Another plasma component...

I just shared some info on external offsets for our plasma primer

phillc54 wrote:

I have had the torch airflow running after the cut but when I go to probe I get the ohmic probe detected while moving to probe height error.

Hmm, airflow "shouldn't" have any effect on probe detection, I don't know why that would be...

I think the cause was that there was already water inside the shield and it could not get out before the Ohmic probe detect feature came on. The air flow must not have been enough to remove all the water bridging the nozzle and shield.

When that was happening If I took off the shield and blew it dry it would work again.

Guys

The ohmic probe tripped while moving is the most common cause I have for stoppage. It is always caused by either water or slag (dross) shorting the nozzle to the shield. It is particularly bad when using the Finecut consumables because of the large gap between the shield and the nozzle. Many times I can fix the problem with just a finger over the shield opening while the post flow is still on using the airflow to blow the water out then restarting with the pause/resume button. If that doesn't work then I have to take off the shield and clean/dry between the shield and nozzle. A way to change probing methods from Gcode and the GUI will be a big help for the job shop crowd. I am stuck with ohmic because of the thinish material I cut.

'03

I figured that the standard consumables would be much less susceptible to this problem. I think when you put the anti dive snippet in your CAM before the end of cut it will help but not eliminate this problem. You can also increase your safe height so the torch travels higher on rapids. On the thicker material you are cutting at slow speed you really have no need for ohmic sensing anyway so just use the float switch. I am sure this is why HT has at least two probing methods on their machines Z axis. Sorry you had so much trouble getting the Z speed and accelerations correct. I think that many of us that have been around the EO branch just take the correct setup for granted.

John

Phill,

I'm working on a post processor for Fusion 360 and just wanted to be certain I have this straight regarding the use of the M67 code. I'm working on a way to slow down cutting and stop THC compensation for small circles. For whatever reason, Fusion 360 CAM in the cutting 2-d profiling mode for plasma does not seem to always use a G2/G3 to do circles but rather makes a number of small linear moves. I was planning on just adjusting the speed by looking at the radius of the circle but that is not an option so I am having to think about alternate methods. Right now, I have something that might work though it is going to be a little unconventional in the g-code it creates. Please consider the following g-code snippet:


The first command would read/set the feed rate and the second would change it to 60%. My question is, what will that third command do? Will it reset back to the original feed rate or will it be essentially ignored? When I read the documentation, I'm led to believe that you have to do an M67 E3 Q100 to get back to the original feed rate.

Thanks for the help. I'll be happy to share my post processor if I can get it working.

Steven

Steven, at the end of the hole, do a M67 E3 Q0 to restore adaptive feed to 100% I don't think the feedrate will do what you expect with adaptive feed active. See linuxcnc.org/docs/devel/html/plasma/plas...user-guide.html#_thc

(So cool to have documents to refer people to )

Here is a complete snippet for an example

islander261 wrote:

Guys

The ohmic probe tripped while moving is the most common cause I have for stoppage. It is always caused by either water or slag (dross) shorting the nozzle to the shield.

With my old CandCNC feather touch ohmic probe I did not have these problems given the exact same running conditions,

I am not that great with electronics but I have read something in the past that said the big manufactures have a way to set the sensitivity of the Ohmic probe circuit, How would something like that work for our setup?