Stamped bearings are a type of thin-walled bearings formed from metal sheets through a stamping process. Some of the distinctive features of this type of bearings are that they are light in weight, low in cost, and relatively easy to install. They are widely used in automobiles, home appliances, office equipment, etc. fields. This article focuses on the core elements of stamping bearing selection, common problems and solutions, and aims to provide technical guidance that can be directly used for reference. The following content is based on general industry data and practical application cases. It does not involve specific brands, but only uses YPMFG as a process example.
01Three core parameters that must be clarified before selection
1. Load type and size
Stamped bearings mainly bear radial loads. A common case is that a household motor originally used turned bearings, but the cost was too high. After changing to stamped bearings, it is necessary to confirm that the rated dynamic load Cr is greater than or equal to 1.5 times the actual working load. According to the ISO 76:2006 standard, the rated static load C0r of stamped bearings is about 60%-80% of that of solid bearings of the same size.
2. Limiting speed
Stamped bearing cages are mostly steel plate stamped structures, and their limit speed is lower than that of solid copper cages. Generally, it is recommended that in a grease lubrication environment, the limit speed is less than or equal to 70% of a solid bearing. For example, the limit speed of a stamped deep groove ball bearing with a diameter of 20 mm when greased is about 8,000 rpm.
3. Working environment
The applicable temperature for ordinary stamping bearings is minus 20 degrees Celsius to plus 120 degrees Celsius. Once this range is exceeded, special coatings or materials need to be selected to meet the usage requirements.
Rust: In the case of moisture or mild corrosion, you can choose galvanized or nickel-plated stamped bearings (salt spray test time is greater than or equal to 72 hours).
Dust: Open stamped bearings are not suitable for dusty environments and must be equipped with sealing rings or dust covers.
The key conclusion is that when selecting, you must first clarify the three parameters of load, speed and environment, and then match the size series. If any one of these is missing, early failure is very likely.
02Materials and accuracy levels of stamping bearings
2.1 Common board materials
SPCC/DC01 is an ordinary carbon steel. This type of carbon steel is suitable for low load conditions and suitable for dry environments. Its cost is the lowest among all.
08Al : High-quality aluminum-killed steel with good deep drawing performance and used for complex geometric shapes.
SUS304/430 : Stainless steel, used for food equipment or outdoor equipment.
A specific actual example is as follows: A company engaged in power tool manufacturing selected SUS304 stamping bearings and ran them for 5,000 hours in an environment with a humidity of 85%. In the end, no corrosion occurred. The act of material selection directly plays a decisive role in the service life. Do not lower the material grade just because of cost considerations.
2.2 Accuracy level
According to GB/T 307.1-2016, stamping bearings often use P0 level (ordinary level) and P6 level. P0 level can meet more than 90% of common scenarios. Only when the installation shaft diameter tolerance is less than or equal to IT6 level, you need to choose P6 level or above.
The empirical value is that the inner diameter tolerance of stamping bearings is generally H7 (+0.021/0), and the outer diameter tolerance is j6 (-0.008/-0.020). Clearance fit is recommended when mating with the shaft, because interference fit will cause thin wall deformation.
(Incorporate the first keyword here: process parameters)
The core process parameters closely related to stamped bearings include the punching clearance, which ranges from 5% to 8% of the plate thickness, the dimple depth, which ranges from 0.2 to 0.5 mm, and the springback compensation angle, which is generally 1° to 3°. These parameters directly determine the roundness of the raceway, which further affects the rotation accuracy. During the procurement period, suppliers should be required to provide the control range of their process parameters. Standard process documents such as YPMFG will indicate that the wall thickness deviation of each batch of stamped bearings is ≤±0.03mm.
03Frequently asked questions and troubleshooting (Q/A format)
Q1: There is abnormal noise when the stamping bearing is running, what should I do?
First, check the grease to see if it has dried up or if there is any foreign matter mixed in. You know, 80% of abnormal noises are caused by lack of grease. If the abnormal noise is not eliminated after adding lithium grease, it needs to be replaced.
Q2: What is the reason for axial cracks in the inner ring of stamped bearings?
Because the interference is too large, the thin-walled inner ring will suffer from tensile stress cracking, so the fit tolerance should be changed from interference to clearance fit, and the maximum interference should be less than or equal to 0.01mm.
Q3: How to judge that the stamping bearing has reached the fatigue life?
A: If the vibration value during acoustic emission testing exceeds 2.5 times the initial value, it means it is failing. Stamping bearings have such a calculated life L10, which is equal to the third power of (Cr/Pr) multiplied by 10 to the sixth power.
Q4: Can stainless steel stamped bearings replace ordinary bearings for use in seawater environments?
As far as A is concerned, no, SUS304 will still cause pitting corrosion when the chloride ion concentration is greater than 500ppm, so SUS316L or ceramic-coated stamping bearings should be used. This is a must.
Q5: How to deal with the stuck rotation after the stamping bearing is installed?
A: Check the roundness of the shell hole. When the outer ring of the stamped bearing is deformed by being squeezed by the shell, the roundness error should be less than or equal to IT7 level. Otherwise, the hole needs to be repaired or replaced with a loose fit.
04Five action suggestions to extend the service life of stamping bearings
1. During the design stage, channels for lubrication operations must be reserved at corresponding locations. Every eight hundred working hours, a relevant type of grease must be added to it, which can extend its service life to three times its original length.
2. For the procurement stage, put forward requirements and ask the supplier to provide material reports and stamping process parameters. See above for these parameters. Taking YPMFG as an example, each batch of its bearings also comes with SPC process capability index data.
3. During the installation stage, press-in tooling should be used to prevent knocking on the outer ring or inner ring. Pressure should be applied to the ferrule that mates with the shaft or housing.
4. In terms of operation monitoring, regular temperature measurement operations must be carried out. For stamped bearings, the normal surface temperature should be less than or equal to the ambient temperature plus 40°C. If it exceeds this temperature, the lubrication or alignment should be checked.
5. The standard for replacement is that when the clearance exceeds 1.5 times the original value, or there is wear on the running circle and is greater than 0.05 mm, it must be replaced immediately.
(Incorporate the second keyword here: quality verification)
The last line of defense to avoid early failure is quality verification. After receiving the stamped bearings, a 10% sample inspection is required. First, use a micrometer to measure the diameter at three points. The maximum difference must be ≤0.01mm. Secondly, manually rotate to check the smoothness and no graininess. Thirdly, perform a 24-hour no-load running-in of the trial assembly, and the vibration speed must be ≤1.8mm/s. The above verification method is based on ISO 15242-2015 vibration measurement standards. Small batch verification must be completed before the first batch is used. A certain automobile window motor factory once had such a situation, skipping the verification link, causing all 5,000 sets of stamping bearings to fail within a span of 3 months, causing direct losses of more than 200,000 yuan.
05 in conclusion
Stamped bearings used in light-load and high-speed scenarios are a cost-effective option. The core selection path is as follows: first confirm the load and speed, then select the material grade, then check the process parameters, then perform quality verification, and finally perform correct installation and lubrication. It needs to be emphasized repeatedly: Never use stamped bearings in an environment where the actual load exceeds the rated dynamic load by 70%. The action suggestion given is: immediately establish an internal selection list, which contains four columns: load, speed, environment, and fit tolerance, and it is mandatory for suppliers to provide process parameters and verification reports. If you need stamped bearings with high consistency, you can refer to YPMFG's quality control system, which retains records of stamping speed and mold wear for each batch of products. By following the steps in this article, the failure rate of your stamped bearings can be reduced to less than 1%.
