help diagnose an extruder / hotend problem

hi guys

been trying to sort this now for over a day and just getting no were so need some urgent help

iv just got my old .5mm j-head up and running (new PTFE, new resistor, new thermistor, brass cleaned out)

wired it all up and having step problems

if i set pronterface to 185C then try and extrude 5mm (30mm/sec ) i only pull about 3mm of filament

i have measured the hotend with an infrared thermometer and also a K-type thermocouple both read around 135c!

BUT when the hotend is not heated pronterface reads 23c which also i get using other gear for room temp.

i have tried running the temp at 200C and it gets better.

any ideas?

Did you replace the thermistor like-for-like, or did you just grab a suitable one? You may just need to generate a new thermistor table.

i ordered some thermistors from farnell (code 3878697)

i have tried to generate a new table but when i do i get -10c at room temp.

135C is below the melting point of PLA so I don't think that is the true temperature inside if you managed to extrude with it.

The only way to accurately measure the temperature is to put a thermocouple inside the nozzle.

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[www.hydraraptor.blogspot.com]

nohead your right !

shoved the k type thermocouple down the barrell and 185C

which not comes to say why am i strugging to push the filament?

Some natural PLA needs about 200C and some colours need even higher. For example I use 200C for faberdashery red, 220C for other colours and 250C for lapis blue.

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[www.hydraraptor.blogspot.com]

iv gone back now and checked springs in extruder, re done steps per mm as i forgot i changed hobbed bolt to a Arcol Hyena Hobbed Bolt as i thought orignally a week ago this was caused by a worn bolt.

it seems i only have a problem if i go over 50mm/sec and i can achully hear the filament slipping when printing as well as seaing the solid infill skip and have parts missing.

ill try going hotter. currently im using faberdashery white and have always run it at 185c not a problem

ill try a pyramid at 200c 50mm/sec see if it makes any difference

Viscosity goes down rapidly as temperature increases making it easier to extrude. It is only too hot when it starts to run out like syrup rather than a solid filament.

Also if you want to print very fast you need to raise the temperature because the plastic doesn't spend long enough in the extruder to heat up fully.

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[www.hydraraptor.blogspot.com]

its better at 200C

waiting untill tommrow when i get my .35mm j-head up and working again as atm quality is no were near were it was 2 weeks ago.

but at least atm im back to printing some parts