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[UM3] Change support material type within Cura midprint?

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Hello, I have an Ultimaker 3. I recently got a hold of some PVA, but seeing as it is so expensive I was starting to think of ways to cut down on the actual usage of PVA filament itself but still keep the nice water soluble idea alive. I have TONS of PLA so that won't be an issue with using one filament and not the other.

One solution to this is to theoretically print the support material out of regular PLA, then only print the connections between that support and the actual model in PVA. So it kind of looks like PVA is gluing two parts together, to help better visualize it. Then, when putting the model into water, the support material pops off the part nice and cleanly like it used PVA as support material this whole time.

Is this even possible to do in Cura? Is it possible to do elsewhere? This can theoretically save lots of PVA filament that I, frankly, do not have the money to splurge on after buying the printer. Thanks in advance.

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Hi,

I don't think that's possible. For the Ultimaker 3 you have a special print core (BB) that's designated for PVA. If the firmware would support it, you could:

Pause print, switch print core from AA to BB, resume print, pause again, switch print core from BB to AA

But frankly, this is more hassle than it is worth it so I doubt this feature would be implemented.

Alternatively you could try to print PLA on the BB core, but since it was not made for that, I don't know how well it will turn out (or if it is even possible - please don't break your print core...)

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What you can do is print the supports with PLA, and only the support interfaces with PVA.

Support interfaces are roofs and bottoms on either side of the support structure touching the print. Printing supports with PLA and support interfaces with PVA will result in small solluble bits between the supports and the model that should remove cleanly.

Use the small looking glass icon next to custom and type in "interface". Set the "Support Extruder" to Extruder 1, check "Enable support interface" and set the "Support Interface Extruder" to Extruder 2.

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TL; DR: Yes but it is a bit more complicated.

@ahoeben Yes you can! But remember the PVA material needs to be extruded a certain amount otherwise it degrades and plugs your printcore, causing your print to fail (more often anyway).

Since this is what we started with and moved away from for a reason it's worth noting.

As some portion of the PVA is hot if that volume of PVA stays hot too long the material becomes black and hard it starts becoming yellowish/brown first and then adhesion and extrusion are already worse.

This is why we cool down the unused core while the other core is printing but the current method of generating support does also grantee enough is extruded.

The ideal solution would be to know the "hot" volume of plastic in the printhead and then make sure to extrude that inside some material specific time.

Determined by the time the material is above a certain temperature for that volume of plastic.

Edited by Guest

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that might help a little bit.

the hot zone with molten material is somewhere between 21mm and 10mm I think (in an UM3)

so you need to extrude about 10-21 mm in the time it takes to degrade at the working temperature or in mm^3

((1 / 4) * pi * ((3 mm)^2)) * (21 mm) = 148.440253 mm^3

I have no idea how long it takes for PVA to be degraded, but it'd make sense to do this every layer, right?

maybe print minimally and then dump the excess material (if there is any) inside the now hollow prime and wipe tower ;)

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What you can do is print the supports with PLA, and only the support interfaces with PVA.

Support interfaces are roofs and bottoms on either side of the support structure touching the print. Printing supports with PLA and support interfaces with PVA will result in small solluble bits between the supports and the model that should remove cleanly.

Use the small looking glass icon next to custom and type in "interface". Set the "Support Extruder" to Extruder 1, check "Enable support interface" and set the "Support Interface Extruder" to Extruder 2.

Thank you this is exactly what I was looking for!

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What you can do is print the supports with PLA, and only the support interfaces with PVA.

Support interfaces are roofs and bottoms on either side of the support structure touching the print. Printing supports with PLA and support interfaces with PVA will result in small solluble bits between the supports and the model that should remove cleanly.

Use the small looking glass icon next to custom and type in "interface". Set the "Support Extruder" to Extruder 1, check "Enable support interface" and set the "Support Interface Extruder" to Extruder 2.

That is so cool! I never thought of that! Thanks!! I gotta use this as support can eat up a lot of PVA.

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