can't get hot

[smiley]

Hey all,

Been lurking for a while now but I have a question. I'm trying to run the PID autotune for my stock hot end and it is really struggling to get the temperature over 180c. This was not a problem last week, when I was able to autotune and average out my PIDs, but I'm doing it again because I just installed a new 25mm PEEK fan.

I'm wondering if others have had (and solved) this problem. Is my fan too strong? Did I kill one of the resistors? Something else I'm not thinking of?

[smiley]

duh. Of course it's the fan. I know this because when I unplug the fan, it gets hot.

So, what are people doing to keep the PEEK fan from overcooling the hot end? Ducts? Tape?

[geneb]

Where do you have the PEEK fan installed? I can get it hot enough to destroy the PEEK section even with the fan running. That's using the stock resistors too.

g.

[smiley]

fan is just wedged into the space between the stock risers and the stock hot-end-mount. I wrapped it with a bit of tape to make a tight fit. It's about 1/2" away from the PEEK.

note, "stock" in this sense means "what they were shipping as of ~April 2013."

The fan was ordered, but never installed, by my partner in crime. It's a 5v job instead of the 12v one that I think the seemecnc guys are shipping now, but otherwise the same dimensions. I have it powered off the aux-out bare pads at the upper-left corner of the RAMBo, just below the heater pins for EXT1. I did it this way because it was what I had on hand, I would have to order (and wait for) a 12v fan.

So, either (1) the current to the fan is robbing enough current that the resistors won't heat up to a setpoint above 180 or (2) the fan blows too hard. I admit I just thought of (1) right now and haven't checked the schematics to see if that even makes sense (my gut sense says no).

When I get back to my shop again I'll try to set it to 200, with the fan running, but just hanging somewhere instead of mounted and blowing on the PEEK.

[cope413]

have you retuned the PID since adding the fan? If not, then that's the issue... your values will all change significantly after adding the fan...

[smiley]

was trying to re-tune the PID with the fan, and the routine kept failing because it won't get hotter than ~180 C. That's why I posted a question.

And it's definitely the airflow, not current draw- if I leave the fan plugged in, but pull it out of its mount space and point it elsewhere, the hot end heats up just fine. So I need to either dial the fan down a bit or stick a baffle or something in there to keep it from blowing so much on the aluminum resistor block.

[cope413]

What fan are you using? I literally built another Max last night with a friend, put the PEEK fan on, fired it up, and tuned it at 220. Heated up quickly, and we were in his garage that was around 50F...

You sure your thermistor is correctly seated?

[smiley]

thermistor is fine. External thermocouple readings are within 2c at all temps.

I wrapped the whole bottom aluminum block in self-adhesive silicone tape, 2+ layers thick. Stopped at the PEEK boundary. re-installed the fan, fired that sh!t up again. M303 S200 hits 200 degrees and then cuts power, asymptotic decay to room temp, message "PID Autotune failed! timeout"

What is the low-boundary temp where the autotune is supposed to bounce back to the setpoint?

[cope413]

Ok so you insulated the heater block. Where did you seat the thermocouple?

And to be clear, prior to insulation, you couldn't get temp to 180C, but with insulation you can get to 200, but now get a failure from timeout?

[smiley]

To be clear, exactly. Post insulation wrap, and with the fan on, now I get to the setpoint temp but afer the heater cuts out it fails to cycle around the setpoint and then the atotune times out.

Thermocouple is wedged into the angle between the hex head of the brass nozzle and the aluminum block.

[foshon]

Try lowering the set point for the autotune, if it runs use those settings and try for the higher set point again. I would also check the PID_Max value to make sure you are allowing the resistor to run at full current.

[smiley]

i just tried to run autotune at 180. it hit setpoint, cooled off to about 170, and veeeeeeerrrrryyyyy slooooooowwwwwlllly started ramping back up towards 180 until the routine timed out again.

going to work now, no more time to play with it until tonight.

apologies for the code-barf below, don't want to leave something out by accident because i don't know it's important. I think the relevant firmware lines are those beginning Extr.1, yes?

also, both the bed heat manager and ext1 heat manager are listed as value "1". Is that a problem?

just the extr.1 bit:

08:25:42.753 : EPR:0 216 1 Extr.1 heat manager [0-1]
08:25:42.763 : EPR:0 217 190 Extr.1 PID drive max
08:25:42.773 : EPR:0 245 60 Extr.1 PID drive min
08:25:42.783 : EPR:3 218 35.01 Extr.1 PID P-gain
08:25:42.783 : EPR:3 222 1.74 Extr.1 PID I-gain
08:25:42.793 : EPR:3 226 175.75 Extr.1 PID D-gain
08:25:42.803 : EPR:0 230 255 Extr.1 PID max value [0-255]
08:25:42.813 : EPR:2 231 0 Extr.1 X-offset [steps]
08:25:42.813 : EPR:2 235 0 Extr.1 Y-offset [steps]
08:25:42.823 : EPR:1 239 1 Extr.1 temp. stabilize time
08:25:42.833 : EPR:1 250 150 Extr.1 temp. for retraction when heating [C]
08:25:42.843 : EPR:1 252 0 Extr.1 distance to retract when heating [mm]
08:25:42.843 : EPR:0 254 255 Extr.1 extruder cooler speed [0-255]
08:25:42.853 : EPR:3 246 0.00 Extr.1 advance L [0=off]:


complete eeprom dump below:

08:25:42.442 : EPR:2 75 250000 Baudrate
08:25:42.462 : EPR:3 129 3.50 Filament printed [m]
08:25:42.472 : EPR:2 125 5458 Printer active
08:25:42.492 : EPR:2 79 0 Max. inactive time [ms,0=off]
08:25:42.502 : EPR:2 83 120000 Stop stepper after inactivity [ms,0=off]
08:25:42.522 : EPR:3 3 80.06 X-axis steps per mm
08:25:42.532 : EPR:3 7 80.06 Y-axis steps per mm
08:25:42.542 : EPR:3 11 80.06 Z-axis steps per mm
08:25:42.562 : EPR:3 15 60.00 X-axis max. feedrate [mm/s]
08:25:42.572 : EPR:3 19 60.00 Y-axis max. feedrate [mm/s]
08:25:42.582 : EPR:3 23 60.00 Z-axis max. feedrate [mm/s]
08:25:42.592 : EPR:3 27 100.00 X-axis homing feedrate [mm/s]
08:25:42.602 : EPR:3 31 100.00 Y-axis homing feedrate [mm/s]
08:25:42.612 : EPR:3 35 100.00 Z-axis homing feedrate [mm/s]
08:25:42.612 : EPR:3 39 12.00 Max. jerk [mm/s]
08:25:42.622 : EPR:3 47 12.00 Max. Z-jerk [mm/s]
08:25:42.632 : EPR:3 133 0.00 X home pos [mm]
08:25:42.642 : EPR:3 137 0.00 Y home pos [mm]
08:25:42.642 : EPR:3 141 0.00 Z home pos [mm]
08:25:42.652 : EPR:3 145 373.40 X max length [mm]
08:25:42.652 : EPR:3 149 373.40 Y max length [mm]
08:25:42.652 : EPR:3 153 373.40 Z max length [mm]
08:25:42.652 : EPR:3 51 1000.00 X-axis acceleration [mm/s^2]
08:25:42.652 : EPR:3 55 1000.00 Y-axis acceleration [mm/s^2]
08:25:42.652 : EPR:3 59 1000.00 Z-axis acceleration [mm/s^2]
08:25:42.652 : EPR:3 63 1000.00 X-axis travel acceleration [mm/s^2]
08:25:42.652 : EPR:3 67 1000.00 Y-axis travel acceleration [mm/s^2]
08:25:42.652 : EPR:3 71 1000.00 Z-axis travel acceleration [mm/s^2]
08:25:42.652 : EPR:0 103 0 OPS operation mode [0=Off,1=Classic,2=Fast]
08:25:42.652 : EPR:3 99 0.00 OPS move after x% retract [%]
08:25:42.652 : EPR:3 43 0.80 OPS min. distance for fil. retraction [mm]
08:25:42.663 : EPR:3 87 1.50 OPS retraction length [mm]
08:25:42.673 : EPR:3 91 0.00 OPS retraction backlash [mm]
08:25:42.683 : EPR:0 106 1 Bed Heat Manager [0-2]
08:25:42.683 : EPR:0 107 255 Bed PID drive max
08:25:42.693 : EPR:0 124 100 Bed PID drive min
08:25:42.703 : EPR:3 108 15.00 Bed PID P-gain
08:25:42.703 : EPR:3 112 0.90 Bed PID I-gain
08:25:42.713 : EPR:3 116 40.00 Bed PID D-gain
08:25:42.723 : EPR:0 120 255 Bed PID max value [0-255]
08:25:42.733 : EPR:3 200 584.00 Extr.1 steps per mm
08:25:42.733 : EPR:3 204 40.00 Extr.1 max. feedrate [mm/s]
08:25:42.743 : EPR:3 208 45.00 Extr.1 start feedrate [mm/s]
08:25:42.753 : EPR:3 212 6500.00 Extr.1 acceleration [mm/s^2]
08:25:42.753 : EPR:0 216 1 Extr.1 heat manager [0-1]
08:25:42.763 : EPR:0 217 190 Extr.1 PID drive max
08:25:42.773 : EPR:0 245 60 Extr.1 PID drive min
08:25:42.783 : EPR:3 218 35.01 Extr.1 PID P-gain
08:25:42.783 : EPR:3 222 1.74 Extr.1 PID I-gain
08:25:42.793 : EPR:3 226 175.75 Extr.1 PID D-gain
08:25:42.803 : EPR:0 230 255 Extr.1 PID max value [0-255]
08:25:42.813 : EPR:2 231 0 Extr.1 X-offset [steps]
08:25:42.813 : EPR:2 235 0 Extr.1 Y-offset [steps]
08:25:42.823 : EPR:1 239 1 Extr.1 temp. stabilize time
08:25:42.833 : EPR:1 250 150 Extr.1 temp. for retraction when heating [C]
08:25:42.843 : EPR:1 252 0 Extr.1 distance to retract when heating [mm]
08:25:42.843 : EPR:0 254 255 Extr.1 extruder cooler speed [0-255]
08:25:42.853 : EPR:3 246 0.00 Extr.1 advance L [0=off]

[smiley]

Try lowering the set point for the autotune, if it runs use those settings and try for the higher set point again. I would also check the PID_Max value to make sure you are allowing the resistor to run at full current.

what should the pid_max be? 255?

[smiley]

Updating - I figured the problem was that the PEEK fan was blowing too much on the aluminum heater block. So I wrapped the top section in silicone self-bonding tape, and tried again. Still couldn't get an auto-tune to complete.

So I started thinking - I can't get reliable prints, so I can't make a fan duct. Don't want to special-order something and have it not work. What can I use as a duct in that tight space, around the ~230c hotend, that won't burn or char, is non-conductive, and will effectively block airflow from the fan to keep it off the heater?

I went out and bought a couple of these:

http://www.bedbathandbeyond.com/store/p ... 1013779260

I cut the bottom off one, cut a hole in the center of the bottom, and slipped it over the hotend. Tucked it under and around the wiring, turned everything back on and HEY PRESTO! it works. PID autotune finishes in ~6 minutes and now the temp chart looks like a straight line.

So, progress. Now onto trying to figure out retract settings.

[cope413]

That's a short term fix, but there's no reason you should be having that trouble to begin with. Something isn't right...

[Eaglezsoar]

That's a short term fix, but there's no reason you should be having that trouble to begin with. Something isn't right...

That something that isn't right is running a 5V fan off of 12 volts.
Smiley's third message to this thread "The fan was ordered, but never installed, by my partner in crime. It's a 5v job instead of the 12v one
that I think the seemecnc guys are shipping now, but otherwise the same dimensions. I have it powered off the aux-out bare pads at the
upper-left corner of the RAMBo, just below the heater pins for EXT1. I did it this way because it was what I had on hand, I would have to order (and wait for) a 12v fan."

That fan is spinning at over twice its designed specifications and will certainly
self destruct, it's just a question of when. Spinning as fast as it is creates far too much air in the worst place possible, the hotend. He has a
mini whirlwind stuck in there. The fix is too remove that fan, get one rated for 12 volts - problem solved. No more driving around buying silicone cups,
an autotune that actually works and no fear of the 5 volt fan destroying itself spewing bits of plastic everywhere including the potential of knocking one's eye out.
Then actually calling what was done "progress".

[smiley]

That fan is spinning at over twice its designed specifications and will certainly
self destruct, it's just a question of when.

no, it's powered off 5V aux-out on the RAMBo. I checked with a multimeter before I wired it up. But I assume that the reason I was having problems is that teh fan I have is probably blowing harder than the fan from seemecnc. Since it's hard-wired to 5V I don't have any variable control over speed-- it's on at 100% whenever the printer is powered.

Both of the resistors in the stock hotend are still good, and I've confirmed that thermistor readings are within ~5c of the actual temp at the nozzle/block junction.

My last few calibration cubes look pretty good. Still using Slic3r and printing single-wall stuff in PLA. I have a lot more reading to do though to understand why I'm having problems with bridging/retract.

[Eaglezsoar]

That fan is spinning at over twice its designed specifications and will certainly
self destruct, it's just a question of when.

no, it's powered off 5V aux-out on the RAMBo. I checked with a multimeter before I wired it up. But I assume that the reason I was having problems is that teh fan I have is probably blowing harder than the fan from seemecnc. Since it's hard-wired to 5V I don't have any variable control over speed-- it's on at 100% whenever the printer is powered.

Both of the resistors in the stock hotend are still good, and I've confirmed that thermistor readings are within ~5c of the actual temp at the nozzle/block junction.

My last few calibration cubes look pretty good. Still using Slic3r and printing single-wall stuff in PLA. I have a lot more reading to do though to understand why I'm having problems with bridging/retract.

Then I owe you an apology but there are two aux-outs on the board and when you said it was the upper left corner I assumed it was the 12V one.
I guess it depends which way you orient the board. Please accept my apology.

[smiley]

apology not necessary, and accepted anyway! I admit I still have lots to learn.

Now that I have the basics working I'm finding it hard to stop thinking about what to do next. I really need to set aside a good six or eight hours to just nail down all the calibration stuff- it seems like everyone on this board is having pretty good results once they have the towers all level and square and the extruder dialed in, although there seems to be quite a bit of variety in who prefers which slicer and firmware combination.

[dpmacri]

But I assume that the reason I was having problems is that teh fan I have is probably blowing harder than the fan from seemecnc.

This brings up a good point. Calling the fan a 5V fan or a 12V fan really says nothing about how much air the fan moves. A tighter specification would include the CFM of the fan. The ones I've gotten from SeeMeCNC just say 12V 0.1A, although currently I'm using one that I bought from Jameco that says 12V 0.06A (it's actually this: http://www.jameco.com/1/1/46651-ad0212m ... 12vdc.html). None of them give the CFM on the fans, but the Jameco one says 2.2 CFM on the website. Doing some searching on the SeeMeCNC one seems to indicate that it's 5.84 CFM. The reason I'm not using the stock one is that it was getting pinched in my build platform and kept stopping. Given the different CFM, though, I'm going to create a mount for it now and go back to using the stock one

[aidans1325]

I am having the same problem. I am running stock everything and the hot end gets up to temp without the fan. I've replaces the thermistor twice now and till get the timeout on it. Please Help! Thanks.

[Mac The Knife]

You need to test your heating resistors, you may have only one working.

[smiley]

I am having the same problem. I am running stock everything and the hot end gets up to temp without the fan. I've replaces the thermistor twice now and till get the timeout on it. Please Help! Thanks.

I still have the silicone cupcake thingy wrapped around my hotend. No further problems in the ~100 hours of printing since my last message in this thread. so, it's a hack, and it's not really pretty, but it's working for me.