60+ terms defined — from arc voltage and dross to THC and kerf width. A plain-language reference for anyone shopping for, setting up, or operating a CNC plasma table.
This glossary covers the essential terminology you'll encounter when researching, purchasing, and operating a CNC plasma cutting table. Terms are grouped alphabetically with cross-links to our guides and interactive tools where applicable.
A type of plasma cutting system that uses compressed shop air as both the plasma gas and the shield gas. Air plasma cutters are the most common and affordable option for CNC tables, suitable for cutting mild steel, stainless steel, and aluminum. They produce a slightly rougher edge than systems using specialty gases but require minimal infrastructure.
The measure of electrical current flowing through the plasma arc, directly determining cut thickness capability and speed. Higher amperage means thicker cutting capacity — a 45-amp system quality-cuts about 1/4-inch steel, while a 125-amp system handles over 1 inch. Choose amperage based on your thickest material needs.
The distance between the tip of the plasma torch nozzle and the surface of the workpiece during cutting. Maintaining the correct arc gap (also called standoff distance) is critical for cut quality. Too close risks nozzle contact and double arcing; too far causes a wide, sloppy kerf. A torch height controller (THC) automatically maintains proper arc gap.
The method used to initiate the plasma arc. The three common types are high-frequency (HF) start, blow-back start, and pilot arc start. High-frequency start can cause electromagnetic interference with CNC electronics, so pilot arc and blow-back start systems are strongly preferred for CNC plasma tables.
The electrical voltage measured across the plasma arc during cutting. Arc voltage is directly proportional to the arc gap distance, making it the primary feedback signal used by torch height controllers (THC) to maintain correct standoff height. Typical cutting arc voltages range from 90V to 200V depending on amperage and material.
A shielding gas mixture of 65% argon and 35% hydrogen, used in high-definition plasma systems for cutting stainless steel and aluminum. H35 produces the smoothest, most oxide-free edges on non-ferrous metals but requires a more expensive plasma system capable of dual-gas operation.
Unwanted mechanical play or looseness in the drive system of a CNC table, typically occurring in rack-and-pinion or lead screw mechanisms. Backlash causes inaccuracies when the gantry or torch carriage reverses direction — circles come out egg-shaped and corners overshoot. Quality tables minimize backlash through anti-backlash nuts, preloaded pinions, or servo drives with encoder feedback.
An angled edge on a plasma-cut part where the cut face is not perfectly perpendicular to the material surface. Some bevel is inherent in plasma cutting due to the shape of the arc — typically 1 to 3 degrees on the "good" side and more on the scrap side. Excessive bevel indicates incorrect cut speed, amperage, or arc height.
A torch mount designed to separate from the Z-axis carriage on impact, preventing damage if the torch collides with the workpiece, a clamp, or a warped plate. Most CNC plasma tables include a magnetic or spring-loaded breakaway mount as standard safety equipment.
Computer-Aided Design — software used to create 2D drawings or 3D models of the parts you want to cut. Popular CAD programs for CNC plasma work include Fusion 360, AutoCAD, Inkscape, and CorelDRAW. The design is exported as a DXF or SVG file and then imported into CAM software to generate cut paths.
Computer-Aided Manufacturing — software that converts your CAD drawing into G-code tool paths the CNC machine can follow. CAM software handles lead-ins, lead-outs, kerf compensation, pierce points, and cut order. Popular CAM programs for plasma include SheetCAM, Fusion 360 (manufacturing workspace), and ProNest.
Computer Numerical Control — the automated control system that drives a plasma cutting table. A CNC controller reads G-code instructions and translates them into precise motor movements along the X, Y, and Z axes. This allows the torch to follow complex cut paths with repeatable accuracy, making it possible to produce identical parts from digital files.
The most common gas supply for air plasma cutting systems. A CNC plasma setup typically requires a dedicated air compressor delivering clean, dry air at 80 to 120 PSI. Moisture, oil, or particulates in the air supply are the leading cause of premature consumable failure — an inline dryer and filter are essential.
The replaceable wear parts inside a plasma torch — electrode, nozzle, swirl ring, shield cap, and retaining cap. Consumables degrade with each cut cycle and must be replaced regularly to maintain cut quality. A typical electrode and nozzle set lasts 1 to 3 hours of actual arc-on time depending on amperage and material.
A reference table provided by the plasma power supply manufacturer listing recommended settings for each material type and thickness. Cut charts specify amperage, arc voltage, cut speed (IPM), pierce height, cut height, gas type, gas pressure, and pierce delay. Always start with the manufacturer's cut chart and fine-tune from there.
The rate at which the plasma torch travels along the cut path, measured in inches per minute. Correct cut speed is critical — too fast produces dross on the bottom edge, too slow causes top-edge dross and excessive heat input. Optimal speed varies by amperage, material type, and thickness. Also called feed rate or travel speed.
The amperage of the plasma arc during the actual cutting process, as opposed to the pilot arc current. Cutting current is set based on material type and thickness according to the plasma unit's cut chart. Reducing cutting current below the rated range shortens consumable life and degrades cut quality.
A CNC plasma table with a ventilation system built into the cutting surface that pulls smoke and fumes downward through the slat bed into a collection plenum, then exhausts them through ductwork or a filtration unit. Downdraft tables keep the work area cleaner than water tables but cost more to install and operate.
Resolidified molten metal that adheres to the bottom edge of a plasma-cut part. Dross indicates incorrect cut parameters — high-speed dross (small, hard beads) means you're cutting too fast; low-speed dross (thick, bubbly) means you're cutting too slow. Properly dialed-in settings produce parts with zero or easily removable dross.
The percentage of a 10-minute period that a plasma cutter can operate at its rated output before needing to cool down. A 60% duty cycle at 65 amps means 6 minutes of cutting and 4 minutes of rest. Industrial CNC plasma systems typically offer 100% duty cycle at rated amperage for uninterrupted production cutting.
Drawing Exchange Format — the standard 2D file format for CNC plasma cutting. DXF files contain vector geometry (lines, arcs, circles, polylines) that CAM software converts into G-code cut paths. Most free and commercial CNC design libraries distribute files in DXF format. Created by Autodesk, supported by virtually all CAD/CAM software.
The smoothness and squareness of the cut face on a plasma-cut part, typically rated on a scale from 1 (roughest) to 5 or by ISO 9013 ranges. Edge quality depends on cut speed, amperage, arc height, consumable condition, and gas type. High-definition plasma systems produce near-laser-quality edges (ISO Range 2-3) on thin material.
The primary consumable inside a plasma torch, containing a small insert (usually hafnium for air plasma or tungsten for specialty-gas systems) that emits the electron stream forming the plasma arc. The hafnium insert slowly erodes with each arc start — when the pit depth exceeds about 0.040 inches (1 mm), the electrode must be replaced.
Electrical noise generated by the high-frequency, high-voltage plasma arc that can disrupt CNC electronics, computer signals, and communication cables. EMI is the main reason high-frequency arc start systems are avoided on CNC tables. Proper grounding, shielded cables, and ferrite chokes help mitigate EMI from pilot-arc systems.
The speed at which the CNC gantry moves the torch along the cut path, synonymous with cut speed. Feed rate is specified in inches per minute (IPM) or millimeters per minute (mm/min) and is one of the most critical parameters for achieving clean, dross-free cuts.
A plasma cutting mode (also called FineCut or precision plasma) that uses lower amperage, specialized consumables, and tighter arc constriction to produce higher-quality edges on thinner materials (typically under 1/4 inch). Fine-cut consumables are a separate set from standard consumables and are available on systems like the Hypertherm Powermax.
The system used to capture and remove hazardous smoke, particulates, and metal fumes generated during plasma cutting. The two main approaches are water tables (which trap fumes in water) and downdraft ventilation (which pull fumes into ductwork). Proper fume extraction is essential for operator safety and OSHA compliance.
The standardized programming language that CNC machines use to control motion and operations. G-code files contain instructions for torch position (X, Y, Z coordinates), feed rate, arc start/stop, and pierce sequences. CAM software generates G-code from your DXF designs — most operators rarely need to write or edit G-code directly.
The bridge-shaped structure that spans the width of a CNC plasma table and carries the torch carriage along the Y-axis. The gantry rides on rails along the X-axis (table length). Gantry rigidity and weight directly affect cut accuracy — a flimsy gantry vibrates at high speeds, degrading edge quality and dimensional accuracy.
The electrical connection (also called work clamp or work lead) that completes the plasma circuit by attaching to the workpiece or the cutting table. A solid, clean ground connection is essential — poor grounding causes erratic arc behavior, difficulty starting, and inconsistent cut quality. Always clamp directly to clean, bare metal.
The area of base metal adjacent to the cut edge that has been heated enough to change its microstructure and mechanical properties, but not melted. Plasma cutting produces a wider HAZ than laser cutting. On hardened or heat-treated steels, the HAZ can cause brittleness or softening near the cut edge.
The method a CNC plasma table uses to detect the material surface before piercing. Common types include ohmic sensing (electrical contact), capacitive sensing, and float switch (mechanical contact). Accurate height sensing ensures consistent pierce height and prevents torch crashes on warped material. See also: THC, Ohmic Sensing.
An advanced plasma cutting technology (also called HD plasma or HyPerformance) that uses tighter arc constriction, higher energy density, and dual-gas systems to produce cut quality approaching fiber laser on materials under 1/2 inch. HD plasma systems cost significantly more than conventional air plasma but deliver superior edge quality, tighter tolerances, and longer consumable life.
The reference point (typically one corner of the cutting table) where the CNC machine returns to establish its coordinate zero. The machine homes to this position at startup using limit switches or hard stops to calibrate its position in X, Y, and Z. Also called the machine origin or zero point.
The standard unit of measure for plasma cut speed and CNC rapid traverse speed in North America. A 65-amp plasma cutter quality-cuts 1/4-inch mild steel at approximately 100 to 120 IPM, while 1/2-inch steel drops to about 40 to 50 IPM. Cut charts list recommended IPM for every material and thickness combination.
The width of material removed by the plasma arc during cutting — essentially the width of the cut itself. Plasma kerf is typically 0.040 to 0.080 inches (1 to 2 mm) for standard systems, and narrower for high-definition plasma. CAM software applies kerf compensation to offset the tool path so finished parts come out at the correct dimensions.
An offset applied in CAM software that shifts the cut path outward (for external contours) or inward (for internal holes) by half the kerf width. Without kerf compensation, every part would be undersized by the kerf width. Most CAM programs like SheetCAM and Fusion 360 handle this automatically once you enter the kerf value.
A short approach path that the torch follows from the pierce point to the actual cut contour. Lead-ins are typically arcs or short straight lines that start outside the part boundary and sweep into the cut line at a tangent. This ensures the rough pierce mark is on the scrap side, not on the finished part edge.
A short exit path at the end of a contour cut where the torch continues past the starting point before extinguishing the arc. Lead-outs prevent a small divot or notch at the start/end junction of the cut. Like lead-ins, they are configured in CAM software and route into the scrap side of the material.
A sensor mounted at the ends of each axis of travel (X, Y, and sometimes Z) that tells the CNC controller when the gantry or carriage has reached its maximum position. Limit switches prevent the machine from driving past its physical boundaries and are used during the homing sequence to establish the machine's coordinate zero.
Precision-ground steel guide rails that the CNC gantry and torch carriage ride on, providing smooth, accurate, and low-friction motion. Quality CNC plasma tables use linear rails with recirculating ball bearing carriages on at least the Y-axis (torch carriage). Linear rails offer significantly better precision and longevity than V-wheels or roller bearings.
Popular Windows-based CNC controller software from Newfangled Solutions used to drive many hobby and mid-range CNC plasma tables. Mach3 is the legacy version (still widely used); Mach4 is the modern replacement with improved plugin architecture and multi-core support. Both read G-code and control stepper or servo motors via a breakout board.
The system of gauge numbers used in the US to specify sheet metal thickness. Common gauges for CNC plasma cutting: 18 gauge (0.048 in / 1.2 mm), 16 gauge (0.060 in / 1.5 mm), 14 gauge (0.075 in / 1.9 mm), 12 gauge (0.105 in / 2.7 mm), 10 gauge (0.135 in / 3.4 mm). Thicker material is specified in fractions of an inch (1/4 in, 3/8 in, 1/2 in, etc.).
The process of arranging multiple parts on a sheet of material to minimize waste. Nesting software (like ProNest, SigmaNEST, or the nesting features in SheetCAM) automatically rotates and positions parts to maximize material utilization. Efficient nesting can reduce scrap by 10 to 20% compared to manual part placement.
A shield gas and plasma gas used in higher-end plasma systems, primarily for cutting stainless steel and aluminum. Nitrogen produces cleaner, more oxide-free edges than compressed air on non-ferrous metals. It is also used as the shield gas in many dual-gas configurations paired with oxygen plasma gas for mild steel cutting.
The copper consumable at the tip of the plasma torch that constricts the plasma arc into a focused, high-energy cutting stream. Nozzle orifice diameter determines the arc width and is matched to the amperage setting — using the wrong nozzle size causes poor cut quality and rapid consumable wear. Nozzles are the fastest-wearing consumable and should be inspected regularly.
An electrical surface-detection method where a small voltage is applied through the torch nozzle. When the nozzle touches the workpiece, the circuit is completed and the controller registers the material surface height. Ohmic sensing is faster and more accurate than mechanical float switches but requires clean, electrically conductive material. It does not work through rust, paint, or coatings.
A plasma gas used for cutting mild steel (carbon steel). Oxygen plasma produces the cleanest, squarest edges and fastest cut speeds on mild steel because it creates an exothermic reaction with the iron — the metal actually burns, adding energy to the cut. Oxygen is the preferred plasma gas for production-quality mild steel cutting but is not used for stainless or aluminum.
A thermal cutting process that uses an oxygen-fuel flame (typically acetylene or propane) to preheat metal to its ignition temperature, then blasts it with a jet of pure oxygen to burn through. Oxy-fuel is slower than plasma and only works on carbon steel, but it handles extremely thick material (up to 12+ inches) and requires far less electrical power. Some CNC tables support both plasma and oxy-fuel torches.
The process of penetrating through the full thickness of the material to start a cut in the middle of a plate (as opposed to starting from an edge). Piercing subjects the consumables and torch to the most stress — dwell time, pierce height, and pierce current must be set correctly to avoid blowback that damages the nozzle and shield cap.
The programmed pause (in seconds or milliseconds) after the arc fires and before the torch begins moving along the cut path. Pierce delay gives the arc time to fully penetrate the material. If the delay is too short, the torch starts moving before the pierce is complete, resulting in a missed cut or an incomplete lead-in.
The standoff distance between the torch nozzle and the material surface at the moment of piercing, typically 1.5x to 2x the normal cut height. The extra height during piercing protects the nozzle from molten metal splashback. After the pierce delay, the torch lowers to cut height and begins following the cut path.
A low-current arc formed between the electrode and nozzle inside the torch body before transferring to the workpiece. The pilot arc ionizes the gas stream so the main cutting arc can jump to the material without requiring high-frequency starting. Pilot arc systems are standard on CNC-compatible plasma cutters because they eliminate EMI from high-frequency start circuits.
The gas that is ionized to form the plasma arc — typically compressed air, oxygen, or nitrogen depending on the material being cut. The plasma gas carries the electrical current and provides the cutting energy. Different plasma gases produce different edge qualities, cut speeds, and consumable life on different materials.
A configuration file or plugin within CAM software that formats G-code output to match the specific requirements of your CNC controller (Mach3, Mach4, LinuxCNC, FlashCut, etc.). The post processor ensures that arc start/stop commands, THC signals, pierce delays, and coordinate formatting match what your controller expects. Using the wrong post processor can cause failed cuts or machine errors.
A linear drive mechanism consisting of a toothed gear (pinion) meshing with a toothed rail (rack) to convert rotary motor motion into linear motion. Rack-and-pinion drives are the most common drive system on CNC plasma tables larger than 2x2 because they offer high speed, high force, and unlimited travel length. Quality systems use helical racks and preloaded pinions to minimize backlash.
The maximum speed at which the CNC gantry travels between cuts when the torch is not cutting (also called rapid traverse or G0 moves). Rapids affect total job time — a table with 1,000 IPM rapids completes a multi-part nested job significantly faster than one limited to 300 IPM, even if actual cut speeds are identical.
The maximum material thickness a plasma system can cut through, regardless of edge quality. Sever cut thickness is typically 1.5x to 2x the rated quality cut thickness. A 65-amp system might quality-cut 5/8-inch steel but sever-cut up to 1 inch. Sever cuts have rough edges, heavy dross, and significant bevel — they are for separation, not finished parts.
The outermost consumable on a plasma torch that surrounds the nozzle and directs the shield gas flow. The shield cap protects the nozzle from molten metal splashback during piercing and helps focus the shield gas around the arc. Shield caps wear slower than nozzles and electrodes but should be replaced when damaged, cracked, or heavily pitted.
A secondary gas that flows around the outside of the plasma arc to protect the cut zone and influence edge quality. Common shield gases include compressed air, nitrogen, CO2, or a nitrogen-CO2 mix. Shield gas selection affects edge oxidation, dross formation, and top-edge rounding. Dual-gas plasma systems allow independent control of plasma gas and shield gas.
A general term for the waste material produced during plasma cutting — including dross, spatter, and resolidified metal. Slag accumulates on the cutting table slats, in the water table pan, or on the downdraft plenum. Regular slag removal is part of routine CNC plasma table maintenance.
An electric motor that moves in precise, fixed angular increments (steps), commonly used to drive the X, Y, and Z axes on entry-level and mid-range CNC plasma tables. Stepper motors are affordable and require no encoder feedback, but they can lose steps under heavy load or at very high speeds, which causes position drift. Compare with servo motors for higher-performance applications.
A closed-loop electric motor with an encoder that continuously reports its position back to the CNC controller. Servo motors provide higher speed, higher torque, better acceleration, and guaranteed positional accuracy compared to stepper motors. They are standard on industrial CNC plasma tables and increasingly common on prosumer machines. The tradeoff is higher cost and more complex tuning.
A consumable inside the plasma torch that imparts a swirling motion to the plasma gas before it passes through the nozzle. The vortex action constricts and stabilizes the arc, improving cut quality and consumable life. Swirl rings wear slowly and are typically replaced every 3 to 5 electrode and nozzle changes.
An electronic system that automatically adjusts the Z-axis position of the plasma torch during cutting to maintain a consistent arc gap. The THC reads arc voltage as a proxy for torch-to-material distance and makes real-time corrections — raising the torch over warped areas and lowering it over dips. A quality THC is one of the most important components for achieving consistent cut quality across an entire sheet.
The handheld or machine-mounted assembly that generates and directs the plasma arc. A CNC plasma torch (also called a machine torch) is designed for automated use with a straight barrel, machine-mount threads, and a pilot-arc start. Machine torches are rated for higher duty cycles and longer consumable life than handheld torches. Major brands include Hypertherm Duramax, Thermal Dynamics SL, and Miller ICE series.
The main plasma cutting arc that transfers from the electrode inside the torch to the workpiece. This is the working arc that performs the actual cutting, as opposed to the pilot arc (which stays within the torch body). The transfer arc forms when the ionized pilot arc stream contacts the conductive workpiece and the full cutting current flows.
A plasma arc configuration where the electrical circuit flows from the electrode through the plasma stream to the workpiece. All plasma cutting uses a transferred arc — the workpiece is part of the electrical circuit. This is in contrast to a non-transferred arc (used in plasma spraying), where the arc stays between the electrode and nozzle inside the torch.
A CNC plasma cutting table with a water-filled pan beneath the slat bed. The workpiece sits just above or partially submerged in the water, which captures smoke, dust, and UV radiation from the plasma arc. Water tables are quieter, reduce heat warping on thin material, and eliminate the need for ductwork. They require water treatment and anti-spatter additives to prevent rust and bacterial growth.
Another name for the ground clamp — the spring-loaded or screw-type clamp that connects the plasma power supply's work cable to the material or cutting table to complete the electrical circuit. A clean, tight work clamp connection is essential for reliable arc starts and consistent cut quality.
Dive deeper with our buying guides and interactive tools.
Everything you need to know before buying a CNC plasma table.
What a torch height controller does and why you need one.
Find the right amperage, cut speed, and gas type for your material.
Compare CNC control and CAM software for plasma cutting.
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