very inconsistent first layers on VC4
Since building my printer, I have had very inconsistent first layers, I did all the calibration and when it works, it works. But about 50% of the time it does not. I think I’ve narrowed it down to an issue with the Beacon contact and possibly some filament always being on the tip of the nozzle so the printer thinks it’s hit the bed before it actually has. I’ve attached two photos of the same G code printed, consecutively with zero changes made in between to show the difference. Is there a way to add a sequence to the start print macro where the printer will wipe the nozzle or maybe increase the temperature of the probing sequence so that the filament melts and does not trigger the beacon contact?
6 Replies
I dont remember if your printer is enclosed or not. Either way are you heat soaking it at all? What type filament and bed temperature is that print? These are massive printers and as they warm up things move around a little. It takes less <0.05mm to mess up your first layer. Two things to do is heat soak the printer by turning the bed up to your print temp like 30 minutes before you use it. I home the printer and move the z down to like 2mm and that helps it get to where it needs to be warmed up quicker. The other thing is Helge and Mikkel have been working on a twist compensation utilizing beacon. It seems to help me and others but I have not had a ton of time to play with it yet. Read up on section #5 at https://github.com/HelgeKeck/RatOS/blob/documentation_v2.1/site/docs/configuration/beacon_contact.md#5-beta-automated-beacon-scan-compensation
GitHub
RatOS/site/docs/configuration/beacon_contact.md at documentation_v2...
The preconfigured Raspberry Pi image that makes it easy to run Klipper + Moonraker + Mainsail on your printer. - HelgeKeck/RatOS
Both printed in pla, unenclosed, same position on plate, same g code, I have very low gantry twist. All of which makes me think it’s a blob on the end that’s triggering the beacon contact
Heat soaking won’t be a factor here
What bed temp? You would be surprised what even 40c will do. I have not tested on the VC4 unenclosed but on my unenclosed VC3, which is the same basics gantry setup, it changes with temp. Do a quick test. Home, z-tilt and do a height map. Leave the gantry centered but lower the z to 2mm and set the bed to what ever temp you print PLA with and let the printer sit for 30 minutes. Do another height map but do not z-tilt before you do it. Compare the two and I suspect it will be fairly different. Klippers ability to deal with height maps is pretty amazing but what it cannot deal with is changes that happens from the time the height map is taken to the time of the print. Maybe this is not your benchy problem but when you start trying to print something with a large first layer you will most likely run into it.
Both Benchys are printed in the center of the bed, so it's not a height map issue, as the bed is probed at the start of each print. The problem is definitely with the nozzle when bits of filament hanging out trigger the beacon contact. If I manually clean the nozzle before each print, I get a perfect first layer.
What I'm looking for is a way for the printer to either raise the nozzle temperature while performing the beacon contact to determine the correct Z-height at the start of a print, so any filament on the tip melts. Alternatively, I can design a wiper with a brass brush that raises the nozzle temperature to 150°C and drags it across the nozzle to clean it before performing a beacon contact.
This is normally just a dirty nozzle from what I’ve seen. The wipe that helge made seems to be working well for me but I almost never print pla. Might need a slightly lower temp for the wipe with pla?
Does yours not do the wipe at 150 already? In front left
I’ll double check tonight, I’m printing pla at the moment as my panels only just arrived, but when I get them on I’ll be moving to and for the most part