Small holes are filled

[Victor_Fournie 0]

Hi everybody, 

I am new on this forum, so please be gentle 😉

I used a custom 3D printer, which goes down to 10 um of resolution. I used Cura to slice my device and obtain a code. Then I re-interpret this gcode for my own software. I like cura as I can make do it everything, with a lot of tunable parameters. But I encounter a problem, or maybe a bug :

When it comes to small holes or small structures, cura fills everything. My parameters are set so that the filling is at 100% and coming at the junction of 1 wall (or sometimes, even 0 wall). For 'big holes', cura stop at the limits, as it should. But for smaller, the filling just does not stop, and goes over and continue beyond. 

I have link an image of the result slicing in preview, my structure in .STL (from fusion360) and the Cura project in .3MF. This structure is just for test, with holes from 840 um to 40 um. Cura stops printing them at 730 um.

I don't think that my piece is wrong as there is nothing red in Xray view. I have tried changing many parameters and looking on the forum (title of the most promising post : Cura ignoring small holes). Here are some of them : 

 

  -turned off union overlaping volumes

  -set maximum resolution to 0.001

  -filter out tiny gaps off

  -minimum infill area to 0 or 0.001 mm2.

Looking forward to hear your advises!

Victor

test diametre.stl test diametre.3mf

[nallath 1,124]

If you change no settings at all it will print most of the holes



Also, is there a specific reason that you set the build plate of the S5 to be so small?

[Victor_Fournie 0]

Thank you for the answer. 

My printer is full custom, so I started with a S5 on cura and changed almost everything.

It is true that it is doing better with the default parameters. But still, it is not printing the holes below 360 um which is still too big sometimes.

So I changed the parameters one by one to join mines. It happens to be the number of "bottom layers". So either, I say, my whole piece is made of bottom layers (which is not very nice), or I need to find what are the difference between the bottom and the rest. And still, I can not print below 360 um. 

Any idea?

[nallath 1,124]

53 minutes ago, Victor_Fournie said:

Thank you for the answer. 

My printer is full custom, so I started with a S5 on cura and changed almost everything.

It is true that it is doing better with the default parameters. But still, it is not printing the holes below 360 um which is still too big sometimes.

So I changed the parameters one by one to join mines. It happens to be the number of "bottom layers". So either, I say, my whole piece is made of bottom layers (which is not very nice), or I need to find what are the difference between the bottom and the rest. And still, I can not print below 360 um. 

Any idea?

If it's a full custom printer, it's probably better to start with the custom fff printer.

 

[Victor_Fournie 0]

Well at first I did that. But some issues were rising. So starting with a working set of parameters was a good idea, and then converge toward my parameters. I will try again, but that does explain what is the issue with the current set.

Edited November 26, 2020 by Victor_Fournie

[GregValiant 1,411]

The hole test.  I know it's a mess but the point was to get as many holes in as possible.  I'm leaving room for someone to ace this test.  I had the nozzle size down to .05.  I started thinking about the resolution of the STL file.

 

 

Next is my block.  Holes from .01mm diameter to 2.2mm diameter and with a realistic 0.2 nozzle.  The block is 20 x 20 x 10 high.

Before exporting the block from AutoCad I scaled it up 100 times.  When I loaded it into Cura I scaled it back down to 20 x 20 x 10.  The resolution seems to have scaled as well.  The .01 and .02 dia holes are ignored.  The .03 hole is there but is not round.  The .04 hole is almost round.  From .08 up they look like holes.  Setting the Minimum Polygon Circumference to .001 seemed to help.

 

 

 

 

 

[Victor_Fournie 0]

Thank you for your answer greg Valiant. Could you share your parameters/design? because I can not get it to print holes of 0.03. As for my side, I tried to scale it up and down, and it always stop at 0.4mm of diameter, which is equivalent to 0.1mm2 (my minimum infill area is 0 or 0.001mm2). Nozzle diameter didnt change anything. Also, these holes are only open for the top and bottom layers. For bulk layer, the holes are even more filled. Is it the same for you?

and nallath, it seems you are from Ultimaker team : are there deeper parameters that I could acess to correct those filled holes? As it is quite important for me, I am ready to go into the software files.

Thank you two again

Victor

[GregValiant 1,411]

Sorry Victor.  I suffer from short attention span and I moved on.  I will re-create the block and I will post the 3mf file here.

 

@gr5 is a moderator here and he coined a term that I like...it's the "snot factor" and is used to describe the tendency of a nozzle going around a hole to pull the plastic in towards the center.  It always makes the hole smaller hence the "Horizontal Hole Expansion" setting in Cura.

With the size of holes you are talking about I'm curious how you will mitigate the "snot factor" to get the plastic to stay where it's put.  You aren't leaving much room for error.

For small holes (like 2mm) I use a HHE of .15.  Since it acts on the radius I am telling Cura to make the 2mm hole 2.3mm in diameter.  When the print is done I have a 2mm hole.  So for a .03mm hole and an HHE of .15 I would tell Cura to make a .33mm hole.  That is 10X bigger than the starting dimension of .03.

Without access to a set of pin gauges I have no way to measure the hole when it's done.  When I did have a set of pin gauges they started at 0.2mm so they wouldn't have worked anyway.

At any rate as part of this edit I've included a 3mf file.  Interesting thing...Cura found the .02 diameter hole but missed the .03 diameter hole.  I think if fell between the cracks in the STL resolution.

Hole Block.3mf

Edited December 7, 2020 by GregValiant