PETG as a support interface layer for PLA
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I am trying to use PETG as an interface layer in a PLA print but not having much success. When the PETG is laid down on the PLA, it just barely sticks when it is going onto a solid surface. Some of the extrusion sticks, some doesn't. When the second layer of PETG interface goes down it sticks to the first layer of PETG. When I try putting PETG on top of a support structure, there is no sticking at all - probably because the support structure is not a solid surface. The filament just kind of curls around the nozzle.
I am using 230C for the extrusion temperature and was expecting the much higher nozzle temperature compared to PLA (205C) to actually stick too much but that is not what is happening.
If you use PETG for your separation layer on support for a PLA print, what are your settings to get enough (but not too much) sticking of the PETG to the PLA?
I want to use the PETG on the separation layer as this should (at least in theory) speed up the print substantially.
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@jens55 When I was experimenting with multi material hot ends, I found that there are very few combinations of filament that will actually stick to each other. I don't recall if PLA / PET-G was one of them but I suspect it was. That's the main reason I gave up on multi material printing.
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@deckingman, I actually tried this when I got my Jubilee printer many moons ago and the verdict was that it worked perfectly although at the time I was likely not trying to just print the interface layer. Everything I have read on the internet says this should work.
I suppose it could be the particular filament I am using. I tried printing the PETG at 250C and it went a bit better on the interface between the PLA and the support on the bottom but when it got to the top of the support (which was PLA) it didn't stick at all. Besides the particular filaments somehow being incompatible, There are two more possible reasons I can think of. Filament not dry (both the PETG and the PLA are in the dryer for the next 8 or so hours) and the fact that the bottom interface layer is printed onto solid PLA and the top interface layer being printed on a support structure with much less contact.
I tried to see if PrusaSlicer has the ability to make the support denser before the interface layer but didn't find a way to do that.
The only other thing I could try is to print the entire support structure in PETG rather than just the interface layer. That way the problem of PETG adhering to a PLA support structure doesn't exist. I could also try and make the support structure really dense to give the PETG more surface area to stick to.
I had to stop for the night as it was bugging the hell out of me.I do have an unopened roll of break-away filament that I could try tomorrow .....
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@jens55 said in PETG as a support interface layer for PLA:
@deckingman, ,,...,........Everything I have read on the internet says this should work. . ........ .
Oh, well if it's on the internet, then it must be true.
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@deckingman .... of course! It also helps that at one time it worked for me
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While I can't yet speak for the PETG and PLA support issue, I have found a glaring problem in my configuration. In PS, there is a setting for extrusion width for support which I had set at 100%. I think that other people have fallen into this trap - that percentage is based on layer height and not nozzle diameter (what where they thinking?). I was laying down 0.2 mm worth of filament for a 0.4 mm nozzle:(
I also had a fairly big support pattern spacing of 3 mm which probably didn't help.
I will start all my tests from the beginning and hopefully the corrected settings will show a completely different picture.
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I have got PLA / PETG printing working, the trick is to make sure the interface layer is 100% dense, and to slow down the print speed of that interface layer so it gets a better chance of adhering, and lastly to increase the support density overall, as more surface for the PETG to stick to massively improves reliability.
If you are using a Bambu machine (or similar one hot end multimaterial) then you MUST purge more filament than you expect, and once you have a value you are happy with, DOUBLE IT. Any PETG contamination will compromise the structural strength of the print, as PLA on PLA layers will refuse to stick to each other.
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@Notepad, thanks for those tips!. I had a 0.2 mm spacing on my interface layer which I changed to 0 spacing or 100% . My support pattern spacing was 1 mm which should be good but I started at 3 mm which was way too much. My interface layer print speed is 40 mm/sec.
What do you use for a z spacing for the interface layer? I had some issues removing the interface layer when the spacing was zero. I am currently printing with a 0.1 mm spacing. -
@jens55 said in PETG as a support interface layer for PLA:
z spacing for the interface layer
I personally use 0 as PETg with PLA or vice versa will separate extremely easy. But only do that if you are having a 100% dense top layer as you dont want the filament to grip between the strands
The real bamboo printer manufacturer
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I am mostly there .... The PLA and bottom of the PETG interface layer separate nicely but I am unable to remove what I think is the interface layer itself (from the PLA that overlays it). At this point I don't know if I am seeing this correctly or not. I can't determine clearly what is the interface layer and what is the model.
More experimenting is needed. -
@Notepad, may I ask what you are using for print speed for your separation layer and also what you are using for support density? Also, do you use normal printing temperatures for the PETG or do you print the separation layer at a nozzle temperature different from a normal PETG print?
This is problem is driving me nuts ... I have a model that has two areas of support at slightly different heights. The support is PLA and the separation layer is PETG. The support is a single area but there are two distinct separation layers at different heights (think of it as stair steps) The lower separation layer prints perfectly fine if I use three separation layers (the first one barely sticks but the second layer sticks to the bits that were left over from the first layer) but the upper layer will not stick at all. The PETG just wraps itself around the nozzle and nothing sticks to the support structure. The support structure is exactly the same in both cases with a 1 mm pattern separation which seems pretty dense to me (also tried 0.5 mm spacing). In about 4 separate trials, the first separation layer has always printed and the second, slightly higher separation layer has never printed (well it prints but the PETG doesn't stick to the PLA support structure).
I normally print my PETG at 230C but I also tried 245C.
To be clear, if I make the entire support structure PETG, it prints just fine but of course you have a TON of filament changes. If I only print the separation layer in PETG then there are hardly any tool changes (depending on the model of course)
If I go any denser than a 0.5 mm spacing it will likely be very difficult to remove the supports.
I believe Cura allows for a variable density where support density is low but then goes very dense just prior to the separation layer. I could not find anything like that in PS. -
@jens55 said in PETG as a support interface layer for PLA:
e using for print speed for your separation layer and also what you are using for support density? Also, do you use normal printing temperatures for the PETG or do you print the separation layer at a nozzle temperature different from a normal PETG prin
- I use a raised temperature of 260°C for the PETG and a regular 225°C for the PLA.
- The interface print speed is at 60mm/s.
- Z-Top distance is set to zero.
- Support density is set to 2.5mm
- Top interface spacing is set to 0.00
- Bridge print speed set to 40mm/s
@jens55 said in PETG as a support interface layer for PLA:
I believe Cura allows for a variable density where support density is low but then goes very dense just prior to the separation layer. I could not find anything like that in PS.
Yes, this is unique to Cura, and generally crashes (at least for me) when I try to use it on more complex parts.
I generally find printing PETG at higher temperatures helps drastically. Also make sure the nozzle is clean as PETg loves to stick to itself.
If you want, send over some pictures as there might be some other aspects causing the failiures
