Post 1: A Truly Pointless Mechanism

This is a writeup about a fun and truly pointless machine I've been working on. Inspired by the tool changers of CNC machines and (more recently 3D printers like the bondtech IDEX) this is a machine whose sole purpose is to automatically swap one screwdriver bit on my driver for another.

To be clear, if the title didn't give it away, this isn't a useful innovation. It's pointless, but that doesn't mean it can't be fun and maybe be a tool for myself and others to learn some cool things.

So with that said, at the outset of this project I'm setting some rules / goals for this design:

• The design must swap one bit for another in under a second. This is quicker than I could do it when trying to change bits as quickly as possible with my hands.
• The design must house all 64 bits that came in the iFixit driver kit.
• The design can't make use of vacuum / compressed air. This is a practical concern as I don't own an air compressor.

So with these goals in mind, I set out to manifest this machine into existence. A first step for me was trying to break down a list of actions I needed the machine to make so that I could start building out the actual parts and assemblies. The actions to change a bit as done by me, a human, are as follows:

1. Grab the old bit
2. Remove the old bit from the driver
3. Place the old bit back into the driver case
4. Release the old bit
5. Select a new bit
6. Grab the new bit
7. Remove the bit from the driver case
8. Place the bit into the driver case
9. Release the new bit

Written out like that it does sound like a lot, at least to me, the person currently working on cramming all these actions into a span of time shorter than a second. But I'm going to do some optimization now to compactify this set of actions. That way we can get all these things done in approximately the same amount of time that it takes to sneeze or takes Jeff Bezos to earn about $3,750 as of the time of writing this post (he must really be working hard.)

Instead of doing these actions in a nice neat ordered list, we're going to squash pairs of them together to single moments in time.

• T0: Detect presence of driver combined with user selection of a new driver bit (1 second timer starts now)
• T1: Grab new and old bit
• T2: Remove old bit from driver and new bit from storage
• T3: Place new bit in driver and old bit in storage
• T4: Release both bits

By letting some actions happen at the same time I can cut down on how long the bit change takes. And with the individual actions separated into steps in a process, I can start designing the mechanism that will be responsible for making this all happen.

• Mechanism 1: Dual bit grabber — a pair of grabbing mechanisms to grab onto both the new and old bit.
• Mechanism 2: Take / place the bits into the driver and storage.
• Mechanism 3: Storage for all 64 bits.

A little animation to better illustrate the idea:

I didn't come up with the concept for the swapping mechanism on my own. It's largely modeled on the mechanism from a DMG Mori CNC mill, just scaled wayyyy down.