Cliff Smyth: Discussion on Infill & Shell Parameters Crucial When Planning a 3D Print

Share this Article

bookWhile there are many details to consider when 3D printing, from the inception of a workable concept to all the aspects of digital design and the process of 3D printing, strength in material is a biggie. You surely don’t want to go to all that trouble just to have your print fail or cave later.

Cliff Smyth, author of Functional Design for 3D Printing, wrote his informative tome to help 3D printing hobbyists prepare ahead of time in order to make the most durable designs possible.

One aspect of 3D printing that doesn’t sound like nearly as much fun as whipping up a 3D design and seeing it print, but is very important to consider, is that of infill and shell parameters. These items have direct bearing on your 3D print, but vary with each design depending on material and how they will be 3D printed and used. It’s recommended–and just good common sense–that you plan to do some testing if your items are considered ‘critical.’

Smyth's test model 'in CURA at 25% and 75% infill, 2 layer (0.7mm) shell'

Smyth’s test model ‘in CURA at 25% and 75% infill, 2 layer (0.7mm) shell’

In his testing examples, Smyth used a standardized 6 mm cantilever beam. Load-carrying capacity was tested with a white plastic bucket bearing a ruler. Basically the 3D printed piece load beam being tested was used to lift the bucket, with its stress and durability being measured.

Four load beams were 3D printed using the same digitally designed 3D model. Smyth directed them to be sliced at varying settings for the purposes of testing, with Cura as the slicer. Parameters were, according to Smyth, adjusted with 3 beams bearing a .7 mm shell and 25%, 50%, and 75% rectilinear infill, as well as one beam with a 1.05 mm shell at 25% infill to be used as comparison.

As water was added to the buckets, stress on the beams holding them up was noted.

“Failure modes were universally in tension, with failure beginning in the upper (stressed) skin, propagating as a tear downward, as expected,” said Smyth.

Infill_Shell_Parameters_031-1024x693An interesting point was that increased flexibility seemed to offer added strength, although the beam that was the weakest in load capacity was the one “deflecting further than the others before failure.” The outcome would be:

  • Less infill creates more flexible parts
  • More infill creates stronger parts – greater gains at 25-50%

“The material used/strength relationship of the reinforced skin vs. increased infill tests were very nearly linear with this model,” reported Smyth. “This was surprising, as I had anticipated that increasing the skin thickness would yield more strength per unit of plastic than increasing the infill. I’m not sure why.”

The tests yielded results that are fairly simple, but solid guidelines for 3D printing hobbyists to keep in mind as the amount of infill density is directly affiliated with strength/flexibility. To find the binfill v strengthest infill density possible for the 3D model at hand, users must consider geometry, infill pattern, and orientation.

“If your 3D printed part will have to withstand tension or compression loading in the Z-Axis, it will probably benefit from much higher infill densities, for example,” states Smyth. “An interesting observation was that the lighter infilled parts were able to accommodate more bending prior to failure, even though they failed at lighter loads.”

This also leads to a ‘downloader beware’ caveat. If there aren’t detailed printing specifications created for a 3D model and the user creates variances with Cura, outcomes could be very different from what the designer of an original file experienced or intended. Obviously, this is where testing comes in as well, if you don’t have detailed instruction files and know that you intend to tinker with a design.

Discuss these findings in the 3D Printing Infill and Shell Parameters forum thread over at 3DPB.com.

[Source: 3Dprintingforbeginners]
one

25% .7 mm shell test

Infill_Shell_Parameters_061-1024x635

Share this Article


Recent News

PEAK Launches Alien Beast 3D Printed Shoes for Limited Sale

Arevo Announces New Aqua 2 Carbon Fiber 3D Printer, $25M in Series B Funding



Categories

3D Design

3D Printed Art

3D printed automobiles

3D Printed Food


You May Also Like

Nexa3D Acquires NXT Factory, Introduces Eco-Friendly 3D Printing Washing Solvent

While Nexa3D may specialize in manufacturing super-fast stereolithography 3D printers, the company has been branching out recently, and narrowing its focus on the materials side of things. It launched the...

Featured

DyeMansion Secures Additional $14M in Series B Funding from New & Existing Investors

German company DyeMansion is known for its coloring and post-processing equipment, such as its three-step Print-to-Product workflow geared toward industrial 3D printing environments. Now, in order to continue transforming and...

T3D Announces New LCD-Based High-Speed 3D Printing System

Taiwan 3D Tech, also known as T3D, is a startup spin-off from the National Taiwan University of Science and Technology (NTUST). Headquartered in Taipei, the company was officially founded in...

3DPOD Episode 32: Tuan TranPham, Arevo

Tuan is known universally by his first name alone. Like Madonna and Beyonce, everyone knows hi by just that one name. In Tuan’s case his fame is 3D printing specific...


Shop

View our broad assortment of in house and third party products.