[jwweathers]

Hello. I am new to the forum. I recently built a 4' x 4' plasma table with a floating head. I am using Mach3 to drive the table and my plasma machine is a TD Cutmaster 52. Everything is working great.

However, I would like to incorporate an ohmic sensor to my machine. The floating head works great for initial height sensing the majority of time with the exception of when I cut thin gauge material. Hence, I would like to install the ohmic sensor. Below is pic of the machine that I built. Also, I have included a diagram of the ohmic sensor I plan to incorporate. I would really appreciate comments/criticism/whatever. Are there improvements? Will I fry my BOB?

Thanks,
Jeff

[jwweathers]

Hello. I am new to the forum. I recently built a 4' x 4' plasma table with a floating head. I am using Mach3 to drive the table and my plasma machine is a TD Cutmaster 52. Everything is working great.

However, I would like to incorporate an ohmic sensor to my machine. The floating head works great for initial height sensing the majority of time with the exception of when I cut thin gauge material. Hence, I would like to install the ohmic sensor. Below is pic of the machine that I built. Also, I have included a diagram of the ohmic sensor I plan to incorporate. I would really appreciate comments/criticism/whatever. Are there improvements? Will I fry my BOB?

Thanks,
Jeff

Anybody??

[Greolt]

I'm interested in what you are trying to do.

My first thought is that as soon as the plasma is started you will fry the 12v power supply.

Nice little table you have built. How are you coping with the mess created?

[jwweathers]

I'm interested in what you are trying to do.

My first thought is that as soon as the plasma is started you will fry the 12v power supply.

Nice little table you have built. How are you coping with the mess created?

Thanks. I don't think that would happen only because the shield cap is floating. That is the sort of thing I am worried about, though. For instance, I supposed the plasma could arc to the shield cap??? That is what I need help with, but the experts here seem reluctant.

I assume you mean the mess from cutting. I am using a broom.

[jimcolt]

Normally you use the shield to ohmically sense the material....the shield will be connect through an isolation relay (300 VDC rated contacts)......and open the relay after the plate is sensed, and before the torch fires, you will have to figure out how to time the relay via your machine code and I/O capability on your machine. This will make the electronics live if the shield gets shorted to the nozzle from pierce splatter. Jim Colt Hypertherm

Thanks. I don't think that would happen only because the shield cap is floating. That is the sort of thing I am worried about, though. For instance, I supposed the plasma could arc to the shield cap??? That is what I need help with, but the experts here seem reluctant.

I assume you mean the mess from cutting. I am using a broom.

[jwweathers]

Normally you use the shield to ohmically sense the material....the shield will be connect through an isolation relay (300 VDC rated contacts)......and open the relay after the plate is sensed, and before the torch fires, you will have to figure out how to time the relay via your machine code and I/O capability on your machine. This will make the electronics live if the shield gets shorted to the nozzle from pierce splatter. Jim Colt Hypertherm

Jim,

Thanks for the reply. So I think you are recommending that I add a relay which would isolate the 12V power supply from the torch when I am not interested in ohmic sensing. Is that accurate?

Thanks,
Jeff

[jimcolt]

correct. Jim Colt

Jim,

Thanks for the reply. So I think you are recommending that I add a relay which would isolate the 12V power supply from the torch when I am not interested in ohmic sensing. Is that accurate?

Thanks,
Jeff