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  1. #1
    3D Printer Noob
    Join Date
    Jun 2019
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    How do you know your printed parts will be strong enough?

    I am so amazed here by all of the functional prints. I'm wondering if anyone has a method here for checking before a print to see if it will handle the weight or stresses of use. Do you do test prints to check specific cases? Do you have rules of thumb? Do you do finite element analysis? fetLife itunes
    Last edited by hardus77; 06-03-2019 at 05:09 PM.

  2. #2
    Super Moderator
    Join Date
    Nov 2016
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    Welcome to the forum hardus77!

    Great questions and very relevant. Answer is easy... no. But that deserves a huge caveat.

    The caveat is that we know that our prints are mere shells where not even the infill offers much support as it is offset from the walls.
    One thing to consider when approaching a design is the layer orientation. Each layer on its own provides the strongest part of the print.
    Second is layer adhesion and third is wall "proximity" (they rarely merge).

    One thing to be sure of is the app we are considering. The limited option in Cube3 are greatly expanded in CubePro providing a huge opportunity for design considerations. But CubePro is a different beast in how it slices and Cube3 and CubePro depart quickly on consistency of the resulting print. I find myself all too often designing to the printer, which I know is bad form for a designer. But it is basically a "unique case" for either platform.

    Next is the material properties. PLA is a great crystalline structure that makes good solid prints. But it really doesn't do well with stress. Stress risers and sustained deflection will take a set and often exceed the material properties within a relatively short period of time. ABS is soft and gummy which makes it difficult to get any lasting elastic properties. PETG is a little better in many respects but still has design limitations such as cold-welding two PETG parts that interact and inherent flex. Basically the right material for the job.

    I do put in features that enhance strength such as additional walls, voids, wall perforations, and many others to force specific design elements. Managing elements like wall thickness to the actual minimum values or values that result in good close fitting wall elements have proven very useful.

    Considering I do work with design that are near the hotend, there too one needs to consider softening of the material or how expansion is managed. The seam in the parts often create a fulcrum for thermal expansion, for instance. There are tricks to manage that type of thing too.

    So I might be painting a picture of a wild west approach. That wouldn't be far off. But I will add that there are different types of printers as noted above. CubePro, to me, is a technical printer. You can design line to line and parts will fit. Walls too thin are removed by default and parts always come out small to ensure this fit. On the other hand, I've been working with the Cube3 for 2 years now and it is a true hobby printer as most FDM printers are. It just makes the best of what you throw at it. A few tweaks and the part will some out somewhat consistently out of all Cube3 printers. And when you put the part on Thingiverse, you find that most people will get similar results. Not the case with CubePro. I don't know of any other slicer that does what CubePro does.



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