FAST HOLE CENTRE MARKING

[beefy]

It's took me a while to develop what I consider an ideal hole marking system, fast and accurate.

My system is Mach3 / Candcnc / Sheetcam / Hypertherm PM1250

For a long time, I could never figure out how to get the shortest possible crack from the plasma cutter using just Mach control. When I did find a way it required the system to wait for the plasma cutter 10 second post cut airflow to stop before I could do the next hole mark.

So I buried my head in electronics & micro-controller programming books and built an electronic board to interface between the plasma cutter and this is the result, I'm pretty happy about it.

http://www.youtube.com/watch?v=yg-s-EAqMfI

What I would love to know is have I wasted all this time and does anybody know of a way to achieve the same result without the use of an add-on external circuit. Note this is not hole centre piercing (which I detested), this is a short crack that leaves a little round divot in the top of the steel. Much more accurate and no nasty nitrided hole to drill through.

Does anyone see fabrication shops finding this type of service useful (profile cutting with hole centre marking) or is this type of service already common as muck.

Keith.

[urbnsr]

Hi Keith,

Looks nice, but I think I do the same thing using SheetCam's drilling operation, LinuxCNC and custom controller/table. I don't know MACH that well, but I don't think LinuxCNC allows the following to happen:

I usually draw a circle centered around where to "punch" the center mark and (optionally) put all these circles on a separate layer. I have a plasma tool setup for this purpose and adjust the pierce delay to match the material thickness so as to not pierce through and no delay at end of cut. After setting SheetCam's drilling operation's minimum and maximum hole size to include the circle size I drew around each center punch, that operation goes fairly fast. Drilling out is usually pretty easy and I am happy with the accuracy of the hole location at finish. I don't notice a mandatory wait for post-flow to stop before moving on to any next cut.

Hope this is of some benefit.

Paul

[beefy]

Thanks very much Paul,

I've been using the drilling operation with a plasma tool for a long time now. The issue I always had was getting the torch to be on for a short enough length of time. Mach3 / Windows never seemed to have the reaction time to switch the torch off again fast enough even with zero pierce delay. The craters (hole marks)got too deep and often started blowing out the side. They were always more like shallow holes with edge blowout, as opposed to the small shallow round crater I now get.

I wonder if Linuxcnc running in Linux reacts much faster. Mach3 has several delay issues as it is right now, for example running a macro while the torch is running causes a momentary pause in motion, as does turning the THC on and off while the torch is in motion (although I believe the Candcnc modern systems have a way round that now).

Keith.

[urbnsr]

Sorry Keith - Didn't mean to go all elementary, there. There is alot going on in LinuxCNC and I bet I've only scratched it's surface. It does use a real time kernel and it includes a program to test a computer's latency for timing settings. I can't say it's better than Mach, but the price is right!

Paul

[beefy]

Ha ha,

yeah Linux is a good price. I Googled once Mach3 vs Linuxcnc and wow there was quite a few opinions out there. I'd love to see how the other side lives and performs but I could spend most of my life just learning in this cnc game.

Needing a separate XP license for each old computer is a pain, especially when you want to have a couple of backup computers.

Keith.