Purge line different sometimes & too high flow for small nozzles?
 
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Purge line different sometimes & too high flow for small nozzles?  

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vintagepc
(@vintagepc)
Member
Purge line different sometimes & too high flow for small nozzles?

I've occasionally noticed the purge stripe at the front edge of the print is different - normally it is about 1/3 the width of the bed and the last part extrudes at a higher rate making it a fatter line.

But some prints will do a longer line ~2/3 the width of the bed, all at the same extrusion rate. Any idea why this happens?

On a related note, the default purge line has too high a flow rate for 0.2mm nozzles, it makes the extruder click/skip This happens despite having selected the correct profile in slic3r. Can I prevent this or is it something I have to live with? Remainder of the print is fine and has no skipping issues. Tightening/loosening extruder screws makes no difference.

Posted : 10/02/2019 10:06 pm
bobstro
(@bobstro)
Illustrious Member
Re: Purge line different sometimes & too high flow for small nozzles?

I found that the purge line prints across a range of nozzle sizes without problems provided I disable Linear Advance ahead of time.

The purge line is controlled exclusively by the startup gcode. If you're using different printer profiles in Slic3rPE, or gcode generated by different slicers, that will account for the variances you're seeing.

You can customize it in startup gcode.

My notes and disclaimers on 3D printing

and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

Posted : 10/02/2019 11:46 pm
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(@)
Illustrious Member
Re: Purge line different sometimes & too high flow for small nozzles?

I've seen the purge line length change without any changes in Slic3r PE settings. I've not examined the files afterwards, but I have no reason to think they were corrupt. Something in the printer simply misinterprets the move - normal vs relative. And it seems random.

Posted : 11/02/2019 12:04 am
vintagepc
(@vintagepc)
Member
Topic starter answered:
Re: Purge line different sometimes & too high flow for small nozzles?

Yes, no custom printer profiles or tweaks on my end to that G-code, just the prusa defaults

Posted : 11/02/2019 12:24 am
bobstro
(@bobstro)
Illustrious Member
Re: Purge line different sometimes & too high flow for small nozzles?


Yes, no custom printer profiles or tweaks on my end to that G-code, just the prusa defaults

Do you get the same purge line when you print the same gcode again? Does it stay with the gcode (e.g. a week later)?

My notes and disclaimers on 3D printing

and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

Posted : 11/02/2019 3:58 am
vintagepc
(@vintagepc)
Member
Topic starter answered:
Re: Purge line different sometimes & too high flow for small nozzles?

No. I did the same print 3x in my "2 axis crash" thread. One purge line was extended, the other two were short, IIRC

Posted : 11/02/2019 4:40 am
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(@)
Illustrious Member
Re: Purge line different sometimes & too high flow for small nozzles?

Just yesterday I had a purge line that was inverted: fat to start, skinny towards the end; but the length was correct... lol.

Posted : 17/02/2019 8:50 am
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(@)
Illustrious Member
Re: Purge line different sometimes & too high flow for small nozzles?

And today I was printing the gcode from Prusa for the Mk3S parts, and third try the purge line was long. Again, this was Prusa's gcode file, not mine, and in several attempts to print the purge line changed length.

ps: I was working on getting the PETG to stick... kept balling up on my nozzle; hence the multiple attempts.

Posted : 19/02/2019 12:03 am
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