CNC Plasma Build

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Hello GroupI have started on a CNC plasma build. basically 1200mm to the X axis and 800mm to the Y axis. I have built a few CNC router type machines but this is the first plasma.I haven't tried this yet but I believe the new pilot arc plasma machines do not need to make contact witt he material to be cut, this means no need for a powered Z axis or ATC.I have used toothed belts on my machines and find them reasonably cheap and if a modern profile used accurate, I did have problems with " AT  " profile belts, but " HTD's  " seem fine, and with a plasma machine I'm not after the fine cut needed with a router.I have attached some photos which should be self-explanatory, the cut parts are 5mm steel and have been laser cut, the frame is 150mm by 50mm by 4mm wall thickness RHS, 25mm round linear rails are used on the X with 20mm round on the Y, I have a cnc router and am thinking of making a powered Z for this one and selling the router one, it's a little bit smaller and this is only a hobby - I am making the plasma machine as I want to do some 3d metal work for a 3m wide gate, would have been easier with a small angle grinder but this is more fun!.I hope to have the machine finised by Christmas - this year!!!The RHS was new about 12 months ago, whilst under cover, it got wet, the corriosion was unexpected and heavy, I hope to send it to the powder coaters early next week, we'll see how it comes out then.For those who noticed the holes / weld nuts in the end, they are so the frame can be mounted in a frame that allows the whole lot to be rotated along it's length, I used to move them by hand but as you get older - you know!!.Part of the gantry is bolted to the linear bearings white the 75mm by 10mm  flat is welded to the base ( frame ) there is enought adjustment in the  holes of the aluminum extrusion to allow fine adjustment to get everything parallel later.I'm using a 415volt three phase mig to weld it all together, I'm not a welder but like to fiddle a bit.Ed Attached Images
Reply:great project!Buy American, or don't whine when you end up on the bread line.
Reply:the cnc plasmas ive seen, there is a 3rd axis (z axis) that keeps the torch at a certain distance away from the steel...  most plates are not perfectly flat so the torch head needs to follow the height of the warped plate..tackleexperts.comwww.necessityjigs.comhttps://www.facebook.com/groups/mach...dingequipment/
Reply:ProgressWelded the gantry today and finished the frame ( base ) - didn't think about the process of welding the bottom of the water bath in, the cut strips along the sides should have had a gap between them and the base, I chased a leak all afternoon - as can be seen from the water on the ground. think I have it now. You would think after almost 60 years on this earth, I would stop and think a bit!!!The rolling base makes welding the frame easy bit of effort but worth it.I use a similar approach with the cnc routers I make and realised ( again ) that to get full use of the bed I would need to have the gantry slightly different from the routers, those thin angle grinder disks make " adjustments " easy.Brucer, the powered Z axis I have seen, only allow the height to be set under control of the computer, I haven't seen any that sense the material and adjust accordingly, still I am a building contractor, not a metalworker so who knows whats' out there!Ed Attached Images
Reply:Looks like a great build on that table... The "look and sense" part comes from the G-code and machine/software capabilities ... and I suppose there are dedicated THC modules that can do it independently also...For the height sense "Touch off" one way to do it is... (this requires a Z-axis with a sense switch)... the G-code says... "Probe in the down direction" this lowers the axis until the switch is triggered"Set the axis to "Z0"   Z0 is the surface of the plate in plasma cutting"Raise the axis to pierce height""Torch on""pause for pierce""lower axis to cut height""Start move for cut"For CNC control software... look at EMC2 "Free" - Linux                                          or       Mach3 "$175 US" - Windows ... I created a small circuit to invert the voltage output from a Powermax 45 and send torch up/down signals to Mach3/EMC2 for THC capabilities, but my Z-axis doesn't have a switch yet so I just put in a PAUSE command to the G-code and manually set the initial Z0 then automatically pierce/cut. Eventually I want to program a PIC for a digital THC... I plan (read "hope") to run the X and Y axis signals through the PIC to analyze the speed of cut, and possibly vector changes to compensate for arc length in corners.I use Google Sketchup to draw "FREE" and use a Rubyscript plug-in "FREE" to export DXF line files...Then I process For G-code generation with Cam777 "FREE" from plasma777.com took a few tries to figure out the setup but it works great for free software. their plasmatrace works for BMPs as well but you have to process the  Image in an editor first...Sheetcam looks awesome for a low cost Gcode processor also.I didn't mean to derail your thread at all, but thought the info might help you or others.Never argue with an idiot. They drag you down to their level, then beat you with years of experience.
Reply:Nice build. Those laser cut parts sure look nice. I really like your rotisserie positioner. Can't wait to see what it looks like when done. I have a THC on my cnc plasma. Worth every penny. Nothing is flat and the THC maintains the torch distance and really extends your consumable life. I would definitely think about adding a z-axis with THC if possible.Awesome design. What program did you use to design your parts?
Reply:Very cool!!!  a CNC plasma is on my "When I move to a house with a workshop" to-do listlooks good so far
Reply:I have a 2x2 torchmate cnc plasma setup.There is no z axis on my machine, just x and y.With this system a water table is a must to prevent metal warpage.I will use weights to hold down the corners of any unflat steel.The z axis THC will about double the cost of my machine.JasonLincoln Idealarc 250 stick/tigThermal Dynamics Cutmaster 52Miller Bobcat 250Torchmate CNC tableThermal Arc Hefty 2Ironworkers Local 720
Reply:does the water help cut down the smoke and stuff from plasma cutting?
Reply:Hi from Texas, just wanted to say your table looks good  and i'm with forhire on the torch hight control thc, I built a CNC plasma cutting machine last year,  posted some pictures for you of the castings I made for the Z axis and floating head that works with the thc, it makes life much easier. If you want to see more pictures of my build go to my profile, I have posted them there, have a good one, Jeff.  Attached ImagesLast edited by Jeff-; 11-28-2010 at 12:50 AM.
Reply:The build is looking good.....just wanted to add a few comments based on your comments as well as others on this thread!- "Pilot Arc" plasma systems have been around since 1959! They are not new. There are some import plasma manufacturers that have a new pilot arc based torch....and it is new to them. Hypertherm plasma torches have always been pilot arc start. The confusion often is that there are high frequency start torches with a pilot arc, and there are non high frequency start torches that have a pilot arc. There also are torches that must get close to, or actually contact the plate...to get the arc started (these torches do not have pilot arc, but do have high frequency). Any pilot arc torch will fire a plasma arc in the air. A non pilot arc torch will not fire in the air.- Torch height control is critical for cnc plasma cutting.....unless you plan to cut one part at a time....and stand by the machine monitoring torch height by hand. There are 3 height phases that are important....1, Pierce height, 2 cut height, 3. Cut height with arc voltage feedback. A good THC must be able to do all three with accuracy to within .010" of the torch manufacturers specifications.- Water tables are a good, simple, inexpensive way to control fumes, but there is a cut quality effect when water is in contact with the cut edge in terms of edge roughness and dross formation. The best cut quality is done with a downdraft cutting table to remove fumes. Downdraft tables require relatively high air flow (depending on the size of the table and the power level of the plasma system), and are usually more costly and complex as compared to a water table design.Jim Colt Originally Posted by weldappiHello GroupI have started on a CNC plasma build. basically 1200mm to the X axis and 800mm to the Y axis. I have built a few CNC router type machines but this is the first plasma.I haven't tried this yet but I believe the new pilot arc plasma machines do not need to make contact witt he material to be cut, this means no need for a powered Z axis or ATC.I have used toothed belts on my machines and find them reasonably cheap and if a modern profile used accurate, I did have problems with " AT  " profile belts, but " HTD's  " seem fine, and with a plasma machine I'm not after the fine cut needed with a router.I have attached some photos which should be self-explanatory, the cut parts are 5mm steel and have been laser cut, the frame is 150mm by 50mm by 4mm wall thickness RHS, 25mm round linear rails are used on the X with 20mm round on the Y, I have a cnc router and am thinking of making a powered Z for this one and selling the router one, it's a little bit smaller and this is only a hobby - I am making the plasma machine as I want to do some 3d metal work for a 3m wide gate, would have been easier with a small angle grinder but this is more fun!.I hope to have the machine finised by Christmas - this year!!!The RHS was new about 12 months ago, whilst under cover, it got wet, the corriosion was unexpected and heavy, I hope to send it to the powder coaters early next week, we'll see how it comes out then.For those who noticed the holes / weld nuts in the end, they are so the frame can be mounted in a frame that allows the whole lot to be rotated along it's length, I used to move them by hand but as you get older - you know!!.Part of the gantry is bolted to the linear bearings white the 75mm by 10mm  flat is welded to the base ( frame ) there is enought adjustment in the  holes of the aluminum extrusion to allow fine adjustment to get everything parallel later.I'm using a 415volt three phase mig to weld it all together, I'm not a welder but like to fiddle a bit.Ed
Reply:can't wait to see more... the cnc stuff is really daunting to me. I just want a plasma table. I'd like to get my feet wet with some kind of dremel based router table or even just a pen for drawing vector graphics on a piece of paper... that way i can take the skills I learned from that and apply it to a larger plasma cutter