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



Quote Originally Posted by z28 View Post
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.:drowning: