Jello 3D Printer (2013) | Hacker News Reader

Jello 3D Printer (2013)

spritesmods.com

198 pointsPanMan23 comments

it seems that a lot of cheaper CDROM drives position their laser by using a standard, imprecise DC-motor and using the laser tracking as feedback.

Besides cost, the track on an optical disc runs in a spiral, and thus the continuous motion of a DC motor is advantageous because the feedback loop is adjusting the linear velocity of the head instead of its absolute position, whereas a stepper motor would have to make discontinuous jumps. This helps tracking performance and decreases noise (both electrical and acoustical.)

Except that a CDROM wants to be able to seek quickly (say 100 milliseconds) while also read a disc at 1x speed (taking 75 minutes).

Having a DC motor which can run smoothly across 5 orders of magnitude is pretty much impossible. Stiction will always be more than 0.05% of the motors power output.

You therefore have to use a "go-stop" approach based on laser feedback instead.

'Stiction' - the static friction that needs to be overcome to enable relative motion of stationary objects in contact.

As a non-native english speaker I assumed that was typo and had to search for it. I will also assume I wasn't the only one.

> On startup, it'll run the carriage into that switch so it knows exactly where it is. With my setup missing that switch, how does it know where the carriage is? Basically by doing the same thing: it'll run the carriage into the end stop for a good while. If the carriage reaches its limit, it'll slip back and stay there. This gives quite some wear-and-tear on the mechanics and isn't the most elegant solution by a long shot, but for a device that isn't used much and with me not having enough GPIOs left to hook up switches, it had to do.

As I understand it, this is basically the same solution the Apple II disk drives used to return the head to track zero. Owners of the Disk ][ will remember the loud repetitive clicking sound it made at startup. That's the sound of the drive controller moving trying to move the head outward 40 times and hitting the end stop most of the time.

Wow. Makes me wonder how the head could maintain its precision with so much mechanical hammering.

The endstop can be designed with springyness.

Then the process is "move towards the endstop", then "switch off the motor current, if we are pushing against the endstop spring, then we'll be pushed back a step". Repeat this process 40 times.

Nice idea. I guess you can also measure from the coil current that the motor is being stopped or pushed back.

Yup, and some modern steppers have this: https://github.com/bdring/Grbl_Esp32/wiki/StallGuard-Setup-a...

I first thought it prints gelatin. Then I thought it was made of gelatin. Now that I see it prints IN gelatin, that's pretty awesome.

Based on the science described in mark robers jelly pool (where he makes an actual proper size pool of properly set jello/jelly), probably not possible to print proper gelatin. At least not without it being a bunch of tiny particles rather than a congealed clean solid: https://www.youtube.com/watch?v=DPZzrlFCD_I

Or at least, not without it taking forever.

It would have been a cool project, even if he used 8020 extrusion like most similar projects.

Instead, he used salvaged gear for this: He pulled old stepper motors from hard disk drives, and even used an old laptop battery as a power supply. Impressive!

So impressive. Its like an implausible macgyver scenario in an action film.

I love this.

I wonder if buttercream or whipped can be extruded through a needle without deflating. Could be pretty tasty.

With a bit of refinement this could probably be productized. Branded jello shots would be great for bars and events.

the post is quite old (2013)

http://www.printadrink.com/

it seems some company did it. (seen in the comments of the blog)

Hah, I just commented about this story in another story

https://news.ycombinator.com/item?id=26497675

This is so cool! And it's from 2013, thats amazing. A very similar printing method is being explored by MIT's Self Assembly lab, I think they first published in 2017 - https://selfassemblylab.mit.edu/rapid-liquid-printing https://www.liebertpub.com/doi/full/10.1089/3dp.2017.0037

The non-obvious way to greatly speed this method up is to use an array of nozzles and dip them all at the same time. Draw them upward while squirting your resin at the appropriate times and you have a 3D printer that prints as fast as you can move something up and down...

Imagine a sewing machine, but every time it moves up a 3D part is left behind in a binder. A new container is whisked in to replace it and the process repeats. Patent #10,870,239 issued, and more are pending :)

His whole website is an absolute goldmine of awesome projects and hacks. I thought this was really cool: Optical Mouse Cam: https://spritesmods.com/?art=mouseeye

I'm a big fan of this one too: https://spritesmods.com/?art=veccart&page=5

This is the principle behind the rapid liquid prototyping process. Positive displacement of a UV cured crosslinking polymer into a self healing substrate allows building at m/sec instead of cm/min.

If we have grant money left over at end of year, I was planning to work on a bench scale unit.

For those like me who missed it there is a "Next" button that takes you to the subsequent pages of the article.

What difference does it make that it is from 2013?

Just in time for the Jelly renaissance!

The 1950s would love this.

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