Discussion on the application of deep groove ball bearing finished cleaning and water-based cleaning agent

- Aug 21, 2019-

Today we will discuss the application of deep groove ball bearing finished cleaning and water-based cleaning agent with ZBF bearing.

https://www.deepgroveballbearings.com/deep-groove-ball-bearing/single-row-deep-groove-ball-bearing/6000-6200-6300-rs-series-bearing.html


At present, many enterprises have cleaned the finished products of deep groove ball bearings with water. For the application of water cleaning, the first question that everyone is worried about is how to deal with and solve the problem of rust prevention. Secondly, how is the cleaning effect?


In general, as far as the cleaning of the liquid is concerned, although the mechanism of the cleaning is different, it is undoubted that the cleaning can be carried out. But in terms of the overall cleaning effect, it is not only a problem with the water-based cleaning agent itself.


First, the main differences between aqueous cleaning and conventional kerosene cleaning are:


The cleaning of kerosene is mainly to dilute, soften or dissolve the oily dirt on the surface of the workpiece, and then circulate and filter to wash away all kinds of dirt. The oily dirt dissolved in the kerosene is mixed with the kerosene to make the kerosene become more and more viscous, the color will be deeper and deeper, and the content of fine solid impurities suspended in the kerosene is higher and higher. This is the root cause of secondary pollution.


The cleaning of the aqueous solution is mainly to remove the dirt, but the performance of the molten or emulsified oily dirt is more or less always, and the various adhered and peeled dirt is also washed after the circulation filtration. The cleaning liquid prepared by the water-based cleaning agent mostly has a natural separation of oily dirt to float on the surface of the cleaning liquid, and the oily dirt can be isolated and removed by a certain method. The fine solid dirt remaining after filtration is also easier to sink after standing.


For the cleaning of bearings, it will involve: the properties of the dirt carried by the bearing, the cleaning medium used, the cleaning process and method, the corresponding cleaning equipment, and the necessary management. Especially when preparing to use kerosene instead of kerosene, we must fully understand our current cleaning process. The following is a discussion of the corresponding aspects.


First, the bearing is contaminated


The dirt attached or adhered to the assembled bearing usually includes: fine metal powder, abrasive particles, super essential oil powder, various oil stains attached during the operation of the equipment, and the workpiece is stored and transported. Anti-rust components and dust, garbage, etc. in the air.


As for the bonding force between the dirt and the bearing surface, there are roughly: mechanical bonding force, intermolecular force, chemical bond force, and electrostatic bonding force.


The dirt carried by the bearings is also different during different cleaning stages. According to the usual cleaning process:


During the cleaning stage of the parts before assembly, the object to be cleaned is mainly the grinding debris and abrasive micro-powder brought by the grinding and super-precision adhered in the ferrule sealing groove, as well as the ultra-essential oil, mechanical oil and channel inspection. Under the scratching grease and anti-rust liquid (oil), dust and other pollutants in the warehouse turnover. It is separated and detached from the surface of the ferrule by ultrasonic cleaning, and is separated from the surface of the ferrule during filtration and circulation scouring of the cleaning liquid.


The rough washing stage of the finished product is mainly the residual cleaning liquid after the steel ball and the retainer are cleaned (usually using kerosene), and also includes the anti-rust oil and the metal-containing waste attached to the parts without cleaning. There is also a fine iron slag powder which is generated by deformation friction when the claws or rivets are riveted. This stage can be carried out by using ultrasonic waves first, followed by rinsing or a combination of the two.


In the finishing stage of the finished product, there is generally a washing and washing that rotates the bearing, and the fine garbage attached between the steel ball and the ball pocket is brought out during the rotation of the bearing. More importantly, it replaces the cleaning liquid brought in before cleaning. First, the filtration precision is higher, and the composition of the cleaning liquid is relatively pure, especially the cleaning liquid which directly acts as an anti-rusting effect. The cleaned bearings are optimally cleaned.


Second, the cleaning fluid filtration accuracy problem


Cleaning fluid (oil or water) has been used for a long time in circulation filtration, but the current understanding believes that regardless of the level of cleaning, the front filtration accuracy can be lower, and the subsequent filtration accuracy is higher than the previous one. It seems to be a more washable. The clean process, in fact, there may be some misunderstandings here.


Filtration can only filter out particulate waste, and there is nothing that can be done on substances that can be dissolved in the cleaning solution.


For example, the original kerosene cleaning is divided into 4 stages: the filtration precision is 5 μm - 3 μm; 3 μm - 1 μm; 3 μm - 0.5 μm; 0.5 μm - 0.2 μm.


Imagine that the bearings in the first stage contain the most garbage and oil. The viscosity of the cleaning solution in use is also larger, and the impurities contained are more. Although the cleaning liquid is filtered during recycling, if the filtration accuracy is relatively low, Then there are still a lot of unfiltered garbage that will continue to impact the inner working surface of the bearing. The garbage brought in this process will cause friction damage to the internal parts of the bearing. At the same time, it will be attached to the bearing and taken to the next level for cleaning.


The total amount of dirt carried by the bearings to be cleaned is constant. If the same target accuracy (eg 0.2 μm) is used for filtration from the first stage, the damage caused by the garbage during the cleaning process is greatly reduced. Of course, the first level of filter replacement will be more frequent, but the latter will be less.


In fact, we have changed the first stage to 5μm → 3μm → 1μm → 0.2μm, and the latter directly to 0.2μm (Note: the filtration accuracy depends on the bearing cleaning requirements). The cleaning of each stage is cleaned with a cleaning solution with a high cleanliness of 0.2 μm. As a result of reducing the secondary pollution during the cleaning process, the damage caused by the garbage in the cleaning process is greatly reduced, and the cleaning can be appropriately reduced. The number of levels.


In our current automatic line bearing cleaning, kerosene and water are only used in two sections, and the cleaning effect is quite satisfactory.


Reasonable selection of filtration accuracy, reasonable configuration and application of the filtration system will directly affect the level of cleanliness of the finished bearing, thereby improving the bearing sound.


Third, the prevention of secondary pollution


Regardless of the cleaning fluid used, it is desirable to avoid secondary pollution during the cleaning process, and to avoid the dirt that has already been washed back to the bearing and cause damage.


First, the demagnetization process before cleaning is indispensable. First, the demagnetization facilitates the shedding of the iron particles, and the iron particles are prevented from being adsorbed again. For bearings with different accuracy requirements, it is essential to stipulate strict residual magnetic standards, and cannot meet the requirements of the requirements specified by the general standards.


Once the soluble dirt on the cleaned bearing is dissolved and mixed in the cleaning solution, it is generally difficult to separate it easily during use. Especially with kerosene cleaning, all kinds of oils and fats will be melted in it, even if it is mixed with water, it can not be completely deposited to the bottom, because kerosene can be incorporated into a certain amount of water. Once the water is wrapped by kerosene to the bearing surface, it can easily cause rust.


Among the used water-based cleaners, the different cleaning agents vary widely. Some water agents, like kerosene, will dissolve the soluble dirt in the cleaning solution, making the cleaning solution more and more turbid. Some brands of cleaning fluids can naturally float oily dirt separated from the bearing during the operation, so it is easy to separate oily dirt. The cleaning agent with oil-water separation function reduces the risk of secondary pollution and extends the service life of the cleaning solution. In use, we only need to replenish it before the liquid level drops to the lower limit. It is not allowed to change regularly.


Fourth, the cleaning method problem


Both the bearing parts before assembly and the bearings after assembly need to be cleaned. In addition to the selection of a suitable cleaning agent, the method of cleaning is also critical. It is often believed that more cleaning times will definitely result in better cleanliness, as well as stronger ultrasonic waves, longer time, higher flushing pressure, faster rotation during flushing, etc. If not properly selected, it will be counterproductive.


First, there are more stages to clean, and there are usually 4 to 5 levels in the industry.


The purpose of ultrasonic cleaning is obviously to make the dirt adhering to the inner and outer surfaces of the bearing and the retainer, including soluble and solid, loose, dissolve and separate from the bearing.


Since the production of bearings is basically in the form of a pipeline or a pipeline, the flow speed of the parts or finished products is relatively fast, and the time for the dirt to adhere to the bearing surface is relatively short, so it should be easier to clean from the bearing surface. Even if some of the relatively strong dirt adheres, it is easily separated from the bearing after demagnetization and ultrasonic waves. Moreover, the bearings are substantially free of deep and blind holes, and the ultrasonic waves are easily applied to all surfaces.


After the bearings are cleaned by ultrasonic waves, the dirt has been separated, emulsified or dissolved from the surface of the bearing. After the action of the flowing cleaning fluid, the bearing has been relatively clean. The rest is mainly that the seal groove and the gap between the retainer and the steel ball also contain a small amount of dirt that is not easily carried away by the liquid flow.


In the next cleaning, the bearings are sprayed or rinsed from different directions to remove loose dirt left in the crevices and grooves after ultrasonic cleaning.


Of course, if it is cleaned with kerosene, the oil contained in the dirt on the bearing, including the steel ball and the rust preventive oil on the surface of the retainer (if it has not been cleaned beforehand), will dissolve in the kerosene and change with time. The concentration of the miscellaneous oil will increase. These miscellaneous oils can not be separated and removed during the cleaning process, so that the residual surface of the bearing after the final cleaning will have more miscellaneous oil components, so consider the final cleaning kerosene turbidity. Therefore, the frequency of kerosene replacement will be much larger than that of the aqueous cleaning solution that can separate oil and water.


Second, the cleaning method that improves the filtration accuracy step by step is not ideal, as already mentioned.


The third is the consideration of the flow direction of the cleaning liquid in the ultrasonic cleaning tank.


Under the action of ultrasonic waves, the dirt has been separated from the bearing surface. In order to carry away the cleaned dirt, the cleaning liquid of the ultrasonic cleaning tank is a flowing liquid which is recycled after being filtered. The flow direction should be that the clean cleaning fluid flows from the bearing area to the bearing cleaning, and the other is the opposite direction of the moving bearing in the ultrasonic cleaning machine, so that the cleaned dirt can be effectively taken away. Turbulence is generated in the cleaning area.


Ultrasonic cleaning is the use of ultrasonic cavitation explosion to strongly wash the surface of the bearing. Thousands of atmospheric pressure stamping waves destroy insoluble dirt and disperse them in the cleaning solution. If the cleaning accuracy of the cleaning solution is low, the washed dirt Can not be taken away in time, the solid particles contained in the cleaning fluid around the bearing will also hit the bearing surface with great force. If the cleaning time is too long and the power is too strong, it will hurt the steel ball. The channel surface affects the low noise level of the bearing.