Engineering Efficient Workholding for CNC Machining Processes
To meet the high demands for workpiece clamping and holding capabilities in modern precision manufacturing, a new clamping fixture has been developed. The structure and operating principle of this fixture are described in detail. With its sophisticated design, the fixture achieves efficient and stable clamping of workpieces. It addresses the shortcomings of traditional clamping fixtures by enhancing clamping force stability and resetting accuracy. Additionally, its integrated design improves compactness and durability.
01 Introduction
In modern precision manufacturing, particularly in high-precision micromachining operations like grinding tiny bars, the capabilities for clamping and holding workpieces have a direct impact on machining accuracy and production efficiency. Traditional clamping fixtures have several shortcomings, including uneven and unstable clamping force and poor resetting accuracy, rendering them inadequate for the demands of contemporary precision manufacturing.
The small-diameter tool illustrated in Figure 1 is typically made from high-speed steel or carbide. Its cutting edge has a very small diameter, ranging from 0.05 to 1.0 mm, and can measure up to 20 mm in length. This design necessitates the grinding of both the primary and secondary cutting faces at the tool tip. In practical applications, collets are commonly used to secure the shank of small-diameter tools. However, due to the small diameter and length of the tool shank, achieving a uniform and stable clamping force is challenging. This instability can lead to tool tilting, deformation, damage, or even breakage during machining, which significantly affects machining quality and efficiency.
Therefore, it is crucial to design a new clamping fixture that can greatly enhance workpiece clamping and holding capabilities.
The main technical problems that need to be solved are as follows.
(1) Uniformity and stability of clamping force
Traditional clamping fixtures frequently encounter issues with uneven distribution of clamping force and unstable clamping pressure. This can result in the workpiece becoming deformed or misaligned during processing. Therefore, the primary technical challenge is to ensure a uniform distribution and stable control of clamping forces on both the left and right sides during the clamping process. This is essential to prevent deformation or offset of the workpiece.
(2) Reset accuracy
The reset accuracy of a fixture significantly impacts the processing accuracy of the workpiece. Traditional fixtures have relatively simple reset mechanisms, making it challenging to achieve high precision in resetting. Designing an effective clamping structure and transmission mechanism to ensure the fixture’s reset accuracy during use is crucial for improving processing quality.
(3) Adaptability
When designing clamping mechanisms, it’s essential to account for the varying requirements of workpieces with different specifications. The clamping system should demonstrate versatility and adjustability to ensure stable clamping for various workpiece types. Optimizing the structural design is a key factor in achieving this stability.
02 Clamping and Holding Fixture Structural Design
To address the issues mentioned previously, our company has developed a new clamping and holding fixture specifically designed for small-diameter tools. This fixture is installed on our DTMA1200 micro four-station grinding machine and works by securely clamping the tool shank while assisting with the collet’s grip. Thanks to its advanced structural design and optimized transmission mechanism, the fixture provides stable and reliable clamping of the workpiece.
The clamping fixture is illustrated in Figure 2, the actual fixture can be seen in Figure 3, the 2D depiction is shown in Figure 4, and the 3D visualization is available in Figure 5.
2.1 Design of key components
The clamping and holding fixture is mainly composed of four key parts: the mounting part, the first clamping arm part, the second clamping arm part and the driving plate part. The components are connected through precise mechanical design and ingenious connection methods to achieve efficient clamping and holding functions.
(1) Design of mounting part
The mounting part is the base of the entire fixture. The structure is stable and can withstand various forces during the processing. The mounting part is provided with precise mounting surfaces and positioning holes for the precise installation and positioning of the first clamping arm part and the second clamping arm part, as well as the driving plate CNC aluminum milling part and other necessary accessories.
(2) Design of the first clamping arm part and the second clamping arm part
The first clamping arm part and the second clamping arm part are the core clamping parts of the fixture. They are located on both sides of the mounting part and are connected to the mounting part through elastic connection. Each clamping arm part consists of a front end and a rear end. The front end is used to install the clamping claw or fixture to directly contact the workpiece, and the rear end is connected to the driving plate part. The opening and closing movement of the clamping arm part is realized by the deformation of the driving plate part. Specifically, the first clamping arm portion includes a first front end and a first rear end, and the second clamping arm portion includes a second front end and a second rear end. The first clamping arm portion and the second clamping arm portion are elastically connected to the mounting portion through their respective elastic arms (first elastic arm and second elastic arm). This design enables the clamping arm portion to undergo elastic deformation when driven, thereby better matching the shape and size of the workpiece and achieving a tighter clamping.
(3) Design of the driving plate portion
The driving plate portion is a key component connecting the first clamping arm portion and the second clamping arm portion. It controls the opening and closing of the two clamping arms through elastic deformation. When the driving device (such as a cylinder, an electric motor, etc.) drives the driving plate portion, the driving plate portion undergoes elastic deformation, pushing the first clamping arm portion and the second clamping arm portion to move toward or away from each other, thereby achieving the clamping or loosening of the workpiece. The design of the driving plate portion fully considers the stability and deformation capacity of the structure. Through the fine hollow seam group design (first hollow seam group and second hollow seam group), the deformation capacity is improved without affecting the overall strength, making the clamping force more uniform and adjustable.
2.2 Structure and Detail
Design In order to further improve the performance of the clamping fixture, a number of structural and detail designs are incorporated here.
(1) Elastic arm design
The width of the first and second elastic arms is carefully controlled between 0.05 mm and 0.5 mm, depending on the clamping force required for the workpiece. This precise measurement ensures that the arms can deform adequately while maintaining structural stability. Additionally, the number of elastic arms can be adjusted based on actual requirements. In this design, a minimum of two elastic arms are incorporated to enhance the uniformity and reliability of the clamping mechanism.
(2) Hollow seam group design
By incorporating a fine hollow seam group between the mounting part and the clamping arm, we can reduce overall mass while simultaneously enhancing deformation efficiency and accuracy. The design of the hollow seam group—whether symmetrical or asymmetrical—can be adjusted flexibly based on the shape and size of the workpiece being clamped, ensuring optimal clamping performance.
(3) Positioning and adjustment mechanism
The design incorporates positioning grooves and adjustable components to ensure precise positioning and stable power transmission during operation. Additionally, the introduction of an adjustment mechanism allows for the fine-tuning of the clamping position and force according to specific needs, which further enhances the adaptability and flexibility of the fixture.
(4) Integrated design and forming
The key components, including the mounting part, the first clamping arm, the second clamping arm, and the drive plate, utilize an integrated design concept. These parts are cut and formed from a metal plate that has elastic deformation capabilities. This approach minimizes fitting clearance and reduces looseness between the components, thereby enhancing the compactness, stability, and precision of the overall structure.
2.3 Structural design features
(1) Stable and reliable clamping force
The innovative design of the elastic arm and the drive plate allows this clamping fixture to maintain a stable and reliable clamping force under the operation of the drive device. The clamping force is sustained not only by the drive device but also by the deformation of the drive plate and the elastic arm. Even when the drive device experiences minor stroke errors, the drive plate and elastic arm do not undergo significant deformation, allowing the clamping force to remain relatively stable. This design effectively prevents the large fluctuations in clamping force that are often seen in traditional clamping fixtures due to stroke errors.
(2) Strong adaptability
The structural design of this fixture takes into account the clamping requirements for CNC lathe turning workpieces of various shapes and sizes. By adjusting the number, width, and arrangement of the hollow seam groups of elastic arms, as well as other parameters, the fixture can effectively address the clamping challenges posed by complex workpieces. Additionally, the incorporation of a positioning and adjustment mechanism has significantly improved the fixture’s adaptability and flexibility.
(3) Good reset accuracy
The accuracy of resetting the fixture has a direct impact on the processing accuracy of the workpiece. This design ensures precise resetting of the clamping arm through an advanced structural design and elastic components, which significantly enhances the resetting accuracy.
(4) Compact and durable structure
The application of integrated design concept makes the entire fixture structure more compact and durable. Key components are made of high-strength materials and their wear resistance and corrosion resistance are enhanced through surface treatment technology, effectively extending the service life of the fixture.
(5) Easy to operate
This clamping fixture is designed for easier and faster operation. Its elastic connection and integrated design allow for smoother and more labor-saving clamping and releasing of the workpiece. Additionally, the adjustment mechanism makes it more intuitive and straightforward to adjust the clamping position and force.
03 Working principle of the clamping and holding fixture
In the clamping and holding fixture’s operation, the first and second clamping arms move relative to each other due to the controlled elastic deformation of the driving plate. This movement facilitates the clamping and releasing of the workpiece. The specific working process is outlined as follows.
(1) Initial state
In the initial state, the driving plate is not subjected to any external forces and remains in its natural position. At this point, the first and second clamping arms, aided by their respective elastic components, are naturally opened to a specific angle, creating an opening gap for the placement of the workpiece. The mounting part securely supports the entire fixture, ensuring its stability throughout the working process.
(2) Workpiece placement and clamping
Once the workpiece is positioned in the “gap” between the first and second clamping arms, the driving device is activated. This action causes the driving plate to experience external force and undergo elastic deformation. As the plate deforms, it pushes the rear ends of both the first and second clamping arms closer together. Because the clamping arms are connected to the mounting portion via an elastic arm, this movement causes the front ends of the clamping arms to also move inward, effectively clamping the aluminum stamping parts.
At this point, the extent of the driving plate’s deformation directly influences the clamping force applied by the clamping arms. By precisely controlling the output force of the driving device, the clamping force can be adjusted accurately to meet the requirements for various workpieces and processing tasks.
(3) Clamping and retention during processing
The fixture provides a stable and reliable clamping force for the workpiece during processing, thanks to the combined clamping action of the elastic arm and the drive plate. Even if vibrations or impacts occur during processing, or if the drive device experiences slight stroke errors, the clamping force remains largely unchanged. This stability is due to the fault tolerance provided by the elastic deformation of both the drive plate and the elastic arm. As a result, the clamping force stays consistent, effectively preventing the workpiece from shifting or deforming under uneven pressure, and ensuring the workpiece’s stability throughout the processing.
(4) Workpiece release and reset
Once the processing is complete, the drive device begins to reverse, allowing the drive plate to gradually return to its original state. As the drive plate recovers from its deformation, the first and second clamping arms slowly open, releasing their grip on the workpiece. The workpiece can then be easily removed with the help of the robot. After the workpiece is released, the clamping arms automatically return to their initial open position, powered by elastic arms, thus preparing for the next clamping operation.
04 Conclusion
This fixture boasts a sophisticated design that effectively addresses the issues of uneven clamping force, unstable clamping force, and poor reset accuracy commonly found in traditional clamping fixtures. As a result, it significantly enhances clamping and holding capabilities. The precise coordination between the elastic arms and the drive plate guarantees a stable clamping force, even in the presence of minor errors in the drive mechanism’s stroke, thereby ensuring machining accuracy and product quality for the workpiece.
Additionally, this fixture demonstrates excellent adaptability. By adjusting parameters such as the number and width of the elastic arms and the arrangement of the hollow slot groups, it can flexibly accommodate workpieces of various shapes and sizes. This versatility greatly enhances the fixture’s adjustability. The sophisticated structural design, along with the incorporation of elastic reset components, ensures accurate resetting, further improving stability and reliability during machining processes.
In practical applications, tests have shown that when using this clamping and holding fixture, small-diameter tools achieve a repeatable positioning accuracy of ±0.002 mm, with a grinding yield exceeding 99.2%.
Currently, this fixture is widely utilized in our company and by related client companies, effectively solving technical challenges in areas such as the clamping of tiny bars. It provides reliable technical support for the precision manufacturing sector and contributes to significant economic and social benefits.
If you want to know more or inquiry, please feel free to contact info@anebon.com
At Anebon, we believe in the values of innovation, excellence, and reliability. These principles are the foundation of our success as a mid-sized business that provides CNC custom machining components, metal stamping products, and high pressure aluminum die casting parts for various industries such as non-standard devices, medical, electronics, auto accessories, and camera lenses.