Indicating exiting features on a waterjet
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  1. #1
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    Default Indicating exiting features on a waterjet

    Easiest example, if you have a flat wide ring (disk) where the ID is finished, and you want to waterjet features concentric to the ID, how do you pick up the finished bore ? A fixture isn't practical, bores are different sizes, 3 jaw chuck would gum up in a hurry. Different example, you want to produce holes at a certain dimension from a finished edge? Is there some kind of electronic edge finder available for waterjet? I'm sure an applications engineer from the waterjet manufacturer could answer these questions,but don't want to go there yet.

    Title should say existing, cant edit the title.

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    Water jets don't lend themselves as well to setup on existing features but it can be done. There are LASER edge finders or you could cut a matching hole in a piece of material clamped in and use a plug to align. It all depends on how accurate you need to be and how much time you want to spend setting up to cut. Another machine may be faster.

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    You would have to make a part that has bearings and swivels on the mixing tube. Could sweep the part with a indicator then.
    Thinking of something like you would use on a edm sinker.

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    I've had to do this a few times and mostly it comes down to how accurate you need to be as has been said before. My quick and dirty method is to bring the nozzle down inside the approximate center of the hole( hopefully it's a large hole) and use the edge of the nozzle as an edge finder and a cigarette paper to use as a feeler. Go to on side and touch off,zero then go to other side and halve the reading for the center of X then do the same for Y. I think if you want more accuracy then you could make a holder for a Haimer 3D gauge and do the same thing. I'm thinking anything done on a water jet like this probably doesn't need to be highly accurate as you still need to clamp it down without moving it. I'm really interested to hear others ideas

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    Draw your holes in CAD, and draw an arc that matches the ring. Maybe quarter circle. Same relationship to holes as the ring, account for kerf. Clamp something to bed and select just the arc to cut. Cut arc and place ring into "fixture". Select only holes and cut.

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    On the last waterjet I ran we used things like mentioned above. Cut the nest then drop in the part or use the mixing tube and a feeler to find an edge.

    I currently have an omax with the "optical edge finder" option which is excellent at this. Just pop on the camera and find an edge with cross hairs or use the hole center function. Then pop the camera off and go. Seems good to a few thou if the edge of the part is crisp on camera.

    The basis of the optical edgefinder is just a bit of software that allows you to calibrate the distance from the camera's cross hair to your actual center of cut. You could easily make a quick detach mount for a taster or one of those optical scopes for a mill and record your own offset distances to apply to your "home" or part origin.

    The camera btw seems to just be a cheap usb microscope that happens to have cross hairs. Though I assume the word "Omax" on the side brings the cost up considerably..

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    Tram a part edge to the waterjet axis then using the nozzle and a feeler gage or making a square 90 degree edge or full part nest like others have said.
    One other trick I have used is to put a brand new nozzle in and run water only at the lowest pressure it will squirt out and jog in small increments until the column of water is interrupted. Then just offset for the radius of the water column to find nozzle center.

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    Some good suggestions here. I like the no-abrasive trick. We have a little cone device that slides onto the nozzle and clamps with a thumb screw and has a diameter of about 1/2". You can drop this into existing holes and line up probably within .005" or better just by eye. If the ring described above was small, I'd maybe turn a plug with a 1/4" hole in the centre to fit into the finished bore, and then pick up the center. If it was big I'd use jmullett's technique to find the inner edges and thence the center, unless i had an optical locator. It's true that waterjets aren't supposed to do this but in fact you have to do it from time to time and there's always a way that works out. Omax at least are super easy to program, so moving the start point of a cut to whatever reference point of the part you've got is always straightforward and makes you feel clever every time.

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    I have a laser-pointer that goes on my omax globalmax (mentioned above) - it appears to be the EXACT same unit sold for use in milling machines with a little different body.

    But in my use so far, it's "all the waterjet cutting is first"....


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