Numerical control, also known as computer numerical control (CNC), is an automated control system utilized in machining, transforming materials like metals, wood, and stone into specific shapes. This technology is utilized in various tools like drills, lathes, mills, grinders, routers, and 3D printers.
NC machining allows for data storage during the machining process, while CNC offers more flexibility and capacity in handling logical operations. Both NC and CNC machines are essential in cutting and shaping metals. Well, in this reading, we’ll be discussing NC machining, its applications, diagrams, types, and how it works. We’ll also explore the advantages and disadvantages of numerical control machining as well as their difference with CNC machining.
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What is Numerical Control Machining?
Numerical control is a crucial aspect of machines, enabling precise control of movements and operations. These machines, which rely on computer programming and numerical data, have significantly improved production efficiency, accuracy, and repeatability in various industries.
This has led to the development of CNC (Computer Numerical Control) machines, which further integrate computers to control their functionalities, enabling more sophisticated machining processes.
NC machines use predefined alphanumeric codes to guide the movements of specific tools, allowing for efficient and precise control of parameters like motor speed, feed rate, rotation direction, and depth of cut. This streamlined manufacturing process offers enhanced accuracy and automation for various machining operations.
Numerical control (NC) is a form of programmable automation used in machine tools, where processes are controlled by numbers, letters, and symbols. NC machines are controlled by a set of instructions called a program, which can be changed based on job types. NC provides flexibility in its use, as it allows for easy writing of new instructions for each job.
It can be applied to various operations like drafting, assembly, inspection, and sheet metal working, but is more prominently used for metal machining processes like turning, drilling, milling, and shaping. NC allows for fast machining operations, making bulk manufacturing more affordable. Overall, NC offers a flexible and cost-effective solution for various machine tools.
Applications
Numerical control technology is a crucial tool in various production operations, including metal cutting, automatic drafting, spot welding, press working, assembly, and inspection. It is particularly useful in metal machining operations, such as turning, sawing, grinding, milling, drilling, and boring.
NC machines are most suitable for complex, expensive, high metal removal jobs, where 100% inspection is required, and close tolerance is required. They are often used in small batch lots or short production runs. NC machines excel in producing parts with intricate contours, close tolerances, and excellent repeatability.
They are also suitable for parts undergoing frequent engineering changes, where human errors could lead to significant costs, urgently required parts, and small batch lots or short production runs. Overall, NC technology plays a vital role in the metal-cutting industry.
Parts of NC Machines
The central part of a NC machine is the controller, which processes input instructions and directs machine tools to perform desired operations. This component is more advanced, capable of handling complex algorithms and real-time data processing.
Machine tools, such as drills, lathes, and mills, perform the actual machining operations, with greater range and flexibility in CNC machines. Traditional NC machines used punched tapes for input instructions, while modern machines use digital methods like CAD files and CAM software.
Servo motors control the movement of machine tools, ensuring precision and accuracy. They receive signals from the controller and move the tools to the correct positions. NC machines also use servo motors, but with enhanced capabilities for smoother and faster movements. Feedback systems monitor operations and ensure machine tools are performing as instructed, providing real-time adjustments to maintain accuracy.
The basic components of an NC (Numerical Control) machine include Set of instructions, a Machine Control Unit (MCU), Signal Output Channel, Tape Reader, Data Buffer, Feedback Channel and Machine Tools.
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Machine Control Unit (MCU)
Machine Controller Unit are made mostly of hardware and electronics, this unit reads and interprets the program of instructions to translate them into the machine tool’s mechanical operations. It regulates tool changes, feeds, equipment flows, and other processes. Tape readers, data buffers, signal channels, feedback channels, and sequence coordinators are parts of a conventional NC controller unit.
Set of Instructions
A broad set of detailed instructions that specify the machine tool’s operations; these instructions are encoded in a symbolic or numeric format for the controller unit to interpret. L-in-wide tapes are now the most often used input medium for NC machines, but they have changed over time. Additional techniques include direct numerical control (DNC) connected to computers and manual data input (MDI) for basic jobs.
Feedback Unit
Feedback unit also referred to as the position feedback package, this device informs the control unit of the precise location of movements. After comparing the desired and actual motions, the control unit actuates the drive units to make the appropriate adjustments.
Machine Tool
This part, which can be any kind of equipment or machine tool, carries out the specified tasks inside the NC system. A worktable, a spindle-like motor, and the controls required for operation are all built into machine tools used in standard machining tasks. Cutting tools, work fixtures, and other auxiliary equipment necessary for the machining process are all included in the machine tool.
Drive Units (Servo Motors)
A Powerful DC servomotors positioned on preloaded ball bearings operate the machine’s axes. The servomotors are triggered by signals from the control unit, which moves the machine slides to the required feed rate and travel distance. Stepping motors or hydraulic DC motors may be used by the driving units.
Magnetic Box
With the exception of servo motor drives, the magnetic box is in charge of receiving electrical signals from the control unit for a variety of machine operations. Among other things, the magnetic box regulates the coolant supply, tool changes, spindle speed selection, and spindle motor start/stop.
Control Panel (Manual Control):
Using dials and switches to operate the machine, the control panel, which can be a component of the controller unit or machine tool, enables the machine operator to communicate with the NC system.
Sensors
NC machines rely on sensors for accuracy and efficiency. Position sensors, such as encoders and resolvers, monitor machine components for precise movements. Force sensors measure cutting force to prevent tool damage and maintain machining quality.
Temperature sensors monitor components and workpiece temperature, allowing adjustments to prevent overheating and maintain material properties. Vibration sensors detect excessive vibrations, allowing machines to adjust parameters to minimize vibrations and maintain tool life.
Diagram
Types of NC System
The various types of NC systems are Traditional Numerical Control (NC Machine), Computer Numerical Control (CNC Machine), Distributed Numerical Control (DNC Machine).
Traditional Numerical Control (NC Machine): is an evolution of conventional machines that uses a tape reader system to perform tasks by punching instructions onto a tape.
Computer Numerical Control (CNC Machine): CNC machines, developed after NC machines, use a computer-generated file containing G-Codes and M-Codes to store programs, allowing for instant changes to parameters like speed, feed, and depth of cut, resulting in highly accurate and efficient machines.
Distributed Numerical Control (DNC Machine): DNC machines, similar to CNC machines, use a remote computer to control multiple machines simultaneously, communicating with local CNC computers to execute operations.
Types of NC Machines
The following are the various types of numerical control machines include Point-to-Point (PTP) Machines, Continuous Path (Contouring) Machines, Dedicated Machines, Modular Machines, and Adaptive Control Machines
Point-to-Point (PTP) Machines: Point-to-Point (PTP) machines are ideal for tasks like drilling, spot welding, and punching where tools need to move to specific locations for operations. They precisely control tool position, ensuring high accuracy. PTP is an NC system that controls only component position, not component motion relative to the workpiece. The machine moves between different positions at the traverse speed allowable for the tool and follows the shortest path, ensuring efficient and accurate operations.
Continuous Path (Contouring) Machines: Continuous movements are performed along a defined path by machines, known as contouring machines. These machines, unlike PTP machines, can move simultaneously along multiple axes, creating intricate and smooth surfaces suitable for operations like milling and complex cutting tasks.
Dedicated Machines: Machines are specialized tools designed for high efficiency in performing repetitive tasks, such as drilling, boring, or cutting. These machines are often used in mass production environments, offering high speed and accuracy, making them ideal for specific tasks.
Modular Machines: Modular Machines are suitable machines for various tasks, allowing manufacturers to customize and adapt them by adding or removing modules, making them highly versatile and adaptable.
Adaptive Control Machines: Adaptive Control Machines utilize real-time feedback to adjust operating parameters, enhancing precision and efficiency by responding to changes in the machining environment and optimizing performance accordingly.
How Does NC Machining Works?
NC machining, or Numerical Control machining, is a process that involves precise steps controlled by pre-programmed instructions. This allows for automated and accurate control of machine tools, resulting in consistent and high-quality production.
The main stages of NC machining include programming the machine with specific instructions, often in the form of G codes and M codes, using computer-aided design (CAD) and computer-aided manufacturing (CAM) software. Once the program is ready, the machine tool is set up, including installing cutting tools and securing the workpiece.
The machining operation begins with the loaded program and the machine set up, following the programmed instructions for tasks like drilling, milling, or cutting. Each movement and operation is controlled by the pre-defined instructions, ensuring high precision and repeatability.
After the machining operation is complete, the final product is inspected to ensure it meets the required standards. This inspection can involve measuring the part’s dimensions, checking for defects, and verifying that the part matches the design specifications.
NC Machine Tools
NC machining requires a range of tools and equipment to ensure precise and efficient operations. These tools include cutting tools, tool holders, workholding devices, measuring instruments, cooling systems, programming software, control units, and chip removal systems.
Cutting tools, such as drills, end mills, and lathe tools, are used to shape materials like carbide, high-speed steel, and diamond-tipped. Workholding devices, including chucks, vises, and clamps, secure the workpiece during operations.
Measuring instruments, such as calipers, micrometers, and gauges, measure dimensions and ensure accuracy. Coolant systems deliver coolant to reduce heat and friction. Programming software, such as CAD and CAM, creates and simulates NC programs. The control unit interprets program instructions and controls the machine’s movements.
NC Machining Software
NC machining relies on advanced software to program and control machines, ensuring precision and efficiency. Key software tools include Computer-Aided Design (CAD) software, which creates detailed 2D and 3D models of parts, and Computer-Aided Manufacturing (CAM) software, which converts CAD models into machine instructions.
G-Code Generators translate CAD/CAM data into G-codes, which NC machines understand. Simulation software helps detect errors before production, while machine control software interfaces with NC machines to execute instructions.
Tool management software manages and tracks cutting tool use, while quality control software ensures parts meet specifications and tolerances. Data collection software monitors machine performance and collects data for analysis. Production planning software helps schedule and manage the machining workflow, using ERP systems like SAP and Oracle.
Common NC Machining Operations
NC machining is a crucial tool in various manufacturing processes, including metal cutting, spot welding, plasma cutting, laser cutting, milling, turning, drilling, drilling, 3D printing, grinding, and broaching.
These processes use cutting tools to shape metal parts, providing precision in milling, turning, and drilling. Spot welding is used in automotive and electronics manufacturing, while plasma cutting uses a high-velocity jet of ionized gas for complex shapes and thick materials.
Laser cutting uses a focused laser beam for high precision and fine detail. Milling involves removing material from a workpiece using rotary cutters, turning produces cylindrical parts, drilling creates holes for precise components, and 3D printing is an additive manufacturing process that builds parts layer by layer. Grinding uses abrasive wheels for fine surface finishes and precise dimensions, and broaching involves using a toothed tool to create complex shapes.
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Advantages and Disadvantages of NC Machining
NC machines offer several advantages, including reduced non-productive time, faster work completion, greater flexibility, improved quality, space efficiency, user-friendly operation, elimination of human errors, labor cost reduction, and high dimensional accuracy.
They require less floor space due to their automated tooling system, and can be operated by less skilled labor. Automation minimizes human errors, ensuring consistent and reliable results. NC technology also reduces labor costs as it requires minimal human involvement.
However, NC machines also have some disadvantages. They require a substantial initial investment due to their intricate and complex technology, which must be used aggressively to recover costs. They also require higher maintenance costs due to their heavy usage, requiring more frequent and costly repairs.
Operating NC machines requires highly trained personnel with expertise in handling intricate technology, making it challenging to find, hire, and train skilled employees. Additionally, programming training is required for making changes to the machine and troubleshooting issues, emphasizing the need for specialized training and expertise. Overall, NC machines offer numerous benefits but also present challenges in terms of investment, maintenance, and programming training.