The Wednesday Update is Posted

This week we’re talking about designing for injection molding!

Oooo, can we pick out colors? I’d love a light one since I must work outdoors and don’t really want to grab onto a super-hot black disk if I don’t have to.

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I want to keep it simple with just one color so I don’t have to keep track of double the part count, but I could be open to a limited run in a custom color down the road if folks are interested. Perhaps just the handle parts if that is a concern?

Someone else expressed that darker colors handle UV light much better and don’t break down over time as much so that could be an argument against a light color outdoors.

Does anyone else have thoughts?

sounds like a question for the material expert.

I’ve also heard that the the black dye in outdoor plastic is UV protection. But
with technology advances, that can be old news.

But if a lighter color is equally good, it may be worth a tiny additional cost
to have something than black.

David Lang

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I didn’t realize injection moulding break even had come down so much. 25 odd years ago when I was inquiring the wisdom was unless you had thousands or tens of thousands of parts it wasn’t worth it. 300 is practically nothing especially if you need multiple copies for a single project. Suddenly you can access the advantages of injection moulding for a project that might only sell 150 or 75 copies.

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modern CAD and CNC makes creating useful molds so much easier than it has been
in the past

In addition, if you really have a small number, you can use a silicon mold
inside a metal shell.

I hadn’t thought of injection molding Delrin. That would be a very interesting
material to make the sled from (would need changes in design based on the
updates over the last few weeks, but having a nice slippery surface like that
would be interesting.

David Lang


Out of curiosity, with about 1400 Kickstarter orders, and an expectation for further production after those are fulfilled, how many units are you planning for when you estimate the life cycle of the molds, @Bar?

As for color, I like the blue/light blue combination in the animation, but I know injection molding doesn’t work that way. :grin:

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Whatever color or material can hold up to the Florida sauna sunshine, I’m fine with it. If I must, I’ll just bring my oven mitts out with me. :grin:


So I went looking for plastic UV resistance and found this:

Carbon black is a widely-used and potent blocker for outdoor applications, offering approximately 2% UV protection. Another effective blocking agent is titanium dioxide, a pigment that serves as a UV screening solution.

From 7 Best UV Resistant Plastics For Outdoor Applications - PlasticRanger

So colo(u)r choice wise that’s either (carbon) black or (titanium) white

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We’re going with hard tooling so the molds should be good for tens or hundreds of thousands of parts. That being said each arm has two sides and each machine has four arms so that’s eight of that part per machine so we’re looking at 1400*8 = ~12,000 of that part already. Geez that’s frightening to think about.

We’ll do an update on the health of the molds at the end of the run. They should be fine for 10x that, but we might eventually wear through one.

Speaking of big numbers, I went to great lengths to make it so that the whole machine only uses one size of bolt to assemble (well almost one kind, there are 8 of a different bolt for the stepper motors, but that couldn’t be avoided) because I spent way way too many late nights counting out bolts into little bags to do that again. As a result we need a LOT of 12mm M3 bolts so I’m planning to order 200,000 of them :exploding_head:


And you won’t have to count them per package, you can just portion them out by mass.

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I stumbled on this video on Youtube a while back, might be relevant. This guy was also tired of counting screws by hand. His stuff looks very well engineered, might be worth looking into maybe making a more limited version if you only have 2 screw sizes to deal with.

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I love his videos! I can so thoroughly relate. For a few thousand dollars you can buy a commercial solution that will count and bag, but I’ve never been quite able to justify it.

Are these cap head / Allen bolts or something different …? Would be nice to also get a couple of spares as with small bolts something always goes missing !!

They are button head allen bolts, there will absolutely be extra included. Each machine needs 78 of them and we’re going to ship 100 so a healthy amount of spares.


Can you get those M3x12 button head screws prepackaged, a bag or box of 100, from somebody that has one of those counting machines and a decent quantity discount?

That is 100% the plan. I’m really hoping to avoid having to count and bag them all myself :stuck_out_tongue:

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