Case Study Of Valve Spring And Bogie Spring-fatigue Fracture

1. Fatigue fracture of spring

Generally, the fatigue fracture is composed of three parts: fatigue source, crack propagation zone and final transient fracture zone. The source of fatigue is sometimes very clear and sometimes unclear. The crack propagation area and the final transient fracture area are the main components.

Features of crack growth area: The surface is relatively smooth, which is the result of slow crack growth, crack surface contact and friction. It is a brittle fracture feature, and the crack propagation direction is perpendicular to the direction of maximum tensile stress. You can usually find the beach-like, shell-like or annual ring-shaped patterns on the fracture with the naked eye. The fatigue source of spring fracture can be determined according to the phenomenon that the crack propagation direction is perpendicular to the beach-like stripes and the feature of the smallest radius of curvature.

Characteristics of transient fracture zone: After the fatigue cracks continue to expand to a certain extent, the effective load bearing area continues to decrease, and the corresponding working stress gradually increases. When the stress exceeds the spring's fracture stress, the spring will instantly fracture. Its characteristic is that the fracture is relatively rough and uneven.

Microscopic characteristics of fatigue fracture: Most of the fatigue cracks start to form between grain boundaries, phase boundaries, inclusions and brittle carbides, and then gradually expand inward. The microscopic characteristics of the fatigue fracture are mainly manifested in the crack propagation zone. The main micro-characteristic of the extended zone is the fatigue band. Fatigue strips have the following characteristics: ① the shape of the strips is undulating or rippled; ② each strip represents a cyclic load; ③ the position of the crack front line can be determined by the strip .

2.Case Studies

(1) BROKEN VALVE SPRING

① Accident description: Valve spring is an important part of automobile engine. It not only controls the opening and closing of engine valves, but also is an extremely important safety component. Therefore, automobile manufacturers attach great importance to the quality of engine valve spring. / T 10591-2007 requires its bench fatigue test not to break 23 million times. A certain type of car experienced abnormal engine noise and idle vibration when traveling 199km after leaving the factory. After inspection, it was found that a valve spring was broken.

② Cause analysis: It can be seen from observation that the corresponding spring surface at the fracture source has an approximately elliptical pit with a long axis length of 0.82 mm and a short axis length of 0.43 mm. Can be found from the following figure:

There are no signs of shot blasting in the pits on the surface of the spring break, and there are obvious scratch marks, indicating that the pits are not inherited from the pit defects on the surface of the oil-quenched and tempered spring steel wire, but are generated when the spring is well-prepared of. At the same time, the figure also tells us that there is a covering on the surface of the spring at the source of the fracture. The covering originates from the side of the pit, so it can be concluded that the covering is the metal material at the pit location. It can be inferred that the accidental factor caused the spring to be scraped by the external force, forming the above-mentioned pit, and generating concentrated stress when the impact scratched the bottom of the pit. The valve spring is subjected to alternating stress during service. The maximum tensile stress is located on the subsurface of the spring, and the stress concentration at the bottom of the pit and the maximum tensile stress are superimposed on each other. As a result, the valve spring starts early under the action of shear force and forms under the pit. The source of fatigue fractures expands rapidly, causing early fatigue fractures.

Since the cause of the fracture was improper use, we artificially started the fracture directly from the crack propagation stage. As explained in the textbook, the initial stage of fatigue cracks accounts for 90% of the entire fatigue fracture process, so the fatigue life of valve springs is only about 10%. It is not difficult to explain that the valve spring will break after a short period of use. The main factor affecting the crack growth at this time is the stress intensity factor K:

From the formula we can see that β is a dimensionless quantity, so the value of K is determined by a. With the gradual expansion of the crack, the value of K increases continuously. When K = Kmax, the spring will break.

③Preventive measures: By analyzing the chemical composition of the spring, its chemical composition meets the requirements of national standards.

However, there are loopholes in the post-processing process, and the process of shot peening is lacking. The textbook tells us that shot peening can effectively remove residual stresses to relieve fatigue damage and extend the service life of springs. Because if the manufacturer can increase the shot peening process during the processing, the service life of the valve spring can be effectively extended. However, in this case, dents on the spring surface due to scratching are the main cause of fatigue fracture, so the shot peening process can only appropriately alleviate this problem. To fundamentally solve the problem of fatigue and fracture in the case, non-destructive testing can be used to pick out defective parts in advance, thereby improving product safety and reducing economic losses. The visual rule is the most economical non-destructive test method. If you want to improve the accuracy of the test on this basis, magnetic particle testing and ultrasonic testing can also be adopted.

④Maintenance: This kind of problem is caused by artificial unconscious crack damage, so the engine does not appear abnormal and it is difficult to find the cracks. When the engine really fails, the spring is usually broken and cannot be repaired, so there is no effective way Repair the spring before it breaks.

(2) ANALYSIS OF SPRING BREAKAGE OF K2 BOGIE

① Accident description: The process of turning k2 spring is: raw material incoming inspection → blanking → flattening → heating and coiling → quenching → tempering → primary process compression → end face grinding → shot blasting → magnetic particle inspection → secondary process Compression → Final inspection → Dip paint → Drying → Storage → Delivery. During the spring manufacturing process, due to various reasons, some springs were scrapped due to failure during the manufacturing process. Early fracture occurred during the inspection and random inspection process, and especially serious was the fracture after loading. In our tests, 11 manufacturers producing K2 springs, 4 of which were broken during the quality inspection process, the number of spring fatigue tests was 3 million, and the number of 4 fatigue test breaks were 680,000, 79 10,000 times, 2.29 million times, 2.49 million times.

②Cause analysis: Unlike the previous case, the failure of the spring in this case was not due to surface defects caused by humans. Before testing, we can roughly guess that it is because of a loophole in the processing process that caused the spring to fail the standard inspection. From the textbook, we know that the residual stress has a great impact on the fatigue performance of the component. At the same time, the process of heat treatment will introduce residual stress, so we should focus on checking the problems in the heat treatment process. According to the information introduced in the literature: the spring heat treatment process is 850 ° C ± 10 ° C, the No. 10 mechanical oil is cooled, and the tempering process is 515 ° C × 65min. By observing the microstructure of the transverse metallographic sample of the fracture spring, it was found that the spring has a deep fully decarburized + semi-decarburized layer with a depth of 0.45mm.

Remarks: The left of the figure is the total decarburization and the semi-decarburization. The right is the heart tissue

Then we started to analyze the fracture structure. The fracture can be clearly divided into three areas: the white bright area, the wood grain fracture area, and the other rapid fracture areas. The white bright area can be determined to be a fatigue area, the source area of which is located on the surface of the inner ring of the spring, and the maximum stress point when it is pressed down. Micro-cracks propagating inward from the surface can be seen in the source area, and fatigue cracks begin at the micro-cracks. The extension area is flat, and obvious fatigue groove lines can be seen. On the other hand, inclusions can be found in the wood grain-like fracture area. This shows that the wood grain fracture area is related to debris. It can be known from the processing process and fracture analysis that the cause of spring fracture is not caused by a single process, and each of the main links in the processing process has different degrees of influence. The quenching and heating time during the heat treatment of the spring is too long, causing serious decarburization on the surface; the defects existing on the surface of the raw material have not been completely removed. Since the maximum stress of the spring occurs on the surface of the spring, the surface quality of the spring has a great impact on the fatigue strength. Defects caused by rolling, drawing and coiling are often the main causes of fatigue fracture of springs. Therefore, we can conclude that the reason for the spring fracture is the influence of the material itself (too many inclusions), and there is a deep decarburization layer on the spring surface.

③Precautions: 1) Spring material: first review the raw materials before processing, and then process after the inspection is qualified, and then perform the blanking operation after the surface quality inspection has no defects. 2) Manufacturing method: In the process of spring coiling and heat treatment, a controlled atmosphere furnace should be used as far as possible to achieve less oxidation-free heating. 3) In addition, shot peening can be added in the process. This process can reduce harmful residual tensile stress, and can also convert residual tensile stress into favorable participating compressive stress, thereby improving the fatigue strength of the spring. 4) After shot blasting, clean up the steel shots in the spring to avoid contact fatigue fracture of the spring. 5) For the surface of the spring, we can detect non-conforming products in advance by non-destructive testing methods, such as ultrasonic testing or eddy current testing.

④Maintenance: For components that have suffered fatigue damage, I have not found an effective method to repair the spring from the root cause, but we can extend the fatigue life of the spring by other means. Since the spring is a steel material part, we can extend its fatigue life by repair annealing. According to data, repair at 550 ° C can extend its fatigue life up to twice. During the annealing process, the strain energy stored in the spring will be released as a driving force, which will change the microscopic state of the structure to a more stable state. In particular, the transformation of carbides delays the occurrence of carbide interface cracks. Of course, the effect of annealing repair is also related to the degree of fatigue damage. As the degree of damage increases, the conditions and number of microcracks increase, and microcracks are unhealable, and the repair effect will naturally decline. In addition, we can also increase the surface hardness and isostatic residual stress by means of a thermostatic isostatic method at medium temperature to delay the initiation of microcracks or to close the microcracks that have been generated. Reduce the effective driving force at the crack tip and slow down the propagation rate of the microcrack. Thereby increasing fatigue life.

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How To Solve The Compression Problem Of Coil Springs?

(1) From a practical perspective

In practice, everyone often encounters that the coil spring cannot press the moving object at the set position, that is, the arbitrary size of the coil spring is short. The core reason is that the helical spring is compressed by excessive force to the compression degree or compression degree (if necessary) without being subjected to the original compression treatment. After opening, the coil spring cannot be restored to the original random size operation process. Its shortening is called "raw compression". In general, after 3 to 6 compressions, the size has not been shortened, that is, the coil spring is "precisely positioned". The coil spring is permanently deformed after the original compression.

(2) From a specific work perspective

In a specific job, even if the force experienced by the compression spring exceeds the ductility limit of the raw material, it should be able to maintain its working size. Therefore, the size of the finished coil spring should be equal to the calculated length and original compression of the coil spring, so that the coil spring cannot be in place, which will cause risk stress when the coil spring ring is tightened, which may cause the coil spring marking line to An exception has occurred and is not a substitute for the coil spring identification line. During the heat treatment process of the finished product coil spring, especially during the tempering process, the artifact should be placed in the furnace as horizontally as possible to prevent the coil spring from being shortened due to its own weight effect, resulting in poor operation.

(3) From the angle of insufficient coil spring force

The requirement of insufficient spring force of the coil spring is to cause the necessary coil spring force as much as possible under the specified deformation. If the load is removed, the coil spring will be repaired to an arbitrary size, and the moving member will smoothly move to the set position. But sometimes the coil spring force cannot be fixed.

(4) From the perspective of stretching

During the stretching process, try to get rid of the friction between the ring and the ring, the ring and the mandrel or sleeve, and the friction between the motion pair and the motion pair. Sometimes the sliding friction range is very large (up to ± 50 %), Resulting in insufficient coil spring force. Unable to get rid of the friction and move the components in place, causing the coil spring to work ineffective. Therefore, try to strictly implement the production process standard as far as possible to carry out in-depth each process, such as screening, coil spring molding, flattening of both ends, removal of edges and corners, heat treatment process, correction adjustment, initial pressure treatment, inspection and refueling.

(5) Other angles

In addition, the coil spring force is also related to design factors and raw material selection factors. From the two core calculation methods of the coil spring, namely the deformation formula lambda = 8pd32n / gd4 and the ground stress formula _uu = k8pd2 / pid3, it can be seen that the coil spring force is greatly affected by the diameter of the wire, ring diameter, deformation and number of rings. This is closely related to the characteristics of raw materials, working temperature, load characteristics and ring numbers. Dynamic hazards can cause abnormal coilspring forces and deformation markings.

Our company is dedicated to the sales and communication of springs and spring machines. If you have any intention, please contact us.
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In The Face Of An Epidemic, How Should We Ensure Security?

At present, China's national defense control of a new coronavirus-infected pneumonia epidemic is at a critical stage. The resumption of production and production in the spring industry will also enter a peak period. How can companies do a good job of prevention and control to ensure the health and safety of employees?

First, Start-up time and factory personnel control

1. It is recommended that the company should set up an epidemic prevention team

In response to the epidemic situation, a company epidemic prevention team was set up to carry out personnel control, environmental disinfection, epidemic publicity, material preparation and other aspects to ensure that all the company's epidemic protection measures are in place.

2.Recommended time for enterprises to resume work after the holiday

Regarding the timetable for enterprises to resume work after the holiday, they should adjust according to the local epidemic control degree to ensure that the epidemic situation is not spread.

3. Factory resumption operation inventory

Focusing on the "man-machine-material law loop" and other aspects, inventory of production operations and formulate corresponding countermeasures.

4. Factory environment disinfection

Before resuming work, all areas of the factory must be disinfected and sterilized to ensure the safety of the personnel inside the factory. Pay special attention to dining in the cafeteria, and when the personnel gather at the morning and regular meetings.

5. Control measures for returning workers to the factory

According to the epidemic situation, formulate the control plan for returning workers to the factory and the measures for controlling the flow of people during the return to work.

6. Management preparations during vacation

Clarify the preparations that company managers need to complete during the vacation, and set the responsible person and completion time.

7. Resumption arrangements

The epidemic prevention team will arrange related work during the post-holiday return to work, clarify the person responsible and the completion time.

8. Prepared list of epidemic protection supplies

Prepare protective equipment for the epidemic before returning to work.

Second, the factory resumption of work to resume pneumonia epidemic prevention program

1. Epidemic prevention preparations before the resumption of work and production

(1) The factory collects epidemic prevention knowledge, publicity videos, and publicity videos from official professional institutions, and conducts publicity in areas such as publicity boards, corporate Wechat, and electronic large screens.

(2) Statistical medical masks, KN90 or KN95 masks, protective clothing (mainly sanitation for sanitation), protective glasses, 75% alcohol (absorbent cotton) / 84 disinfectant, hand sanitizer, rubber gloves, soap, thermometer, infrared thermometer Instruments, oximeters, sprayers, emergency transportation vehicles, emergency medicines, etc.

(3) Develop emergency measures for the occurrence of symptoms such as fever, fatigue, dry cough or dyspnea, isolation measures and emergency transportation routes for medical treatment, and designated hospital contact.

2. Work Arrangement for Resumption, Reproduction and Epidemic Prevention

(1) Departments at all levels of the factory shall collect statistics on the preparation of their personnel in advance and report to the human resources department. Before entering the factory, employees from outside the urban area and employees who have reworked in large epidemic areas, including related parties (including suppliers, logistics, business outsourcing, and dispatchers), must organize all medical personnel to check before entering the factory. On the first day of resumption of work, it is especially important to check the health of the entire staff.

(2) Remind employees to do self-protection and disinfection during the epidemic control period while at home and after resuming production.

(3) After all employees go to work, as long as any employee finds physical abnormalities, such as fever, fatigue, dry cough or dyspnea, etc., he must immediately report to the management, and immediately perform on-site disinfection and arrange for employees to go to the hospital for medical treatment and confirm the diagnosis Notify the company.

(4) All employees, outsiders, and visitors must accept the doorman's infrared temperature measurement before entering the factory. The doorman is responsible for recording the body temperature. If the body temperature exceeds 37.3 degrees Celsius, it is forbidden to enter and report to the factory and the docking person. Outsiders must also wear masks by themselves (the factory staff of long-term business parties can provide temporary preparation masks).

(5) Do a good job in registering and confirming foreigners. All foreigners must register at the gates, with their names, phone numbers, and whether they have been to Hubei recently. The quarantine staff reports to the enterprise on the situation of self-quarantine. According to the actual situation, the factory randomly checks the situation of home quarantine staff through Wechat QQ videos and other methods.

(6) Employees who commute by car or public transport must wear protective masks. They should use hand sanitizer to wash their hands immediately after getting off the bus. After using the commuter car, they must immediately disinfect and replace the seat cushion cover, and arrange for a special person to manage and inspect.

(7) Before resuming production, each factory organizes personnel to disinfect all sites of the factory once, and then every three days. The key areas include locker rooms, offices, domestic garbage storage sites, and smoking spots. Special persons are arranged to disinfect each morning and evening.

(8) Confirm the safety and hygiene of the cafeteria of each factory employee. The canteen is forbidden to purchase live poultry and fish meat without slaughter and quarantine, and it is forbidden to provide lettuce. Cutlery should be steam sterilized. Processing is separated from raw and cooked.

Restaurant service staff must conduct a health check before taking up their duties daily, take temperature measurements and retain test records, and must uniformly wear gloves, protective glasses, medical masks, and protective shoes during operations.

Disposable protective equipment must be discarded in a centralized manner. Repeated protective equipment must be centrally disinfected. Repeated use without disinfection is prohibited.

Tableware is uniformly distributed by service personnel. It is forbidden to fetch and take tableware by yourself. Do not use your own chopsticks and tableware to pick dishes from public bowls and plates. Meals are collected and divided by the cafeteria staff.

Food retention samples shall be implemented in accordance with regulations.

(9) Set disinfection hand sanitizer, soap and alcohol cotton balls or disinfection wipes in major places such as bathrooms and cafeterias. Employees are required to wash their hands before or after meals, or wipe their hands with alcohol cotton balls.

(10) Gatekeepers, service personnel, cleaning and greening personnel must wear masks, rubber gloves, and the above-mentioned protective supplies should be replaced daily.

(11) After the resumption of work, the factory will organize the inventory of protective supplies and calculate the recent usage, purchase in advance, and reasonable inventory. The material is distributed on demand as a daily protective material and emergency disposal material, and a special person is responsible when necessary.

(12) In their respective labor positions, non-person-to-person contact environments should wear masks; in frequent contact positions, and in closed jobs (control rooms, etc.) where centralized operations are required, wear masks and other protective equipment. It is forbidden to spit, wastes of protective masks and mouth and nose secretions are wrapped in tissue paper and put into special medical waste barrels designated by the factory.

(13) Each factory's workshops, conference rooms, offices and other densely populated places should be kept open and ventilated (excluding central air conditioning), and open and ventilated at least twice a day, 30 minutes each.

(14) During the epidemic prevention period, factories should temporarily cancel or control the number of people to participate in collective activities and large-scale meetings to minimize or stop business trips and parties. If necessary, report to and obtain consent from management at all levels.

(15) Don't believe or spread rumors. It is strictly forbidden to use social media to spread false information to create panic.

(16) For those who are inaction, slow, and disorderly, those who engage in formalism, bureaucracy, and those who conceal or fail to report the epidemic, they must be held accountable in a timely manner, and they must release a strong signal that they should pay attention to implementation and should not be lax.

Third, Key areas and recommendations for personal protection

1. What are the high-risk areas in the office (wear a mask)

New coronaviruses are mainly transmitted through droplets in the air. The air is not flowing, the density of people is high, and the places where people come and go frequently are high-risk areas.

By degree of danger:

(1) Elevator room

(2) Canteen / restaurant

(3) office

Highest danger: elevator room

The elevator room is a place where the air is extremely impermeable. Don't be superstitious about the "disinfected here" notes. Only a certain concentration of alcohol can dissolve the outer membrane of the coronavirus. However, alcohol is extremely volatile. Unless someone is arranged to disinfect alcohol in the elevator room every hour, and the danger in the elevator room is invisible, just after someone coughed or sneezed When you left, you thought you walked into the empty elevator room, but it was full of droplets, including your fingers pressing the elevator button.

Suggest:

(1) Be sure to wear a mask when riding the elevator.

(2) Conditional units must frequently disinfect the elevator rooms, especially the button area.

Second highest risk: canteen / restaurant

The area crowded with people queuing for meals or eating is the area with the highest pedestrian flow and the highest density.

Suggest:

(1) Take off your mask at the last minute to sit down and eat.

(2) Avoid face-to-face dining and avoid talking.

(3) Avoid group meals.

High Risk Three: Office

Where there is someone, there is a risk of infection.

Suggest:

(1) Wear a mask and maintain a moderate distance for conversation.

(2) Maintain good ventilation at all times.

(3) Perform necessary alcohol disinfection on door handles, keyboards, mice, stationery, and desktops.

2. Wash your hands frequently. Wash your hands frequently. (Three important things)

(1) Go to the unit and wash your hands the first time.

(2) Wash your hands before eating.

(3) I've been to the elevator, the high-risk area of ​​the canteen, come back and wash my hands.

(4) Come back out and wash your hands immediately.

(5) Wash your hands before touching your face, especially your nostrils and eyes.

3. Scientific alcohol disinfection

It doesn't make sense to spill it on yourself like a perfume. The key is to disinfect the parts and objects that our hands will touch. Such as mobile phones, door handles, elevator buttons, mouse and keyboard, bicycle handles, work permits, stationery, chairs, etc., depending on your actual situation, conduct screening and key disinfection. Alcohol should be sprayed on the covered objects and allowed to dry naturally without wiping.

Our company is dedicated to the sales and communication of springs and spring machines. If you have any intention, please contact us.
Name:Luoyang Xian Heng Spring Machinery Co., Ltd.
Email: marketing@springcoiling.com
Tel: 0086-379-62265677
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MODIFICATION OF THE SHORT SPRING CAN DAMAGE THE SHOCK ABSORBER, DO YOU KNOW THE REASON?

Many car owners may have experienced this: they want to reduce the height of the car by replacing the "short springs", and they can also improve the support of the car body during the change of line and cornering. However, it took a long time to modify the short spring. The shock absorber of the original car began to go wrong, either leaking oil or all kinds of abnormal sounds. Why does this happen?You need a good quality spring making machine.

There is no problem with retrofitting short springs, but the problem is that this involves a "spring and shock absorber matching" problem. The reason why the automobile shock absorber assembly can make the vehicle run smoothly and ensure sufficient filtering vibration capability is the function of the cooperation between the working stroke of the spring coiling machine and the stroke of the shock absorber movement. 

If the modified spring is much smaller than the original car spring, the telescopic stroke of the short spring will seriously limit the stroke of the shock absorber, resulting in the shock absorber not working in a reasonable stroke range, the shock absorption effect can not be properly played, shock absorption In addition, the shorter spring will make the shock absorber piston movement range lower than the lower part of the cylinder. When the big pit is encountered, the piston can easily “bottom out”; the bottom of the shock absorber is often subjected to severe pressure and will further causes oil leakage, and the top of the piston rod is broken.

Therefore, if only the spring is replaced during the modification, and the original vehicle shock absorber is retained, it is necessary to first confirm the K number of the original car spring, and then select the modified spring that is not much different from the original car spring K number. Some people will ask, what is the K number? The K number of the spring is an important parameter of the spring, which represents the hardness of the spring, which depends on the diameter of the spring wire and the spacing between each turn. Generally speaking, the thicker the wire and the closer the pitch is, the larger the K number, and vice versa.

By modifying the short spring to reduce the height of the car, the reduction is actually very limited. The height that can be reduced must be within 10% of the load range of the original vehicle shock absorber, that is, about 10~15mm; once this distance is exceeded, the service life of the original vehicle suspension will be greatly shortened. Therefore, in order to pursue the low-lying effect of the whole vehicle, it is better to replace the shock absorber and the spring.

When it comes to suspension modification, you have to mention "snap-hook suspension", which is a Hong Kong person's statement, which refers to adjustable height shock absorbers. The first twisted tooth suspension was popular in the modification of the chassis of the car. By adjusting the ground clearance and changing the vehicle's gravity distribution, it helps to improve the tire limit of the car. Nowadays, civilian modified vehicles have also begun to use a large number of twisted teeth for shock absorbers. The main reason is that it can change the height of the vehicle at any time. At the same time, it can adjust the damping force of the shock absorber and the adjustment of the number of springs K to help the vehicle cope with different conditions and ensure excellent handling.

Our company is dedicated to the sales and communication of springs and spring machines. If you have any intention, please contact us.
Name:Luoyang Xian Heng Spring Machinery Co., Ltd.
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Key Factors Affecting Quality During Spring Grinding

There are many places to pay attention to when producing springs. Any detail will affect the quality of the spring. After all, the details determine the success or failure. When springs need to be ground after they are produced, we cannot relax our vigilance and start with the following points and grasp the details to produce a good spring.

(1) The grinding wheel should be selected reasonably

Grinding wheel is coarse, the roughness of the grinding surface is coarse, and the production details of the grinding wheel particle are low. If the grinding wheel is too hard, the grinding surface will be burnt and the verticality is not good. There will be two grinding surfaces. The grinding wheel is soft, the sand particles fall off quickly, the life of the grinding wheel is short, and the perpendicularity and the parallelism of the end face are not good.

(2) Control of helix rise angle

When grinding the end face of a spring with a double-end grinding machine, in order to ensure the verticality of the spring, the size of the spring's rising angle is very important. When the size of the spiral lift angle is not consistent, the degree of grinding surface grinding, the thickness of the tip, and the verticality are greatly dispersed.

(3) A dedicated measuring tool is required during grinding

In order to ensure the quality of grinding, a certain number of special measuring tools should be equipped to ensure that workers can quickly and accurately measure the quality of the grinding spring in the self-test.

(4) Dressing of the grinding wheel

The dressing of the grinding wheel has different shapes, and the verticality after grinding is also different. If the grinding wheel disk is concave, the verticality of the grinding spring is good, but the grinding wheel is easy to wear and not used for a long time. The dresser can swing at an angle to make a concave wheel. If it is a parallel grinding wheel, this is the ideal state. This kind of grinding wheel has a long service life, few dressing times, and good verticality of grinding. If it is a convex-shaped grinding wheel, that is, the middle protrusion after the grinding wheel is trimmed. The verticality of the spring is not good, which is usually caused by the wear of the guide of the dresser. When the dresser is trimmed, it is necessary to repair the dresser in time. Fine grinding.

(5) Selection of grinding sleeve diameter and length

Grinding a spring with high verticality requires a clearance of 0.05-0.5mm between the spring and the sleeve, and a uniform clearance between the spring and the upper and lower grinding wheels.

(6) Grinding of the dresser guide rail

After the seal of the dresser guide rail is damaged, the sand will enter the dresser guide rail, causing wear of the guide rail. If the machine is used for a long time, the dresser guide rails will be worn. At this time, the dresser guide rails and sealing devices should be repaired in time, otherwise the knife phenomenon will occur, and the grinding wheel will have a convex shape after trimming, and the spring verticality is difficult to be polished.

(7) Prevent gaps during spring grinding

When the spring is ground, the gap is easy to produce a gap. The gap affects the verticality, load characteristics and free height of the spring. Therefore, the general grinding process of the spring is performed after the stress is tempered and tempered. Springs wound with annealed materials will have end gaps when they are coarsely ground. Springs rolled with cold drawn materials have a layer of residual compressive stress on the surface of the steel wire. After rough grinding, the balance of residual stress will cause end gaps. Springs made of annealed material produce gaps during rough grinding. A stress-relief tempering process can be added before rough grinding to eliminate residual cold drawing stress and solve the problem of end gaps.


Our company is dedicated to the sales and communication of springs and spring machines. If you have any intention, please contact us.
Name:Luoyang Xian Heng Spring Machinery Co., Ltd.
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Tel: 0086-379-62265677
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