First Layer Issues  

The best place to seek help with new-builds (and new pre-built machines) is Prusa Suport via chat.

You will need your machine's serial number.

Cheerio,

RE: First Layer Issues

It shouldn't be a not-level bed because the Prusa's pre-print routine includes checking the bed level at several points in the print area.  It then uses the data it's gathered to compensate for variations in bed level while printing.  Are you using LW-PLA?  If so, it may simply be that your nozzle temperature is inadequate and/or your flow rate needs adjusting in your slicer.

RE: First Layer Issues

Thank you @abenn. I am using Jessie PLA 1.75, not any LW-PLA. I have chatted with Prusa support and they've asked me all sort of things that check out okay. I have gone so far as to loosen the rail, push down and re-tighten, swap out the nozzle with my MK4S nozzle, re-calibrate the gear box, make sure the idler screws are correctly tensioned, etc. I still get a the issue where part of the first layer (always the same area of the bed) is not solid (see attached pics). The nozzle temp seems accurate. If I increase the flow rate it seemed to help and then failed horrible on repeated tests. It's also doing this will different PLA filament brands so it's not related to just one roll. Tonight I tried moving the Z offset closer to the bed by adjusting it -.025 and it seemed to do the trick. Do you know if this setting is retained for all future prints even if the printer is turned off? I'd like to make it a permanent setting.  Thank you.

Flip the print sheet - does the result repeat on the other side?

Cheerio,

RE: First Layer Issues

Thank you @Diem. I'm using my textured sheet and I did flip it over and even tried my textured sheet from my MK4S resulting in the same issue. If I do a live z adjust of -.025 it seems to help, but the printer is NOT remembering the offset if I print again and/or turn off the printer and print again. Isn't the Core One+ supposed to remember this? Not sure if I should do a factory reset and do all calibrations again or just put that offset into Prusa slicer under Printers -> Size and coordinates -> Z offset. At this point I don't know what's wrong with the printer.

Keep working with support; don't change many slicer values unless they suggest it (it confuses the results) - and make sure to tell them you tried flipping.

Cheerio,

RE: First Layer Issues

Thank you again @Diem. I just got off chat with them and even though I am printing this particular project on my textured sheet with PLA, they wanted me to try the smooth PEI sheet. I did and the first layer test came out perfect. The textured sheet works, but I have to have more "squish" and my lowering of the z offset by -.025 basically resolves that issue. Still interesting how part of the first layer is fine and consistently another part is not. Wish I could adjust the offset for the first layer ONLY and not the entire print. I don't believe Prusa slicer has an option for that (unless I've missed it) and changing the extrusion width didn't really help. 

I want to use the textured sheet on this project because it's a nicer finish than the smooth for what I'm making. I ordered a satin sheet which supposedly works better with PLA and also has a fine texture, so not sure if that will work well. Mostly I'm hoping I didn't mess up my printer build by loosening and retightening things like my linear rail, heat bed, etc. with all the troubleshooting. Thanks again to everyone for the help. Kind regards

RE: First Layer Issues

Create a new printer set the z offset.

RE: First Layer Issues

Did you start with the smooth and move to the textured?  Each sheet needs a new Z offset.