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Quality inspection

national standard

1. National standard for vibration acceleration (commonly known as Z standard)

This standard was formulated early. The quality level of bearings is determined by measuring the vibration acceleration value when the bearings are rotating. It is divided into three quality levels: Z1, Z2 and Z3 from low to high. At present, domestic bearing manufacturers are still using the vibration acceleration value to measure the quality of bearings, which simply reflects the fatigue life of bearings.

2. Vibration speed standard (commonly known as V standard)

Since the original vibration acceleration standard has not been abolished, this standard is based on the standard issued by the Ministry of Machinery Industry, which is formulated by referring to European standards and combining with the actual situation and needs of China, and divides the quality level of bearings by detecting the vibration speed of bearings (equivalent to the national standard). It is divided into five quality levels: V, V1, V2, V3 and V4. The quality grades of various ball bearings from low to high are V, V1, V2, V3, V4; The quality grades of roller bearings (cylindrical and conical) are V, V1, V2 and V3 from low to high.

It reflects the quality of the bearing by detecting the vibration b velocity of the bearing in different frequency bands (low frequency, medium frequency, high frequency). It can be roughly analyzed whether there are geometric dimension problems (such as steel ring ellipses), quality problems of raceways/rolling elements, and quality problems of cages. Compared with the vibration acceleration, the bearing quality has been significantly improved. At present, domestic bearings exported to Europe, China's military and aerospace industry all carry out bearing quality inspection in accordance with this standard. At the same time, it provides a feasible means to detect the quality of bearings imported from Europe and identify counterfeit bearings.

There are two standards for bearing quality inspection in parallel, while bearings with high "Z" quality level may not have good quality performance when inspected with "V", and there is no corresponding relationship between the two. This should be paid special attention to in the quality inspection of bearings.

Quality discrimination

We usually identify the quality of equipment bearings from the following aspects:

1. Whether the outer package is clear

Generally, brands produced by regular manufacturers have their own special designers to design external packaging, and arrange factories with qualified production conditions for production. Therefore, the packaging of products, from lines to color blocks, should be very clear and unambiguous.

2. Whether the steel print is clear

Each bearing product will be printed with its brand words, labels, etc. on the bearing product body. Although the font is very small, the products produced by formal manufacturers use steel printing technology to print, and they are embossed before overheating treatment. Therefore, although the font is small, it is deeply concave and very clear. In general, the font of counterfeit products is not only vague, but also floating on the surface due to rough printing technology. Some can even be easily erased by hand or the manual marks are serious.

3. Whether there is noise

Hold the inner sleeve of the bearing with the left hand, and rotate the outer sleeve with the right hand to and fro slightly to hear if there is any noise during the operation of the bearing. Due to the backward production conditions of most counterfeit products and completely manual workshop operation, it is inevitable that impurities such as dust and sand will be mixed into the bearing body during the production process, so there will be noise or unsmooth operation when the bearing rotates. This is the key to judge whether the products are from the brand products of regular manufacturers with strict production standards and machine operation.

4. Surface

Whether there is muddy oil stain on the surface requires special attention when purchasing imported bearings. As there is still a certain gap between domestic anti rust technology and foreign advanced manufacturing countries, it is easy to leave thick oil stains when carrying out anti rust treatment on the bearing body. When touching the bearing body with hands, it feels sticky. However, there is almost no trace of anti rust oil on the bearing imported with original packaging from abroad. According to the insiders, a particularly careful person can smell a special smell on imported bearings, which is the smell of rust preventative oil.

5. Whether the chamfer is uniform

The so-called chamfer of the bearing is the junction of the horizontal and vertical surfaces. Due to the limitation of production technology, the counterfeit bearing products are not satisfactorily processed at these corners, which can be easily identified.

6. Packaging

Bearing packaging includes inner packaging and outer packaging

After the bearing is manufactured and inspected as qualified, it shall be cleaned and rust proof, and then put into the inner package to achieve the purpose of waterproof, moisture-proof, dust-proof, impact proof, maintaining the quality and accuracy of the bearing, and facilitating the use and sales.

The inner packaging of bearings is divided into three categories according to the rust prevention period:

① Short rust proof packaging: the rust proof period is 3-6 months. It is applicable to bearings that are shipped in large quantities to the same subscriber and put into use in a short time. By agreement of both parties, simple packaging is adopted based on the principle of convenient use.

② General rust proof packaging: one year rust proof period, suitable for general purpose bearings.

③ Long rust proof packaging: two years rust proof period, suitable for special and precision bearings.

The inner packaging materials of the bearing include polyethylene plastic cylinder (box), kraft paper, plain and corrugated polyethylene composite paper, paper box, polyethylene or polyethylene plastic film, nylon fastening belt or plastic braided fastening belt, waterproof high-strength plastic belt, linen bag, etc. The above materials shall be qualified in the corrosion resistance test.