[sudo-discuss] lulzbot TAZ 3d printer is dead

[Hol Gaskill]

i have to disagree on that assessment - if it's under closed loop control, it should be shut off once it reaches a certain temperature well below failure temp.  if the thermistor reading is lagged significantly behind the temperature of the heating element then it will ramp up past the high temp each cycle for a period of time even with the thermistor functioning perfectly.  not sure on conductivity of jb weld but i'd bet a 6 that pack thermal grease (either 'arctic cool' type or lithium grease) will solve the problem.  

on May 01, 2014, Jake <jake at spaz.org> wrote:
>once the resistor gets hotter than it should, it probably burns away >whatever paste is conducting its heat to the block, and runs away, so of >course there is no thermal glue there now..>>I believe putting a cyindrical resistor in a cylindrical hole in an >aluminum block is a recipe for disaster, unless you have magic thermal >glue that is also pliable, since everything is expanding and contracting >with every thermal cycle.>>I don't have any reason to believe there's anything wrong with the >thermistor, which is the temperature sensor.>>i'll probably be there on saturday. Do you know if JB weld is a good >choice for gluing the resistor in place?>>-jake>>On Thu, 1 May 2014, Hol Gaskill wrote:>>> just popped by the space and noticed the air gap - should probably use >> some kind of high temp thermal grease. my bet is that the heater was >> getting significantly above max temp but that heat wasn't getting >> conducted into the block and into the thermistor. i'll check mine and >> bring in on saturday for omni hackathon with a side of 3ding - will you >> be around? would also like to learn how to work with thermistors.>>>> cheers>>>> on May 01, 2014, Jake <jake at spaz.org> wrote:>>> if the TAZ we has now has the 2.0 schnozzle then it might use the 4.7 ohm >resistor>as seen here:>http://www.lulzbot.com/products/heat-resistor-47-ohm>>of course the printer will work with a different resistor as long as it >provides>enough heat to print. Worst case we have to insert M220 S50 to >slow it down to half>speed printing until we get a better resistor...>>what value resistors do you have?>any special glue?>>On Thu, 1 May 2014, Hol Gaskill wrote:>>> this is what i pull>up for the part - 6.8 ohm:>> http://www.lulzbot.com/products/heat-resistor-68-ohm>>>> sounds like the most common reason for these failing is over temp from miscalibrated>thermistor>- i did find those 3 i got for the type a machine and if it's the same>part i'll>bring them in.>>>> on May 01, 2014, Jake <jake at spaz.org> wrote:>>> so i spent all evening (and some of last night) to finally spool up the>>gigantic>pile of black filament for the TAZ 3D printer.>>i finally got it hung from>the wall>with a!> dust cover over it and ready to >feed smoothly into the printer, and then>i discovered>that the heating >element in its extruder head is dead.>>oh well.>>so,>we need a>new resistor to go in there. I don't know what the original >spec is, but>since the>whole thing runs on 24VDC and assuming 24 watts of >heat, that would be>a 24 ohm>resistor or so.>>Is someone other than me interested in contacting Lulzbot>and asking>>whether they want to send us a new resistor, or if they can tell us what>>part number>of resistor we should get as a replacement?>>-jake>>P.S. yes i tested>the resistor>and it's dead, infinite ohms, it's burned >out. When we get a replacement>we can>glue it in there better than they >apparently did. If the glue goes bad it>dies.>>>>>>