How to reduce Z Ribbing?

I've owned a Robo R1+ for many years now. It served my needs well, but i recently bought an R2 as an upgrade. Although the hotend was pushed out of position sideways/diagonally when it arrived, after pushing it back in place it printed out of the box with no issues using both the screen locally and from Cura from my computer. I'm rather pleased with the results. I compared my results with my R1+ and they are close. The R2 has slightly better results, as the z layers are less noticeable (slightly).

However, I would love to further perfect the prints and try to further reduce my z ribbing and reduce or eliminate post-processing cleanup. Previously, i could reduce the fill and change a few other parameters in the MatterHackers software to reduce z ribbing, but it would reduce the strength of the parts. I mostly use PLA right now.

I understand that with FDM printers, a certain amount of ribbing may be unavoidable, but does anyone have some ideas on how I can further reduce the z ribbing effect? As-is, it is extremely small to begin with. Am I just trying too hard to remove this from my prints? Tell me I'm being too picky?

 

My terminology may be off Mark, but it is the z height edges that are created when the layers are printed (squished together). I thought this was called ribbing, compared to the z wobble, which is when the gears/rods move up/down as the print runs and the slant on the rods can slightly move the print head around. And yes, it could be an overflow problem, but before i make more changes, I want to know 'just how good' i could get the prints. I don't want to chase a dream.

Enclosed are two pics. The one pic is of a pink test print from my R1+. You can see the layers are more spaced out and the ribs are more noticeable. In that pic, there is a new part in black that the ribs are much more refined. And the flat black piece is the raft of that part that shows another problem i am having, which I'll explain in a minute. As you can see, the R2 prints better than the R1+.

In the second pic, I printed basically the same object on the R2 (in black) as the R1+ (in pink). You can see the layer resolution/detail is much better on the R2. I'm not saying the resolution/quality is bad on the R2. It is great actually. Very, very good. I was just wondering if anyone has gotten a more smooth side to their prints. When i use my fingernail over the edge, it is not smooth.

With the new R2 I am having difficulty getting the prints off the print bed. I think i have the version 2 print bed. It is a matte black finish material. This is a big change from my R1+ where i had issues getting it to stick. I'd prefer having issues getting off the bed over it not sticking. However, the raft is very difficult to detach from the print most times and I'm not sure how I would go about adjusting that.

 

Ok, thanks for the info. I'll try to adjust the Z offset a bit and see what the results are. That first link you provided looks like a great resource, as well as the others. I will work through that as well. Great stuff. I'm going to try to see if i can get the sides smoother.

 

Your sides are just normal for FDM, of course making thinner layer makes the layers less visible. For some materials there are different possiible post treatments to make the sides smoother (sanding, epoxy coating, acetone vapor chamber...) that you could look into.

 

FDM should work for my immediate needs, but future projects may dictate having a completely smooth surface on the edges. I'll still work toward perfecting the prints some more, but I won't lose sleep over my results. I also feel that they are very good indeed. Thanks again for the feedback and the links.

 

Form1+ printer: This part is about 1.25 inches wide. And this isn't even on the printer's highest quality setting.

 

I once wanted to try seeing what printing something oversize with extra perimeters then milling out the excess would give... obviously limited to certain shapes and a lot of work, but maybe for the rare times it's needed...

 

Yep, I do the same. FDM lacks good dimensional accuracy. Combination of the way most machines are built (including the R2) and the nature of the fabrication process (extrusion). With my MakerBot, I got in the habit of printing reference surfaces over-large and then milling them down to spec on my TAIG CNC. But my FormLabs SLA printers pretty much eliminated the need. They print "balls on accurate", within a few thousandths which is great for something that's essentially "plastic". If only the resins were a bit more mechanically robust...