Crafting Precision: The Artistry Behind CNC Milling Parts

A CNC milling machine consists of many different parts that each play an important role and work together to accomplish a variety of milling tasks. In this article, we will introduce the main parts of a CNC milling machine in detail to help you better understand their functions and roles.

1. column:

The column is one of the support structures of a CNC milling machine and is usually located on the base of the milling machine. It is responsible for supporting and stabilizing the machine's superstructure, such as the part that suspends the spindle and table. The column is usually designed to ensure rigidity and stability so that it can maintain accuracy during high-speed milling.

2. Base:

The base is the basic structure of the CNC milling machine, which is usually located on the ground to bear the weight and vibration of the whole machine. The base must be stable and rigid enough to ensure that the machine does not deform or vibrate during operation.

3. Knee:

The knee is a movable part of the CNC milling machine that connects the column to the table. The lifting and lowering motion of the knee can be controlled by the CNC system, thus realizing the movement of the milling tool in the vertical direction to adjust the milling depth.

4. Power feeding mechanism:

The power feed mechanism consists of a variety of electric motors, ball screws, guide rails, and gear systems used to control the motion of various components on the milling machine. These components work in tandem to allow the table and tool to move horizontally and vertically to accomplish the milling operation.

5. Workbench:

The work table is the work platform of the milling machine and is usually located above the knees. The table can be moved horizontally to position the workpiece and support it for milling operations. It usually has T-slots for clamping and securing the workpiece.

6. ram:

The ram is the part that connects the table to the column and it can be moved in the lateral direction to adjust the position of the table. This allows the table to be precisely positioned along the X-axis on the milling machine.

7. Spindle:

The spindle is the core component of a CNC milling machine and is responsible for rotating the milling cutter and transmitting the cutting force to the workpiece. The spindle usually has high speed and power to accommodate different types of cutting tasks. It can also perform elevating and lowering motions to change the depth of feed of the tool.

8. Milling cutter:

A milling cutter is a tool used to cut a workpiece and usually has multiple teeth. Different types of milling cutters can be used for different milling operations such as face milling, slot milling and contour milling.

9. Milling collets:

Milling collets are used to clamp and hold milling cutters. They must be able to provide sufficient clamping force to ensure that the cutter does not loosen or deflect at high speeds.

10. CNC controller:

The brain of a CNC milling machine is the CNC controller, which usually consists of a computer numerical control (CNC) system. The CNC controller receives a program input from the user and then performs the milling operation by controlling the power feed mechanism and spindle. The operator can program the milling machine using a computer interface to control parameters such as the machining path, cutting speed and feed rate.

11. Cantilever:

Some CNC milling machines have a cantilever, which is a component that extends near the spindle to support tool cutter attachments such as coolant supply systems or measurement sensors.

12. mandrel support for horizontal milling machines:

Horizontal milling machine is a special type of milling machine which has a horizontally arranged spindle. A mandrel holder is a device used to support and position the workpiece and is usually used on horizontal milling machines.

Basic Principle of CNC Milling Machine

A CNC milling machine is controlled by a computer numerical control (CNC) system, which means that the operator can use computer programming to specify the desired cutting path, depth of cut, speed of cut, and other parameters on the workpiece. the CNC system translates these commands into motion-control signals to accurately control the movement of the milling machine's various components.

Tool selection and clamping

First, the operator needs to select the appropriate milling cutter, which depends on the material and shape of the workpiece and the desired cutting operation. Milling cutters usually have multiple teeth that can rotate at high speeds and cut the material. Selecting the proper cutter is a critical step in ensuring quality and efficiency in machining.

Once the tool is selected, it must be properly clamped in the milling chuck or shank to ensure a safe and consistent cutting operation. The clamping force must be high enough to prevent the tool from loosening during high-speed rotation.

Workpiece clamping

Workpiece clamping is another critical step. The table usually has a T-slot for clamping the workpiece or fixture. The operator must ensure that the workpiece is securely clamped to prevent it from moving or shifting during the cutting process.

Coordinate System

CNC milling machines use a coordinate system to determine the position of the tool and the workpiece. Typically, a milling machine has three axes: X, Y, and Z. These axes correspond to the movement of the tool in the horizontal, vertical, and feed directions, respectively, and the CNC system directs the movement of the tool by controlling the movement of these axes.

CNC Programming

Before machining can begin, the operator must write or generate a CNC program. This program consists of a series of instructions that tell the CNC milling machine how to move the tool to cut the workpiece.CNC programs are usually written in a specific programming language, such as G-code.

Workflow

Once the CNC program is ready and uploaded to the CNC milling machine's controller, the workflow is as follows:

a. Starting the CNC milling machine

The operator first starts the CNC milling machine and confirms that all safety settings and emergency stop functions are functioning properly.

b. Zeroing

The CNC milling machine needs to know the starting position of the tool and workpiece. Typically, before each job, the tool needs to return to a known starting position, which is referred to as "zeroing".

c. Machining

Once the zero return is complete, the CNC milling machine starts cutting the workpiece according to the instructions in the CNC program. the CNC controller precisely controls the position of the tool and the depth of cut by controlling the motion of each axis. the relative motion of the table and the tool allows the workpiece to be machined in the same manner as the tool. The relative motion of the table and the tool makes the cutting operation possible.

d. Cutting parameter control

During machining, the CNC system controls the cutting parameters such as cutting speed, feed rate and depth of cut. The selection of these parameters depends on the workpiece material and cutting requirements.

e. Monitoring and adjustment

Operators usually monitor the cutting process to ensure that everything is in order. If needed, they can make fine adjustments to the cutting results, such as adjusting the cutting speed or changing tools.

f. Finish machining

Once the cutting task is complete, the CNC milling machine stops the tool movement. The workpiece can be removed and inspected to ensure quality requirements are met.

Accuracy and surface quality

CNC milling machines are known for their high accuracy and excellent surface quality. the CNC system is able to accurately control the position of the tool, making the cutting process very precise. This is essential for manufacturing precision parts, which require highly accurate dimensions and surface smoothness.

Areas of application

CNC milling machines are used in a wide range of manufacturing applications, including aerospace, automotive, medical devices, electronics, and mold making. They are capable of machining a wide range of workpieces of different shapes and sizes, from small parts to large structures.

Technical Operation of Milling Machines

The technical operation of a milling machine is a highly complex and precise task that requires the operator to have in-depth machining knowledge and skills.

1. Preparation

Before performing the technical operation of a milling machine, some necessary preparations are required to ensure that everything goes smoothly.

a. Safety check

Ensure that the emergency stop button and other safety devices of the milling machine are functioning properly.

Check that the tools and fixtures are properly installed and that the clamping force is sufficient.Check that the cutting lubrication system is working properly to ensure that the tool and workpiece are lubricated during the cutting process.Check that the starting positions of the table and tool are correct.

b. Material and tool preparation

Prepare the workpiece to be machined and make sure its surface is smooth and clean.

Select suitable cutting tools, according to the material and cutting requirements of the workpiece.Mount and adjust the tool to ensure that the cutting tool is in the correct position.

c. CNC Program Preparation

Check and load the proper CNC program which contains the cutting path, cutting speed, feed rate and other necessary parameters.

Verify the correctness of the CNC program to ensure that it meets the workpiece requirements and tool specifications.Set the workpiece coordinates and workpiece start point on the CNC controller to ensure accurate tool positioning during the cutting process.

2. Operation Steps

Once the preparations have been completed, the operator can begin the technical operation of the milling machine. The following are general operating steps:

a. Start the milling machine

Turn on the main power to the milling machine and ensure that all electrical systems are functioning properly.

Start the CNC controller and enter the password or authenticate (if required).Load and select the CNC program to be run on the CNC controller.

b. Zero Return Operation

Use the Zero Back command in the CNC program to move the tool and workpiece to a known starting position.

After the zero return operation is complete, make sure the tool and workpiece are not colliding or interfering.

c. Setting Workpiece Coordinates

Use the coordinate system on the CNC controller to set the workpiece coordinates, including the X, Y, and Z axis positions.

Make sure the workpiece coordinates match the actual workpiece position.

d. Cutting Operation

Start the cutting operation, the CNC controller will control the movement of the tool and the workpiece according to the instructions in the program.

Monitor the cutting process to ensure that the tool is cutting the workpiece on the correct path.Adjust the cutting speed, feed rate and depth of cut as required.

e. Periodic Measurement and Inspection

Regularly use measuring tools to check dimensions and surface quality of workpieces.

If dimensional deviations or unsatisfactory surfaces are found, adjust cutting parameters or tools as needed.

f. End of Cutting

When the cutting operation is complete, close the cutting program.

Move the tool to a safe position for tool change or workpiece removal.Turn off the milling machine and disconnect the main power supply.

3. Safety Precautions

Milling machine operation requires a high degree of vigilance and adherence to strict safety regulations to prevent accidents. The following are some key safety precautions:

Wear personal protective equipment (PPE): including safety glasses, earplugs (if noisy), protective clothing and gloves.

Follow safety regulations: Strictly follow safety regulations and standard operating procedures for milling machine operations.

Regular maintenance: Check the maintenance of the milling machine regularly to ensure that all components are in good condition.

Avoid interference: Make sure there is no collision or interference between the tool and the workpiece.

Use caution when changing tools: Never change tools while running. Make sure that the tool has completely stopped rotating.

Dispose of waste: Dispose of chips and scrap properly to prevent clogging the machine or creating a hazard.

Types of Milling Machines

Milling machines are a common type of metalworking machine and there are several different types, each suited to specific machining needs and workpiece types.

Vertical Milling Machine (VM):

Vertical Milling Machines have a spindle that is perpendicular to the table and a tool that moves in a vertical direction.

It is suitable for machining workpieces of various sizes, including flat milling, grooving and contour milling.Commonly used in general metal processing and mold making.

Horizontal Milling Machine:

Horizontal Milling Machine has spindle arranged horizontally and the tool moves horizontally.

It is suitable for the machining of large workpieces, such as large castings and bearing housings.

It can carry out efficient cutting and is suitable for mass production.

CNC Milling Machine:

CNC Milling Machine is a kind of milling machine equipped with computer numerical control (CNC) system, which can be programmed to automatically control the movement of tools and workpieces.

With high precision, high productivity and versatility, it is suitable for the processing of various complex workpieces.

CNC milling machines can be of vertical, horizontal or gantry type.

Bed Milling Machine:

Bed Milling Machine has a large bed to support the table and workpiece.

Ideal for machining large workpieces such as aerospace parts and heavy mechanical components.

Can handle high cutting forces and high rigidity requirements.

Gantry Milling Machine:

Gantry Milling Machines have a large gantry structure for supporting the table and spindle.

It is suitable for machining large workpieces and high precision requirements, such as aero-engine parts and ship components.

Has a large working area and high rigidity.

Vertical Machining Center (VMC):

Vertical Machining Center is a highly automated CNC milling machine, usually with an automatic tool change system and a rotary table.

It is used to produce complex parts such as automotive components, aerospace parts and medical device components.

Horizontal Machining Center (HMC):

Horizontal machining centers have horizontally aligned spindles for horizontal machining operations.

Used for efficient machining of complex workpieces such as automotive engine parts, turbine blades, etc.

Add-on Machining Center (5-Axis Machining Center):

An add-on machining center can move in five different axes, allowing cutting on complex curved surfaces.

It is suitable for producing high-precision parts in the aerospace, medical and space fields.

CNC milling machines play an important role in the manufacturing industry by serving as a high-precision metalworking tool for a variety of different types of milling operations. With precise CNC control, CNC milling machines can produce complex parts and components, providing an indispensable capability for modern engineering and manufacturing.