CNC Knowledge: Complete collection of machining technology basics!

1. What are the three methods of clamping workpieces?

{1. Secure the light fixture; 2. Find the right pliers directly; 3. Mark the line and find the right clamp}

2. What does the process system include?

{machine tools, workpieces, fixtures, tools}

3. What are the components of the mechanical processing process?

{roughing, semi-finishing, finishing, superfinishing}

4. How are benchmarks classified?

{1. Design basis 2. Process basis: process, measurement, assembly, positioning: (original, supplementary): (coarse base, fine base)}

What does processing accuracy include?

{1. Dimensional accuracy 2. Shape accuracy 3. Position accuracy }

5. What does the initial error that occurred during processing include?

{Principle error · Positioning error · Setting error · Tool error · Mounting error · Machine tool spindle rotation error · Machine tool guiding error · Machine transmission error tool · Stress deformation of the processing system · Thermal deformation of the processing system · Tool wear · Measuring error · Workpiece residual stress Error caused by

6. What is the impact of the rigidity of the processing system on the precision of machining (deformation of the machine tool, deformation of the part)?

{1. Workpiece shape error caused by changes in the position of the cutting force application point 2. Processing errors caused by changes in the size of the cutting force 3. Processing errors caused by the cutting force clamping and gravity 4. The impact of transmission force and inertia force on processing accuracy}

7. 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}

8. What is the phenomenon of “mistaken re-image”? What is the error reflection coefficient? What steps are being taken to reduce erroneous reimages?

{Due to changes in the deformation of the processing system error, the error of the stock is partially reflected on the workpiece. Measures: increase the number of tool passes, increase the rigidity of the processing system, reduce the amount of feed, and improve the accuracy of the stock.}

9. Transmission error analysis of machine tool transmission chain? Measures to reduce transmission chain transmission errors?

{Error analysis: that is, measured by the rotation angle error Δφ of the end member 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. From the ends of the transmission parts, the error has the greatest impact, so it should be made as accurate as possible 4. Use a correction device }

10. How to classify processing errors? What errors are constant errors? Which errors are systematic errors of variable value? Which errors are random errors?

{System error: (constant value system error, variable value system error) random error

Constant system error: machining principle error, manufacturing error of machine tools, tools, fixtures, stress deformation of process system, etc.

Variable value system error: wear of the props; thermal deformation error of tools, fixtures, machine tools, etc. before thermal balance

Random errors: draft copy errors, positioning errors, clamping errors, multiple adjustment errors, warping errors caused by residual stresses}

11. What are the ways to ensure and improve the accuracy of processing?

{1. Error prevention technology: rationally adopt advanced technology and equipment, directly reduce the original error, transfer the original error, average the original error, and average the original error.

2. Error compensation technology: online detection, automatic matching and grinding of even parts, and active control of decisive error factors}

12. What does processing surface geometry include?

{geometric roughness, surface waviness, grain direction, surface defects}

13. What are the physical and chemical properties of surface layer materials?

{1. Cold work hardening of the surface layer metal 2. Deformation of the metallographic structure of the surface layer metal 3. Residual stress of the surface layer metal}

14. 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. The main factor is: the arc radius of the tool tip and the secondary declination angle. The secondary factor is: increase. cutting speed. Proper selection of cutting fluid. Appropriate increase in tool cutting angle to improve tool cutting edge quality.

15. Try to analyze the factors that affect the surface roughness of the grinding process?

{1. Geometric factors: influence of the amount of grinding on the surface roughness 2. Influence of the particle size of the grinding wheel and the dressing of the wheel on the surface roughness 2. Influence of physical factors: plastic deformation of the metal surface: wheel selection}

16. Try to analyze the factors that affect cold work hardening of cutting surfaces?

{Influence of cutting quantity, influence of tool geometry, influence of processing material properties}

17. What is grinding burn? What is grinding and extinguishing burns? What is grind anneal burn?

{Return: If the temperature in the grinding zone does not exceed the phase transformation temperature of the hardened steel, but exceeds the transformation temperature of martensite, the martensite of the metal on the surface of the workpiece will be transformed into a quenched structure 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 lower hardness superior to that of the original martensite in its lower layer; cooling A quenched structure with lower hardness than the original quenched martensite appeared slowly. Annealing: If the temperature of 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}

18. Prevention and control of mechanical processing vibrations

{Eliminate or weaken conditions that produce mechanical processing vibrations; improve the dynamic characteristics of the processing system and improve the stability of the processing system by using various vibration absorbing devices}

19. Briefly describe the main differences and application opportunities of machining process maps, process maps and process maps.

{Process Map: Single part production in small batches using ordinary processing methods. Mechanical Process Map: Medium Batch Production: Large volume production requires strict and meticulous organizational work.}

*20. What are the principles for selecting approximate references? Principles for a fine selection of benchmark indices?

{Rough reference: 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 crude references generally cannot be reused; . Fine data: 1. The principle of data coincidence; 2. The principle of unified data; 3. The principle of mutual datum; 4. The principle of self-basis;

21. What are the principles of organizing the sequence of the process?

{ 1. Treat the reference surface first, then process other surfaces; 2. In half of the cases, treat the surface first, then treat the holes; 3. Treat the main surface first, then treat the secondary surface; . Arrange the rough machining process first, then arrange the finishing process}.

22. How to divide the processing steps? What are the advantages of dividing the processing steps?

{Division of processing steps: 1. Rough machining step·semi-finishing step·finishing step·precision finishing step can ensure sufficient time to eliminate thermal deformation and eliminate residual stress caused by machining coarse, in order 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 machine tools precision, 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. }

23. What are the factors that affect process margin?

{1. Dimensional tolerance Ta of the previous process; 2. Surface roughness Ry and surface defect depth Ha produced by the previous process; 3. Space error left by the previous process;

24. What is the working hours quota?

{T quota=T time for a single piece + t precise final time/n number of pieces}

25. 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;

26. What is the main content of the assembly process regulations?

{1. Analyze product drawings, divide assembly units and determine assembly methods; 2. Develop assembly sequences and divide assembly processes; 3. Calculate assembly time quotas; 4. Determine assembly technical requirements, quality inspection methods and inspection tools for each process; ; 5. Determine the mode of transport of assembly parts as well as the equipment and tools required. 6. Select and design special tools, accessories and equipment required in the assembly process.}

27. What should be considered in the assembly process of the machine structure?

{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.}

28. What does assembly accuracy generally include?

{1. Mutual position accuracy; 2. Mutual movement precision; 3. Mutual Cooperation Accuracy}

29. What issues should be paid attention to when searching for assembly dimension chains?

{1. The assembly dimension chain should be simplified if necessary; 2. The “one piece and one link” composed of the chain of assembly dimensions; 3. The “directionality” of the assembly dimension chain. assembly accuracy in different positions and directions. Where necessary, the assembly dimension chain should be supervised in different directions.

30. What are the methods to ensure assembly accuracy? How are the different methods applied?

{1. Method of exchange; 2. Selection method; 3. Method of modification;

31. What are the components and functions of machine tool accessories?

{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 unchanged during the machining process. .The components are: 1. Positioning components or devices 2. Tool guiding components or devices 3. Clamping components or devices 4. Connection components 5. Clamp body 6. Other components or devices.

Main functions 1. Ensure processing quality 2. Improve production efficiency 3. Expand the scope of machine tool technology 4. Reduce the labor intensity of workers and ensure production safety.}

32. How are machine tool accessories classified based on their range of use?

{1. Universal luminaire 2. Special luminaire 3. Adjustable luminaire and group luminaire 4. Combined luminaire and random luminaire}

33. The part is positioned on a plane. What are commonly used positioning components? And analyze the situation of removing degrees of freedom.

{The workpiece is positioned on a plane. Commonly used positioning components include 1. Fixed bracket 2. Adjustable bracket 3. Self-positioning bracket 4. Auxiliary bracket}

34. The part is positioned with a cylindrical hole. What are commonly used positioning components? And analyze the situation of removing degrees of freedom.

{The workpiece is positioned with a cylindrical hole. Commonly used locating components include 1. Pin 2. Locating pin}.

35. When positioning a part on an exterior circular surface, what are commonly used positioning components? And analyze the situation of removing degrees of freedom.

{The workpiece is positioned on the outer circular surface. Commonly used positioning components include V-shaped blocks.

36. The part is positioned with “two pins on one side”. How to design the two pins?

{1. Determine the center distance dimension and tolerance of the two pins. 2. Determine the diameter of the cylindrical pin and its tolerance. 3. Determine the diamond pin width, diameter, and tolerance.}

37. What two aspects does positioning error include? What are the methods for calculating positioning error?

{There are two aspects of positioning error. 1. The positioning error caused by the 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 workpiece process. the reference and the positioning reference which do not coincide are called reference position error}.

38. Basic requirements for the design of workpiece clamping devices.

{1. During the clamping process, the correct position obtained when positioning the workpiece must be maintained. 2. The clamping force should be appropriate, and the clamping mechanism should be able to ensure that the workpiece does not loosen or vibrate during processing. and at the same time, the workpiece should be prevented from loosening or vibrating. In case of improper deformation and surface damage, the clamping mechanism 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.}

39. What are the three elements used to determine the clamping force? What are the principles of selection of clamping force direction and action point?

{Selection of the direction of the clamping force at large and small action points should generally follow the following principles: 1. The direction of the clamping force should promote precise positioning of the workpiece without destroying the positioning for this reason . , it is generally required that the main clamping force points vertically towards the positioning surface 2. The direction of the clamping force should be consistent with the direction of the rigidity of the workpiece to reduce the clamping deformation of the workpiece. The clamping force should be consistent with the direction of the cutting force and the gravity of the workpiece to reduce the required clamping. General principles for selecting 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 relatively rigid position 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 machining surface to reduce the rotating moment caused by the cutting force. on the piece}

40. What are the commonly used clamping mechanisms? Focus on analyzing and mastering the wedge clamping mechanism.

{1. Inclined corner clamping structure 2. Spiral clamping structure 3. Eccentric clamping structure 4. Hinge clamping structure 5. Centering clamping structure 6. Linking clamping structure}

41. How to classify drilling molds according to their structural characteristics? How to classify drill guides according to their structural characteristics? What are the categories according to the specific connection modes between the drilling jig and the clamp?

{The drilling mold is based on the total structural characteristics:

1. Fixed drilling die 2. Rotating drilling die 3. Flip type drilling die 4. Cover type drilling die 5. Sliding column drilling die Classification of structural characteristics of drilling die:

2. 1. Fixed drilling mold 2. Replaceable drilling mold 3. Quick-changing drilling mold 4. Special drilling mold The specific connection method of the drilling jig to the clamp:

3. Fixed Hinge Separate Hanging Type}

42. What are the characteristics of machine tool fixtures in machining centers?

{1. Simplified functions 2. Complete positioning 3. Open structure 4. Quick readjustment}