Waterjet Ready Drawing (slip joint)

T

tmerkl

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Jan 8, 2007
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Does anyone have any tips on getting a drawing ready for a waterjet run? I currently do all my patterns in a program called inkscape, which has the option to save as a .dfx file. How much extra "meat" do I need to add for the critical areas, if any? Should I scale the entire knife a couple thousandths oversize? Planning to just spot the the pin and pivot holes. Does anyone have any experience with doing this or things I should watch out for? As my orders stack up, it just seems like I could cut down on the time it takes by having 80% of the profiling and rise/fall done already. Thanks!
 
It depends a lot on what kind of finish you're specifying the WJ to cut with. The better the surface finish, the more the cost to cut. Also your design, and whether you're also cutting the spring, or just the blade. I would imagine .010" to be sufficient. On the few I've done with a laser .010" was plenty, and you'll likely be getting a finer surface finish from the WJ than I was.
 
I guess I always assumed that a laser and air hardening steels would not be a good match. Is this a bad assumption on my part? Yes, I'd like to cut the spring and blade. I'll have to investigate the cost for each assuming the laser is no problem. Thanks for your reply.
 
You may want to look at Fusion 360. It is free for hobbiest's. It will program the water jet supposedly from the drawing. I have used the program, but never had it program a water jet
 
tmerkl said:
I guess I always assumed that a laser and air hardening steels would not be a good match. Is this a bad assumption on my part? Yes, I'd like to cut the spring and blade. I'll have to investigate the cost for each assuming the laser is no problem. Thanks for your reply.
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Well, it can make life harder. I've laser cut Z wear, AEBL, S7 for air hardening. It definitely leaves you a hard skin that will skate a file. At the same time, it's very very shallow and I can for example, cut through it on the bandsaw. You just need to get over the skin with some pressure, it would skate all day with light pressure but you can pop right through it.

I wasn't suggesting you go to a laser house, just that it's similar consideration on how much stock to leave. You could get close to cutting exactly on size with a WJ, it just gets more expensive since each part takes longer to cut. That's the balance you'll have to strike on your own, how much more expense is worth how much less finish work after cutting.
 
I'd make the holes .005 to .010 undersized so that you can ream them to final. Depending on the size of the hole (and the WJ machine's tolerances) you may not even have to drill before you ream. Finishes are usually rated 1-5 (1 is very coarse and the fastest/cheapest, and 5 will leave an edge finish not completely unlike a media blasted finish, but is much slower and more expensive). 5 is probably overkill, as you'll want to grind/polish to finished dimensions anyway. I'd probably do about .010 as kuraki suggested as well. I'd run your final ideas/questions by waterjet's owner/operator as they will have a much better idea of their machine's capabilities.

You can certainly use laser as well, just as long as you compensate for the HAZ. You'd probably want to get some carbide reamers just for longevity sake.
 
Just to clarify from my other post since I didn't really spit it out. You're trying to compensate for 2 things from the WJ, like Andrew pointed out, the machines capability of positional tolerance, and how much material to remove for a satisfactory finish. If .010 seems like it's a lot, it's because that's about as good as most of these machines are capable of repeatably holding. On a fixed blade, that may not matter much, but depending on your slipjoint design it might make a huge difference.
 
Thanks everyone. The info you guys have provided gives me enough info to have some idea of what to ask the waterjet shop. Much appreciated
 
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