PETG supports on PLA parts, or more specifically, multi-material support structures. I am a convert, and in this video, I will hopefully make you one as well, because it's changed how I approach 3D-printing design on both dual-nozzle and single-nozzle printers. Let me explain. This shape is not ideal to print with. You can't really print on a side. So you print it face down. And regardless if you enable regular supports or just let it bridge across. Best case scenario, it's a bit rough and loses a bit of geometric accuracy. Worst-case scenario, you get some sagging. Because of that, I would just avoid designing something like this. I would try to make it more printable. Or if I had no choice, I would split it in half and glue it back together after printing. Now though, I would just enable PETG supports. And the bottom comes out amazingly clean. And it looks pretty similar to the top surface, which is pretty incredible because it's an overhang. By the way, this also works the other way around. If you're printing a PETG part, you can use PLA supports to get the same nice smooth surface. This idea of multi-material supports has made me go from trying to avoid overhangs at all costs when designing, to it's kind of all right because I know I'll get a smooth surface under certain conditions. There are limits to this. There are times it works well, times it's pretty mid. There are settings that I would tweak depending on the shape and more importantly, printers I would and wouldn't do this on. So, let's get into it.

On the molecular level, PETG and PLA are so chemically different that they don't mix even when they're molten. And it's for very similar reasons that oil and water don't mix. Now, when you turn on regular PLA supports for your PLA model, your slicer will by default, leave a tiny little gap between the support material and your print. This little gap creates a weak point that allows your supports to actually, you know, be able to be snapped off. Without this gap, your supports would be stuck to your print. However, this gap is what causes the underside surface of your print to be not that amazing. These default supports are good. They can get the job done, but they can be better. Now, because PETG and PLA don't mix, you don't need that gap. You can put your PLA layer directly onto your PETG support, and it's not going to stick. And when it comes time to remove your supports, it just kind of pops off. Well, it does stick a little bit, but that's, you know, good because we want it to, you know, stick together just enough when printing. But because there's no gap anymore, the surface you get where your part meets the support material is way better. So that's the whole logic of this video. Let's dive into actually doing it.

Now, we're going to be using Bambu Slicer because we're printing on our H2C, but I've happily done this on my P1S at home with Orca Slicer. It works just the same, so it doesn't matter what you're using. To start off with, I've got one of my test models here that we're going to call Coin. I'm going to ensure that I have my PLA and PETG filaments in my workspace here. And then I'm going to head to supports and enable it like usual. Then I'm going to go ahead and under the support interface, I'm going to select PETG. And it's going to prompt us with a whole bunch of things that it also wants to change. Just change them. It's doing the correct thing. If you're doing the opposite here and you're making your part out of PETG, you'll just need to select your PLA option instead. Now, if we take a look at the sliced model preview, you'll see that we have our coin and our supports being generated normally. And then actually PLA supports all the way up to these two layers here, which is where the PETG actually gets printed right before our part actually starts. When I say PETG supports, this is largely what I've been referring to, just having this PETG interface layer here. If we go ahead and enable advanced mode, we can also see the other settings that would change to make this work. First of all, we have our top Z distance. And this is going to be set to 0 mm because this is the gap that we were just talking about. And obviously, we want it to be nothing. Very important setting there. And as you can see, if we restore it back to its default value, it's actually going to try and leave that little 2 mm gap. We don't want that. Make sure it's set to zero. Then we also have interface pattern and interface spacing. Now when you normally slice supports, you know, your regular PLA supports, the top layers of those supports, the part that the actual model sits on is not completely solid. Again, this is to ensure that your PLA support doesn't stick to your PLA model. And these settings here, you know, change it to be completely solid so that our surface comes out nice and smooth.

Settings-wise, that's really it. Here is our coin. The materials pop off super easy. And as you can see, we have our part. We have that patchy interface layer. And then we also have, you know, the PLA support structure underneath it that didn't stick. None of these kind of stuck together. The first time I printed this and even now I'm kind of, you know, taken a back a little bit how cool it is to print one physical solid thing and have three completely independent parts, you know, come out of it because they just don't stick together. Comparing this to a coin that was printed with regular PLA supports, the difference is pretty night and day. and the PETG supports have just print-mogged the PLA supports in every single way. The surface looks better. It feels smoother. It's a bit more geometrically accurate. It was easier to remove. And I'm going to go out on a limb here and say that it's going to be a tiny bit stronger as well because that bottom layer is adhering to the part a lot better. Very, very minor increase in strength there. But I think that underside's going to get a lot of wear and tear. I feel like the PLA supports is going to kind of maybe string and peel a bit better though.

Now, to address the elephant in the room here, we are using a big fancy dual-nozzle printer here for our dual material print. But if you are using a single-nozzle print, this coin example doesn't actually use much more filament, nor does it increase the print times too much. We'll talk about it later, but there are objects like the coin here where this method is sort of a no-brainer even on single-nozzle machines. But how does this hold up on other shapes? Well, this is maybe where the, you know, flaws of this start to arise. We're going to call this piece Lion. It's a test of using these supports on a kind of more statue model, a situation that really commonly needs supports. And the results are fantastic. Compared to using regular PLA supports, it was so much smoother. There was less sagging. And I was just kind of blown away at how day and night the results on the underside of it were. Once again, however, if you look closely, you will see that there are some black spots of PETG stuck in our PLA part. And this was somewhat of a common occurrence. My guess is that our PETG wasn't, you know, fully dialed in. And when printing that support layer, a little blob might have formed on the top of it. And when our PLA layer goes over it, that PETG blob gets embedded in our PLA part forever. Now, when I say not fully dialed in, I actually mean that I just grabbed some wet PETG off the shelf without actually drying it like it needs to. Most of the tests that you're going to see in this video are using that wet PETG. So, there's going to be a lot of this blobbing everywhere. After later printing some more demos with, you know, properly dried PETG filament, most of these random black blobs just disappeared. So, I'm going to chalk that up to wet filament. But there were still some stray bits here from time to time with just regular print defects you might get. The important thing here is that if you have your PETG profile dialed in and it prints perfectly, you're going to be fine. But if it doesn't print very well, you're probably going to have little bits of PETG getting in your PLA. On functional prints, no biggie. But for things you really care about the color, it might be smarter to use the same color PLA and PETG just in case. Also worth knowing that when printing PETG with PLA supports the other way around, this was a lot less of an issue. My guess is that PLA just prints, you know, nicely by default, so it didn't randomly blob or string like PETG does. Also, also worth knowing, we have printed a lot of these flat surfaces like in the coin here, and not once did we get the random blobing. So again, the coin works a lot better than this. It seems that once you get into, you know, more curvy geometric shapes like this, the blobbing becomes an issue.

Just some more test pieces. We call this one here wiggly. This surface is a bit of a printer nightmare being, you know, all curvy and a lot of it being printed in midair as well. Yet again, night and day difference between the oldie support PLA method and PETG interface supports and for the exact same reasons. It was smoother. It was just easier to remove. There was less sagging. and it was just cleaner overall in terms of print quality. We also had some generic overhang tests and on the steeper overhangs of like 70 to 80°, there was a massive difference again, but there was less of a difference at the less steep overhang angles. Something to note here that was very visible in the overhang test that you know popped up from time to time. The PETG interface created almost like a bit of an elephant footing where the first layer of PLA touched the PETG. Here we got blobs of our PLA model sticking out. It wasn't anything crazy. could be easily cleaned up and only appeared in certain geometries. Just an observation. We also printed out this one that we called Archie that gave us yet again some pretty good results and even printed out a half sphere upside down which once more pretty great outcomes. In every test part that we ran that needed supports, there was a noticeable improvement in terms of surface quality, just overall print quality on the underside. Even things that we've been printing off camera, the exact same deal.

As you may have noticed, this method works better and worse on different shapes. The coin is really kind of the poster child of this entire method, and I just can't get over how incredible it is. I'd give that like a nine or 9 out of 10 surface finish on the bottom. The Wiggly and the Archie, on the other hand, yes, there is a big improvement, but I'd only give it like a six or seven out of 10 at best on that surface. The top is noticeably a lot better than the bottom, but again, there is an improvement. So, that got me thinking, could we tweak the settings to get a better result on the more curvy and organic geometries? The answer, sort of. Maybe. Yeah. I started by playing around with some support settings. And after a bunch of test prints, I found that on curvy and organic surfaces like wiggly and archy, bumping up the threshold angle from 30° to 40 or maybe even 50, as well as increasing the patchy interface layers from the default of two to four, maybe even five, got marginally better results. pretty reliably sometimes on certain geometries. Big emphasis on the marginal though. Wiggly went from maybe a seven out of 10 to a seven and a half or eight out of 10. The Lion a little bit better as well, but you've really got to look close to see the differences, but I'd probably say it also increased by, you know,.5 or one point. The simple overhang test saw not really any noticeable increases at all. Same deal for Archie as well. We didn't see any improvements there whatsoever. Interestingly though, the sphere test came out worse every time. There is too much to waffle on about why I think this is the case. So, for the sake of time, I'll put it in the written guide linked below in more depth if you want to go check out why I think this is the case and kind of when I would, you know, choose to use these expanded settings. However, long story short, tweaking the settings here like this can lead to slightly better underside surface on curvy shapes like this. But, I think we're getting well into the point of diminishing returns here. If you do mess around with them and find something that works better, please do let us know below. I also went ahead and tried some other ideas like manually modeling another shape that kisses the underside of the model and then printing that out of PETG, you know, like kind of manually modeling a solid PETG kind of thing for it to sit on. I don't know what I was doing here. I was just trying something. However, with this, I got something really, really interesting. This is the best wiggly that I could make with the regular PETG interface support method. I'm not going to be comparing this new method to the bottom. I'm going to be comparing it to the top of Wiggly. As you can see, it is almost indistinguishable. There was actually a worst-case scenario than this, which was uh it made the PETG unable to be removed at all. Partially, I think that this happened because when you use support material, it can kind of bend and break away, which makes it removable. But when you print a solid block, it can't bend or move out of the way, and it kind of sticks a bit better. Also that when you print a vertical wall of PETG alongside a vertical wall of PLA, although they don't chemically stick, the layer lines create sort of a Velcro or zipper effect that mechanically holds the pieces together. Kind of like, you know, interlocking the pages of a phone book. It wasn't just this part, by the way. This is something I encountered quite often when I used too many PETG supports, even with the regular, you know, PET G interface method. If I set the overhang threshold too high or if I had some bad petgy bubbling and artifacting from wet filament, this velcro effect would make it hard to remove the supports. Just something to keep in mind if you experiment with the settings. Don't set the overhang too high and make sure your filament is, you know, nice and dry. For my final test, I went through and changed not only the interface layer, but the support structure to be made of PETG as well. And again, I didn't really get any better results. I don't see why this would have produced better results. It's just printing the support out of PLA instead of PETG. If anything, it was a bit more of a hassle as you were trying to print PETG and PLA on the same print bed. Luckily, on a textured PEI sheet, the max temp of PLA is about 60° and the minimum temp of PETG is about 60° as well. So, if you adjust your filament settings, this can work. But again, this is just extra effort to get pretty much the same results. I will say, however, it did make it a bit easier to remove supports on the coin structure. Very niche case there, though.

All right, let's round this up and interpret the results and what they actually mean for our workflows. First of all, the coin, our poster child here. If your part has a flat overhang surface that is perfectly parallel to the bed, like in the coin or the underside of the letter H or in the letter T, PETG supports is a no-brainer, even on a single nozzle printer. On this flat overhang, there's only two layers of PETG being printed here. So, the nozzle only has to do a filament swap twice. On top of that, if I went home and printed this exact thing on my single-nozzle P1S printer at home, the Prime Tower and the poop ejections out the back would only waste an extra 2.5 g of filament, which is nothing. And in terms of total print time, this PETG interface only adds 8 minutes of extra printing time. Those numbers, by the way, are compared to printing it with regular supports. We're just saying, is it worth upgrading to PETG supports instead of, you know, regular PLA supports even on a single nozzle printer, as long as you have a multi-material solution like an AMS, that is not much extra to get an incredibly clean underside. Because of that, I don't really stress about having these flat parallel overhangs anymore. Yeah, I will avoid them if it's an easy fix, but if I have a part with this feature that needs supports, it's not the end of the world because I'm pretty confident that the supports will give me a nice surface quality similar to the top side. If I was planning to make like two or 300 of these, I might try and eliminate the need for support structures altogether. But for regular printed parts that are, you know, one-off things, it's not a thing that I try and avoid as much. Curved surfaces, on the other hand, well, this is where you got to decide based on your printer, is it worth it? First of all, as we saw, the quality was greatly improved again, but not as amazing as the coin. There is a more noticeable difference between the top and bottom surfaces of Wiggly and the Lion compared to the coin. On top of that, trying to use patchy supports on a shape like this on a single-nozzle printer. You can expect anywhere between a 30% increase in print time to even a doubling or even a tripling, depending on what you're printing. Again, that is compared to just using regular PLA supports. By the way, on top of that, you are wasting a lot more material with the nozzle needing to be purged all the time as there's so many PETG layers that it has to put down. So on a single nozzle printer, you'd probably be weighing out whether you know, ye oldie PLA supports is worth it, saving the material or using a bit more to get clean results with PETGY interface. You know, it depends how badly you really want that nice underside surface. Dual nozzle printers, on the other hand, well, it doesn't really matter. You have two nozzles and you're printing two materials. It's going to take roughly the same amount of time and material. You might as well do it. To me, on a machine like the H2C or H2D, PTI interface support layers are a bit of a no-brainer regardless of the shape. I'm probably going to be turning them on by default anytime I turn on supports. It's an almost free upgrade in underside surface quality at the cost of having some PET G and PLA loaded into the machine at the same time and also a Prime tower that weighs a few grams that'll go into the bin. It's nothing for free improvement at home. I'm also looking to upgrade my P1S and I'm unsure what to get, but this has been one of the biggest cases to get a mid-range dual nozzle printer like the X2D, which is a beefed-up P2S with a second nozzle designed for support material. I am so on the PETG interface support train that it's kind of worth it getting that extra nozzle regardless. I I I I can't live without it now. So, I hope I've convinced you. If you have a dual-nozzle printer, this is basically a single button press to get greatly improved supports. And if you're like me and only have a single-nozzle printer at home, it's again pretty worthwhile if you have a flat thing like the coin. More curved geometric surfaces on the other hand, h maybe not. Depends how really badly you want that nice surface. If you find a way to get even better results with this multi-material support method, or you just have a question about something from this video, feel free to head on over to our community forums and post about it. We're all makers over there. Until next time though, happy making