I’m printing a flat (horizontal) area in an elevated position, so it needs support from below.
I am printing PLA, and use PETG as the support layer.
The problem is that when I separate the support structure from the print, the PETG always sticks to the model and not to the support structure, and then it’s very difficult to get off. This all started when I ran into some other trouble with the support, where the first layer after the PETG layer wasn’t sticking, see here.
So I found the setting to change the printing angle for a layer, and set that to 45 deg especially for that first layer on top of the PETG layer (and that works, and that layer now prints nicely).
But they now stick together like glue. The change in print direction did not cause this because it also happens at another layer where I didn’t mess with the print angle.
But I modified some other settings as well, and now it’s difficult to retrace what may have caused this.
I have already tried increasing the “Top interface spacing” but that made matters worse, because then the PLA layer practically dug into the grooves of the PETG layer, making it stick more.
As an engineer, I know I can just gradually change the settings and make test prints, but I’m a bit short on time and also like to understand what’s going on and not just “monkey do”.
Here’s my support settings:
I suspect that the general advice of “use petg as interface” is too broad to be useful, given the wild and nonstandard number of formulations of pla and petg out there.
The few times I’ve tried gave me similar results as you, fused when done at 0 height, or a spaghetti factory from it rolling off the interface. I think the community could help by giving strong examples of “This vendor formula pla + this vendor formula petg = working 0 gap interfaces”
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Well, thanks for confirming the issue isn’t just me 
I’ll try the Bambu “Support for PLA” for the next print - I just had a major clog in the extruder for the first time - of course very close to the 4h print being finished. After fixing the issue, I let the printer continue but it then printer a few layers too high into air. But that print already had a very sticky PETG layer as well. I’ll have to redo the print and will try the Support instead to see if that’s better.
Exciting stuff (both positive and negative)!
One solution is to make the entire support out of one material. the support will stick to the support better than the model.
But, it might increase the print time. It depends on the geometry. Comparing an overhang that has just one layer of interface. causes one poop. But a ramp causes a pair of poops for each layer. So making the entire support does not save poop.
Another solution is to model the Support. Then add some interlocks to mechanically hold the interface to the base of the support. Takes time but depending how much time is saved it might be worth it. Another advantage to modeling the support is it can be optimized for a faster print.
