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How much do you know about machining process?

September 23, 2022

How much do you know about machining process? Here comes the interview question!
1. What are the three methods of workpiece clamping?
1. Clamp in the clamp; 2. Directly align the clamp; 3. Marking and aligning clamp
2. What does the process system include?

Machine tool, workpiece, fixture, tool
3. What are the components of the machining process?
Rough machining, semi finishing, finishing, super finishing
4. How are benchmarks classified?
1. Design datum 2. Process datum: process, measurement, assembly, positioning: (original, additional): (coarse datum, fine datum)

What does machining accuracy include?
1. Dimensional accuracy 2. Shape accuracy 3. Position accuracy
5. What are the original errors during processing?
Principle error, positioning error, adjustment error, tool error, fixture error, rotation error of machine tool spindle, guide error of machine tool guide, transmission error of machine tool, stress deformation of process system, thermal deformation of process system, tool wear, measurement error, error caused by residual stress of workpiece

6. Influence of process system stiffness on machining accuracy (machine tool deformation, workpiece deformation)?
1. Workpiece shape error caused by position change of cutting force action point 2. Machining error caused by size change of cutting force 3. Machining error caused by clamping force and gravity 4. Influence of transmission force and inertia force on machining accuracy

7. What are the guiding errors and spindle rotation errors of the machine tool guideway?
1. The guide rail mainly includes the relative displacement error of the tool and workpiece in the error sensitive direction caused by the guide rail 2. Radial circular runout of the main shaft · axial circular runout · inclination swing
8. What is the phenomenon of "error remapping"? What is the error remapping coefficient? What are the measures to reduce error


Due to the change of process system error and deformation, the blank error is partly reflected on the workpiece Measures: increase the number of tool passes, increase the process system stiffness, reduce the feed rate, and improve the blank accuracy
9. Transmission error analysis of machine tool transmission chain? Measures to reduce transmission error of transmission chain?
Error analysis: that is to use the angle error of the end components of the drive chain Δφ To measure
Measures: 1. The smaller the number of drive chains, the shorter the drive chain, Δφ The smaller it is, the higher the accuracy is

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10. How are machining errors classified? Which errors are constant errors? Which errors belong to variable systematic errors? Which errors belong to random errors
Systematic error: (constant systematic error, variable systematic error) random error
Constant systematic error: machining error caused by machining principle error, manufacturing error of machine tool, cutter and fixture, and force deformation of process system
Variable systematic error: wear of props; Thermal deformation error of tools, fixtures, machine tools, etc. before thermal balance
Random error: copy of blank error, positioning error, tightening error, multiple adjustment error, deformation error caused by residual stress
11. What are the ways to ensure and improve the machining accuracy?
1. Error prevention technology: reasonable use of advanced technology and equipment to directly reduce the transfer of original error The original error is inferior to the original error Average the original error
2. Error compensation technology: online detection of automatic grinding of coupling parts, and active control of error factors that play a decisive role
12. What does the geometric morphology of the machined surface include?
Geometric roughness, surface waviness, texture direction, surface defect
13. What are the physical and chemical properties of the surface layer materials?
1. Cold work hardening of surface layer metal 2. Metallographic structure deformation of surface layer metal 3. Residual stress of surface layer metal
14. Try to analyze the factors that affect the surface roughness of cutting?
Roughness value consists of: the height of the cutting residual area Main factor: the tool tip arc radius Main deflection angle Secondary deflection angle Feed rate Secondary factor: the cutting speed increases Select the cutting fluid appropriately Increase the rake angle of the tool Improve the grinding quality of the tool
15. Try to analyze the factors that affect the surface roughness of grinding?
1. Geometric factors: the influence of grinding parameters on surface roughness 2. The influence of grinding wheel granularity and grinding wheel dressing on surface roughness 2. The influence of physical factors: plastic deformation of surface layer metal: the selection of grinding wheel
16. Try to analyze the factors that affect the cold work hardening of the cutting surface?
Influence of cutting parameters influence of tool geometry influence of material properties
17. What is grinding tempering burn? What is grinding quenching burn? What is grinding annealing burn?
Tempering: if the temperature in the grinding area does not exceed the transformation temperature of the quenched steel, but has exceeded the transformation temperature of martensite, the martensite in the metal on the workpiece surface will be transformed into the tempering structure with lower hardness for quenching; if the temperature in the grinding area exceeds the transformation temperature, plus the cooling effect of the coolant, the surface metal will have a secondary quenching martensite structure, with higher hardness than the original martensite; In his lower layer, due to slow cooling, there is tempering structure annealing with lower hardness than the original tempering martensite: if the temperature of the grinding area exceeds the phase transformation temperature and there is no coolant during the grinding process, the surface metal will have annealing structure, and the hardness of the surface metal will drop sharply
18. Prevention and control of machining vibration
Eliminate or weaken the conditions that generate machining vibration; Improve the dynamic characteristics of the process system, improve the stability of the process system, and adopt various vibration damping devices
19. This paper briefly describes the main differences and applications of machining process cards, process cards and process cards.
Process card: single piece small batch production with common processing method Mechanical process card: medium batch production process card: mass production type requires strict and meticulous organization
20. The principle of selecting rough datum? Principle of precise benchmark selection?
Coarse datum: 1. Principle of ensuring mutual position requirements; 2. The principle of ensuring the reasonable distribution of machining allowance on the machined surface; 3. Principle of facilitating workpiece clamping; 4. The principle that the coarse datum shall not be reused generally. The precise datum: 1. The principle of datum coincidence; 2. Principle of unified benchmark; 3. The principle of mutual benchmarking; 4. Self reference principle; 5. Principle of easy clamping
21. What are the principles of process sequence arrangement?
1. First process the datum plane, then process other surfaces; 2. In half cases, the surface shall be machined first and then the hole; 3. First process the main surface, and then process the secondary surface; 4. Arrange the rough machining process first, and then the finishing process
22. How to divide the processing stages? What are the benefits of dividing the processing stages?
Machining stage division: 1. Rough machining stage, semi finishing stage, finishing stage, precision finishing stage can ensure that there is sufficient time to eliminate thermal deformation and residual stress generated by rough machining, so as to improve the subsequent machining accuracy. In addition, when defects are found in the rough machining stage, the next processing stage is not necessary to avoid waste. In addition, equipment can also be used reasonably. Low precision machine tools are used for rough machining and precision machine tools are used for precision machining to maintain the precision level of precision machine tools; Reasonably arrange human resources, and highly skilled workers are specialized in precision and ultra precision machining, which is very important to ensure product quality and improve process level.