Testing true temperature

Hello, do thermistors become inaccurate after a time?

I was printing fine with both PLA and ABS up until a while ago, looking at the filament leaving the nozzle it appears to be fairly sluggish, as if it is not hot enough or only just approaching melt temperature, consequently it no longer sticks to the bed.

My printer is an Ormerod 2. When I first started printing with it a year or so ago PLA was at 190 degrees and it worked fine, later I had to increase it to 225 degrees to get it to stick, now it is not sticking at all hence my question about thermistors.

Is there any way to check the actual temperature of the hot end? or should I just go with a new hot end.

Any suggestions gratefully received.


Brian

One way is to get a digital multimeter that includes a thermocouple probe. Then feed the thermocouple probe into the hot end in place of the filament.

A thermistor should continue to read fairly accurately unless it's maximum temperature rating has been exceeded. A new Ormerod thermistor is very cheap anyway, from RepRap Ltd or Emakershop. Check that the PTFE heatshrink is included when ordering.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

It's much more likely your filament has changed or your nozzle has built up some dirt inside.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Thanks for your advice gentlemen, I have been meaning to fit a new E3D V6 hotend for some time now so I might do that next as it will be a new thermistor, heater and nozzle, the one I have is only a Chinese repro but it looks like it will be ok.

Many thanks,


Brian