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Radmot Mar 22, 2023 8:49:51 AM

Metal machining – what is this process?

Metal machining is a process of shaping elements made of alloys, modification of their dimensions, and sometimes: also properties. The goal of such a process is a production of an element that has the desired size and shape. 

There are many types of machining – the main difference between them is based on the type of processed material (eg. during milling it is usually a block of metal alloy) and technology characteristics (eg. milling removes material way more effectively than plastic machining). And of course: the type of tool used to machine and cut metal. What are the types of metal milling and what possibilities do they present?


Types of metal machining

There are widely accepted typologies of metal machining operations that divide it into main categories:

  • machining (eg. milling, sanding, water jet cutting, turning – traditional and computer numerical control based), 
  • plastic processing (eg. curving, stamping, drawing, forging),
  • thermal processing (eg. annealing or saturation with elements).

Each of these processes allows the production of a metal part, with different properties and shapes:

  • Metal machining is the mechanical processing of metal elements that focuses on removing the extent of the material. Part produced in the said process is usually much lighter than the block of beginning material and has a desired shape and is made according to the requirements of the customer.
  • Plastic metal processing allows to shape of parts (eg. stamping, curving) but without changing the initial volume of the object (mass before and after plastic processing remains the same or almost the same).
  • Thermal, chemical, or thermo-chemical metal processing is focused on giving an object additional and predefined features. It can be annealing, which gives a processed metal part better hardness and rigidity, or anodization, which improves surface finish (typically: aluminum). 

Each of these metal machining processes has a different usage and can be utilized during the whole manufacturing process (eg. machined parts are subjected to the process of annealing).


Machining of metals - what is that process?

The overall characteristics of metal machining can be described well by its alternative name: removal treatment. The whole process focuses on removing extended material till the part gains its desired shape and form. Currently, we can point to three main types of metal machining: 

  • milling, (on an automatic or CNC machine),
  • turning, (same: automatic or CNC operated),
  • grinding (same: automatic or CNC). 

Machining metal parts shape blocks of raw material by removing material – for example, milling machines use cutters to cut material. Due to the vast variety of tools, contemporary milling machines can remove big amounts of material on short notice). 

On the other hand, we can divide the milling itself into circumferential and face milling (due to the orientation of the cutting surface in the process) and opposite and concurrent milling (due to the orientation of the machined object). 

It is worth mentioning, that milling (especially made by computer numerical control) allows the production of elements of almost any shape and form. 

Turning, as one of the milling processes, works on the principle of removing excess material from the rotating object (attached to the leaf's holder) by a specialized turning blade (tool bit or drill). 

Such metal machining can be divided due to the orientation of the blade (in other words: the side of the machined object) for external turning (most current – blade moves on a special fence) or internal (sometimes called "boring” – the blade moves inside the turned object). 

Grinding is usually seen as one of the final steps for the part machining – it can smoothen the surface, but also removes smaller amounts of the material. 

It is worth mentioning – processes, that we see as "metal machining” can be performed by hand-controlled tools (eg. automatic leaf) or controlled by the computer (then called "CNC machining”). 

CNC machining is a very popular way of shaping and machining metal elements – due to high precision, low tolerance, and ease of mass production. 

In addition – a well-prepared surface can speed up the whole manufacturing process. For example, additional chemicals, thermal (such as aluminum anodizing), or other processes are easier to perform on well-machined parts.

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Plastic processing of metals – how does it differ from other techniques?

Plastic processing of metals explores the natural flexibility of metal alloys to shape them in a wanted way. We can divide such for: 

  • bending,
  • stamping, 
  • forging, 
  • draw. 

Metal bending (eg. pipes of metal profiles) is commonly used as a process for shaping parts for pipe construction (like scaffolding). The great advantage of that process, especially cold bending, is simplicity and ease – it is not required to use any types of additional tools, just sheer force. 

On the other hand, forging metal, in addition to shaping, changes the internal structure of the object and gives additional (often: wanted) features such as higher rigidity or mechanical resistance. 

Metal stamping is commonly used to produce thin metal elements, such as sheet metal. Stamping is performed with the help of hydraulic or mechanical presses that provide high pressure for each square centimeter. 

Plastic processing of metal can be performed:

  • in cold (in a temperature below the point of metal recrystallization even at room temperature), 
  • in hot (above the point of metal recrystallization – heat increases the plasticity of the metal).

Force directed to the object allows it to change its shape and the process temperature has an impact on the final features of the shaped part. 

It is commonly agreed that metal machined plastically in hot is less fragile than one shaped in cold. On the other hand, – cold shaping can provide better hardness and overall rigidity of the object

Thermal processing of metal

Thermal processing (often called "heat treatment") is focused mainly on giving features and properties – mainly as a result of changing alloy structure. Among the thermal processing of metal, it is worth mentioning:

  • hardening, 
  • annealing, 
  • supersaturation, 
  • stabilization. 

Hardening is a commonly recognized form of thermal processing of metal. It betters the physical characteristics of the element as a result of the fast cooling of heated-up elements, eg. by converting it to cold water or oil.  

Annealing has some similarities to hardening, yet the main difference is the cooling process – the heated part is left to cool down at its natural speed. 

Stabilization is a form of annealing, yet the element is heated up to 100-150 °C.


Chemical and thermo-chemical processing of metal

A thermo-chemical and chemical treatment of metal is a group of processes focused on giving the object desired set of characteristics by the influence of chemical substances and/or high temperature. 

Chemical treatment of metal is used to change the physical and chemical characteristics of a steel surface. It can be for example nickel plating, the process that creates a coat of nickel on the surface of a part. 

On the other hand – term-chemical treatment is a much more complicated process, that allows getting a more wear-resistance surface of the element with different properties. It is a result of combining thermal processing, used as an accelerator for the chemical processes. 

We can mention about following types of thermo-chemical treatment of metal: 

  • chrome plating, that improves the esthetics of the part and creates a wear-resistant coat on the surface of the metal (the process is performed in temperatures up to 1050 °C), 
  • nitriding, that improves corrosion- and wear resistance of the surface, 
  • silication, the process of enrichment of the surface of the metal by silica in high temperature improves temperature and acid resistance of part,
  • sulfation, a saturation of the surface with sulfur, that improves sliding properties and significantly reduces friction.


Metal machining - contact us

At RADMOT, we can offer CNC milling servicesCNC turning services as well as many additional services, including washing, aluminum anodizing, laser marking and assembly.

Contact us and tell us what you need. We have been providing CNC services for almost 40 years. Our quote is completely free. And if you have any doubts about what technology will work best for you, our expertise is at your service.

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