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Magnet Update! Getting A Grip On Grips

By June 15, 2021 News

We’re back with another update on our progress with the Magnet. The photo above is our latest production sample that includes a few stealthy but important improvements.

If you look closely from the side, you may be able to spot a subtle tweak we made to the “tool”, or mold, between our last update and this one. See if you can spot it:

As you scan your eye down the rubber grip on the left upright, you’ll notice that it’s actually thicker at the top than the bottom. This results in a tiny air gap toward the base, where you can see a little daylight peeking through. What gives?

Tale of the Taper

This tiny gap is the result of a 1.5mm taper that we carved right into the mold. And when we add a phone into the Magnet, you’ll see why:

When the phone is installed, you’ll see that the left upright, the one that moves, is no longer perfectly parallel, but actually tilted a bit to the left. This is the result of a small but unavoidable amount of play in the sliding mechanism. But… if you scan your eye down the rubber grip like we did before, you’ll notice that the grip itself is now more parallel than before, fitting more flush against the phone for more grip.

So that’s the trick. In an ideal world, you’d have as little splay as possible, so the uprights would stay straight up and down, and rest perfectly flat on the face of the phone for maximum grip. But once you start making actual parts, the tighter you make those sliding tolerances, the Magnet tends to stick and not slide smoothly. In this case we’ve made the tolerances as tight as we can while still allowing the Magnet to open and close smoothly. To offset the small amount of splay, we added that 1.5mm taper to the rubber, which just about exactly cancels it out.

Getting A Grip on Grips

Another nice improvement with this sample are the rubber grips. You may recall that we were having some bubbling issues in the rubber as we attempted to figure out the temperature and cooling time. After a few tests, the rubber faces are now just about perfect:

That little dot in the middle of the grip is the injection point where the rubber flows in. On the earliest samples it was a bit of mess, misshapen and bumpy. But everywhere around that dot is now nice and flat. Even though you’ll never actually see this dot in the assembled device, maintaining a smooth surface is crucial for maximum grip on the phone.

We’ve been using this for a few weeks now, and between the smoothed-out grips and the new taper, this is the best-performing Magnet we’ve made so far. With any luck, these are the last mechanical tweaks we’ll need to make.

Drastic Plastic

So what’s left? Just fire up the presses, right? Almost! After doing just that in a test batch over the past couple weeks, the factory was getting an unusually high reject rate, where the plastic itself didn’t flow or mold smoothly.

So they’ve decided to do a test run with a different kind of plastic, Polypropylene, to see if it produces a higher percentage of usable Magnets. (The original samples were run with ABS, a more rigid type of plastic.) So we’ll see how this goes. They ordered the new material about a week ago and should be running this new batch any day now.

We’d reaaaallly like our next update to include a photo of a final production sample, so we can hit the gas pedal and start cranking them out. We’ll let you know how this goes. As always, thanks for your patience as we navigate this unfamiliar process, and thanks for backing the Magnet!

Top Comments

  1. Avatar for Troy Troy says:

    Some nice incremental improvements here, including adding a 1.5mm taper to the rubber grips to offset the unavoidable play in the sliding mechanism.

    This play, or what we’ve been calling “splay”, is when the the sliding upright tilts out a little bit, causing the surface to no longer be parallel with the phone. It was always an issue with the 3D-printed parts, where if we made them too tight, there would be less splay, but the Magnet would jam when you tried to open it. Or if it’s too loose, then you can slide it open really easily, but it won’t grip the phone really snugly. So what we would do is print a few of them and then get out the files to start sanding away the sliding parts until they slide better. No two Magnets were ever really the same.

    So far, the production samples have performed much better in this regard. The tolerances of injection molding are just much more repeatable from unit to unit, so there isn’t this crazy variablity that you get with even very expense 3D printing like Shapeways. They slide pretty much perfectly with no sanding, but there is still some splay which prevents a really flat grip on the phone. The 1.5mm taper addresses that pretty well. Just a gentle squeeze on the uprights to snug up the grips on the phone, and it stays in there pretty firm. This most recent sample is definitely the best-gripping Magnet we’ve made so far. I’d be fine with this level of performance in the final production Magnet.

    The test run they’re doing on the new plastic, that’s more of an X factor. No idea what they’ll discover but hopefully it’s good. We’re pretty much there on the mechanical tweaks and it works pretty well. They just need to find a plastic where they can reliably reproduce the tolerances from Magnet to Magnet.

  2. Looks like yous have thought of pretty much everything! Nice work.

  3. Avatar for jptk jptk says:

    Great stuff, thanks for the detailed update. :love_you_gesture:

  4. Hi, can I still order one? I missed the Kickstarter-campaign :frowning:

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