JPH03215019A - How to bend plastic sheets - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to a method for folding plastic sheets, which allows plastic sheets to be folded at high speed and with high precision. [Prior art and problems to be solved by the invention] Conventional methods for bending plastic sheets include: As shown in the cross-sectional view in Figure 6, a plastic sheet l is placed on the pedestal 3.
Place! Then, it is sandwiched between the heating plate 41 and the pedestal 3, and bent by pressing from both sides with the bending jig 5. When it is sufficiently bent, the heating plate 41 is removed and it is cooled with air or the like. Alternatively, after cold bending, a heating plate 41 is applied to heat the sheet and cool it. Both of the above methods require a cooling step after heating, so processing takes time. Furthermore, if a part of the plastic sheet other than the folded part is heated even slightly, the area around the folded part will expand and contract, resulting in deformation and precise bendability and dimensional accuracy, making it especially difficult to bend thin sheets. In addition, in the case of a bent product as shown in the perspective view in Figure 2, the bending angle tends to change if heat treatment is performed under the same conditions at the center and both ends, and it is necessary to correct this by creating a temperature distribution in the length direction. However, it is difficult to accurately bend the heating plate because it is difficult to create an accurate temperature distribution. <<Means for Solving the Problems>> In order to solve the above-mentioned problems, the present invention utilizes laser light as a heating means to heat only the bent portion at once. A method for bending a plastic sheet, which is characterized by heating and softening the bent portion of the sheet with a laser beam and then bending it along the bent portion; This is a method for bending plastic sheets, which is characterized by heat treatment with light.The following describes the method in detail with reference to the drawings. FIG. 1 is a side sectional view showing an example of an apparatus for carrying out the method of folding a plastic sheet of the present invention, and FIG. 2 is a perspective view showing an example of a folded product obtained by applying the present invention. 3 to 5 are side sectional views showing other examples of an apparatus for carrying out the method of folding a plastic sheet according to the present invention, and FIG. 6 is a side sectional view showing a conventional method for folding a plastic sheet. FIG. 2 is a side sectional view showing an example of a processing device. As shown in FIG. 1, the method of the present invention involves heating and softening a bent portion 11 of a plastic sheet 1 with a laser beam 2, and then bending it along the bent portion. First, the plastic sheet 1 is placed on a pedestal 3 having the same shape as the shape to be bent, and the plastic sheet 1 is sandwiched between the holding plate 4 and the pedestal 3 and fixed. The bent portion 11 at the edge of the pinched portion is then irradiated with laser light 2 to heat and soften it. Next, by pressing the plastic sheet 1 in the direction of the pedestal 3 using the bending tools 5 on both sides, the plastic sheet 1 is bent along the pedestal 3 from the bent portion 11. Then, the bending process is completed by cooling by contacting the pedestal 3 or presser plate 4 or by blowing cooling air. Furthermore, as shown in Figure 1, if the plastic sheet is thick, it is possible to irradiate from both sides, and it is also possible to irradiate the front and back sides by changing or shifting the irradiation time. By doing this, the heating time is further shortened, the angle of the bent portion is accurate, and a sharp bending process with less radius on the inside can be achieved.

Further, as shown in FIG. 3, a plastic sheet 1 is placed on a pedestal 3, clamped with a presser plate 4, and bent with a double-opening folding tool 5. It is also possible to heat-treat the bent portion by irradiating it with By irradiating the folded portion of the folded sheet with laser light to raise the temperature to a high temperature, there is an advantage that the heat resistance of the folded portion is improved.

Then, as shown in FIG. 4, the bent product 12 that was bent in a separate process is fixed in a support mold 6 that matches the outer shape of the product.
The bent portion 11 may be heat-treated by irradiating the laser beam 2 from the inner surface of the bent product 12. Since only a very limited area can be heated with laser light, the cooling speed is also fast. The laser beam 2 needs to be used in various ways depending on the physical properties of the sheet, but a carbon dioxide (CO2) laser or the like can be used. Conditions such as making the laser beam stronger and thicker or heating it for a longer time can be freely changed depending on the sheet thickness, material, bending angle, etc. By deflecting the laser beam, the entire bent part can be heated freely in a continuous straight line, a curved line, or a dotted line. The shape of the irradiated area can also be freely obtained. Alternatively, the heat treatment may be performed in multiple stages, such as intermittently irradiating the laser beam in the first stage, and then irradiating and heat-treating the unirradiated portions in the second P1 stage. By adjusting the position and degree of heating in this way, deformation and distortion of the folded part can be minimized, and even with the folded product shown in Figure 2, the degree of heating can be adjusted in the length direction of the folded part. By doing so, both the center and both ends can be bent at the same angle. For example, in the case of a sheet that has been rolled and heat-set, such as a biaxially rolled polyester sheet, heating the entire length of the folded part will make it brittle, but by irradiating the folded part in a dotted manner with a laser beam, the folded part can be heated. It is possible to obtain bent products with a good balance of heat resistance and strength. If the oscillation wavelength of the laser beam and the physical properties and material of the sheet are used in a certain manner, the inside of the sheet will be heated quickly. For example, polyvinyl chloride sheets have high absorption of far-infrared and infrared wavelengths, and can be heated efficiently.

The heating width of the laser beam in the above method depends on the material and physical properties of the sheet, thickness, color tone, bending angle, shape of the bent part, processing speed, shape of the sheet, laser wavelength, irradiation time, laser output, etc. Although there are differences, in general, if it is less than 0.3 times the thickness of the plasti-solite, stress will concentrate on the irradiated area and cracks may occur, and if it is more than 5 times the thickness, the heating width will be widened. As a result, precise bending accuracy cannot be obtained, and deformation around the bent portion may occur.

In the case of plastic sheets, where irradiation with laser light will cause the surface of the sheet to become rough and cause problems with gloss and appearance, as shown in Figure 5, irradiation of multiple sheets of plastic sheet 1 with laser light After the bending process, the rough outer surface of the plastic sheet l3 is peeled off using a laser beam. Only the middle plastic sheet 14 can be used as a product. Of course, the outer surface can be made of a material that is highly heat resistant and hard to roughen, and can be used as a product without peeling. Furthermore, burrs and protrusions that occur during bending and sheet punching can be removed using laser light during the bending process, resulting in beautiful products. <<Example>> Next, an example will be explained. As a plastic sheet, hard polyvinyl chloride sheet (product name: Vinyfoil C-8) is used.
As shown in Fig. 2, a shutter for a 3.5-inch floppy cassette was bent into an approximately U-shape using a 3.5-inch floppy cassette shutter (flexibility temperature: 85°C, thickness: 0.3 mm). First, as shown in FIG. 3, the plastic sheet 1 is placed on the pedestal 3, and the holding plate 4 is placed between the plastic sheet 1 and the pedestal 3.
At this time, if the presser plate is heated (60 to 120°C), it can be bent more easily.Next, after bending the plastic sheet 1 with the bending jig 5, a laser beam is applied to the bent part 11. Irradiate and heat treat.

The laser used was one with a carbon dioxide (c O 2 > method) continuous wave operation and an output range of 8 ow, and the oscillation wavelength was 1
O,6 μm (infrared rays) is adopted, and the internal method is a galvanometer type with a total length of 47 mm (shutter width).
It was heat-treated by making it reciprocate 10 times in 0.3 seconds with a width of mm so that the surface temperature of the bent part became 100''C to 110゛C, and after cooling it with cold air for 0.5 seconds, it was taken out from the pedestal 3. A heat-resistant shutter with no deformation of the bent portion even under heating conditions of 70°C x 6 hours was obtained.Furthermore, the plastic sheet held by the pedestal 3 and the bending jig 5 was fixed. 47 in 0.3 seconds under a laser beam
A similar product was also obtained by heat treatment by moving at a speed of mm. (Effects of the Invention) As explained above, since the present invention heats the bent portion of a plastic sheet using laser light, it has various effects as shown below. 1) Since the laser beam is extremely thin and the thickness etc. can be freely adjusted, it can be selectively irradiated to prevent heating of areas other than the folded part, thus allowing folding with good precision and a beautiful finish.

2) By making the heated part thinner, cooling time is shortened and processing speed is improved. 3) Heating conditions can be set extremely quickly by adjusting laser output, irradiation time, etc. according to wall thickness, material, bending angle, etc. 4》By adjusting the laser beam pattern and intensity, it is possible to set the best heating conditions according to the characteristics of the material forming the plastic sheet and the required bending shape, which is impossible with conventional heating bending methods. It has become easier to bend materials and bend shapes.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of an apparatus for carrying out the method of folding a plastic sheet of the present invention, and FIG. 2 is a perspective view showing an example of a folded product obtained by applying the present invention. 3 to 5 are side sectional views showing other examples of an apparatus for carrying out the method of folding a plastic sheet according to the present invention, and FIG. 6 is a side sectional view showing a conventional method for folding a plastic sheet. FIG. 2 is a side sectional view showing an example of a processing device.

Claims (1)

[Claims] 1) A method for folding a plastic sheet, which comprises heating and softening the folded portion of the plastic sheet with a laser beam, and then folding the plastic sheet along the folded portion. 2) Folding and holding the plastic sheet; A method for bending a plastic sheet, characterized by heat-treating the bent portion with laser light.