Problem with hollow function

#1

Hello,

When i try to hollow objects i often encounter situations were the hollow-function creates holes or at least very thin walls which cannot be printed. This happens even if i use an accuracy of 100%.
See the following picture:

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image.png772x546 101 KB

I uses the following settings:
Wallthickness 1.5mm
accuracy 100%

My plan is to print the parts as a shell with 1.5mm walls and infill.

I also tried to create the hollow with meshmixer - which worked fine - but formware 3d is not able to create a correct infill for parts not hollowed with formware 3d.

Can you please give me a hint how to get a good result.

kind regards
Christian

#2

Hi Christian,

It looks like you are also reducing the hollowed shell ? If so, this causes intersections of course.
Or otherwise using a very rough grid size? -> Where do these very large triangles come from?

It’s hard to tell without seeing the actual mesh-lines or problematic mesh.

Usually it’s a combination of parameters that can make a hollow work properly or wrong.

We use the same underlying technique as in meshmixer to hollow called a marching-cubes algoritm.

Of course i can increase the accuracy parameter in the software if this seems to be a general problem with multiple meshes… that should always solve it.

Elco

#3

Hi Elco,

as i stated above i set the accuracy Parameter to 100% - as i understand this should reduce the grid size.
Furthermore i`m not using the feature to reduce the hollowed Shell.

Is there a different way to set the grid size - as far as i could see the gridsize is a result of the accuracy Parameter.

If you want, i can send you the mesh via WeTransfer because it is quite big. Please tell me to which email address i should send it.

Kind regards
Christian

#4

Hi Christian,

Yes just send it to me over wetransfer. info [at] formware.co

As a matter of fact i’m currently working on an improvement in these algoritms.
What I encountered is that there is a maximum in the current library that we use for these meshes.
That has to do with the maximum array size on your machine; which is 2.000.000.000
If you deduce this to XYZ it means 3sqrt(2.000.000.000) = +/- 1250 cells.
So this has an implication if you use very large models; you can’t use an infinitely small grid…

I"ll check your file; and how much i can stretch the accuracy!
Can be that meshmixer is a bit more flexible here

Elco

#5

Hi Elco,

the STL-File is on ist way via WeTransfer.com.

Since my DLP-Printer has a large Buildvolume (346x194x400mm), i often encounter situationes where i have to print something big, that shoud be hollowed. It would be gréat, if you could improve this somehow.
for my perspective, i would like to set the size of the sampling grid in mm (i.e. 0.5mm as minimum-Value) instead of setting the accuracy Level in percent.
Maybe it helps if you use avaiable cells only for the bounding box of the part and not for the complete build volume.

Kind regards
Christian

#6

Hi Christian,

Sorry i was to late downloading files. It was busy last days.
If you want me to still have a look at it; please resend.

sorry for the inconvenience.

Elco

#7

Hi Elco,

i just uploaded the stl-file again.

kind regards
Christian

#8

thx. looking at it now.

#9

Hi Chris,

I’ve had a look and expanded the functionality with regards to hollowing.
You were right that it was not possible to hollow your model; it was to large+detailed for the current limits that i had set very conservatively to prevent out of memory exceptions.

I’ve expanded the bounds of that is possible within the Memory limits of a pc, calculating backwards.
Additionally The program will now give you a plausible suggestion for the resolution (better name then ‘accuracy’) (green arrow) based on your wall thickness that you set. Of course, you can go much higher. But computational time will increase by third power.

I was able to succesfully hollow your parts with the recommended settings within a couple of seconds.

With regards to reduction; within your specific part this will be tricky. Lots of sharp angles relative to the part size. So reduction will very fast result in thicker or thinners walls… nothing to do about it. So keep it minimal in this case.

If you wish to get a faster result; please split your part into the 2 disjoint parts that they really are and hollow seperately. It will improve the algoritms time by x2.

I’ve included the update in the latest installer.

Elco

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#10

Hi Elco,

thak you verry mucht, i will check it out as soon as possible.

Kind regards
Christian