This topic contains 31 replies, has 6 voices, and was last updated by jhr 1 year, 3 months ago.
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I would like to start a little print contest. There isn’t much to win, except better print quality for everyone or at least some of us.
If you take a close look at the images below, you’ll notice a repetitive vertical pattern, every 4-5 layers. What’s interesting is, that this pattern does not occur on every printer and on at least one of my printers not on every print. Some of my printers (I currently have 5 in use and more on the shelf), respectively some prints, instead show a totally random pattern.
Those prints with the ordered, repetitive thicker lines every 4-5 layers would be really perfect (compared to those with the jittered, random pattern), if only there wouldn’t be those repeating thick lines.
I’ve already contacted CEL and they believe this may well be an issue with the threads on the drive motors. I have to say that I have one Kickstarter machine and several blue, commercial machines, and while I could imagine that the jittered print on the KS machine could be caused by that, it just doesn’t explain why some prints on the other printers seem to flip-flop in terms of outer appearance quality.
My suspicion is that it could be a software issue, specifically a rounding error. Why else would the thick lines precisely appear every 4-5 layers!?
So here’s the “contest”: Download the attached STL and print it using my settings below. Post a close up which shows the structure of the print, including AM version and the OS platform and version you are using.
The samples below have been printed using
- AM 2.00.01 on Mac OS X 10.11.4
- Cura slicer
- PLA (Robox)
- Fine settings
- No raft or brim
- Infill … I can’t recall, probably 15% or so.
Perhaps we can figure out what’s going on here…
(@bhudson mind to give it a shot?)@bhudson Seen this issue before?
Also interesting, but not the topic of this thread is the different print quality in the gables. The work-around to get fine, yet perfect details at the top is to place an object into the layout, which is higher than the rest, as you can shown and discussed in my post here. But again, that’s another issue.
@dr-woo I have access to five printers right now and will run this on all of them. I will track the serial and also the gantry style.
There are three generations of gantry - Gen 1 is a rigid connection between the screw and the guide rod. This was shipped on Beta units and some early trade samples. I do not have access to any of these right now. Gen 2 and Gen 3 are similar. The difference is in the fit in the barrel connection between the Z screw and Z guide rod. Gen 2 has a square cutout on the steel plate over the bearings, Gen 3 has a trapezoidal cutout. This may be the driving factor in this little phenomenon.
Another point to look for is the generation of Z screw and how straight the Z screw is. If there is an undercut at the bottom of the threads that is the latest screw, Gen 3. Gen 2 does not have an undercut. Gen 1 does not have an undercut and is point welded at 3-4 points around the screw. Straightness should be gauged by no wobble, some wobble, a lot of wobble. I would say no wobble is less than 0.5 mm, some wobble is 0.5mm to 2 mm, lots of wobble is >2 mm. The best way to determine wobble is to watch the screw while running the Z test.
I operate two Betas and four Production Robox.
I am the US/Canada Technical Support engineer for the Robox.
See my 3D Hub site at https://www.3dhubs.com/phoenix/hubs/benhttps://www.dropbox.com/sh/ktg43wsmhwrq3li/AAByNsUXynMg1xAU9jjqj9hJa?dl=0
Folders correspond to serial number.
4514-0241 has Gen 3 gantry, Gen 3 screws, no wobble, used PLA on AM 2.00.01
KS-1614-0023 has Gen 3 gantry, Gen 3 screws, no wobble, used PLA on AM 2.00.01
KS-1614-0038 has Gen 3 Gantry, Gen 1 screws, some wobble, used XT on AM 2.00.02-RC4
KS-1614-0024 has Gen 3 gantry, Gen 1 Screws, some wobble, used XT on AM 2.00.02-RC4
4314-0019 has Gen 3 gantry, Gen 2 screws, no wobble, used XT on AM 2.00.02-RC4
Hope this helps.
I operate two Betas and four Production Robox.
I am the US/Canada Technical Support engineer for the Robox.
See my 3D Hub site at https://www.3dhubs.com/phoenix/hubs/ben@bhudson Thanks a lot for your efforts. Unfortunately it is very difficult to see the actual layering effect from your pictures. In my samples above the only light source came almost straight from top, so every layer drops a shadow against the one below, so the layer pattern becomes easily visible. Also close up and no elevated view, but full frontal, so perpendicular to the layers. Mind to re-shoot the results again?
As for the gantry versions: my KS machine still has the Gen1 style, all other blue, commercial versions have been upgraded by myself from Gen2 to Gen3. The facts that I’ve seen jittered prints and print with repetitve lines on ever 4-5 layers on the very same G3 gantry machine, somehow speaks against the gantry theory.
The straightness of the Z screw is an interesting point and is a logical explanation for the jittered prints, at least on my KS machine. CEL has already offered me to replace the Z motor (with screw).
I assume that if the Z screw is perfectly centered and doesn’t wobble, that eliminates jittered prints (still don’t understand though why I have printers which obviously sometimes jitter and sometimes don’t).
What this doesn’t explain are the noticeable, totally regular lines which periodiocally appear every 4 or 5 layers. Note that this isn’t an XY-shifted layer, but more like a bulge going equally all around! See below. Know what I mean? What we see here is 4 layers perfectly aligned and stacked on top of each other, and then every 5th layer being somehow squeezed on top (or being printed with a higher material flow than the 4 previous layers), which causes the bulging.
To me this looks like a software, rather than a hardware issue. And to figure this out, it would be interesting to see if others have the same ‘bulging’ every 4-5 layers as well. I mean no doubt, the Robox delivers excellent prints, but if we wouldn’t have this repetitive bulging/ripple effect, the print surface would be as perfect as FDM can be.
@dr-woo I have uploaded several more shots of each print to the same folders. The lighting should be more revealing.
I operate two Betas and four Production Robox.
I am the US/Canada Technical Support engineer for the Robox.
See my 3D Hub site at https://www.3dhubs.com/phoenix/hubs/benI concur with the 5 layer repetitive pattern on roof. Not so sure about the vertical feature though.. Anyway attached is the picture of print from your *.stl file showing the 5 layer issue. Note that near top of roof there was one of the 5 layer patterns that is much better, not quite perfect but better.
My set up is:
- AM 2.00.01 on Win10
- machine date manufacture date is 51/14 I don’t know the gantry details but are original.
- Cura slicer
- ColorFabb XT white
- Default Fine settings
- No raft or brim
- Infill 20%.
It does look like a software resolution/rounding issue, but needs to be investigated further.
I will have a bit of time to experiment during the next week, so will look at some print angles and STL resolution parameters.
I normally see a slight resonance or mechanical effect when printing vertical surfaces in the X or Y planes, but do not see the 5 layer effect you have, but I don’t know your part orientation.
BTW thanks for the tip on fine detail at top of print by adding a higher feature.
Regards John
@john Thank you for your post. I have to say that I perhaps shouldn’t have provided a model of that house, because the focus of the issue which matters to me, can be seen much better on straight, perpendicular walls than the tilted roof top. A simple, 15*15*15 mm cube printed with Fine settings should already reveal the repetitive lines every 5 layers.
It seems to me that those repetitive lines are always there, but they just can’t be seen if your Z axis wobbles, thus your prints are jittered (as you can see in my very first picture here above, to the very right [Green Kickstarter LE]).
As for the fine detail on top issue: CEL seems to have it on their bug list.
@dr-woo Thanks for feedback. I used the roof as it was easier to get a photo of the layer deviation. This is at limit of my camera
As it happens I use a 25mm cube to check accuracy of the printer. Have attached a photo of one of them (most I have used normal settings, this one was done on fine settings @ 20% infill, other details as before).
The pattern is certainly consistent, about 50 in 25mm i.e. 5 layers in fine mode. This could be a thread issue with the Z screw but needs to be proved. The effect is quite small on my machines, but now will have to try to quantify it.
regards John
I just came across the following image from CEL’s October 2015 blog post on the Dual Material Head status again, and immediately noticed that one can here as well clearly see that sort of rim which appears approx. every 5 layers. The BIG, BIG question is: Exactly what is causing these rims? IMO it’s clearly a software-related issue (the precision with which those rims reappear along the Z axis makes me believe this). But is it caused by the slicer algorithm (we are all using Cura now; anyone still access to AM w/ Slic3r for comparison?) or a bug in Automaker itself (numerical rounding error?)?
Those rims are the only flaws which prevent the Robox print from being as perfect as FFF/FDM can be!
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This reply was modified 1 year, 4 months ago by
Dr. Woo.
@dr-woo “a bug in Automaker itself (numerical rounding error?)?” I don’t think AM is doing much but passes object (stl) to Cura to be processed. Also, if it is Cura’s problem wouldn’t same existing Ultimaker (and tens of other printers of people using Cura around the world)?
On the other hand, while we are speculating - what about firmware and rounding error? (same thing you said but now focused on software in the Robox itself!) And there you would like to have access to older firmwares to try it out. Although I wouldn’t expect it being introduced - more like something that was always there but we didn’t pay attention. I am yet to try to print your test print.
I totally agree in that if it is a Cura-caused problem, the problem would very likely also affect every other Cura-relying printer out there. Problem is that I don’t have access to for instance an Ultimaker to investigate this.
It should be mentioned that the problem as far as I recall becomes only visible in Fine print mode, not in Normal. I could be wrong however, I would have to to test prints again.
Speaking of test prints: I’d say forget about my provided STL test object (house). A simple (hollow) cylinder, perhaps 20 mm in diameter and 20-25 mm height should do a better job (as it is less view point dependent when taking pictures).
Addendum: I’ve searched the web for fine/ultrafine Cura-based Ultimaker prints and found for example the following ones. Some jitter on that cylinder, but not a single case with indication of those rims. Perhaps I’ll post my above images with the rims in the Cura forum and ask if anyone has spotted this effect before.
Also take a look again at the images at the very top, which i used to open this thread: My conclusion is that any random pattern is caused by a mechanical jitter, while those repetitive rims are software-caused. The randomly patterned prints probably have those rims as well, however they are not visible because of that jitter.
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