CNC Knowledge: Using grinding fluid on grinders

Most grinding processes involve parts with relatively high precision and roughness. The grinding fluid used should have the following functions:

1) Cooling function. Grinding fluid should have better cooling function than other machining fluids. It can remove a lot of heat from the grinding area during processing, reduce the grinding temperature, improve the durability of the grinding wheel and improve production efficiency.

2) Lubrication function. When grinding, the grinding wheel is subjected to strong working pressure during processing. The grinding fluid can enter the small gap between the grinding wheel and the workpiece surface, forming a very thin adsorption film, which reduces the friction factor, prolongs the life of the grinding wheel and improves the finish of surface of the room.

3) Cleaning function. If the chips generated during grinding and the sand particles rejected by the grinding wheel cannot be removed quickly, they may attach to the workpiece and the grinding wheel. Affects part accuracy and surface finish. Therefore, the grinding fluid must have good cleaning performance.

4) Anti-rust function. If the grinding fluid cannot provide good anti-rust function, it may cause corrosion during workpiece processing, resulting in the product being scrapped. Therefore, a grinding fluid with certain anti-rust properties should be selected during grinding.

Comparing the lubrication effects of using multiple grinding fluids with dry grinding, it can be found that the use of grinding fluids has good lubrication effects. During high-speed operation, significant friction occurs between the grinding wheel surface and the grinding wheel surface. workpiece. The pressure of the grinding process is very high, and the maximum temperature can reach more than 1000°C. If the grinding fluid used at this time cannot perform its good lubrication function, it will cause significant wear of the grinding wheel and reduce the machining accuracy and surface finish.

In addition, whether the grinding fluid can completely penetrate the grinding area directly affects the cooling and lubricating effect. During the grinding process, whether it is internal and external cylindrical grinding or surface grinding, if the position of the nozzle of the grinding fluid is improperly placed and the grinding fluid is poured into the wrong direction, the grinding fluid will be blocked due to the huge airflow generated. by the high speed rotation of the grinding wheel. It enters the grinding area, so it cannot be cooled in time during the grinding process. At this point, the grinding fluid has no cooling effect on the grinding heat of the workpiece. The grinding area, and can only reduce the overall temperature of the room. There are also several negative issues associated with the use of grinding fluid, such as increased grinding processing costs, environmental issues, and effects on operator health.

When grinding, using a suitable grinding fluid often has a greater effect on improving surface finish than reducing grinding thickness. In order to ensure the optimal functioning of the grinding fluid, to truly implement its four major functions and to play its role, the following points must be reinforced:

1. Make sure the grinding fluid is not corrupted or deteriorated.

1) Reasons for corruption and deterioration of grinding fluid

Corruption and deterioration of grinding fluid are the result of rapid reproduction of microorganisms under certain conditions, causing biochemical changes in the grinding fluid. Microorganisms responsible for spoilage include fungi, bacteria and yeast. These fungi can be widely found in the atmosphere, soil, rivers, natural objects and elsewhere. The following representative bacteria are often found in deteriorated and corrupted grinding fluids:

has. Trichobacillus aeruginosa: one of the main bacterial genera responsible for the corruption of grinding liquid.

b. Sulfate-reducing bacteria: This is another major bacterial genus responsible for the odor of the grinding liquid. It reproduces under anaerobic conditions and presents rust tumors. Under the influence of scale, it can reduce sulfate radicals, generate hydrogen sulfide, and emit odors that corrode iron.

c. Yeast: Powerful enzymes are produced in bacteria, making the grinding liquid sticky and putrid.

2) Conditions for rapid reproduction of microorganisms

has. Sufficient nutrient sources: The grinding fluid provides sufficient organic matter (carbohydrates, fatty acids, fatty alcohols, etc.), minerals and trace elements, nitrogen compounds (organic nitrates, etc.) and sulfur compounds for the reproduction of microorganisms, phosphorus, etc.

b. Oxygen: aerophilic bacteria will produce a slight odor, anaerobic bacteria will produce a foul odor, and facultative anaerobic bacteria will produce a slight odor.

c. Temperature: Bacteria tend to breed between 30 and 37 degrees and mold between 20 and 30 degrees.

d. pH value: Bacteria reproduce easily at pH 7.0 to 8.5, mold reproduce easily at pH 4.5 to 7.0, and bacteria and mold reproduce at pH > 9 with the lowest probability.

3) The phenomenon of corruption and deterioration of the grinding fluid

has. Slightly rancid.

B. The color of the liquid is gray-brown or pink (iron ions are precipitated), but it should be distinguished from excessive grinding materials.

c. A sudden change in pH, usually a rapid decrease after pH < 8, and the pH value of some synthetic solutions increases.

d. Viscosity increases and even gelatin precipitates.

e. Demulsification and stratification of the emulsion.

f. The consequences of rust and reduced cutting performance.

2. Ensure good management of the grinding fluid

1) The original solution must be managed to avoid exposure to extreme cold and long-term storage. Keep it above 5 degrees Celsius in winter and avoid direct sunlight in summer. It is best to use it within three months. Otherwise, the emulsified oil will be demulsified at low temperatures and cannot be restored.

2) Concentration management of working fluid preparation The concentration of working fluid is the basis for giving full effect to the function of grinding fluid. If the concentration is too low, it will affect the grinding function. If the concentration is too high, it will also affect the normal performance of the function. From the point of view of anticorrosion, it is better to increase the concentration appropriately. A large number of facts show that when the concentration of grinding fluid is 2-4%, microorganisms reproduce most quickly. 5 to 10% is better. In concentration management, if conditions permit, it makes sense to implement a liquid supply system or centralized preparation or special personnel preparation. The minimum requirement is that you cannot simply add water, add no or less original solution and not measure the preparation.

Improved grinding fluid corruption and odor

(1) When replacing a new fluid, carefully clean the fluid tank, pipes and machine tools.

If it is not cleaned or cleaned thoroughly, especially if there is corrupted grinding fluid before changing the fluid, it will become corrupted within a few days after changing the fluid. The entire cleaning process before changing the fluid:

1. Dispose of liquid waste.

2. Remove grinding debris, mud, rust and scale from the grinding fluid tank walls and bed surface, then clean the tank with water.

3. Use system cleaning agent to clean the box wall and bed surface to remove oil stains, and circulate the pipes for 3 hours to drain the cleaning fluid.

4. Use low concentration grinding liquid and bactericide, circulate for more than 1 hour, and wipe the box wall and bed surface for sterilization.

5. Prepare and add new liquid. Use a clean water source (tap water) and sterilize water for preparation if necessary. The concentration of the grinding liquid is prepared between 5-10% and a sugar is used as a measuring tool.

(2) Management of the grinding fluid used

1. Keep clean: prevent foreign bodies from entering, wash hands and cotton gauze without abrasive liquid, etc.

2. Quickly remove wear debris.

3. Start the machine and circulate the grinding liquid for 1 hour every day: preferably 0.5 hours in the morning and 0.5 hours in the afternoon.

4. Check the pH value of the cutting fluid frequently. When the pH value is lower than 9, add new liquid and tap water in time.

5. After the grinding liquid is consumed, add liquid and water in time.

6. Develop a replacement cycle based on work hours and seasonal changes. Do not wait until the grinding fluid is corroded before replacing it. Corruption of grinding fluid will impact the grinder, workpiece material, environment and operator. It can also affect the lifespan and operation of the new one. fluid.

7. When the pH value is lower than 8, the original solution, fungicide and pH adjuster should be added according to site conditions.

Thanks to the replacement of the new fluid and the strict management of the new fluid used, the grinding fluid no longer has any odor.

In summary, the rational use of grinding fluid can improve tool life and surface finish, ensure that liquid waste is treated after use, and meet environmental protection requirements, and its ingredients must not be harmful to humans. health. Nowadays, the key development direction of cooling and lubrication methods for grinding processing is the development of non-polluting grinding fluids. In the process of continuous construction and economic development in Haixi, environmentally friendly grinding fluids will surely develop faster and be more widely used in grinding mill processing.