There are a variety of approaches to precision metal cutting. The type of methods range from basic welding, to plasma cutting, laser cutting, and waterjet cutting. Additionally, within each technique exists further subsets. For instance, within the technique of plasma cutting, the plasma gouging method and CNC methods are available. Within the waterjet approach, CNC methods are also available, in addition to what is called pure waterjets, and abrasive waterjets.
Currently, the most common methods used in the precision metal cutting industry are CNC plasma cutting, and CNC waterjet cutting.
The term CNC stands for computer numerical control, indicating that the task of cutting by the device, is performed by a computer.
There are many pros and cons to both CNC plasma cutting and CNC waterjet cutting. In order to decide between the two types, one must consider the following:
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The type of material that will be cut
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The thickness of the material that will be cut
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The level of accuracy required for the type of cut
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Production time granted
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Costs available for operation
CNC Plasma Cutting
The method of CNC plasma cutting is limited by the variety of material it can cut, however, it is ideal for cutting specifically metal materials. This includes:
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Mild steel
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Aluminum
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Stainless Steel
CNC plasma cutters are known to perform best with materials less than an inch thick, and are extremely fast. The speed range is of 0.1 to 1,000 inches per minute, depending on the density of the substance.
In the plasma cutting approach, a flow of plasma is used via a plasma arc or electrical arc. The plasma is so hot in temperature that it can cut through many different types of metals. Furthermore, the use of a plasma torch tool makes this method very accurate.
CNC Plasma cutting has many advantages. However, as with anything else, it also has its disadvantages. The pros and cons include:
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Most appropriate cutting method for metal materials
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While accurate, other methods have proven more meticulous
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More efficient in processing metal than abrasive waterjets
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Lesser expensive cutting devices
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Contains consumable parts that require replacing
CNC Waterjet Cutting
CNC waterjet cutters are better for situations in which detailed cutting are needed, especially where fully extended cuts are necessary (cutting entirely through the material). Waterjet cutters are more efficient in regard to production, and are versatile in that these machines can cut through both soft and hard materials like rubber and titanium. However, it is not able to cut through all grades of steel.
CNC waterjet cutting machines use a jet of water to cut materials. The water is moving at more than 2,000 feet per second, and under pressures of about 90,000 pounds per square inch (psi). This approach essentially errodes the material.
Pure waterjet machines use only water to cut materials. Therefore, it is more appropriate for softer materials like:
Abrasive waterjet cutters use a mixture of water and an abrasive substance to cut materials. Therefore, it is more appropriate for harder materials like:
The advantages and disadvantages of employing CNC waterjet devices include:
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Ability to cut both soft and hard materials
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No heat affect zone (HAZ) and therefore, material structure is not compromised
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Considered a "green” technology as the water is recyclable and emits limited fuel
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Not the ideal method for metal cutting when speed of processing is a factor
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Abrasive substances in abrasive waterjets are costly
CNC approaches to metal cutting are considered to be far more precise than other forms, whether it be a plasma device or waterjet. The technique is capable of producing complex cuts, and are less likely to produce errors. Moreover, because of its high accuracy, CNC approaches rarely require secondary operations, making this technique much more efficient.