Upcoming Functional Print: Hand Challenge

I’ve heard that 3D printing is being used to change lives by allowing the inexpensive design and construction of prosthetic limbs. It’s especially useful for children, who will outgrow prosthetics multiple times during childhood, and those who may not otherwise be able to afford traditional prosthetics. I even saw a 3D-printed prosthetic hand last weekend at Hagley Museum’s Maker Fest (see the 6th picture down). But I only learned today that anyone can produce one of these devices and send it to a person who needs it. The e-NABLE Community is a community of people who do just that, and help match those in need with those with printers. A couple of years ago, a group of 6th grade students in South Carolina decided to participate as part of a class project. They then took it a step further by issuing the Hand Challenge, to encourage anyone with a 3D printer to participate. The challenge is still going strong, and I’ve decided to participate. Since this will be my first one, I’ve ordered a starter kit with all of the non-printed hardware (nuts, bolts, velcro, etc). I plan to start printing parts in the next few days (modulo an upcoming 2 day trip), and I’ll be posting progress as I go.

If you have a 3D printer, I encourage you to have a look. If you know anyone who could benefit from one of these devices, check out the community website; they can help match you with someone who can help.

Functional Print – VW Passat iPhone Holder

I recently decided to replace my old Ford Ranger, which was getting long in the tooth. Working from home, I only drive about an hour a week, so a new vehicle was out. I dislike large trucks, and used small trucks with decent milage are hard to find lately (owing to a lack of new small truck models being offered in the U.S. in recent years). So, I decided to look at cars, and wanting some degree of cargo capacity, I started looking at wagons. I eventually found a 2009 VW Passat Wagon, which is a great little car. However, it’s too old to feature Car Play, and there’s no great place to put a phone holder for using Waze or another turn-by-turn nav app.

It does, however, have a pair of odd little slide-out drawers in the dash, just under the vents, on either side of the hazard lights switch. Here they are closed:

And with one open:

You can rest an iPhone 6 in there, but it is not secure. In the best case it will slide forward, angling the screen up towards the roof, and in the worst case it will become a missile, in the case of a sudden swerve or stop.

After taking a few measurements of the drawer and my phone (in its usual case), I fired up Fusion 360 and took a stab a modeling an iPhone holder to fit in that drawer. The first iteration fit the drawer and the phone, but did nothing to secure the phone:

My second iteration added some small arms to keep the phone in place and removed some of the material in the base behind the phone support, to reduce printing time and cost. It turned out much better:

It’s now a usable phone holder, although I’m planning another iteration with several improvements:

  1. Widen the base just slightly for a friction fit in the drawer. The drawer is lined with some sort of felt, so it should be possible to get a snug fit that isn’t likely to let go in case of a quick stop.

  2. Loosen the arms a fraction. The current model grabs a bit when sliding the phone out.

  3. I’m going to order a right angle Lightning cable and right-angle 1/8″ stereo cable, and try to modify the base to allow them to be semi-permanently installed into the base. The goal is to drop the phone in and have both power and audio connection to the car. The cables will have to hang down over the console for now, but I’m not ruling out routing them behind the dash in future.

I’ll post the new version when it happens, once I track down the cables I want.

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.