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Tip for Reducing Purge  

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Peter L
(@peter-l)
Honorable Member
Tip for Reducing Purge

Here's a quick tip for reducing the total purge in a print.

First, you should set your purge volumes for each pair of filaments you use to the minimum purge that will eliminate color banding. The default settings work fine for most color changes, but you may need more for some changes (such as black to white), and with many changes you can get away with less than the default (anything to black requires very little purge, for example).

Once that's done, you should arrange your filaments with the darkest color on Filament 1, and in approximate order from dark to light with the lightest filament on the highest numbered input.

The reason for this is that Slic3r will generally go through the extruders in sequential order on each layer. Filament 1 gets printed first, then 2, etc., and it generally takes more (sometimes a lot more) purge to go from dark to light than from light to dark.

It takes a lot less purge to go from a dark color to a light color if there's an intermediate shade in between, so by ordering your colors this way and making sure your purge volumes are properly set up, you may be able to save quite a lot of purge.

For example, suppose you're printing in black, grey, and white. You want the transitions (where possible) to be arranged as:

Black -> grey -> white -> black

This will take less total purge than Black -> white -> grey -> black.

Respondido : 10/09/2018 6:54 pm
toaf
 toaf
(@toaf)
Noble Member
Re: Tip for Reducing Purge

I swear to the gods I was just thinking about that.
thanks again for doing the science.

I have a Prusa,therefore I research.

Respondido : 10/09/2018 8:37 pm
Peter L
(@peter-l)
Honorable Member
Topic starter answered:
Re: Tip for Reducing Purge

I did a comparison test of the effect of calibrating purge volumes. The print I've been using for testing (4-color Gustav the Turtle, 20% infill and 0.25mm layers) uses two very dark and two very light filaments.

By adjusting the purge volume between each pair of filaments and making sure the filament changes were happening in a rational sequence, I was able to reduce the weight of the purge tower by a third, and get better quality output with less color bleeding.

The default settings in Slic3r specify 140 mm3 of purge on every filament change. I've found that this is almost always more than in needed. Most of the time you can use 100 mm3 or less, and going between similar shades or from a very light to a very dark color may require as little as 60 mm3 for a clean transition. On the other hand, going from black to white needs 250 mm3 (with the Inland PLA I'm using).

Respondido : 15/09/2018 7:45 pm
toaf
 toaf
(@toaf)
Noble Member
Re: Tip for Reducing Purge

thanks again for doing the science. i have a few low layer 5 color prints waiting for a mmu :). i think im sticking with low layers when i get mine. i hope your getting you colir change fail raye lower.

I have a Prusa,therefore I research.

Respondido : 15/09/2018 11:41 pm
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