PLA Not bonding to itself

So I'm trying to print with 1.75mm black PLA filament. I can get the first layer or two to bond beautifully with the bed, but once I ascend above that, it becomes hard for the PLA to stick to the layers that are already there. Additionally, what gets extruded looks like a whispy mess, and by the time the print is over, I have this mass of plastic fibers that don't really do anything. I wonder if anyone has had a similar problem and what they did to fix it.

For further info, I am using a J-Head hot end with a 0.4mm nozzle. My layer height was set at 0.4mm, and I kept the hotend at around 200C. I know that "ideally", PLA is to be extruded at around 185C, but when I bring it down that low, it starts clumping up/beading a lot.

z axis calibration is needed. or flow rate needs to be increased.

Edited 1 time(s). Last edit at 11/14/2013 07:41AM by jamesdanielv.

You can't make 0.4mm layers with PLA through a 0.4mm nozzle. About 0.3mm is the max layer height. The cross sectional area of the filament laid down must be no more than that of the filement extruded into mid air.

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Thanks for the tips guys.

And thanks, nophead. I set the layer thickness lower and increased the hotend temperature to 230C. It's printing beautifully now. I think my thermistor table may not be completely accurate. What tools do you guys recommend to measure the hotend temperature so that I have something to reference the thermistor values I'm getting?

IR thermometers are cheap and easy to use but they tend to be a bit inaccurate on copper and aluminium, you could measure the resistance of the thermistor directly and compare it to the reference table the manufacturer produces. The most accurate way is likely to be attaching the probe of a thermocouple meter directly to the hot end with some thermal paste but they can be rather pricey.

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