets up to about 187, and about 207 with the fan at half speed. i feel as though there might be something wrong with the wiring or the resistors for the extruder

[Nylocke]

One of the resistors may have burned out. Both in parallel should measure 3.4 ohms.

[n108bg]

One of the resistors may have burned out. Both in parallel should measure 3.4 ohms.

I'm getting 9.4 ohms when i touch the two sides of the resistor package. Do i need to unplug the wiring from the board when i measure, or am i actually getting 9.4 ohms?

[Eaglezsoar]

It almost sounds as though the resistors are wired in series. Has this printer worked before?

[n108bg]

yeah, its run about 3 kilometers of filament now, primarily ABS. I turned it off a couple days ago after leaving it on for a while (board only, hotend and HBP shut off automatically), came back to it today, and it was doing this. Both resistors are running in parallel, i promise.

[Eaglezsoar]

yeah, its run about 3 kilometers of filament now, primarily ABS. I turned it off a couple days ago after leaving it on for a while (board only, hotend and HBP shut off automatically), came back to it today, and it was doing this. Both resistors are running in parallel, i promise.

Hopefully you have a connector that you can take apart to disconnect the hotend from the rambo. If so disconnect all power to the printer and disconnect the hotend then measure the resistors.
You should not be reading 9 ohms or greater. I personally would replace the resistors with one of the ceramic heaters that you can find on Ebay and other sites. (12 Volt heater)
This would eliminate the resistors and all the "goop" that is holding them in. You will have one hole free on the hotend after you switch to a heater. Do not use 2 of them!
Anytime you work on the printer, disconnect all power! If you pull a stepping motor wire off the Rambo when powered you will most likely blow the driver circuit for that stepper.
Best of luck with the printer and keep in contact so that we may know the status.

[Nylocke]

The power resistors are quite fragile, and if you are not very careful when assembling the hotend (IE if there is a small pocket of air next to one of them) they can build up too much heat and rupture. The cartridges are so much more robust, and I'm sort of disappointed that SeeMe still hasn't designed and shipped a different hotend design for use with them (I know the ERIS has a new design thats experimental, but its not yet available).

[n108bg]

I don't work on the printer with the power on/connected when i work on the printer since i blew the heater fuse. I removed the wiring from the board and verified, 9.8 ohms. I have a 12v heater cartridge lying around from an e3d hotend i have sitting in a soon to be replaced rigidbot. i might give that a shot, if it fits.

And what do you mean i can't put 2 of them in? 80w would sure cut down on the preheat time

[Eaglezsoar]

I don't work on the printer with the power on/connected when i work on the printer since i blew the heater fuse. I removed the wiring from the board and verified, 9.8 ohms. I have a 12v heater cartridge lying around from an e3d hotend i have sitting in a soon to be replaced rigidbot. i might give that a shot, if it fits.

And what do you mean i can't put 2 of them in? 80w would sure cut down on the preheat time

Ha Ha. It's your printer and house if you want to burn them down. (just kidding but do not use 2 of them, use the empty hole to warm up small slim jims.)

[n108bg]

The power resistors are quite fragile, and if you are not very careful when assembling the hotend (IE if there is a small pocket of air next to one of them) they can build up too much heat and rupture. The cartridges are so much more robust, and I'm sort of disappointed that SeeMe still hasn't designed and shipped a different hotend design for use with them (I know the ERIS has a new design thats experimental, but its not yet available).

Wasn't aware that the resistors were that fragile...i'll have to give that cartridge thing a try, maybe switch to an e3d hotend in the future.

As for the hotend, i mean, i've seen worse choices. Like the ultimaker 2 using 3 mil filament, because we need to be unique and use a form of filament that puts more pressure on everything from the cold end to the hotend, meaning our cold end will rip a trench into the filament at random, and jam. Honestly, up til' now, aside from managing to blow a fuse on the board, this extruder was fine.but i know i'm going to start using PETG filament soon, and that's edging up real close to that magical 247c mark where the PEEK turns to mush.

Ha Ha. It's your printer and house if you want to burn them down. (just kidding but do not use 2 of them, use the empty hole to warm up small slim jims.)

i'll figure out something to put in there. As for the new cartridge, I know i will have to recalibrate the extruder PIDs, are there any additional precautions i will need to take if i intend to run PETG or other hot plastics?

[Nylocke]

Lots of hotend and printer manufacturers use 3mm filament (Ultimaker, Lulzbot). The problem you describe isn't unique to 3mm filament, and it likely jammed before it dug the whole. Its likely due to a problem that occurred with the hotend.

If you mean Nylon and the like when you say "hot plastics" I wouldn't try it. PETG should be okay but anything over 247C will cause the hotend to fail, you aren't replacing the weak link (PEEK bits of the hotend).

[geneb]

Nylocke, the reason they're using resistors is this:

If the thermistor fails and the firmware pumps more power to the hot end in an attempt to raise the temperature to the set point, the resistors will eventually burn out and you'll have to replace one or more of them.

If that happens with a heater cartridge, it has a non-zero chance of burning your house down. (A 12v, 40W heater cartridge can melt aluminum.)

g.

[Jimustanguitar]

I just swapped out some burned up resistors for a friend. Same symptoms, one day the machine just wouldn't heat up as fast and couldn't quite reach its target temperature. It looked to me like there was an airgap in the silicone that allowed the resistors to heat up without transferring the heat into the aluminum of the hotend very well, and they cooked themselves that way.

[img]http://i.imgur.com/J1arxQq.jpg[/img]

[Nylocke]

I think if they had a better mounting solution for the thermistor this would be a non issue (also most modern firmwares have thermal runaway protection which should stop this from happening in 99% of the failures, repetier has panicked at me just because a heated bed couldnt keep temp or my hotend overshot by 10 degrees).

[geneb]

The mounting solution is perfectly adequate when the hot end is properly assembled. The problem with creating fool proof solutions is that the universe keeps cranking out more and more ingenious fools.

g.

[n108bg]

I just swapped out some burned up resistors for a friend. Same symptoms, one day the machine just wouldn't heat up as fast and couldn't quite reach its target temperature. It looked to me like there was an airgap in the silicone that allowed the resistors to heat up without transferring the heat into the aluminum of the hotend very well, and they cooked themselves that way.

[img]http://i.imgur.com/J1arxQq.jpg[/img]

I just pulled the resistors on mine, and they look exactly like that . hooked them both to the multimeter, and they were dead as a doornail. Wound up using some heatsink epoxy and gluing that 40w ceramic heater to it. Heats up to 152, then overshoots to about 160, then cools down. just need to tune the pid, and i'll be back in business! Thanks to all the jeddi's (isn't it spelled Jedi? or is that like a copyright thing/inside joke) who helped out.

[barry99705]

The plural of Jedi is Jedi. I'd wrap some high heat silicone around your hot end to hold the heater cartridge in place. I trust thermal epoxy to hold something about as far as I can throw my car. This happened when a cartridge fell out of the hot end.

[n108bg]

oh...christ. Yeah, i'll tack some of that red RTV around the ends once my current print stops. Was kind of thinking of that when i saw the epoxy was rated for in excess of 150c, but didn't think of how far in excess.

[Nylocke]

I prefer the mechanical connection of a screw or clamping mechanism.

Don't get too worked up, the Zortax has a proprietary firmware without a lot of the safety features implemented in newer versions of Repetier and Marlin. If that machine were running Repetier I have 99.9% certainty that what happened would have been prevented via either thermal runaway protection (gets too hot) or the temp dropping too much (caused by the cartridge decoupling from the heater block, which would have had a significant drop in temperature in 99.9% of situations, which after 10 seconds it would have been shut off).

I've dealt with both of these in my use of a couple different printers, thankfully not during an actual meltdown (one was an overheating PSU trying to keep up with the load of the bed, causing it to stay 3 degrees short for a prolonged period of time without rising, and the other was my own printer overshooting the temp set point by 10 degrees because of some bad PID values). While these features are not 100% reliable, I trust them to prevent accidents on properly assembled and cared for equipment. Software can lockup, and components can fail (and they seem to fail ON), so don't trust them with your life/expensive things, but at the same time don't worry too much when you leave the room for some coffee and leave the thing on.

[Jimustanguitar]

While we're on the topic... Red RTV has a really low flashpoint in its liquid state, so don't try using the heat of the hotend to cure it faster unless you're using really tame temps. The MSDS says it flashes above 93C!

And before anybody asks... No, I did not have an incident
I was just reading the MSDS to dig into the cure time.

[ken cummings]

Sounds like I have the same problem or very close to it. A couple of days ago I followed MatterControl instructions to reset the Touch sustem after layers wouldn't create. My Orion printed a couple of small test pieces then dropped from 210 C to 152. End of print. I am not skilled at repairing circuits. Is this something I can send back to SeeMeCNC for repair or replacement? I had a Bukito before this and such problems were easily dealt with. I'll send a message to SeeMe TEch support.

[ken cummings]

I reread the words of Jimustanguitar again carefully and see my problem may be just another software failure I am scheduled to demo the Orion next Wednesday so I'll pursue both hardware and software solutions.