Try to run the head up and down in Z and see if the head wobbles left to right as it travels up and down. There is a calibration burnin gcode file that should be of help for this.
I have not had to do this for a couple months now. As it runs up and down look at the outside edge of the threaded rod by using the the outside edge of the smooth rods as a reference.
It seems a Z axis issue is more likely considering the periodic nature of the banding, but dealing with that might be pretty difficult if it can’t be resolved by checking for loose set screws in the coupler (one to the motor, one to threaded rod). I did notice two things about the pieces though, and it might be worth trying some other easy things first:
If you look at the bottom of each piece, the part that touches the buildplate, you see that there is some extra extrusion around the entire perimeter of the pieces you printed, and not on the factory piece. If it is over extrusion, measuring the filament diameter with calipers and adjusting that number might help. You can also adjust the flow rate. You have to do this in expert settings. There’s also the initial layer width option you might want to check – the default is 125% but I would think that would affect only the initial layer being a little over extruded. Assuming the factory piece was printed with this 125% first layer, you are now getting a lot more filament coming out than they did at the factory, probably over the entire print.
Also your build plate might have loosened. Do the edges perpendicular to the X axis wiggle up and down? Mine did after a while, just remove the print surface and tighten up the screws underneath that attach the plate to the carriage. I don’t think this would make the regular banding you see, I think it would look more random, but it’s worth checking because it takes only a second.
After printing another square piece in green ABS it seems the z-axis ripple effect is only present in one dimension! Only on surfaces perpendicular to the x-axis.
IMHO the problem seems to be because the z axis threaded bar is a little bit bent (If this is the problem you would need to replace it).Also check if the connection with the motor is centered and tight as it was adviced before.
I don’t see wobble in my printer on the Z axis. Your X axis pulley wobbles more than mine – I have a little wobble, but I had to really squint and repeatedly run the print head back and forth to see it. On yours it is obvious right away.
Hey there,
I would just like to follow up this post by letting you know that LulzBot support came to the rescue, confirmed a bent z-axis threaded rod - these things happen, but what is important is what is done about it. In LulzBot’s case they returned and replaced the printer, and even though they didn’t have to, covered the shipping. Great support response in the face of a difficult situation and I would continue to recommend LulzBot to anyone I meet.
