Variations in filament performance

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Variations in filament performance

Postby tmccafferty » Fri May 10, 2013 2:54 am

I was wondering how much variation people are experiencing with filament. I have used from two different spools of PLA. One is red from Makerbot. Mother other is black from some other source (I'm not sure where it came from).

The red was the first I used and I basically tuned my BOT to it. The print quality is very acceptable both on the sides and top surface. I get the best results at 200deg C. I am printing pretty slow shooting for quality rather than speed. I need to work on speed some day.
I just received and started using the black. The sides of my print looks as good as the red. However, the quality of the surface is lacking. I have adjusted the average diameter and experimented with temperature (185-205) but can't get as good of quality on top surface. It's kind of rippled almost like there is too much plastic being extruded. I have checked diameter and extruder calibration. I even went down a bit below the actual diameter but began to see gaps in the passes.

Any ideas? I don't have good enough light tonight for a good photo of the black surface.
Do you experience significant differences in brands of filament?
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Re: Variations in filament performance

Postby SystemsGuy » Fri May 10, 2013 11:33 am

Filament varies, and between the dye content and impact additives, I find variances between different colors from the same manufacture. I find the easiest way is to pick an object you will use to calibrate consistently over time - I use Moria's Treefrog - and then dynamically adjust your e-steps to get the proper extrusion.

There a great example / description of doing this that Triffid Hunter wrote a while back - http://reprap.org/wiki/Triffid_Hunter%2 ... tion_Guide - that describes a method of watching the infill to see when it's "right" to fine tune your extrusion. I find this helps a lot, and gets easier as you do it more.

Also with PLA - most of it will extrude over a *large* temperature range, and in general has a more matte finish at the lower temperatures and more glossy at the higher. I've got some Protoparadigm that will print happily from 165 to 215c. Since heat is the devil for PLA, you really want to go as low as you can - unless you are shooting for the glossy look - and then cool the heck out out it.

Here's something I just knocked out that I think came out stunningly well, in Diamond Age Black & White.

P1020244.JPG
Yin & Yang Vase, 195mm http://www.thingiverse.com/thing:85951
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Re: Variations in filament performance

Postby tmccafferty » Fri May 10, 2013 12:27 pm

Really nice print! Thanks for the link. I'll dig into it.
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Re: Variations in filament performance

Postby orcinus » Fri May 10, 2013 1:23 pm

Awesome print, SystemsGuy.

Just one thing to add re: PLA and printing cool.
With some PLA stock i've learned that going too low is actually detrimental because it *encourages* curling in sharp corners and negative angles. Yes, i know, that goes contrary to common sense for PLA, but that's what i've experienced on numerous occasions: print at 190 and it curls like crazy, print at 210 and it's (almost) fine, go above 210 and it gets worse again (due to not being cooled down fast enough).

The best explanation i can think of is that below the sweet spot, layer adhesion is not high enough and previous layers don't get enough adhesive force to keep negative angled surfaces (i.e. perimeter that's expanding from layer to layer and only sticking to the previous layer with it's inner edge) from deforming upwards as it cools.

As you go up from the sweet spot again, the regular effects of not being able to cool the filament fast enough start to kick again and the results again get progressively worse.
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