Machining processes are the techniques used for removing material from a workpiece (an item that is being manufactured). This article summarizes the three main categories of machining processes; discusses the desirable characteristics of machining processes; and examines aspects of nontraditional machining processes. Finally, the article defines terms and concepts that are relevant to the topic of machining processes.
Keywords Abrasive Processes; Cutting Processes; Disruptive Technology; Laser; Machining; Machining Processes; Manufacture; Milling; Nontraditional Processes; Outsourcing; Prototype; Turning; Waterjet Cutting Processes; Workpiece
Manufacturing: Machining Processes
Our study of machining processes begins with definitions for two important terms:
- Machining Processes
In the manufacturing industry, a workpiece refers to an item that is in the process of being manufactured.
Machining processes are the techniques used for removing material from a workpiece. Generally, machining processes can be grouped into three categories of processes:
- Cutting processes: These processes utilize single-point or multipoint cutting tools, each with a clearly defined geometry. Machining processes that are considered to be in the cutting processes category include milling (cutting material with a rotary cutter) and turning (rotating the workpiece in order to cut cylindrical parts). Basically, cutting processes involve the machining of an external surface with the workpiece rotating. Most often, it utilizes a single-point cutting tool.
- Abrasive processes: These processes include methods such as grinding.
- Nontraditional processes: These processes utilize electrical, chemical, or optimal sources of energy. See "Laser micromachining" and "Waterjet cutting" in the Applications section (Michigan Technological University, 2007).
Choosing the Appropriate Machining Processes
How do manufacturers go about choosing the appropriate machining processes?
Manufacturers choose their machining processes based on a combination of factors dictated by their own unique circumstances, the workpiece itself, ease and safety of use, and cost. Haftl (2007) presents a table containing five machining processes for metals.
The table provides a ball park price for the equipment for each process and indicates how each process performs in six categories: Thickness of material machined; type of material machined; ability to make perpendicular cuts; speed of cutting; best features; and worst features.
Desirable Characteristics of Machining Processes
Regardless of the type of machining process, manufacturers strive to ensure that the processes will exhibit the following four desirable characteristics:
The first desirable characteristic of machining processes is suitability. Suitability indicates that the machining processes are appropriate for the composition of the workpieces being machined. Certain machining processes are only suitable for thin or rigid materials. Other machining processes are only effective for cutting very small pieces.
The second desirable characteristic of machining processes is safety.
Machining processes safety covers three areas:
- The item
- The workers or operators
- The environment
Item safety ensures that the machined part or item meets safety standards for usage. When discussing machining processes, we might typically think of user safety in relation to end products such as tools, furniture, or other household items. However, machining processes are also used on food products, which would require scrupulous adherence to sanitary requirements. See "Example of Waterjet Cutting: Frozen Fruit" in the Applications/Further Insights section.
Worker or Operator Safety
Worker or operator safety ensures that the machining processes and tools are safe for the workers or operators who are performing the machining process tasks.
The U.S Department of Labor oversees compliance of fair labor practices, including safe working conditions. The U.S. Occupational Safety & Health Administration (OSHA), an agency within the Department of Labor, enforces the federal laws and regulations concerning safe working conditions. In addition, OSHA encourages individual states to set up their own occupational safety and health programs that OSHA monitors after approving them. To date, 26 states have set up OSHA-approved safety and health programs (United States Occupational Safety & Health Administration, n.d.).
The issues surrounding safety guards for machines are reviewed in "Materials address safety guarding issues" (Metalworking Production, 2005, p. 15). According to the article, the frequent opening and closing of machine guards can cause serious occupational injuries. In addition, the removal of machine safety guards very often leads to industrial accidents. So, why would anyone remove the safety guards on machines? It seems that guard systems that are often heavy steel or wire mesh are difficult to use; therefore, the guards are more likely to be removed or bypassed. The solution proposed in the article is to replace heavy machine guards with guards made of lighter, more flexible materials, such as Perspex with gas spring supports or glass with rotating wiper portholes. These two types of machine guards provide a weightless, balanced lift when the doors are opened and also allow for clearer observation of the work process.
Environmental safety ensures that the machining processes and their byproducts do not pose hazards to the environment. In addition to any state and local environmental regulations, manufacturers must comply with the laws and regulations of the U.S. Environmental Protection Agency.
The third desirable characteristic of machining processes is accuracy. Accuracy refers to the ability of the machining processes to consistently yield an item that accurately meets specifications on the first cut.
The last desirable characteristic of machining processes is cost-effectiveness. To be cost-effective, the machining processes need to be performed at a cost that yields a profit for the manufacturer but is still affordable for customers.
The cost-effectiveness of machining processes is mainly affected by the following factors:
- The price of materials
- The price and reliability of equipment
- The availability of skilled labor
- The cost of compensation for employees
- The cost of overhead (rent, insurance, utilities)
- The speed of the machining processes
- The manufacturer's competitive position in the marketplace
The Price of Materials
Although the price of materials is largely dictated by supply and demand, manufacturers still negotiate for the best prices from suppliers.
Manufacturers will of course attempt to negotiate the best prices for the purchase or rental of their equipment. However, the reliability of the equipment — how long it can operate perfectly without the need for repair or replacement — affects both the true cost of the equipment and the speed of machining processes.
The Availability of Skilled Labor
Access to a skilled labor pool is crucial for manufacturers. Skilled labor includes the employees who operate the machines and the employees who supervise them and the plants. If a manufacturer outsources part or all of his machining processes to...
(The entire section is 3586 words.)