Selecting extruder temperature for colour differences

I'm sure I've seen a thread somewhere that gives a rule of thumb, but I can't find it now.

Does anybody have a good general rule for selecting extruder temperatures when switching to new colours/filaments? Is there a good rule of thumb that I can use to identify when I've set the temperature right without actually starting a print? Obviously if it drips then it's too high, and I would hope that my "cold extrude" limit of 180C will prevent any accidents with temps below that but Is there an exact "ideal temperature" that I need to find for each filament or will I not notice the difference as long as I'm +/- 5C of it?

With the Nophead DiBond Mendel90 set up, my starting point for PLA is an indicated 220C. I say indicated because there are many out there who insist that PLA should be printed at 185C and seem to take what is shown up in Pronterface (or other control program) as the whole truth and nothing but the truth. In reality, the real temperature at the melt point inside the nozzle may not be as accurate as shown up in software and there are many reasons for this including inaccurate temperature tables in the firmware, thermistors not sitting where they should do in the JHead and manufacturing tolerances for the thermistor itself.

As far as Nophead's kits go though, he has done a lot of work to reduce these temperature variations and inaccuracies by using close tolerance thermistors, measuring actual temperatures inside the JHead to create the thermistor tables and of course, fitting the thermistors himself prior to dispatch.

To answer your question then ...... start off at 220C and you will not go far wrong with good quality filament. This is the temperature I use for all but a few of my colours, the big exception being Faberdashery Jade Green which seems to like 190C - far too runny at 220C. It is down to experimentation really and in my experience for the sort of stuff I make, +/-5C is not noticeable. Don't get too hung up on getting the perfect extrusion temperature as things can also change from batch to batch. Keep a log though - relying on memory is not a particularly good idea (or is that just me?).

Alan

Excellent answer and exactly what I was looking for, thanks!

I'm currently using 210 as a starting point (because the Jade Green that came with the kit was too runny at 220 as you say!) but didn't want to risk finding out that it is too low when I try one of my many other colours - I bought the rainbow pack from Faberdashery to see what the colours look like in real life, and have only got as far as trying the purple!

I'm using separate filament profiles in Slic3r for each colour so I don't have to remember to change the temperature settings each time I swap filaments. When I get round to having more than one batch I'll start keeping a historical record so that with each new batch I can use an average of the previous batches as a good starting point.

The kit comes with Village green, not Jade green.

220C was fine for it when I started kit production but a few people are saying it is too runny at 220C now. We buy large batches from Fabbersdashery so I think there have only been two manufacturing runs.

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Oh yeah, it even says that on my Slic3r profile. My mistake.

I didn't even realise I had it too hot until a buddy pointed it out on a couple of my Space Invaders. Once I turned it down a tiny bit everything suddenly started looking much better. It's amazing how a tiny tweak in any part of the process can have such dramatic effects.