One of the metalworking techniques is cutting. Metal cutting is a process in which, a cutting tool penetrating the material causes the separation of the particles of that same material.
There are two basic ways of metal cutting:
- Rough processing – is a basic treatment and consists of scraping, drilling, milling, etc. The main object of this kind of processing is to remove a larger quantity of material
- Final processing – broaching, grinding. This procedure is used to perform the final processing, after the cutting is being done
If metal cutting tools could be divided in groups, they would be divided into:
- Hand metal cutting tools– eg. Hand saws, scissors
- Machine metal cutting tools– laser cutter, plasma cutter, water jet cutting, autogenous cutting, etc.
The decision of how to cut the material depends on the speed, the quality, the precision and general requirements of the cutting. Accordingly, cutting tools are chosen as well.
An example of cutting a material with a hand tool is sheet cutting. When it comes to sheet cutting; scissors (hand or desk) are used in most cases, and there is minimal snout present during the cutting. However, the cutting should be further processed due to the sharp edges that occur in the cutting process.
Machine metal cutting is mostly done by the CNC technology, which has many benefits. Therefore, for example, CNC laser metal cutting, provides a precision of 0.2 mm. Iron cutting is possible as well, by using a CNC and one of the cutters (eg. plasma cutter).
Metal cutting principle
When cutting, the material being cut (sheet metal, iron, steel …) is subject to plastic deformation, the stress of the cut material is increased, it begins to leak, which eventually causes cracking or deformation. When cutting, snout occurs as well. Moreover, the cut alone in some cutting techniques requires additional processing while in other (eg laser cutting) it doesn’t.
In addition to the before mentioned division into hand and machine cutting tools, cutting tools can be divided into:
- Tools separating the material by cutting (eg. knife)
- Tools separating the material by particle separation (eg. drill bit)
- Cutting tools without direct contact – energy cutting (eg. plasma cutter)
As has already been mentioned, snout occurs when cutting the material. In some techniques the amount of snout is negligible, while in some it is pretty large.
The amount and the way of forming of the snout depends on the plastic properties of the cut material and can be divided into:
When cutting, forces that affect the heat of the material occur, and the material can be deformed if the amount of heat transferred to it is large. However, today’s sophisticated cutting techniques mostly transmit a minimal amount of heat to the material, so deformation is avoided. In addition, most sophisticated cutting techniques (plasma, laser cutting) leave very little cuts behind, and the cut itself doesn’t need to be further processed.
The development of technology, especially the CNC, increases the precision of cutting. For example, CNC laser metal cutting achieves a precision of 0.2 mm.
Materials used for cutting tool production
When cutting material, apart from the deformation of the material, the depletion of the cutting tool happens as well.
Therefore, the following requirements are posed on the cutting tool:
- Cold cutting tools – up to 200 ° C: depletion, deformation, hitting resistance
- Hot cutting tools – above 200 ° C: depletion, corrosion, hitting resistance
With each cutting tool the following differs:
- Causes that affect wear – heat can increase depletion
- Depletion mechanisms – eg oxidation
- The way it is being used – eg fracture
- Depletion Criteria – Different cutting materials have different criteria when it comes to depletion
Metal cutting is one of the most important processes before any further processing. The development of the CNC technology enabled a high precision of the cut, that is as high as 0.2 mm.