JP4657780B2 - Molding method of resin sheet - Google Patents

Description

  The present invention relates to a molding technique in which a thermoplastic resin sheet is softened by heating and molded with a molding die.

  Generally, when a thermoplastic resin sheet is formed into a desired shape, the heat-softened sheet is lowered from above the mold, and the sheet is placed on the molding surface of the mold and vacuumed or clamped. For example, they are brought into close contact with the molding surface and molded into a desired shape. At the time of molding, problems such as thinning of the sheet occur at locations where the sheet is stretched, and when using a sheet decorated with a texture pattern or satin pattern as the sheet, Problems such as a small remaining depth of the grain at the large part, a large grain pattern, and a glossy surface gloss of the sheet as compared with other parts are likely to occur.

For this reason, in the process of contacting the heat-softened sheet with the mold, the shoulder is provided on the mold corresponding to the peripheral edge of the sheet in order to prevent the portion where the sheet is most easily stretched from being excessively stretched. By providing a pressing member that can press the peripheral edge of the sheet toward the shoulder, and pressing the sheet toward the shoulder with the pressing member when the sheet is brought into contact with the molding surface of the mold, the pressing portion A technique (for example, refer to Patent Document 1) that prevents the sheet on the inner side of the molding portion from being stretched is known. In this technique, the pressing member is configured as a link mechanism so that the contact portion of the pressing member with respect to the sheet does not shift laterally.
JP-A-6-55625

  However, in the above technique, at the stage where the sheet is brought into contact with the molding die, the end of the sheet is pressed against the shoulder by the pressing member, and the inner side of the molding unit is prevented from being extended. Therefore, at the stage where the sheet is brought into close contact with the molding surface by vacuuming or the like after that, it is not possible to prevent the extension of the sheet inside the pressing member, and there is a limit to the prevention of the sheet extension rate. is there.

  Therefore, the present invention further suppresses local elongation of the sheet, prevents the thickness from becoming non-uniform, and prevents problems such as deterioration in appearance in the case of a sheet that has been decorated. For the purpose.

  In order to achieve the above object, the present invention provides a method for molding a resin sheet in which a heat-softened thermoplastic resin sheet is lowered from above a molding die and is brought into close contact with the molding surface of the molding die. When the sheet is lowered and a part of the sheet comes into contact with the protruding portion of the molding surface, at least a part of the vicinity of the protruding portion of the sheet is brought into a non-contact state with respect to the molding surface. The sheet is clamped in a stretched state, and then the sheet holding member is moved to the protruding portion side while holding the non-contact sheet end with a sheet holding member provided in the mold, The non-contact sheet was brought into contact with the molding surface.

That is, the portion where the sheet elongation rate is the largest is generally the side wall portion that intersects the sheet at a large angle in the vicinity of the projecting portion that projects rapidly on the molding surface. Therefore, the side wall portions intersecting at such a large angle are clamped in a state where the sheet is stretched in a non-contact state, and then the sheet holding member that holds the non-contact sheet end is moved to the protruding portion side. If moved, the sheet of the same part can be relaxed (image such as replenishing the amount of sheets necessary for molding), and the local elongation is alleviated.
At this time, since the outer portion (the portion opposite to the protruding portion) of the sheet holding portion held by the sheet holding member is extended, this portion should be a non-product portion (outside design portion). It is preferable.

  In molding the heat-softened thermoplastic resin sheet with a molding die, when the sheet contacts the projection of the molding die, a part of the vicinity of the projection of the sheet is brought into a non-contact state with respect to the molding surface. If the sheet holding member that holds the sheet end portion in the non-contact state is moved to the protruding portion side, a space is generated in the sheet portion that was initially non-contact, and the elongation rate can be suppressed. Molding defects due to elongation are suppressed.

Embodiments of the present invention will be described with reference to the accompanying drawings.
Here, FIG. 1 is an explanatory view showing a part of a forming die to which the forming method according to the present invention is applied, and FIG. 2 is an explanatory view of the forming method.

  The method for molding a resin sheet according to the present invention suppresses the heat-softening of a thermoplastic resin sheet and suppresses even when the molding shape is complicated and local elongation tends to occur when molding is performed following the molding surface of the mold. Thus, the appearance is not deteriorated, and the sheet is particularly characterized in that it is formed with a space in the sheet where the sheet is easily stretched.

Therefore, first, an outline of a mold in which the present molding method is adopted will be described with reference to FIG.
This molding die is configured as a vacuum molding die for vacuum molding a thermoplastic resin sheet to be heat-softened. As shown in FIG. 1, the molding die is provided with a molding surface having a protruding portion 1t on the surface and a large number of molding surfaces. A first mold 1 in which a vacuum hole is formed; a second mold 2 that is movable up and down above the first mold 1; and a gripping frame 3 that grips the peripheral edge of the sheet W. The grip frame 3 is disposed between the first and second molds 1 and 2 and is movable up and down with respect to the first mold 1.

  The first mold 1 is provided with a first core 4, which is slidable in the horizontal direction along the guide member 5, and normally, by a restoring mechanism (not shown). 1 is moved to the left position shown in FIG.

  The second mold 2 is provided with a second core 6 that is slidable in the horizontal direction with respect to the mold body. When the second mold 2 is lowered, the second core 6 is located near the outside of the first core 4. When the second core 6 descends and slides horizontally inward toward the molding surface side, the first core 4 is pressed to slide together with the first core 4.

The present molding method using the above mold will be described with reference to FIG.
A thermoplastic sheet W such as TPO or PP sheet gripped by the gripping frame 3, which is decorated with a concavo-convex pattern, leather pattern, texture pattern such as a geometric pattern, or satin finish, etc. at about 180 ° C. After heating to a temperature at which molding is possible, the sheet W is brought into contact with the first molding die 1 by lowering the second molding die 2 and the grip frame 3. Then, as shown in FIG. 2A, the sheet W first comes into contact with the protruding portion 1t of the molding surface. The mold temperature of the first mold 1 at this time is a temperature at which a sheet of about 70 ° C. can be solidified.

  Then, when the second mold 2 and the gripping frame 3 are further lowered, as shown in FIG. 2B, a part of the sheet W becomes the first core 4 of the first mold 1 and the second mold 2. The sheet W between the apex of the projecting portion 1t and the holding portions of the first and second cores 4 and 6 is formed at the stage where the clamping is finished and is held between the second core 6 The surface is pulled without contact. In addition, this location is usually a location where the expansion rate of the sheet W is the largest.

  Next, as shown in FIG. 2C, when the second core 6 is advanced, the first core 4 is also pushed across a part of the sheet W, and the apex of the protruding portion 1t and the first and second portions The sheet W between the holding parts of the cores 4 and 6 comes close to the molding surface. If the vacuum is pulled from the vacuum pulling hole of the first mold 1, the sheet W between the apex of the projecting portion 1 t and the holding portions of the first and second cores 4 and 6 is not greatly stretched. In addition to preventing the thickness of the portion from being reduced, it is possible to prevent problems such as changes in the texture depth and pattern such as a texture pattern, and differences in gloss.

On the other hand, the sheet W of the outer portion (the left portion in the figure) of the holding portions of the first and second cores 4 and 6 is increased in elongation and is likely to be thinned and deteriorated in quality. This portion is a non-product portion outside the product surface portion and is removed by trimming later, so that the appearance quality is not deteriorated.
By the above procedure, the elongation of the portion of the product surface portion where the sheet W is most likely to be stretched is suppressed, the thinning is prevented, the texture pattern is not changed, and the molding quality can be improved.

In addition, this invention is not limited to the above embodiments. What has substantially the same configuration as the matters described in the claims of the present invention and exhibits the same operational effects belongs to the technical scope of the present invention.
For example, the raw material of the thermoplastic resin sheet W is arbitrary, and the shape of the molding surface of the first mold 1 is an example.
Furthermore, this forming method is not limited to vacuum forming.

  When molding a heat-softened thermoplastic resin sheet with a molding die, it suppresses local elongation, prevents thinning, and prevents quality defects such as changes in wrinkle patterns. A molded product can be formed.

Explanatory drawing which shows a part of shaping | molding die with which the shaping | molding method concerning this invention is applied Illustration of this molding method

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st shaping | molding die, 1t ... Projection part, 2 ... 2nd shaping | molding die, 4 ... 1st core, 6 ... 2nd core, W ... Resin sheet.

Claims (1)

A method of molding a resin sheet in which a heat-softened thermoplastic resin sheet is lowered from above a molding die and is closely adhered to a molding surface of the molding die, the thermoplastic resin sheet being lowered, and the molding surface When a part of the sheet comes into contact with the protruding part of the sheet, at least a part of the vicinity of the protruding part of the sheet is held by the sheet holding member provided on the mold and the sheet is stretched, so that a step of clamping the part in a non-contact state with respect to the molding surface, thereafter, the sheet holding member is moved to the projecting portion, a non-contact state sheet comprising the step of contacting the molding surface A method for molding a resin sheet characterized by the above.