How does an EDM machine work?

 Electrical Discharge Machining (EDM), also known as electrical discharge machining or spark machining, is a non-contact machining process that uses electrical spark erosion to remove conductive material from the workpiece.

1. Basic working principles of EDM

The operation of an EDM machine relies on the rapid and repeated release of a high-voltage electric current between the electrode and the workpiece. The key components and steps are as follows:

1.1 Key components

1. Electrode: Acts as a cutting tool and can be a copper rod, graphite, or brass wire (in the case of Wire EDM). The electrode is connected to one terminal of the power supply.

2. Workpiece: The material to be cut, which must be an electrically conductive material . The workpiece is connected to the other terminal of the power supply.

3. Dielectric Fluid: The workpiece and electrode are immersed in this fluid (usually EDM oil or distilled water). This fluid acts:

   • Insulated: Prevents short circuits.

   • Controls spark generation: It breaks down into a conductive medium when the voltage is high enough.

   • Cooling: Absorbs heat from sparks.

   • Scrap Removal: Flush molten metal particles out of the cutting gap.

1.2 Spark Erosion Process

1. Spark Gap Control: The servo system controls the electrodes to move as close to the workpiece as possible (but not touching it) to create a micro-gap between them.

2. Dielectric Breakdown: As the voltage applied between the electrode and the workpiece increases, the electric field in the gap increases, causing the dielectric fluid to ionize.

3. Electrical Discharge: A rapid flow of electric current in the form of a spark across a gap.

4. Melting and Evaporation: This spark creates very high heat (up to8,000to12,000  ºCOr more20,000 °F) which will cause the small pieces of material in the area where the spark occurs on the workpiece to melt and evaporate, turning into vapor.

5. Flushing: When the spark is extinguished, the circulating dielectric fluid rapidly flushes molten metal particles (slag or Debris) out of the gap.

6. Repetition: This entire process is repeated rapidly (thousands of times per second) as the CNC system controls the movement of the electrode, continuously and precisely "eroding" the material into the desired shape.

2. Main types of EDM machines

The specific operation varies depending on the type of EDM machine:

EDM machine type	Electrode	Working characteristics	General use
Sinker EDM (Ram/Die Sinking EDM)	Electrodes that are fabricated to a specific shape (e.g., graphite or copper rods)	The electrode is "sunk" into the workpiece to create a cavity, channel, or negative 3D shape.	Plastic injection molding, casting molding, complex cavity creation
Wire EDM (Wire-Cut EDM)	Thin wire (usually brass) that is fed continuously.	The wire acts like an electric band saw, cutting through the workpiece, creating straight cuts or cutting complex 2D shapes.	Metal stamping die work, high-precision parts, thin-walled shape cutting
Hole Drilling EDM (Fast Hole Drilling)	Hollow Tube Electrode	Used to create small, deep, and precise holes quickly.	Drilling the initial hole for Wire EDM, creating cooling holes in the turbine

Advantages of EDM

• Can cut very hard materials (such as hardened steel) that are difficult to cut with conventional methods.

• It is a cutting process that does not use mechanical force (No Mechanical Force), allowing delicate parts to be cut without distortion or deformation.

• Provides high precision and good quality surface finish.

• It can create complex geometric shapes, small holes and sharp internal corners that cannot be achieved with conventional milling.

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How does a CNC waterjet machine work?

 A CNC waterjet cutter is an automated cutting tool that uses the principle of mechanical erosion, injecting a high-pressure stream of water (often mixed with an abrasive) to cut precisely through almost any material. It is a cold cutting process.

1. Basic operating principles

The operation of a waterjet machine relies on converting water pressure into very high speeds for cutting, which is divided into three main steps as follows:

1.1 Ultra High-Pressure Generation

• High-Pressure Pump (or Intensifier Pump): This is the heart of the system. It takes filtered tap water and intensifies it to a very high pressure, typically around60,000to94,000PSI (pounds per square inch) or approximately4,000to6,480bar

1.2 Pressure to Velocity Conversion

• Orifice: High-pressure water is directed through a metal tube to the cutting head. As the water is forced through a tiny hole called an "orifice" (usually made of diamond or sapphire), which is much smaller than a human hair, the laws of physics convert the water pressure into a jet of water that travels at supersonic speeds (higher than sonic ).2,500miles per hour, or about 3-4 times the speed of sound)

1.3 Cutting Mechanism

Waterjet cutting is divided into two types depending on the material:

• Pure Waterjet Cutting: Used for cutting soft materials such as rubber, foam, plastic, wood or food. The high-speed water jet cuts the material by the force generated when it hits the surface.

• Abrasive Waterjet Cutting: Used for cutting hard materials such as metal (steel, stainless steel, aluminum), stone, glass, or ceramics.

  • In the mixing chamber of the cutting head, abrasives such as garnet, a natural sand, are sucked into the pure water stream through the principle of vacuum (Venturi effect).

  • The abrasive-mixed water stream is accelerated and projected out of the focusing tube as high-speed "liquid sandpaper" that erode, or grinds, away material in small, microscopic amounts.

2. The role of the CNC system

CNC (Computer Numerical Control) systems are crucial in controlling the entire process to produce precise and complex workpieces:

1. Programming: The user enters 2D or 3D drawings created from a CAD program into the CNC system.

2. Motion Control: The CNC software converts the design into G-code to control the movement of the cutting head in the X and Y axes (and the Z axis or other rotational axes for 3-5 axis machines) to cut along the desired line.

3. Parameter Management: The CNC system controls water valve opening/closing, pressure adjustment, and abrasive feed rate to suit the material type and thickness, which affects cutting speed and edge quality.

Main advantages of Waterjet CNC

• No Heat Generation: Since it is a cold cutting process, there is no material distortion (Thermal Distortion) or heat affected zone (HAZ) generation.

• Material versatility: Can cut almost any material, from soft to very hard.

• High precision: It can cut complex shapes with high precision and has a very narrow Kerf, reducing material waste.

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How does a CNC plasma cutting machine work?

 A CNC plasma cutter is an automated tool that uses the principle of heat cutting, relying on the fourth state of matter called plasma , to cut all types of conductive metals (such as steel, stainless steel, aluminum) quickly and precisely under the control of a computer system.

1. Principles of plasma generation and cutting

The main process of plasma cutting consists of four important steps:

1.1 Gas Flow

• The machine injects gas (such as compressed air, nitrogen, oxygen, or an argon/hydrogen mixture) into the plasma torch at high pressure and speed.

1.2 Electric Arc and Plasma Creation

• Inside the cutting head are electrodes and nozzles.

• When a high voltage current is applied between the electrode and the injector, a spark is created, which ionizes the gas flowing through that area.

• The ionized gas becomes a plasma, a very high temperature conductor (up totoor more)

1.3 Cutting Action

• Once plasma is generated, the system transfers the primary current to the metal workpiece (the workpiece acts as the positive terminal in the circuit).

• A highly heated plasma jet is forced out at very high speed through a tiny orifice in the nozzle.

• The intense heat of the plasma causes the metal in contact to melt instantly .

• The pressure and high velocity of the still flowing gas blows away the molten metal from the Kerf, causing the workpiece to continuously break apart.

1.4 CNC control system

• The CNC (Computer Numerical Control) system precisely controls the movement of the plasma cutting head along the X, Y, and Z axes according to the shape the user has designed in the computer program.

• CNC controls parameters such as cutting speed, amperage, and torch height control (THC) to achieve the best possible cut quality.

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2. Working steps of CNC plasma cutting machine

1. Design: The user creates the shape of the workpiece in a CAD (Computer-Aided Design) program.

2. G-code Generation: Use Computer-Aided Manufacturing (CAM) software to convert design files into G-code instructions to tell the machine where to move and when to start cutting.

3. Setup:

   • Place the metal sheet on the cutting table and connect the ground wire to the workpiece.

   • Set cutting parameters (current, gas type, pressure) in the CNC system.

4. Arc Initiation:

   • The CNC system will command the cutting head to lower to the pierce height.

   • The machine will start the plasma creation process (Pilot Arc) and send the current to the workpiece.

5. Piercing:

   • The high-heat plasma beam penetrates through the thickness of the metal sheet.

6. Cutting:

   • Once the cut is made, the CNC system commands the cutting head to start moving along the path specified in the G-code.

   • The Automatic Cutter Head Height Control (THC) system works to maintain a constant height between the cutter head and the workpiece to produce a consistent quality cut.

7. Completion: When the workpiece has been cut to the specified shape, the system will stop supplying power and stop the gas flow.

Summary of main components

component	duty
CNC system	The brain controls the movement in the X, Y and Z axes to cut according to the designed shape.
Power supply	Converts alternating current (AC) to direct current (DC) and provides the high current required to create the plasma arc.
Plasma cutting torch	It is the origin of plasma, consisting of electrodes, nozzles and rotating gas rings.
Gas (Gas/Compressed Air)	It is a medium for creating plasma and uses high pressure to blow away the molten metal.
Altitude Control (THC) System	Automatically adjusts the distance between the cutting head and the workpiece to maintain the quality of the cut.

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