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lars86

Help Test a Potential Cura Feature!

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Hi guys,

In the pursuit of the highest quality prints possible, I am trying to minimize the appearance of the perimeter seam.

First off, as a survey:

 

  1. Would you say that your seams generally bulge outwards, pucker inwards, or both? (sometimes the seam looks like mini cleavage, with slight bulges on either side of a small divot) (It is definitely best to print with the seam location set to "back" or "aligned", so that you can see more clearly.)
  2. What machine are you using?
  3. What slicer and version are you using?

 

For me, the seam is a slight dimple in the print skin, using the new Cura 2.1.2 (which is awesome if you haven't tried it!). I felt that this could be addressed by adding an overlap between the start and end points of the perimeter. On Github, we hypothesized, and disagreed on why it would or wouldn't work. So I decided to just test it experimentally.

I made a very simple test of a hollow test cylinder (just a few perimeter loops):

 

  • The control is without any modification
  • Overlap_0.2 is the above file, with additional print moves added to the end of each perimeter loop, which extend the loop by 0.2mm, in the correct direction. Followed by 0.4mm, and 0.6mm overlap files.

 

Here are the results on my printer (a heavily modified UM):

e1f5bfe4-25c6-11e6-8107-5aa7b29756df.jpg

Full size: Results

I would love to get a good spread of results , across different machines, and that's where you guys come in. As long as you are running a 0.4mm nozzle, this code should print just fine with PLA. If you want to print other material, feel free to change the temp (just make it equal across the tests).

Just make sure to label the prints as they come off the machine. If you are able to get decent quality photos of the tests, that would be awesome. I used a piece of tape to hold them all together for my photo, which definitely helps the comparison. Even if you struggle to get an up close photo, some descriptive feedback would be helpful too. Just describe what you see when looking at the seams, and checking them with your fingernail.

If we can demonstrate that this provides improvement for most people, I think it will be added to Cura. Here are the gcode files:

For Ultimaker Original (and other Reprap printers) running 3mm filament:

https://dl.dropboxusercontent.com/u/60958586/Seam_Overlap.rar

For Ultimaker 2:

https://dl.dropboxusercontent.com/u/60958586/Seam_Overlap_UM2.rar

For Ultimaker Original (and other Reprap printers) running 1.75mm filament:

https://dl.dropboxusercontent.com/u/60958586/Seam_Overlap_1.75mm.rar  (These files use the flow override firmware function to convert filament diameter)

https://dl.dropboxusercontent.com/u/60958586/Seam%20Overlap%201.75mm.zip  (These files were modified by DaHai8 to convert by modifying extrusion distances)

Edited by Guest

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Results like these take days, not hours. Please be patient. We have lives too.

I too hate perimeter seams and would love to minimize them.

I for one will try this out if possible and get back to you, but within days...not hours. :)

 

Results, yes. But not joining the conversation! ;)

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Ok, tried it but can't print it.

The main problem is the feed rates in your gcode are about half of what my printer requires. So only a small amount of filament comes out and nothing sticks.

I think your using 3mm dia filament. I'm using 1.75mm

Also, you X location is right at the edge of my printer's printable area (~175mm). Perhaps if you moved the item more to the center of the bed?

Thanks.

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Ok, tried it but can't print it.

The main problem is the feed rates in your gcode are about half of what my printer requires. So only a small amount of filament comes out and nothing sticks.

I think your using 3mm dia filament. I'm using 1.75mm

Also, you X location is right at the edge of my printer's printable area (~175mm). Perhaps if you moved the item more to the center of the bed?

Thanks.

 

Ah, okay! So, it's not the "feed rates", but the extrusion rate (also a feed rate). Doing a quick calculation, it looks like you need to push 1.75mm filament 2.939 times faster for the same flow rate.

I edited the gcode files to add this flow rate multiplier in, and hopefully it is without the allowable range.

I also put in a 50mm shift in both X and Y, to bring the print away from the edge for you. I like printing near the back corner of my 205mm build plate for less vibration.

Give these a try and let me know: https://dl.dropboxusercontent.com/u/60958586/Seam_Overlap_1.75mm.rar

Thanks!

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Clearly, I don't know what I'm doing.

This, from you gcode had no effect:

 

M221 S293

 

Perhaps my printer doesn't allow values greater than 100%.

So did a quick search/replace of all the G1/G0 F values to numbers 2.93 times more.

That resulted in some hilarity as the print head raced around the print bed. :)

It was then I realized its the E values that need changing. So I wrote a Perl script to multiply all the G1/G0 E values to 2.93 x greater.

It fed a bit more filament, but still no enough to stick or even make a line.

I dunno. Like I said, clearly I don't know what I'm doing.

Would it be possible to send me the Cura Engine? Would I be able to replace my 2.1.2 Cura engine with it in the folder?

I really want this to work. I HATE those Frankenstein Zipper lines!

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Clearly, I don't know what I'm doing.

This, from you gcode had no effect:

 

M221 S293

 

Perhaps my printer doesn't allow values greater than 100%.

So did a quick search/replace of all the G1/G0 F values to numbers 2.93 times more.

That resulted in some hilarity as the print head raced around the print bed. :)

It was then I realized its the E values that need changing. So I wrote a Perl script to multiply all the G1/G0 E values to 2.93 x greater.

It fed a bit more filament, but still no enough to stick or even make a line.

I dunno. Like I said, clearly I don't know what I'm doing.

Would it be possible to send me the Cura Engine? Would I be able to replace my 2.1.2 Cura engine with it in the folder?

I really want this to work. I HATE those Frankenstein Zipper lines!

 

Hmmm, okay. Let's get to the bottom of this.

Are you running Marlin firmware? Do you have a 0.4mm nozzle?

I just ran the beginning of the gcode, and the M221 S293 line sets the "Flow" parameter inside the "tune" menu, to 293%; just as expected. What made you think it did nothing?

All the extrusion distances in the gcode are absolute, so to normalize volumetric flow, for a given length, we just need to correct for cross-sectional area of the filament. Pi cancels out, so we just need a ratio of r1^2 / r2^2 to get the multiplier. I think the math is good.

Are you sure your hot end isn't clogged, or the temperatures wrong for the material you are printing?

I hand edited these files to add the overlap. This was a preliminary test to justify developing a feature in Cura.

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Not sure what firmware I'm running. The display only says "Mendel Ready" and none of the other screens say anything about the firmware type or version. I'll go back the to seller and see if they know.

It is a .4mm nozzle. And I have it set to that in Cura, along with 1.75mm filament.

I got no "Flow" menu item either. Nothing in the "Prepare" or "Control" menus have any kinda of flow setting. On the Main screen I have "Fr", but setting that just makes the print head move faster (same as with Gx Fnnn.nnnn gcode).

I think the M211 S293 didn't do anything because the flow rate of the filament out of the nozzle was unchanged, ie: near to nothing.

I agree with your math. I checked that earlier.

I've printed a few items between trying your gcode files and everything is working fine. No clogs. I did change the temps in your files from the start to match my regular print temps: 55c bed and 215c nozzle.

Post the STL of your test cylinder and I'll load into Cura and generate at .1mm res gcode file like yours. Then I'll compare my generated E rates against your's and see what multiplier is being used.

Then I can update my Perl script to adjust the Extrusion rate to what my printer requires.

Thanks!

Edited by Guest

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It sounds like you are just running a firmware that does not support live flow override (bummer).

Here is the STL file: https://dl.dropboxusercontent.com/u/60958586/Test.stl

I redid the multiplier calculation, and the factor should actually be 2.65x. The first calc was using the nominal 3mm size, but in reality I am printing with 2.85mm. You really should just be able to take all EXXX.XXX values and multiply by 2.65

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Well, here's where I get to show how smart (or stupid) I am.

Generated your object at .1mm and compare my gcode to yours. Of course, the coordinates are not the same, but at least the relative offsets and distances would be, right? Nope.

How about the relative Extrusion rates per 1 unit distance? Those should be constant, right? Nope.

How about relative differences between Extrusion rates per 1 unit distance between your gcode and mine? Should be consistant? Nope.

Argh.

Nothing is making sense. This appears to be un-testable by me. Sorry.

I've included the spreadsheet along with my gcode if you want to have a go at it, but I understand if you want to move on and find another, more qualified tester.

http://bitman.org/AA3_Test.gcode

http://bitman.org/Comparison.ods

Edited by Guest

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I think you are farther along than you give yourself credit for, but are just tripping up on some details. (and you are still the only one who has bothered to try)

It looks like your print is starting with a .15mm layer, not 0.1mm. So if you tried to do calcs on the first layer code, results will be skewed.

I did a distance calculation from your code, and divided the extruded distance, by the movement distance and got 0.0166265 mm filament / mm travel. This is 2.65175... greater than the same value in my code. Exactly what I expected to see.

I think something must have gone wrong in your script, originally. You should just be able to take my code and multiply all E values by 2.65

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This is really P***ing me off! :angry:

I found my "Tune" menu. It only appears when the printer is actively processing a gcode file. In it are "Flow" and "Flow 0" setting. I tried both. Neither do a Damn thing - no matter what value I set it too. There's no documentation I could find on either as well. Argh.

Side Note: My Tune menu also has a "Change Filament" option. So I tried that. Big Mistake! The print-head raised off the object and then moved to home, but totally ignored the 0-stop switch and proceeded to grind the motor until I quickly powered it off. More Argh.

So, I redid my Perl Code for the 2.65x E rate multiplier and truncated the values to 5 decimal places. And that worked!!!

Sort of...

The first couple of layers printed fine, but then I noticed it was overflowing - badly (see attached pic).  

Checking the values, they are all 2.65 times greater than your gcode file - even to the end:

Original:

G1 X160.916 Y67.960 E62.02322
G1 X159.924 Y68.193 E62.02960
G1 X158.909 Y68.348 E62.03604
G1 X157.896 Y68.427 E62.04241
G0 F11400.00000 X157.869 Y67.626
M107
M104 S0 ;extruder heater off

Modified:

G1 X160.916 Y67.960 E164.36231
G1 X159.924 Y68.193 E164.37922
G1 X158.909 Y68.348 E164.39629
G1 X157.896 Y68.427 E164.41317
G0 F11400.00000 X157.869 Y67.626
M107
M104 S0 ;extruder heater off

So I'm still scratching my head on what's going wrong... :(

IMG_20160705_192746.thumb.jpg.0804050f381257873b22b6eb4f6ffaf4.jpg

P.S. Just so you know I'm noting wasting both our times with a crappy printer. Mine is pretty nice and prints well at .1mm. Here's an example at .1mm and 7cm tall:

IMG_20160705_194721.thumb.jpg.0a2dcb53081ae1a0e82a694e616f6cbf.jpg

Edited by Guest

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Very weird!

Just in your little code snippet, I did the math by hand, and found it to be off slightly. But my math tells me it isn't enough to cause the whole issue though.

Did it seem to start the print extruding correctly? You could always back down the multiplier by maybe 10%. So, x2.55

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Ok. New Day and different results.

Apparently I really hosed up my printer with all the Tune/Flow/Flow 0/Change Filament testing. After turning it off last night and then testing again today, 2.65 x Extrusion levels worked!

I tested other multipliers as well: 1.7 (bad), 2.2 (bad), 2.40 (good), 2.50 (good), 2.57 (good).

So here's the 2.65 multiplier test:

5a331ed2c1d85_Test265.thumb.JPG.06fbe1a53135ac81c1372bd6007ff513.JPG

And I tried another test: here's the 2.50 multiplier test:

5a331ed315e02_Test250.thumb.JPG.a80efad10c7ef3795050496db7428eca.JPG

The Coast .4 looks better in both tests in the photos, but not as good in real life. I think the difference is that the Coast .4 has less of a divot/depression but its just as wide as the other tests. So on camera it does not show up as much.

Still, Coast .4 is a marked improvement!

I've also place the modified gcode files on my server for anyone to use if they want to test this with .4mm nozzle and 1.75mm filament.

http://bitman.org/Coasting.zip

Let me know if you want me to testing anything more!

Cheers!

5a331ed2c1d85_Test265.thumb.JPG.06fbe1a53135ac81c1372bd6007ff513.JPG

5a331ed315e02_Test250.thumb.JPG.a80efad10c7ef3795050496db7428eca.JPG

Edited by Guest

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Me for example I haven't posted because I disagree on the approach. I think a wipe + retract like s3d does its more than enough to not even need coasting. It needs test and adjustments, but I don't get z blops or marks because it can retract on that wipe + retract when changing z. So I rarely get that on the outside.

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Me for example I haven't posted because I disagree on the approach. I think a wipe + retract like s3d does its more than enough to not even need coasting. It needs test and adjustments, but I don't get z blops or marks because it can retract on that wipe + retract when changing z. So I rarely get that on the outside.

 

That is welcome feedback. Like I said initially, I would like to hear people's experiences with perimeter seams. Confirmation of my theory is nice, but I want to see what the majority experience.

Would you mind posting a close up of a print from S3D, with an aligned seam for reference? This thread is about whether overlap will improve prints in the new Cura, so it isn't directly applicable. But I'm interested to see.

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