Understanding ‘What is Machining?’ is important for manufacturers in every sector. Machining processes are the foundation of modern manufacturing industries and can shape metals and other materials into a finished product for consumer use. Machining tools also work on raw material processing for secondary industries.
Machining processes have many different types to suit the needs of different industries. Each type further has the option of many cutting tools. Having a comprehensive idea of these types and tools beforehand provides a better execution for your particular project.
Therefore, this article will have an in-depth discussion on ‘what is machining?’, the different types of machining operations, machining cutting tools, advantages, limitations, and many tips that can optimize the process for you.
What is Machining?
Machining is a manufacturing process where the desired shape is created by removing material from a larger piece. It is used for making finished products and for raw material processing. Machining processes are also known as subtractive manufacturing processes. Complex parts often require the use of multiple machining processes in conjunction with each other.
Most machining processes have high control over the material removal for utmost accuracy. Almost all materials, including metals, wood, glass, plastics, ceramics, and more, support machining operations.
Brief History of Machining Processes
Machining is not a recent manufacturing process. Early machining tools went as far back as 1200 BC. These tools used handicraft operations for making weapons and basic utilities. Primitive versions of manual lathes date to Ancient Egypt. With time, the machining processes progressed to include higher production speed, more complexity, and a degree of automation.
When Was Machining Invented?
John Wilkinson can be credited with the invention of early machining tools. He made a boring machine in 1775 for manufacturing steam engine cylinders. The industrial revolution further pushed innovations in machine tools and processes. Eli Whitney also provided several inventions in machining tools. These were used for making muskets for the US Army.
Development of Machining in the 20th Century
The growth of machining technology rapidly paced in the 20th Century. The concept of modern machines developed and improved during this time period. The growth of parallel technologies such as computing and CNC further added new capabilities to these machining tools and processes.
Machining in the 21st Century
The 21st century focuses on precision machining on a micro and nanoscale. Additionally, complex multi-axis machines add new dimensions to the geometry that can be machined. Additionally, machining techniques use advanced science, such as laser cutting and electric discharge machining.
How Machining Works?
Machining processes rely on a machine tool to work on the raw materials to create the desired shape. Modern machine tools are mostly automated. They use inbuilt computing to interpret the commands and work on the part. The method of commands depends on the type of technology that the machine uses. Most modern machining tools are based on Computer Numerical Control (CNC), which uses CAM programming.
Different Stages of Machining Processes
Machining processes go through multiple stages to complete the part production. These different stages are:
- Designing Part: For automated manufacturing using a CNC machine, a graphical design of the part is made. The design is saved as a Computer Aided Design (CAD) file. Minor adjustments and manual machining might not require designs.
- Creating CAM File: The CAM file contains the G-code that the machine can understand. The programmer converts the CAD file to a CAM version. The operator then loads this file to the machine. For machines without CNC, the CAM file is not needed.
- Machine Setup: Every machine requires setup before executing the machining process. Setup includes loading the workpiece, adjusting the settings, and ensuring tight connections.
- Machining: The machine begins execution once the setup is complete. The execution is done in the presence of the operator.
- Unloading: The finished product is removed from the machine. It is then sent for secondary assembly or additional machining processes as needed.
Different Types of Machining Operations
The vast applications of the machining process have led to the emergence of many types of machining processes and operations. These 11 most prominent machining types are:
Milling tools involve high-speed rotary cutting tools. The workpiece materials are kept stationary at the work table. The shape of the cutting tool can vary based on the requirement. Some common examples are end mills, face mills, and thread mills.
Applications of Milling
Milling machines are commonly used for manufacturing gears. Making grooves and slots in a workpiece is also done with milling tools. Niche milling tools are used for applications such as keyholes.
Boring tools are used to expand holes in a workpiece. The holes can be further designed to meet particular requirements. Examples include tapered holes. Boring tools have many forms, like back boring and line boring.
Applications of Boring
Boring is done to create hollow cylindrical shape metals like engine shafts and gun barrels. Boring tools are often used to increase the accuracy of already drilled holes.
Broaching uses a toothed cutting tool for removing material from the workpiece. There are two variations of the broaching process- linear and rotary. Linear broaching is the more common of these two basic types. A broaching machine often shortened to broach.
Applications of Broaching
The common application of broaches is for making gears and splines. Broach is also used for making keyholes. Bearing caps and cylinder block machining also utilizes broaching.
Drilling tools are the most common types of machining equipment. The purpose of drilling is to make holes in raw materials or finished workpieces. Drilling tools create holes of smaller diameter, unlike boring tools. Drilling can be a part of CNC machining or done manually. Even handheld drills are available for small-scale workshops and independent professionals.
Application of Drilling
The most common application of drilling tools is to make screw holes. Drilling also creates holes for secondary assembly. At times, drilling is used for making holes with an aesthetic purpose.
Grinding is another very common machining process. It uses abrasive wheels to remove minimal material from the workpiece. Grinding tools cannot create significant changes to the workpiece shape. However, they can improve the surface finish of the workpiece. Grinding also enhances the accuracy of the workpiece for secondary assembly.
Application of Grinding
Grinding is generally used as a secondary machining process. It can remove the marks and unwanted burrs created by other metalworking processes. For instance, grinding tools can remove the unwanted burrs of welding. Grinding can also make minimal changes to the dimensions of a part. This is done to fit a part tightly in a slightly smaller space.
Turning uses a stationary cutting tool against a high-speed rotating workpiece. The tools remove material from the workpiece in a symmetrical manner. Turning tools are usually applied for cylindrical and conical-shaped parts.
Application of Turning
The turning process is commonly used for making automotive parts like engine shafts and components. It can also create helical grooves, tapers, contours, and steps of varying diameters.
Reaming uses a multi-edge cutting tool to enlarge previously drilled holes. The holes are themselves created by processes like drilling. Reaming removes very little material from the hole to add precision. Reaming tools can be used on drilling benches, lathes, mills, and other machining equipment.
Application of Reaming
The main reaming application is to create round holes with a good aesthetic finish. It can also create tapered holes.
Planing is used to machine surfaces of material blocks. The cutting tool is held stationary, and the workpiece is brought against it. The cutting tool removes material from the surface according to the shape of the tool. The cuts can be straight or angled into the workpiece. Special extension cutting tool can be used on planers to make internal shapes.
Applications of Planing
Commonly, planer machines are used for making slots and grooves. Planer tools can also create flat surfaces accurately. Using a curved planer can generate curved surfaces. Additionally, planing is also common to make dovetail joints in woodworking.
Sawing uses material cutting with toothed or smooth blades. The blades can be linear, curved, or even rotary. Sawing tools are available in various manual and CNC machine configurations. Common configurations are band saws, table saws, and jig saws.
Application of Sawing
Sawing is commonly used for raw material processing. It can cut metal bars, sheets, pipes, and other shapes. Sawing is one of the most common processes in woodworking.
Water Jet Cutting
Waterjet cutting is a versatile and precise machining technique that uses a high-pressure stream of water, often combined with an abrasive substance, to cut a wide variety of materials. Abrasive materials are added to the water stream to increase the cutting power.
The process works by forcing water through a tiny nozzle at an extremely high pressure, typically 50,000 PSI or higher. This powerful stream can cut materials accurately without introducing heat, making it an ideal solution for materials that are sensitive to high temperatures.
Waterjet cutting is used in industries where preserving material integrity is important. Common examples are:
- Cutting metals, including steel, aluminum, and titanium
- Processing materials like granite, marble, glass, and ceramics
- Fabrication of parts in the aerospace and automotive industries
- Creation of intricate designs in the arts and architecture
- Cutting food products in the food industry
- Prototyping and model making in various industries
Waterjet cutting presents several advantages over other similar technologies, such as:
- No heat affected zone (HAZ): Unlike other cutting methods such as laser and plasma cutting, waterjet cutting does not produce heat. This is critical when working with materials that are sensitive to high temperatures, as it prevents thermal distortion and hardening, ensuring the structural integrity of the material is maintained.
- Ability to Cut Nearly Any Material: Waterjet technology can cut a wide range of materials that other methods struggle with, including metals, ceramics, composites, laminated materials, glass, stone, and even rubber. This technology also works well for materials of varying thicknesses.
- High Precision and Accuracy: Waterjet cutting is known for its high precision and accuracy. The technology allows for intricate designs and patterns to be cut with a high degree of accuracy, often within 0.005″ or better.
- Environmentally Friendly: Waterjet cutting is a more eco-friendly option compared to other cutting technologies. It doesn’t create hazardous waste or fumes, and the water and abrasive materials used in the process can often be recycled. Also, since it doesn’t generate heat, it reduces the energy footprint
- Reduced need for secondary finishing processes, saving time and resources.
Burning Machining Technologies
Burning tools apply heat to melt the material and separate it into multiple pieces. The application of heat can be done in a variety of ways. This leads to many types of burning machining techniques. The different types of burning techniques are:
Laser cutters melt excess stock material with high-powered light beams. Light beams can be focussed to extremely thin dimensions. Therefore, laser cutting is highly precise compared to any other cutting tool.
Plasma cutting uses an ionized jet of gases to remove material. The airflow helps in removing the melt automatically. Plasma cutting only works for electrically conductive materials.
Oxy-fuel cutting uses a mixture of oxygen and fuel like acetylene to emit a high-temperature flame. The flame then melts the materials to create the cut. The major benefit of this method is its portability. However, oxy-fuel cutting does not provide precision machining. It also leaves unwanted burn marks on the materials.
What are the Different Types of Cutting Tools in Machining?
All machining techniques utilize cutting tools for removing materials from the workpiece. The cutting tools are made of metals and metal alloys. Cutting tools come in various shapes and sizes to suit different requirements. The different types of cutting tools are:
Linear Cutting Tools
Linear cutting tools have straight-line edges. These tools are usually stationary and do not rotate around any axis. Some machines can have a linear motion of these tools. Examples of linear cutting tools are broaches and single point tool bits.
Rotary Cutting Tools
Rotary cutting tools have a circular wheel-like shape. The rotating cutting surface removes material due to a combination of sharpness and friction. These cutting tools can sometimes have toothed edges for smoother operation. Rotary cutting tools include drill bits, countersinks, reamers, and cold saws.
Hybrid Cutting Tools
A hybrid tool doesn’t fall completely into the class of linear or rotary cutting tool. Instead, it includes features of both these classes. Example of hybrid cutting tools are hacksaws, bandsaws, and fly cutters.
Indexable tools have swappable tips that are inserted into the cutting tool. The tool tips are generally made from a different material. The tip can be joined by clamping, brazing, soldering, or welding. Indexable tools are generally used in end milling tools, fly cutters, and saw blades.
Multi-Point Cutting Tool
A multi-point cutting tool is a complex tool with two or more cutting edges. All these edges remove material from the workpiece simultaneously during a single pass. Common examples of multi-point cutting tools are broaches, hobs, grinding tools, hone, and milling cutters.
Advantages of Machining
A commonly asked question regarding machining is ‘Does machining have any advantages?’ Evaluating the advantages of machining becomes even more important when considering the close competition with additive manufacturing techniques. Here are some of the advantages that machining has to offer:
- Unlimited Materials: Machining techniques can work on all types of materials. This is a major advantage over additive manufacturing techniques which work only on a limited set of materials.
- Surface Finish: Machining processes create a very smooth surface on the workpiece. An even greater smoothness can be achieved with processes like grinding. Processes like etching can further push the boundary of what is possible in terms of surface finishing.
- Precision: CNC machining has some of the lowest tolerances in industrial manufacturing processes. In fact, many CNC machining processes come under the umbrella term of ‘precision machining’. Machining tolerances can be as low as +/- 0.001″.
- Production Rate: CNC machining is a high speed process. Therefore, it can easily meet the demands of mass production. Additionally, techniques like multi-axis machining further speed up the production rate.
- Consistency: Machining processes are highly consistent in terms of outcome. Consistency is a major requirement for most industries. Machining techniques always produce identical parts.
- Less Labor Intensive: A CNC machine is highly automated equipment. It frees up most of the human labor for other high-priority tasks. A CNC machine generally requires labor only for loading and unloading of parts. Besides that, only one operator is enough to oversee the machine operation.
Are There Any Limitations to Machining?
Machining is the go-to option for modern manufacturing industries. Even so, there can be certain limitations to machining techniques. These limitations are:
- Workable Sides: Regardless of the number of axes, some sides of the workpiece will be left out of machining. To machine these sides, the workpiece needs to be removed and repositioned.
- Operator Skill: CNC machine operations are dependent on the operator’s skill. An unskilled operator can cause poor results or damage the machinery and workforce.
- Initial Investment: Capable precision machining equipment can require a high initial investment. The initial capital can be a limitation for small-scale machine shops.
- Material Wastage: Machining removes a lot of unwanted material from the workpiece. This results in high material wastage. In some cases, the material can be recycled and sold as scrap. However, it can be difficult to dispose of this material in many cases.
- Time Consumption: In some cases, machining processes can be more time-consuming than alternatives like 3D printing or injection molding.
What Types of Materials Can Be Machined?
The major attraction of machining techniques is the freedom to choose any material. Machining processes work on materials of any class. Some common materials that undergo machining are:
Metals and Alloys
Metals and metal alloys are the most commonly used machining materials. Machining metals provide significantly higher accuracy and surface finishing than alternative manufacturing techniques. Some example of machined metals and alloys are:
- Steel (All grades)
Machining plastics is common for making consumer goods such as electronics. Plastics can also undergo 3D printing and injection molding. However, machining offers better consistency and precision. A common consideration during plastic machining is the release of toxic fumes due to heat.
Some examples of plastics that undergo machining are:
- Acrylonitrile Butadiene Styrene (ABS)
- Polycarbonate (PC)
Wood machining techniques ensure a freedom to create complex wooden shapes. A common consideration when machining wood is the generation of wood dust. Additionally, when machining plywood, care must be taken not to delaminate the different layers of wood.
Common examples of machinable woods are:
- Engineered Woods
Important Skills For Quality Machining Projects
Machining is not a single skill-set job. It requires a combination of skills for exceptional quality results or execution of complex projects. Some of the skills that are useful in machining are:
- Mechanical Engineering: Mechanical engineering provides a clear idea about materials’ strengths, limitations, and usability. Lack of this skill can result in the breakdown of parts during or after machining.
- Graphic Designs: Graphical designs of the parts are required before machining them. The graphical design displays how the part will turn out in 3D.
- Computer Programming: Programming is essential for machining using CNC. Programming skills are used for making CAD and CAM models of the part.
- Operator Skill: The operator skill can vary based on the machine used. Operator skills are gained with training and experience on the machine.
Modern manufacturing is incomplete without machining processes. Machine shops use different types of processes in tandem to create parts. Every project uses machining in multiple stages, from R&D to prototyping to mass production. If you are looking for manufacturing methods for your next project, machining techniques can be a great fit for you.