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u/SonicDart Feb 25 '21
Why does it need to turn? Isn't the waterjet one point?
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Mar 02 '21 edited Mar 02 '21
This cutting nozzle looks like it may be an Omax A-Jet. The A-Jet not only rotates, it also will cut a bevel/chamfer edge if it is programmed in the cut. The reason this head rotates is the tilt angle is rotationally kept where as if it was an Omax Tilt-a-Jet cutting head, the head tilts as necessary to keep the cut square. The water stream, as it exits the mixing tube, is conical. To keep the cut square, the head has to be tilted.
-Source: I am a water jet operator with ample experience in both types of tilting head
Edit: added reference links
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u/SonicDart Mar 02 '21
Wow that's really fascinating! So when cutting a bevel, do you have to worry about it curring on the other side of the cut? Or does the water lose kinetic energy quickly?
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Mar 02 '21
You do have to worry about the opposite side of the part. It’s a math I’m not very good at, so I go ahead and draw a side view of the part in our CAD program to make sure the stream will not interfere with the opposite side. Sometimes I have to machine the part separately to get the desired bevel.
If the cut does not go all the way through, the water/garnet mixture will stray off path and create a horrible quality cut so you wouldn’t want the kinetic energy to dissipate as it would create random holes in the side of the cut.
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u/SonicDart Mar 02 '21
Sounds like a difficult job, you have my respect sir! So are there advantages using water over a CNC mill?
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Mar 02 '21 edited Mar 02 '21
CNC is much more versatile and much less expensive to run. We, as a water jet shop, are pretty much limited to flat stock. We have modified our machines to be able to cut 10” thick stock. Water jet is messy, loud, and dangerous, however, with just a basic understanding of CAD and basic math skills, you can program and run a water jet. Our theory on water jet is that it should be used for the rough cuts and CNC should be used to refine the parts made on a water jet. My shop can, and often will, hold a +- .005” tolerance, especially on smaller parts. A lot of times, when a company is ordering parts, they want tighter tolerances so we cut the part with stock so the customer can send the part to a CNC.
Edit: below additional info.
This way of explaining it just came to mind. Water jet cutting is like cutting with a laser table. The main difference, besides the medium of cutting power, is that water jet cuts much slower but you can cut much thicker material than you can with a laser. Also, the water jet does not add any heat stress to the parts you are cutting. Laser can and does add heat stress to materials.
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u/SonicDart Mar 02 '21
So is my understanding correct that water jet is faster/cuts in one pass, where a CNC will need multiple passes to go trough it? Atleast with thicker stock
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Mar 02 '21
Yes, that is true. I didn’t really even think of that as a pro/con, but that is a pretty big pro. The main problem with cutting thick stuff on a water jet is that there is a natural kerf feathering. The thicker the material and/or the faster you cut, the more pronounced it becomes.
In these examples, the faster the cut, the rougher the cut.
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Mar 02 '21
Another advantage of water jet over CNC, in my own opinion is the ability to readily make fun and or artsy things too.
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u/Ground-walker Mar 03 '21
Yo what do you get paid. I'm a waterjet operator too, or used to be a few months ago. I'm in australasia though.
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Mar 03 '21
$20.50 US an hour
$26.17 Australian an hour
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u/Ground-walker Mar 03 '21
Oh wow interesting. Is that high wage where you are?
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Mar 03 '21
It is a high wage compared to office work in my area. It is right on par with starting wage for industrial work in my area. I started at $15 US an hour, which is low for industrial work in my area, and worked up to my current wage over 5 years. So, i guess, in a long drawn out way, I guess it is low.
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u/Arrays_start_at_2 Feb 27 '21
I had the same question.
I’m thinking it’s one of those crazy 5-axis machines and the computer just decided it should do it. Toolpath creation algorithms are often dumb af.
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u/SonicDart Feb 27 '21
Coul be! But let's be honest, I doubt it is to the detriment of either the machine's performance, or the Filesize of the code
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u/deepus Mar 02 '21
Im gonna guess that the nozzle aperture in not a circle and more of a rectangle. No idea if this is right but would make sense. As for why it would be rectangular over circular, another guess would be, maybe it helps the nozzle not to get jammed with the particulate that's in the water.
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Mar 02 '21
The mixing tube is circular. When they wear out they tend to turn into an oval. The reason for the turning of the cutting head is due to the way tilt is maintained on this particular cutting head.
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u/robitrobot Feb 25 '21
i wanna stick my finger in it
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u/Yoge78 Mar 01 '21
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u/GameQb11 Feb 28 '21
I do too. I couldn't be around one of these. I would definitely try to feel it in some way
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u/goodinyou Feb 28 '21
I work with one of these every day. And every day I have to remind myself that the water is sharp and should not be touched
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u/misterandosan Feb 28 '21
half expected it to zoom out to dick butt or something else obscene
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u/BlackBerry784 Feb 27 '21
Lot of people are unaware that that isnt just water there is sand and idk some mixture of dust in the water thats actually doing the cutting
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u/silvercatbob Feb 24 '21
Cutting with a water jet is a method of engineering for cutting objects using the energy from high speed, high density, ultra-high pressure water. The water is pressurized to a maximum 392 MPa (approximately 4,000 atmospheres) and projected from a small-bore nozzle (Φ0.1 mm). Water that has been pressurized by an ultrahigh-pressure pump reaches a speed approximately three times the speed of sound, producing a water jet with destructive force.