Welcome to the SeeMeCNC Community

Ive been printing some white (maybe Ultimachine, not super sure though) PLA on my 3mm E3D, and the temps I've been having to use don't make much sense...

I dont have a thermocouple to test it out unfortunately, but Ive been having to bump my temp way up to 250C to get good results and its confusing and bothering me. Ive used a 1.75mm E3D and some opaque orange PLA and i never had to go above 230C, and Ive used another 3mm E3D with this same PLA and I never had to go above 220C if I remember correctly. The Buda I used for a time I had to get to 205 to print with at fairly high speeds (same PLA), though the Buda does have a larger melting chamber. Ive been printing with Cura set to 70mm/sec and Slic3r with what I would call medium speeds (all averaging out to ~70+mm/sec), and a fan set to ~60% speed. Maybe this is right, but its bothering the crap out of me because it goes against about everything I know about this PLA.

Ive also printed Nylon without the Fan on the Slic3r speeds at 270C and it worked fairly well, though I probably could have done it at a higher temp...

You really, really, really need to get a thermocouple. Harbor Freight sells a meter equipped with one for $20.

g.

Ok, there's one at my local hacker space, I'll use it this Tuesday when I go over there... If it's off then how should I correct it?

Likely a stupid question given your level of expertise, but you did remember to change the thermistor value in the firmware, correct?

Yes, it is set to the exact thermistor I have installed, I think its the EPCOS one, its the smallest of the E3D thermistors available.

The smallest one of the two used is the new "semitec" ones:

http://e3d-online.com/index.php?route=e ... blog_id=19

FWIW I have exactly the same issue with 2 1.75mm E3D hotends, printing PLA requires ridiculous (for PLA) temperatures.
Given what others have reported, I think it's just manufacturing variance. I'd guess that some have smoother bore than others, and are less prone to jam.
Basically what increasing the temperature like that is doing is lengthening the melt zone, which is probably reducing the likely hood of a jam.

It's hard to compare E3D temps for PLA to what would be needed with other nozzles. The E3D heater block has a smaller ratio of volume to surface area than a Budaschnozzle or a SeeMe hot end (so it's more susceptible to heat loss), and the melt zone is deliberately kept as short as possible in order to minimize melt creep and retraction blobs. The position of the thermistor relative to the nozzle bore and heating element is also quite different. The temp inside the melt chamber when the filament is moving through at speed is the same between different hot ends, but the thermistor will read something different because the block has to be run hotter and the temperature is being read from a different point.

My Budaschnozzle likes to run about 185-205C for PLA. My E3D likes about 210-235C for the same filament. I don't think it matters much if you're running 1.75 or 3mm filament, although you'll get smoother extrusion out of 1.75.

Yeah, I have it in as the semitec, foot to know i'm not the only one experiencing this issue, I thought I was going mad but seriously I was going a lil crazy because of this.