Method for managing a coolant supply system for machining equipment

Abstract

In machining, the number density of fine bubbles generated in the coolant can be easily and inexpensively confirmed in-line without interrupting the process. [Solution] This invention provides a method for managing a coolant supply system for a machining center, which involves plotting measurement data of the number density of fine bubbles generated in the coolant against the airflow rate to the fine bubble generator in advance, and then performing machining while monitoring the airflow rate based on that data to determine the number density of fine bubbles in the coolant in-line.

Description

Technical Field

[0001] The present invention relates to a method for managing a coolant supply system for a processing machine.

Background Art

[0002] In machining, by using a fine bubble coolant in which fine bubbles are generated in the coolant, it is known to contribute to improving productivity, such as extending the life of drills and grindstones, reducing warping of workpieces, and improving machining speed.

[0003] Thus, in the machining site, since the production speed is improved by using the fine bubble coolant, if the generation of fine bubbles stops or decreases, there is a risk of grinding burn and deterioration of the warping of the workpiece. Therefore, there have been many demands to confirm whether the fine bubbles generated by the fine bubble generator are sufficient and how much longer they can be used.

[0004] In particular, in a fine bubble generator of a micropore method that supplies compressed air to a liquid through a porous body, the porous body becomes clogged as it is used, so that the generation of fine bubbles becomes insufficient.

[0005] The number density of fine bubbles (the number of fine bubbles per unit volume of coolant) can be confirmed by using a dedicated measuring instrument, but this requires stopping the process each time for measurement, resulting in a decrease in production efficiency. In addition, since chips and dirt are mixed in the coolant for the processing machine, it is necessary to measure after removing the chips and dirt, significantly reducing the production efficiency.

[0006] Furthermore, since this dedicated measuring instrument is expensive, it is not practical to introduce it at all machining sites.

[0007] Therefore, in processing plants using micropore-type fine bubble generators, there was a need for an inexpensive and simple method to confirm the number density of fine bubbles necessary for improving processing efficiency, and whether or not such fine bubbles were being generated.

[0008] In recent years, various studies have been conducted on the correlation between the amount of bubbles generated and various parameters.

[0009] For example, in a Venturi-type bubble generator, the bubble generation state is sometimes measured using a differential pressure gauge. Patent Document 1 discloses a microbubble generator that can stably generate a sufficient amount of microbubbles by maintaining a pressure difference of 0.1 MPa or more across both ends of the microbubble generator.

[0010] Furthermore, Patent Document 2 discloses a fine bubble generator that effectively generates microbubbles based on the flow velocity of a liquid passing through a porous material. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2011-056436 [Patent Document 2] International Public Gazette WO2020 / 004653 [Overview of the project] [Problems that the invention aims to solve]

[0012] In a venturi-type bubble generator like the one described in Patent Document 1, the water pressure of the coolant can be checked using a differential pressure gauge installed upstream of the throttling inside the generator, and this can be used as one of the indicators for determining the fine bubble generation status.

[0013] However, micropore-type fine bubble generators lack internal throttling, and no matter how much the coolant pressure is increased, the phenomenon of natural air intake from the outside does not occur. Furthermore, since there is almost no pressure difference before and after the passage of the liquid, it is not possible to determine the fine bubble generation status by measuring the differential pressure of the coolant alone. Moreover, Patent Document 1 does not mention the number density of fine bubbles that improve processing efficiency.

[0014] Patent Document 2 describes a method for generating fine bubbles by passing a liquid through a porous body. However, in a machining environment, it is difficult to maintain a constant fluid velocity and the required flow rate for machining cannot be met, making it impossible to guarantee a uniform number density of fine bubbles in the coolant. Furthermore, while there is a description of the amount of fine bubbles generated, there is no indication of its correlation with the force applied to the tool.

[0015] Furthermore, while effective fine bubble generation conditions have been studied as described above, management methods for predicting when to replace the porous material of a fine bubble generator or when to perform maintenance have not been considered.

[0016] Furthermore, while the number density of fine bubbles directly affects the effect of improving machining efficiency, there has been little research on the relationship between the number density of fine bubbles and the change in tool machining resistance.

[0017] Therefore, in order to determine whether the number density of fine bubbles in the coolant used during processing was sufficient, the inventors diligently investigated based on their own knowledge of fine bubbles and processing resistance, and found that there is a correlation between the air flow rate and the number density of fine bubbles generated in a micropore type fine bubble generator. The present invention reveals the number density of fine bubbles that improve processing efficiency, and provides a method for managing a coolant supply system that allows for inexpensive and simple confirmation of the number density of fine bubbles generated in the coolant in-line during machining without stopping the process.

Means for Solving the Problem

[0018] The present invention solves the above problems by the following steps. A fine bubble generator attached to the coolant piping path for a processing machine, having an air flow meter provided in the air introduction path to the fine bubble generator, generating air into the coolant through the fine bubble generator, and supplying the coolant containing fine bubbles to the processing point. In a method for managing a coolant supply system, means for measuring and plotting the number density of fine bubbles generated in the coolant with respect to the air flow rate flowing into the fine bubble generator in advance; a step of determining, based on the plotted data, an air flow rate at which the number density of fine bubbles in the coolant becomes 100,000 or more per mL as a threshold value; a step of setting the air flow rate to be above the threshold value and performing processing; when the value of the air flow meter during processing drops below the set air flow rate at the start of processing, or when it becomes less than the threshold value, including performing maintenance on the fine bubble generator. A method for managing a coolant supply system for a processing machine.

Advantages of the Invention

[0019] The present invention clarifies the correlation between the number density of fine bubbles and the processing resistance applied to the tool in the micropore method, and can confirm the state of fine bubbles inexpensively and simply without using a special measuring device and without stopping the process.

Brief Description of the Drawings

[0020] [Figure 1] Schematic diagram of the coolant supply system according to the present invention [Figure 2]Graph of the number density of fine bubbles against airflow rate in this embodiment [Figure 3] A graph showing the grinding resistance for each number density of fine bubbles. [Modes for carrying out the invention]

[0021] The fine bubble generator according to the present invention can use a microporous type fine bubble generator that generates fine bubbles by supplying compressed air to a liquid through a porous body. As the porous body member, ceramic filters and other appropriate materials can be used.

[0022] Furthermore, in this application, "fine bubble" refers collectively to bubbles with a diameter of 100 micrometers or less.

[0023] The fine bubble generator is installed in the piping path for the processing machine's coolant. Air is supplied to the fine bubble generator using a compressor or the like, and fine bubbles are generated in the coolant through the porous material inside the fine bubble generator. As shown in the schematic diagram in Figure 1, the air flow rate can be measured and displayed by installing an air flow meter in the air introduction path to the fine bubble generator.

[0024] First, as shown in Figure 2, the number density of fine bubbles supplied to the coolant is measured and plotted against the airflow rate of the fine bubble generator used.

[0025] The porous material can be dry, semi-wet, or wet when acquiring data, but the closer it is to the state of the porous material during processing, the better.

[0026] Semi-wet refers to a state of equilibrium within the porous material, where the pressure of the incoming air and the pressure of the flowing coolant are balanced. If the operation is carried out without stopping the airflow from the start to the end of processing, and there is sufficient time for the porous material to dry before the next processing, it is preferable to obtain data from a state where the porous material is dry.

[0027] On the other hand, if the airflow is stopped during processing, or if the next processing step is started without allowing the porous material to dry, the equilibrium between air and coolant is disrupted, and the material becomes completely wet. In such cases, it is preferable to obtain data on the porous material in its wet state.

[0028] Any air flow meter capable of measuring flow rate is acceptable, but one with higher measurement resolution is preferable. In particular, because the flow rate changes slightly due to capillary action as the coolant passes through the porous material, and due to the adhesion of dirt and contaminants from the coolant, it is even better if the meter has a resolution that can measure in units of 0.01 L / min down to a range close to 0 L / min.

[0029] Furthermore, according to the inventors' studies, using a thermal flow meter is most preferable. Flow meters are broadly classified into "thermal," "area," and "propagation time difference" types based on their measurement principle. Area and propagation time difference flow meters measure the actual flow rate flowing through the measurement section, but thermal flow meters, even when using compressed air, allow for the confirmation of a value converted to the air flow rate generated in the coolant after being released into the atmosphere. Therefore, errors are less likely to occur when correlating with the number density of the generated fine bubbles. In microporous fine bubble generators that generate fine bubbles through a porous material, compressed air is required, so using a thermal flow meter is preferable because it makes it easier to confirm the correlation with the number density of fine bubbles.

[0030] The number density of fine bubbles can be determined, for example, by measurement using image analysis.

[0031] The airflow rate should be between 0.05 L / min and at least 0.1 L / min, and data on the number density of the supplied fine bubbles should be obtained.

[0032] In machining, the number density of fine bubbles in the coolant is an important parameter. As mentioned earlier, in the field of machining, it is known that generating fine bubbles in the coolant contributes to improved productivity by extending the life of drills and grinding wheels, and reducing workpiece warping. This is because coolants containing fine bubbles reduce machining resistance, especially grinding resistance.

[0033] Figure 3 shows a graph of the number density of fine bubbles and grinding resistance. The inventors investigated the correlation between the number density of fine bubbles and grinding resistance and found that when the number density of fine bubbles is 100,000 / mL or higher, it is effective in reducing processing resistance.

[0034] Grinding resistance was measured by the normal resistance of the grinding wheel, which was measured using a cutting dynamometer.

[0035] As shown in Figure 3, the grinding resistance is highest when there are no bubbles (0%), and decreases as the number of bubbles increases. Even with a fine bubble number density of 100,000 / mL, the grinding resistance was less than half that of machining with coolant that did not generate fine bubbles. Furthermore, no grinding burn or workpiece warping occurred up to 100,000 / mL, demonstrating a certain effect on machining resistance.

[0036] Therefore, the threshold airflow rate should be set to an airflow rate at which the number density of fine bubbles is 100,000 bubbles / mL or higher. Also, as shown in Figure 3, the grinding resistance tends to decrease as the number density of fan bubbles increases. If the number density of fine bubbles is 300,000 bubbles / mL or higher, the grinding resistance will decrease even further, and even better, if it is 500,000 bubbles / mL or higher, the grinding resistance will decrease even more, so it is even better to adjust the flow rate to be above this level.

[0037] During machining, ensure that the airflow rate is above a predetermined threshold before proceeding with the process.

[0038] By installing an air flow meter in the air introduction path to the fine bubble generator and displaying the air flow rate, the number density of fine bubbles being generated can be identified and monitored in real time based on the air flow rate without stopping the operation during processing.

[0039] Furthermore, the lifespan of the fine bubble generator can be predicted by tracking changes in airflow during processing. If the airflow meter reading falls below the threshold during processing, the coolant for the processing machine can be kept in good condition by performing maintenance on the fine bubble generator. Maintenance may include cleaning or replacing porous bodies as needed. [Examples]

[0040] Fine bubbles were generated in the coolant using a fine bubble generator (FB-ASSIST P series MGL-073 manufactured by Nippon Tungsten) installed in the coolant piping for surface grinding. A water-soluble coolant was used.

[0041] A flow meter PF2M705-C6-EW (SMC two-color display digital flow switch) was installed in the air intake path of the fine bubble generator, and the number density of fine bubbles was measured using a Shimadzu Particle Insight at air flow rates of 0.01 L / min and every 0.01 L / min.

[0042] Figure 2 shows the number density of fine bubbles in relation to the airflow rate. The flow rate at which the number density of fine bubbles in the coolant exceeded 100,000 bubbles / mL was 0.05 L / min.

[0043] Initially, the airflow rate was set to 0.5 L / min, and SUS304 sheet metal was processed. During processing, it was possible to confirm that sufficient number density of fine bubbles were being generated simply by checking the airflow rate, without stopping the process. Furthermore, processing could be performed successfully under the same conditions until the airflow rate decreased. As the airflow rate decreased with use, the number density of fine bubbles also decreased. When the airflow rate was approximately 0.3 L / min, the number density of fine bubbles was measured and found to have decreased to 60% of the initial level, but no grinding burn or workpiece warping occurred.

[0044] When the airflow rate fell below 0.05 L / min, we determined that the porous material had reached the end of its lifespan and replaced it. This allowed us to restore the number density of fine bubbles to over 100,000 bubbles / mL without causing grinding burns or warping of the workpiece. [Examples]

[0045] In an automotive parts production line, a fine bubble generator (FB-ASSIST P series MGL-073, manufactured by Nippon Tungsten) installed in the coolant piping was used to generate fine bubbles in the coolant. A water-soluble coolant was used.

[0046] A flow meter PF2M705-C6-EW (SMC two-color display digital flow switch) was installed in the air intake path of the fine bubble generator, and the number density of fine bubbles was measured using a Shimadzu Particle Insight. When the number density of fine bubbles was plotted against the air flow rate, the flow rate at which the number density of fine bubbles in the coolant exceeded 100,000 bubbles / mL was 0.05 L / min (Figure 2).

[0047] The processing was carried out with the airflow rate set to 0.5 L / min. By continuing the processing under the same conditions and replacing the porous material when the airflow rate began to decrease, we were able to perform maintenance in a planned manner.

[0048] Prior to applying the present invention, determining the number density of fine bubbles required stopping the production line, ceasing the supply of coolant, and drying the porous material for 30 minutes while supplying air before making the determination. Even in the shortest case, the production line was stopped for more than 15 minutes, resulting in nearly 20 minutes of non-operational and non-productive time.

[0049] With the present invention, it is no longer necessary to stop the coolant, thus eliminating this non-operating and non-productive time.

[0050] Measurement data of the number density of fine bubbles in relation to the airflow rate confirmed that sufficient number density of fine bubbles could be generated with airflow alone. During normal processing, the coolant supply system could be managed without stopping the process or reducing the efficiency of the production process.

Claims

1. A fine bubble generator attached to the coolant piping route for the machining equipment, The fine bubble generator has an air flow meter installed in the air introduction path, By generating air in the coolant via the fine bubble generator, A coolant containing fine bubbles is supplied to the machining point. In the management method of the coolant supply system, In advance, the flow rate of air flowing to the fine bubble generator is determined as follows: The procedure for measuring and plotting the number density of fine bubbles generated in the coolant, Based on the plotted data, a threshold is set for the airflow rate at which the number density of fine bubbles in the coolant is 100,000 bubbles / mL or more. A process of setting the airflow rate to above the aforementioned threshold and performing processing, During processing, the value of the air flow meter falls below the set air flow rate at the start of processing. Or, if it falls below the threshold, This includes performing maintenance on the fine bubble generator. A method for managing a coolant supply system for a machining center.

2. The method for managing a coolant supply system for a processing machine according to claim 1, characterized in that the fine bubble generator is of the micropore type.

3. The method for managing a coolant supply system for a processing machine according to claim 1 or 2, characterized in that the air flow meter is of the thermal type.

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