simonr Posted January 20, 2015 Share Posted January 20, 2015 The problem with supporting the torch on either side is when you are severing the tube - notching for example. The end of the arm is less & less supported as the cut progresses. Si Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted January 20, 2015 Share Posted January 20, 2015 Doh! Very good point Si Quote Link to comment Share on other sites More sharing options...
robertspark Posted January 20, 2015 Author Share Posted January 20, 2015 Wow Si, you can draw quick, that idea looks good, I was trying to draw something last night using the pipe threaded type chuck (actually it's very similar to the 3-jaw lathe chuck arrangement), but using two plates with angled slots cut in them, working in opposite directions (sprung loaded) so that the tube would always be centred, then you could use maybe a mecanum wheel on one of the jaws. Now if you bult two of these assemblies, the other with an opposite mecanum wheel, each driven by a stepper, you could probably drive them through a simple logics arrangement from the standard mach3 BOB. Whats the options for say 38mm tube? (thinking exhaust headers here [lobster type]) I thought CDS tube came in 1 1/2" (38mm) and 1 3/4" (44) mm. Should we not be looking at a little lower than 44mm to increase interest? Quote Link to comment Share on other sites More sharing options...
simonr Posted January 20, 2015 Share Posted January 20, 2015 I look forward to seeing your drawing! It's adaptable to smaller tube - but only to a point! The problem with this approach is the resolution is proportional to the circumference. When the tube gets too small, the resolution follows. Do you use Solidworks? I think it's the software that's quick more than me! Si Quote Link to comment Share on other sites More sharing options...
robertspark Posted January 20, 2015 Author Share Posted January 20, 2015 Inventor Quote Link to comment Share on other sites More sharing options...
simonr Posted January 22, 2015 Share Posted January 22, 2015 Not that different to SW. A bit like Jeep versus Land Rover - each of their followers think theirs is best! Si Quote Link to comment Share on other sites More sharing options...
zim Posted January 22, 2015 Share Posted January 22, 2015 Which one represents LR ? Quote Link to comment Share on other sites More sharing options...
robertspark Posted January 22, 2015 Author Share Posted January 22, 2015 I've used autocad in my day job for 16 years, from LT, to full to Revit. The naming convention is just similar. I've looked at solidworks but at the time (4 years ago ish) it didn't seem to flow for me (command names). I've developed my knowledge as we all do in that time frame and from what little used inventor I've picked it up quickly although would not consider myself an expert at it by any stretch of the imagination. AutoCAD that is another matter as it pays my bills and I need to know how to use it + keyboard commands etc for speed. Revit I've done a few jobs with it, and although I know how to use it, it has not clicked with me yet. My give solid works another look at. Side note, back on topic -> the laptop kindly crashed for me 2 nights ago, so although I was getting somewhwere with the two plates and slots idea for a chuck type arrangement (sprung loaded), looking at the dimensions of the plates required ( largest tube dia (100mm) + edge clearance to slot (say 20mm) + the 1/2 tube diameter for the jaw movement (50mm) + 1st slot to 2nd slot clearance (say 25mm) + 2nd slot to outer diameter clearance (say 20mm), ) so total size is about 310 diameter. then factor in the weight (although you could add a wedded design to reduce some of the weight), it all starts to get a bit cumbersome Hence I think Si's idea defiantly looks to be a more flexible idea (you could probably change the belts and use it on larger tube too). I've still not got my table going so am taking a back seat to get it sorted (work + life balance) + need to make progress on my LT230 which has effectively stopped since starting the table. (should have waited and gone with your group buy Si.... table alignment issue being resolved with non-aligned welds [schoolboy / backyard mechanic error] However I'll defiantly be down for a group buy on this idea at the end / if you offer a kit etc. Thought for the Z axis -> suggestion to maybe not use a stepper (given the tube is likely not to have much variation to alter the torch height) but what about using something like a solenoid..... that way if you have a plasma torch that requires scratch / touch start, you set the solenoid at the touch setting, and once the arc is ignited, can raise the torch by a few mm? Alternatively, if you have a HF torch, and want to save your expensive consumables, you can set the high setting as your pierce height, then drop down to the cut height when the solenoid is energised? (am I over thinking the torch height problem? ) Rob Quote Link to comment Share on other sites More sharing options...
simonr Posted January 22, 2015 Share Posted January 22, 2015 should have waited and gone with your group buy Si.... table alignment issue being resolved with non-aligned welds [schoolboy / backyard mechanic error] Rob However, if you'd done that - I wouldn't have had the impetus to build mine! A solenoid for the Z Height is a good idea - just moving between two adjustable stops. Si Quote Link to comment Share on other sites More sharing options...
robertspark Posted January 22, 2015 Author Share Posted January 22, 2015 A solenoid for the Z Height is a good idea - just moving between two adjustable stops. The catch comes in solenoid choice, seems to be a load on ebay, or wind you're own... (lathe, roll of coated wire, tube and a pin...) The energisation period should be only a few seconds until the arc is struck or pierce is achieved. (side note... I was trying to use these as they can be had for about £75 for 4 in the UK http://proto-pic.co.uk/mecanum-wheels-4-pack-1/ (only need 2 per cutter) and were not large diameter, and may have been able to bolt directly to a Nema stepper .... but the files in the newer version of inventor than the one I'm using http://grabcad.com/library/mecanum-wheel-3 thought it would be a clever idea to plonk a tube cutter on one end of a tube and it walks its way down to the other end cutting off sections .... (tube would need to be supported somehow though but the imagination was working... Quote Link to comment Share on other sites More sharing options...
simonr Posted January 24, 2015 Share Posted January 24, 2015 That's pretty much what I was considering here http://forums.lr4x4.com/index.php?showtopic=92681#entry802410 I 3D Printed one which worked better (with some tiny bearings in each roller). They only work if the axle is exactly parallel to the floor - as the wheel is only 'round' in one plane. As you move off that plane, it gets more & more 'lumpy'. My wheel was 50mm OD and ran OK on 100mm tube. Less well on 50mm. I think the issue is the required tolerance of the wheel axle being parallel to the tube axis. The smaller the tube. the more precise this has to be. Even with bearings, about 70mm was the limit. High precision / low tolerance costs money - likely more money than doing it a different way! I think the Belt idea has the best chance of anything I've seen / thought of so far! Quote Link to comment Share on other sites More sharing options...
robertspark Posted January 24, 2015 Author Share Posted January 24, 2015 The belt idea above is by far the best, but I was wondering.... Is the larger diameter not limited by belt length? If so could you not just swap over to a longer belt and then use it on larger tube? For the smaller diameter, could you not have slotted holes for the rollers which would allow adjustment for the smaller tube diameters (in conjuntion with a shorter belt)? I'm thinking here of something like a Gates HTD5 (5mm pitch) http://www.sdp-si.com/D265/PDF/D265T016.pdf For not a lot of money you can then choose a few belts to do nearly any tube diameter of your choice? Edit: I wonder if it's possible to run the belt inside out, so that the smooth side is on the tube (greater contact area, potential of less slip?) Quote Link to comment Share on other sites More sharing options...
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