Файл: Two primary machining processes are turning and milling.docx

During the manufacturing of a part, a variety of machining operations and processes are needed to remove excess material. These operations are usually mechanical and involve cutting tools, abrasive wheels, and discs, etc. Two primary machining processes are turning and milling. 

Turning is a machining process performed by a lathe; the lathe spins the workpiece as the cutting tools move across it. The cutting tools work along two axes of motion to create cuts with precise depth and width. Lathes are available in two different types, the traditional, manual type, and the automated, computer numerical controlled (CNC) type.

Milling uses rotating cutters to remove material, unlike turning operations where the tool does not spin. Traditional milling machines feature moveable tables on which the workpieces are mounted. On these machines, the cutting tools are stationary and the table moves the material so that the desired cuts can be made.

Other processes sometimes dovetail onto these processes or are performed with standalone equipment. for example- Drilling/Boring/Reaming

1)what machining operations exist?

1) Drilling/Boring/Reaming, Milling, Turning

2) what tools are used in these processes?

2) cutting tools, abrasive wheels,discs

3) what types of lathes exist?

3) manual type and the automated

Во время изготовления детали для удаления излишков материала необходимы различные операции механической обработки и технологические процессы. Эти операции обычно являются механическими и включают в себя режущие инструменты, абразивные круги и диски и т.д. Двумя основными процессами обработки являются токарная обработка и фрезерование.

Токарная обработка - это процесс механической обработки, выполняемый токарным станком; токарный станок вращает заготовку по мере перемещения по ней режущих инструментов. Режущие инструменты работают по двум осям движения, создавая надрезы точной глубины и ширины. Токарные станки выпускаются двух различных типов: традиционные, ручные и автоматизированные, с числовым программным управлением (ЧПУ).

При фрезеровании для удаления материала используются вращающиеся фрезы, в отличие от токарных операций, при которых инструмент не вращается. Традиционные фрезерные станки оснащены подвижными столами, на которых монтируются заготовки. На этих станках режущие инструменты неподвижны, а стол перемещает материал таким образом, чтобы можно было производить желаемые надрезы.

Другие процессы иногда дополняют эти процессы или выполняются с помощью автономного оборудования. например - Сверление/расточка/развертка

CNC milling machine

Milling is not a new process. Since the arrival 

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Industrial Revolution in the XNUMXth century, began a journey in which man and machine would go hand in hand to manufacture. However, little by little the machine has been occupying more positions and functions that previously only man could do. Milling machines have been around for decades, but CNC milling is something more contemporary. A way to control everything by computer, improve the speed, precision and productivity of this type of machining.

Milling is a process by which a tool known as a milling cutter creates shapes or pieces. It is done by subtractive manufacturing, that is, the opposite of additive manufacturing. The milling cutter will start or eliminate part of the material until carving or carving what was wanted. With the advent of the CNC, computers can control the CNC milling machine to achieve the expected result, without a person having to make adjustments and movements manually.

To better understand the operation of a CNC milling machine and the milling process, it would also be important to at least list and understand some of the the main parts. Not all milling machines have them, as it can differ from one manufacturer to another, or between models. However, the main ones are:

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  Spindle: It is the one that keeps the cutting tool in place for the processing of the part.
  
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  Tools: it is a removable component, and it is the one that performs the carving on the piece.
  
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  Control panel: is the interface through which the operator can control the machine or monitor some parameters.
  
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  Actions column: It is the main part or frame that holds other components of the machine in place.
  
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  Seat: it is fixed to the column of the machine, and rests on the work table.
  
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  Kitchen: it is the base of the machine in which the upper part of the seat is located, where the piece to be machined is placed. It will also have a clamping device so that the piece does not move during the process.
  
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  Base: is the support area of ​​the machine on the ground.
  
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  Refrigeration system: It can be by air or by liquid. Since there is friction between the workpiece and the tool during milling, a lot of heat will be produced in some cases. To reduce the temperature, you can use air or fluids that bathe the work area.
  

How CNC milling machine works

Like any other CNC milling machine, everything starts with a computer design that will be passed to an understandable language by the CNC machine and it will read this code to control movements what should I do to get the result identical to the model designed by computer. The drill will remove material from some areas until it achieves the appropriate shape, thickness

Common Milling Operations

There are various operations of milling that can be carried out with this type of CNC machines. Depending on the type of court, the main ones are:

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  face milling: the axis of rotation of the tool will be perpendicular to the surface of the work piece. This milling will create flat surfaces and requires end milling cutters with sharp edges.
  
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  Plano: when the axis of rotation is parallel to the surface of the part. The tool has cutting edges along the entire cutting circumference, and produces slots, cavities, grooves.
  
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  Angular: the axes of rotation of the tool make an angle with the surface of the part. It is used to produce chamfers, slots, dovetails, etc.
  
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  shape milling: they are specific milling cutters to generate irregular surfaces, semicircular contours, cords, curves, etc.
  
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  Others: there are also some others to create gears, simultaneous work on several surfaces, etc.
  

Types of CNC milling machines

Several types of CNC milling machines. And as was the case with lathes and other types of machines, they can be classified using several criteria:

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According to spindle orientation

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  Vertical: more versatile in terms of machining options.
  
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  Horizontal: better to work with heavy and long pieces.
  

Depending on the number of axles

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  3 axes: they are parts with X axis (left to right), Y axis (forward and backward) and Z axis (up and down), allowing 3D milling. These machines are the simplest, easiest to operate, and are the cheapest. However, you cannot access certain areas of the part being machined, and the geometry that can be achieved will be less complex.
  
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  5 axes: This machine is more complex than the previous one, adding two additional axes to improve freedom of movement. With this, more complex parts are obtained. In this case, the part will be able to make rotary movements so that the tool can have better access to all areas. Among its advantages are the fact of eliminating the manual repositioning of the part, ability to produce more complex geometries, better precision, and very smooth surfaces. As for the disadvantages, there is the cost, and the greater complexity of the machine.
  

According to the materials

There are many materials that can be machined or milled. However, there are some restrictions, as the materials need to have specific tensile strength, heat resistance, hardness, and shear strength properties.

Advantages of Numerical Control Milling

CNC milling has big benefits for a workshop or company. For example, some of the most prominent benefits are:

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  Productivity: increases production speed, and reduces costs.
  
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  Scalability: allows to manufacture from a few pieces to increase large-scale production, to mass manufacture and allowing all the pieces to be identical.
  
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  Precision- Some machines are accurate to as little as tenths of a millimeter, so they will be able to create high-quality parts.
  
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  Versatility: they can create all kinds of shapes (chamfers, cavities, slots, threads, teeth,…), and you can even quickly change the job to produce a different part in no time.
  

Among the industries that use this type of machines are aerospace, electrical, automotive, robotics, construction, medical, food, to make furniture, etc.

Disadvantages

CNC milling also has Some disadvantages:

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  Cost of complex geometries: depending on the geometries, the cost could increase and the time required as well.
  
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  Restrictions or limitations: these machines can only work with specific part dimensions in terms of length and width.
  
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  Shapes that cannot be milled: They cannot create certain features, such as curved holes, straight internal edges, walls less than 0.5mm, etc. For this, other types of machines would be needed.
  
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  material waste: In subtractive manufacturing processes, a large amount of material is eliminated, generating a lot of waste. Only a portion of the entire virgin block will be used. Many of the resulting chips can be recycled or reused. For example, metal can be melted down, some plastics are also recycled, or wood can be used for other industries (paper, fillers, biomass, etc.).
  

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