How to determine the wear level of Precision Ground Ball Screw?
Precision Ground Ball Screw, as a high-precision transmission component, is widely used in CNC machine tools, precision instruments and other equipment, and its wear condition directly affects the positioning accuracy and operational stability of the equipment. Regularly checking the wear of ballscrews is a key link to ensure the efficient operation and prolong the service life of the equipment. This article will introduce in detail how to scientifically and accurately check the wear of precision grinding ballscrews.
First, the common types of ball screw wear
Before understanding the inspection method, it is necessary to clarify the common types of wear of precision grinding ball screws in order to carry out targeted inspection work.
Raceway wear: this is the most common form of wear. Ball and screw raceway, nut raceway long-term contact operation, under the action of the load will produce contact stress, with the increase in the use of time, the raceway surface will gradually appear abrasion, manifested as increased surface roughness, scratches or pits, and in severe cases, fatigue spalling will be formed.
Ball wear: When the ball rolls in the raceway, it will not only wear the raceway, but also wear itself due to friction and impact, which may result in smaller diameter of the ball, scratches on the surface, and increased roundness error.
Thread wear: The threaded part of the screw and the threaded part of the nut will be worn in the long-term relative movement, which may lead to the increase of the thread clearance and affect the transmission accuracy.
End support wear: the end support structure (such as bearings) of the ball screw will also be worn during operation, which may lead to the increase of radial runout and axial runout of the screw, indirectly affecting the normal transmission of the screw.
Second, the preparatory work before the inspection
In order to ensure the accuracy and safety of the inspection results, the inspection before the need to make adequate preparations.
1. Equipment shutdown and safety protection: first of all, the installation of ball screw equipment shutdown, and cut off the power supply to ensure that the equipment is in a completely static state. For equipment with pneumatic or hydraulic systems, it is also necessary to release the system pressure to prevent accidental start-up causing personnel injury. At the same time, set up warning signs around the equipment to avoid the approach of unrelated personnel.
2. Clean up the working environment: clean up the debris, dust and oil around the ball screw to keep the working environment clean. Use compressed air to blow away the floating dust on the surface, and then wipe the surface of the screw and nut with a clean rag dipped in an appropriate amount of cleaning agent (e.g. kerosene, alcohol) to ensure that the actual condition of the parts can be clearly observed during the inspection.
3. Prepare inspection tools: According to the inspection requirements, prepare suitable inspection tools, mainly including:
Measuring tools: such as micrometers, percent tables, vernier calipers, laser interferometers, etc., used to measure the dimensional accuracy of the ballscrew, shape and positional tolerances.
Observation tools: such as magnifying glass, microscope (magnification is generally 10 - 50 times), used to observe the raceway, ball and other surface microscopic wear.
Auxiliary tools: such as wrenches, screwdrivers, etc., used to dismantle the parts that may hinder the inspection; there are grease guns, grease, etc., after the inspection can be lubricated and maintained on the screw.
4. Understand the equipment-related information: check the manuals, drawings and other information of the equipment to understand the model, specifications, rated load, service life, historical maintenance records and other information of the ballscrew, to provide a reference basis for the inspection work, and to clarify the key points and standards of the inspection.
Third, specific inspection methods
1. Appearance inspection
Overall observation: Observe the overall condition of the ballscrew with the naked eye, and check whether there are obvious deformation, bending, cracks and other phenomena on the surface of the ballscrew. Check whether the movement of the nut on the screw is smooth, whether there is any jamming, abnormal sound and so on.
Raceway and ball check: with the help of magnifying glass or microscope, carefully observe the surface condition of raceway and ball,the surface of raceway should be smooth and even, without obvious scratches, pits, fatigue flaking and other wear traces, if the surface of the raceway is found to have metal flaking debris, or obvious grooves, it means that the raceway is seriously worn; the surface of the ball should be free of scratches, corrosion, deformation and other conditions, and the size of ball should be uniform, you can place the ball on the surface to check whether it is smooth. The size of the ball should be uniform, you can take out the ball, use a micrometer to measure its diameter, and the standard diameter for comparison, if the diameter deviation is more than 0.001mm, indicating that there is wear and tear of the ball.
Thread inspection: Observe the engagement of screw threads and nut threads, and check whether there is wear, deformation, burr, etc. on the thread surface. Touch the thread surface with your finger to feel whether there is obvious unevenness, if so, it means that the thread is worn.
2. Dimensional accuracy check
Measurement of the diameter of the screw: use a micrometer to measure the outer diameter of the screw at different positions (such as the ends, the center), the measurement points should be evenly distributed, and each position should be measured 3 - 5 times, taking the average value. Compare the measurement result with the nominal diameter of the screw, if the deviation exceeds the permissible range (generally ±0.002mm), it means that there is wear or deformation of the screw.
Pitch Error Measurement: The laser interferometer is used to measure the pitch error of the ball screw. Install the reflector of the laser interferometer on the nut, move the nut along the axis of the screw, and record the pitch error values at different positions. According to the precision requirements of the equipment, determine whether the pitch error is within the permissible range, if exceeded, it means that there is wear and tear of the screw, affecting the transmission accuracy.
Gap Measurement: Measure the axial gap and radial gap of the ball screw.
Measurement of axial clearance: Put the probe of the meter against the end surface of the nut, push and pull the nut along the axial direction by hand, and read the maximum value of the meter, which is the axial clearance. Generally speaking, the axial clearance of precision ball screw should be controlled between 0.001 - 0.003mm, if the clearance is too large, it means that there is wear and tear of the screw or nut.
Measurement of radial clearance: Use the probe of the meter against the outer surface of the screw, gently shake the screw in the radial direction, and read the change of the value of the meter, i.e. the radial clearance. Radial clearance may be too large due to end support wear or screw bending.
3. Running status check
No-load running check: In the case of equipment power failure, manually rotate the screw, feel whether the rotation resistance is uniform, whether there is no jamming, abnormal noise and other phenomena. If there is obvious resistance change or noise during rotation, it may be caused by wear of raceway, damage of ball or entry of foreign matter.
Load running check: Observe the running condition of the ball screw under the normal running condition of the equipment. The vibration amplitude and frequency of the screw can be measured by the vibration sensor. If the vibration increases abnormally, it may be due to imbalance or poor fit caused by wear. At the same time, monitor the temperature changes in the operation of the screw, if the temperature rises abnormally (more than 15 ℃ above the ambient temperature), may be due to wear and tear exacerbate friction, resulting in increased heat.
Fourth, the judgment and treatment of the inspection results
1. Judgment of the results: According to the above inspection content, combined with the use of ball screw standards and the precision requirements of the equipment, the wear situation is judged. If all the indicators are within the permissible range, it means that the wear of ball screw is light and can be used; if one or more indicators exceed the permissible range, it means that there are different degrees of wear and tear of ball screw, and corresponding treatment is required.
2. Treatment measures:
For slightly worn ballscrews, maintenance can be carried out by replacing grease, adjusting preload, etc., in order to restore part of its performance. For ballscrews with more serious wear, such as obvious spalling of raceways, exceeding of pitch error, excessive gap, etc., the ballscrews should be replaced in time with new ballscrews, in order to avoid influencing the normal operation and processing accuracy of the equipments. For the case of end support wear, it is necessary to replace the corresponding bearings and other components, and readjust the support structure to ensure the normal operation of the screw.
Fifth, the importance of regular inspection
1. Timely detection of problems: regular inspection can timely detect the early wear of precision grinding ball screws, avoid further aggravation of wear, prevent equipment downtime due to screw failure, and reduce production losses.
2. Guarantee the precision of the equipment: through the inspection and the necessary maintenance treatment, it can guarantee the transmission precision of the ballscrew, ensure that the parts processed by the equipment meet the quality requirements, and improve the qualification rate of the products.
3. Extend the service life: reasonable inspection and maintenance can reduce the wear speed of ball screw, extend its service life and reduce the maintenance cost and replacement frequency of the equipment.
In summary, checking the wear and tear of Precision Ground Ball Screwneeds to be carried out in accordance with the standardized process, from the preparatory work to the specific inspection methods, to the results of the judgment and treatment, each link is crucial. Only regular and scientific inspection can ensure that the ballscrew is always in good working condition and provide reliable guarantee for the efficient and precise operation of the equipment.
Contact Us
📞 Phone: +86-8613116375959
📧 Email: 741097243@qq.com
🌐 Official website: https://www.automation-js.com/
