[microdot]

I have a question for everybody running a CNC plasma table. Have you ever had a torch crash? How bad was it and was there any damage beyond just knocking the work piece out of alignment (relative to the work offset)? I ask this because I'm still working on my Z axis design and thought of a way to have a precision holder for the machine torch that also incorporated a break away feature in case the torch ever got hung up on, or crashed into the table or material. Before I went through the trouble and cost of making it I just wanted to see if this was a real world concern or if I was just over thinking things.

Thanks

[LeeWay]

I've had one and there was no damage because I hit the Estop at the same time it was crashing. I've only been running about a month or a little less though. I generally cut small parts out of small sheets too, so I watch the machine the whole time.
If you use larger sheets, I would say do it for sure. Then you can have some peace of mind and walk away a bit and don't have to hover over the Estop button.
I still plan on designing and installing one on mine. Torches are not cheap and a breakaway is fairly cheap insurance.

[plain ol Bill]

Yes I have experienced a torch crash and it got expensive. Broke my Hypertherm torch in half and I attribute the crash to my ignorance and being new to CNC work. I hit a tip up when moving to another part.

[jimcolt]

Torch collisions are inevitable on cnc plasma machines. In most cases the collisions can occur with small cutouts that tend to tip up in the slat bed. On high end industrial machines there is sophisticated CAM nesting software (ProNest from Cam Solutions is one of the best) that has collision avoidance...it applies start and stop points as well as torch traverse paths that avoid running over previously cut parts.

On virtually all industrial machine sold today there also is a torch collision detector/breakaway device that detects collisions, protects the torch and instantly stops motion when this ocurrs.

I use a low cost magnetic breakaway from Home Page on my home entry level cnc machine. These units sell for about $275 and will eliminate torch breakage.....paying for itself with the first plate collision. Attached is a picture of the SnapnCut mount on my machin with a Hypertherm Powermax85 torch:

Jim Colt

I have a question for everybody running a CNC plasma table. Have you ever had a torch crash? How bad was it and was there any damage beyond just knocking the work piece out of alignment (relative to the work offset)? I ask this because I'm still working on my Z axis design and thought of a way to have a precision holder for the machine torch that also incorporated a break away feature in case the torch ever got hung up on, or crashed into the table or material. Before I went through the trouble and cost of making it I just wanted to see if this was a real world concern or if I was just over thinking things.

Thanks

[LeeWay]

Can you use that with a floating torch head. I plan on making my own. It will have to be designed differently. I'm using the PM 45 hand torch.
I think a couple shallow locating pins and a few rare earth magnets with a normally closed contact switch should do the trick.
Anyone seen any home made designs to get a look at?

[LeeWay]

I did order some magnets that I think will work well with my future design. I was thinking about the contact switch though. If you are running THC, is it really necessary to have a disconnect switch there? When the torch volts go out of range, it stops all motion and the torch. That should work, but only if it's fast enough. I have no clue how many milliseconds that might take or need.
Thoughts?

[microdot]

Thanks jim. That is exactly what I had in mind. I have a few spherical neodymium magnets that I was going to use as both the locating and holding power. With an e-stop switch placed so that if the torch is knocked off even slightly this should be cheep torch insurance. I'll throw up some pics once I get the model done.

[Arthurmetal]

here is my solution for a torch break away.
A piece of steel pipe around the torch (torchbody is not magnatic) is hold in place with a swichable magnet.
Also very useful to detach the torch for maintanance.
Higher up on the torch is a hoseclamp holding a small pin keeping a microswitch pressed until the torch is tilted sideways by a collisision.
Very low budget, works perfect for me.

regards, Arthur

[Kerryfisher]

I made this one up at next to no cost apart from time, some ball bearings and an old hard drive magnet, works great.
In reply to Leeway, I was thinking I would need to fit a tether and maybe a switch but with cancnc thc it will sense a fault and shut off, I am a good bit off fully understanding it yet though!
My machine is nearly finished now, hope to add a report on it soon on here.

[partsman]

Have you ever had a torch crash? How bad was it and was there any damage beyond just knocking the work piece out of alignment (relative to the work offset)?

Yes, broke two hand-held units. About $500ea to replace

My new table is using the Snap-Cut system like Jim posted above. It is reasonably expensive and well worth the money!

[PlasmaPal]

We had a lot of torch crashes when we first bought our table. We developed a collar that clamps onto the torch and three spring feelers sense the top of the metal to prevent the THC from driving the torch down and causing a crash. Also the spring feelers can be used to probe for the top of the material at each new pierce and set the Z height to 0.

plasmapal.com

[microdot]

[QUOTE=PlasmaPal;1586734]We had a lot of torch crashes when we first bought our table. We developed a collar that clamps onto the torch and three spring feelers sense the top of the metal to prevent the THC from driving the torch down and causing a crash. Also the spring feelers can be used to probe for the top of the material at each new pierce and set the Z height to 0.

The type of crash I was asking about was during a traversing move, not a plunging move. My solution was to mount the torch to a plate that used three spherical magnets to hold it to the z axis. I can seem to fine the pictures I took of it but I do have a rendering of the SW model which is attached.

µ

[big iron]

Check out Plasma Torch Protection System | Boss Manufacturing - Home. they have everything you need to get a circuit stop control torch holder or magnetic breakaway for just about any cnc table out there.

[Kerryfisher]

This is my mk 2, they really don't take much making, been using this one for a while now, works well, one slight change since then, rather than glue the balls in position I just gave them a quick tack with tig.

DIY Breakaway torch mount - PlasmaSpider.com