Parallelism, other issues


#21

While you have your hair dryer out you can also bend the bed holding hooks a little inward to avoid the bed moving around, that can sometimes ruin the finish on long prints and a little tension does not impede bed leveling at all.

Already designed a replacement hook that has a slant on the top.
One is enough to keep the bed from moving around.
Going to put it on Thingiverse and link here once i’m done with yet another rebuild/recalibration.


#22

Here’s the replacement hook:


#23

Here’s a video of one of the deformed carriages before the fix:

https://youtu.be/9QOIIv-_fq0

And here’s a video of it after the hairdryer fix:

https://youtu.be/59_0VN7J21Y

It’s still not quite perfect, as i had to eyeball fixing the twist in addition to fixing the bend of the bushing receptacles. It’s an approximation - it’s way better than it was, but there’s still a dimensional error present that i had to fix by using the rod length trim.

If there’s an official fix (replacement carriages off a fixed mold), i’d appreciate it (cc @VEL337)


#24

Hi Orcinus!

If you PM me your address we will send you new parts.

Best Regards,
VEL337


#25

orcinus
Very nice fix!


#26

PM sent!

In other news, here’s a recent PETG print:

It’s a replacement Y carriage for my E3D BigBox.
So far, seems like everything more or less fits, although some holes were a tad undersized, and i had to open up the linear bearing holes quite a bit in the STL to get the bearings to go in and line up properly.

I still need to figure out a way to get rid of those diagonal artifacts, gonna have to try the anti-parallel diode trick one of these days.


#27

This seems like ghosting/ripple. Try decreasing the acceleration on the printer.


#28

It’s not, i assure you.
Or, at least, i’m not talking about the ripple.

I’m talking about the parabolic artifacts that coincide with tri-lobes of the tower motion ranges, and go from parabolas to diagonals as you move further, i.e. the exact thing experienced by others due to missing microsteps.

The face facing the camera in the second photo was facing the Z tower dead on.
You can’t have continuous artifacts across the whole surface from ripple, much less diagonal ones. The mechanics just don’t work that way.


#29

If you look at the last photo, very bottom of the object, you’ll see the bottoms of the parabolas too.


#30

absolutely off-topic question:
which settings (retract, temp, cooling) did you use for your PETG?


#31

Default cura K8800 profile retract, temp 245, cooling at 80% to fight the stringing.

I had one part snap, the rest are fine, so i doubt it was due to too aggressive cooling, i think 80% is fine, and it was just a segment of the filament that had too much moisture in it.

Using hairspray (well, actually, 3Dlac, which is almost the same thing) on the bed, had no trouble with sticking, and no trouble getting the prints off.


#32

ok - back on topic…
IMHO it’s a problem of the moving print bed - moving in Z-direction.
If you’re printing close to the boarder, opposite of a tower, the bed is simply pressed down, because it doesn’t have a catch in Z-direction.
You can see it if you compile your Marlin with “UBL” and try to calibrate the whole thing.
So, a Z-catch close to the piezos may solve that…


#33

Not really, that has nothing to do with it.
What you’re describing would not be periodic in nature, and would not exhibit phase shift across layers (i.e. wouldn’t result in diagonal lines).

What i’m talking about is this:
https://reprap.org/forum/read.php?178,763881

Here’s a good example from that thread:


#34

I’ve just realized you might not be actually seeing what i’m talking about in my photos because of their resolution (causing moire when the forum resizes them). Here’s some highlights from cropped portions of the photos

Diagonal_2

Diagonal_1

Diagonal_3 :


#35

Here, this print should make it more apparent:

Of course, the angle and intensity change depending on where the face cross-sections the tri-lobe motion ranges described by the towers.

Edit: Yes, i need to trim my fingernails, i know :frowning:


#36

I know now exactly what you are talking about and I think it’s called salmon skin.
I honestly don’t mind that artifact at all since it’s usually very vague on my printer and IMO it doesn’t take away from the esthetics of the part more than visible layers do.


#37

If it is salmon skinning you might try layer height of 0.17mm which should theoretically lead to a minimal salmon effect.
You might read the following thread:


#38

Yeah, i know about that, but it’s still not a permanent solution. Odd layer heights are not always a good idea if you need Z accuracy, and if you’re trying to optimize for layer height vs. extrusion width (e.g. when trying to get very thin extrusion widths, in order to get better surface detail / textures).

In any case, got a bunch of 1N5408’s, will give the diode voltage drop fix a try, see if it does anything for one of the axes. If yes, there’s readily available “smoother” boards for cheap nowadays (2-3 EUR) that you can hook up between the stepper and the driver. Pretty small footprint too.


#39

If you need Z-accuracy you’d need a solution for the beds Z-movement when printing. So the salmon skinning is your least problem…
Simply lay a ruler over the piezos and look where the axis lies - anything larger (towards the border) will give you offsets because of the pressure related Z-movement. It looks like warping, but it isn’t…

And - if you try UBL to compensate you’re completely lost…


#40

Dunno, i’m getting pretty good Z accuracy as is.
In fact, that’s the least of my worries - it’s better than what i’m getting from X and Y at the moment :smiley: