Functional Print – Resistor Bending Guide

Over the past 6 months or so, I’ve started to use Reddit on regular basis. One of my favorite recent finds is the r/functionalprint subreddit, which features practical items made with a 3D printer. Contrast this with r/3dprinting, which features lots of calibration prints, printer upgrades (many themselves 3D printed), hardware and software reviews, folks asking for help, etc. r/3dprinting is a great subreddit with lots of helpful folks, but it’s mostly about the practice of printing, and not about what we print. r/functionalprint, on the other hand, is about useful things made with a 3d printer. It reminds me that having a 3d printer isn’t just about having a 3d printer, it’s about all the things such a device enables.

I’ve had my printer now for nearly a year. It has gotten a fair amount of use, but it has also set unused for months at a time. Often, it has printed its own upgrades parts, or calibration cubes, or other objects focused on making the printer better. But once the printer is all dialed in, then what? Aside from a stretch of playing with 3D printed terrain for tabletop gaming (more on that in the future), I’ve really on focused on the practice of printing, and not the rest.

So here’s something that I designed (Fusion 360) and printed on my Monoprice Maker Select V2 last night:

It’s a Resistor Bending Guide. A what? Well, I’ve recently designed a through-hole Display board PCB for another project (more on that in the future) which I had made at OSH Park. It contains several 14- and 7-segment LED displays, so it needs a number of current-limiting resistors. The ones I spec’ed are quite small, and trying to bend the legs at just the right places to get them to sit nicely on the board was quite a chore, so I designed this as a template for bending them to size. The first one was twice as tall, but the other dimensions weren’t quite right, so I made it shorter for faster prints while iterating; once I had the rest of the dimensions correct, I found that the shorter guide was perfect for pre-trimming the leads to a shorter length before inserting into the PCB. Here are some action shots to show you what I’m talking about.

Tiny little resistors.

The divot in the top of the widget is just the right size to hold the resistor body.

Just fold the legs over to get the correct spacing for the holes on the PCB. The bottom of the tool is a perfect place to trim the leads.

Here’s one that’s been bent and trimmed, and is all ready for the PCB.

And here it is, at home on the PCB. With 66 per board times 2 boards, plus a different display board that will need a similar number, this little tool will save more time than the ~hour it took me to design, print, and iterate it. Quite functional, that.

Finally, here’s a closeup of the design in Fusion 360. The detail is a bit finer than my printer can reliably reproduce, hence some iterating, but it gets the job done.

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One Response to “Functional Print – Resistor Bending Guide”

  1. jclark.org - Learning through Failure: KiCad Edition Says:

    […] with success after neatly soldering 66 resistors to a my new PCB last night with the help of my resistor bending guide, I thought I’d be showing some shots of my new LED display board in action. After all, this […]