JP7803739B2 - Filter material, and filter for electric discharge machine using same, filter for wire-cut machine, electric discharge machining system, and method for manufacturing filter material - Google Patents

Description

This disclosure relates to filter media, filters for electric discharge machines, filters for wire-cut machines, electric discharge machining systems, and methods for manufacturing filter media.

Filter media are used to efficiently remove and purify solid particles contained in liquids and other media. For example, in electrical discharge machines such as wire-cut electrical discharge machines, filtration filters are used in which a folded filter medium made of synthetic fiber, cellulose, or the like is packed into a cylindrical metal or resin container to remove fine metal chips (also known as sludge or dust) from the workpiece (workpiece) that are generated during machining and mixed into the machining fluid. Due to the increasingly fine machining chips produced by these electrical discharge machines, there is a demand for liquid filtration filters with high efficiency (initial efficiency) for capturing small initial dust particles. To address this, liquid filtration filters have been proposed that have a two-layer structure consisting of a filtration layer and a support layer, with the upstream filtration layer containing fibrillated lyocell fibers (Patent Documents 1 to 6).

For example, Patent Document 2 claims that by including fibrillated lyocell fibers in the filtration layer and quasi-filtration layer (support layer), high filtration performance (the filtration time until the resulting filtrate becomes clear) can be achieved through internal filtration by the fibrillated lyocell fibers contained in the filtration layer and quasi-filtration layer until a certain amount of particles captured on the surface accumulates.

However, according to this patent document, the filtration layer contains 40 to 90% by weight of fibrillated lyocell fibers in order to improve the initial performance of internal filtration, which causes the differential pressure to rise rapidly and shortens the lifespan of the filter material.

On the other hand, Patent Document 3 discloses a structure in which the filtration layer contains fibrillated lyocell fibers and a support layer that does not contain fibrillated lyocell fibers is provided downstream. In this case, there is a problem in that the filtration function cannot be fully exerted until a certain amount of particles are captured on the surface and accumulated.

In response to this, it has been thought that increasing the amount of fibrillated lyocell fiber in the filtration layer could improve the initial performance of internal filtration. However, this would lead to increased clogging of the filtration layer, resulting in a shorter filter lifespan. In this way, improving initial performance by increasing the amount of fibrillated lyocell fiber and extending the filter lifespan are contradictory properties, and it has been difficult to achieve both.

Patent No. 5727562 Patent No. 4120737 Patent No. 4086729 Patent No. 5599071 Patent No. 5599072 Patent No. 5759435

One of the purposes of this disclosure is to provide a filter medium that has high initial efficiency while suppressing a decrease in lifespan, as well as a filter for an electric discharge machine, a filter for a wire-cutting machine, an electric discharge machining system, and a method for manufacturing the filter medium that use the same.

Means for solving the problem and effects of the invention

A filter medium according to a first aspect of the present invention comprises a support layer and a filtration layer laminated to the support layer so that one surface is fixed thereto and the other surface serves as a filtration surface on which material to be filtered accumulates. The filtration layer has a finer mesh than the support layer, and contains synthetic resin fibers. The support layer contains synthetic resin fibers and fibrillated lyocell fibers, with the lyocell fibers blended in an amount of 10 to 30% by weight. With this configuration, initial characteristics can be improved by filtering dust with the fibrillated lyocell fibers in the support layer until dust accumulates in the filtration layer and sufficient filtration performance is achieved.

Furthermore, according to the filter medium of the second aspect of the present invention, in the above aspect, the blending amount of the lyocell fiber is 18 to 30% by weight.

Furthermore, according to the third aspect of the present invention, in the filter medium of any of the above aspects, the blending amount of the lyocell fiber is 10 to 20% by weight.

Furthermore, according to the fourth aspect of the present invention, in the filter medium of any of the above aspects, the blending amount of the lyocell fiber is 18 to 20% by weight.

Furthermore, according to a fifth aspect of the present invention, there is provided a filter medium comprising a support layer and a filtration layer laminated to the support layer so that one surface thereof is fixed thereto and the other surface thereof serves as a filtration surface on which material to be filtered accumulates, the filtration layer having a finer mesh than the support layer, the filtration layer containing synthetic resin fibers, and the support layer containing synthetic resin fibers and fibrillated lyocell fibers, the filter medium having a maximum pore size of 40 to 49 μm and a mean flow pore size of 25 to 35 μm.

Furthermore, according to the filter medium of the sixth aspect of the present invention, in any of the above aspects, the filtration layer does not contain fibrillated lyocell fibers.

Furthermore, according to the seventh aspect of the present invention, in the filter medium of any of the above aspects, the filtration layer further contains a pulp-like synthetic polymer.

Furthermore, according to the filter medium of the eighth aspect of the present invention, in any of the above aspects, the initial efficiency is 85% or more at a particle size of 5 μm.

Furthermore, according to the ninth aspect of the present invention, the filter medium has a bending resistance of 700 mgf or more in any of the above aspects.

Furthermore, according to the tenth aspect of the present invention, a filter for an electric discharge machine can use the filter material according to any of the above aspects.

Furthermore, according to the eleventh aspect of the present invention, a filter for a wire cutting machine can use the filter material according to any of the above aspects.

Furthermore, an electric discharge machining system according to a twelfth aspect of the present invention includes a filter device including a filter material using the filter material according to any of the above aspects and a filter cartridge into which the filter material is inserted; a machining tank for storing machining fluid; an electric discharge machining unit that performs electric discharge machining in the machining fluid stored in the machining tank; a control unit that controls the machining operation of the electric discharge machining unit; and a circulation path that connects the machining tank and the filter device so that the machining fluid circulates, and is configured so that the machining fluid discharged from the machining tank is filtered by the filter device and returned to the machining tank.

Furthermore, according to a thirteenth aspect of the present invention, there is provided a method for manufacturing a filter medium comprising a support layer and a filter layer laminated so as to be fixed to the support layer on one side and having the other side serving as a filtering surface on which material to be filtered accumulates, the method comprising the steps of: beating organic synthetic resin fibers and mixing them with synthetic resin fibers to form a filter layer; mixing the synthetic resin fibers with 10 to 30% by weight of fibrillated lyocell fibers to form the support layer; and attaching the support layer to one side of the filter layer to form an integral layer.

FIG. 2 is an enlarged cross-sectional view showing a filter medium according to an embodiment of the present invention. 1 is a graph showing the relationship between the blending amount of Lyocell fiber and the initial efficiency and life of the filter media according to Examples 1 and 2 and Comparative Example 1. 1 is a graph showing the relationship between the maximum pore size and the initial efficiency and life of the filter media according to Examples 1 and 2 and Comparative Example 1. 1 is a graph showing the relationship between the mean flow pore size and the initial efficiency and life of the filter media according to Examples 1 and 2 and Comparative Example 1. 1 is a graph showing the relationship between the amount of Lyocell fiber blended in the filter media according to Examples 3 to 7 and Comparative Example 3 and the initial efficiency. FIG. 1 is a schematic diagram showing an electric discharge machining system. FIG. 1 is a perspective view showing an example of a filter device. FIG. 10 is a perspective view showing another example of a filter device.

Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below are merely examples for embodying the technical concept of the present invention, and the present invention is not limited to these. Furthermore, this specification in no way specifies the components set forth in the claims as components of the embodiments. Unless otherwise specified, the dimensions, materials, shapes, and relative locations of the components described in the embodiments are not intended to limit the scope of the present invention, and are merely illustrative examples. Note that the size and relative positions of components shown in the drawings may be exaggerated for clarity. Furthermore, in the following description, the same names and symbols indicate components that are identical or of similar quality, and detailed description will be omitted as appropriate. Furthermore, the elements constituting the present invention may be configured with the same components, with one component serving multiple functions, or conversely, the function of one component may be shared by multiple components.

The filter media according to an embodiment of the present invention is a component for filtering objects. It is generally used as a filter media in a filter device. The object to be filtered varies depending on the application of the filter media, and is called dust, sludge, etc. Filter media can be used, for example, in filter devices that filter wastewater in machine tools such as processing machines, oil filters for engines, or septic tanks.

The filter is preferably used as a filter for machinery and equipment that are shut down for a certain period of time, such as processing machines. For such equipment that is shut down for a certain period of time, the filter material that adheres to the filter material can be allowed to fall under its own weight while the equipment is not in use, such as overnight, thereby preventing a decline in filtering performance. That is, according to this embodiment, filtering performance can be restored during the shutdown period when the equipment, such as a processing machine, is not in use. This allows filtering performance to be restored during periods when the processing machine is not in use, without the need to set aside a special maintenance period. The process for recovering filtering performance is therefore performed autonomously, without the user having to be particularly aware of the operation or time required for restoring filtering performance. In this way, the filter's own characteristics allow dust to fall under its own weight, thereby preventing a decrease in pressure loss, extending the filter's lifespan, extending the time until replacement, and achieving the excellent effect of reducing maintenance effort and costs. Thus, according to this embodiment, the dust particles that have accumulated on the filter material surface can be released, restoring filtering performance, thereby preventing a decline in filtering performance due to long-term use.

The filter medium according to this embodiment can be suitably used as a filter for an electric discharge machine, and in particular, as a filter for a wire-cut machine.
[Embodiment 1]

A filter medium 10 according to an embodiment of the present invention is shown in the schematic cross-sectional view of Figure 1. The filter medium 10 shown in this figure includes a support layer 1 and a filtration layer 2. The support layer 1 supports the filtration layer 2. The filtration layer 2 is laminated so that one surface thereof is fixed to the support layer 1. The other surface of the filtration layer 2 serves as a filtration surface on which the material to be filtered accumulates.
(Support layer)

The support layer contains synthetic resin fibers and fibrillated lyocell fibers. The amount of lyocell fibers is 10 to 30% by weight.

With this configuration, the initial characteristics can be improved by incorporating fibrillated lyocell fibers into the support layer to capture dust through internal filtration until sufficient filtration performance is achieved due to dust accumulation on the filtering surface. Furthermore, by keeping the amount of lyocell fibers in the support layer below the upper limit of the above range, the mesh size does not become excessively fine, preventing the filter's lifespan from being shortened.

Specific examples of synthetic resin fibers referred to in this specification include polyester-based resins, polyolefin-based resins, polyamide-based resins, acrylic-based resins, polyvinyl acetate-based resins, polyvinyl alcohol-based resins, polyphenylene sulfide-based resins, and modified resins and mixtures thereof, with polyester-based resins being particularly preferred.

Synthetic resin fibers may be fibers made from a single resin, or fibers made from two or more types of resin (composite fibers). Furthermore, a single type of fiber may be used, or multiple types of fibers may be combined.

Synthetic resin fibers may also be used that function as heat-sealing binders. Specific examples include unstretched fibers, and composite fibers such as core-sheath, sea-island, and side-by-side fibers made from multiple resins with different melting points.

The average width of the synthetic resin fibers is preferably 1.0 μm or more and 50 μm or less, more preferably 2.0 μm or more and 40 μm or less, and even more preferably 3.0 μm or more and 30 μm or less. The average fiber width can be determined, for example, by observing with a scanning electron microscope and finding the arithmetic mean value of the widths of 100 fibers randomly selected.

The blending amount of lyocell fiber is preferably 18 to 30% by weight. By blending an amount equal to or greater than the lower limit of this range, the initial efficiency of filtering finer particles can be improved.

Alternatively, the blending amount of lyocell fiber may be 10 to 20% by weight. By keeping the blending amount below the upper limit of the above range, the rigidity of the filter medium can be maintained high, and deformation and breakage during high-pressure filtration operation can be suppressed.

Alternatively, the amount of lyocell fiber may be 18 to 20% by weight.

The fiber length of the fibrillated lyocell fiber in the support layer is preferably about 4 mm. In this specification, the fiber length is a value measured at the contour (the path length of the center line of the fiber) before beating. A measuring instrument such as Kajaani FS300 (Metso) can be used.
(filtration layer)

The filtration layer has a finer mesh than the support layer. The filtration layer also contains synthetic resin fibers and pulp-like synthetic polymers.

The content of synthetic resin fibers in the filtration layer 2 is not particularly limited, but is preferably 40% by mass to 90% by mass, more preferably 45% by mass to 80% by mass, and even more preferably 50% by mass to 70% by mass. This allows the filtration layer 2 to achieve both good filtering performance and strength.

The length of the synthetic resin fibers is not particularly limited, but is preferably 1.5 mm or more and 20 mm or less, more preferably 2.0 mm or more and 18 mm or less, and even more preferably 3.0 mm or more and 18 mm or less.

The filtration layer preferably further contains a pulp-like synthetic polymer. Specific examples of pulp-like synthetic polymers include polyamide, polyimide, polyamideimide, polyacrylonitrile, polyester, polyolefin, polycarbonate, polyacetal, polybutylene terephthalate, ultra-high molecular weight polyethylene, polysulfone, polyethersulfone, polyphenylene sulfide, polyarylate, polyetherimide, polyetheretherketone, aromatic polyamide, aromatic polyimide, liquid crystal polymer, modified resins thereof, and mixtures thereof. The content is preferably 10 to 50%, more preferably 15 to 45%, and even more preferably 20 to 40%. This facilitates the removal of dust accumulated on the filtration surface.

The initial efficiency of filter material 10 is preferably 85% or more at particle size of 5 μm.Here, initial efficiency can be measured by the method specified in ISO19438:2003.That is, using the multi-pass filter tester that conforms to the above-mentioned standard, test oil and contaminant particles are passed through filter material, and the contaminant particles of any particle size are counted at the upstream and downstream of filter material, and the filtration efficiency is calculated by the following formula, and is the average value after 4 minutes, 5 minutes and 6 minutes from the start of test.
(Formula 1)
(Filtration efficiency) = (upstream count number - downstream count number) / (upstream count number) x 100 (%)

This allows clear filtrate to be obtained in a short time, even when filtering liquids containing fine dust.

The bending resistance of the filter medium 10 is preferably 700 mgf or more, and more preferably 850 mgf or more.
(Other ingredients)

The filter medium 10 may contain components other than those described above. Examples of such other components include binders, flocculants, plasticizers, colorants, antioxidants, UV absorbers, light stabilizers, softeners, modifiers, rust inhibitors, fillers, surface lubricants, corrosion inhibitors, heat stabilizers, lubricants, primers, antistatic agents, polymerization inhibitors, crosslinking agents, catalysts, leveling agents, thickeners, dispersants, antioxidants, flame retardants, hydrolysis inhibitors, corrosion inhibitors, carbon fibers, carbon nanotubes, carbon nanofibers, fullerenes, metal fibers, and metal particles.

The thickness of the filter medium 10 is not particularly limited, but is preferably between 50 μm and 400 μm, more preferably between 55 μm and 370 μm, and even more preferably between 60 μm and 350 μm.

The volume ratio of the support layer to the entire filter medium 10 is preferably 30% by volume or more and 90% by volume or less, more preferably 40% by volume or more and 85% by volume or less, and even more preferably 50% by volume or more and 82% by volume or less.

Examples of materials that can be used for the support layer 1 include dry nonwoven fabrics such as meltblown, spunlace, and needle punch, wet nonwoven fabrics, and woven fabrics. Among these, wet nonwoven fabrics are preferred in terms of adhesion to the filtration layer.
(Method for manufacturing filter medium 10)

Here, we will explain a method for manufacturing such a filter medium 10. However, the content of the present invention is not limited to the following examples.

The wet papermaking method is a suitable method for manufacturing the filter layer. First, a pulp-like synthetic polymer and synthetic resin fibers are dispersed in water to form a papermaking slurry. Next, the water is filtered through the wire mesh of a papermaking machine and dried using a cylinder dryer or similar to obtain the filter layer. The papermaking machine that can be used here includes a fourdrinier, cylinder, inclined short-wire, twin-wire, etc.

Next, 10 to 30% by weight of fibrillated lyocell fibers are blended with the synthetic resin fibers to form a support layer. The blending method may involve impregnating or coating a base fabric made of synthetic resin fibers with a lyocell fiber dispersion, or it may be made into a paper similar to the filtration layer. The support layer is then attached to one side of the filtration layer to form an integrated laminate. The attachment method may involve blending a heat-sealable binder fiber into both or one of the support layer and filtration layer, and then heating and pressurizing the laminate using a cylinder dryer or the like, or by laminating a heat-sealable mesh or the like between them. This results in a filter medium 10, as shown in Figure 1, in which a filtration layer 2 is laminated on a support layer 1.
[Examples 1 and 2, Comparative Examples 1 and 2]

Next, filter media according to Examples 1 and 2 and filter media according to Comparative Examples 1 and 2 were each prepared, and their properties were compared. The preparation method for each sample was as follows. First, the filter layer material was prepared by dispersing core-sheath polyester fiber (2.2 dtex, 5 mm), stretched polyester fiber (0.3 dtex, 5 mm), and acrylic pulp in water at the blending ratios shown in Table 1 to form a papermaking slurry, which was then made into paper on a cylinder paper machine. Meanwhile, the support layer material was prepared by dispersing core-sheath polyester fiber (2.2 dtex, 5 mm), stretched polyester fiber (0.3 dtex, 5 mm), and beaten lyocell fiber in water at the blending ratios shown in Table 1 to form a papermaking slurry, which was then made into paper on a Fourdrinier paper machine. The filter layer and support layer were layered in the wet paper state and dried using a Yankee dryer to obtain the filter media according to Examples 1 and 2 and Comparative Example 1.

Furthermore, for Comparative Example 2, the filter layer was made of sheath-core polyester fiber (2.2 dtex, 5 mm), stretched polyester fiber (0.3 dtex, 5 mm), and beaten lyocell fiber in the blending ratios shown in Table 1. The support layer was made of sheath-core polyester fiber (2.2 dtex, 5 mm) and stretched polyester fiber (0.3 dtex, 5 mm) in the blending ratios shown in Table 1. The support layer was made on an inclined short-wire papermaking machine. The filter medium for Comparative Example 2 was obtained in the same manner as in Example 1. For each sample obtained, the basis weight, paper thickness, density, air permeability, maximum and median pore size (P.S.), flexibility, initial efficiency, and life were measured.

The basis weight of each sample was measured in accordance with JIS P 8124:2011.

The paper thickness of each sample was measured in accordance with JIS P 8118:2014.

The maximum pore size and mean flow pore size of each sample were measured using the bubble point method (ASTM F316-86, JIS K 3832) with 2-propanol as the test liquid. The mean flow pore size is the value of d (μm) expressed by the formula d = cγ/P, where P (Pa) is the differential pressure at the intersection of the curve obtained by dividing the dry curve by half the flow rate and the wet curve, and P (Pa) is the pressure at which air bubbles first begin to emerge from a liquid-wet sample (the bubble point value). The maximum pore size is the value of d (μm) expressed by the formula above, where P (Pa) is the pressure at which air bubbles first begin to emerge from a liquid-wet sample (the bubble point value).

The bending resistance of each sample was measured using a Gurley tester in accordance with JIS L 1096:2010, with three stacked 88.9 x 25.4 mm samples. The measured value (mN) was converted to the bending resistance (mgf).

The initial efficiency and life of each sample were measured using a multi-pass filter testing device conforming to ISO 19438: 2003, with a filtration area of 98.5 ^cm , an oil volume of 6 L, a test flow rate of 0.7 L/min, and a concentration of 42.9 mg/L. Here, life is defined as the test time (minutes) from the start of the test until the filter pressure loss increases by 100 kPa.

The composition and physical properties of each sample are shown in Table 1. Figure 2 shows the relationship between the amount of lyocell fiber in each sample and the initial efficiency and lifespan. In the figure, ● indicates initial efficiency, and ▲ indicates lifespan. Figure 3 shows the relationship between pore size (maximum value), initial efficiency, and lifespan, and Figure 4 shows the relationship between mean flow pore size, initial efficiency, and lifespan.

As shown in Table 1, in Examples 1 and 2, the initial efficiency was higher than that of Comparative Examples 1 and 2 as the amount of lyocell fiber in the support layer increased for all sizes of 4 μm or more, 5 μm or more, and 6 μm or more. Furthermore, the life decreased slightly as the amount of lyocell fiber increased, but remained at a higher level than Comparative Example 2. This is presumably because the surface of the upstream filtration layer traps dust particles to prevent the pores in the filter medium from clogging, while the fibrillated lyocell fibers arranged on the support layer side trap particles, improving the initial properties.
[Examples 3 to 7, Comparative Example 3]

Furthermore, filter media according to Examples 3 to 7 and filter media according to Comparative Example 3 were each produced, and their properties were compared. The production method for each sample was the same as that of Example 1 above, except that the filter layer and support layer were each made using a square sheet machine conforming to JIS P 8222, laminated in a wet paper state, and dried at 120°C using a Kumagai Riki rotary dryer. The basis weight, paper thickness, and initial efficiency of each obtained sample were measured in the same manner as in Example 1. The composition and physical properties of each sample are shown in Table 2. The relationship between the amount of lyocell fiber blended and initial efficiency is also shown in the graph in Figure 5.

As shown in these tables and graphs, in Examples 3 to 7, a high correlation was observed between the amount of lyocell fiber in the support layer and initial efficiency.

The filter material of the present embodiment can be preferably used as the filter material for electric discharge machine, more preferably as the filter material for the filter device of wire-cutting machine.In particular, it can be preferably used as the filter material for the filter device of the electric discharge machine such as wire-cutting electric discharge machine, which removes the fine metal chips of the workpiece that are discharged during machining and exist in the machining fluid.In this case, the object to be filtered is the fine metal chips.
(Electrical discharge machining system 1000)

Figure 6 shows an electric discharge machining system 1000 in which an electric discharge machine 200 and a filter device 100 are connected. The electric discharge machining system 1000 shown in this figure connects the electric discharge machine 200 and the filter device 100. The electric discharge machine 200 includes a machining tank 210 for storing machining fluid, an electric discharge machining unit 220 that performs electric discharge machining in the machining fluid stored in the machining tank 210, a control unit 230 that controls the machining operation of the electric discharge machining unit 220, and a circulation path 240 that connects the machining tank 210 and the filter device 100 so that the machining fluid circulates. The electric discharge machine 200 is connected so that water is discharged through the filter device 100. The electric discharge machining system 1000 is configured so that machining fluid discharged from the machining tank 210 is filtered by the filter device 100 and returned to the machining tank 210.

The control unit 230 also controls the electric discharge machining unit 220 to stop the machining operation for a certain period of time. With this configuration, when the electric discharge machine 200 is not in use, such as at night, the material to be filtered that has adhered to the filter for the electric discharge machine 200 falls by its own weight, thereby preventing a decrease in filtering performance.
(Filter device 100)

The filter device 100 includes a filter cartridge 120 into which a filter material 110 is inserted. The filter material 110 is held with the filtering surface facing upright. An example of a filter device 100 connected to an electric discharge machine 200 is shown in Figure 7. The filter device 100 shown in this figure has a cylindrical filter cartridge 120 into which a filter material 110 made of filter material 10 is inserted. This filter device 100 is placed vertically and uses an out-in system, in which wastewater is taken in from the circumferential direction, filtered by the filter material 110, and discharged axially, as indicated by the band-shaped arrows. In this filter device 100, wastewater containing dust DT is circulated through a circulation path 240 while the electric discharge machine 200 is operating. The wastewater is then filtered by the filter device 100, purified, and made reusable.

In the filter device 100, dust DT accumulates on the filtering surface of the filter material 110 as wastewater circulates. In a filter device 100 for such a processing machine, dust DT, such as processing debris, adheres to the surface of the filter material 110, forming a cake layer and remaining there, reducing filtering performance. As the processing machine is used, the amount of dust DT that adheres increases, reducing pressure loss and bringing the filter device 100 to an end of its life.

For this reason, in order to extend the life of filter devices, conventional filter devices for processing machines have adopted a structure that uses mechanical action to sift away dust adhering to the surface of the filter material, such as blowing compressed air to cause it to fall downward or vibrating the filter itself. However, adding a compressed air blowing mechanism to a filter device requires the preparation of a compressor, piping, etc., making the configuration more complicated. Furthermore, a configuration that vibrates the filter material also requires the installation of a power mechanism to produce such mechanical action, which is similarly time-consuming. Furthermore, in either case, tasks such as blowing compressed air and vibrating the filter material must be repeated regularly, which creates the problem of additional maintenance work.

In contrast, the filter media of this embodiment does not require such an additional mechanism. Instead, the characteristics of the filter media 110 itself make it easy for the attached dust DT to fall under its own weight. This allows the dust DT to fall and settle to the bottom of the filter cartridge 120 at night or during downtime, without requiring any special operations, thereby restoring the filtering performance of the filter media 110. This method allows existing filter devices to be used as is, eliminating the cost of application. Furthermore, there is no need to perform separate, regular operations to remove dust (such as spraying compressed air or vibrating the filter), making it easy to maintain.

In other words, according to this embodiment, by using a filter material with a smooth surface as the filter, dust DT and other particles adhering to the filter surface fall to the bottom of the filter cartridge 120 under their own weight, which is expected to restore filtration performance. In particular, for processing machines that require operational shutdowns, the dust will continue to fall during the shutdown period, improving the effectiveness of restoring filtration performance. A temporary shutdown of operation is sufficient. In other words, dust is expected to fall over time, even if it is not for a long period such as several days or months. Furthermore, after a certain period, the dust will have almost completely fallen, and the filtration performance restoration effect is likely to saturate. The downtime period varies depending on the processing volume of the processing machine used, the material and size of the workpiece, the type of filtrate, the size of the filter, and other factors. Tests conducted by the inventors have found that a downtime period of approximately five hours is sufficient to restore filtration performance.

The filter replacement time for such processing machines is generally when the filter's pressure loss reaches a specified value (e.g., 200 kPa to 300 kPa). In other words, the filter's lifespan is determined by the time it takes to reach the specified pressure loss.

Furthermore, according to this embodiment, dust particles accumulated on the surface of the filter material fall to the bottom of the filter cartridge 120 during periods when the processing machine is stopped, reducing the resistance to fluid flow through the filter material. This suppresses an increase in pressure loss, lengthens the time until the specified value is reached, and extends the life of the filter. In other words, the filter material according to this embodiment is suitable for use in processing machines that have downtime periods during which operation is stopped for a certain period of time or more. By utilizing the downtime of the processing machine, the amount of dust that falls under its own weight is increased compared to the amount of dust that accumulates, thereby restoring filtration performance. This method allows the filtration performance recovery period to be set while the filter device is operating normally, without any special steps or treatments, and the replacement cycle of the filter device can be extended.
(filtration method)

Here, we will explain a filtration method using a filter device that uses the filter media of this embodiment as the filter material. Machining is performed using an electric discharge machine 200 with an electric discharge machine filter installed, and the material to be filtered contained in the machining water is allowed to adhere to the surface of the electric discharge machine filter. Then, while the machining operation of the electric discharge machine 200 is stopped for a certain period of time or more, the material to be filtered that has adhered to the electric discharge machine filter is allowed to fall under its own weight. In this way, when the electric discharge machine 200 is not in use, such as overnight, the material to be filtered that has adhered to the electric discharge machine filter is allowed to fall under its own weight, preventing a decline in filtering performance.

The shape of the filter device is not limited to the form shown in Figure 7, and any known form can be used as appropriate. For example, the filter device 100' according to embodiment 2 may be configured as multiple flat plates extending radially around the periphery, as shown in Figure 8. The filter device 100' shown in this figure also has a filter material 110' inserted into a filter cartridge 120'.

The filter media of the present invention, as well as the filters for electric discharge machines, filters for wire-cut machines, electric discharge machining systems, and methods for manufacturing the filter media, can be suitably used as filter media for filter devices in wire-cut machines and other processing machines.

1... Support layer 2... Filter layer 10... Filter material 100, 100'... Filter device 110, 110'... Filter material 120, 120'... Filter cartridge 200... Electric discharge machine 210... Machining tank 220... Electric discharge machining unit 230... Control unit 240... Circulation path 1000... Electric discharge machining system DT... Dust

Claims (12)

The supporters and
A filter medium comprising a filter layer having one surface laminated to be fixed to the support layer and the other surface serving as a filtering surface on which a filtering object is accumulated,
The filtration layer has a finer mesh than the support layer,
The filtration layer contains synthetic resin fibers,
The filter medium wherein the support layer contains synthetic resin fibers and fibrillated lyocell fibers, and the blending amount of the lyocell fibers is 10 to 30% by weight. The filter medium according to claim 1,
The filter medium has a blending amount of the lyocell fiber of 18 to 30% by weight. The filter medium according to claim 1,
The filter medium has a blending amount of the lyocell fiber of 10 to 20% by weight. The filter medium according to claim 1,
The filter medium has a blending amount of the lyocell fiber of 18 to 20% by weight. The supporters and
A filter medium comprising a filter layer having one surface laminated to be fixed to the support layer and the other surface serving as a filtering surface on which a filtering object is accumulated,
The filtration layer has a finer mesh than the support layer,
The filtration layer contains synthetic resin fibers,
The support layer includes synthetic resin fibers and fibrillated lyocell fibers,
The filter medium has a maximum pore size of 40 to 49 μm and a mean flow pore size of 25 to 35 μm. The filter medium according to any one of claims 1 to 5,
A filter medium in which the filtration layer does not contain fibrillated lyocell fibers. The filter medium according to any one of claims 1 to 6,
The filter medium, wherein the filtration layer further comprises a pulp-like synthetic polymer. The filter medium according to any one of claims 1 to 7,
A filter medium having an initial efficiency of 85% or more at a particle size of 5 μm. The filter medium according to any one of claims 1 to 8,
A filter medium having a bending resistance of 700 mgf or more. A filter for an electric discharge machine using the filter material described in any one of claims 1 to 9. A filter for a wire cutting machine using the filter material described in any one of claims 1 to 9. A filter material using the filter material according to any one of claims 1 to 9,
a filter device including a filter cartridge into which the filter material is inserted;
a machining tank for storing machining fluid;
an electric discharge machining unit that performs electric discharge machining in the machining fluid stored in the machining tank;
a control unit that controls the machining operation of the electric discharge machining unit;
a circulation path that connects the machining tank and the filter device so that the machining fluid circulates;
Equipped with
The electric discharge machining system is configured so that the machining fluid discharged from the machining tank is filtered by the filter device and returned to the machining tank.