simonr Posted December 1, 2014 Share Posted December 1, 2014 I actually fired it up last night for the first time - and the PC crashed! The HF Start on the plasma was obviously inducing spikes somewhere inside. This evening I added a few clip-on ferrite chokes on the USB, power & Torch trigger wires plus a 0.1uF decoupling capacitor across the torch trigger wires - and it worked just fine! Another top-tip is to use screened cable between the PC & the plasma cutter. The screening (earthed to the breakout board 0v line) screens out most of the interference that might otherwise be induced in the wire. I have no idea what settings to use - torch height above the metal, current, speed at which the torch moves, air pressure etc. I see a fair bit of trial & error before I get it right. Si Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted December 1, 2014 Share Posted December 1, 2014 Excellent work Simon, how's the cut quality? Quote Link to comment Share on other sites More sharing options...
simonr Posted December 1, 2014 Share Posted December 1, 2014 Excellent work Simon, how's the cut quality? Terrible! One cut was pretty good - but I didn't pay attention to the settings! I was too excited! I'll see what I can find on line so far as suggested settings are concerned - I could do with a place to start from. I'll try again on Wednesday with a new nozzle & shroud on the cutter. the current one is a bit on the manky side. Si Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted December 1, 2014 Share Posted December 1, 2014 I think Rob posted earlier in this thread some guidlines for settings .... I'll take a look Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted December 1, 2014 Share Posted December 1, 2014 Here's the post I was thinking of http://forums.lr4x4.com/index.php?showtopic=89125&p=789931 unfortunately I think we may need Rob to scan a page or two from his manual Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted December 1, 2014 Share Posted December 1, 2014 Simon, have a look at https://www.hypertherm.com/Xnet/library/download/?file=HYP115403 (powermax 65/85 manual) It has some charts starting on page 3-23 that might help Quote Link to comment Share on other sites More sharing options...
simonr Posted December 1, 2014 Share Posted December 1, 2014 Thanks Barry! You (from an earlier post) have an R-Tech 50A Plasma? How would you rate it? My Plasma is only 30A and will cut 6mm cleanly and just about manage 10mm not at all cleanly. Now this is working, I thought I might treat myself to a more powerful plasma (and stick mine on eBay!). These days there are so many out there, it's hard to choose! How well does the Pilot Arc work? Mine is HF Start, but on rusty plate, occasionally it looses the arc and you have to re-trace. It's not a problem, just inconvenient. Si Quote Link to comment Share on other sites More sharing options...
discomikey Posted December 1, 2014 Share Posted December 1, 2014 how much would you stick yours on the blag site for? hehe really keen to see cut quality when all sorted, i presume it will be pretty good because a decent cut on a plasma is all down to the settings Quote Link to comment Share on other sites More sharing options...
simonr Posted December 1, 2014 Share Posted December 1, 2014 how much would you stick yours on the blag site for? hehe Not really thought about it. It cost me about £500 inc VAT about 5 years ago but has seen a lot of use. I guess a couple of hundred? I'll persevere with it until I get decent cut quality and order another one after Xmas some time. Si Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted December 1, 2014 Share Posted December 1, 2014 The R-Tech 50A plasma is the only one I've used so it's hard to have anything to compare it to. The pilot arc works well (obviously only used it by hand as my cnc table is still a pile of parts). Whilst cutting some stainless steel I thought something seemed strange with the cut, turned out I'd forgotten the earth clamp but it had still cut the (thin) stainless with just the pilot arc. Also works well on painted/powdercoated steel. If you want to try it out on your CNC table you're welcome to borrow it. Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted December 1, 2014 Share Posted December 1, 2014 BTW there are some 30A tables around page 3-9 in this manual https://www.hypertherm.com/Xnet/library/library.jsp?file=HYP109170 Quote Link to comment Share on other sites More sharing options...
robertspark Posted December 1, 2014 Author Share Posted December 1, 2014 I'm happy with my Hypertherm Powermax 350 (manual here basically 30A output so similar to Simons I guess in cut speeds) https://www.hypertherm.com/Xnet/library/library.jsp?file=HYP104427..... but I'd happily have something bigger (single phase) as the pilot arc is brilliant and I've had some really good cuts too reciently although I don't think I'll be cutting 3/8" plate any time soon (armour plating not required on my build!) If you want other manuals there can be downloaded here including the service ones, that's the thing about hypertherm everything is available, clear and above board.... afterall all they do is plasma (but you pay for it, and they have good R&D from what I've seen) http://www.hypertherm.com/en/Service/Manuals/ photos of my build are here, just updating the library: http://s947.photobucket.com/user/rclandrover/library/Plasma Quote Link to comment Share on other sites More sharing options...
steve b Posted December 2, 2014 Share Posted December 2, 2014 Have you thought about using oxygen instead of air ? this will improve the cut quality considerably , it's what we use on the Esprit HD at work . cheers Steveb Quote Link to comment Share on other sites More sharing options...
simonr Posted December 2, 2014 Share Posted December 2, 2014 Thanks chaps. I'd not considered using oxygen. I have a BOC contract - so I guess I could give it a go! Think I'll get it working the best I can on air first though. Si Quote Link to comment Share on other sites More sharing options...
steve b Posted December 2, 2014 Share Posted December 2, 2014 We use nitrogen and helium iirc for stainless and aluminium , I'll have a look at the mix ratio's when I'm in later cheers Steveb Quote Link to comment Share on other sites More sharing options...
robertspark Posted December 2, 2014 Author Share Posted December 2, 2014 The commercial machines use oxygen but you need to consider the flow rate ..., my plasma requires 127l/min of air so a 20l bottle of oxygen at 200 bar is 4000 l of air which is say 30 mins of cut time (on pure tanked gas, not sure if you can run a mix to just increase the 21% in the air) Then you need to consider the cut speed (tables for mine in the manual) .... Thought I may consider it if I was doing something special ..., not sure if O2 improves the machines cut depth too I think you need to focus on the pierce delay and the dropping down to the cut depth (half the pierce height) Quote Link to comment Share on other sites More sharing options...
ejparrott Posted December 4, 2014 Share Posted December 4, 2014 I've been toying with the idea of getting a plasma cutter. Also been thinking about a mount to hold a torch on the end of my mill table to give the X & Y movements. How much does the Z get used when cutting though? Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted December 4, 2014 Share Posted December 4, 2014 I've been toying with the idea of getting a plasma cutter. Also been thinking about a mount to hold a torch on the end of my mill table to give the X & Y movements. How much does the Z get used when cutting though? Same as Laser and Water Jet, a controlled plunge and then stay at depth till you finish cutting. Quote Link to comment Share on other sites More sharing options...
robertspark Posted December 5, 2014 Author Share Posted December 5, 2014 I've been toying with the idea of getting a plasma cutter. Also been thinking about a mount to hold a torch on the end of my mill table to give the X & Y movements. How much does the Z get used when cutting though? I don't think that a mill table will give you the feed rate required, but you be the one to decide, have a look at the hypertherm manuals posted above / links below as they give tables in the operator manuals for feed rate and material thickness besides being able to cut thicker material (which is sometimes useful), the higher amapage will give you a higher feed rate which I would have thought would have been useful in a commercial environment, as well as the increased duty cycle. mine is suppose to do the following (mild steel): 1.3mm - 70 in/min 2.8mm - 52 in/min 6.0mm - 17 in/min 9.0mm - 9 in/min all at 25A, and about a 40% duty cycle (so multiply by 4 for the 10min cut duration). The Powermax 45 (next size up, and largest from hypertherm single phase [hence my next upgrade with a mechanised torch]) will do: 1.5mm - 350 in/min 2.7mm - 190 in/min 6.4mm - 25 in/min 9.5mm - 20 in/min all at 45A, and about a 50% duty cycle (so multiply by 5 for the 10min cut duration). (not plugging their equipment, just seem to have the most amount of concise information available in once source, and you could probably relate it to others with similar current and duty cycle machines). The torch cutting heights, pierce height and pierce delay are interesting in the Powermax 45 manual for a starting point on mechanised cutting. Rob Quote Link to comment Share on other sites More sharing options...
ejparrott Posted December 5, 2014 Share Posted December 5, 2014 Don't know what speeds it'll come up with yet, not up and running Quote Link to comment Share on other sites More sharing options...
robertspark Posted December 5, 2014 Author Share Posted December 5, 2014 Ahh sorry thought it was an existing mill that you were going to mount a torch in the tool holder and cut on the xy bed (well above it) I thought mills tended to be slow at movement but accurate because of the fine pitch leadscrews which also provide the bed rigidity Looking at the 45 manual I was surprised to see a cut height of 0.5mm on one of the pages. Doesn't give much room for error without THC Quote Link to comment Share on other sites More sharing options...
simonr Posted December 6, 2014 Share Posted December 6, 2014 I've found that I don't need to move that fast! about 100"/min is as fast as the plasma seems to cope with! More than that and the arc is prone to extinguishing! I think if the Plasma had a pilot arc (to re-ignite) it might be able to go faster - or if I was using very clean, shiny plate. Also, 0.4mm cut and 1.2mm pierce seems to give the best results for me. I think I'm going to add the THC as 0.4mm exceeds the flatness of the plate I've been using and it keeps touching down and ruining the cut (and tip!). Si Quote Link to comment Share on other sites More sharing options...
simonr Posted December 6, 2014 Share Posted December 6, 2014 Well, I've taken the plunge & ordered a Hypertherm Plasma Cutter! 60A Single or 3 Phase, Pilot Arc and a Machine torch! I did some nice cutting this evening! My dad has a 'studio' in their garden and he asked if I could make a sign. He designed it! I was going to 3D Print it - but thought I could have a go at plasma cutting it instead. Not the best photo of the finished article, but the detail & finish is not bad. This is it with a coat of primer. I must resist the temptation to make a horrible pictorial weather vane - which seems to be what everyone else who's built one does! Si Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted December 6, 2014 Share Posted December 6, 2014 Excellent! That's a succesful build The cut looks clean, did you do much cleaning up of it? Or is that pretty much as it came off the table? Quote Link to comment Share on other sites More sharing options...
simonr Posted December 6, 2014 Share Posted December 6, 2014 There was a bit of scale on the back. Most of it came off with a chisel then a quick zip over with a sanding disc. Today it became a really useful tool! I'm really impressed with it! Si Quote Link to comment Share on other sites More sharing options...
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