I’ve recently changed the PEI sheet on the print bed of my Mini. This is the second time I’ve changed the PEI sheet. The first time everything was well and the printer produced great prints.
This time around I’ve had a lot of issues with layer 1 not adhering to the PEI in some places.
This print is a single layer covering the entire printable area allowing for the skirt. You can clearly see the parts where the ABS has not adhered to the print bed. I adjusted the z offset and that allows more of the plastic to be laid down in the lower left empty area but it means the skirt on the right hand side doesn’t get print properly as the lines don’t merge.
So I suspect there are lumps in the lower left that the nozzle is hitting as it passes over which is stopping the plastic from extruding from the head.
Can someone tell me if I’ve just put the new PEI sheet on incorrectly? Or is it something worse like a warped print bed?
It’s not likely the bed would be bent, and a well tuned Z-Offset would take care of imperfections in the PEI. The Z-Offset looks too low from the image you’ve shared. The layers appear to be smeared together. The below image from LulzBot shows a well configured Z-Offset (middle shot) and two extremes either side.
Note there are definable edges on the middle shot. The short story is: set the Z-Offset to the point where the first layer extrusions are “joined” (no gaps, stay connected when removed from the bed). Avoid smearing - you are left with no elbow room for imperfections on your print surface.
Yes, it would be best to slice again given you are using the LulzBot Mini and that setting is defined in Cura’s machine settings page. Just FYI (in case someone in the future is reading this and is interested) - if it were a TAZ 3D Printer then it would be managed on the actual device (within the printers own menu system) and Gcode does not need to be regenerated.
So I’ve tried to find a z offset which doesn’t smear the print and prints in the “high” area of the print bed while staying fused in the “low” areas and I have not been entirely successful.
At about 0.1mm z offset I still have an area in the front left where the nozzle touches the surface and leaves no filament while at the same time on the right hand side of the print surface the lines of filament don’t fuse together properly. Obviously at greater z offsets the situation improves on the left while deteriorating on the right and vice versa for smaller offsets…
So I’m left with about 25% of the print area towards the front of the print bed that is unusable for printing.
I’ve tried to gently scrape the “high” area down and that has helped but I’m now at the point where the PEI surface has been scraped away completely in a small spot and the underlying adhesive exposed.
So I’m resigned to having to replace this PEI sheet now as I don’t think there is any point persisting with it.
Thanks for reporting back. Given you have removed PEI down to the borosilicate glass, something is up with that corner of the heatbed. We do have replacement LulzBot heatbed kits, although, I note the date that you purchased your LulzBot and it would be worth getting in touch with support@lulzbot.com to see if they would cover this by warranty. Everything you have done in this forum topic will certainly help to copy+paste some replies. Their tech support team is available almost 24/7, so expect a reply within the day.
Ok, so I now know what the problem is/was. And naturally it was user error.
I got the new print bed on Tuesday and installed it into the printer yesterday. First print run on the brand new bed with factory installed PEI sheet gave exactly the same problem at which point I realised it couldn’t possibly be anything to do with the print bed.
After some poking around and watching the print bed more closely I found that the bed was being lifted at that one specific spot on the y axis. From there is was easy to figure out something was jammed underneath the cable carrier. Turns out to be a smallish black piece left over from a previous print. Why I didn’t see it earlier is because it blended perfectly with the chassis and cable carrier…
Mea Culpa.
I hope someone else learns from this and doesn’t have to go through the expensive process I’ve just been through.
Dan! It sucks to hear about the runaround. It sounds like you’ve hit that one-in-a-million edge-case
Thanks for documenting your experience in the forum though. Fouling of the bed-travel is definitely something we’ll add to our own troubleshooting list.
