In light of the fact that Prusa’s multi material kit is projected to ship soon if it hasn’t already, what dissolvable support material would you guys recommend for PETG in the Y-splitter setup? Does PVA have too much of a temperature difference? I’m printing most of my PETG at 255 C.
Glad you asked cuz i was fixing to lol
I don’t know if anyone’s tried that that with the new PVA blends. I heard that PVA doesn’t like to purge easily. Try it but expect to spend some time dialing it in.
Try a simple test? Print a light colored filament and then switch to a dark filament and start printing. See how long until it has full darkness coming out of the hot end. You should expect that amount of time and filament to be wasted each filament change. Maybe worse. You may also have a temperature diifference which the hot end will need to overcome before it starts pushing filament out.
A cartesian style printer can handle two separate hot ends better than a delta style can because the hot end will not be wiggling if it moves too fast like it would on a delta style printer.
Perhaps you should avoid using two different filaments with vastly different properties in the same hotend and use two different hot ends instead. Just my 2 cents.
There are a number of settings tweaks for support material by the way. Perhaps some of them would make the dupport material remove easily without causing issues in filament swap time or incomplete nozzle purges.
Well judging from Prusa’s last update on it they printed a part with selective soluble supports. So like Simplify3D’s dense support for a couple bottom or top layers then use the main material for the rest of the support towers that don’t touch the printed part to save on material. Their purge tower should be able to reasonably purge away the PVA when it changes material. I’m simply wondering if the temperature difference is going to cause issues with the PVA getting too hot or the PETG trying to be extruded at too low of a temperature. I guess I could always write a post processing script to add a G4 or M0 command to dwell for say 20 seconds. Or if they use the M109 command to heat when changing materials that could work too.
The selective soluble support preview was a couple updates back. Here’s a pic: http://www.prusaprinters.org/wp-content/uploads/2017/02/Soluble_800_600.jpg
I wouldn’t run PVA with anything but PLA. The exact temp tolerance depends a lot on blend, but in general, if you overheat PVA it rapidly degrades into horrible tar and more or less destroys the hot end. I really don’t see that working with PETG.
That’s severely disappointing. What about HIPS? Would limonene damage PETG?
E3D’s Scaffold is designed for use with PETG
@Tim_Elmore It was designed for their Edge filament which is most likely a blend between ABS and PLA. Scaffold has a recommended print temp of 215 C and is PVA based. So it really wouldn’t work well if Ryan says PVA tends to degrade at high temps and I print most of my PETG at 255 C.
All PVA filaments are a blend of polyvinyl acetate (PVAc) and polyvinyl alcohol (PVOH), but the ratio varies. PVOH is more dissolvable but is garbage as a pure polymer so you need the PVAc to improve the properties. Scaffold seems to have a higher PVAc content and less PVOH, with some secret sauce to make so it’s less pernickity than “standard” PVA in terms of self-destructing from contact with air and cross-linking in the nozzle. But it WILL still crosslink in the hot end at high temperatures.
@Tim_Elmore Not through the same nozzle! The printing temps are too different. You’ll pyrolyze the Scaffold while purging to/from PETG.
@Adam_Steinmark Edge is a PET variant. Most modified PET blends are “PETG” where the G means “glycol modified” but there’s a wide range of options for how they could have modified it. I don’t know if Edge is technically a PETG or a different modified form of PET.
While I’m on the subject of names, pure PET is a “polyester” (and is totally unprintable because any moisture in the filament destroys it when it melts) and modified PET formed from two or more different PET-like compounds like PETG is a “co-polyester.”
@Adam_Steinmark As Ryan said, Edge is a PET based filament.
@Ryan_Carlyle Time in the nozzle seems more important than temperatures for PVA stuff. Plus can’t you move the hotend temperature up/down in the purge tower? PETG will still extrude at ~220C, so move to purge tower, drop to 220C, switch to Scaffold, purge, resume printing, move to purge tower, swap to PETG, increase to 250C while purging, move back to print.
Basically use the purge time for adjusting temperature.
@Tim_Elmore Standard PVA will burn up in an instant at 220C, but Edge is seemingly a lot less sensitive. Purging it with PETG at 220C might work. What I’m not sure is whether you’ll get good enough plastic displacement with the PETG so cold – will there be dead zones where it doesn’t purge well because the viscosity is so high at 220C?
I think the idea of the same nozzle being used is screwed because at least some of the other filament will be in the nozzle at the time that it is trying to purge and one filament will not want to extrude at the low temperature and the other will clog the nozzle at the high temperature. The concept is screwed. I say a different support material filament that is close to the printing filament or check out the nifty support material options like a gap of 0.5 to 1mm between the support material and the part or less interface fill amount.
I think the two filaments used is a switching extruder should have an overlapping temperature range. You could do the purge tower at a temperature in the overlapping range then before switching to the optimal temperature for the filament you just switched to.
@NathanielStenzel why would I use such a large gap?
And HIPS should be able to work fine with that. I can print HIPS at 240 C. I’d much prefer to clean my parts with standard tap water if possible though.
I do not know the optimal gap. I only know that Cura and/or Slic3r are capable of configuring the gap and other related settings for the support material.