Shells vs Infill

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OncologyEngineer
Posts: 17
Joined: Tue Jun 05, 2018 1:34 am
Location: Sydney, Australia

Shells vs Infill

Postby OncologyEngineer » Thu Jun 28, 2018 3:26 am

Hi All,

If I am making wide and long prints is there any difference between increasing the number of shells to having 100% infill? I've noticed by increasing the shells to the width of the print that there is minimal direction changes that happens during the infill process. The machine operates so much more smoothly.
Regards,
Onc Eng
N2+ dual standard
Based in Sydney, Australia

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MDVolle
Posts: 51
Joined: Fri Oct 20, 2017 9:00 pm
Location: Fullerton CA

Re: Shells vs Infill

Postby MDVolle » Wed Jul 04, 2018 6:59 am

I really want to see some of the answers on this one!

I have observed the same thing and have also tried printing the same part using each of the different infill styles -

The triangular infill seems to print the "smoothest" while the honeycomb requires the most care and time - but looks so cool...

Cubic also works really well and offers good 3D strength - but triangle seems the fastest/smoothest.

I think that if you print 100% solid, the part will flex more readily without breaking down the internal fill but might not be quite as stiff as a high fill with a pattern.

What I have seen with doing what you are trying - "shells to fill" is that it uses a lot of material and may have cooling issues (which could increase warping).

There really are no completely "correct" answers if you get the part you want at the quality you need... that counts as a win.

OncologyEngineer
Posts: 17
Joined: Tue Jun 05, 2018 1:34 am
Location: Sydney, Australia

Re: Shells vs Infill

Postby OncologyEngineer » Fri Jul 06, 2018 5:08 am

Dear MDVolle,

Thanks for your reply, appreciated. I'd like to have seen other replies as well but looks like thats not going to happen.

I totally agree that by reducing the infill down from 100% it will actually make the component stronger and I believe that the hexagon is actually the strongest (bees honeycomb) however because I'm be taking CT images of the parts I make its not strength of a print that I'm interested in but rather the density of the image that's produced and how that compares with the standard water density that is used medically.

In describing what I'm printing think a breastplate, high and wide but thin (~3-4mm) so, comparing the operation of infill versus shell to create a solid plate, for the infill option if I increase the speed of the print the machine will have a tendancy the move excessive but will do a good job. If I use the shell option, I can speed it up to ludicrous speed (thanks Space Balls) and it's still nice and smooth, and made quicker but the downside is that the estimated weight is less far than the infill version. (Hmm...At this point I think it might be beneficial to actually weigh a print completed using each option).

I'm off print some new prints as well as to find some scales!

Cheers, Onc Eng
N2+ dual standard
Based in Sydney, Australia

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MDVolle
Posts: 51
Joined: Fri Oct 20, 2017 9:00 pm
Location: Fullerton CA

Re: Shells vs Infill

Postby MDVolle » Fri Jul 06, 2018 5:21 am

I'm not sure exactly what you are doing, but it might be of interest that there are a significant number of "filled" filament products -

These range from simple wood powder fill, chopped glass to carbon fiber and even metals - there are even specific metal filaments that were designed for electrical and radiologic shielding as well as the Porolay filaments with a water dissolvable filler to make them more "tissue like". they come in a variety of densities.

Another thought about the process you are describing - you can print 100 percent fill WITHOUT ANY FILL - essentially you have shells and top and bottom layers - you can set the top and bottom layers to actually equal the entire thickness of your part.

Using "All shells" would be like shells plus a concentric top and bottom while using shells plus rectilinear top and bottom layers would also print very fast but have crossed layers for strength.

You can also do the opposite - you can set ZERO top and bottom layers - in which case the infill is open above and below -

It sounds like you are trying to hit specific densities and I would weight things - I was making very light airplane parts and found that the estimated weight was only good for comparison - not an exact final result.

Sounds like an interesting project!

Mark

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Vicky@Raise3D
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Joined: Fri Mar 25, 2016 3:54 am

Re: Shells vs Infill

Postby Vicky@Raise3D » Sat Jul 07, 2018 2:09 am

Too much infill will cause higher internal pressure inside the model and increase the print time of each layer. More print time, more cooling time. Sometimes may cause shrinkage.
Too many shells will cost more time and filament. But it sometimes has better result for structures with small slope.


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