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Esprit Automation - Thermal cutting terms
Category: Agriculture and Industry > Thermal cutting
Date & country: 24/11/2007, UK
Words: 32

Arc Lag
This is the angle at which the arc lags the torch relative to the vertical direction. It increases with speed or power. A surface mark of about 5 degrees is the optimum setting.

Arc-voltage Height Sensing
(or Arc voltage control, AVC). When the main plasma arc has been established the voltage between the torch and material is measured. This is used to compare with an operator set reference voltage and the system ensures that the correct torch stand-off is maintained during the entire cut. The arc-voltage is directly proportional to arc-length.

An ArcWriter is a dual gas, variable output power, plasma marking, scoring and punching system designed to leave temporary or permanent identification marks on metal surfaces. This is very often a separate power supply and plasma torch to the main cutting plasma torch. However, increasingly these are becoming integrated within the main plasma torch, especially where Hydefinition cutting is involved, allowing the customer to cut or mark with the same cutting torch.

Back Lash
This is the amount of movement the machine can make with out moving the motor. Provision is made on all Esprit machines to reduce this to a minimum by the use of very low or virtually zero backlash gearboxes.

Bevel-Kerf Angle
This is the angle the cut face is out of square to the top surface of the material being cut. When plasma cutting this angle is dependent on matching the speed, power (amps) and the distance between the torch and the material being cut.

Common Cutting
This is where a previously cut path is used as part of the cut for another profile.

Conventional Plasma Cutting
This process generally uses a single gas (usually air or nitrogen) that both cools and produces the plasma. Most of these systems are rated at under 100 amps, for cutting materials 5/8� thick.

DNC Link
This is the optically isolated connection between the CAD/CAM system and the CNC control mounted on the profiling machine. It is a modulated signal and can be transmitted over a few kilometres.

This is a build-up of waste material, removed during the cutting process, which sticks to the underside of the profile. This is preventable by correctly setting the cutting process variables.

Dual Gas plasma Cutting
This utilizes two gases; one for the plasma and one as a shield gas. The shield gas us used to shield the cut area from atmosphere, producing a cleaner cut edge. This is probably the most popular variation, as many different gas combinations can be used to produce the best possible cut quality on a given material.

Duty Cycle
This refers to the percentage of time in any ten minutes that the plasma arc can be cutting. It is usually 100% on mechanised plasma cutting systems.

The electrode is used to start the plasma cutting arc. A high frequency low-amperage current is passed between the electrode and the nozzle, which is seen as the pilot arc. The electrode has a slug of highly conductive (and expensive) rare metal (typically Hafnium or Zirconium) inserted into its end. Each time the pilot arc is struck, a small amount of this rare metal is evaporated. Eventually all or most of this material is evaporated and the pilot arc will not strike. At this point (or earlier if the pilot-arc does not strike consistently) the electrode must be changed.

High-Low Gas System
(or High Preheat system) This system is used during pre-heating of the plate prior to piercing when using the Oxy-fuel cutting process. Higher than normal fuel gas and heating oxygen pressures are used to achieve a much hotter, fiercer flame resulting in much shorter pre-heat times. Pre-heating without high-pressure pre-heating can sometimes take a few minutes with material in excess of around 50mm.

Hydefinition Plasma
This is a Hypertherm patented technology that super-constricts the plasma jet to yield an energy density two to three times that of conventional plasma. This gives a much narrower kerf, producing straight dross free edges, essentially eliminating secondary finishing operations.

HyFlow Vortex Technology
This is a vented two-piece nozzle patented by Hypertherm to stabilise the plasma arc precisely in the centre of the electrode in Hydefinition applications. This consistency increases electrode and nozzle process life.

Initial Height Sensing (IHS)
This is the process of positioning the plasma-cutting torch at the correct distance above the plate prior to striking the arc. Inductive sensors are most often used to sense the plate as these can be used above or below water. Once the initial torch height has been set and the arc started, arc-voltage height control is used to maintain the correct torch to material stand-off during cutting.

Kerf - Kerf Width
This is the width of the slot created by the cutting process.

Kerf Compensation
This is an operator adjustable dimension, which can be altered at any time. It is the amount of cutting path offset required to compensate for the material removed by the cutting process. The normal compensation is half of the kerf width.

LongLife Oxygen Technology
This involves the precise control of key cutting parameters to gradually ramp up the power to the plasma torch when starting the cut, and gradually ramp down the power when stopping. These are the times when consumable deterioration is most prevalent, as parts of the electrode material (hafnium) in the plasma torch break away and ejects from the face of the electrode if the power is immediately turned on to full power or switched straight off. Therefore creating extra wear on the consumables. However with the gradual change in power created in the LongLife process consumable life is significantly extended.

The nozzle has two purposes. The pilot arc is struck between the electrode and the nozzle, the nozzle being connected to the other side of the High-frequency generator. Once the pilot arc has struck and when the main-arc is produced, the small orifice in the end of the nozzle constricts the arc. During its life, under normal the orifice in the end of the nozzle increases in diameter. If any of the molten metal produced during piercing is deflected back on the nozzle then the nozzle orifice may become misshapen. As the shape and size of the nozzle orifice changes, the cut quality will deteriorate. Typically the nozzle is replaced at the same time as the electrode or perhaps every two electrodes.

Over-Under Water Cutting Table
This type of cutting table has an air chamber, which when filled with air causes the height of the water level to rise. Thus the level of water can be set to be either below, level with or above the material. Cutting tables of this type are used for underwater plasma cutting and for cutting on water. The water level is lowered when the parts are to be removed from the table allowing the operator to walk on the table.

One common description of plasma is to describe it as the fourth state of matter. We normally think of the three states of matter as solid, liquid and gas. For a common element, water, these states are ice, water and steam. The difference between these states relates to their energy levels. When we add energy in the form of heat to ice, the ice melts and forms water. When we add more energy, the water vaporizes into hydrogen and oxygen, in the form of steam. By adding more energy to steam these gases become ionised. This ionisation process causes the gas to become electrically conductive. This electrically conductive, ionised gas is called plasma. The plasma cutting process, as used in the cutting of electrically conductive metals, utilises this electrically conductive gas to transfer energy from an electrical power source through a plasma cutting torch to the material being cut. It is then how the plasma gas is controlled through the torch, which effects the final cut quality you see.

Plate Rider
A plate rider is a pneumatically controlled dish with a number of roller balls mounted in the base. The dish is retracted whilst the machine is traversing but when cutting the dish is lowered so the balls are in contact with the material. The torch is positioned a precise height above the bottom of the balls and an exact torch stand-off is maintained in this manner. The plate-rider is a very simple device but produces excellent results on materials up to about 6mm. Because of the contact between the balls and the material, the plate rider is not always suitable for particularly highly finished materials.

Quick Disconnect Torch
A quick disconnect torch is a system which allows for rapid consumable changes. This is accomplished by unscrewing a single band and pulling the torch head off and then replacing it with a second spare torch head. By having a spare torch head, the consumables from one torch head can be changed off line, while the system is cutting with the other one. Therefore minimising downtime. All Hypertherms Hydefinition torches have quick disconnect torches, in comparison a number of the competition only offer a single unit construction torch. Where by the consumables have to be pulled out one by one thereby reducing productivity.

Remote voltage-current selector.
On Max200 plasma systems and above, the remote voltage and current selector allows the machine operator to vary the cutting current and arc-voltage reference from the machine console. The remote voltage/current selector is a box with LED displays and knobs to set the parameters, which is mounted on the profiling machine.

The shield is a copper item that is screwed on to the front of the torch when all the other components have been put in. It is designed to protect the nozzle from splatter produced when piercing. The shield locates on the shield cap. Replacement of the shield is only required when the piece appears damaged by molten metal adhering to or melting it.

Shield Cap
The shield cap is a robust screw-on item, which covers the sides of the nozzle and torch. The shield screws on to the shield cap to protect the end of the nozzle. The shield cap needs replacing very infrequently only when it becomes badly charred. For each plasma cutting system there is a range of consumable parts covering different cutting current ranges, different plasma gases and different cut-quality criteria.

Standard Shapes
These are a library of standard shapes programmed into all Paragon CNC units. Various standard forms such as rectangle, circle, ring, flange, gusset etc are available. The operator can specify all of the dimensions, lay out an array of profiles and set a gap between multiple profiles.

Swirl Ring
The swirl ring is a ceramic ring with various small holes designed to swirl the plasma gases thus accelerating them and further constricting the arc. This item lasts much longer than the electrode or nozzle. Eventually the swirl ring becomes brittle and may break when changing other consumable parts in the torch.

Update Time
This is the number of times per second that the CNC updates the servo`s and consequently modifies the correct position of the machine. The new Paragon Esprit control has an update time of 1 millisecond compared to 5ms on a Farley and 25/30ms on some current machines. You can imagine the problems some of our competitors have when they only update every 2mm at 3m/min cutting speed.

Water Injection Plasma Cutting
This process uses a single gas for plasma and utilizes water either radially or swirl injected into the arc to greatly improve arc constriction, therefore arc density and temperatures increase. This process is used from 260 to 760 amps for high quality cutting of many materials and thicknesses.

Water Shield Plasma cutting
This is a variation of the dual gas process where water is substituted for the shield gas. It produces improved nozzle and work piece cooling along with better cut quality on stainless steel.