Correcting 'Ghosting' Issue in Prusa MK3S+ Printouts

For the past few prints with Prusa, I noticed strange ‘ringing’ and waves pattern- which I later learnt the issue is called ghosting. It was especially pronounced at the edge of the print like the flower patterns here.

Really bad ghosting issue with Prusa print

At first, I wasn’t sure what was happening. I then started to search online what this phenomenon is. I learnt that this was a ghosting issue, which is a rather common issue with 3D printer- including Prusa i3. Quick check to Prusa website, it advised to check the belt tension for both X- and Y- axis. The belt tension should be between 240 and 300. To find the value, go to Support> Belt Status. I checked the status of my Prusa, the values for both were in 270s.- so there was no problem with the Belt tension.

‘Ghosting’ Phenomenon

I speculated that it might be the plastic, so I decided to use different plastic: same result. Next, I thought perhaps the issue is with Cura. So I used PrusaSlicer for next print: same ghosting result. Afterwards, I decided to update the printer profiles on Cura and PrusaSlicer: same results.

Getting desperate, I cleaned up the printer and greased the X- and Y- metal rods: same results. I played around with various print settings: slowing down the print acceleration, changing the infill pattern, changing wall thickness, slowing down print speed. Nothing solved the ghosting issue.

Tightening Y-axis Belt

I decided to check the Belt Tension more carefully and more thoroughly. When checking X-axis and Y-axis belt tensions, Y- belt felt somewhat looser than X- axis belt and yet they gave almost identical reading. I went on to tighten the Y- axis belt from the adjustable belt holder situated below the print bed. To do this, I needed to put the print on its side to be able to access the Y- axis belt holder. I tightened all the screws in the holder (without over-tighten them of course), and brought the holder ever slightly closer together. Once all completed, I ran the Belt Tension test and for Y-Axis, it gave a reading of 287- which is higher that previous value of 270s. The reading actually puzzled me because the higher number means the belt is looser- but I just tightened the belt!

I decided to run a test-print anyway. Lo and behold, it printed flawlessly just like a new Prusa would do! See the stark difference below.