Is my hot end failing?

[Deereengineer]

All of a sudden my extruder is jamming and my drive gears are stripping the filament. The melted plastic stream will flow out but after 5 seconds or so it slows and stops and then it stripps. using a wireless thermometer I pointed the laser all around the extruder end but I could not find any temperatures above 170 c but simplify 3d thinks it is at 245c. has anyone tested the temp on there hotend this way?

[TomR]

Your problem sounds similar to the one I just had. I measured the outside temp with a multimeter and got around 220 instead of the 250 reported. I had a clicking sound which I thought was the gear not able to push the filiment through the nozzle (V4) because the temp was too low. To make a long story short, it was the pinion gear inside the extruder motor that was partially stripped. I determined that I was not able to measure the outside temp of the hotend with my meter accurately.

[ednisley]

I pointed the laser all around the extruder end

IR thermometers don't measure the temperature of surface inside the laser spot!

The sensor peers through that large opening (just below or above the laser aperture) and "sees" a 10° beam angle. The active area is an inch in diameter at half a foot / two inches at a foot and doesn't get much smaller as you get closer.

The thermometer reports the average temperature based on the IR emission of what it sees inside that area. When the thing you're measuring doesn't fill the area, the temperature includes all of the background visible around it, which is why extruders show up unnaturally cool. Small things don't fill the sensor unless you jam the thermometer's snout right up against them, which is a Bad Idea for plastic cased thermometers... [grin]

IR emission depends on both the temperature and the surface's IR emissivity. The thermometers assume an emissivity of 0.95, which is true for most organic / painted / rusty surfaces and completely wrong for bare metals like aluminum, steel, and copper. Kapton & silicone tape seem to be OK, but you must stick masking tape on the shiny end of a stepper motor to get a reasonably accurate temperature; the black paint on the side works fine.

Bottom line: as long as the thermistor reports a steady temperature, that's almost certainly the extruder's operating temperature.

Given the trend around here lately, I suggest a fat filament in a skinny hole lies at the bottom of your jamming troubles...

[insta]

fat filament in a skinny hole

name of my band in middleschool

[ednisley]

in middleschool

Shudder

[Jules]