JPH032640B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an abrasive water jet cutting method.

(Prior Art) A conventional abrasive water jet cutting method will be described with reference to FIG. Conventionally, in cutting using an abrasive water jet, as shown in the figure, ultra-high pressure water 53 is supplied from an ultra-high pressure water pump 51 to a jet nozzle (abrasive nozzle) 52, while ultra-high pressure water 53 is supplied from an abrasive tank 54 to the jet nozzle 52. A dry abrasive 55 is supplied, and the dry abrasive 55 is mixed with the ultra-high pressure water 53 in the mixing chamber 56 in the jet nozzle 52, and the ultra-high pressure water 53 containing the dry abrasive is applied to the material to be cut. It was done by spraying. As the dry abrasive material 55, for example, silica sand, cast iron grid, garnet, alumina, etc. with an average particle diameter of about 0.2 to 0.8 mm have been used.

(Problems to be Solved by the Invention) The conventional abrasive water jet cutting method described above has the following drawbacks. First of all, since the dry abrasive material 55 is used, the abrasive nozzle tip 57 wears out prematurely, resulting in a very short service life. Secondly, since the dry abrasive material 55 has a large particle size, the cutting width (kerf width) becomes wider than the abrasive nozzle tip diameter.
The drawback is that burrs are formed on the back surface of the material to be cut, and precise cutting cannot be performed.

This invention was made to solve the above-mentioned conventional problems, and its purpose is to extend the life of the abrasive nozzle tip, and to make the cutting width equal to the diameter of the abrasive nozzle tip. It is an object of the present invention to provide a water jet cutting method that can perform precise cutting by cutting the water jet at a depth of 100 mm or less.

(Means for Solving the Problems) Therefore, in the water jet cutting method of the present invention, a suspension containing fine abrasive particles with an average particle size of 100 μm or less is supplied to an ultra-high pressure water jet for cutting. .

(Function) As mentioned above, when a suspension containing a fine abrasive is supplied to an ultra-high pressure water jet for cutting, the wear of the abrasive nozzle tip is significantly reduced, unlike when a dry abrasive is supplied. , its lifespan will be greatly extended. Furthermore, the cutting width can be made narrower, and the cut surface can be polished at the same time as well as cutting with the abrasive material, making it possible to perform precise cutting without forming burrs on the back surface of the material to be cut. Note that using a fine-grain abrasive with an average particle size of 100 μm or less is because if the particle size is larger than this, the sedimentation rate will be faster.
This is because it is difficult to form a suspension using ordinary stirring means.

(Example) Next, regarding a specific example of the method of this invention,
This will be explained in detail with reference to the drawings.

FIG. 1 shows an outline of the apparatus used in this embodiment. In the figure, 1 is a jet nozzle (abrasive nozzle) for cutting the material 2 to be cut.
A high-pressure water supply hose 3 led from an ultra-high pressure water pump is connected to the base end of this jet nozzle 1, and a suspension supply hose 5 led from a stirring tank 4 is connected to the side. is connected. Reference numeral 6 denotes a cover surrounding the periphery of the cut portion of the workpiece 2, and 7 a catcher for receiving the ultra-high pressure water jet jetted from the jet nozzle 1 toward the workpiece 2. The ultra-high pressure water containing the suspension is passed through a recovery pipe 9 to a concentration control tank 10.
The structure is such that it is circulated and supplied to the A recovery pump 8 is interposed in the recovery pipe 9, and the used abrasive material 11, which is pumped to the concentration control tank 10 by the recovery pump 8, is subjected to concentration control and recycled. Become. The concentration control tank 10 is
It has a supply hopper 22 for the fine abrasive material 11, and is connected to the stirring tank 4 via a connecting pipe 23. Note that the concentration control tank 10 has a structure in which water is drained from the top. The stirring tank 4 is equipped with a stirrer 24, and the base end of the suspension supply hose 5 is connected to the bottom of the stirrer 24. In this case, a filter 25 is attached to the connection part of the suspension supply hose 5. The suspension supply hose 5 is provided with a control valve 26 having a throttle function, so that the amount of suspension supplied can be freely controlled. As described above, in the above device, the abrasive material 11 is recycled by circulating it in a closed circuit, and compared to the conventional method, the abrasive material 11 is recycled.
This makes it possible to reduce the amount of waste.

The detailed structure of the jet nozzle 1 is shown in FIGS. 2 to 4. As is clear from the figure, the jet nozzle 1 includes a mixer outer cylinder 13 having a mixer chamber 12 therein, and a mixer outer cylinder 13 having a mixer chamber 12 therein.
a nozzle tip 15 attached to the distal end side of the mixer via a holder 14; a mixer inner cylinder 16 disposed within the mixer outer cylinder 13 and mixing the suspension into high-pressure water using negative pressure; This mixer inner cylinder 1
It consists of a pure water nozzle (diamond, sapphire, etc.) 17, etc., interposed between the base end of the mixer inner cylinder 16 and the mounting bracket side of the high-pressure water supply hose 3, and the base of the mixer inner cylinder 16 is configured to have a small diameter. The cylindrical mixer chamber 12 is formed on the outer periphery thereof. The mixer outer cylinder 13 is arranged so as to intersect with this cylindrical mixer chamber 12 in a tangential direction.
A suspension introduction path 18 is formed on the side of the suspension. The mixer inner cylinder 16 has a high-pressure water passage 19 at its axial center, and the mixer chamber 12 is located around it.
and the high-pressure water passage 19, and in this case, each suspension passage 20 is formed to intersect with the high-pressure water passage 19 at a predetermined angle. has been done. Note that the mixer inner cylinder 16 may have only one suspension passage 20 and may be configured to intersect with the high-pressure water passage 19 at 90 degrees.

Next, a method of cutting the material to be cut 2 by abrasive water jet using the above-mentioned apparatus will be described. First, the concentration control tank 10 and the stirring tank 4
A fine abrasive material with an average particle size of 100 μm or less (for example, alumina fine powder, silicon carbide fine powder, etc.) is mixed with water and stirred to form a suspension with a concentration of 20 to 70%. The reason why the particle size of the abrasive is set to 100 μm or less is because if the particle size is larger than this, the sedimentation rate is high, making it difficult to create a suspension using normal stirring means.
Also, if the concentration is lower than 20%, a good cutting effect cannot be obtained, and if the concentration is higher than 70%, it becomes close to a solid and it becomes difficult to supply it to the jet nozzle 3 using negative pressure. Next, once the suspension is prepared, ultrahigh pressure water is supplied from an ultrahigh pressure water pump to the jet nozzle 3 via the high pressure water supply hose 5. Then, the ultra-high-pressure water jet passes through the high-pressure water passage 19 in the jet nozzle 3 at high speed, and the resulting negative pressure causes the suspension in the mixer chamber 12 to flow through each suspension passage 2.
0 and is mixed (supplied) into the ultra-high pressure water jet. At this time, since the suspension introduction path 18 crosses the mixer chamber 12 in the tangential direction as described above, the suspension flows into the mixer chamber 12.
2, and is mixed into the ultra-high pressure water jet in a sufficiently agitated state. On the other hand, the supply amount of the suspension is controlled by changing the aperture diameter of the control valve 26. In this case, the concentration of the suspension is, for example, 50% (the abrasive nozzle diameter 2
mm), the total supply amount is controlled to be 5 kg/min or less. If it exceeds 5Kg/min,
This is because the dispersion of the jet nozzle 3 becomes large and the cutting efficiency deteriorates. However, if the diameter of the abrasive nozzle is large, it may be 5 kg/min or more.

FIG. 5 shows the relationship between the injection time of the jet nozzle 3 and the amount of change in the nozzle diameter. As is clear from the figure, in the conventional method using a dry abrasive, the jet nozzle 3 wears out early, whereas in the embodiment method of the present invention, the progress of wear is gradual, and the life of the jet nozzle 3 is reduced. It can be seen that compared to the conventional method, the period is approximately 7 times longer in the normal usage range.

FIGS. 6a and 6b show the state of the cut surfaces of test materials (materials to be cut) cut by the method of the above embodiment and the conventional method. In this case, dry silica sand is used in the conventional method (b), and stainless steel with a thickness of 5.3 mm is used as the test material in both cases. This shows that, compared to the conventional method, the method of this embodiment can cut with a much narrower cutting width (same or smaller than the nozzle diameter) even when jet nozzles of the same diameter are used. In addition, when looking at the cross section with a microscope, burrs are formed on the back side of the sample material at the edges of the cutting grooves in the conventional method.
It was confirmed that no burrs were formed on the edges of the cutting grooves obtained by the method of the above embodiment. From these facts, it is clear that according to the method of this embodiment, precise cutting can be performed.

According to the method of the above example, the abrasive used hardly changes in particle size, shape, etc., so there is no problem with recycling.
This reuse makes it possible to eliminate the need for conventional post-processing. Further, since the suspension can easily adjust and control the supply amount, the abrasive can be stably supplied.

FIG. 7 shows the relationship between the abrasive supply amount and the cutting limit speed in the conventional method and the example method, respectively.
~800 μm), and this example method uses an alumina suspension (particle size 10 to 70 μm, concentration 50%), respectively. As is clear from the figure, it was generally believed that the cutting ability of a waterjet increases as the particle size of the abrasive increases for ductile materials such as metals. As in, the average particle size
It can be seen that even when using a suspension containing fine abrasive particles of 100 μm or less, the cutting ability is as good as or better than that of the conventional method.

By the way, in the past, plastics, fiber reinforced plastics (FRP), sheet molding compounds (SMC), Bakelite, acrylic, rubber,
When cutting soft materials such as leather with a water jet, it is done by spraying pure water, but when water jet cutting is performed using such a pure water method, burrs are formed on the back side of the material to be cut. At the same time, cracks and the like occur on the cut surface, often requiring secondary processing. Therefore, when the method of the above embodiment (suspension method) was applied to waterjet cutting of soft materials and compared with the case using the pure water method, the following good results were obtained. First, when carbon fiber reinforced plastic (CFRP) with a thickness of 10 mm is cut using both methods,
According to the pure water method, burrs were formed on the edges of the cutting grooves on the back side of the sample material, and many cracks were generated on the cut surface, but according to the method of the example, no burrs were formed on the same parts, and There were almost no cracks on the cut surface. This was also the case when glass fiber reinforced plastic (GFFRP) with a thickness of 10 mm was used as the test material. Furthermore, when cutting acrylic with a thickness of 6 mm using both methods, when using the pure water method, many planar peelings were formed around the cutting groove on the back side of the specimen, and many localized defects were also formed on the cut surface. However, according to the method of the example, such peeling did not occur at all. In all of the above examples, at the same pressure (for example, 2000 kg/cm ² ), the method of the example was able to cut at a higher speed than the pure water method. Therefore, according to the method of the above embodiment, precise cutting can be performed not only when the material to be cut is a hard material but also when a soft material is used, and secondary processing is not required. It has become clear that this method has an excellent cutting ability capable of cutting at a higher speed than waterjet cutting.

(Effects of the Invention) In the water jet cutting method of the present invention, a suspension containing fine abrasive particles with an average particle size of 100 μm or less is supplied to the cutting ultra-high pressure water jet, so that the dry abrasive material can be cut. Compared to conventional waterjet cutting methods that supply ultra-high pressure water jets, the abrasive nozzle tip wear is significantly reduced and its lifespan is greatly extended. In addition, since the cutting width can be narrowed and the abrasive material is fine particles, not only cutting with the abrasive material but also polishing of the cut surface is done at the same time, leaving almost no burrs on the back side of the material to be cut. It is possible to make precise cuts that would otherwise be impossible. Furthermore, if the suspension is reused, post-treatment can be made unnecessary.

[Brief explanation of the drawing]

Fig. 1 is a layout diagram of devices used in an embodiment of the water jet cutting method of the present invention, Fig. 2 is a longitudinal sectional side view of the jet nozzle used in the above embodiment, and Fig. 3 is a cross-sectional view taken from Fig. 2. , Fig. 4 is a cross-sectional view of Fig. 2, Fig. 5 is a graph showing the relationship between nozzle injection time and nozzle diameter change, and Fig. 6 a and b show the metallographic structure of the sample material after cutting. 7 is a graph showing the relationship between the abrasive supply amount and the cutting limit speed, and FIG. 8 is an explanatory diagram of the conventional method. 1... Jet nozzle, 2... Material to be cut, 3...
...High pressure water supply hose, 5...Suspension supply hose,
11...Fine abrasive material.

Claims (1)

[Claims] 1. A waterjet cutting method characterized by supplying a suspension containing fine abrasive particles with an average particle diameter of 100 μm or less to an ultra-high pressure water jet for cutting.