Array of Poor Corners

[ahoeben 1,953]

Now I have a craving for chocolate...

[Slashee_the_Cow 294]

3 hours ago, charlesrkiss said:

Thanks so much for your feedback, Slashee!!

Always nice to have a happy customer!

 

The first thing that comes to mind when I see those photos is: what do you have your jerk set to?

(It might be what the "corner velocity" is in the firmware, I don't know Klipper... in that case I would know what it is)

 

Remember that the nozzle generally isn't dropping filament straight down on the bed, it tends to create a bead on the end of the nozzle which leaves a trail behind it. Jerk affects how much it can change speed instantly at a corner, so if it's too high the trail will just change heading to follow the nozzle at a bit of a diagonal to reach the new line it's printing instead of reaching the corner fully.

(Also if it's too high it can make the printer vibrate whenever it rounds a corner which could make a model wobble out of alignment or if your printer isn't tuned correctly, possibly make it slip a step or two on the motor and give you some layer shift.)

 

The traditional downside with having really low jerk (other than the increase in print time) is that it has the potential to cause overextrusion because of how much time the nozzle spends at the corner slowing down and then speeding up again, leaving a blob, but if you have linear advance set up then hopefully it's controlling the flow well enough to prevent that.

 

This is actually my last print. It's really hard to see because... well translucent TPU mostly, and then the forum will crush the image quality when I upload it.

I had jerk on that set to 1mm/s. Because it's TPU (squishy and flexible) and very tall and narrow, so did not want anything making it wobble even a little. There are slight blobs on the corners (and there's a whole lot of crap because TPU is annoying as hell to clean up). You can test it that low, of course, obviously TPU behaves pretty differently to PLA or PETG.

 

(120 Slashee points to whoever can correctly identify specifically what the yellow thing in the top left is. Message me your answers, don't want to send the thread off topic)

[charlesrkiss 0]

I managed to print two separate prints and combine them. The image with green tint background is one array of 81 squares, and the image with the black background is during the insertion of the grid piece (over the print bed, over the 81 squares).

The image with the white background is also both prints 'sandwiched' together, the finished product, on a sheet of paper.

 

I ultimately failed to print both simultaneously because the bottoms stuck together. This is a problem I can work on, probably, if desired.

Then, I wanted to print an additional file, the grid in white (to make the images of the two separate prints more distinguishable), but I clogged the printer after changing filaments from black to white, I presume. The print was terrible. I will have to examine this and try other prints over the next couple days. 

Also, I will start another discussion over on the klipper community page using the same title. I have to go over there and ask questions about pressure advance, corner velocity, and the usual acceleration/deacceleration settings.

And I am definitely planning to try some of your suggestions, which may be better and simpler solutions!

 

I will try to do all of this simultaneously over the next couple of weeks. 😹

I made a lot of progress over the last few weeks. Thank you so much Slashee !!

 

Edited May 7 by charlesrkiss

[charlesrkiss 0]

Okay, Slashee, I have this amazing tool I copied from GitHub (https://github.com/tjjfvi/CuraSettingsInjector/tree/master), it writes the end of the G-code with all the Ultimaker settings.

 

Maybe you already know about it. I attached the gcode to this print. Based on the images, what settings would you change? 😹

 

I looks to me like the nozzle is not getting quite to the end of the line and is cutting corners, literally and figuratively, and also spends too much time (cutting the corners) and melts the surrounding material and deposits more than it should in the form of a blob. But it's much better than it was! 

 

There are so many UltiMaker settings to choose from!

 

There are some elephants' feet I can get rid of, probably. Besides, the adhesion is too good on the PET tape, which is becoming the perfect print surface medium for these. So I have a lot of room to decrease adhesion things like width of first layer.

 

Also, hilariously, the prints were highly electrostatically charged. As usual, but the little black squares uncontrollably jumped around like popcorn, as I would try to peel them off the PET, and would fly to other parts of the PET sheet and stick there, where there were lower energy states, apparently. 😹 

I imagine I have to spray these prints with something immediately after printing, like an oil or detergent or dip it in water with a hair dryer.

 

Is not "Jerk" the same as high acceleration and high deacceleration values at corners? I am wondering if it is that same as the square_corner_velocity setting on Klipper, because apparently I can not use both settings simultaneously. Argh.

 

CE5S1_28_array.cup.gcode

Edited Sunday at 01:47 AM by charlesrkiss

[Slashee_the_Cow 294]

1 hour ago, charlesrkiss said:

Is not "Jerk" the same as high acceleration and high deacceleration values at corners? I am wondering if it is that same as the square_corner_velocity setting on Klipper, because apparently I can not use both settings simultaneously. Argh.

Sounds like that's the setting you're looking for. Jerk is how much it's allowed to instantly change speed at a corner (because if it came to a complete stop then started moving the next direction, it'd leave a blob.

 

Technically regardless of the jerk setting the head should go to the corner and then move in the next direction, but since the filament you're leaving behind isn't right under the nozzle (it's a small bead that follows it), changing speed too quickly at corners will make that bead take the straightest route to keeping up with the print head, effectively cutting the corner.

 

It's something that requires a bit of testing to set up if you're looking for accuracy: too high and you'll be effectively cutting the corners. Too low and it'll have to slow down so much that it leaves a blob. And not that it's a problem for you, but it also matters if you're printing something tall: if your jerk is too high the bed could vibrate and make your print wobble a bit. Especially fun when you're trying with TPU (although when I did that it actually came out reasonably well).

[charlesrkiss 0]

Hi Slashee, thank you so much for your comments, they really help a lot. Huge improvements have been made!

I'm a bit confused between the UltiMaker and Klipper interactions/interference.

 

Apparently, some UltiMaker settings have to be disabled for the Klipper settings to work, and/or vice versa.

 

Conversely, I was wondering whether these corners in the image look nominal or unusual to you, because they look odd. 

It looks to me the corner at 9 o'clock is the result of the nozzle and extrusion stopping, and changing directions, as you indicated (or it lifts up completely and goes somewhere else, one of the corners must be that, I imagine.

 

Also, it looks like the corner at 6 o'clock is rounded, ie., rounding the corner (not stopping and restarting), like the other two corners look. 

I also read somewhere that slicers may code corners at different orientations differently, such as from various directions, and perhaps doing more.

The corner at 9 o'clock may be an optical illusion, but it does look very tight, like it's the corner where the nozzle started and stopped (not rounding a corner). This is just a guess.

The width of the black rails coded in Blender are 0.25 mm across. The nozzle was 0.2 mm. The corner at 6 o'clock looks like it has a radius of 0.5 mm, which is twice the wall width (cross section) — two-and-a-half times the nozzle diameter.

I probably need to take another photo to understand what is happening at the bottom, but is not as important as the top, and the 9 o'clock corner needs another photo from a different angle.

 

The flat part at the top is coded in Blender as 0.10 mm across (see Blender image). And it looks like UltiMaker is dealing with it okay. The fillets are not important to me, but may help the slicer deal with a 90-degree angle, which is why I put them in.

Finally, I ordered a 0.1 mm nozzle with some black Polymaker PolyMax PLA. So things are about to get squared times worse! 😹

 

If that is not bad enough, is it possible for a slicer or software to treat all the corners the same, eg., starting and stopping there (at each corner, and not round them)?

 

 

 

 

Edited 21 hours ago by charlesrkiss

[Slashee_the_Cow 294]

7 hours ago, charlesrkiss said:

I'm a bit confused between the UltiMaker and Klipper interactions/interference.

I'm not sure I quite follow. Cura will only ever treat UltiMaker printers with any UltiMaker specific options (and its gcode flavour). You mean between Klipper and Marlin (the gcode flavour a lot of printers use)?

 

AFAIK (or in English, what I say until @ahoeben comes in and corrects me and we all learn something so I don't mind) Klipper supports a subset of Marlin commands, enough that it should print an average Marlin file, but for several advanced things (like jerk) with Marlin it's up to the slicer to do things (program moves at the right feed rate and/or set the acceleration values, Cura does the former), whereas with Klipper you can set the corner velocity and include fairly simple move commands and it will automatically adjust the acceleration and such.

 

Cura doesn't have proper Klipper support, so it just slices files in Marlin and relies on Klipper to print based on that. I'm guessing the Klipper Settings plugin available from the marketplace overrides it so Cura doesn't do it and includes the Klipper commands to set those options in the gcode file (haven't tried it, for obvious reasons).

 

7 hours ago, charlesrkiss said:

If that is not bad enough, is it possible for a slicer or software to treat all the corners the same, eg., starting and stopping there (at each corner, and not round them)?

That situation is exactly what jerk exists to avoid: you're never going to have precise enough control over the extrusion to avoid either blobs or underextrusion if you come to a complete stop before moving in the next direction. It'd be fairly easy to hand code a Marlin gcode file to test that but I don't know if Klipper would mess with it in the printing process to automatically apply adjustments.