PEI spring sheet lifting off the print bed
I'm having a really tough time printing PETG with my MK3 due to the spring sheet warping when the heated bed is set to PETG temps. The whole sheet lifts in the middle, like the edges are contracting and pulling in tight. The print will start well, but once the sheet lifts, the print head starts to rub into the already extruded plastic and on the PEI. Just to be clear, it's the entire spring sheet that lifts, and not the PEI sheet on top of the spring sheet.
Is there any way to keep the sheet lying flat at high temperatures?
I'm sorry if this is a common issue or has been answered before, but I haven't been able to find anything in the forums.
Thanks for the help,
Erik
Re: PEI spring sheet lifting off the print bed
I almost only print with PETG and never had issues with the the spring sheet lifting off the bed (magnets). PETG has very little warping - maybe the problem is somewhere else.
What temperature is the hot bed set for? Do you have a photo showing the problem?
What filament are you using (I use Prusa and Devil Design PETG)?
Have a look at my models on Printables.com 😉
Re: PEI spring sheet lifting off the print bed
You could check the temperature variations across the sheet. It almost sounds as if it is hotter in the middle than at the edges or not heating at all.
A second thing to check is that the magnets on the heatbed are all firmly in place.
Regards,
Martin
Martin Wolfe
Re: PEI spring sheet lifting off the print bed
I'll try to snap a photo when it happens again. The PETG parts that I've printed so far have had some warp to them due to this issue, even though everything that I've read says that PETG has virtually no warp. I stopped printing with PETG for quite a while due to frustration, but am determined to get through it and at least print out replacement parts for the printer.
I switched from slic3r to simplify3d this week and have been trying out some of the advanced control over temperature and speed. I set the first layer to print at 25% speed, and slightly cooler than the other layers. So far I've printed out the fan hood successfully, but had a failed print with the extruder parts.
The successful print was with Hatchbox PETG, and now I am trying eSun for the extruder.
I am currently experimenting with:
Layer: .2 (.3 for first layer) at 30% speed
Bed: 85deg (80 for first layer)
Extruder: 240deg (230 for first layer)
I am now sure it's not an issue with the sheet or the printer, but with my settings. I'm surprised at how much tweaking PETG has taken compared to PLA, which printed pretty darn well with the default slic3r settings.
Re: PEI spring sheet lifting off the print bed
The surface temperature when set to 85 varies from 45 on the edges to 75 at the center, when measured with an IR thermometer. But I don't think that gradient is surprising with the heater being at the center of the bed.
Re: PEI spring sheet lifting off the print bed
The heater is throughout the bed surface area. That is your problem. The only bit localised to the centre is the thermistor. Contact Prusa support via chat and have a video of you taking those temperature readings to hand.
Regards,
Martin
Martin Wolfe
Re: PEI spring sheet lifting off the print bed
Hi Erik,
the heating on the print bed is supposed to be Distributed across the surface, with hotter areas towards the periphery.
as you can see in this image, the outer tracks are thicker than the inner tracks, so they should get hotter.
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Re: PEI spring sheet lifting off the print bed
Doh! And here I thought I was just slow at getting the settings right to get large prints that didn't warp.
I've contacted support and they are sending a replacement. I'm glad I finally decided to check in here for help 🙂