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How does the drawing machine calculate the drawing allowance？
Category：answer Publishing time：2025-10-11 11:45:37 Browse： Times
In the field of mechanical processing, drawing is an efficient and precise processing method, widely used in the processing of various internal surfaces, such as keyways, splines, rectangular slots, etc. The reasonable calculation of the drawing allowance is one of the key factors to ensure the quality and efficiency of the drawing process. This article will introduce in detail how to scientifically calculate the drawing allowance during the drawing process.
What is the drawing allowance?
The drawing allowance refers to the thickness of the metal layer reserved for the cutting edge of the drawing tool before the drawing operation. It is the reserved amount for the pre-processing hole or surface of the workpiece before the drawing process, which directly affects the design of the drawing tool, the size of the drawing force, and the quality of the processed surface.
2. Influencing factors of the allowance for broaching
1. Material properties: different materials have different machinability, and plastic materials (such as low-carbon steel) require a larger broaching allowance to avoid excessive broach wear.
2. Processing accuracy of the initial hole: the more precise the preliminary processing hole, the smaller the broaching allowance can be appropriately reduced; if the preliminary hole error is large, a larger allowance needs to be reserved.
3. Broaching method: broaching can be divided into internal broaching and external broaching, and different broaching forms have different requirements for the allowance.
4. Broach structure: the cutting capacity of integral broaches and assembled broaches is different, and the requirements for the allowance are also different.
5. Requirements for processing accuracy and surface roughness: the higher the accuracy requirements, the more precise the control of the allowance should be.
3. Methods for determining the allowance for broaching
# 1. Empirical formula method
In actual production, empirical formulas are usually used to estimate the allowance for broaching:
- For broaching circular preliminary holes into rectangular holes or keyways:
[
A = D - d
]
Among them, A is half of the broaching allowance, D is the final broaching size, and d is the diameter of the preliminary hole.
- For internal surface broaching, the allowance is generally controlled between 0.1 to 0.3 mm; for external broaching, it may be around 0.2 to 0.5 mm.
# 2. Table lookup method
According to parameters such as processing material, broaching type, and broach type, refer to the recommended allowance table in the machinery processing manual to determine the allowance value. For example, the 'Metal Cutting Manual' provides standard broaching allowance ranges for different materials.
# 3. Trial cutting method
For broaching operations with high precision or special materials, the allowance can be gradually adjusted in the trial cutting to find the optimal value. Although this method is more expensive, it can effectively improve processing accuracy and tool life.
4. Principles of allowance distribution for broaching
1. Uniformity principle: ensure uniform distribution of allowance to avoid excessive local load causing broach breakage or workpiece deformation.
2. Phased principle: the allowance for rough cutting, fine cutting, and calibration should be reasonably distributed, usually accounting for 70% to 80% of the rough cutting part, and 20% to 30% of the fine cutting part.
3. Consideration of tool life: excessive allowance will increase broaching force and tool wear, affecting processing efficiency.
5. Summary
The allowance for broaching is an important parameter that cannot be ignored in broaching processing. Accurate calculation and reasonable allocation of the allowance for broaching can not only improve processing efficiency and surface quality, but also extend the service life of the broach and reduce production costs. Therefore, in actual operation, engineering technicians should determine the allowance for broaching scientifically and reasonably according to specific working conditions, combining experience formulas, standard tables, and actual tests, in order to achieve the goal of high-efficiency and high-precision broaching processing.
Through the above analysis, we can see that the allowance for broaching is not only a simple setting of technical parameters, but also an important embodiment of process optimization. Only by fully considering various factors such as materials, processes, and equipment can we truly achieve high efficiency and accuracy in broaching processing.
In the field of mechanical processing, drawing is an efficient and precise processing method, widely used in the processing of various internal surfaces, such as keyways, splines, rectangular slots, etc. The reasonable calculation of the drawing allowance is one of the key factors to ensure the quality and efficiency of the drawing process. This article will introduce in detail how to scientifically calculate the drawing allowance during the drawing process.
What is the drawing allowance?
The drawing allowance refers to the thickness of the metal layer reserved for the cutting edge of the drawing tool before the drawing operation. It is the reserved amount for the pre-processing hole or surface of the workpiece before the drawing process, which directly affects the design of the drawing tool, the size of the drawing force, and the quality of the processed surface.
2. Influencing factors of the allowance for broaching
1. Material properties: different materials have different machinability, and plastic materials (such as low-carbon steel) require a larger broaching allowance to avoid excessive broach wear.
2. Processing accuracy of the initial hole: the more precise the preliminary processing hole, the smaller the broaching allowance can be appropriately reduced; if the preliminary hole error is large, a larger allowance needs to be reserved.
3. Broaching method: broaching can be divided into internal broaching and external broaching, and different broaching forms have different requirements for the allowance.
4. Broach structure: the cutting capacity of integral broaches and assembled broaches is different, and the requirements for the allowance are also different.
5. Requirements for processing accuracy and surface roughness: the higher the accuracy requirements, the more precise the control of the allowance should be.
3. Methods for determining the allowance for broaching
# 1. Empirical formula method
In actual production, empirical formulas are usually used to estimate the allowance for broaching:
- For broaching circular preliminary holes into rectangular holes or keyways:
[
A = D - d
]
Among them, A is half of the broaching allowance, D is the final broaching size, and d is the diameter of the preliminary hole.
- For internal surface broaching, the allowance is generally controlled between 0.1 to 0.3 mm; for external broaching, it may be around 0.2 to 0.5 mm.
# 2. Table lookup method
According to parameters such as processing material, broaching type, and broach type, refer to the recommended allowance table in the machinery processing manual to determine the allowance value. For example, the 'Metal Cutting Manual' provides standard broaching allowance ranges for different materials.
# 3. Trial cutting method
For broaching operations with high precision or special materials, the allowance can be gradually adjusted in the trial cutting to find the optimal value. Although this method is more expensive, it can effectively improve processing accuracy and tool life.
4. Principles of allowance distribution for broaching
1. Uniformity principle: ensure uniform distribution of allowance to avoid excessive local load causing broach breakage or workpiece deformation.
2. Phased principle: the allowance for rough cutting, fine cutting, and calibration should be reasonably distributed, usually accounting for 70% to 80% of the rough cutting part, and 20% to 30% of the fine cutting part.
3. Consideration of tool life: excessive allowance will increase broaching force and tool wear, affecting processing efficiency.
5. Summary
The allowance for broaching is an important parameter that cannot be ignored in broaching processing. Accurate calculation and reasonable allocation of the allowance for broaching can not only improve processing efficiency and surface quality, but also extend the service life of the broach and reduce production costs. Therefore, in actual operation, engineering technicians should determine the allowance for broaching scientifically and reasonably according to specific working conditions, combining experience formulas, standard tables, and actual tests, in order to achieve the goal of high-efficiency and high-precision broaching processing.
Through the above analysis, we can see that the allowance for broaching is not only a simple setting of technical parameters, but also an important embodiment of process optimization. Only by fully considering various factors such as materials, processes, and equipment can we truly achieve high efficiency and accuracy in broaching processing.
