Severe PC-Blend Warping on Massive Part (CoreOne) – Hardware Limit or Slicer Issue?
Hi everyone,
I’m currently printing a rather massive filter cassette on my Prusa CoreOne using unfilled Prusament PC-Blend. Despite a lot of preparation and a solid first layer, the part warped so aggressively during the print/cooling phase that it formed a severe "banana shape" at the bottom and even deformed an internal hole meant for a heat-set insert due to internal shrinkage stresses.
Before I surrender and switch to PC-Blend CF, I wanted to get a sanity check from the experienced PC-Blend users here to see if there is any slicer trick left to save this.
The Setup & Preparation:
Printer: Prusa CoreOne (closed doors/lid, exhaust fan blocked to maximize chamber temp).
Filament: Prusament PC-Blend (unfilled). Dried for 7 hours at 65 °C in a SpacePi filament dryer and printed directly out of the active dryer.
Build Plate: Satin Sheet with a thin, dried layer of PVP glue stick (UHU).
Temperatures: * Nozzle: 275 °C
Bed: 115 °C
Chamber: Maintained a constant 55 °C after the first layer (thanks to heat soaking and hotend thermal mass).
Cooling (Post-Print): I attempted an "annealing/slow cool-down" after the print finished by leaving the bed at 75 °C for 30 minutes before letting it cool completely.
Slicer Settings (PrusaSlicer):
Brim: 10 mm
Infill: 15% Gyroid (to minimize directional stress)
Part Cooling Fan: 0%
Chamber Fan: Set to auto (barely engaged).
Perimeters: Arachne engine active.
The Symptoms: The first layer adhesion was actually fantastic. The part stuck to the glue/sheet perfectly at the beginning. However, the massive thermal mass of the thick walls and infill seemed to overpower the adhesion over time, lifting the corners and warping the internal geometry. I suspect the part mainly warped during the cool-down phase, because the top layer looks great and is quite flat.
My Questions:
Is a massive part like this simply hitting the physical limits of unfilled PC-Blend on a passively heated printer (even at 55 °C chamber temp)?
Would switching to PC-Blend CF completely eliminate this specific issue due to the carbon fibers counteracting the shrinkage?
Are there any hidden slicer tricks (e.g., asymmetric infill angles, specific extrusion width tweaks for the first layers) to relieve internal stresses before giving up on the unfilled material?
I have attached pictures of the warped bottom and the squeezed heat-insert hole. Any advice is highly appreciated!
Best Answer by hyiger:
To answer your specific question: "Is a massive part like this simply hitting the physical limits of unfilled PC-Blend on a passively heated printer (even at 55 °C chamber temp)?"
For materials like PC and ABS/ASA they shrink a lot when they cool. You can compensate for this in the slicer. The problem with PC in particular is that the shrinkage isn't even. The bottom layers have already cooled (a 110-120° plate is well below PC's glass transition temperature) and shrunk by the time the upper layers are being deposited. The stress builds up and the plastic starts to curl upward as you have observed. You see this in the corners first because that is where it's getting pulled the hardest. And the larger the part, the more curling force.
The single biggest fix for this is to have the chamber as warm as you can make it. On a Core One it's between 55-60° but not with the current firmware which tops the chamber at 55° and then aggressively cuts on the chamber fans... Next is to get a strong adhesive but then you run into problems on a spring steel sheet like the statin where it can actually curl the build plate off of the bed which is why G10 on a rigid and not spring steel plate will help. Regardless, on a part like this you will still get some curling but not as severe. Even if you can control this, PC for a part like this is overkill. You will probably be successful printing this in PC-CF but that is also not only overkill again but expensive.
PETG is the right choice here. If you want to be adventurous and try something new, PCTG is a better alternative to PETG in my experience.
If you do go the G10 route, do not print ABA or ASA on it with adhesive. If you do the part will weld itself to the sheet. You won't damage the sheet (they are very robust) however you will need to get acetone involved to destructively remove the part. Will stick fine without an adhesive. Same with TPU, it's sticks too well.
I own 3 sheets. Don't be tempted to buy the Prusa PA and PP specific build plates. In my opinion they are a waste of money. They work, just not necessary.
- G10 - PC, PA, PPA, ASA (without glue), PP (PP based adhesive is required), POM (need to scuff the sheet first)
- BIQU CryoGrip Glacier - PLA, PETG, PCTG, ASA, PA and PC (smaller parts)
- Generic Textured Plate - TPU
I can't recommend the CryoGrip Glacier enough as a general purpose build surface. I use it on all my printers.
RE: Severe PC-Blend Warping on Massive Part (CoreOne) – Hardware Limit or Slicer Issue?
Hi florima,
I saw your post here and while I'm new to 3D printing and have no experience with PC filament myself I took a look around on the Prusa website and found this blog article. Based on your description you followed most of the recommendations from that blog post. You mention however that your rely on the Arachne Engine for perimeters. The blog post mentions the following:
With denser infills and generally more material inside the object, the higher the risk of warping – this causes the object to detach from the print sheet. If you print something large, you can consider lowering the number of perimeters (if it doesn’t affect the desired result).
Your infill density seems to be pretty low already but maybe Arachne generates too many perimeters? Can you manually adjust the number of perimeters to a low value?
Also looking at your last picture it seems that the bend is along the longest side of the model. If I understand your description correctly the top side on the last picture was the bottom on the print bed. Due to that orientation you have extremely long filament layer lines because the print head moves parallel to the longest side of the model. Maybe if the print height permits it you can rotate the model by 90° and use the left side on your last picture as bottom. Perhaps you get better results with that orientation, because the filament layer lines run orthogonal to the model's longest side. I'd expect shorter layer lines to warp less. The downside is that you'll have less bed adhesion in this orientation, so a sufficiently large brim might help.
RE: Severe PC-Blend Warping on Massive Part (CoreOne) – Hardware Limit or Slicer Issue?
Hi Matt, thank you for your input and for taking the time to look into this!
Well, I tried to follow everything I could find on the internet to make this print happen. This failed attempt cost about 15€, which sucks a little bit 🥲
Your reasoning totally makes sense, but there are a few issues with that approach:
- When printing in the Z-direction, the parts become mechanically much weaker.
- When printing the longest side in the Z-direction, there is way less contact area with the heated bed. If I'm correct, PC-Blend tends to shrink heavily when the temperature drops from 110°C down to 90°C. So rotating the model wouldn't be ideal in my opinion.
Also, as I mentioned in my post, the top layer is actually perfectly flat. This strongly indicates that the model warped right after the print finished, while the part was equalizing to room temperature. Otherwise, the good quality of the top layers wouldn't be explainable 🤔.
I've also attached the G-code file so everyone can take a closer look at the model🤓. As you will see, the walls actually only consist of 3 perimeters (except for the bottom and top flanges). Given the sheer thermal mass of the base, I highly doubt that reducing the perimeters in that specific area would be enough to tame the warping.
RE:
For large PC-Blend parts, I use a Garolite G10 plate with Vision Miner Nano Polymer adhesive. The backing plate is rigid steel so the plate doesn't get pulled off the bed when the part cools. The chamber should be > 55° which is not possible with the current 6.5.3 firmware. You should downgrade to 6.4.0 and insulate the top of the chamber with a blanket.
Do you need the heat deflection of the PC or would ASA work? I would also recommend switching to PC-CF or PET-CF. PC Blend is the wrong material for large rectangular prints.
RE: Severe PC-Blend Warping on Massive Part (CoreOne) – Hardware Limit or Slicer Issue?
I opened the g-code. This is too large to print on a Core One with PC-Blend. You might get lucky with G10 but not on a satin plate.
RE: Severe PC-Blend Warping on Massive Part (CoreOne) – Hardware Limit or Slicer Issue?
Hi hygier, and a big thank you for your guidance!
This part is meant to be the housing for a custom filtration system for my CoreOne. I originally chose PC-Blend because I wanted a durable, long-lasting housing that could withstand high temperatures. Since I plan to print a lot of ABS, ASA, and other technical filaments in the future, I figured PC-Blend would give me plenty of thermal headroom.
Turns out, it was definitely overkill on my part! 😅
After this failure, I've decided to pivot to PETG just to get the filter up and running. I figure my chamber temperature won't hit the 80 °C mark anyway (PETG's glass transition temperature), so it should actually hold up perfectly fine. Since you seem highly experienced with high-temp setups, I'd love to get your thoughts on one detail: How do you view the actual exhaust air temperature? Do you think the hot exhaust air passing directly through the PETG filter cassette could cause any thermal softening over time, or do you think the passive ambient cooling on the outside of the cassette is sufficient?
I will definitely look into your advice regarding the Garolite G10 plate and the Vision Miner adhesive. Even if I don't use it for this specific project, having that setup in the arsenal sounds incredibly useful for future high-temp endeavors!
RE:
To answer your specific question: "Is a massive part like this simply hitting the physical limits of unfilled PC-Blend on a passively heated printer (even at 55 °C chamber temp)?"
For materials like PC and ABS/ASA they shrink a lot when they cool. You can compensate for this in the slicer. The problem with PC in particular is that the shrinkage isn't even. The bottom layers have already cooled (a 110-120° plate is well below PC's glass transition temperature) and shrunk by the time the upper layers are being deposited. The stress builds up and the plastic starts to curl upward as you have observed. You see this in the corners first because that is where it's getting pulled the hardest. And the larger the part, the more curling force.
The single biggest fix for this is to have the chamber as warm as you can make it. On a Core One it's between 55-60° but not with the current firmware which tops the chamber at 55° and then aggressively cuts on the chamber fans... Next is to get a strong adhesive but then you run into problems on a spring steel sheet like the statin where it can actually curl the build plate off of the bed which is why G10 on a rigid and not spring steel plate will help. Regardless, on a part like this you will still get some curling but not as severe. Even if you can control this, PC for a part like this is overkill. You will probably be successful printing this in PC-CF but that is also not only overkill again but expensive.
PETG is the right choice here. If you want to be adventurous and try something new, PCTG is a better alternative to PETG in my experience.
If you do go the G10 route, do not print ABA or ASA on it with adhesive. If you do the part will weld itself to the sheet. You won't damage the sheet (they are very robust) however you will need to get acetone involved to destructively remove the part. Will stick fine without an adhesive. Same with TPU, it's sticks too well.
I own 3 sheets. Don't be tempted to buy the Prusa PA and PP specific build plates. In my opinion they are a waste of money. They work, just not necessary.
- G10 - PC, PA, PPA, ASA (without glue), PP (PP based adhesive is required), POM (need to scuff the sheet first)
- BIQU CryoGrip Glacier - PLA, PETG, PCTG, ASA, PA and PC (smaller parts)
- Generic Textured Plate - TPU
I can't recommend the CryoGrip Glacier enough as a general purpose build surface. I use it on all my printers.
RE: Severe PC-Blend Warping on Massive Part (CoreOne) – Hardware Limit or Slicer Issue?
FWIW, I built filtration ducting for the back of my Core One using plain black PETG, no CF. I think there's zero chance of the rear plate or the exiting air ever hitting a temperature that will bother it, assuming you don't modify the printer for extra high temperatures.
RE:
How do you view the actual exhaust air temperature? Do you think the hot exhaust air passing directly through the PETG filter cassette could cause any thermal softening over time, or do you think the passive ambient cooling on the outside of the cassette is sufficient?
Sorry, realized in my long-winded answer above I never really answered your question. As long as the chamber temperature doesn't go above 55° (which with the newer firmware it can't) then PETG is fine. If you were to bypass this and run the chamber higher at close to 60° then PETG on a long print could possibly start to soften.
The problem again though is this a print that covers almost the entire build plate. So even with PETG and PCTG since they are also amorphous you will get the corners curling on a print like this if you don't glue it down but not as aggressively as PC-Blend.
So again, I think PETG is good enough if you take care to use an adhesive with it. If you want a cleaner print with better heat tolerance then a good choice would be PET-GF or PET-CF. PET-GF is a fun choice because there are other colors available beyond just black. Also the GF variants are slightly cheaper and since this part doesn't carry any load you don't need the stiffness that carbon fiber provides.
RE: Severe PC-Blend Warping on Massive Part (CoreOne) – Hardware Limit or Slicer Issue?
Dude hygier, I'm really glad to have met someone like you on this forum!
First of all – thank you so much for your time! I truly appreciate your "long-winded" answers. I got a ton of inspiration from them and definitely learned a lot today. Everything you wrote is going straight into my notes!
And also, a big thanks to Conrad for your assessment.
RE: Severe PC-Blend Warping on Massive Part (CoreOne) – Hardware Limit or Slicer Issue?
In extreme cases, where the PC/PA model is very large, there’s no need to use custom plates with a rigid steel sheet, You can prevent the plate from curling upwards with the model just installing steel clamps on the four corners of the bed. Those for securing mantelpieces outdoors work fine, they’re flat on the top side, so they don’t interfere with the printhead movements. Wait until the bed mesh is complete, pause the print, fix the steel clamps on the bed and resume the print job. There’s of course a small area around the corners where you can’t print but it’s a small price to pay.
Nowadays I don’t print huge parts in PC, but I used those clamps on my MK3S time ago.
RE: Severe PC-Blend Warping on Massive Part (CoreOne) – Hardware Limit or Slicer Issue?
@artur5 that is generally sound advice and what I used to do on my MK4. Problem with the core one is there is not a lot of room to attach clamps, especially in the back. If you plan to print large PC and ASA parts then I think the G10 on a rigid plate is a good choice, albeit an expensive one.
RE: Severe PC-Blend Warping on Massive Part (CoreOne) – Hardware Limit or Slicer Issue?
I don't own a Core One, so I didn't realize that the room inside was so tight. Anyway, I'm surprised that you can't attach even this kind of clamps. They only need a few millimeters of space on the sides of the bed to fix them. See below, my Voron 2.4,
RE: Severe PC-Blend Warping on Massive Part (CoreOne) – Hardware Limit or Slicer Issue?
I don't own a Core One, so I didn't realize that the room inside was so tight. Anyway, I'm surprised that you can't attach even this kind of clamps. They only need a few millimeters of space on the sides of the bed to fix them. See below, my Voron 2.4,
The back left corner is problematic since the side panel and head bed cable get in the way. I thought about clamping in my case but the G10 surface itself is superior in general for engineering plastics so it just made sense (in my case) to get a dedicated build plate with a rigid steel backing.