robertspark Posted January 18, 2015 Share Posted January 18, 2015 As per title .... Accessory for the cnc plasma table... A tube notcher This one here still wins with me really as the a axis will always be in fixed units and not rotational degrees transposed into tube diameter. The former is the way a lot of tube notch apps / utilities that output a cad drawing profile seem to work. https://m.youtube.co...h?v=7fK4qaf4maI https://m.youtube.co...h?v=D-BuRLhfLvk Although this does require notching the tubes before bending .... Hence I was wondering if there was a way to make say a 300mm dia circular track that you could clamp to the tube then run a carriage on the track which conjunction with torch height control (thc) would adjust the torch height to the specific dia of steel tube you want cut ... That way it could be fixed in any orientation and you could bend the tube first then trim and notch it to your needs (shooting the breeze idea do you think there would be such a market for an accessory in the roll cage (4x4) market)? Quote Link to comment Share on other sites More sharing options...
simonr Posted January 18, 2015 Share Posted January 18, 2015 Thanks for starting the thread Robert! Questions: Should this be an add-on for a CNC plasma table or stand alone? Should the tube be rotated and the cutting head be stationary or the tube stationary and the cutting head move? Or a combination of both. I started thinking about how to move the tube in two axes. My first clever (I thought) idea was to mount the tube between rings of three Mecanum wheels (google for images) with two of them driven by stepper motors. If the wheels are turned in opposite directions the tube will move lengthways and if turned in the same direction, the tube will rotate. The problem is the wheels are uber expensive and I would have to write a set of Macros for Mach3 to drive each axis as it works differently to a normal XYZA setup. Cool, but too complicated! I like the idea of something that clamps to the tube and the cutting head moves. It would really need something like an Iris mechanism to do the clamping so the tube is always dead centre of the ring which the cutting head moves round. If I went down this route, what is the maximum tube diameter I should make it fit? I guess about 3" / 80mm? As you increase this, the cutter starts to become more and more unwieldy and heavy. Also, what is the minimum useful X travel required? It would need two clamps and the cutter would either need to move between the clamps or extend beyond the end of one of them. Either way, the travel is going to be limited. I guess at about 200mm? How should the rotary axis be driven? I've considered include laser cutting a tooth profile around the outside of a ring made in two bits so they can be un-bolted and clamped around the tube - so you could cut between two bends. Is this useful? I have found I've needed to notch a bit of tube post bending once or twice. This is a lot easier than trying to work out how the tube will twist in advance of several bends in different planes. Maybe that's just me being lazy? Your thoughts? Quote Link to comment Share on other sites More sharing options...
robertspark Posted January 18, 2015 Author Share Posted January 18, 2015 Can't post the photo from here (iphone) so forget the article but this was something I may have seen earlier to prompt the thought process (the problem with this is the x-axis plus a z-axis (weight....) ) but thought it was worth early consideration http://www.fabricatingandmetalworking.com/2014/08/beware-of-bad-bargains/ The rack could probably be made with a chain welded to a ring though or a load of chain drilled holes with pins inserted driven by a cog I was thinking to use one for a lobster type exhaust ( althought considering the starting point is a straight length of tube such a clamp cnc cutter probably is a) overkill and b) too heavy for thin wall exhaust tube (hence 4" od would probably be advantageous (to do snorkels too maybe if someone wants as that is probably the largest tube needed for a 4x4? Rob Quote Link to comment Share on other sites More sharing options...
wanger Posted January 18, 2015 Share Posted January 18, 2015 interested and interesting! yes cnc table with notcher is a great idea. i'm interested if this is a possability. Quote Link to comment Share on other sites More sharing options...
robertspark Posted January 18, 2015 Author Share Posted January 18, 2015 Wow those Mecanum wheels are interesting (someone did reinvent the wheel) I guess the treads would need to offer traction on steel tube (rubber?) and may wear over time. Wonder if they could be made? Cnc cut hub (star shape with tabs for each point) Points drilled / plasma cut (use as nut alignment holes with say a drill bit at time of nut weld) Each point /tab bent to 45 deg using a jig Nut welded on each side of the tab (once bent) Cylindrical tube chosen with an ID to match some cheap bearings and an od to match some rubber tube (think hose pipe sleeve (thin wall tube) ID of bearings to match 12.9 cap screws Bolts would lock against each other when tightened into the welded nuts .... That's the theory anyway (armchair designer) haha (Weight problem depending upon how many points required on each wheel plus bearings tubes and bolts etc) Direct drive on a stepper drive? (Segway?)... Err (edit) muppet think it would go round and round in circles trying to balance given the small wheels are not controlled / braked ... Work for an all direction platform though ( more stable) Quote Link to comment Share on other sites More sharing options...
simonr Posted January 18, 2015 Share Posted January 18, 2015 I designed a Mecanum wheel on the cad to be laser cut & folded and use Cast PU wheels. I 3D printed a version of it - which worked, but not well enough to call it a success. Each wheel needed 16 bearings and the machine would need at least 6 wheels - I decided it was just not viable cost wise! The Jim Colt article was good - but I see what you were talking about. It needs to be something like that which will adapt more easily to different tube sizes. Si Quote Link to comment Share on other sites More sharing options...
wanger Posted January 18, 2015 Share Posted January 18, 2015 depends what you want to notch i guess. roll age tube and under, down to say 1". so 2">1" over that its easy with a piece of paper and a grinder and under that use scissors Quote Link to comment Share on other sites More sharing options...
robertspark Posted January 18, 2015 Author Share Posted January 18, 2015 Overthinking the problem? (NASA design for a pen that works in space .... Use a pencil... http://www.scientificamerican.com/article/fact-or-fiction-nasa-spen/) Quote Link to comment Share on other sites More sharing options...
vinny Posted January 18, 2015 Share Posted January 18, 2015 I think a set of sized clamps for each size pipe you want to cut would be better. After all you need specific sized mandrel to bend the pipe. The clamp would be say 100-150mm long with teeth around both ends to stop the 2nd axis twisting, You can then relate the number of steps from the motor to degrees very accurately for any pipe size. The clamp could also give a fixed reference for travel along the tube axis. The clamp can be aligned around the tube to give an exact start point for the cut. I might be better with a sketch! Quote Link to comment Share on other sites More sharing options...
simonr Posted January 18, 2015 Share Posted January 18, 2015 Vinny - that's a good point! I drew this, this afternoon. Which will grip from 20 to 100mm. However - like NASA's pencil, I may have been over-thinking it and I think I prefer Vinny's suggestion! One clamp will probably cope fine with a small range of tube - say 1 3/4" to 2" Si Quote Link to comment Share on other sites More sharing options...
robertspark Posted January 18, 2015 Author Share Posted January 18, 2015 Wow that's impressive Si Quote Link to comment Share on other sites More sharing options...
zim Posted January 18, 2015 Share Posted January 18, 2015 Similar to how an electric pipe threading machine grips piping. G Quote Link to comment Share on other sites More sharing options...
simonr Posted January 18, 2015 Share Posted January 18, 2015 Similar to how an electric pipe threading machine grips piping. G How? Quote Link to comment Share on other sites More sharing options...
robertspark Posted January 18, 2015 Author Share Posted January 18, 2015 Zim, Like this one? http://www.northerntool.com/shop/tools/product_200317188_200317188 manual here (bit slow to load) http://www.northerntool.com/images/downloads/manuals/89138.pdf Not complete, but gives an idea with the photos... http://www.ebay.co.uk/itm/SP16510206-Electric-Pipe-Threading-Machine-Replacement-Spare-Parts-Front-Chuck-/281507355984?pt=UK_DIY_Materials_Plumbing_MJ&hash=item418b255d50 I guess the problem you get to when you want something to clamp to the tube then cut is size + weight, instead of just getting a chuck with a 4" bore and feeding your pipe through it. http://jnhanda.en.made-in-china.com/product/hexQrYmDIyRV/China-Hand-Cutting-Machine.html (starts at 4"....) Rob Quote Link to comment Share on other sites More sharing options...
simonr Posted January 18, 2015 Share Posted January 18, 2015 A little OT, but I thought I'd post a photo of a useful tool I made for tube-work years ago. It will hold any size tube from 10mm to 70mm at any angle. It's been tremendously useful for positionig bits to weld them together. Si Quote Link to comment Share on other sites More sharing options...
Bingy Posted January 18, 2015 Share Posted January 18, 2015 Zim, Like this one? http://www.northerntool.com/shop/tools/product_200317188_200317188 manual here (bit slow to load) http://www.northerntool.com/images/downloads/manuals/89138.pdf Not complete, but gives an idea with the photos... http://www.ebay.co.uk/itm/SP16510206-Electric-Pipe-Threading-Machine-Replacement-Spare-Parts-Front-Chuck-/281507355984?pt=UK_DIY_Materials_Plumbing_MJ&hash=item418b255d50 I guess the problem you get to when you want something to clamp to the tube then cut is size + weight, instead of just getting a chuck with a 4" bore and feeding your pipe through it. http://jnhanda.en.made-in-china.com/product/hexQrYmDIyRV/China-Hand-Cutting-Machine.html (starts at 4"....) Rob Link 1 yes Pipe threader Link 2 manual never looked at Link 3 Not of chuck but die holder Link 4 hard work On video in link 1 0.14 to 0.17 shows the scroll chuck. Quote Link to comment Share on other sites More sharing options...
simonr Posted January 18, 2015 Share Posted January 18, 2015 Link 4 is an interesting approach. You could use a toothed belt with a tensioner swing arm to pull a dolly on to the surface and drive the belt with a stepper motor. You could use one of the shortish belts made for lawn mowers. The X & Z axes just hang off the dolly. That has a feeling of low-cost ness about it! Si Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted January 18, 2015 Share Posted January 18, 2015 I wonder if the reason it's for 4" and above is because on a small pipe there isn't enough belt in contact with the pipe to prevent slipping? EDIT: Neat idea though Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted January 18, 2015 Share Posted January 18, 2015 Just thought, you could combine ideas and have your clamps with teeth on the outside for a toothed belt to run on and you'd have no chance of slippage. .... actually maybe I misunderstood and that was what you meant Si Quote Link to comment Share on other sites More sharing options...
simonr Posted January 18, 2015 Share Posted January 18, 2015 No - you got it first time! If you could change the wheelbase of the dolly and tension the belt sufficiently (more than one belt?) I can't see it slipping. You would probably not be able to go below 1 1/2" tube though. It would work equally well if you fixed the cutting head and let it rotate the tube - perhaps with another dolly to support the other end of the tube. Then you could use it in situ on a bent tube or on the bench if required. You could even control the stepper motors with a microcontroller and a simple interface where you specify the two tube sizes that you are joining and the angle. Let it plot a path and perform the cut. It's rare to need anything more complex and it would make it quite self contained and likely cheaper overall. Si 1 Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted January 18, 2015 Share Posted January 18, 2015 I like the idea it could do both fixed pipe or moving pipe and the fact you have eliminated one of the expensive parts of most machines which is the scroll chuck. Having it run from a microcontroller is an interesting idea Would be nice to keep the option of a computer controlling it as well just in case, but if it's a kit then I suppose you choose what to use when you build. Quote Link to comment Share on other sites More sharing options...
simonr Posted January 19, 2015 Share Posted January 19, 2015 It would be interesting to use the microcontroller as a full blown USB motion controller as well. That way, you can run it from a simple LCD + a few buttons, or plug in to your PC via USB. I don't know (technically) how a motion controller interfaces with Mach3 - but all the info is probably out there! While it's being USB a motion controller, you could use the buttons on the LCD to control Feed Rate and fine tune Torch Height? It could potentially do the torch height control too - which would be a significant value-add! Si Quote Link to comment Share on other sites More sharing options...
zim Posted January 19, 2015 Share Posted January 19, 2015 How? Skip to about 2 min - 3 min. G Quote Link to comment Share on other sites More sharing options...
simonr Posted January 20, 2015 Share Posted January 20, 2015 OK - what about this? The two belts would probably have to be further apart - but you get the idea. The torch is just cantilevered off the belt frame. You would use a screw adjust to tension the belt sufficiently to hold the rig rigid. One stepper motor (the big one drives the belts and the other smaller one turns a lead screw to wind the torch along the length of the tube. The two rollers that run on the tube are in slotted holes - my idea is that you adjust them such that the bottom of the rig is just proud of the surface of the tube. This adjustment means that the torch height stays the same cutting tube from 44 to 100mm tube diameter. Thoughts? Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted January 20, 2015 Share Posted January 20, 2015 Looks good, if the cantilever didn't prove to be rigid enough you could have a belt each end of the track and still use one stepper by sending the drive down one of the rails the torch head is running on. Although it would mean more parts which would put the price up, the cantilever idea seems to work well enough for some of the industrial cnc plasma cutter systems for cutting large plates of steel so is probably fine for this . Quote Link to comment Share on other sites More sharing options...
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