I'm having some trouble with surface quality.

I’m having some trouble with surface quality. It looks good from straight on, but the layers aren’t aligned as well as I would like. There seems to be a little bit of periodicity related to the lead screw, but there is some randomness as well. The printer is an Ord with 2mm pitch trap screws, 1 full step per .1mm with a separate driver for each Z motor. Flexible motor couplings, the screws are seated against the motor shafts, each end of the carriage is the same distance above its motor to within a couple of .01mm. I have tried a wobble isolator which decouples the lead screw nut from the carriage, but the results were the same.

The surface looks good straight on, but a little tilt starts to show lines at 4mm. A little more tilt adds some lines at 2mm spacing with some other random uneveness. I don’t think this is XY wobble, it seems more like inconsistent layer height. Steps/mm are correct- I can raise the Z 160mm and the motor couplers will return to exactly the same position. When I move Z with a dial indicator, movement tends to vary +/- .01mm, sometimes as much as .02mm. A move of 10mm is more likely to have a larger error than .01mm moves. There is .05mm backlash, but there are no direction changes during a print so that shouldn’t be a factor. I don’t suspect skipped steps because some moves are over by .01-.02 rather than always under. When I plot the errors in a graph I don’t see any pattern.

This didn’t always happen. I just changed it over to bowden so I was thinking that might be the cause, but I’m not seeing any signs of inconsistent extrusion. The solid surfaces look good and there doesn’t seem to be any variation within a layer. Any ideas on where I should look for a problem? The screws move around a bit, but they are unconstrained at the top and have flexible couplings at the bottom, so I don’t expect them to be pushing the gantry around. The temp is flat through the whole print, any variation is under 1C. I tightened up the X and Y belts, no change.

I had the same problem. There was too much space around the head and it was moving while retracting. After fixing the space it is ok.

I also got this sort of oddness when my print bed was using bangbang to heat up and cool off, I didn’t see the artifacts at all if in disabled the headed bed or after I put a sheet of glass on top of the build platform

The problem became more.obvious the colder the ambient room temp got.

The bed is unheated at the moment, but it’s possible that the springs are too weak or too high, allowing some movement. The E3D is snug, the heat block is tight to the heatbreak. There isn’t any wiggle, just some flexing of the carriage if I pull really hard.

You should be able to isolate bed wobble as the problem by slowing the print waaaaaay down. If you get the same pattern problem on the same print object at different print speeds, then it isn’t bed wobbling on springs

Also make sure to try other slicers, that’s not always the issue but it helps narrow it down to hardware or software

DeltaMaker had this problem occasionally. Check your V-wheels. We had a large batch manufactured from the same company that makes those, and a lot were wobbly.

Are the wheels prone to wear? One of the first things I tried was cleaning the rails and the grooves of the V wheels. I can try switching some wheels around and see if it makes a difference.

I’ve seen lead screws full of tiny debris mixed in grease cause a slight restriction and result in this pattern. The makerslide Delrin v rollers can indeed be damaged or out of round.

I had/ have similar issue. I wonder it’s going in and out of the natural res frequency of something as print progresses. As model gets higher you go in and out of this sweet spot as Centre of mass rises. Top face of print sways around particularly when things shaking around doing infill pattern pushing still-soft wall of model out slightly around these sweet spots. It’s just a hypothesis. To test would stiffen up preinter as a whole (as I have done) and stiffen up and reduce mass of print bed its gubbins (which i ave not done). Work in progress - will look into it next time I have a tall model to print.