Vertical ripples

I’ve been printing with my Mini for a short while now, but recently a print came out with some weird ripples along the side.

http://imgur.com/dLRSoMV
http://imgur.com/1xwblq8

My first thought was a loose y axis belt since it looks like the ripple slowly goes away. When moving the belt in the y axis, there seems to be a bit of lag from when the belt first begins to move and the build plate actually moves. I don’t know if that is normal or not.

However, for whatever reason that seems to correct itself around 4/5 into each object, and at different heights on both. I read a thread over on Reddit discussing a similar issue. In their case the issue was Cura itself as Slic3r gave them no ripples.

Printed with IC3D blue ABS filament
Hotend: 230c
Bed: 110c
Speed: 50mm/sec

That can be caused by harmonics, which can be themselves caused by a dirty or gummed up Igus bearing, a Loose bearing holder, A Loose hot end or Carriage, or in some cases overtight belts. What basically happens is that your nozzle swings in or out perpendicular to its current direction of travel, and then oscillates kind of like a pendulum. Unless the part is very thin, you don’t see the matching motion on the other side of the part because it gets buried in the layer. To combat this, clean the bearings and rods with a moist and then dry cloth, tighten any loose fittings, check that the X belt seems about the same tension as your Y belt, and if necessary adjust the bearing holders in or out to better contact the rods if there is any excess play in the carriage.

I fight this a lot on my Taz 2 and 5 but have not really noticed it on my Mini… I print thin walled parts with a dark colored translucent PLA so, it is very noticeable when it happens. If all of the things piercet suggested fail to solve the problem, adjust the print speed, probably downward. If it happens to be a resonant frequency causing the problem, moving to a higher speed could also help. You will just have to play with it if it turns out all the mechanics are tight. The Mini’s default print speeds are pretty high in Lulzbot’s configs.

In the example photo where you can see the ripples stop, did you have any other parts on the bed that were fully build at that level? If so, the cooling settings might have slowed down the print at that level causing a reduction in rippling.

Thanks for the reply! Sounds like I have my work cut out for me this evening. Is there a good resource for finding and identifying all these parts?

I was printing multiple parts, so that may have affected print speed for various heights. I have it set to a minimum of 10 seconds at each height, and with how many pieces were being printed, it never had to artificially slow down. The shorter and wider pieces corrected itself while the taller piece was still rippling. It looks like it’s around 4/5s up in both objects before it fixes the ripple. In your other reply you mentioned the Mini’s default print speed of 50mm/sec is high, what speed do you usually use? Thanks for the input!

I actually run the default profiles on my Mini, most of the time. I have not seen any bad rippling on that machine at this point. To be more accurate, I should say the accelerations on the mini seem to be much higher due to the lower mass of the components.

On my Taz machines, the print speed is generally around 50 mm/sec. That produces pretty bad ripples on some parts. I was actually working on this problem this past weekend. I have went through the steps piercet suggested without good results. Lowering the feedrate to 75% REALLY helped the Taz machines as far as ripples are concerned. I will probably stick with that speed until I try the openrails mods piercet has been working on.

I might still go through Piercet’s checklist along with the monthly recommended maintenance steps. The more research I do, the more inclined I am to think it’s a software issue with Cura. I’m running the most up to date version, but might try Slic3r tonight and see if I can reproduce the problem. I’ll also definitely try reducing the feed rate.