MakerBot Industries

First draft on the left, second draft on the right

I’d like to address some comments to the prior two posts.  The first post was essentially about identifying a problem that could be solved with a 3D printer.  In this case, it was the cracked plastic case for my mom’s car key fob.  The second post was about one method for measuring and documenting measurements in a meaningful way.  Basically I trace out the parts on a sheet of paper and draw in arrows indicating the dimensions.

@Mark wanted to know why I was breaking up the posts.

Well, originally I had intended to live-blog the process of identifying, measuring, designing, and printing the solution.  This was not to be for a variety of reasons.  Instead I opted to break what would be a very very long post into discrete sections. ¹²

@Alex Guichet wanted to know when you’d get to see the results and if this was just going to be a teaser.

I’ve broken the entire saga into four posts.  You’ll get to see the finished product at the end.  Promise.

Draft, the First

From the photo above you can see the first attempt on the left.  There were a number of deficiencies in this draft that I didn’t really think about until I was actually holding the part in hand.  In my zeal to measure the electronic-beeper-thingie and the metal key, I had completely forgotten to measure or design the less critical part that allows you to put the darn key on a keyring.  Next, the metal part that is the actual key is quite a bit thinner than the electronic-beeper-thingie.  As such, there needs to be a raised section that is only “key”-width rather than “beeper”-width.  In this first version you can see that there is no such raised section.  I also failed to include a hole for the small screw that holds the key in place and both sections together.  In this draft the two parts do not actually fit together, they are both just flat pieces that do not interconnect in any way.  I also noticed that I made the entire enclosure slightly too big vertically.  Just one more thing to tweak in the next version.

Once it was in my hand, I decided that the next version would allow a portion of one part to fit into a section of the other.  Just looking at the finished product was enough to help me realize all of these deficiencies – that’s why I didn’t even bother to clean the part up. 

Onwards and upwards!

Draft, the Second

From the photo above you can see the second attempt as the two parts on the right.  While these parts were much more suitable than the prior, there were still some issues to work out.  I included a section for the keyring, a hole for the screw to hold the key in place, a lip on one side and a bevel on the other so they would fit together, and I reduced the interior height by 2mm to reduce the extra room.  The parts fit together well – but came apart relatively easily.  I decided the next version would have an even larger lip.  It turns out that a reduction in 2mm was too much, since the electronic beeper just barely kept the parts from fitting properly.  Increase by 1mm.  I decided all of the buttons needed just a little more clearance on each side, so I gave them all 0.4mm more space.  I made created a recessed section for the screw head to disappear flush into the top section once installed.  Lastly, I also widened very slightly the two walls on either side of they key, since it was a very tight fit.

The benefits of drafting

Imagine you had to program by punch card.  Get one punch wrong and that card was toast.  Get one punch card wrong and your whole program was toast.  Sure, you could double, triple, and quadruple check your program by inspecting every punch and the order of every card…  But it’s not a very efficient use of time.  For modern programmers there is little penalty for just taking a chunk of code and firing it up.  The most common worst case scenario is an error code directing you to where the problem might exist.

Now, if software guys can try out a draft of code without any significant penalty, why not hardware guys? ³  I don’t need to get everything exactly right the first time – and I might even find a few improvements along the way.  With an investment of about 20 minutes of unattended printer time and $0.20 of plastic each I got to try out two interim designs – and improve my final design.

Up next:  The final results!

Posts in this series:

• MakerBot Hero:  Car Keys I
• MakerBot Hero:  Car Keys II
• MakerBot Hero:  Car Keys III
• MakerBot Hero:  Car Keys IV
• MakerBot Hero:  Car Keys Epilogue

1. Like Dave Durant long post. [↩]
2. Dave, I kid because I love! [↩]
3. And, for that matter, why not tinkerers, makers, hackers, repair people, and dads? [↩]

Tracing the key fob

The last post covered my decision to remake/repair my mother’s car key. Frankly, I’m surprised I haven’t been fired from this job for not having fixed this problem immediately. In my defense, from the moment I learned of this issue I dropped everything to begin working on it.

A critical step to printing a replacement part is measuring your existing parts to make sure the replacement components will fit well.  I find the easiest way to start doing this is to simply trace the existing parts on a white sheet of paper.  Once this has been completed, I flesh out the “sketch” a little and draw in all of the measurements.

Marking the dimensions of the key fob

Once the measurements have been taken down and associated with the relevant areas on the existing parts, I like to create a digital representation of these parts.  Doing so allows me to use those existing components as a basis for developing the replacement parts.  With printing tolerances, a little ooze, and some very minor Z axis wobble I find that 0.5mm – 1.0mm room on all sides is sufficient to develop parts that print and fit together nicely.

Next up:  A first draft

Posts in this series:

• MakerBot Hero:  Car Keys I
• MakerBot Hero:  Car Keys II
• MakerBot Hero:  Car Keys III
• MakerBot Hero:  Car Keys IV
• MakerBot Hero:  Car Keys Epilogue

Key fob, apart

My mom had been a public school teacher for all of her working life until she retired several years ago.  It was just before she retired that she bought herself a nice new car.  Yesterday she came to visit and she handed me her car keys to grab something from her trunk.  I was horrified at what I saw.  Her car keys, which have a built in electronic car lock/unlock remote, was wrapped in cheap packing tape.  On top of that, it was old packing tape.  So old that it had become stringy and oozey.

I asked what happened only to be told that while at her school she had dropped her keys which immediately cracked at the point where the metal key met the plastic housing for the electronic guts.  The school maintenance worker had kindly offered to fix it up the only way he could – with public school¹ packing tape.

This conversation ensured:

• MakerBlock: “How long has it been like this?”
• MakerBlock’s mom: “Oh, a looong time.”
• MakerBlock: “How long?”
• MakerBlock’s mom: “About two years.”
• MakerBlock: “Two years?!  Mom, you do know I have a machine in the other room capable of just making you a new plastic housing for your keys, right?”²
• MakerBlock’s mom: “Oh, that never occurred to me.”
• MakerBlock: “This is just unacceptable!  You can’t live like this.  I’m making you a new one.”

With the careful application of a utility knife to remove the packing tape and precision screwdrivers to take out the one lone screw, the key fob revealed its secrets, as depicted above.

Next:  Designing the replacement

Posts in this series:

• MakerBot Hero:  Car Keys I
• MakerBot Hero:  Car Keys II
• MakerBot Hero:  Car Keys III
• MakerBot Hero:  Car Keys IV
• MakerBot Hero:  Car Keys Epilogue

1. Read: cheap [↩]
2. 3D printers has essentially been all I can talk about, or write about for that matter, since hearing about them for the first time in April of 2008. [↩]