JPH0443497B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a hollow double-walled plastic molded article having holes using blow molding.

[Conventional technology]

Conventionally, in order to manufacture a hollow double-wall plastic molded product having holes using blow molding, holes are finally formed in one cavity 43 of a pair of split molds 41 and 42, as shown in FIG. A convex portion 45 is provided for this purpose, and the parison in a plasticized state is compressed by the convex portion 45 and welded and integrated to form a hole burr portion 4F, and the parison 40 surrounded by cavities 43 and 44 is blow molded. After cooling, the molded product was taken out of the mold, and then the hole burr 4F was cut off with a cutter or the like to produce a hollow double-walled molded product having holes.

[Problem that the invention seeks to solve]

However, in the case of the above manufacturing method, the following
It had problems (1), (2), and (3).

(1) The viscosity of the parison plasticized in blow molding is usually 2×10 ³ Poise or more, and the pressing force of compressed air to expand the parison is usually 3 to 15 kg/cm ² , so it is difficult to use a hole burr. There is a limit to the thinning of parts by compression, and as a result, thick parts must be removed when removing burrs, making it difficult to remove burrs.

(2) Also, by compressing the plasticized plastic in the hole burr, the compressed plastic is pushed toward the hollow double wall molding cavity side, creating a buildup, which causes the hollow double wall There was a problem that the molded product was deformed and the molding cycle became longer due to the cooling time.

(3) Furthermore, it was necessary to insert a cutter or the like into the hole burr and cut along the periphery of the hole, making it difficult to finish the hole beautifully as it was easy to make an unexpected cut on the periphery of the hole. .

The present invention solves the problems (1), (2), and (3) above, and provides a hole that is easy to remove burrs, does not cause buildup in the molded product, and can be finished beautifully. An object of the present invention is to provide a method for manufacturing a hollow double-walled molded product having the following characteristics.

[Means for Solving the Problems] The present invention has the following technical means for achieving the object. That is, the present invention includes (A) disposing a parison between the split molds having a convex portion in the cavity of one split mold and a recess in the cavity of the other split mold, and (B) disposing the parison between the split molds. As the mold clamping progresses, the parison is clamped between the outer periphery of the protrusion and the opening edge of the recess, and (C) the mold is further clamped to fit the protrusion into the recess, thereby enclosing it between the protrusion and the recess. (D) The hole burr part of the parison is pushed outward, and the base end of the hole burr part is thinned by the shear force generated by the outer periphery of the convex part and the opening edge of the recess. (E) The molded product is removed from the mold after cooling, and the proximal end of the burr for the hole is then cut off. The present invention relates to a method for manufacturing a hollow double-walled molded product.

In the present invention, a hollow double-wall molded product is a product made by blow molding thermoplastic plastic such as polyethylene, polypropylene, polyamide, or ABS.
Cases with circular or square holes, such as cases for storing tools, housings for computer equipment, containers for transporting parts, etc.
Other examples include plate-like members and box-like members that have a hollow space between adjacent double walls.

[Effect]

In the present invention, the base end of the hole burr is thinned by the shear force generated by the outer periphery of the protrusion provided in the cavity and the opening edge of the recess, so the cutting force required for removing the burr is small and the burr removal process is easy. is easy. In addition, as the split mold progresses, the parison is squeezed by the outer periphery of the convex part and the opening edge of the concave part, so the plastic in the hole burr part is pushed to the hollow double wall cavity side as much as in the past. There is no problem and there is no accumulation of meat. Furthermore, by advancing the mold clamping and fitting the convex part into the recess, the burr part for the hole of the parison surrounded by the convex part and the concave part protrudes outward from the outer surface of the main body of the hollow double-walled molded product. Therefore, by moving a cutter or the like along the outer surface of the main body, a beautiful finish can be achieved, and the work of removing burrs is also facilitated.

[Example] An example of the present invention will be described below based on the drawings.

FIG. 1 shows a housing panel 1 of a computer equipment a, which is an example of a hollow double-walled molded product having holes manufactured by the manufacturing method of the present invention. It has a hollow double wall structure with a hollow part 4 between an inner wall 2 and an outer wall 3 made of plastic. The panel 1 is provided with a large number of air vent holes 5, and the outer wall 3 is provided with a slightly uneven textured surface.

FIGS. 2 to 5 explain the manufacturing method of the present invention step by step. In the figure, 10 is parison,
11 and 12 are a pair of split molds; 13 is an outer wall 3 of the panel 1, which is an example of a hollow double-wall molded product having holes;
A recessed cavity 14 for forming the inner wall 2 of the panel 1 is a protruding cavity 14 for forming the inner wall 2 of the panel 1, and the cavity 13 is carved with a grain. Cavity 1 of one split mold 11
A convex portion 15 is formed in the cavity 14 of the other split mold 12, and a recess 16 is formed in the cavity 14 of the other split mold 12. It is formed in a position where A tapered inclined surface is formed on the outer periphery 15a of the convex portion 15, and the gap D1 of the opening edge 16a of the recess ₁₆ is smaller than the maximum outer dimension _D2 of the inclined surface 15a and larger than the minimum internal dimension _D3 . It is set. Also, 1
7 is the extrusion head of parison 10.

First, as shown in FIG. 2, plasticization is carried out between the split molds 11 and 12, which have a protrusion 15 in the cavity 13 of one split mold 11 and a recess 16 in the cavity 14 of the other split mold 12. The plastic thus obtained is extruded from an extrusion head 17 as a parison 10 and placed. Next, as shown in FIG.
As the molds 1 and 12 are clamped, the parison 10 is clamped between the outer periphery 15a end face of the convex part 15 and the opening edge 16a of the recess 16, and the mold clamping is further progressed to form the convex part 1.
5 into the recess 16 from the opening edge 16a, the hole burr F of the parison 10 surrounded by the projection 15 and the recess 16 is pushed outward from the cavity 14 for forming the inner wall, and The base end _F1 of the hole burr F is connected to the outer periphery 15a of the convex part 15 and the recess 1.
0.1 m due to the shear force due to the opening edge 16a of 6.
Thin the wall to about 1mm. Then, pressure fluid is introduced into the parison 10 and the cavity 13,
By blow molding the parison 10 surrounded by 14, an inner wall 2 having a thickness of about 2 mm to 4 mm is formed.
and molding the outer wall 3. Note that the introduction of the pressure fluid may be started before the mold clamping is completed.

Next, the molded product is cooled in the split molds 11 and 12 and then taken out from the split molds 11 and 12, and the cutter 18 is moved along the outer surface of the inner wall 2 to form a hole burr F as shown in FIG. A hole 5 is formed by cutting out the thinned proximal end _F1 of the panel 1 as shown in Fig. 1.
Manufacture.

FIG. 6 shows another example of a split mold, in which the cavity 23 of the other split mold 21 is
form parallel convex portions 25, and one split mold 22
The gap D4 between the opening edge 26a of the recess 26 formed in the cavity 24 and the convex portion 25 is set to 0.1 mm to 1 mm. FIGS. 7 and 8 show another example of a split mold, in which a protrusion 35 with a large number of knurled grooves 35b is formed in the cavity 33 of the other split mold 31, and a hole burr is provided. F
The proximal end _F1 is made thinner in the form of a perforation.
Further, in FIG. 7, an opening end 36a of a recess 36 formed in the cavity 34 of one of the split molds 32 is formed with a circular inclined surface that widens toward the end and has a length of about 2 mm to 5 mm.

If the hole burr F is cut off on the inner wall 2 side, which is the opposite side of the outer wall 3 on which the textured surface is formed, as shown in the above embodiment, the textured surface of the outer wall 3 will not be damaged. In addition, the outer periphery 15 of the convex portions 15, 35
By forming slopes on a and 35a, mold clamping can be performed accurately, and the base end _F1 of the hole burr part F can be thinned uniformly over the entire circumference. , the cutting operation of the hole burr portion F becomes easier.

〔Effect of the invention〕

As described above, the manufacturing method of the present invention allows for easy burr removal work, eliminates buildup in the molded product, allows holes to be beautifully finished, and even for hollow double-walled molded products with a large number of holes. , can be manufactured very rationally.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing a housing panel of a computer device, which is an example of a hollow double-walled molded product having holes manufactured by the manufacturing method of the present invention, and FIGS. 2 to 5 are views of the present invention. The manufacturing method is shown in the order of steps; Figure 2 is a cutaway front view of the mold, and Figure 3 is a
4 and 4 are sectional views of the main parts of the mold, FIG. 5 is a sectional view of the main parts of the molded product, and FIGS. 6 to 8 show other examples of the split mold used in the present invention. Figures 6 and 7 are sectional views of the main parts of the mold, Figure 8 is a front view of the protrusion 35 shown in Figure 7, and Figure 9 is a split mold used in the conventional manufacturing method. It is a sectional view of the main part. 1: housing panel, 2: inner wall, 3: outer wall,
4: Hollow part, 5: Hole, 11: One split mold, 1
2: The other split mold, 15: Convex portion, 16: Concave portion.

Claims (1)

[Claims] 1 A parison is placed between the split molds having a convex part in the cavity of one split mold and a recess in the cavity of the other split mold, and as the mold of the split mold progresses, the outer periphery of the convex part and The parison is clamped by the opening edge of the recess, and the mold is further tightened to fit the protrusion into the recess, thereby pushing the hole burr of the parison surrounded by the protrusion and recess outward. At the same time, the proximal end of the hole burr is thinned by shearing force caused by the outer periphery of the convex part and the opening edge of the recess, and the parison surrounded by the cavity is blow molded to form a hollow double wall structure. A method for producing a hollow double-walled molded product having a hole, the method comprising: removing the molded product from the mold after cooling, and then cutting off the proximal end of the hole burr.