[gzm.pepe]

I want to use this option in my plasma table machine, anyone know what is required to use this option?

[jimcolt]

Ohmic contact is a method of finding the surface of the plate before the cut starts. It senses electrical contact between the torch shield (the wire connection shown in your picture connects to the electronics on the machine, and to the shield on the torch). When contact is made the height control records that as (0) for the surface...then retracts to the pierce height for piercing. After the pierce is complete, the z axis indexes the torch to the cut height....then after x and y motion achives programmed speed...the arc voltage feedback height control takes over for maintaining torch to work distance accurately. The Ohmic contact is only for finding the plate surface initially......however some height control manufacturers also use it during arc voltage control to sense plate collisions (if you go to the Hypertherm website Choose your region and language | Hypertherm and look at automation products, then torch height controls ...these systems all use ohmic sensing...as it was first used on Hypertherm systems.

The picture you show is a kluged ohmic wire connection. In reality...you should use the retaining cap that has a built in wire spade terminal for this connection. Attached are drawings of Hypertherm consumables...the top set is for use with an Ohmic plate sensor. If you tell me what brand and model cnc machine you have...I can guide you regarding the availability of ohmic sensing.

Jim Colt

I want to use this option in my plasma table machine, anyone know what is required to use this option?

[gzm.pepe]

Ohmic contact is a method of finding the surface of the plate before the cut starts. It senses electrical contact between the torch shield (the wire connection shown in your picture connects to the electronics on the machine, and to the shield on the torch). When contact is made the height control records that as (0) for the surface...then retracts to the pierce height for piercing. After the pierce is complete, the z axis indexes the torch to the cut height....then after x and y motion achives programmed speed...the arc voltage feedback height control takes over for maintaining torch to work distance accurately. The Ohmic contact is only for finding the plate surface initially......however some height control manufacturers also use it during arc voltage control to sense plate collisions (if you go to the Hypertherm website Choose your region and language | Hypertherm and look at automation products, then torch height controls ...these systems all use ohmic sensing...as it was first used on Hypertherm systems.

The picture you show is a kluged ohmic wire connection. In reality...you should use the retaining cap that has a built in wire spade terminal for this connection. Attached are drawings of Hypertherm consumables...the top set is for use with an Ohmic plate sensor. If you tell me what brand and model cnc machine you have...I can guide you regarding the availability of ohmic sensing.

Jim Colt

Thank you Jim, some days ago I emailed hypertherm Mexico asking for the cost an diferences of the 3 models of THC from hypertherm, but no answer yet,
Im looking for other options while waiting, Im making CNC plasma/oxyfuel tables for local workshops in my city in Mexico, I still looking for a good option and good cost for THC

[Torchhead]

To use ohmic sensing you have to have a THC that will take that signal in for IHS. Because it can be unreliable on rusty or coated material you HAVE to have a backup system that will keep your THC from driving the torch down hard enough to break the end off (it has happened) If you invest in a standalone THC where the torch axis runs independent from the toolpath then one method of backup is to sense the current in the lifter motor (called torque feedback) and stop the motor if it meets too much resistance thereby saving the torch. That method is elegant but needs to be set by the operator and is costly. It only works if the TH has direct control of the lifter motor

Another method is to build in a "shock absorber" that will let the torch lift up and trip a limit switch if the ohmic fails. it's called a "floating torch holder". If you have that feature than you really don't need ohmic sensing because you can just as easily use the floating torch holder to act as the primary touch-off as well as the fail safe.

How you do IHS is totally dependent on what the THC you chose can use. the important thing is that you DO the IHS in the pierce and cut process.

TOMcaudle
www.Candcnc.com

[gzm.pepe]

To use ohmic sensing you have to have a THC that will take that signal in for IHS. Because it can be unreliable on rusty or coated material you HAVE to have a backup system that will keep your THC from driving the torch down hard enough to break the end off (it has happened) If you invest in a standalone THC where the torch axis runs independent from the toolpath then one method of backup is to sense the current in the lifter motor (called torque feedback) and stop the motor if it meets too much resistance thereby saving the torch. That method is elegant but needs to be set by the operator and is costly. It only works if the TH has direct control of the lifter motor

Another method is to build in a "shock absorber" that will let the torch lift up and trip a limit switch if the ohmic fails. it's called a "floating torch holder". If you have that feature than you really don't need ohmic sensing because you can just as easily use the floating torch holder to act as the primary touch-off as well as the fail safe.

How you do IHS is totally dependent on what the THC you chose can use. the important thing is that you DO the IHS in the pierce and cut process.

TOMcaudle
www.Candcnc.com

Tom thank you very much everything is more clear now

[larryy1022]

Is that you Jose?

I havent been this forum quite a long time.
The torch retaining cap IHS works just as Jim said, and our THC uses ohmic contact for anti-collision checking as he said too -).

As to the backup when u cut painted/rusty steel, the proximity switch IHS will do the work. So u got nothing to worry abt...
Just wire it up as the instruction manual.
proximity switch IHS is always ok, but its accuracy is not good as ohmic contact.

look forward to your testing result

Larry

[gzm.pepe]

Is that you Jose?

I havent been this forum quite a long time.
The torch retaining cap IHS works just as Jim said, and our THC uses ohmic contact for anti-collision checking as he said too -).

As to the backup when u cut painted/rusty steel, the proximity switch IHS will do the work. So u got nothing to worry abt...
Just wire it up as the instruction manual.
proximity switch IHS is always ok, but its accuracy is not good as ohmic contact.

look forward to your testing result

Larry

Thank you Mr. Larry I was posted this before before having the thc, I'm working right now in the installation