Tool selection and parameter optimization in turning parts processing
Turning parts processing is one of the most common and widely used processing methods in the field of mechanical manufacturing. It uses a turning tool to cut the rotating workpiece to obtain the required shape, size and surface quality.
The quality and efficiency of turning processing directly affect the performance and cost of the product, and tool selection and parameter optimization are the key factors that determine the turning processing effect. This article will deeply explore the tool selection, parameter optimization and application of computer-aided manufacturing (CAM) software in turning parts processing, in order to provide readers with valuable reference.
1. Tool selection in turning parts processing
(1) Tool material
The material of the turning tool directly affects the cutting performance and service life of the tool. Commonly used turning tool materials include:
1) High-speed steel (HSS):
It has high hardness, wear resistance and toughness, and is suitable for processing ordinary steel, cast iron and other materials.
2) Cemented carbide:
It has extremely high hardness and wear resistance, but poor toughness, and is suitable for processing difficult-to-process materials such as high-strength steel, stainless steel, and heat-resistant alloys.
3) Ceramics:
It has extremely high hardness and heat resistance, but is relatively brittle. It is suitable for high-speed finishing of cast iron, hardened steel and other materials.
4) Cubic boron nitride (CBN):
It has a hardness second only to diamond, has extremely high wear resistance and thermal stability, and is suitable for machining hardened steel, high-temperature alloys and other difficult-to-machine materials.
5) Diamond:
It has the highest hardness and wear resistance, but is expensive. It is suitable for machining non-ferrous metals, non-metallic materials, etc.
(2) Tool geometry parameters
The geometric parameters of turning tools include rake angle, back angle, main rake angle, secondary rake angle, etc. These parameters directly affect cutting force, cutting temperature, surface quality, etc.
1) Rake angle:
It affects the sharpness of the cutting edge and the size of the cutting force. A larger rake angle can reduce the cutting force, but it will reduce the tool strength.
2) Back angle:
It affects the friction between the back face of the tool and the surface of the workpiece. A larger back angle can reduce friction, but it will reduce the tool strength.
3) Main rake angle:
Affects the direction of cutting force and the flow direction of chips. A larger main rake angle can reduce radial force but increase axial force.
4) Secondary rake angle:
Affects the quality of the machined surface and the heat dissipation of the tool. A larger secondary rake angle can reduce the roughness of the machined surface but reduce the strength of the tool.
Reasonable tool geometry parameters can improve machining efficiency, improve machining quality and extend tool life.
(3) Tool coating
Tool coating can significantly improve the wear resistance, heat resistance and lubricity of the tool, thereby improving machining efficiency and extending tool life. Commonly used tool coatings include:
1) TiN (titanium nitride):
It has high hardness and wear resistance and is suitable for machining ordinary steel, cast iron and other materials.
2) TiCN (titanium carbonitride):
It has higher hardness and wear resistance than TiN and is suitable for machining high-strength steel, stainless steel and other materials.
3) Al2O3 (aluminum oxide):
It has extremely high hardness and heat resistance, and is suitable for high-speed machining of cast iron, hardened steel and other materials.
2. Tool selection for machining different types of turned parts
(1) External turning:
External turning requires high rigidity and wear resistance of the tool, and usually selects tools with a larger main rake angle, such as 90° external turning tools, 75° external turning tools, etc.
(2) Internal turning:
Internal turning requires high tool size and chip removal performance, and usually selects tools with thinner tool bars and larger chip removal grooves, such as internal turning tools, boring tools, etc.
(3) Face turning:
Face turning requires high tool strength and impact resistance, and usually selects tools with a smaller main rake angle, such as 45° face turning tools, 60° face turning tools, etc.
3. Parameter setting and optimization when turning parts
(1) Cutting speed
Cutting speed refers to the instantaneous speed of a selected point on the cutting edge relative to the main motion of the workpiece, and is usually expressed by the length of the workpiece surface that the cutting edge passes through per unit time (in m/min).
1) Impact analysis:
● Processing efficiency:
Increasing the cutting speed can shorten the processing time of a single piece and significantly improve production efficiency.
● Processing quality:
Higher cutting speeds help reduce cutting forces and surface roughness, thereby improving processing quality.
● Tool life:
Excessive cutting speeds will increase tool wear, shorten tool life, and increase processing costs.
2) Selection basis:
● Workpiece material:
Different materials have different cutting speed ranges. For example, the cutting speed of aluminum alloy is usually higher than that of stainless steel.
● Tool material:
The allowable cutting speed of carbide tools is higher than that of high-speed steel tools.
● Processing requirements:
Roughing can choose a higher cutting speed to improve efficiency, while finishing needs to appropriately reduce the speed to ensure surface quality.
(2) Feed rate
The feed rate refers to the displacement of the tool relative to the workpiece in the feed direction, usually expressed as the feed distance per revolution or per minute (in mm/r or mm/min).
1) Impact analysis:
● Processing efficiency:
Increasing the feed rate can shorten the processing time, but too high a feed rate may cause a sharp increase in cutting force.
● Processing quality:
Excessive feed rate may increase surface roughness and affect the dimensional accuracy and surface finish of the workpiece.
● Tool life:
Exessive feed rate will aggravate tool wear, especially when processing hard materials.
2) Selection basis:
● Workpiece material:
Soft materials (such as aluminum alloys) can use a larger feed rate, while hard materials (such as hardened steel) need to use a smaller feed rate.
● Tool geometry parameters:
The edge strength and chip removal ability of the tool will affect the selection of feed rate.
● Processing stage:
Roughing can use a larger feed rate to improve efficiency, while fine processing requires a smaller feed rate to ensure surface quality.
(3) Cutting depth
The cutting depth refers to the vertical distance between the surface to be machined and the machined surface (in mm). The choice of cutting depth directly affects the machining efficiency, cutting force and tool life.
1) Impact analysis:
● Machining efficiency:
Increasing the cutting depth can reduce the number of machining times and significantly improve efficiency.
● Machining quality:
Excessive cutting depth will increase the cutting force, which may cause vibration and deformation, affecting the machining accuracy.
● Tool life:
Excessive cutting depth will aggravate tool wear, especially when machining hard materials.
2) Selection basis:
● Workpiece material:
Soft materials can use a larger cutting depth, while hard materials need to reduce the cutting depth.
● Machine tool rigidity:
Machine tools with better rigidity can withstand a larger cutting depth.
● Machining stage:
Rough machining can use a larger cutting depth to quickly remove the excess, while fine machining needs to reduce the cutting depth to ensure accuracy.
4. Comprehensive optimization of cutting parameters for turned parts
In the actual processing of turned parts, cutting speed, feed rate and cutting depth need to be considered comprehensively to achieve the best processing effect. The following table lists the recommended range of cutting parameters for some common materials. These parameters are based on empirical values under general processing conditions and need to be adjusted according to specific needs in actual applications.
5. Application of computer-aided manufacturing (CAM) software in turning parts processing
(1) Tool path planning
CAM software can generate efficient tool paths based on part models and processing requirements. Common tool path strategies include:
1) Contour processing:
Features: The tool cuts along the contour of the part and removes material layer by layer.
Advantages: Suitable for processing complex curved parts and can obtain higher surface quality.
Disadvantages: Long processing time and complex tool path.
2) Spiral processing:
Features: The tool cuts along the spiral trajectory and is suitable for deep hole processing.
Advantages: It can improve processing efficiency and reduce tool wear.
Disadvantages: Not suitable for all types of parts.
3) Profiling:
Features: The tool cuts along the contour of the part, which is suitable for machining parts with regular shapes.
Advantages: The machining path is simple and the efficiency is high.
Disadvantages: Not suitable for parts with complex curved surfaces.
4) Radial machining:
Features: The tool cuts along the radial direction, which is suitable for machining circular or annular parts.
Advantages: High machining efficiency and good surface quality.
Disadvantages: Not suitable for non-circular parts.
(2) Parameter optimization
CAM software can automatically optimize cutting parameters such as cutting speed, feed rate, cutting depth, etc. according to the tool, workpiece material and machining requirements. This can significantly improve the machining efficiency of turned parts and reduce machining costs.
6. Conclusion
In short, tool selection and parameter optimization are key technologies that cannot be ignored in turning parts machining. Through scientific methods and advanced technical means, it can significantly improve machining efficiency and ensure product quality.
Comments
Post a Comment