Simple screw counter • Hacker News Board

Re: Simple screw counter

#71

Post by irjustin » Wed, Mar 04, 2026, 2:51 AM UTC

shellfishgene wrote: post #42

rkangel wrote: post #35

Earlier quoted context omitted.

You're weighing the bag. Dispense a load in and divide the total weight by the unit weight and you know how many you've put in. Easier with heavy objects, and needs the variation on weight to be low for the number of items you're dispensing.

Sure, but how do the parts get into the bag?

You grab a "rough amount" and by using weight all you need to do is diff 2,3,4? Ideally 5 and under.

it's very easy to count <=5 visually, but if your package requires 12 nuts, repeatedly counting up to 12 is so stressful the poster built an entire counting machine.

Re: Simple screw counter

#72

Post by interloxia » Wed, Mar 04, 2026, 11:21 AM UTC

xyzzy_plugh wrote: post #54

irjustin wrote: post #19

Earlier quoted context omitted.

> Is this done because of the error in weighing the smallest parts, so they have a margin for error by allowing for an extra 1 or 2? This is a secondary benefit, the primary benefit is if the end user loses/breaks one. That part very well could be show stopper (Ikea 110630 anyone?). Now the end user is stuck - has to call, you have to ship, do you charge? do you give for free? they have to wait. they're annoyed, you'…

Just in case anyone is unaware: Lego does in fact ship single pieces for free, if you lose one.

I tried that the other day when when my kid rebuilt a 3 in 1 set. I couldn't justify 7€ shipping for a 10c part so that the baby orca could have it's dorsal fin. My kid didn't care. I was disappointed.

Re: Simple screw counter

#73

Post by Animats » Wed, Mar 04, 2026, 7:07 PM UTC

ssl-3 wrote: post #55

Animats wrote: post #27

That's very nice. The nut dispenser is very effective. Small, and feeds well. The screw dispenser is starting to run into jamming problems. It will probably start to jam more as the acrylic gets scratched and friction becomes worse. But it's manual and low volume, so jamming isn't a big issue. He's discovered that dispensing is easy, but order from chaos is harder. There's a whole theory of feeder design.[1] There ar…

The nut dispenser is awesome. It occurs to me that the screw counter's main difficulty is in orientating the screws. The machine does solve that (as a product of all the shaking and jostling and doubtless unjamming), but judging by the length of the feeder tube it's not a very fun step. And the end goal isn't to have screws that are each oriented in exactly the same way, but instead to have a specific quantity of scr…

> Perhaps by using a sorter that puts the screws in a line, axially, without a preference for heads-first or threads-first orientation?

Here's a vibratory bowl feeder doing exactly that.[1] This is the industry standard way to solve this problem. Look what happens once the screws are lined up without a preference for heads-first or threads-first. A very simple slotted rack gets them all from horizontal to heads-up. As is usual with such feeders, if something doesn't land where it's supposed to, it falls back into the bowl for another try. That's the anti-jam mechanism.

3D printing vibratory bowl feeders works.[2] Useful for when you need to handle thousands, but not millions.

This is more scale than the clockmaker needs, though. Unless his business scales up.

[1] https://www.youtube.com/watch?v=kIPNdrbSYM4

[2] https://www.youtube.com/watch?v=ECx6L7z0T4Y

Re: Simple screw counter

#74

Post by shellfishgene » Thu, Mar 05, 2026, 9:29 AM UTC

irjustin wrote: post #71

shellfishgene wrote: post #42

Earlier quoted context omitted.

Sure, but how do the parts get into the bag?

You grab a "rough amount" and by using weight all you need to do is diff 2,3,4? Ideally 5 and under. it's very easy to count <=5 visually, but if your package requires 12 nuts, repeatedly counting up to 12 is so stressful the poster built an entire counting machine.

Yes, the question is how exactly you grab a "rough amount"? If you need 4 parts in each bag, is it really much easier to construct a system that can dispense 4-6 parts, than one that can dispense exactly 4?

Re: Simple screw counter

#75

Post by irjustin » Tue, Mar 10, 2026, 4:37 AM UTC

shellfishgene wrote: post #74

irjustin wrote: post #71

Earlier quoted context omitted.

You grab a "rough amount" and by using weight all you need to do is diff 2,3,4? Ideally 5 and under. it's very easy to count <=5 visually, but if your package requires 12 nuts, repeatedly counting up to 12 is so stressful the poster built an entire counting machine.

Yes, the question is how exactly you grab a "rough amount"? If you need 4 parts in each bag, is it really much easier to construct a system that can dispense 4-6 parts, than one that can dispense exactly 4?

Sorry i completely missed this. If you don't see it, it's okay - I probalby miss any replys going forward.

Being upfront, I have no idea what I'm talking about. Just some arm chair engineer.

The poster needed 6 parts which is JUST into annoying. My personal thoughts are what they need isn't dispensing but alignment. Thinking deeper I can agree that weight might not the most efficient here.

They're building the aligning and dispensing tool but I argue that's over engineering the problem. If it's aligned it's VERY easy to count 6 via a mark along the track and just push it to the end against your finger and based on the mark you know you have exactly 6.

To me the hardest part to make "just work" is the dispensing, but if you remove that it becomes a much easier problem. There's enough sales volume, you can make a vertical fixture that is a stack of fixed aligning tracks. Your fingers become the dispenser. Sweep and move to the next track.

Just random thoughts.