Original source Carl Woods - Facebook Ender 3 support

Lets talk about Z-Axis problems...…:)

Sorry for the long post/wall of text but this may be helpful to someone out there so I am going to post it all up. If you don't have any Z-Axis issues then feel free to ignore!

I have 2 Ender 3’s. Both printed OK-ish from day 1 but I was getting quite a few artifacts that I wasn’t happy with. There were some quite pronounced vertical lines and also horizontal banding in prints. This varied from a couple of layers to a band about 3mm high that always appeared in the same place. I managed to sort these out. The Horizonal banding was got rid of by tuning the Z Axis. The vertical lines have also been removed now. It has taken me a couple of days to get it right but I am now pretty happy.

I’ll start with the vertical lines. I tried all sorts of fixes from tuning the X Axis and adjusting multiple times to belt tensions. Nothing got rid of them totally. In the end it was an easy fix. I wanted to remake my Z-Axis tensioner with a bearing with a smaller bore. The 5mm bore broke a couple of the printed parts due to the thin walls around the bolt. I ordered a 3mm bore GT2 idler. But I ordered one with teeth. It cleared the issue straight away. I think the lines were artifacts from the toothed belt “clicking” over the original smooth idler.

The horizonal lines were a bit more difficult. I stripped both machines and examined the leadscrews, nuts and brackets.

I have a bit of experience with ballscrews/leadscrews being an aircraft engineer. It also makes me extremely picky about tolerances! (Fun fact – I have rebuilt many many aircraft ballscrews over the years including pretty much every thrust reverser ballscrew fitted to Concorde when it was operational). In short the leadscrew and in particular the nut are junk.

One printer was not too bad after some cleaning up of the leadnut with a Dremel but the other was awful. It ran rough at various points all the way down the leadscrew. A new leadscrew and nut was ordered from Amazon. This gave me a bit of a problem as it was a larger mounting base on the nut than on the original. Reusing the original was not an option as it was so poor. So I reassembled one printer and got printing. I printed a plate to relocated the extruder further back and an adapter to mount the new round leadscrew nut to the original point.

At the same time both leadscrews and nuts were scrubbed clean and totally degreased and coated in a PTFE coating. I also put a very light coat on the wheels and rails with a cloth. The screws went in the oven at 80 for an hour to bake dry. I then spent an hour or so getting the wheel adjustments just right on both printers. I reassembled the printers with the printed parts and the leadscrews and nuts with the stepper motors left loose. I then spent about 4 hours adjusting the steppers to line up perfectly. This is a real trial and error with feeler gauges, a pile of pre printed shims that I had made and a lot of patience. Be aware that the stepper adjustment is not just front to rear, there is some adjustment side to side that is also just as important and just tightening the screws can throw it out again. The ideal outcome was that the x axis fell slowly and very smoothly under its own weight when the steppers were disengaged. In my opinion this has to happen otherwise something is binding. It’s just common sense.

I got there in the end. Both printers now fall slowly and smoothly all the way to the plate. It is the stepper that provides the only resistance. If the connector is loosened between the stepper and the screw so the screw can spin freely it drops like a stone. It is a bit of a pain if you want to disengage steppers with your end script but I overcame this by adding a line to move the plate all the way forward before they disengage. I guess on big prints I will have to leave the steppers engaged to stop it but the results seem to have been worth it.

I ran the same G-Code cylinder I had run previously and none of the artefacts or defects appeared. Out of interest I tried to tighten the Z Wheels just enough to stop the carriage falling on its own and it immediately reintroduced various areas of slight banding.

It took me hours and hours but if you have the patience and are willing to spend £13 on a new screw if you find yours is rubbish then it is a very worthwhile exercise. I have seen a lot of posts with similar issues to mine and it is almost always put down to an extrusion issue.

This shows it may not always be. I was confident my extrusion and filament path was almost perfect with bearings etc in use right through. It was 100% down to a rubbish leadscrew setup but it can be fixed at minimal cost and a bit of time. Now to run a big print and see the results. The photos speak for themselves, although they were a pain to photograph well!

I have been struggling to clear the z axis seam on my benchy print. I've seen so many examples of perfect benchy's without any seam or inperfections. Is there a cura profile with predefined parameters which can resolve this issue? I am using Generic PLA 0.4mm nozzle / Standard Quality 0.2mm / 20% Infill. I have played around with the z seam alignment and z seam position. the seam does not clear it just moves, how are others able to get a seamless print? I ordered my printer three months ago from here and I have been struggling for days on this, appreciate if someone can help please.