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glob after travel ?

Posted by riggg 
glob after travel ?
January 21, 2013 12:09AM
I can print a box just fine, with the walls looking very smooth. But if I print something with a lot of traveling the quality is not as good. Any idea? Should I raise/lower temperature, slower/faster travel, adjust z-endstop, retraction setting in slic3r in at -.5mm@60mm/s.

Re: glob after travel ?
January 21, 2013 12:24AM
That's caused by two things: insufficient retraction, and slow travel moves. Your problem appears to be retraction. -0.5mm is actually not retracting at all, it's pushing 0.5mm of filament out! You want that number to be positive. I have mine set to 1.2, but it's pretty machine-specific, so you might have to experiment a bit.

After you do that, if the problem persists, try speeding up your travel moves to 200mm/sec or higher. A well-tuned machine should be able to achieve at least 200 mm/sec, if not 300 or higher if you have a lighter-than-average X-carriage and extruder setup. That way there's less time for a blob to form since the nozzle is moving so fast during travel moves.
Re: glob after travel ?
January 21, 2013 02:34AM
I'll have to check I may have it set to positive .5 on second thought. I initially lowered it since the head does not move while retracting, thus forming a blob at the end on a perimeter, Thanks, I will try 1.2 with a fast retract time.? (65mm/s)?
Re: glob after travel ?
January 21, 2013 03:07AM
what temp are you running at? if possible lower the temp a little more. I'm skeptical about some of these really high feedrates, and would guess that during any acceleration calculations for flow rate will be inaccurate, and never consistent.

I should also mention that at 300mm/second the extruder head would look like a solid blurry object.

also if you have cool enabled raise your minimum feedrate because your extruder may be oozing a little. perhaps also get a bigger fan.
what is your z height resolution as well?

can you list all your slicer settings?

Edited 2 time(s). Last edit at 01/21/2013 01:47PM by jamesdanielv.
Re: glob after travel ?
January 21, 2013 06:46PM
using with small cooling fan attached to carriage

setting in screen shots attached
open | download - 1.JPG (30.5 KB)
open | download - 2.JPG (31.4 KB)
open | download - 3.JPG (21.1 KB)
open | download - 4.JPG (34.7 KB)
Re: glob after travel ?
January 21, 2013 08:04PM
as mentioned above your travel speed is very low @ 130mm/s. I find that travel speeds less than 250mm/s causes blobs even with a bit of retraction.
Re: glob after travel ?
January 21, 2013 10:45PM
try changing your max speeds from 60mm/s to 40mm/s and see if it helps. it may be possible that extrusion pressure is uneven because the feed rate fluctuates too much for those small moves. the processing power of arduino can not do 60mm/s around circles.

I did not see the cool menu in the images taken. So i don't know what you are using for those settings.

also change minimum distance to 8mm from 2mm for travel after retraction, this way the perimeter and small perimeter will work without a separate retraction for each set of moves, probably the main issue with blobs in this case. it still is small enough of a distance to retract between the solid areas of the part being printed.

i find that having All perimeter settings set to the same value helps keep consistent nozzle pressure and is easier to control. the external perimeters you have set to 95%, change that to 100%

IMHO, and YMMV, bets of luck!
Re: glob after travel ?
January 22, 2013 12:20AM
Gulf Wrote:
> as mentioned above your travel speed is very low @
> 130mm/s. I find that travel speeds less than
> 250mm/s causes blobs even with a bit of
> retraction.

Most RepRaps can't reliably travel at 250 mm/s... I have zero blobs using 1 mm retraction and 130 mm/s travels.

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Re: glob after travel ?
January 22, 2013 02:38AM
The cooling I just turn on a fan M106 in pronterface.

The globs seem to be from traveling from one side of the print to the other. On layer1 there will be a nice perimiter then layer2 when the head passes over in travel a bit of plastic sticks to the edge of the perimeter, such that it makes a branch that grows out away from the perimeter, as seen in "glob2" (the picture initially posted).

I had prints turn out great when printing at 60mm/s for perimiters just after I cleaned the few glob branches off.

I think it may be either, ozzing (so temp problem?), wrong z-endstop height(adjust up?), or retraction settigns (more retraction? (but I initially lowered to .5 retraction from 1mm cause a slight blob formed while the head stood still retracting))
Re: glob after travel ?
January 22, 2013 06:44AM
I have tested that using marlin firmware + Slic3r 0.7.2b, gives better results when compared to splinter + Slic3r 0.9

Re: glob after travel ?
January 22, 2013 07:43AM
I have read that many people have there travel speeds around 250mm/s and that is what I currently run, I assumed that was most people were running at. In the competition section most people are running quick travel speeds from what I remember reading but as cameron pointed out it's possible to get good prints at lower speeds.

Also swich to Kisslicer, Sli3er is not worth the trouble. Read some of the coments in the Tantillus forums about how much better the prints are if you need convincing.

Edited 1 time(s). Last edit at 01/22/2013 07:55AM by Gulf.
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