setting up proper grounding

[Rigo87]

I'm using the hypertherm guide on how to properly ground a cnc setup and have some questions:
1) Do I need 2 or 3 grounding rods?
2) Would the plasma have 3 grounds ( the clamp, a ground rod, and one going to ground bus)?

[jimcolt]

The earth grounding circuit is generally put in place if you have electrical noise interference that is affecting the electronics on your machine. Machines that use a plasma cutter with high voltage, high frequency start technology will be more likely to have issues with electrical noise, while machines that use air plasma cutting systems with a blowback start torch (in most cases) will run satisfactorily with no earth grounding scheme.

The guide from Hypertherm is for high frequency start plasma systems on CNC machines that experience electrical noise.

- the number of ground rods in 99.99% of the cases is one.
- The only connection to a ground rod with an air plasma cutter is the work cable connection. Industrial plasma cutters over 125 amps all use high frequency start technology, these systems often have separate starter enclosures, gas flow control enclosures, etc., and they often will require a separate ground wired from each individual component box to the earth ground connection.

Bottom line....provide details about what cnc cutting machine (brand, model, electronics uses, etc) and the plasma make and model....and I can ofer more specific advice.

Jim Colt Hypertherm

[Rigo87]

I have an Eagle Plasma table with a lotos LTP5000D, but I have plans to replace it in a few weeks with a Hypertherm Powermax 45XP. If I'm planning on changing machines do I still go forward with 2nd ground rod? Also does Hypertherm offer a machine torch for the powermax 45xp?

[Dana gear]

We installed 6 foot copper ground rods one each for each machine, never had any problems.

[jimcolt]

- the number of ground rods in 99.99% of the cases is one. Jim Colt Hypertherm

[Rigo87]

thanks Jim and all other commenters, as I get closers to getting my Hypertherm I'm sure I'll come up with more questions on how to properly setup the machine

[_Ogre]

we installed a ground rod and welded a plate to the frame to bolt a ground buss to
the clamp is the work clamp off the pm65, 1 wire to the ground rod, 1 wire to the pc table and 1 wire to a lug welded to the water tray



the lug on the table also has a short work clamp attached, we rarely clamp to the work

[tcaudle]

There are as many ways to do grounding as there are different types of plasma cutters. A lot of it depends on the plasma but some depends on the way the builder of the controls has provided for their internal grounding and the isolation of the interfaces to the table. Noise takes the shortest path to ground (lowest impedence) BUT if it has more than one path it can split and go more than one way. If your controls share a common connection with the table and plasma then noise can hop into your control or worse the PC running the machine. Tying everything in the system ot one ground rod (start ground) depends on how good the one ground really is. Not everything gest shunted to the rod and the further it is away from each of the direct runs the less effective it is. HF starts are enough of a challenge that most vendors won't even talk about how to make them work with a PC based control.