lines in surface

hi,,

i am getting horizontal lines in my prints inspite of getting rid of my z wobble... i cant seem to figure out what the problem is.. i have even tighten my x and y belts but the bands remain....

[imgur.com]

I get this in my prints from the combined thermal expansion of the bed and hot-end due to temperature fluctuations.

I think most of my flexing is in my heated bed, I can print on a cold bed with ABS juice and get much better consistancy layer to layer.

I'm running a PID temperature controller on my hot end, which is a beast to get minimal temp fluctuations. When the temp runs high or low from set temp, the material flows slightly different, also causing layer banding.

i did the pid autotune and got the temperature within 2 degrees + - fluctuation ...... but i am still getting the banding... one interesting thing is that the line disappear on objects with no infill .....

Could also come from inconsistant filament diameter. I have some black ABS from reprapper.com that varies way too much, +/- .5mm at some places on 1.75mm filament, not good.

Looks to me to be backlash from your Z-Axis. Have you installed some type of anti-backlash constraint on your z-axis yet? I had similar issues with only using a single nut on the bottom side of my x-ends. By installing a second nut on top of the x-ends with a strong spring in between you are making sure that the z-axis cannot shift in the vertical axis. If you look closely you should notice that the lines in your print match the pitch of your leadscrews. You may not need to print any new parts as your x-ends may already be built for anti backlash nuts. Search on thingiverse for x-ends, there are several which are designed for this specific purpose.

Hope this helps.

@ archistrong

initially i used two nuts with a spring to avoid backlash... but then that setup was causing a lot of z wobble... so to remove that i used a z isolator nut

[www.thingiverse.com] and removed the top nut.... if you think it is backlash my next step would be to use acme screws ... thats all that is left to do till now..... i have tried all the z couplers out there and in the end the best results were achieved using a 6 mm threaded rod on the z axis with a rigid coupler like the one [www.thingiverse.com] ....