Hole Centre Marking with CNC Plasma

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First of all guys this is not a sly attempt at advertising because I'm in Australia.I'd just like some input from you guys if this feature of my plasma table could get me some odd jobs from fabrication shops. It's just me and my backyard setup so I have no idea what goes on out there in the fabrication world.I've finally perfected my hole centre marking system on my cnc plasma table. It gives the equivalent of a small centre punch mark in the top of the steel. I can cut holes with the plasma cutter, but for nice accurate holes would some fabricators prefer hole locations marked so they could accurately drill the holes.Here's a Youtube video of the table in action. I'm actually making the slats for my table on that cut.Cheers,Keith.
Reply:I used to work for a company in melbourne manufacturing longrange fuel tanks, we used to do exactly that to mark the holes for drilling on our pump mount flanges and sometimes other parts. Worked perfectly well for us although sometimes the "pierce" of the plasma would hardenthe steel and make it hard to drill. Our plasma was a hypertherm but not sure how may amps it was.Your system seems to do a much quicker job than ours though, nice work.
Reply:Mancave, very nice job on that. I am in the process of building a CNC plasma set up. Can you tell us how you did this. Did you do it in Mach3. I am not up to speed with Mach3 or even sheetcam yet but when I get my controller/motor setup from CNCandcnc.com (wireless bladerunner set up) I will want to learn how to do what you did for the "center mark" process. If this is secret to you I understand as well.Thanks.T.J.www.tjsperformance.comDynasty 300 DXHTP 240HTP Microcut 380Hyperthem 85JD2 Hyd Bender and HF Hyd Ring Roller all in one =(Frankenbender)Bpt. Mill/DRO4' x 8' CNC Plasma TableInstagram: tjsperformanceYT: TJS Welding and Fabrication
Reply:There are some cnc machines that have this exact technique built in. I would suggest checking with Tom at CandCNC if it is a standard function on his new bundles of equipment.Nice job with making yours work Keith!The dimples will have a slight nitride hardening (from the nitrogen content in air). If you use solid (not coated) Cobalt drill bits you will have no issues drilling through this. These drills cost more, but will make many more holes (so they are cheaper per hole!) and are re-sharpenable. I noticed the other day that HomeDepot now stocks some cobalt drills for a pretty low price. I buy mine from industrial suppliers, Travers Tool Co.  www.travers.com  is one of my favorites.Jim Colt  Hypertherm
Reply:Originally Posted by jimcoltThere are some cnc machines that have this exact technique built in. I would suggest checking with Tom at CandCNC if it is a standard function on his new bundles of equipment.Nice job with making yours work Keith!The dimples will have a slight nitride hardening (from the nitrogen content in air). If you use solid (not coated) Cobalt drill bits you will have no issues drilling through this. These drills cost more, but will make many more holes (so they are cheaper per hole!) and are re-sharpenable. I noticed the other day that HomeDepot now stocks some cobalt drills for a pretty low price. I buy mine from industrial suppliers, Travers Tool Co.  www.travers.com  is one of my favorites.Jim Colt  Hypertherm
Reply:Thanks for all the replies guys.The nitriding is absolutely no problem with this system. I think because the torch on time gives nothing more than a crack, the depth of nitriding is very minimal. The crater is like 1mm in diameter and not even that deep. If I'm using a small drill (normal HSS) I just use the mark as it is. At the moment I'm using a 6mm drill and I have to centre punch the craters to enlarge them, but that's pretty quick to do because the point of the centre punch fits in the crater nice with no movement. After many centre punches the point is still good so the nitrided depth musn't be thick enough hurt the centre punch.My Candcnc system (older MP3000) doesn't have this feature but I'm sure Tom will be quick to add something like this if it's not already in his latest systems. Tom is a thinker and keeps coming up with better and better systems. I can't wait till I can afford his latest one.I know Jims Plasmacam and also the larger Samson Plasmacam have something like this, but Plasmacam has their own dedicated software so maybe it can react much faster than Mach.Candcnc uses Mach3. Now I'm no Mach expert but I could never get Mach to respond fast enough to switch the torch off quick enough. That's why I designed a dedicated external circuit board to interface between Mach and my plasma cutter. Basically the circuit board is not the bottle neck timewise, the plasma cutter itself is. The board I made reacts probably within 2 milliseconds so getting the shortest possible crack from the plasma cutter is more determined by the reaction time of the plasma cutter itself. Thankfully my Hypertherm Powermax 1250 seems to react quite fast, but I have no idea if all plasma cutters are the same. I had two other electronic tricks up my sleeve if the 1250 wouldn't react fast enough but I didn't need to play with them.T.J. I'll be keeping the circuit board design itself to myself. I've put a lot of time into figuring it out, and it and if it turns out I can make a buck of it I'll certainly try. Hope nobody hates me for that LOL.However, here is the basic way that most people using Sheetcam with Mach would mark hole centres. When you have hole in your drawing you put them on a separate layer. Choose a DRILL operation not a plasma operation, but use a plasma tool within the drill operation. You'll see max. and min. hole size boxes so make sure the MIN size is set smaller than you smallest hole, and the MAX size is set larger than your largest hole. Now sheetcam will operate the torch right at the centre of the holes. In your plasma tool set the pierce height and cut height the same and have zero pierce delay. A sneaky way of creating a better (smaller) hole mark is to disconnect your ground lead for the hole marking, at least that what I've done in the past. See if any of that works for you. You could also try turning your amps right down.There is another way that required me to modify the post processor and make a dedicated macro to turn the torch on and off with different types of Mach commands but it required the post cut airflow to stop before another hole could be marked (min 10 seconds between hole marks).  I finally got sick of all the workarounds and built the interface board. Now I don't have to disconnect my ground lead, or turn the cut current down, or wait for the post cut airflow to stop, and I get the cutest little craters ever. Now I'm just waiting for the huge kick in the teeth when someone says, "Ah this is how you can do that with Mach and Sheetcam", LOL. I just did things the only way I could figure out how.Keith.