| Gallery, Projects and General > Project Logs |
| Spraymist |
| (1/5) > >> |
| bogstandard:
Still on my tuit list, this project definitely needs to be done sooner than later. I have been using flood coolant for many years, but since my new machines were installed, I have only ever used it on my mill, never on the lathe. This project, if it works, will get me away from flood coolant altogether, and I will make a spraymist unit for the four machines that require it, lathe, mill, surface grinder and power hacksaw. Having read both good and bad reports about spraymist, I have decided that good far outweighs the bad, and with a little redesign of a cheapo unit, I should be able to eliminate some of the bad faults. I think the main complaint is that the mist gets airbourne, and soon fills up the shop. I hope to get my systems using very small quantities of air and only tiny amounts of coolant. To such an extent, it will be a total loss system, just a quick wipe up in the area you are working in after you have finished. Please remember, this is experimentation on my part, and really the results won't be known for a fair while, as I play about with different size and design of nozzle. But what I will be doing first off, should get me a basic working system. Over the last few months, I have been gathering together all the bits to make the required number (and some). The main parts are the linkline type type coolant pipes. They can be as cheap or as expensive as you want to make them, but I have found that, the really cheap stuff is just that, and only really suitable for fitting into a fixed position, like on the power hacksaw. Earlier this year a friend brought me a unit back from the US, a nice cheapo job from LMS. http://littlemachineshop.com/products/product_view.php?ProductID=2725&category= Cheap and cheerful, and I suppose it must work, otherwise they wouldn't be selling it. The main problem that I can recognise instantly is the way the nozzle works, and it is this area that I will concentrate my main effort on. It works on the venturi principle, where air is speeded up as it goes past the pipe end, and when it hits the larger opening of atmosphere, the pressure drops (lower pressure than surrounding air, it could be described as a partial vacuum, if such a thing existed) and the coolant is sucked up the pipe and mixed with the jet of air. Hence it is spraying a mist of coolant. I will be attempting to reduce the amount of coolant flowing and trying to get a more efficient venturi effect. There is no coolant loose in the linkline at all, that is reserved for pressurised air, the small tube you see actually runs all the way back to the coolant tank. I scribbled up a bit of a design for a more efficient nozzle, and this will evolve as it is made. This is a rough sketch of the commercial unit air block, with a slight addition of my own of the stuffing gland, to assist in stopping air leakage, and also hold the inner pipe so that it cannot be pulled out easily. So now to get on my way. I will be using the pipe on the left, and as you can see, the orange nozzle has already been discarded, I will be making my own up to fit. Because there is actually no loose liquid inside the big tube, I am hoping that friction or Loctited joints will be satisfactory, plus I am expecting to use very low pressure and volumes of air, maybe around 20 to 30 psi, and micro litres in volume. The piece of brass was mounted up in the lathe and the end shaped up. I will just explain what the bits are for. The hole in the end goes all the way thru the nozzle, and is a very tight fit for the small pipe. The pipe will be forced up the end by say 1/2" and loctited in. The middle diameter is a friction fit into the end of the outer plastic tube. I now need to drill air tranfer ports to get the pressurised air from this side to the other. This shows how it fits into the end of the locline. Set in the RT, I carefully drilled down on the land between the medium spigot and the small one. I drilled 6 off by 1mm holes. I am not worried that they stay straight, as long as they reach the other end without breaking into the central hole or the outside of the central spigot. The six transfer holes drilled, no breakouts but they were a bit higgledy-piggledy on the other side. No concerns over that, the holes are thru and that is all that matters. The other end of the nozzle was cleaned up ready to accept a fine bore tube. The ones shown here are actually tungsten tubes off a spark eroding machine, the big one just behind the nozzle is about 2mm diameter with a 1mm hole up the centre. I will be starting off with a fairly small one, and experimenting with larger ones if I can't get the flow I require. Once things work out just fine, I can turn the whole nozzles up out of brass, and drill the correct hole in the middle. To be continued................. Bogs |
| bogstandard:
This bit might be a little more interesting, because it shows how to make a most underated tool, the lowly D-bit. Just to explain a little, a venturi nozzle can be very difficult to design and make, because there are so many variables, and I couldn't even start to be anything but a total novice in the design of one. But there are a couple of basic figures that I know will give me a design that works. These are shown in the C-o-C. I will be chopping off the front cone part, and it should work well enough to give me a usable spray nozzle. I want to make the back cone, and at this time I will make it adjustable, so I can find the optimum position for the inner nozzle itself. But how to cut an internal taper as small as I want it? A boring bar is out of the question as it would have to be so fine, it would be almost guaranteed to break. I could get a reamer made to the angle I want, but it would cost lots of pennies. The answer is a D-bit, and if well made, is just as accurate as a commercially made reamer. I am going to show you how I make one to continue with this job. Mounted up a piece of silver steel (drill rod), and faced off the end. Kicked the topslide (compound) over by half the angle required, in this case 11 degrees. Then using the topslide, the taper was being cut. The taper was finished when the small end was at about 2mm. I will be drilling a 3mm hole thru the nozzle material, so this D-bit will not require a cutting edge putting onto the very end. The machining marks were gently removed with fine emery. The bar was accurately measured up (this was 3/8" or 0.375"). Then it was divided by 2 and the figure rounded up. It was at this stage I changed my normal making practice. I would harden at this stage and grind the end down on my surface grinder. But because most people don't own such a machine, I am going to do it the normal way. Mounted up perfectly level in the milling vice, the bar is reduced down by not quite half it's diameter. One or two thou larger is ideal. Mine measured up when finished at 0.1885", one thou over half size. This is what it looked like close up. The machining marks are only tenths of a thou deep, so no worries over those. I would forget about deburring, as you can easily take too much off the edges and prevent it being sharpened. It was now time to get things warmed up and hardened. Just the part that was machined was heated up to cherry red, and held there for a minute or two, then it was quickly quenched in water. This should make the tool as hard as glass. I don't bother tempering the tool, and that is just a personal thing. The machined face is then gently smoothed down on a smooth oiled stone until the machine marks are gone. You should end up with edges as sharp as a razor. You tend to hoard the good and more useful ones that you make. Just in case. So that is the D-bit made. Next time I will be using it to make the adjustable brass nozzle. Bogs |
| Andy:
Much appreciated, as always. I'm following this with great interest, learning all the time. Making D bits is a nice 'bonus feature'. |
| Darren:
Nicely shown John, I've been itching to make a D-bit but for a totally different reason/job. :thumbup: |
| chuck foster:
i have used d bits for those once in a life time odd ball size holes that just don't warrent buying a reamer for, with a bit of care they work just fine. thanks john chuck :wave: |
| Navigation |
| Message Index |
| Next page |