2010/9/10 Jon Elson <[email protected]>: > Ian W. Wright wrote: >> Viesturs wrote.... >> >> >>> So >>> I do not see any way to create a DIY pump for waterjet cutting. One >>> can easily build the machine construction, but I am convinced that >>> pump, high-pressure tubing and cutting head are impossible to be >>> created in a DIY process. >>> >> >> So how was the original principle established - not by some guy in his >> garage workshop as usual?? >> It will be fun to watch and see how long it takes someone on the list to >> make one - I can't believe no one will try!!! >> > I have absolutely no doubt that an experienced machinist, especially one > who is well familiar with > ultra-high pressure hydraulics or waterjet machines, could fabricate a > high pressure pump himself. > I also believe that someone less familiar could spend quite a lot of > time tinkering with it to get it > to work properly.
Yes, just as I stated in my latest e-mail - do not do this at home unless You have know-how or prior experience. Otherwise one poses himself to a serious risk of a lethal injury. The thing I would like to stress is that getting it to work properly - shift the stroke from one direction to another etc - is not the hardest part. The hardest part in the history of this technology is being able to get the pumps reliable. Pressure is enormous and so is the stresses applied to the construction of the pump. One has to have access to a very well kept know-how, what materials have to be used. Pumps with 90000 PSI pressure have appeared only recently in the market although they have been prototyped long ago (I recall reading that prototypes of 120K PSI have been built), but the problem is to find materials that can bear that kind of stress (it was said that simply thickening walls of the high pressure cylinders does not solve the problem), finding, what kind of seals have to be used to make them last longer than few hours. That is where very many issues have to be solved. > > Actually, I think the abrasive injection nozzle is > likely to be harder to get right > than the pump. There are all sorts of things that have to be just right > to entrain a steady flow of > "dust" into the water jet, and I can see 100 ways that a single drop of > stray water can make the > garnet jam up. > Just like a DIY machine hobbyist is purchasing stepper motors instead of fabricating them, I believe that buying ready-made parts for the cutting head is the way to go (just like it is with the pump, but, unfortunately, AFAIK only KMT is selling separate high pressure pumps, Flow, Omax and Ptv will not sell You a separate pump, one has to buy all the machine). Actually, it is not difficult to get a steady flow of the abrasive, because, if it is dry, it flows very easily and getting a steady flow of abrasive is similar to getting a steady flow of water - just make a proper hole for it to flow out of the container (usually in a shape of cone, turned upside down) and create a valve that opens/shuts it down as necessary. The water jet creates a sucking force which then sucks the abrasive through the small pipe and water can get to abrasive only if the nozzle gets clugged or any other non-usual situation. Under normal operation water cannot get into abrasive tube. Trust me, the abrasive feeding system is very very very simple, compared to remaining pieces in the puzzle of this technology. I have read that the inner form of mixing chamber (the place, where abrasive meets water jet) influences the efficiency of usage of the abrasive as a cutting particles, but I have not found any source with detailed explanations. Yet another one tightly guarded piece of know-how. IMHO the hardest part with the cutting head would be on/off valve for the water. Conventional solutions do not apply here due to enormous water pressure. Viesturs P.s. I feel happy as a small kid, having the chance to explain this technology, as I have turned into it's fanboy :)) ------------------------------------------------------------------------------ Start uncovering the many advantages of virtual appliances and start using them to simplify application deployment and accelerate your shift to cloud computing http://p.sf.net/sfu/novell-sfdev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
