Compliant Mechanisms Hack Chat

A little flexibility never hurt anyone

Wednesday, January 26, 2022 12:00 pm PST Local time zone:
Hack Chat
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Amy Qian will host the Hack Chat on Wednesday, January 26 at noon Pacific.

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When it comes to putting together complex mechanisms, we tend to think in a traditional design language that includes elements like bearings, bushings, axles, pulleys -- anything that makes it possible for separate rigid bodies to move against each other. That works fine in a lot of cases -- our cars wouldn't get very far without such elements -- but there are simpler ways to transmit force and motion, like compliant mechanisms.

Compliant mechanisms show up in countless products, from the living hinge on a cheap plastic box to the nanoscale linkages etched into silicon inside a MEMS accelerometer. They reduce complexity by putting the elasticity of materials to work and by reducing the number of parts it takes to create an assembly. And they can help make your projects easier and cheaper to build -- if you know the secrets of their design.

Amy Qian, from the Amy Makes Stuff channel on YouTube,  is a mechanical engineer with an interest in compliant mechanisms, so much so that she ran a workshop about them at the 2019 Superconference. She'll stop by the Hack Chat to share some of what she's learned about compliant mechanisms, and to help us all build a little flexibility into our designs.

  • Hack Chat Transcript, Part 1

    Dan Maloney01/26/2022 at 21:27 0 comments

    Dan Maloney12:00 PM
    OK, let's kick it off. Welcome to the Hack Chat, I'm Dan, Dusan and I will be moderating today as we welcome Amy Qian to the chat. We're going to talk all about compliant mechanisms and flexures, and I assume a little about bendy straws too ;-)

    Amy Qian12:00 PM

    Dan Maloney12:00 PM
    Amy, what is it about these mechanism that you find interesting?

    Amy Qian12:01 PM
    Aside from being very satisfying when they work, I think they are pretty easy to make, sometimes more so that "traditional" mechanisms

    KnownAardvark joined  the room.12:01 PM

    Amy Qian12:02 PM
    they aren't appropriate for all cases when you want a mechanism. But there are lots of cases where they shine.

    pranshu_c12:02 PM
    Hi @Amy Qian ,

    pranshu_c12:02 PM
    How do you start to ideate for mechanisms ?

    Scott Bezek joined  the room.12:03 PM

    Chris Thompson joined  the room.12:03 PM

    Chris Thompson12:03 PM

    Dan Maloney12:03 PM
    I guess I got ahead of myself there. I should have started off with the "tell us a little about yourself" thing

    Amy Qian12:03 PM
    oh hmm, there's usually some day dreaming and doodling involved.

    Amy Qian12:03 PM
    haha, sure thing

    Evilamblonyx joined  the room.12:04 PM

    Evilamblonyx12:04 PM
    Hi everybody

    ciarnoneill joined  the room.12:04 PM

    tca joined  the room.12:05 PM

    Amy Qian12:05 PM
    I am a mechanical engineer by training and mostly by profession, too. I like to tinker a lot (like lots of folks here). Mostly mechanical, although slowly crossing into more electrical things. A lot of my projects are shop improvements, shop tools, furniture, random things around the house, stuff for my car which is a small camper van.

    Evilamblonyx12:08 PM
    When I design compliant mechanisms, I'm usually trapped betrween "Ok, do it right, calculate everything and make a proper simulation" and "Just draw something, print it, and it might work without thinking to much about it".

    So what is your way? Do you make proper engineering in this cases, or more try and error?

    Chris Thompson12:09 PM
    related: How do you prototype?

    Dan Maloney12:10 PM
    Was there anything in your ME training that covered compliant mechanisms? IOW, was there a "Compliant Mechanisms 201" course?

    Amy Qian12:11 PM
    I'm definitely Team Trial and Error. I'm almost never designing mechanisms that operate on the edge of material properties, so it's pretty low risk. Also, most of my flexures are laser cut, so that is pretty quick to iterate

    Ethan Waldo12:11 PM
    My all-time favorite compliant mechanism that achieves sub-micron scale XYZ stages. might give insight in to more scientific process.

    Chris Thompson12:11 PM
    do you use polypropelene?

    Amy Qian12:12 PM
    The heart of compliant mechanisms is beam bending! Which is a heavily covered topic in most mechanical engineering programs (think stress-strain curves)

    Amy Qian12:13 PM
    As for how to turn bending beams into mechanisms, there's lots of great examples out there to build off of. But also, sky's the limit, let your creative juices flow.

    samy kamkar12:14 PM
    @Amy Qian thanks for sharing and your youtube channel, liked some vids and subbed! do you have any suggestions of resources that break down the different effects/areas necessary to design flexure mechanisms? for example, if I had an ideas like yours, "I want a 7-option infinite rotation device [wheel], only moves one way [ratchet and pawl], two binary switches, and the switches to reset upon a single rotation of the device", how would i determine the different components and design, let alone thicknesses based on material type, and durability/determining minimum number of times each piece can be flexed?

    Amy Qian12:15 PM
    I mostly prototype in Delrin or Acetal (both really similar, I think Delrin is a specific type of Acetal) plastic. It laser cuts really well and is not brittle like acrylic. Polypropelene is really melty...

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Dan Maloney wrote 01/26/2022 at 21:29 point


  Are you sure? yes | no

David Gray wrote 01/22/2022 at 15:07 point

Unfortunately, I'll be working during the chat, so was wondering if it would be recorded and available for viewing/listening at a later time?  

  Are you sure? yes | no

Tom Nardi wrote 01/23/2022 at 00:20 point

Unless stated otherwise, the Hack Chats are all text based and the transcript gets posted afterwards. 

Occasionally they are live streamed to YouTube, in which case, the recorded version is made available right after.

So the short answer is: while we'd love to have you there live, we always make sure there is some record of the chat that can be referenced for those who can't make it.

  Are you sure? yes | no

Dusan Petrovic wrote 01/24/2022 at 19:09 point

Hi @David Gray - There is a transcript

  Are you sure? yes | no

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