Coast at end, what does it actually do ?

[glx51mm]

Hello everyone !!!
I got a Makergear M2 about a week ago along with a copy of Creator and I am quite surprised at the quality of the prints. I was able to print a few test cubes at 0.1 with amazing results. And then my sheer enthusiasm was replaced by frustration the moment I tried to print the calibration pyramid. I have printed more than 20 by now and the best one was the very first at 0.1 layer height. Had to disable the auto width though.
I tried to enable the "coast at end" but I couldn't notice any variation of the path of extrusion or any print quality improvement. So, how does this feature work and how does it help ?

[Simplify3D]

Hey there!

Glad you've been getting some great quality prints using Creator and welcome to the boards! While the software comes with some very intelligent presets, it can also be very easy to make a few minor changes that significantly impact print quality. You probably have a much better chance at getting spot-on advice if you post the .fff file you have been using to print your calibration pyramids. I can tell you from experience, that things start to become very tricky at extremely small layers heights, so you might want to try printing one of the pyramids at a 0.15mm layers to see if it helps isolate what factors might be effecting your results.

In fact, we print calibration pyramids on our test machines all the time, and we usually get great results using the default settings. The screenshot below is using a stock printer, stock filament, and default settings included with Creator. Literally no tweaks at all, straight out of the box

pyramid.jpg (55.06 KiB) Viewed 20250 times

In reality, we can get much better results if we actually tailor the settings for this specific part, but I just wanted to illustrate what the default settings should be capable of doing.

Now about your question on extruder coasting, this is similar to the old dwindle features used in skeinforge. When you are printing you can build up significant pressure inside the extruder trying to push the melted plastic out the tiny hole in the nozzle. The coasting feature allows you to turn off the extruder a few millimeters before the end of the tool path to allow this pressure to equalize without leaving blobs on your part. When combined with well tuned retraction settings, it can be a very powerful combo. Few other slicers actually support this so it can make a big difference in your print quality!

Hope that helps and let me know if you have any other questions!

[glx51mm]

That is one nice pyramid !
But, far from what I can achieve with default M2 settings. I am using Makergear black PLA on a stock printer.
I printed a few pyramids so you can realize how bad this actually comes out with default settings which is quite weird.
I have achieved much better results with different settings, especially at 0.1 mm.

Default PLA settings for high quality, no coast selected

Default PLA settings for high quality, no coast selected

default-015-no-coast.JPG (295.94 KiB) Viewed 20239 times

Default PLA settings for high quality, coast at 1mm

Default PLA settings for high quality, coast at 1mm

default-015-coast-1mm.JPG (276.33 KiB) Viewed 20239 times

[glx51mm]

Default PLA settings for medium quality, no coast selected

Default PLA settings for medium quality, no coast selected

default-025-no-coast.JPG (315.23 KiB) Viewed 20239 times

Default PLA settings for medium quality, coast at 1mm

Default PLA settings for medium quality, coast at 1mm

default-025.-coast-1mm.JPG (313.57 KiB) Viewed 20239 times

[Simplify3D]

So theoretically, we printed the exact same part using the exact same settings (our photo was default PLA, Medium quality, no coast). We have also printed plenty of those using the stock MakerGear black PLA and get the same results. So really all that's left at this point is machine or material variation. The excessive stringiness and poor ooze control that you are getting on the 4 small pyramid pillars makes me think this might be related to high temperatures (since those small areas would be affected most by something like that).

Can you verify that your fan was running at 100% during the build? I know some of the M2 fans have a tendency to stick at times. And is there any chance your extruder is running hotter than you are intending? Any chance you have a laser temperature gauge or a spare thermocouple to verify it is actually stabilized at 190 degrees?

[13brv3]

Simplify3D,

Can you provide the pyramid stl file you printed, or a link to it? In a brief search, I found several that were similar, but I'd want to try this with the exact same file if possible.

Thanks,
Rusty

[Simplify3D]

I believe this is the one: http://www.thingiverse.com/thing:8757

[glx51mm]

The pyramid I am using is this one: http://www.thingiverse.com/thing:21303
The temp is quite high for this PLA and yes it brings up problems. However, I tried the same print at 175. Still problems appear but it is a bit better than the ones on the photos.
The fan I can verify it was at 100% spinning fast. The extruder temp I checked with an IR thermometer and it was spot on.
I printed about 20 more pyramids yesterday but none came out nice.
Some of them were printed fine up to almost one third of the height and then messed up.
So, I went a step further and took a high speed video with my camera. The video isn't the best as slow motion with this camera requires too much light but still is evident what is going on.
The file is here: https://docs.google.com/file/d/0BzbYiED ... sp=sharing
Watch from 0:05 to 0:10.
You can clearly see that when the head travels from one pillar to the other a little filament comes out of the nozzle. Once the head arrives at the next pillar, it retracts !!!
Shouldn't it retract just before leaving the first pillar ?

[glx51mm]

Another pic of default settings for medium quality using PLA without using coast but using a temp of 175 degrees.
I also noticed that sometimes for a moment the flow out of the nozzle becomes much greater and it messes up everything.
btw I found a video (http://www.youtube.com/watch?v=9Ufy47O5BmU) of an M2 building a pyramid (skip to 1:07) which looks quite the same as mine.
He is using Creator without active cooling on the pyramid as he mentions.
Maybe I have to try with a different fan....

default-175temp.JPG (314.62 KiB) Viewed 20202 times

[glx51mm]

Just tried with a bigger and faster fan connected to a separate power source. Same result...