Posts Tagged ‘ hotend ’

C-Bot 3D Printer: Supercharging the Volcano

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When I installed the 1.2mm E3D-v6 Volcano nozzle, I noticed that when my PLA cooling fan kicked on, the hotend would have a really hard time maintaining temp running at a ‘high’ (45mm/sec) extrusion speed (for the Volcano):  If starting at 220 deg, when the fan would kick on it would just drop and drop, and I’d stop the print or kill the fan when it hit 200 deg.  If I dropped the speed down to say, 10mm/sec, it could keep up.  This made me think fan+cold filament was too much for the hotend.

After much discussion on Google+ (here, and here), I tried a variety of things, none that got it working 100%.  I re did the Marlin auto-PID with the fan on full blast:  This got it to the point the temp would drop some 10-15 deg, then slowly creep back up.  But this is far from optimal.

The thing that tipped me off was the suggestion to figure out what the power is of the heater-cartridge in my Volcano hot-end:  Measuring the resistance gave me 7.1 ohm, which equal to 20.3w (voltage^2 / resistance = 12v*12v/7.1 = 20.3w).  Checking online, I noticed that there are 40w heater cartridges as well, so I picked one up (I got that one simply because it could be shipped via Amazon Prime…).  Installation ensued:

volcanoUpgrade

And that my friends, is the secret sauce:  After I got the new heater cartridge installed, I re-ran the PID-Autotune in Marlin (via Simplify3D)…

M303 E0 S200 C8

…waited a number of minutes for it to finish, then crammed the three values back into my Configuration.h, uploaded that via the Arduino IDE to the Rumba, and I was in business:  Not only does the hotend heat up faster now (220 deg in 1min 50 sec with full fan compared to 2 min 30 sec with no fan), but I can maintain hotend temp with 100% 24cfm fan kicked on.  It’ll drop maybe 3 deg when the fan blasts on, then pull right back up to temp.

So a note to any of you Volcano users:  Make sure you have the 40w heater cartridge (the one with the red leads) not the 25w one (blue leads).

I measured the new heater before I put it in:  4.1 ohm resistance, which equals 35w, not 40w.  But it works, so I’m happy :)

Another thing learned:  When you issue a M105, and get something like this back:

RECEIVED: ok T:206.1 /220.0 B:26.0 /0.0 T0:206.1 /220.0 @:127 B@:0

The @:127 is the ‘power’ going to the hotend.  Note that 100% = 127, not 255, in this instance.

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2016
01/20
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Trouble in paradise: The Replicator quit extruding…

I’ve been using my Makerbot Replicator (1) to print all the parts for my new C-Bot build.  However as of a few days ago, it suddenly quit extruding correctly.

I print almost entirely in PLA, usually from 200-210 degrees.  Suddenly, I couldn’t get anything to print unless I raised the temp to 230-245:  Pretty crazy for PLA.  And the surface quality was terrible.  Any lower in temp and I could hear the extruder stuttering, and it wouldn’t really extrude much at all.

Leading up to this I had been printing at 120mm\sec, at .3mm layer height:  Squeezing a lot of plastic out of the nozzle at that rate.  I noticed a bunch of melted filament around the top-rear of the heater block (you only noticed it when specifically looking for it, couldn’t see it from the front\sides):  The only way it could have got there would have been backpressure from the nozzle squeezing it out of an improper location up-stream.  My guess is that this somehow started the domino effect to cause whatever was screwing up my current extrusion.  It had completely encased the back of the heater cartridge and wrapped around the thermocouple wires.  I had to heat the whole block up and carefully pick it away without damaging any of the wires.

Thanks to tips from this forum I got it resolved:  One suggestion was that the kapton tape that insulates the thermocouple had worn through, and by grounding to the heater-block it was giving inaccurate temperature readings.  This seemed like a prime culprit since I had to crank my temp settings so much higher.

I’m not sure specifically which steps fixed it, but this is what I did:

  • Did a complete teardown on the hotend, to the last bolt.  Removed old kapton, cleaned up head, wrapped in new kapton.
  • Removed heater cartridge and thermocouple : Didn’t noticed any wear-through on the thermocouple kapton, but added more just in case.
  • Did however noticed where the wire leaves the thermocouple and bends up around the heater block : one of the bends looked a bit frayed, and was mighty close to the heater block itself:  Added extra insulatory kapton at that junction.
  • Added a new nozzle, just to weed that out.
  • Re-bed level, etc.
Extrusion was immediately was back to normal after that, thankfully.  I was beginning to think the Replicator was getting jealous of the C-Bot build…. 😉
Some words of wisdom from Ryan Carlyle on the above thread:
General rule of thumb is that PLA does not print reliably over 10 mm^3/sec with a typical Replicator type hardware setup. At 0.3mm layer height, 0.4mm extrusion width, and 120mm/s, you’re doing 14.4 mm^3/sec. That’s reasonable for ABS (which melts faster) but not for PLA. Raising the temp may cover the symptoms for a while but it can also lead to charred filament and worse clogging issues later on.
2015
06/23
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