Computer Controlled Manufacturing

CNC Machine Tools

Machine tools are devices that perform material removal (also known as "chip removal") from a workpiece using a cutting tool attached to the machine. When this material removal process, carried out with cutting tools, is automated via coding and a computer, the machine is called a "CNC Machine Tool." There are three main processes in CNC machine tools depending on how the material is removed:

• Material removal by the cutting tool moving linearly while the workpiece rotates (CNC Lathe)

• Material removal by the workpiece moving linearly while the cutting tool rotates (CNC Milling)

• Material removal by the cutting tool moving linearly while the workpiece remains stationary (Electrical Discharge Machining (EDM), Guillotine Shears, Press Brake, Laser Cutting, Punching, etc.)

CNC machine tools are primarily composed of the following machines:

1. CNC Laser Cutting Machines: Machines used to cut materials using high-energy laser beams.

2. CNC Marking Machines: Machines that process specific depths using laser energy to engrave models, logos, or images onto materials.

3. CNC Punching Machines: Machines that use dies located in the machine's head to press and cut sheet metal into final shapes.

4. CNC Press Brake Machines: Machines used to bend sheet metal processed and cut to desired dimensions in laser or punching machines, shaping them under pressure.

5. CNC Lathe Machines: Machines used to process cylindrical materials.

6. CNC Vertical Machining Centers: Machines used to process prismatic materials.

These machines have become standard equipment in modern industry. There are thousands of additional machines that could be added to this list, from special production machines to presses, grinders, and guillotine shears, all of which are CNC-controlled and serve various purposes.

Numerical Control (NC)’un Tarihçesi

NC (Numerical Control) refers to the method of controlling machines through numerical data. This coding method first emerged after World War II, as the United States Air Force needed faster production processes. Developed in collaboration between MIT and Parsons Corporation, this method began in 1952 with a machine known as the Hydral Machine. A series of meaningful movements was created by perforating a paper tape, and on the Hydral machine, a reader would interpret the perforations and send signals to the motor or relevant parts, achieving the desired movements. This system enabled more efficient production.

History of CNC

CNC (Computer Numerical Control) emerged from the enhancement of NC (Numerical Control) with computer support. Instead of using perforated paper, G and M codes, which the machine could interpret, were introduced. The inclusion of computer support allowed for the simulation of these codes, preventing material waste and reducing errors. The most important aspect of CNC programming is ensuring that it is written in a logical sequence, adhering to algorithmic rules.

CNC Operator

A CNC operator is a person who shapes metal or non-metal materials to the desired form and dimensions or writes CNC programs and transfers them to the machine to execute the operation. The following are expected of a CNC operator:

➢ Knowledge of CNC machines and their types,➢ Understanding of workpiece clamping systems and their selection criteria,➢ Knowledge of cutting tools and clamping systems,➢ Familiarity with safety rules for working with CNC machines,➢ Ability to perform necessary calculations,➢ Capability to measure and inspect work,➢ Ability to read technical drawings,➢ Control the work based on manufacturing drawings,➢ Possess knowledge about materials, and➢ Maintain cleanliness and perform maintenance around the machine area.

Disadvantages of CNC Machines

• High initial investment costs,

• The need for a detailed manufacturing plan,

• High hourly rates for machine usage,

• Expensive fixtures and cutting tools,

• Require careful operation and maintenance,

• Regular maintenance must be performed by experienced personnel.

Advantages of CNC Machines

• No need to reprogram for mass production due to the machine’s memory,

• A separate power source that maintains memory even if the machine is turned off,

• Easy modification of CNC programs,

• The ability to execute more tasks with fewer lines of code using CYCLE commands,

• Standard tasks can be executed by calling ready sub-programs,

• Optimal spindle speed and feed rate can be achieved via the computer,

• High precision and speed in production,

• Minimizes losses in electricity, materials, time, and labor,

• Does not require expensive fixtures, jigs, or molds,

• Program simulation allows error detection beforehand,

• Automatic tool changes are possible.

Parts of CNC Machines

CNC machines consist of four main parts:

1. Body

2. Control Unit

3. Machine Spindle

4. Tool Magazine / Turret

Other components vary depending on the type of machine and its capabilities.

Control Unit in CNC Machines

Control units are produced differently by various manufacturers. Data transfer is made easy through RS-232C ports, USB drives, and Compact Flash cards on control units.

Tool Magazine in CNC Machines

The tool magazine is the mechanism on CNC machines where cutting tools are placed, and it facilitates the change of tools when needed. Depending on the capacity, 12 to 32 cutting tools can be attached. Types of tool magazines include:

• Umbrella-type magazines

• Disk or drum-type magazines

• Box-type magazines

• Chain-type magazines

Cutting Fluids Used in CNC Machines

High speeds during cutting generate high temperatures. To dissipate this heat, special fluids are directed toward the workpiece through specific channels to achieve the following effects:

✓ Dissipating heat during cutting,

✓ Preventing the cutting tool and workpiece from overheating,

✓ Reducing wear on the cutting tool,

✓ Ensuring the cutting tool completes the operation with consistent performance,

✓ Removing chips from the cutting area,

✓ Keeping the cutting area clean,

✓ Producing the desired surface quality on the workpiece,

✓ Acting as a lubricant for the machine and systems.

CNC Lathes

A CNC lathe is a type of automated machine that performs cutting operations by rotating the workpiece. The cutting tool approaches the rotating workpiece to shape it as desired. CNC (Computer Numerical Control) technology controls the machining process through programmable commands, allowing for precise cuts. CNC lathes are used for manufacturing workpieces of various sizes, typically preferred for cylindrical or conical parts. The machine has multiple axes of movement and rotates the workpiece to perform various machining operations.

Main Components of a CNC Lathe:

• Body and GuidesThe main structure and supporting components of the machine, typically made of robust and durable materials. The guides allow for the movement of components such as turrets, cutting tools, and the tailstock mounted on the body.

• SpindleThe spindle rotates the workpiece and performs the cutting process. It is typically driven by a central motor and belt system. The spindle is the most critical part of the machine, requiring high precision.

• Lathe ToolThe tool holder and cutting tools that perform the cutting operations. The lathe tool approaches the workpiece to execute the cuts. Different types of lathe tools are available, depending on the machine structure. The turret’s rotational movements are driven by a hydraulic or servo motor, and the tool stations typically come in sets of 8, 10, or 12. In some sources, the turret is also referred to by this name.

• Work TableThe section where the workpiece is placed and held. It secures the workpiece and is connected to the spindle, which rotates the piece.

• Drive SystemCNC lathes have drive motors and mechanisms that control the spindle and movable axes. This system ensures precise and accurate movement.

• Cooling SystemThe cooling system is used to cool the tools and workpiece during machining, preventing overheating and increasing cutting efficiency.

• TailstockIn manual lathes, the tailstock is used to support long workpieces. In CNC lathes, its movement is controlled by program commands or buttons/pedals. The pressure applied by the tailstock is determined based on the size of the workpiece.

• Control SystemThe control system is the programmable unit that operates the CNC lathe and processes commands. This system controls cutting speeds, tool directions, and other parameters. There are four main types of control units: FANUC, MITSUBISHI, SIEMENS, and LNC. The control system includes:

  • Hard keys: Buttons related to machine movements.

  • Soft keys: The keyboard section with alphanumeric keys.

  • Display: The screen section where the relevant program and all settings are displayed.

Types of CNC Lathes

• Flat Bed Lathes

• Twin Turret Lathes

• Multi-Axis Lathes

• Vertical Machining Center Lathes

• Sliding Headstock Automatic Lathes

• Horizontal Lathes

• Vertical Lathes

• Boring Lathes

• Turret Lathes

• Semi-Automatic Lathes

In addition to this, lathes can be classified into detailed categories based on the cutting process, machine structure, purpose of the machine, type of material being processed, number of tool holders, or the types of finished parts.

Workpiece Clamping Devices on CNC Lathes

• Three-Jaw Chuck: A type of chuck used to center and grip the workpiece. It is commonly preferred for holding circular or cylindrical parts.

• Four-Jaw Chuck: A type of chuck with four jaws. It is used to hold the workpiece more securely and compress it in a balanced manner.

• Cross Jaw Chuck: A type of chuck that allows precise centering of the workpiece. The cross jaw system facilitates achieving concentricity.

• Wedge Chuck: A type of chuck that has wedges for holding the workpiece. The wedges can be adjusted according to the shape of the workpiece and provide the clamping force.

• Surface Clamping Device: A type of device that holds the workpiece by attaching it to its surface or edge. Various surface clamping devices can be used depending on the shape and requirements of the workpiece.

• Parallel Clamping Device: A type of device used to hold the workpiece parallel. It grips and compresses the two edges of the workpiece, ensuring it is held properly.

• Custom Clamping Devices: Special clamping devices designed according to the shape, size, or specific requirements of the workpiece can be used. For example, various special devices are available, such as those for holding with screws or pins, magnetic holding, or vacuum holding.

Cutters Used in CNC Lathes

1. Triangle Roughing Tool

2. Square Roughing Tool

3. Profile Groove Tool

4. Right Side Finishing Tool

5. Left Side Finishing Tool

6. Straight Groove Tool

7. Outer Corner Profile Tool

8. Outer Thread Tool

9. Left Side Tool

10. Replaceable Tip Drill

11. Hole Groove Tool

12. Inner Thread Tool

CNC Milling Machines

CNC milling machines are automated milling machines that operate under computer control and can perform precise machining. These machines can carry out processes such as cutting, drilling, and surface finishing on different materials, thanks to their programmable features. CNC milling machines provide high precision, repeatability, and efficiency. Their computer-controlled nature offers flexibility in design and manufacturing processes, facilitating the production of more complex parts. CNC milling machines are used in various sectors, including automotive, aerospace, medical, and electronics, accelerating production processes and enhancing quality. CNC milling machines are generally used for machining cubic and prismatic parts.

Basic Components of a CNC Milling Machine

• Machine Body

  This is the main structural component of the machine, supporting all other parts. It is typically made of strong and durable material.

• Work Table

  This is the section where the workpiece is placed and held. It ensures that the workpiece remains stable and in the correct position during machining.

• Spindle

  This is the rotating part where the cutting tool is located. The spindle allows the cutting tools to rotate and perform the cutting operation.

• Cutting Tools

  These are the cutting edges used during machining. Different types of cutting tools are employed according to various machining needs.

• Motion Systems

  A series of drive motors and precision screws are present in a CNC milling machine to provide movement by moving and positioning the axes. The X, Y, and Z axes typically have the ability to move, and five-axis machines may also include A and B axes.

• Control System

  There is a control unit that manages the operation of the CNC milling machine and processes programmable commands. This system oversees the machining processes of the workpiece and provides coordination.

• Cooling System

  A cooling system is utilized to cool the tools and workpiece that heat up during machining. This helps prevent overheating and increases cutting efficiency.

Types of CNC Milling Machines

1. Vertical Machining Centers (VMC)

2. Horizontal Machining Centers (HMC)

3. Gantry Machining Centers

4. Bridge-Type Machining Centers

5. Five-Axis Machining Centers

6. Four-Axis Machining Centers

7. Universal Machining Centers (UMC)

8. Turret Machining Centers

9. Vertical Turret Machining Centers

10. Horizontal Turret Machining Centers

11. Wheel Machining Centers

12. Rotary Table Machining Centers

13. Parallel Machining Centers

14. Grinding Machining Centers

15. High-Speed Machining Centers

16. C-Frame Machining Centers

17. Tool Changer Machining Centers

Here’s the translation:

Workpiece Clamping Devices in CNC Machining Centers

• Chuck:These are devices used to clamp and secure the workpiece. They are typically used in rotating machining operations.

• Clamping Fork:These are two-piece devices used to clamp the workpiece. They provide stability by gripping the four corners or edges of the workpiece.

• Parallel Vice:These are devices used to secure the workpiece in a flat and parallel manner. They hold the workpiece firmly by applying pressure on both sides.

• Pliers-Type Clamping Device:These are devices used to secure small workpieces. They are used to clamp the workpiece and hold it in the desired position.

• Vacuum Table:These are devices used to secure flat and smooth-surfaced workpieces. They secure the workpiece by drawing it in with a vacuum effect.

• Custom Clamping Devices:These are specialized devices designed according to the shape and characteristics of the workpiece. They ensure the workpiece is held correctly according to specific requirements.

Cutters Used in CNC Machining Centers

• Face Milling Cutters

• Profile Cutters

• Groove Cutters

• Gear Milling Cutters

• T-Slot Cutters

• Chamfer Cutters

• Replaceable Tip End Mills

• Local Milling

• High-Performance Milling

• Plunge Milling

• Pocket Milling

Cutting Tool Holder Devices Used in CNC Machining Centers

• Veldon Tool Holders

• Hydraulic Tool Holders

• Heat Shrink Tool Holders

• Collet Tool Holders

• VDI Tool Holders

Machine Tools

1. Drilling Machines

   Drilling machines are tools used to create holes in materials using a rotating cutter. They are commonly used for drilling materials such as metal, wood, or plastic.

2. Grinding Machines

   Grinding machines use an abrasive stone or wheel for processes like smoothing, cutting, or shaping the surface of materials. They are typically used for machining metal parts.

3. Tool Grinding Machines

   Tool grinding machines are used to restore the sharpness of cutting tools (such as drill bits, mills, lathes, etc.) or to shape their cutting surfaces.

4. Gear Machines

   Gear machines are tools used for the production or machining of gears. They are used for cutting gear profiles, creating teeth, or shaping gear wheels.

5. Planer and Surface Machines

   Planer and surface machines are used for flattening or shaping flat surfaces. Planer machines are typically used for larger parts, while surface machines are used for smaller and more precise operations.

6. Boring Mills

   Boring mills are machines used for drilling, milling, and other operations on large and complex parts. They are commonly used in large-scale industrial production.

7. Presses

   Presses are machines used for shaping, bending, cutting, or compressing materials. They are generally used for the production of metal or plastic parts and come in various strengths and capacities.

Fundamentals of Programming

CNC (Computer Numerical Control) machines are industrial machines that automatically process workpieces and optimize production processes. Programming these machines is based on fundamental knowledge to determine how the workpiece will be shaped and processed. In CNC machines, coding enables the design created using CAD (Computer-Aided Design) software to be converted into a format understandable by the machine through CAM (Computer-Aided Manufacturing) software. During this coding process, factors such as the dimensions of the workpiece, the movements of the cutting tools, cutting speeds, and cutting depths are taken into account. Coding in CNC machines is critical for accurate and efficient production, significantly affecting the quality and precision of workpieces. Key coding values in CNC programming include:

G Codes

G-codes are standard commands in a language used to control the movements of cutting machines. For example, the G00 command is for rapid movement, while G01 is for linear cutting. G-codes guide the movement of the laser machine by determining parameters such as cutting speed, feed rate, positioning, rotations, and cutting depth.

M Codes

M-codes are commands used to control various functions of the CNC machine. For example, the M03 command turns the laser on, and M05 turns it off. M-codes manage functions like laser power control, cooling system management, and focusing adjustments.

X, Y, and Z Coordinates

X, Y, and Z coordinates are used to determine the points at which the laser will cut. The X and Y axes represent the position on a plane, while the Z axis represents depth or height. These coordinates determine the precision of the cutting process.

Feed Rate

The feed rate determines the speed at which the laser moves while cutting the workpiece. It is adjusted based on the material properties of the workpiece and the quality of the cut. It is typically expressed in mm/min.

Laser Power

Laser power determines the ability of the laser to cut the workpiece. Different materials may require different laser power levels. It is usually expressed in watts.

Focus Depth

Focus depth defines the depth at which the laser beam is focused on the workpiece. Focus depth is adjusted based on material thickness and cutting requirements.

Cut Path

The cut path determines the route that the workpiece will be cut along by the laser. An appropriate cut path is selected based on the geometry of the workpiece. For example, cutting can be done from the inside out, from the outside in, or through scanning cuts.

The above example illustrates how coding is done and shows the path that the tool will follow during simulation. It would be more appropriate to examine the details of this topic under a different heading. Especially, production machines are like an ocean, and the information provided here is just a drop in that ocean. To learn more, you should dive into the subject and experience different aspects. Wishing you to learn something new every day. Have a nice day!