In the realm of CNC plasma machines, proper grounding is paramount for safe operation and reliable performance. However, many off-the-shelf CNC kits overlook the crucial aspect of grounding, resulting in the static buildup and electrical noise. This excess electricity can lead to interruptions and even safety hazards in machine operation.
To compound the issue, CNC machines often operate in electrically noisy environments, surrounded by high-powered machinery and motors. This noise can cause significant problems and wreak havoc on the machine’s motion controller.
This blog aims to address these challenges by exploring the most common grounding issues associated with CNC machines and providing tested solutions to enhance the machine’s safety and reliability.
Reasons to Invest in Proper Grounding
If you want to keep your machine running safely, grounding is a must. Without grounding, you’re just asking for trouble.
Avoiding a live chassis – First and foremost, you need to ground the machine frame. This is crucial for routing fault currents to earth ground in case a component or cable fails and shorts to the chassis. If you don’t ground the frame, you could be in serious trouble if your chassis becomes live.
Stopping static buildup – CNC routers can generate some serious static charges, especially when working on dry materials like wood. Static can cause malfunctions in the controller and create shock hazards. It can even ignite dust in the atmosphere, leading to potential explosions or fires.
Eliminating electrical noise – CNC machines use motors and high-frequency signals that can cause interference with other devices in proximity. It can lock up or cause errors in the controller, computer, and other devices. With proper grounding, most of this noise will be shunted to the ground, eliminating most of the problems.
Prevent performance problems – Now, if your machine is a plasma cutter or contains a VFD spindle, grounding becomes even more important. With the huge amounts of electrical noise generated by these machines, proper shielding and grounding are a must for avoiding performance and reliability issues.
How to Create a Grounding System
To properly install a grounding system for your CNC machine, the first step is to install a single point ground (SPG) – a screw stud or terminal bar where all the ground wires from the machine come together. Connect the incoming power cord’s safety ground to the SPG point.
Next, ground each moving part of the machine separately to the SPG point. These connections ensure a low resistance path for current and eliminate insulating or intermittent mechanical connections that can cause fault currents or electrical noise issues. Take off any coatings or paints at the connection points; you can use a star washer to penetrate any oxides or coatings for efficient removal.
To ensure good electrical contact, use proper ring tongue terminals and star washers on both ends of each ground wire. For easy identification, use 14 gauge green or green/yellow wires.
If a grounding bar is used instead of a stud, you need to mount it firmly to the main chassis with tooted or star washers for good contact. Properly size the terminals for the wire and mounting screw used, and crimp on correctly using the right crimping tool.
Directly connecting the main ground from the power cable to the SPG ground bar or stud is critical. It should be separated from all other wires by a separate nut on the stud, ensuring that the grounding is secure and effective. Place all other ground wires at the top of this connection, ideally with a star washer between their terminals for good contact. Use a double nut or lock nut on top to prevent loosening.
Since most kits now have no access to the ground terminal on the power cord, the main ground stud can be connected to the power supply case for an adequate ground connection. Alternatively, cut the plug end off the power cord and wire a good aftermarket plug to the cable, attaching a separate ground wire from the single point ground to the third prong in the plug along with the ground wire from the cord.
Following these steps, you can ensure that your CNC machine is properly grounded, with a low resistance path for current, no insulating or intermittent connections, and good electrical contact at every point.
Cable Routing and Dust Collection
Noise from power cables of devices such as plasma cutters can cause EMI/RFI emissions. Put these cables at a distance from the control wiring or low voltage on the machine. You can plug them into a separate electrical circuit from your machine electronics and PC to reduce interference. It’s also a good idea to use ferrite beads on the power cables—they should lower the noise further.
External dust collection can also cause problems. Swift air flow through a plastic hose produces an electrical charge of static that is capable of arcing over, leading to EMI/RFI that could potentially wreak havoc on the optimal operation of your CNC plasma machine and cause safety hazards. It is absolutely imperative that your dust collection system be grounded in a meticulous manner, especially if using plastic hoses. Failure to do so could have catastrophic consequences.
Metal piping and parts should be grounded. Plus, you should spiral wrap any tubing or plastic hose connected to the machine using ground wire. If there’s a metal spring wire on the hose, connect it to the ground at one end. You can get dust collection grounding kits from a nearby woodworking store and install them on your system.
Conclusion
Grounding is crucial for the safe and efficient operation of CNC plasma cutting systems. Proper grounding helps minimize the risk of electrical interference, arcing, or fire hazards and can significantly improve the reliability of your machine.
Proper grounding is an investment in your personal safety and the longevity of your CNC plasma machine.
by