Improving print quality by testing feed speed and temp

[lanceo]

I'm trying to improve my print quality - I've been getting a lot of stringing/snot. My resolution/physical calibration seems to be ok - lines are straight, corners are sharp, etc. I've been reading a tonne of articles about stringing. They mostly deal with feed, bed temp and nozzle temp.



So I've taken some time this morning to print out the same piece repeatedly and trying different settings. www.thingiverse.com/thing:49263



I'm sure all you old-timers have already done this, but I'm a noob and want to put this info down somewhere where I can search for it later!





I'm using Pink Excelvan PLA bought from eBay. It says speed: 50-100 mm/s @190-210C. I'm guessing that each filament is a bit different.



I'm printing directly on the aluminum plate, which is getting a bit messy with loads of thin PLA lines stuck that I can't get off with my fingernail. I can prolly use acetone or something, but I'm not that desperate yet.



I've noticed that things stick better to different zones in the plate. Note sure why. I'll troubleshoot that later.





GOAL: I'm looking to create the best-quality print, with the least stringing at the fastest speed.



Theories:

- A high nozzle temp makes thinner gunk. Thinner gunk will be less accurate, but should stick better.

- High feed may induce tearout. Increase nozzle temp to compensate.

- Low nozzle temp may induce tearout. Lower feed or increase temp to fix.





Slic3r settings:

perimiters: 35mm/s

infill: 50mm/s

travel for non-print: 100mm/s

first layer: 10mms/s

max print speed: 80mm/s

Infill: 15%









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Print test #1

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I started with a feed of 25% - not sure how fast this is - how can I tell current mm/s in Repetier?



1st layer:

Feed of 25%

Bed temp of 65C

Nozzle temp of 215C



- Good bed adhesion.





2+ layers:

Feed of 100%

Bed temp of 50C

Nozzle temp of 195C



- Nice print - lots of stringing though.





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Print test #2

---------

1st layer:

Feed of 25%

Bed temp of 70C *

Nozzle temp of 220C *



- Good bed adhesion.



2+ layers:

Feed of 100%

Bed temp of 50C

Nozzle temp of 185C *



- Almost no stringing!

- 35min print time.



---------

Print test #3

---------

1st layer:

Feed of 100%

Bed temp of 70C

Nozzle temp of 220C



- Good bed adhesion.



2+ layers:

Feed of 150% *

Bed temp of 50C

Nozzle temp of 185C



- Less stringing then #2!

- But badly torn infill. Note that temp is below the manufacturer-recommended minimum of 190.

- 25min print time.



---------

Print test #4

---------

1st layer:

Feed of 150% *

Bed temp of 70C

Nozzle temp of 220C



ABORT! First layer wouldn't stick and got balled up and wrecked.





---------

Print test #5

---------

1st layer:

Feed of 100% *

Bed temp of 70C

Nozzle temp of 220C



- Good bed adhesion.



2+ layers:

Feed of 200% *

Bed temp of 50C

Nozzle temp of 190C *



- Almost no stringing!

- But badly torn infill - feed prolly too fast.





---------

Print test #6

---------

1st layer:

Feed of 100%

Bed temp of 70C

Nozzle temp of 220C



Good bed adhesion.



2+ layers:

Feed of 200%

Bed temp of 50C

Nozzle temp of 210C *



Almost no stringing!

Nice finish! Best print yet. And fast! 20min print time.







---------

Print test #7

---------

1st layer:

Feed of 100%

Bed temp of 70C

Nozzle temp of 220C



Good bed adhesion.



2+ layers:

Feed of 300% *

Bed temp of 50C

Nozzle temp of 220C *



- Fastest print! 14min print time.

- Nozzle had a difficult time keeping temp at 220, needed to turn off the nozzle fan.

- The whole machine shakes a LOT when doing the 'colouring in' of the surfaces. I'm sure there is some sort of harmonic imbalance at some frequencies. Been thinking about adding 'Z' braces to reduce the shakes and firm up the chassis.

- Almost no stringing!

- Nice finish, but not as good as #6!

- Did I mention how fast it was?











Lessons:

- Lowering feed and increasing bed temp and nozzle temp will increase adhesion to bed.

- Increasing feed will probably require an increase in nozzle temp to allow for the greater flow needed. This will reduce tearout.

- Lowering nozzle temp AND feed reduces stringing, but will take longer to print.

- Defo use different settings for the first layer vs higher ones.

- Superfast feed does it quickly, but the machine shakes alarmingly at times. Finish not bad though!





Now to find out if we have 7 tubes of toothpaste in the house that need pushing! 

[Nelson]

Nice! Thank you for taking the time to do all these tests. Time to add the retractions in as well.

[JohnOCFII]

Yes, retraction distance and speed are two things that I don't really understand -- I mean, I know what the terms mean, but am still unclear on how they impact the prints.

[piscanc]

regarding retraction settings.

distance:
when you have soft filament it squishes in tube, even hard ones zig-zag in a tube a bit. You have to compensate for this.
Longer the feed tube from extruder motor to hotend, bigger the difference in filaments...
With too much distance, you can pull out filament completely from the nozzle, witch tends to clog PTFE insert.
So maximum distance is in proportion with nozzle design.

Retraction speed:
again relates to property's of filament... mostly viscosity, but that changes with temp, nozzle sizes, color a lot...
less important with slow printing speeds, and common materials, but with high speeds and certain filaments, it becomes most important thing.
wrong settings in one direction (low speed) does almost nothing and you have lots of stringing,
too high speed splits filament inside nozzle/hotend and creates bubbles, it could also clog hotend with combination of long travel with certain prints.