Welcome to Section View! A (mostly) weekly newsletter focused on prototyping and R&D for mechanical and electrical engineers. We’ll be sharing our favorite tools and techniques for designing and building better prototypes, along with an equal dose of inspiration and a pinch of silliness. We hope you learn a little something with each issue while having some fun. Subscribe here.

Tool of the week

This week's tool of the week is a good digital level.  I have a few that I like, for different purposes.  First up is the Mitutoyo 950 Series Digital Protractor.

It has a thick aluminum body that holds up well to regular abuse in the shop, and nice flat reference surfaces that are appropriately sized for most applications. I find it especially useful for setting up 80/20 frame assemblies nicely flat and parallel.

Next up is the Wixey digital angle gauge.  With its magnetic base this is the perfect tool for setting table to blade angles on table saws, chop saws, band saws and scroll saws.  Less versatile, but worth it given how inexpensive they are.  

Last, if you are in a pinch, you can download a bubble level app to your phone. Be wary of absolute accuracy, as not all phones will have well calibrated and trustworthy accelerometers.  Even so, these apps can be quite useful for relative measurements during assembly or testing.

Prototyping Tips

Skip the bends.  The abrasive waterjet cutting machine is one of the most useful prototyping processes available to design engineers.  One of my favorite ways to use waterjet cutting is by prototyping bent sheet metal parts cut from thick materials.  With laser cutting, material thickness is usually limited to ¼” or less, depending on material. Laser cut sheet metal parts need secondary bending and forming operations which require extra parts for dialing in bend allowances, often adding several days to your lead times.  Waterjet cutting allows you to quickly prototype bent parts by aligning bend lines with the thickness of the material and cutting the bent profile directly, no bending operation needed.  This is particularly useful if you don't require precision from the flat pattern features.  For simple mounting brackets you can finish them on the drill press.

Flat and Parallel.  Continuous cast aluminum tooling plate is one of my secret weapons for bench top test fixtures.  It's a super cheap way to get a stiff, flat reference surface that you can build up from.  Unlike wrought aluminum alloys (ex: 6061, 2024) it has a small uniform grain structure and is essentially free of internal stress.  This means you can machine large portions of material without worrying about distortion.  It comes in a variety of thicknesses and most pieces I've received are flat and parallel to within 0.002" (anecdotal).  There are two alloys and suppliers that I recommend; MIC6 by Alcoa and K100S by Alpase.  MIC6 is readily available on McMaster, but if you need larger pieces or more quantity I'd recommend an Alpase dealer near you.  Note: both can be a bit "gummy" to machine.  I like to use form taps instead of cutting taps on these materials.

Designer’s Corner

Lessons from failure. Wahoo is a fitness company that makes indoor bike trainers and related bike training equipment.  Recently they've had some product failures that I think both mechanical and electrical engineers can learn from.  The first is related to an improperly sized keyway designed to transfer riding resistance from a shaft to a hub.  This design/tolerancing issue, coupled with an engineering assumption that the system would not see alternating loads, led to a super annoying clicking noise during coasting on the KICKR trainer.  The second issue is users having electrostatic discharge (ESD) events which fry one of the wheel speed sensing control boards.  Electrical engineers didn't anticipate that the rotating mechanical components would generate ESD problems, especially in dry environments.  Design oversights aside, I'd like to give HUGE kudos go to the Wahoo CEO for addressing these issues head on and being transparent about the engineering solutions.  A refreshing take these days.

Fun Stuff

Surjan Singh has a great blog post where he attempts to weigh his car without using scales.  Pointless? Yes.  Entertaining? Highly.  His method is admittedly a bit flawed, but for me it underscores a crucial kind of engineering creativity that we should all strive for.  Even a basic knowledge of physics can help us understand the world around us at astonishingly high fidelity if we are willing to exercise it thoughtfully.

Free Stuff

We've still got some magnetic drill and tap charts that you can stick on your toolbox, your drill press, or anywhere you find useful.  Just email us at support@fiveflute.com if you want one, and we'll send it your way.

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