I know it has been discussed many times but I have not encountered this idea anywhere so here it goes:
pla as support for petg weakens the subsequent layer adhesion for petg, so you bump the purging volume to get rid of contamination. on larger models where the contamination would spread across a larger area this isn’t such of an issue, but for smaller models, especially when you have floating regions on higher layers, I found that even a volume of 800 is not enough, also you have to babysit the printer just to be sure the poop goes down the drain and not on the buildplate, build up in the chute or knock the fan cover off and stalls the print job (it happened, yes).
what I have done is set the volume to 900 and added another 100 to prime volume, and would have added more to prime but that would have increased the material waste, and also add a significant amount of print time due to the prime tower being larger and printed at every layer.
what I was thinking would help is maybe another variable in filament settings “material change prime volume” that would get used only after the change, and, to keep this prime layer from printing in midair, a regular/tree support could be used at the sides/corners. in this way the purging volume would be kept at reasonable levels and the poop would go down the drain as expected.
also, another variable “material change extrusion multiplier” could be used to increase the primed volume per printed line and keep the overall footprint of the layer smaller. I know that would defeat the purpose of the prime tower because of the added pressure, and to offset that, at the last lines that would equal regular prime volume, the normal multiplier would be used, thus bringing pressure down.
what are your thoughts on this?
I think I would the printhead to reach the pressure needed while printing the central infill, starting to print the rest when purging is enough. so no tower at all for adapt geometries
While I haven’t used it in a while, as I recall the purge volumes are managed in a table where you can independently specify how much purge you want going from one filament to another, in either direction. Those numbers are by definition a “material change extrusion” setting invoked on a filament change.
So I don’t understand your proposal for another parameter that’d do the same thing.
Also, in my experience, even small amounts of dedicated support filament contamination significantly weaking layer adhesion. If the parts you’re printing are decorative, a little contamination might be something you can get away with. If the parts you’re printing are function parts that take a mechanical load or impact stress, you need very high levels of purge. I gave up using dedicated support filament because I primarily print functional parts and they were significantly weaker due to support filament contamination.
Was gearing up to buy a H2D because of this. But now, I’ll get a H2C instead. Just waiting to see what if any issues the earlier adopters are experiencing.
those numbers in the purge volume tables are more of a “color change” purge than a true material change.
and even if you do decorative prints, a “little” contamination makes the difference between a strong part that survives mishandling and one that brakes in pieces at first contact with the floor.
I only print toys and stuff for my daughters and I hate spending hours printing only for it to break because contamination. I would imagine that someone who makes a living from printing and selling stuff, would prefer loyal customers due to quality, and not a “I’m not buying from this guy anymore, it broke on the second day of usage” reaction, even if the stuff he/she sells are purely decorative.
Still not understanding. The purge table is for filament. It doesn’t know or care what the filament is. Works the same for small purges when printing colors with the same filament, or large purges when using a support filament.
The only problem with it is, for support filaments, in my experience anyway it doesn’t go high enough. But when using dedicated support filaments, to avoid weakening the primary filament, extremely high/wasteful levels of purge are needed.
Which is why, if you’re doing functional prints where strength is critical, an H2D or H2C is really the only workable solution. Dedicated extruders for primary and support so no mixing or purging is required.
that’s exactly the point, doesn’t go high enough. probably because 900 (which is max value in the table) already fills the chute and BL didn’t consider breaking it into smaller chunks.
of course a tool changer would be ideal for different materials, but some do not have the money / do not want to spend it or simply consider that one printer is enough for their usage, thus a solution for different material support is required.
you can multiply your heart out, max is 900 