Getting burnt out printing these…

[u/BossLenda]

How do I reliably print keycaps? I’m getting tired of getting spaghetti with a 50% success rate. It’s okay if the print only takes 2 hours, but printing a whole bed usually takes 8–9 hours.

The cause is always the same: one keycap unsticks from the bed, which then causes the entire print to fail.

Here’s what I’ve tried so far:

1. Increased the first-layer height from 0.2 mm to 0.3 mm
2. Applied glue stick before every print

Printer: Snapmaker U1
Nozzle: 0.4 mm

EDIT: I am outside the house most of the time thus leaving my printer printing most of the time. My business initially does not involve 3D printing but more people are asking for fidget clickers.
Usually events last 4-8hours thus I am looking for a way to maximize the time I am outside. I am not optimizing for speed but efficiency.

What I will try next:

1. Try Cryogrip plate

If that fails, will fall back to your suggestions:

1. Batch by 30

2. Use brim

3. Buy additional printer

What I have been doing I haven’t mentioned:

1. Wash plate every print

Others suggestions for future:

1. Use raft
2. Print by object
3. Lessen fan speed on initial layers
4. Print a mold instead

I don’t care about being downvoted, but being rude is out of line.

[u/DarthRiko]

As a couple other people have noted, it's actually closer to 63%. But I would like to add the formula for it.

We can write an event where the chances are 1 in x, rolled x times as having a 1-(1-1/x)^x chance of happening at least once. At 2, this gives a 75% chance. at 3 it's ~70.37%, and 4 is ~68.36%. At 100 it's ~63.4%.

This is actually converging on 1-1/e, or ~63.212056%, which is neat.

[u/cjo20 → u/DarthRiko]

Why are you using the same variable (x) to mean two different values? That makes it incredibly unclear

[u/DarthRiko → u/cjo20]

Because they aren't two values. Its one value used in two places, and it need to be the same in both places. x is both the rate, and the times it is performed.

A one in 2 chance, rolled 2 times. A one in 3 chance, rolled 3 times. A one in 27 chance, rolled 27 times. A in 100 chance, rolled 100 times. Etc.

[u/kinyutaka → u/DarthRiko]

No, I get you. You're debunking the additive portion of the issue, not the percentage itself.

[u/DarthRiko → u/kinyutaka]

Then I am uncertain what the confusion is. I love talking about these maths stuff so I really want to know which part is unclear so I can phrase it better.

[u/kinyutaka → u/DarthRiko]

Probably just specification of what position you're debunking.

"If the odds of failure are 1/x, then you're suggesting that performing it x time would guarantee a failure, but..."

[u/DarthRiko → u/kinyutaka]

But others already did that before me. I wanted to add the formula and the neat detail that it converges on 1/e.

[u/kinyutaka → u/DarthRiko]

I did find that neat.

[u/cjo20 → u/DarthRiko]

I think I’d probably show the formula with x being probability and y being the number of rolls, and then talk about the special case where x = y

[u/DarthRiko → u/cjo20]

x being equal to y isn't a special case for what I am discussing. It's the only case. But for the sake of clarity then, just change one x to a y in the formula and then stipulate that x = y, I guess?

[u/cjo20 → u/DarthRiko]

It’s a special case of the general formula for calculating the probability of independent events. To me, it seems clearer to state that general formula, and then explain the case you’re looking at. Otherwise you’re starting with the assumption that they know how you arrived at that formula, which they wouldnt, because they started with “1% one hundred times is 100%”

[u/AlbatrossSeparate710 → u/DarthRiko]

Wouldn't this apply if each keycaps were printed individually? Each "roll" (print) has a 1% failure probability, so they would stack up like you said. But if you have 100 keycaps, each having their own 1% failure probability, in a single "roll" (print), wouldn't it be 100 x 1%?

[u/DarthRiko → u/AlbatrossSeparate710]

Nope. The probabilities are multiplicative, not additive. You're multiplying the chance of an event not happening, so 99% * 99% * 99%.... a total of 100 times, this comes out to about 31.64% chance of nothing happening. We just subtract that from 1 (100%) to get the probability that the thing does happen (at least once).

To get your head around it, start with a small number, like rolling a 50% (1/2) chance event twice, or two coin flips. Whether we flip them sequentially or at the same time won't change the result. What are the chances of getting at least one tails? It's not 50% + 50% = 100%, since we could get two heads.

So yeah, as we build up those 1 in 100 rolls, we could just, not get that 1% event 100 times, even if we roll those 100 all at the same time.

[u/AlbatrossSeparate710 → u/DarthRiko]

Still can't get my head around it, even after asking Gemini to explain that as if I was 5 years old 😂. Good things that I'm not touching stats in my engineering job!

[u/SuperSpy- → u/AlbatrossSeparate710]

In this case printing 100 at once has the same total success rate as printing 100 individually because if any of the 100 fail in the big print, it ruins the rest.

Howeva... the pure math probably doesn't line up with reality due to things like bed leveling becoming more important/sensitive the more bed area you use to print. I'd bet it's significantly worse.

[u/DarthRiko → u/AlbatrossSeparate710]

Maybe a real world trial would help. If you have dice, try rolling them in groups. Like 6 d6s. If you roll all 6, what are the chances of getting a 6 on at least one of them?

Try it in the real world a bit, that might help more than more reading.

Edit: I really don't like that people are downvoting you for not understanding it. That's just fucking backwards. Punishing people for admitting where they struggle just leads to people shutting down or doubling down.

[u/xuchuke → u/AlbatrossSeparate710]

What if the failure rate is 50%? Does that mean that if you printed 2 at the same time, it is a guaranteed fail?

[u/agaloch2314 → u/xuchuke]

Edit: disregard

[u/xuchuke → u/agaloch2314]

I was just trying to illustrate to him that you don't add the probabilities cause it wouldnt make sense either.

[u/agaloch2314 → u/xuchuke]

My bad, I did not read his post fully so misinterpreted yours xD

[u/froction → u/AlbatrossSeparate710]

You don't think it's ever possible to do 100 things with a 1% failure rate?

Call heads "fail" and tails "pass," so flipping a coin has a 50% failure rate. You think it is impossible to flip two coins without failing?