I have been doing machining for so long, what do I know about the machining process? Today I’m going to watch it again with you…
1. What are the three methods of clamping workpieces?
1. Tightening in the luminaire
2. Find the right pliers directly
3. Mark the line to find the correct pliers.
2. What are the components of the mechanical processing process?
Roughing, semi-finishing, finishing, superfinishing, etc.
3. How to classify benchmarks?
1. Design Basis
2. Process benchmark: process, measurement, assembly, positioning
4. What is included in the initial error that occurred during processing?
Caused by principle error, positioning error, setting error, tool error, mounting error, machine tool spindle rotation error, guide rail guide error machine tool, machine tool transmission error, process system stress deformation, process system thermal deformation, tool wear, measurement error and workpiece residual stress error.
5. How does process system rigidity impact machining accuracy?
1. Workpiece shape error caused by changes in the position of the cutting force application point
2. Processing errors caused by changes in cutting force
3. Processing errors caused by clamping force and gravity
4. The impact of transmission force and inertia force on processing accuracy
6. What do machine tool guide rail guiding error and spindle rotation error include?
1. The guide rail mainly includes the relative displacement error between the tool and the workpiece in the error-sensitive direction caused by the guide rail.
2. Spindle radial circular runout, axial circular runout and tilt oscillation.
7. Transmission error analysis of machine tool transmission chain? Measures to reduce transmission chain transmission errors?
Error analysis: It is measured by the rotation angle error Δφ of the end element of the transmission chain.
Measurements: 1. The fewer transmission chain parts, the shorter the transmission chain, the smaller Δφ and the higher the precision; 2. The smaller the gear ratio i, especially the small gear ratio at the first and last ends; 3. Since the end of parts transmission, the error of parts has the greatest impact, so it should be made as accurate as possible. 4. Use a correction device.
8. Which errors are variable-valued system errors?
Systematic error: (constant value system error, variable value system error) random error
Constant system error: processing error caused by processing principle error, manufacturing error of machine tools, tools, fixtures, stress deformation of process system, etc.
Variable value system error: Wear of tools, tools, fixtures, machine tools, etc. causes thermal deformation errors before thermal equilibrium.
Random errors: blank copy errors, positioning errors, clamping errors, multiple adjustment errors, deformation errors caused by residual stresses.
9. What are the ways to ensure and improve the accuracy of processing?
1. Error prevention technology: reasonable use of advanced processes and equipment to directly reduce original errors
2. Error compensation technology: online detection of even parts, automatic grinding and active control of decisive error factors
10. What are the physical and chemical properties of surface layer materials?
1. Cold hardening of surface layer metal; 2. Deformation of the metallographic structure of the surface layer metal; 3. Residual stress of the surface layer metal;
11. Try to analyze the factors that affect the surface roughness of cutting processing
The roughness value is determined by: the height of the residual cutting zone.
Main factors: tool tip arc radius, primary declination angle, secondary declination angle and feed amount.
Secondary factors: the cutting speed increases, the cutting fluid is selected appropriately, the cutting angle of the tool is increased appropriately, and the sharpening quality of the tool is improved.
12. Try to analyze the factors that affect the surface roughness of the grinding process?
Geometric factors: 1. The effect of grinding amount on surface roughness; 2. The effect of grinding wheel particle size and grinding wheel dressing on surface roughness.
Influence of physical factors: plastic deformation of the surface metal, amount of grinding and choice of grinding wheel.
13. What is grinding burn? What is grinding and extinguishing burns? What is grind anneal burn?
Quenching: If the temperature in the grinding zone does not exceed the phase transformation temperature of the quenched steel, but exceeds the transformation temperature of martensite, the martensite of the metal on the surface of the workpiece will be transformed into a structure quenched with lower hardness.
Quenching: If the temperature in the grinding zone exceeds the phase transformation temperature, coupled with the cooling effect of the coolant, the surface metal will have a secondary quenching martensite structure with hardness higher than that of martensite original in its lower layer; cooling A quenched structure with lower hardness than the original quenched martensite slowly appears.
Annealing: If the temperature in the grinding zone exceeds the phase transition temperature and there is no coolant during the grinding process, the surface metal will have an annealed structure and the metal hardness of surface will drop sharply.
14. Principles of selection of coarse data and fine data
Raw data: 1. The principle of guaranteeing mutual position requirements; 2. The principle of ensuring a reasonable distribution of the machining allowance on the machined surface; 3. The principle of facilitating the clamping of the workpiece; 4. The principle that raw data generally cannot be reused;
Precision data: 1. The principle of data coincidence; 2. The principle of unified data; 3. The principle of mutual data; 4. The principle of practical tightening;
15. What are the principles of organizing the process sequence?
1. Process the reference plane first, then process other surfaces; 2. Under normal circumstances, process the surface first, and then process 3. Process the main surface first, and then process the secondary surface 4. Arrange the rough machining process first, and then arrange the process of finishing.
16. How to divide the processing steps? What are the advantages of dividing the processing steps?
The division of processing steps: rough machining step, semi-finishing step, finishing step and precision finishing step can ensure sufficient time to eliminate thermal deformation and eliminate residual stress caused by rough machining, so as to improve the precision of subsequent processing. In addition, when defects in the blank are found during the rough machining stage, it is not necessary to proceed to the next processing stage to avoid waste. In addition, the equipment can also be used rationally, low precision machine tools are used for rough machining and precision machine tools are dedicated to finishing to maintain the precision level of the machines. precision tools, human resources can be reasonably organized and high technology; workers specialize in precision and ultra-precision machining, which is important to ensure product quality and process level improvement.
17. What are the technological ways to improve productivity?
1. Shorten the base time; 2. Reduce the overlap between auxiliary time and basic time; 3. Reduce work organization time; 4. Reduce preparation and production time;
18. What is the main content of the regulations on the assembly process?
1. Analyze the product drawing, divide the assembly units and determine the assembly method; 2. Develop the assembly sequence and divide the assembly processes; 3. Calculate the assembly time quota; 4. Determine technical assembly requirements, quality inspection methods and; inspection tools for each process; 5. Determine the method of transporting assembly parts as well as the equipment and tools required; 6. Select and design tools, accessories and special equipment required in the assembly process;
19. What should be considered in the machine structure assembly process?
1. The machine structure must be able to be divided into independent assembly units; 2. Reduce repairs and machining during assembly; 3. The machine structure should be easy to assemble and disassemble;
20. What problems should be paid attention to when searching for assembly dimension chains?
1. The assembly dimension chain should be simplified if necessary; 2. The assembly dimension chain consists of “one part and one link” 3. The “directionality” of the assembly dimension chain In the same assembly structure, there is assembly accuracy; in different positions and directions. Where necessary, dimensional chains should be assembled in different directions.
21. What are the components and functions of machine tool accessories?
The machine tool holder is a device for clamping the workpiece on the machine tool. Its function is to hold the workpiece in a correct position relative to the machine tool and the cutting tool, and to maintain this position during the machining process.
The components are: 1. Positioning components or devices; 2. Tool guiding components or devices; 3. Clamping components or devices; 5. Clamp body;
The main functions are: 1. Ensuring the quality of treatment; 2. Improve production efficiency; 3. Expand the scope of machine tool technology; 4. Reduce the labor intensity of workers and ensure production safety;
22. How are machine tool accessories classified based on their range of use?
1. Universal luminaire; 2. Special lighting; 3. Adjustable luminaire and group luminaire; 4. Combined luminaire and random luminaire.
23. What two aspects does positioning error include?
1. The positioning error caused by inaccurate production of the positioning surface of the workpiece or positioning components on the fixture is called datum position error.
2. The positioning error caused by the mismatch between the process data and the workpiece positioning data is called datum misalignment error.
24. What are the basic requirements for the design of workholding devices?
1. During the clamping process, the correct position obtained when positioning the workpiece must be maintained.
2. The clamping force should be appropriate. The clamping mechanism must be able to ensure that the workpiece does not loosen or vibrate during processing, and at the same time, it must avoid improper deformation and damage to the workpiece surface. should generally have a self-locking function.
3. The tightening device should be easy to use, economical and safe.
4. The complexity and automation of the clamping device must be compatible with the production batch and production method. The structural design should be simple and compact and use standardized components wherever possible.
25. What are the three elements used to determine the clamping force? What are the different principles?
1. The direction of the clamping force should achieve precise positioning of the workpiece without damaging the positioning. For this reason, it is generally required that the main clamping force points vertically toward the locating surface.
2. The direction of the clamping force should be consistent with the direction of the workpiece rigidity as much as possible to reduce the clamping deformation of the workpiece.
3. The direction of the clamping force should be as consistent as possible with the direction of the cutting force and the gravity of the workpiece to reduce the required clamping force.
Principle of selection of the point of application of the clamping force:
1. The point of application of the clamping force must face the bearing surface formed by the support element to ensure that the positioning of the workpiece remains unchanged.
2. The point of application of the clamping force should be in a place with good rigidity to reduce the clamping deformation of the workpiece.
3. The point of application of the clamping force should be as close as possible to the processing surface to reduce the rotating moment caused by the cutting force on the workpiece.
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