Mixing PLA with PETG: PrusaSlicer multi-material interlocking

[Zoips]

In episode 575, Toby questioned the mechanical integrity of prints mixing PLA with PETG. I'm just wondering what folks are thinking about Prusa's new feature in V 2.9.2 of PrusaSlicer.

"Bond any filaments with multi-material interlocking!
PrusaSlicer can now interlock neighboring parts made from different materials, creating a cross-hatching boundary between them. This creates a bond for filaments that don’t usually stick together, such as PLA, PETG, and FLEX, greatly simplifying the process of printing on multi-extruder printers like Prusa XL."

https://files.prusa3d.com/?latest=slicer-stable&lng=en

[3D Printing Tips and Tricks]

You want an opinion? Ok…

It’s yet another solution for a non problem.

Simply use materials that bond together in the first place.

[Sophie]

I can see this being useful 

I've actually already printed an idea like this for an outdoor frisbee I needed for camping!

Made it out of TPU and PLA and the two areas were hatched together to ensure a good bond

Credit to the designer - Eternity Labs (They make some pretty cool stuff by the way might be good for a thing of the week here and there) Link to their Frisbee

 

[Sophie]

I meant interlocked - not "hatched" in this case

[Kurt Gluck]

Cool

[Kurt The 3D Printer GUY!!]

Hey Sophie - I really LOVED the pics for the Interlocking for the Frisbee design - that is pretty Damn SWEET!!!!!

You're using 2 nozzles to print the 2 materials. At least I suspect that is indeed what you're doing!

But, yeah - just seeing how it interlocks the 2 diverse filaments together - is really, really WILD!

However, I do have to ask. I'd like to know a little more about why those 2 different materials to begin with? Why not both of them being TPU (but, yeah - 2 different colors of TPU)???

 -K 

On Saturday, September 6, 2025 at 6:33:18 PM UTC-4 Sophie wrote:

[3D Printing Tips and Tricks]

I've never had an issue with TPU and PLA not bonding. I've used TPU for hinges and all sorts of other things without needing a mechanical interface beyond the two materials simply fusing.

Here's an example of something I printed way back when I first got my E3D Toolchanger that intermixes TPU with PLA:

https://www.thingiverse.com/thing:3515796

[Kurt The 3D Printer GUY!!]

Yeah Andy - I do Indeed remember you posting about printing the Chest piece - and that was pretty cool. 

Although, now I'm surprised by your comment of TPU/PLA fusing together. Since, recently, someone posted a video a dude did - with PLA as supports for TPU - and they came apart easily - but, stuck together well enough that the print worked Great! It was a kind of Bellows design that the guy did...

-K

[Bryan Eckert]

This is an "Aerobie" style disc. They came around in the 90's and had a solid core with a rubberish outer coating. Set the world record at that time for the longest throw (over a quarter mile!)

If it was all TPU it would flex too much to fly properly, it needs to be stiff. Hence the 2 materials.

https://www.aerobie.com/products/pro-ring-orange

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[Kurt The 3D Printer GUY!!]

Cool disc style!!!

-K

[3D Printing Tips and Tricks]

So you saw a post where someone used PLA for supports which came off easy. Do you have the settings for that print? How do you know that there was 0 space between the materials?
In my experience the two materials bond well. To me it is not hearsay, it’s objective evidence.

[Bryan Eckert]

AFAIK you just use standard interface distances for PLA interface supporting TPU - but the entire support structure needs to be PLA as PLA will move around when on top of TPU. 

The issue is if you are using an AMS style unit the TPU will delaminate from itself unless you flush insane amounts, really needs to be done with a toolchanger.

There's discussions about it on both Prusa forums and Bambu reddits.

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[3D Printing Tips and Tricks]

As such, they are simply using tpu as a break away support… so? what is the advantage?
I see tons of posts in the Reddit groups and on the specific forums all from relative noobs who act like they are experts.

I say… try it for yourself! Make a small square. Print half in PLA and pause it then print the rest in TPU and try to pull them apart.

[Kurt Gluck]

Since most PLA is not Pure PLA (exceptions are Printed Sold and Polar that I know about) and since all sorts of stuff is mixed into the PLA and probably lots of brands of TPU.  It is possible IMHO that results will vary as far as bonding.

For example the Printed Solid Elixer line of PLA HAS TPU mixed in so they get a nice silk shine.         Thus I would assume that Printed Solid Elixer would Bond with TPU more than other Printed Solid Pla 

Kurt-A

I have never worked with TPU so its just a guess