July 2019 – Page 4 – CNC Machining & Turning, Milling, Metal parts

Complete Works of Machining Technology Foundation! The interview questions are coming

How much do you know about the processing technology after so long? Let’s review it together today.
1. What are the three methods of workpiece clamping?

{1. clamping in fixture; 2. direct alignment clamp; 3. scribed alignment clamp}

2. What are the contents of the process system?

{Machine Tools, Workpieces, Fixtures, Tools}

3. Composition of Machining Process?

{Rough, Semi-Finish, Finish, Ultra-Finish}

4. How to classify benchmarks?

Design Benchmark 2. Process Benchmark: Procedure, Measurement, Assembly, Location: (Original, Additional): (Rough Benchmark, Precise Benchmark)] ____________

What does the processing accuracy include?

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

5. What are the original errors in the process of processing?

{Principle error, Positioning error, Adjustment error, Tool error, Fixture error, Machine spindle rotation error, Machine tool guide error, Machine tool transmission error, Mechanical deformation of process system, Thermal deformation of process system, Tool wear, Measurement error, Error caused by residual stress of workpiece}

6. The influence of stiffness of process system on machining accuracy (machine tool deformation, workpiece deformation)?

{1. Workpiece shape error caused by change of position of cutting force action point 2. Machining error caused by change of cutting force size 3. Machining error caused by clamping force and gravity 4. Effect of transmission force and inertia force on machining accuracy}

7. What are the guiding errors and spindle rotation errors of machine tool guides?

{1. The guide mainly includes relative displacement errors of tool and workpiece in error sensitive direction caused by the guide 2. Radial circular runout of spindle, axial circular runout and tilt angle swing}

8. What is the phenomenon of “error duplication”? What is the error mapping coefficient? What measures can be taken to reduce error reproduction?

Because of the change of the error and deformation of the process system, the part of the blank error is reflected in the workpiece. Measures include increasing the number of cutters, increasing the stiffness of the process system, reducing the feed and improving the precision of the blank.

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

Error analysis: that is to say, the angle error of the end element of the transmission chain is measured by the angle error

Measures: 1. The smaller the number of transmission chains, the shorter the transmission chains, and the smaller the_, the higher the accuracy. 2. The smaller the transmission ratio I, especially the smaller the transmission ratio at both ends. 3. Because the error of the end parts in the transmission parts has the greatest impact, it should be as accurate as possible. 4. Using correction device}

10. How to classify machining errors? Which errors belong to constant errors? Which errors belong to variable system errors? Which errors belong to random errors

Systematic Error: (Constant Systematic Error Variable Systematic Error) Random Error

Constant System Errors: Machining Principle Errors, Manufacturing Errors of Machine Tools, Tools, Fixtures, Stress and Deformation of Process Systems, etc.

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

Random error: copy of blank error, positioning error, tightening error, error of multiple adjustments, deformation error caused by residual stress}

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

Error Prevention Technology: Rationally Using Advanced Technology and Equipment to Reduce the Initial Error Transfer, the Initial Error Transfer, the Initial Error Homogenization and the Initial Error Homogenization

2. Error Compensation Technology: On-line Inspection of the Error Factor in Active Control of Automatic Matching of Couple Parts

12. What are the contents of machined surface geometry?

{Geometric roughness, surface waviness, texture direction, surface defects}

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

Cryogenic Hardening of Surface Metal 2. Metallographic Deformation of Surface Metal 3. Residual Stress of Surface Metal}

14. Trial analysis of factors affecting the surface roughness of cutting?

Roughness value is determined by: the main factor of the height of the cutting residual area: the secondary factor of the feed rate of the main deviation angle and the vice-deviation angle of the tool tip arc radius: the increase of cutting speed, the appropriate choice of cutting fluid, the appropriate increase of the rake angle of the tool, and the improvement of the grinding quality of the tool.)

15. Trial analysis of factors affecting surface roughness in grinding?

Geometric factors: the influence of grinding parameters on surface roughness 2. The influence of grinding wheel size and grinding wheel dressing on surface roughness 2. The influence of physical factors: plastic deformation of surface metal: the choice of grinding parameters for grinding wheel}

16. Try to analyze the factors affecting the cold work hardening of the machined surface.

{The influence of cutting parameters on tool geometry and 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 zone does not exceed the phase transformation temperature of quenched steel, but has exceeded the transformation temperature of martensite, the martensite on the surface of the workpiece will be transformed into a tempered structure with lower hardness for quenching. If the temperature in the grinding zone exceeds the transformation temperature, coupled with the cooling effect of coolant, the surface metal will have a secondary quenching martensite structure with hardness higher than the original martensite. In his lower layer, annealing of tempered structure with hardness lower than that of original tempered martensite occurs because of slower cooling. If the temperature in the grinding zone exceeds the phase transformation temperature and there is no coolant in the grinding process, annealing structure will appear on the surface metal and the hardness of the surface metal will decrease sharply.

18. Prevention and Control of Machining Vibration

Eliminating or weakening the conditions for vibration in machining; improving the dynamic characteristics of the process system and improving the stability of the process system

What should gear reducer pay attention to during running-in period

Reducer in the actual use of the process are all in need of a run-in period, the correct run-in period, can effectively extend the life of the entire reducer gear, and before use, all operators are basically in accordance with the relevant methods given by the regular manufacturers to guide the operation, reducer in the actual use of the process should pay attention to what?
Reducer in the actual use of the process are all in need of a run-in period, the correct run-in period, can effectively extend the life of the entire reducer gear, and before use, all operators are basically in accordance with the relevant methods given by the regular manufacturers to guide the operation, reducer in the actual use of the process should pay attention to what?
1. During the operation of the reducer, we must pay attention to limiting all running-in periods. The workload of gear deceleration and even the whole workload should not exceed the rated workload of the reducer itself, and we should arrange a suitable time, because only in this way can we avoid the overheating of the whole phenomenon.
2. In the process of actual operation of gear reducer, we must observe the final operation situation. If there is any abnormality, we should stop the abnormal situation. Of course, we should exclude all the faults and stop the operation. We should reflect this situation to the merchants or manufacturers and help them solve it well.
3. In the actual working process of gear reducer, it is necessary to select the most suitable lubricating oil, especially the reducer with relatively large input power. Relatively speaking, during this period, they may often check the quality of all lubricants, or other conditions, to check the sealing of the whole machine, and in the process of inspection, you may find that these lubricants are missing, so in this case, it is necessary to analyze their reasons, whether it is because of the lack of use too fast. Or for other reasons, to help us find the problem.

Matching Skills of Shock Absorbers

First, check whether the product provides 2-3 inch elevation requirements, some products only provide 2 inch elevation, barely used to 3 inch elevation, it is easy to pull to the limit in cross-country damage.
Secondly, whether the diameter of the expansion rod in the center of the shock absorber can reach more than 16 mm is a basic index of strength.
Thirdly, whether the upper and lower connection sleeves of the shock absorber are high strength polyurethane sleeves is also an important basis for ensuring long-term high strength use, because ordinary rubber is difficult to use for long time under high strength.
The shock absorber is mainly used to restrain the vibration of spring when it rebounds after vibration absorption and the impact from the road surface. Although the shock absorber spring can filter the vibration of the road surface when passing through the uneven road surface, the spring itself will also have reciprocating motion, and the shock absorber is used to suppress the spring jump. If the shock absorber is too soft, the car body will jump up and down. If the shock absorber is too hard, it will bring too much resistance and hinder the normal work of the spring. Shi Xiaohui said that in the process of refitting the suspension system, hard shock absorbers should be matched with hard springs, and the hardness of the springs is closely related to the weight of the vehicle, so the heavier vehicles generally use harder shock absorbers. In order to design the best combination of shock absorber and spring, it is necessary to constantly try in refitting. Professional refitting stores can generally find the best match for owners.

Classification of Safety Valves by Principle of Action

According to the principle of action, it can be divided into direct-acting safety valve and non-direct-acting safety valve.
1. Direct acting safety valve
Direct acting relief valve is opened under the direct action of working medium, that is, relies on the action of working medium pressure to overcome the mechanical load imposed on the valve disc by the loading mechanism, so that the valve opens. The safety valve has the advantages of simple structure, quick action and good reliability. However, due to the structural loading, its load size is limited, and can not be used in high-pressure, large-caliber occasions.
2. Non-direct acting safety valve
This kind of safety valve can be divided into pilot safety valve and power assistant safety valve.
Pilot safety valve is driven or controlled by the medium discharged from the pilot valve. The pilot valve itself is a direct acting safety valve, sometimes other forms of valves are also used. Pilot safety valve is suitable for high pressure and large caliber occasions. The main valve of pilot relief valve can also be designed to be sealed by working medium, or it can impose a much larger mechanical load on the disc than the direct acting relief valve, so it has good sealing performance. At the same time, its movements are seldom affected by back pressure. The disadvantage of this kind of safety valve is that its reliability is related to the main valve and the guide valve. Its action is not as fast and reliable as that of the direct acting safety valve, and its structure is more complex.
The safety valve with power assistant device is forced to open under normal opening pressure by means of a power assistant device. This safety valve is suitable for situations where the opening pressure is very close to the working pressure, or where the safety valve needs to be opened regularly for inspection or blowing out the sticky and frozen medium. At the same time, it also provides a means to force the opening of safety valve in emergency.

Matching Skills of Shock Absorbers

Common Types and Manufacturing Equipment of Mechanical Gears

Gears are the main basic transmission components in the machinery manufacturing industry. Wheeled mechanical parts, which transmit torque by meshing teeth, can realize the functions of changing rotational speed and torque, changing the direction of motion and changing the form of motion by driving with other gear mechanical parts. But for the manufacturing process of high precision gear, especially the gear with many teeth, large diameter, long tooth surface, high precision and long processing cycle, strict process guarantee is required in the hobbing process, and all links such as blank processing, fixture, cutter, machine tool adjustment and environment must be well controlled. Following is a brief introduction to the manufacturing process of automotive gears in Yida Borun Petrochemical Company.

I. Types of Common Gears

Gears can be classified according to the shape of the gear, the shape of the tooth line, the surface of the gear teeth and the manufacturing method.

(1) Gears can be divided into cylindrical gears, bevel gears, non-circular gears, racks, worm and worm gears according to their shape.

(2) Spur gear, helical gear, herringbone gear and curve gear are classified according to the shape of tooth line.

(3) According to the surface of the gear teeth, it can be divided into outer gear and inner gear.

(4) According to the manufacturing method, it can be divided into casting gear, cutting gear, rolling gear, sintered gear and so on.

(5) According to the hardness of gear tooth surface, it can be divided into soft tooth surface gear and hard tooth surface gear.

II. Equipment for Gear Manufacturing

(1) Hobbing machine is a kind of gear hobbing machine, which uses hobs to develop rough, precision straight teeth, helical teeth, herringbone gears and worm gears, so as to achieve higher accuracy and efficiency.

(2) Gear shaping machine is used to cut spur, helical gear and other teeth by generating method with gear shaping cutter. It is mainly used for multiple gears and internal gears.

(3) The gear milling machine is milling by indexing method with forming milling cutter, which is mainly used for instrument gears with special tooth profile.

(4) Shaving machine is a kind of efficient machine tool which uses gear shaving cutter to finish gears.

(5) Grinding machine is a high-precision machine tool with grinding wheel, precision hardening cylindrical gear or gear cutter tooth surface;

(6) Honing machine is a machine which uses the free meshing between the honing wheel and the gear to eliminate the burr of hardened gear and other tooth surface defects.

(7) The extruder is a machine tool which uses the free meshing of the extruder with high hardness and no cutting edge to smooth the slight unevenness on the tooth surface, so as to improve the accuracy and smoothness.

Selection of Cutting Oils

(1) Silicon steel is a relatively easy-to-cut material. Generally, in order to clean the finished gear workpiece easily, low-viscosity gear cutting oil will be selected on the premise of preventing burrs.

(2) When choosing cutting oil for carbon steel gear cutting, the better viscosity should be determined according to the process difficulty and degreasing conditions.

(3) Because galvanized steel and chlorine additives will react chemically, attention should be paid to the possibility of white rust of gears when choosing gear cutting oil. Rust can be avoided by using Yida Borun sulfur-type special gear cutting oil, but degreasing should be done as soon as possible after processing.

(4) In the cutting of stainless steel gears, the gear cutting oil containing sulfur-chlorine compound additives is generally used to ensure the extreme pressure performance, while avoiding burrs and cracks in the workpiece.

These are the common types of gear and gear manufacturing equipment. Rational selection of gear manufacturing equipment can effectively reduce investment and improve efficiency.

Surface Treatment Requirements for CNC Processing

1. From the aspect of appearance, the surface machined by parts is free from obvious defects such as scratches and abrasions.

2. The product surface processed by NC lathe must be smooth, beautiful, no burr, no flying edge, etc.

3. In terms of quality, the machined surface of parts must meet the requirements in terms of corrosion resistance, wear resistance and hardness.

In order to meet the accuracy of parts processing, it is necessary to meet the requirements of surface technology and appearance. Computer Gong processing | Dongguan high-speed computer gong processing | Dongguan die processing | Dongguan mechanical parts processing | CNC processing of the parts we processed can not appear to be all burrs and other situations, here we introduce the surface processing requirements of CNC lathe processing:

1. From the aspect of appearance, the surface machined by parts is free from obvious defects such as scratches and abrasions.

2. The product surface processed by NC lathe must be smooth, beautiful, no burr, no flying edge, etc.

3. In terms of quality, the machined surface of parts must meet the requirements in terms of corrosion resistance, wear resistance and hardness.

1. Selection Principle of Cutting Parameters

Dongguan high-speed computer gong processing to determine the basic principles of three elements; according to cutting requirements, first determine the back feed ap, then look up the table to get the feed, and then through the table to calculate the main cutting speed U.

In many cases, we can determine the value of these three elements through empirical data.

2. Selection of Cutting Parameters

Practice has proved that the choice of reasonable cutting parameters is related to many factors, such as machine tools, cutting tools, workpieces and processes. The methods of reasonable selection of processing dosage are as follows:

When roughing, it is necessary to ensure higher production efficiency, so a larger back-feed should be chosen. For larger feed, the cutting speed U is selected as medium and low speed.

When finishing, the requirement of dimension and surface precision of parts is guaranteed. Therefore, a smaller back feed ap, a smaller feed, and a higher cutting speed U are chosen.

In rough machining, the potential of NC lathe and the cutting ability of tool should be brought into full play. When semi-finishing and finishing in CNC lathe factory, Dongguan mould processing should focus on how to ensure the quality of processing, and on this basis, try to improve productivity. Computer Gong processing | Dongguan high-speed computer gong processing | Dongguan mould processing | Dongguan machine parts processing | CNC processing CNC lathe factory in the selection of cutting parameters should ensure that the tool can be processed to complete a part or ensure that the tool durability is not less than a working class, at least not less than half the working hours. The specific numerical value of CNC lathe factory should be selected according to the specification of machine tool, tool durability and practical experience.

(1) The choice of knife size on the back. The selection of back-cutting tool quantity depends on the stiffness of machine tool, fixture, moon tool and workpiece and the power of machine tool. When the process system permits, we should select as much knife feed as possible. Except for the margin reserved for later working procedure, the remaining roughing margin is removed as soon as possible so as to minimize the number of cutters.

Usually on medium-power machine tools, the back feed of roughing is 8-10 mm (single side). The back feed of semi-finish machining in CNC lathe factory is 0.5-5 mm, and that of finish machining is 0.2-1.5 mm.

(2) The determination of feed quantity. Feed quantity refers to the direction of tool feed per unit time. CNC lathe factory moving distance. The principle of determining feed speed is that when the quality requirement of workpiece can be guaranteed, higher feed speed can be selected to improve productivity. Computer Gong processing | Dongguan high-speed computer gong processing | Dongguan die processing | Dongguan mechanical parts processing | CNC processing CNC lathe factory cutting, turning deep holes or finishing, should choose a lower feed speed. Feed speed should be adapted to spindle speed and back feed.

How to Prevent Collision in CNC Machining

In such a high speed and construction situation, once the operator can not press the emergency stop button due to programming and operation errors, the tool has collided with the workpiece. Computer Gong processing | Dongguan high-speed computer gong processing | Dongguan die processing | Dongguan machine parts processing | CNC processing in order to prevent the emergence of machine tools and personal affairs, the following methods can be adopted in programming and operation (take FANUC system as an example).

The origin of the workpiece coordinate system set by the programmer should be outside the workpiece blank, at least on the workpiece surface.

Under normal conditions, the origin of workpiece coordinate system can be set anywhere, as long as the origin has a certain connection with the origin of machine tool coordinate system. But in practice, if the instruction value is zero or close to zero, the tool will point directly to zero or near zero. In milling, the tool will run to the worktable of machine tool or the base of fixture: in turning, it will run to the base of chuck. In this way, the tool will penetrate the workpiece and point directly to the datum. At this moment, if we want to move quickly, something will happen.

FANUC system generally set: when the decimal point is omitted, it is the smallest input unit, usually micron. When the decimal point is omitted, the input value will be reduced to one thousandth. At this moment, the input value will be close to zero. Perhaps, because of other factors, the tool should have been separated from the workpiece, but the practice has not been separated from the workpiece and entered the workpiece. When this happens, the zero of the workpiece coordinate system should be located outside the workpiece or on the base of the workbench (or fixture), and the results will be different.

Programmers and operators should be more careful about decimal points when writing programs.

FANUC system is the smallest setting unit when decimal point is omitted, while most domestic systems and some systems in Europe and America are mm when decimal point is omitted, that is, calculator input method. If you get used to the calculator input method, there will be problems in the FANUC system. Many programmers and operators may use both systems. In order to prevent the scale from becoming smaller due to decimal points, decimal points should be added to the program of calculator input method. Computer Gong processing | Dongguan high-speed computer gong processing | Dongguan die processing | Dongguan mechanical parts processing | CNC processing, to do so, for a certain type of system is surplus, but after cultivating habits, there will be no problems due to decimal points.

In order to make decimal points attractive, isolated decimal points are usually written as “.0” in programming. Of course, the zero after the decimal point of the numerical value is neglected in the execution of the system.

When adjusting the workpiece coordinate system, the operator should set the reference point outside the physical (geometric) length of all the cutters, at least on the cutter location of the longest cutter.

For the workpiece coordinate system on the workpiece installation drawing, the operator acquires it by setting the offset of the machine tool coordinate system on the CNC machining center. That is to say, the operator sets a reference point on the CNC machining center, and finds the scale between the reference point and the zero of the workpiece coordinate system set by the programmer, and sets this scale as the workpiece coordinate system offset.

On the lathe, the reference point can be set on the rotating base of the tool holder, on the tool tip of the reference tool or in other directions. If no additional motion is added, the zero of the programmer’s instruction is to move the reference point of the tool holder (CNC machining center) to the zero azimuth of the offset. At this moment, if the datum point is set on the rotary base of the tool holder, the tool holder will collide with the workpiece. In order to ensure no collision, the reference point of CNC machining center should be located not only outside the tool holder, but also outside all the tools. So even if the tool holder is equipped with a tool, the reference point will not collide with the workpiece.

In CNC machining center, the reference points of X and Y axes are on the axis center line. However, the reference point of Z axis can be set at the end of the spindle or at some point outside the end of the spindle. If the instruction is zero at the spindle end, the spindle end will reach the zero orientation specified in the coordinate system. Computer Gong processing | Dongguan high-speed computer gong processing | Dongguan die processing | Dongguan mechanical parts processing | CNC processing at this moment, the end of the spindle key will collide with the workpiece: if the spindle is equipped with a tool, it will collide with the workpiece. In order to ensure no collision, the reference point on Z axis should be set outside all tool lengths. Even without additional motion, the reference point will not hit the workpiece.

Types of Boring in CNC Machining

10. Reaming: The workpiece should be positioned by a central drill before drilling with a bit 0.5-0.3 mm smaller than the drawing size. Computer Gong processing | Dongguan high-speed computer gong processing | Dongguan die processing | Dongguan machine parts processing | CNC processing | and reamer reaming. When reaming, attention should be paid to controlling the spindle speed in 70-180 rpm/min.

11. Boring processing: the workpiece should be positioned with a central drill, then drilled with a bit 1-2 mm smaller than the drawing size, then processed with a rough boring cutter (or milling cutter) to the processing margin of only 0.3 mm on one side, and finally finished with a pre-adjusted size fine boring cutter. The last fine boring margin should not be less than 0.1 mm.

12. Direct numerical control (DNC) operation:

13. Before DNC NC machining, the workpiece should be clamped, the zero position should be fixed and the parameters should be set.

14. Open the processing program to transmit data in the computer to check, then let the computer enter the DNC state, and input the file name of the correct processing program.

15. Press the TAPE key and the program start key on the machine tool, when the LSK gleams on the machine controller.

16. DNC data transmission can be processed by pressing the return keyboard on the computer.

3. Contents and scope of workers’self-examination:

1. Processors must see clearly the contents of the process card before processing, know clearly the parts, shapes, sizes of the drawings to be processed, and know the processing contents of the next process.

2. Before clamping the workpiece, the blank size should be measured to meet the requirements of the drawings. When clamping the workpiece, the placement of the workpiece must be carefully checked to be in accordance with the programming instruction book when computer gong processing | Dongguan high-speed computer gong processing | Dongguan die processing | Dongguan mechanical parts processing | CNC processing.

3. Self-inspection should be carried out in time after rough processing is completed. Machinery parts in Dongguan should be processed in order to adjust the data with errors in time. Dongguan high-speed computer gong processing self-inspection content mainly for the location and size of processing parts. Such as: (1) whether the workpiece is loose; (2) whether the workpiece is correctly divided; (3) whether the dimension of the processing part to the reference edge (reference point) meets the requirements of the drawing; (4) the position and dimension of the processing parts to each other. After checking the position and size, the shape ruler of rough machining should be measured (except for arc).

4. Finishing after rough processing and self-inspection. Computer Gong processing | Dongguan high-speed computer gong processing | Dongguan die processing | Dongguan machine parts processing | CNC finishing processing workers should check the shape and size of the processing parts: the basic length and width of the processing parts on the vertical plane are measured; the base point size on the processing parts of the inclined plane is measured.

A little knowledge of steel

Steel is an indispensable and important material for national construction and Realization of the Fourth Century. It is widely used and has a wide variety of varieties. According to the different section shapes, steel is generally classified into types.

In order to organize the production, ordering and supply of steel products and do well in management and management, the four major categories of steel, plate, pipe and metal products are divided into heavy rail, heavy rail and heavy rail.

Large section steel, medium section steel, small section steel, cold-formed steel, high-quality section steel, wire rod, medium-thick steel plate, thin steel plate, silicon steel sheet for electrical purposes,,

Seamless steel pipe, welded steel pipe, metal products and other varieties.

2. Production Method of Steel

Most steel products are processed by pressure, which results in plastic deformation of the processed steel (billet, ingot, etc.). According to the processing temperature of steel, there are two kinds of different processing methods: cold processing and hot processing. The main processing methods of steel are as follows:

Rolling: The rolling of steel and metal billets through a pair of rotating rolls gap (various shapes), due to the reduction of the cross section of the material by the compression of the rolls, the length of the increased pressure processing method, which is the most commonly used production method of steel products, mainly used to produce steel profiles, sheets, pipes. It is divided into cold rolling and hot rolling.