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Question for a mechanical engineer (CAD Specific)

Discussion in 'Off-Topic Discussion' started by soggyBottom, May 2, 2021.

  1. May 2, 2021 at 6:21 AM
    #1
    soggyBottom

    soggyBottom [OP] Well-Known Member

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    I'm not trying to be a mechanical engineer, I just enjoy designing and creating parts as a hobby. Mostly 3d printing but I have done a little using aluminum. For things like gears, I usually just integrate off the shelf parts into my creations. I have no professional experience and no education in anything CAD or mechanical engineering (I'm a software engineer). What are some general concepts that you learned in school that you feel are valuable? Safety isn't an issue here because I'm generally only working with RC cars.
     
  2. May 2, 2021 at 6:33 AM
    #2
    TacoDozer22

    TacoDozer22 Well-Known Member

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    CAD specific?

    Add your filets/chamfers last. Ctrl + s a lot.
     
    creddington likes this.
  3. May 2, 2021 at 6:59 AM
    #3
    soggyBottom

    soggyBottom [OP] Well-Known Member

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    lol yeah thanks
     
  4. May 2, 2021 at 8:05 AM
    #4
    Louisd75

    Louisd75 Well-Known Member

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    Are you doing 2d or 3d? Check your units. I swap back and forth between inch and mm depending on what I'm doing. If you're doing 3d modeling learn how to use the pattern, sweep and revolve tools. They can save a ton of work vs just trying to extrude bits and pieces to make a shape.
     
  5. May 2, 2021 at 8:29 AM
    #5
    Knute

    Knute Well-Known Member

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    CAD is just software.

    The fundamentals behind the design are rooted in several areas of study and understanding.
    Statics
    Dynamics
    Strength of Materials
    Kinematics
    Thermodynamics
    Heat Transfer
    Machine Elements
    Fluids
    ............just a few......

    Anyone can learn to run the software. Understanding and creating a good, durable design is a different process.
     
    rleete likes this.
  6. May 2, 2021 at 10:27 AM
    #6
    soggyBottom

    soggyBottom [OP] Well-Known Member

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    I thought you were joking but after this king about it I don't think you are.
     
  7. May 2, 2021 at 10:53 AM
    #7
    TacoDozer22

    TacoDozer22 Well-Known Member

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    I mean, you asked for CAD specific tips. You didn’t mention what program or your end goal (strength, DFM, performance, DFA or anything like that) so I gave a couple tips that can be applied very broadly. There are literally thousands of books, websites and forums dedicated to CAD stuff but you kinda need to be a little more specific in what you are trying to accomplish.

    Adding your filets/chamfers last is good practice because if you need to change or add features, you’re less likely to blow up your entire model tree if these things are last

    Saving a lot is a good idea because CAD requires a lot of computer resources and sometimes you may add a feature (like a screw thread or a big pattern or big assembly) that may push your computer over the edge and crash the program. I’ve lost hours of work because I didn’t save something.
     
  8. May 2, 2021 at 1:46 PM
    #8
    rtzx9r

    rtzx9r Well-Known Member

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    We didn’t learn much in college regarding CAD... but as noted above it is more related to the function of the gears and what types of forces they will be under. These are taught in a number of the core engineering classes. You could do all this by the book (formulas etc) but you’d be there for weeks. It is more common to model it in CAD and then do some Finite Element Analysis Using those 3D models and the mechanical properties of the materials to understand what forces /stresses are within the parts. You can tweak designs from there and then build and test some prototypes. This usually gets you into the ballpark and then you can adjust smaller things as needed.

    What I’ve learned in 20 years as a biomedical engineer, at least in my experience, is that engineers don’t strive for perfection on the first round. It’s why engineers do so much testing with a high degree of statistics behind it.
     
    soggyBottom [OP] likes this.
  9. May 3, 2021 at 4:24 PM
    #9
    vssman

    vssman Rocket Engineer

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    If you’re interested in 3D printing, that thought process, for me, is different vs machining. For example, when in machining thought mode, I start with a block or round and then remove material to make an item. 3D process is all about adding material. Honestly, most of my last 30+ years has had little CAD need as that’s typically a designer’s role in the industries that I’ve worked it. Engineers focus more on finite element analysis, etc.

    Always remember: F=MA...
     
  10. May 4, 2021 at 7:35 PM
    #10
    soggyBottom

    soggyBottom [OP] Well-Known Member

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    I've been doing quite a bit of topology optimization in my models which I think falls under FEA. The wiki page seems to have a lot of good starting points. Thanks.
     

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