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Comment by Jerry2 | Hacker News Reader

I've looked at the examples of things they cut with that thing [0] and the amount of time and abrasive needed to cut even a single knife blade out of steel is quite shocking:

>Cut time: 118 min. | Abrasive used: 39 lb.

I presume this abrasive sand, garnet, is non-recyclable? Yikes!

Imagine how many bags of sand you'd need to cut a whole sheet of metal!

[0] https://www.kickstarter.com/projects/1294137530/the-first-de...

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AFAIK garnet isn't recyclable, but it's also pretty much just sand (non-toxic, though the material you're cutting might make the resulting slurry something to avoid).

To put the amount of material in perspective, the large table waterjet in the shop that I work at recently had its annual cleaning, during which over 1.5 tons of garnet mud was removed (we do use it regularly, but we're far, far from a high-volume shop). To cut a single knife blade ours would probably use less than a pound of garnet, but then again our machine cost several hundred grand.

As for time, that is indeed pretty high, but it's comparable to what you'd expect from commercially-available 3D printers. DIYers wouldn't be discouraged there.

For me, the biggest reservation is that 4mm of steel seems quite shallow, if indeed that is the maximum depth.

(Note that I just started working at this machine shop two months ago, so I'm hardly a real expert here. :P )

Thanks for an excellent overview and for confirming my assumptions. I've seen commercial waterjet machines in action when I visited a tool factory when I was in high school and those machines were amazing... they were cutting through plates of steel like it wasn't even there.

As for garnet, yeah, it's sand but it's finely meshed and I'm guessing you need a strongly abrasive sand. Unless you're near some beach with that type of sand, you'll have hard time finding something optimal.

I just don't see why any DIY-er would want this want this machine given how expensive and time-consuming the whole process is. Unless you're rich or working for some rapid-prototyping place, you're much better off paying commercial guys for cutting your blanks for you. Anyway, feel free to correct me if you think my reasoning is wrong since I'm no expert.

  > you'll have hard time finding something optimal

I wasn't intending to imply that one could use any old sand in the machine, only that disposal shouldn't be unduly bad for the environment (unless your recycling comment was intended to focus on the economic aspect rather than the environmental aspect).

Taken in the context of being a first-generation device, I don't think this is a bad product at all. First-generation 3D printers were way less polished than this appears to be (though of course I haven't used it myself). It remains to be seen how much maintenance it will require, but even current-gen 3D printers seem to manage to break down once a week or so, so again I don't think DIYers will be deterred there. :P And in particular, I think hackerspaces with a decent amount of cash but with scant floorspace might find this product compelling (our waterjet is easily the single largest tool in the shop). This might also appeal to folks with personal shops who can't justify the enormous expense of a full-size waterjet, who might purchase this out of sheer novelty. AFAICT it won't appeal to rapid prototypers, because prototyping in acrylic (or wood) via a laser cutter is already so much faster than waterjetting (unless you need your prototypes to be metal, in which case you already own a full-sized waterjet).

TL;DR: empowering DIYers is good, even if initial appeal is limited, and hopefully subsequent generations of the device will improve the economics.

You can basically use any old sand as long as it's meshed within spec for your machine depending on what you're cutting.

If you use silica sand, you get silica dust and silicosis.

With garnet, you can recycle it on site and their some companies that will buy and recycle your abrasive to resell. That being said, garnet sand is cheap as shit and it's more expensive for most shops to recycle. I've heard that factories making backhoes and the like cutting lots of like 1/4 inch plate will because they're using just so much that it makes sense to recycle on site. All that being said, the sand will go round and be a less effective abrasive after a few uses.

According to their specs page, the 118 min was for blade, bolsters, inserts, etc, for a total of 9 pieces. So, figure maybe 45-60 mins for knife blade itself? Still long but less so...

It apparently can be recycled:

http://www.thefabricator.com/article/waterjetcutting/reusing...

(I guess it won't be worth setting up recycling for most users of this machine)

They say $0.30-$0.60 a pound (and I see lower prices suggested elsewhere), so the cost isn't astronomical.

That's an interesting link! However, like you said, you need specialized equipment to recycle it so this is not something that hobbyists or users of this machine will use since the cost will probably be more or less the same as the cost of a new bag of sand.

And you're still left with the huge amount of time it takes for it to cut steel. Commercial waterjet systems can cut that blade I mentioned in seconds. Wazer took 2 hours.

I think all these hobbyists and small shops that are considering this technology should beware of the cost. Suddenly, that seemingly high cost of commercial waterjet providers doesn't seem that high at all to me!

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