Regular irregularities (not only) on the surface...

Hi.

I've got a cheap Prusa i3 Rework, redesigned by someone for selling. I bought it a month ago and used only with PLA, most of the time with 0.4 nozzle and 0.2 layer. Recently something happened and the printer is practically unusable. See the photos and the explanation below:



As you can see it happens on every layer, not only first. And not only on the flat surfaces, but also on perimeters (then it's not a line, but a crack in a model's wall - it looks like a string with small balls of filament) and infill. Generally everywhere.

I'm pretty sure it happens with every single turn of hobbed bolt. I checked - it doesn't have any visible irregularities. My guess is broken extruder stepper, what do you think?

More details: it doesn't get better after changing temperature, slicer (Slic3r and Cura tested, previously both worked fine), filament etc. I'm also pretty sure the nozzle is ok. The only thing that makes a slight difference is increasing layer height, but it's just a workaround, not perfect though. Any ideas?

Hi

I'm getting a very similar issue. I consistently get points on the print where less plastic is extruded. To make matters worse, when this occurs, the hot end then sometimes picks up the previous layer and stretches it, totally messing up the layer and distorting the overall print.

After inspecting and running loads of test prints (including varying temperature and print speed), I finally noticed that the irregular extrusion happens at every turn of the gear. This led me on to looking at the hobbed bolt whereupon I noticed that on one side the groove appears to be a little deeper than the other.

This suggests to me that the cause of my irregular extrusion is a poorly formed hobbed bolt. I suppose that replacement is the only way to test whether this is the case so I have yet to prove that conclusively.

Have you checked your hobbed bolt? Does anyone else have any ideas on this topic?

Hi

Sorry for the late reply.
In my case, like I expected, the only thing that helped was replacing extruder stepper. It had to be faulty.