Grounding CNC Plasma

[z28]

Im a Newbie here......I just finished building my CNC Plasma Table. The table is sitting in my garage. My garage is 1600 square feet of concrete floor. Outside of the shop is also surounded by concrete. Im not sure how to go about grounding my CNC Plasma Table. I have thought about drilling a hole in the concrete and pounding a grounding rod into the floor? If so how deep do I need to go? Any Ideas? Can I ground it to a ground wire on an electrical socket going back to the fuse pannel in my home? How important is it to ground these tables? Is it a saftey issue or more to protect the electronics? Im sure many of you have ran into this same issue.....Any help would be appreciated.

[WSS]

Home depot and Lowes sell a copper clad 8ft rod that works good. We drilled through our floor and hammered the rod into the dirt. It is very important to ground these machines properly.

WSS

[johndjmix]

Im not putting anyone down, but asking...why? If the ground clamp of the plasma has a good connection to the material why does it matter?

--John

[WSS]

Plasma generators do not use ground clamps. Plasma is inherently noisy, if you do not have a proper earth ground, you risk that noise (and other things) going to things like your computer.

WSS

[johndjmix]

Ahh yes, i could see the computer getting screwed up. But, every plasma (that i know of) does have a ground clamp to clamp onto the material.

--John

[acourtjester]

The ground you are talking about is for an electrical circuit. What the others are talking about is noise riding on the electrical power and in the air from the radio frequency noise generated by the pilot start on some plasma cutters.

[WSS]

Ahh yes, i could see the computer getting screwed up. But, every plasma (that i know of) does have a ground clamp to clamp onto the material.

--John

They look like grounds, perhaps even utilize a ground clamp, but are not actually grounds like on a welder.

[Al_The_Man]

A plasma machine has to have the +ve electrode clamped or referenced to the material, which is usually also the table.
It will work like this regardless of other connections, but it is the other equipment that must be protected from stray currents that may or may not leak to Earth Ground.
All the CNC tables I have encountered have the +ve conductor bonded to the service ground and generally has a ground stake where all these are terminated, usually right at the table.
This is in order to make equipment such as PC.s or Electronic controllers that also have their power supplies referenced to earth Ground exactly at the same potential, it is called equi-potential bonding.
The last thing you want is a Plasma table that is not at earth ground where stray current may find all sorts of paths through equipment that is.
Ground rods come in all lengths, a 6ft copper plated should work, depends on the soil make up in your area.
Al.

[jimcolt]

Grounding of a cnc plasma machine is important for a few different reasons...some are safety related and some are electrical noise interference related. The level of need will vary from cnc machine to cnc machine....and also varies depending on the design of the plasma system. Also....the work lead from the plasma is not considered a "ground", rather it is the return path for the cutting current.

-Noise issues created by high frequency start plasma systems. Older technology air plasma systems (many of the import low cost air plasma systems are still produced with this technology) as well as almost all "Industrial" plasma systems use a high voltage high frequency discharge at the beginning of every start cycle to ionize the plasma gas....to start the torch. This 15,000 volt, 3 megahertz pulse can shake up low voltage motor, encoder, and computer inputs and outputs....especially of cnc machines that use a standard office computer or laptop as the machine control. The starting effect of the high frequency can simply affect the computer to the point that it will not function (reboot).....or it can literally destroy circuitry in the computer and drive electronics. Proper earth grounding, shielded computer and drive cables...as well as electronics designed with proper I/O input filtering are a must when using high frequency start plasma systems.

-Noise issues created by inverter based plasma systems. Newer technology inverter based plasma power supplies also can create electrical noise interference similar to....but not as severe as the above high frequency noise. Inverter power supplies develop a "pulse width modulated" output frequency that can be in the range of 16 khz to 60 khz (depending on power supply and manufacturer design). Typically the effect of this technology...especially on stepper driven cnc machines will be with rough motion....or strange error mesages on PC used as the machine control. Usually a good earth driven ground and proper grounding of each electronic component of the machine to the earth ground will eliminate issues when this type of plasma is used.

-Electrical grounding issues that affect height control. Poor work lead connections to the actual plate....as well as poor cutting machine frame and cutting bed ground connections can provide both safety as well as innacurate (arc voltage based) height control operation. The height control system on most CNC plasma machines is dependant on a good arc voltage reading between the material being cut (positive) and the torch electrode (negative). Poor grounding and stray cutting table voltages can and often do affect the control of torch height.


Industrial grade CNC machine all use a specifically designed hardened, shielded, isolated CNC control that is designed to not have issues with electrical noise from any type of plasma. Still....industrial tables (when properly installed) all have a dedicated ground rod for safety and operational issues.

Entry level machines that use an office PC or Laptop are far more susceptible to electrical noise and safety issues....and should always be installed with a dedicated, properly designed grounding system as well.

I have both a PlasmaCam (with Hypertherm Powermax85) and a Torchmate (with Powermax45) entry level machines in my home shop.....both have had issues with electrical noise interference. Both sets of issues were solved with proper machine grounding, a ground rod, as well as with input line conditioning (for the computers and the drive electronics) through a common UPS (uninteruptible power supply) available at office supply stores.


Hope this helps,


Jim Colt Hypertherm

Im a Newbie here......I just finished building my CNC Plasma Table. The table is sitting in my garage. My garage is 1600 square feet of concrete floor. Outside of the shop is also surounded by concrete. Im not sure how to go about grounding my CNC Plasma Table. I have thought about drilling a hole in the concrete and pounding a grounding rod into the floor? If so how deep do I need to go? Any Ideas? Can I ground it to a ground wire on an electrical socket going back to the fuse pannel in my home? How important is it to ground these tables? Is it a saftey issue or more to protect the electronics? Im sure many of you have ran into this same issue.....Any help would be appreciated.

[Al_The_Man]

Some time ago I was involved in servicing some local MG Systems plasma tables that that used the Acroloop PC based motion card and S/W.
It was important to maintain the common Earth ground to both table (+ve) electrode and the PC and service ground and use a ground rod at the table where all were terminated.
I subsequently installed my own versions of the Acroloop SW and followed these practices and never had any issues with noise problems.
Al.

[tjbaudio]

This brings up a question for nonCNC use. I am planning on adding a Hypertherm Powermax45 and a small wire welder (Lincoln or miller 140) to my current 50ish year old AC stick welder (Marquet, looks like a green trash can).

Power is a 100 A 4 wire panel with local ground rod buried 2 ft directly under the breaker panel along with a ground run to the main house panel (bonded to 2 ground rods, water and gas mains)

I have the welding table grounded to the AC welder threw heavy cable. I also have a heavy ground clamp on 20 ft of wire bolted to the table so I can work on stuff not clamped to the welding table.

I was going to also bond the work side clamps of the new plasma and wire welder to said table. Thus one heavy clamp or steel table acts as my work ground. Is this going to cause me problems? Will I have to change clamps around depending on what tool I am using?

Thank you.

[jimcolt]

Should work just fine....that is similar to the grounding on my welding table....which has a Powermax45 and a Millermatic 250 mig.


Jim

This brings up a question for nonCNC use. I am planning on adding a Hypertherm Powermax45 and a small wire welder (Lincoln or miller 140) to my current 50ish year old AC stick welder (Marquet, looks like a green trash can).

Power is a 100 A 4 wire panel with local ground rod buried 2 ft directly under the breaker panel along with a ground run to the main house panel (bonded to 2 ground rods, water and gas mains)

I have the welding table grounded to the AC welder threw heavy cable. I also have a heavy ground clamp on 20 ft of wire bolted to the table so I can work on stuff not clamped to the welding table.

I was going to also bond the work side clamps of the new plasma and wire welder to said table. Thus one heavy clamp or steel table acts as my work ground. Is this going to cause me problems? Will I have to change clamps around depending on what tool I am using?

Thank you.