METHOD OF MANUFACTURING PLATE WORKPIECE WITH SURFACE MICROSTRUCTURES

A method of manufacturing a plate workpiece with surface microstructures is provided. Before press-molding, a preform is placed between a first mold with a pattern and a second mold, and is disposed on the second mold. Next, the first mold and the second mold are heated to a transition temperature of the preform, and then pressed against the preform to impress the pattern onto the preform to obtain a patterned preform. Finally, the patterned preform is cooled with the second mold and shrunk to obtain the plate workpiece with surface microstructures. Since the patterned preform is uniformly cooled from bottom to top by thermal conduction, the temperature field is isothermal in a horizontal distribution. Therefore, a plate workpiece with high accuracy surface microstructures is obtained, and is useful for carrying multiple optical fibers in optical communication.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, one skilled in the arts can easily realize the advantages and effects of a method of manufacturing a plate workpiece with surface microstructures in accordance with the present invention from the following embodiments. The descriptions proposed herein are just preferable embodiments for the purpose of illustrations only, not intended to limit the scope of the invention. Various modifications and variations could be made in order to practice or apply the present invention without departing from the spirit and scope of the invention.

The method of manufacturing a plate workpiece with surface microstructures was implemented as described in detail incorporating the block diagram as shown inFIG. 1.

As shown inFIG. 2A, a press-molding apparatus1was provided in step (A). The press-molding apparatus comprised a first mold11, a second mold12and two fixing members13.

The first mold had a first surface111and a second surface112opposite to the first surface111. A pattern14was formed on the first surface111of the first mold11. The second mold12was disposed to face the first surface111of the first mold11having the pattern14. Two fixing members13were disposed on the second mold12and respectively disposed at two opposite sides of the first mold11.

A preform21was provided in step (B). The preform21was placed between the first mold11and the second mold12as well as between two fixing members13, and is disposed on the second mold12. The preform21was made of optical glass, which enables the preform21to be press-molded with a pattern corresponding to the pattern14of the first mold11.

In the present embodiment, the first mold11, the second mold12and the preform21were disposed in a closed chamber (not shown in figure). As shown inFIG. 3, step (B′) was performed before the heating, pressing, cooling and parting steps, which were step (C), (D), (E) and (E′) in sequence. The pressure in the closed chamber was reduced to not more than 5×10−3torr in step (B′). Therefore, the thermal transfer by gas in the closed chamber and oxidation of the first mold11and the second mold12was avoided. The stability of the preform cooled only from a single surface was improved.

Subsequently, the first mold11was heated with a heating rate of 5° C./second to about 540° C., and maintained at the temperature for about 100 seconds. Meanwhile, the second mold12was heated with a heating rate of 3.86° C./second to about 540° C., and maintained at the temperature for about 80 seconds. Accordingly, the preform21disposed on the second mold12was heated together to be capable of being press-molded.

In the present embodiment, the first mold11and the second mold12were made of a thermal conductive material, tungsten carbide. The first surface111of the first mold11had centerline average roughness less than 20 nanometers.

Then, a load of 150N was applied for pressing the first mold11down against the heated preform21for about 86.4 micrometers with a pressing rate of 1.5 micrometers/second in step (D). As shown inFIGS. 2A,2B and3, the preform12was pressed against the first mold11and the second mold12, such that the pattern14formed on the first surface111of the first mold11was impressed onto a top surface of the preform21to obtain a patterned preform21A.

The pattern of the patterned preform21A comprised multiple grooves211formed in a top surface of the patterned preform21A. Each groove211had a width about 105.8 micrometers, and every two adjacent grooves had an interval about 128 micrometers inbetween.

In step (D′), the patterned preform21A was continuously pressed and the first mold11was held at the same position for 100 seconds, so as to release the thermal stress of the patterned preform21A produced in the heating and pressing steps.

After that, air was used as a cooling gas to blow the second surface112of the first mold11and the second surface122of the second mold12uniformly in step (E), so as to cool the first mold11only from its second surface112and cool the second mold12only from its second surface122with a cooling rate of 0.5° C./second. In the present embodiment, the first mold11and the second mold12were cooled down to about 460° C.

Accordingly, the patterned preform21A was uniformly cooled from bottom to top and together with the second mold12by thermal conduction after blowing the air to the second surface122of the second mold12. Further, the contact force between the patterned preform21A and the first mold11was reduced to zero after the first mold11was cooled to 490° C. The patterned preform21A was shrunk and had a smaller volume than before shrinkage. Thus, the patterned preform21A was capable of parting from the first surface111of the first mold11and from the fixing members13disposed nearby two sides of the patterned perform21A.

Next, in step (E′), the second mold12was secondary cooled from the second surface122with a cooling rate of 1.5° C./second, the first mold11was also cooled with a cooling rate less than 5° C./second to room temperature. At the same time, the first mold11was elevated to the original position.

After carrying out cooling of the first mold11and the second mold12, the vacuum of the closed chamber was released. Finally, a plate workpiece with surface microstructures4was obtained as shown inFIG. 4. Here, said plate workpiece with surface microstructures4was the patterned preform21A after cooling.

As shown inFIG. 4, the plate workpiece with surface microstructures4had multiple grooves41formed in the top surface of the plate workpiece4. The grooves41extended along a direction D and parallel to each other. In the present embodiment, the grooves41were formed in, but not limited to, a V-shape.

In the present embodiment, the grooves41of the plate workpiece4had a mean width of 105 micrometers and a width tolerance of 0.1 micrometers. The grooves41also had a mean interval of 127 micrometers between every two adjacent grooves41and an interval tolerance less than 0.3 micrometers. It demonstrated that the method succeeded in manufacturing a plate workpiece having surface microstructures with high accuracy and high grooves quantity.

With further reference toFIGS. 2B and 4, the heated preform21was compressed in a vertical direction and expanded in a horizontal direction after being pressed against the first mold11. Two fixing members13were disposed at two opposite sides of the patterned preform21A, and each fixing member13had a long axis parallel to the direction D of the grooves211of the patterned preform21A. Therefore, the two fixing members disposed at these positions achieved the objectives of controlling the overall size of the patterned preform21A and improving the accuracy of the surface microstructures of the plate workpiece4, i.e., reducing the error variance of the widths and interval tolerances to the least.

In the present embodiment, the two fixing members13were made of a thermal insulated material. 100 nanometers-thick platinum-iridium alloy films131were coated on the surface of the fixing members13nearby the patterned preform21A, so as to provide the fixing members with adhesive-free property. No fixing member was disposed at the ends of the grooves211, which ensures that the thermal stress of the plate workpiece can be released through the ends.

As shown inFIG. 5, the temperature field of the cooled patterned preform remained isothermal in a horizontal distribution and varied in a vertical distribution after cooling the first mold and the second mold only from a single surface of each mold in steps (E) and (E′). Thus, the variance in a horizontal temperature field of the cooled patterned preform was effectively reduced by the present method, thereby obtaining a plate workpiece with high accuracy surface microstructures.

The present embodiment was implemented as described in the aforementioned Embodiment 1. The difference between the Embodiments 1 and 2 was the pattern impressed onto the preform.

In step (D), the preform was disposed between the first mold and the second mold. A load of 280N was applied for pressing the first mold down against the heated preform for about 170 micrometers with a pressing rate of 2.5 micrometers/second to impress the pattern of the first mold onto the preform, and a patterned preform was obtained. In the patterned preform, each groove had a width about 198 micrometers, and every two adjacent grooves had an interval about 252 micrometers inbetween.

After performing a similar cooling step as described in Embodiment 1, the grooves of the plate workpiece had a mean width of 196 micrometers and a width tolerance of 0.1 micrometers. The grooves41also had a mean interval of 250 micrometers between every two adjacent grooves and an interval tolerance less than 0.35 micrometers. It demonstrated that the method succeeded in manufacturing a plate workpiece having surface microstructures with high accuracy.

In brief, a patterned preform can be successfully parted from the first mold by shrinkage if the second mold is directly cooled only from the second surface thereof after pressing. As a result, the quality of the produced plate workpiece with surface microstructures is effectively improved, and thereby a plate workpiece with high accuracy surface microstructures is successfully obtained.