JP5477739B2 - Abrasive mixed fluid polishing apparatus and polishing method - Google Patents

Description

  The present invention relates to a polishing apparatus and a polishing method effective for polishing a metal interior, for example, a flow path formed for the purpose of cooling or temperature control of a mold or the like.

  A method is known in which a slurry-like mixed fluid obtained by mixing abrasives such as free abrasive grains in a fluid such as water is flowed at high speed into a through-hole formed in a metal part or ceramic part, and the inner surface thereof is polished. (Patent Document 1).

  However, conventional products subject to high-speed fluidized polishing are intended for polishing inner surfaces of relatively straight holes such as stainless steel capillaries and ceramic ferrule capillaries. It was not effective for polishing the inner surface of the three-dimensional channel.

JP 2003-300148 A

  The present invention provides an inexpensive and mixed abrasive polishing apparatus and polishing method using the same that is effective for polishing an inner surface of a hollow portion formed in communication with a metal member such as a mold. With the goal.

  An abrasive mixed fluid polishing apparatus according to the present invention is an inner surface polishing apparatus for a hollow portion formed in communication with a metal member, and is connected to one opening and the other opening of the communicating hollow portion, respectively. A pair of storage tanks for the abrasive mixed fluid and a pressure increasing means for alternately increasing the internal pressure of the pair of storage tanks, and the abrasive mixed fluid reciprocally flows into and out of the hollow portion The inner surface of the part is polished.

By using the abrasive mixed fluid polishing apparatus, the abrasive mixed fluid is forced to flow into the hollow portion formed in communication with the inside of the sintered metal member manufactured by laser beam modeling, and the inner surface of the hollow portion is Can be polished.
Here, the present invention is suitable for a metal stereolithography mold in which metal powder is laminated in a thin film shape while being sintered with laser light and is three-dimensionally sintered.

  The present invention is effective for polishing the inner surface of a three-dimensional hollow portion, and particularly for polishing the inner surface of a three-dimensional hollow portion formed inside a metal member such as an optical molding sintered mold using laser light. The surface finish can be easily done by forcibly flowing the mixed fluid.

An example of composition of a polisher concerning the present invention is typically shown. The principle diagram of grinding and polishing with loose abrasive grains is shown. The structure of the mold used for the polishing test and evaluation is shown. An example of change in surface roughness of the inner surface of the flow path depending on the polishing time is shown. The graph which measured the change of surface roughness Ra [micrometer] by polishing time is shown. The observation result of the flow-path surface accompanying progress of grinding | polishing time is shown. The size and concentration of loose abrasive grains and the change in flow path surface roughness are shown. (A) shows the relationship between the size of free abrasive grains and surface roughness, and (b) shows the relationship between the concentration of free abrasive grains and surface roughness.

The structural example of the grinding | polishing apparatus using the abrasives mixed fluid based on this invention is shown.
A pair of storage tanks 11 are connected to one opening of a hollow portion such as a flow path provided in communication with a workpiece W made of a metal member such as a mold and the other opening via a connector 11a such as a piping member. Connect each one.
In the storage tank 11, free abrasive grains 20 as an abrasive are mixed with a fluid 21 such as water or oil.
The storage tank 11 is connected to the pressure increasing means so that the mixed fluid of the loose abrasive grains 20 and the fluid 21 can be forced into a flow path formed inside the workpiece W.
Here, the structure of the pressure increasing means is not particularly limited as long as the abrasive mixed fluid can be forced to flow into the communication channel of the workpiece W at a high speed. In this example, the piston 13a disposed in the portion 12 is connected to a cylinder 13 that is reciprocated by hydraulic pressure, air pressure, electric drive, or the like.
The cylinder 13 is not limited in its means and structure as long as the pressure increase portions 12 on the left and right sides can be alternately increased in FIG.
For example, the hydraulic pump 14 can be used for the hydraulic cylinder, the air pump 14 can be used for the air pressure cylinder, and an electric cylinder can also be used.
In the present embodiment, the storage tank 11 and the pressure increasing portion 12 are provided separately, but the pressure increasing portion may be formed integrally with the storage tank.

  In FIG. 1, one of the storage tanks 11 connected to the left and right of the work W is increased in pressure, and the abrasive mixed fluid is forced to flow into the flow path formed in the work W and returns to the other storage tank 11. The abrasive mixed fluid reciprocates in and out of the flow path by alternately increasing the pressure of the pair of storage tanks 11.

FIG. 2 shows a principle diagram that can be ground and polished with loose abrasive grains.
Free abrasive grains are those in which individual abrasive particles are in a free state. When mixed with a fluid such as water or oil, it becomes a slurry, and when a forced flow is generated in the mixed fluid, the abrasive grains Comes into contact with the surface of the workpiece (work), and this surface is ground and polished.
There is no restriction | limiting in particular in an abrasive grain material, An alumina type abrasive grain, a silicon carbide type abrasive grain, a zirconia alumina type abrasive grain is mentioned as an example, and an alumina abrasive grain is good at the point which is easy to obtain cheaply.

FIG. 3 shows an example of the structure of a mold used for examining the polishing conditions with the abrasive mixed fluid.
A mold or the like actually required for polishing is a three-dimensional flow path such as a flow path for flowing a cooling or temperature control medium provided inside.
In recent years, it has been studied to form a three-dimensional flow path in order to increase the cooling efficiency and temperature control efficiency of a mold.
As a means for forming such a flow path, a metal powder that can be sintered, such as iron powder, is laminated in a thin film shape, and a laser beam such as a YAG laser or a CO ₂ laser is focused on the basis of programming. A method of dimensionally forming a sintered body has been studied.
In such a metal stereolithography method, since the surface roughness is rough because it is due to sintering, the cavity surface is finished by cutting or the like, but the medium flow path for cooling, temperature control, etc. is a tool The conventional cutting process cannot be performed.
Therefore, a test evaluation was performed using the separated molds of molds A and B shown in FIG.

  The molds A and B are stereolithography molds by laser light sintering using metal powder, respectively. As shown in FIG. 3B, the semicircular grooves with R = 2.5 mm and L = 80 mm are molded. A pseudo flow path was formed by forming on the facing surfaces of A and B and sealing with a packing material.

Using such a test mold, polishing was performed under the conditions of abrasive alumina, particle size # 150 (average particle size 97.5 μm), abrasive concentration 2.0 vol%, flow rate 20 m / sec, polishing distance 40 m per reciprocation. The results are shown in the graph of FIG.
As a result, as shown in FIG. 4A, the as-sintered surface roughness as-sintered was arithmetic average roughness Ra = 24 μm and maximum height Ry = 115 μm, but after 500 sec Ra = 10 μm After Ry = 41 μm and 9000 sec, Ra = 3.2 μm and Ry = 14 μm.
The time course of the surface roughness Ra at this time is shown in the graph of FIG. 5, and the surface photograph is shown in FIG.

Next, among the alumina abrasive grains, three types of particle sizes # 60 (average particle size 302.5 μm), # 150 (average particle size 97.5 μm), and # 320 (average particle size 72.5 μm) were used, The result of investigating the polishing time and the surface roughness change with the volume concentration of the abrasive grains is shown in the graph of FIG.
As a result, it was assumed that the abrasive grains having a larger average particle diameter can be polished faster, but it was surprisingly found that even if the average grain diameter of the abrasive grains is large, the surface roughness is small.

Therefore, FIG. 8 shows the results of investigating the influence of the particle size and concentration on the surface roughness at the same polishing time.
As a result, in order to finish the surface roughness small, it was found that the relatively coarse particle size # 60 is the best, and the influence of the abrasive concentration is relatively small.
Therefore, it has been clarified that the average particle diameter of the abrasive grains is preferably in the range of 90 to 350 μm when the abrasive grain material is alumina in the sintered mold obtained by laser beam shaping of the metal powder.
Further, the influence of the abrasive grain concentration was at least in the range of 2 to 16 vol%.

  Next, a three-dimensional channel or a branched channel under the conditions of the abrasive grain average particle size of 90 to 350 μm, the concentration range of 2 to 16 vol%, and the flow rate of 10 to 30 m / sec shown above. As a result of polishing the sintered mold formed, a sufficiently practical surface was obtained.

11 Storage tank 12 Pressure increasing part 13 Cylinder 14 Pump 21 Fluid W Workpiece

Claims (1)

A hollow surface inner surface polishing apparatus formed in communication with the inside of a metal member,
A pair of storage tanks of the abrasive mixed fluid respectively connected to one opening and the other opening of the communicating hollow portion, and a pressure increasing means for alternately increasing the internal pressure of the pair of storage tanks, Using an abrasive mixed fluid polishing apparatus in which the inner surface of the hollow part is polished by flowing out and flowing in and out of the hollow part, the abrasive mixed fluid ,
The abrasive mixed fluid is forcibly flowed into the hollow part of the three-dimensional shape formed in communication with the inside of the sintered optical shaping mold produced by laser stereolithography, and the hollow part inner surface is polished .
The abrasive mixed in the abrasive mixed fluid is alumina, the average particle diameter is 90 to 350 μm, and the abrasive concentration is in the range of 2 to 16 vol%. Polishing method with mixed fluid.