JPH0532209B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to improvements in tape-reel molding methods.
More specifically, the present invention relates to a method of accurately molding a tape reel by improving the cooling efficiency of the fixed cavity core in a tape reel mold having a fixed cavity core provided with a gate and a movable cavity core. [Prior Art] As is well known, a hot runner type tape reel molding mold includes a fixed core and a fixed cavity core provided with a gate, and a movable movable core and a movable cavity core. The cavity is formed by joining the movable core to the fixed core.
Molten tape and reel molding resin is injected through a gate provided on the stationary core, and after the resin filled in the cavity is cooled and solidified, the mold is opened and taken out as a tape and reel molded product. However, in conventional tape and reel molding molds, when the molding cycle is shortened, the fixed side cavity temperature rises, causing problems such as surface runout of the tape and reel molded parts and cylindricity of the tape winding core to rapidly increase. . In order to improve these problems, we conducted extensive studies and found that the cooling efficiency of the cavity in the fixed cavity core on the gate side was reduced due to the inappropriate position of the cooling water channel in conventional molds due to the constraints of the mold structure. Unfortunately, it was found that the temperature difference between the stationary side cavity and the movable side cavity became large, and the surface runout of the reel-molded parts and the cylindricity of the tape core deteriorated. As a result of studies based on this knowledge, we discovered that by increasing the cooling efficiency of the fixed cavity core and using a mold that can cool it uniformly, it is possible to reduce the temperature difference during molding between the fixed cavity and the movable cavity. The present inventors have invented a tape reel molding method that can improve the surface runout and cylindricity of the tape reel and enable high-cycle manufacturing of tape reels. Hereinafter, the present invention will be explained using the drawings. FIG. 1 is a schematic cross-sectional view showing an example of a conventional hot runner type tape reel molding die. In FIG. Fixed side cavity core,
The stationary core 2 is attached to the stationary cavity core 1 and assembled. 3 is a movable cavity core that can be moved into and out of contact with this, and 4 is a movable core, which is assembled by attaching the movable core 4 to the movable cavity core 3. 5 is a cavity formed when these cores are joined. The nozzle of the molding machine (not shown in the figure) is connected to the nozzle contact surface 6 of the mold.
The molten resin is injected into the mold from this nozzle, passed through the runner 7, heated by the hot chip 8, and filled into the cavity through the gate 9. The parting surface 10 is a contact surface between the stationary mold and the movable mold. The fixed side mold includes the above-mentioned fixed side cavity core 1 and fixed side core 2, as well as the fixed side mounting plate 1.
1, manifold block 12, fixed side spacer block 13, fixed side receiving plate 14, fixed side template 1
Consists of 5th grade. On the other hand, the movable mold includes a movable mold plate 16, a movable receiving plate 17, an upper ejector plate 18, a lower ejector plate 19, a movable spacer block 20, a movable mounting plate 21, and the like. The hatched part is the cooling groove, 22 is for gate or hot chip cooling, 2
4 is for cavity cooling of fixed side cavity core,
26 is a cooling groove for cooling the moving side cavity core tape reel side plate, and 28 is a cooling groove for cooling the cylindrical core of the tape reel. 23 is a cooling water inlet/output path to the cooling groove 22, 25 is a cooling water inlet/outlet path to the cooling groove 24, 27 is a cooling water inlet/outlet path to the cooling groove 26, and 29 is a cooling water outlet/outlet path to the cooling groove 28.
This is the cooling water inlet/outlet route. FIG. 2 is a plan view of a main part showing the positional relationship between the cooling groove 24 and the cavity 5 taken along the line A-A' of the stationary cavity core portion 1 shown in FIG. 31 is the outer peripheral end of the cavity of the reel side plate portion, 32 is the outer end of the fixed side cavity core, 33 is the outer peripheral end of the fixed side core, and 25-
1 is the entrance path of the cooling water inlet/outlet path 25 to the cooling groove 24; 2
5-2 indicates the exit path from the cooling groove 24 of 25. In the conventional mold shown in Figs. 1 and 2, it is difficult to process the cooling groove 24 for cooling the cavity on the gate side close to the cavity 5, so the cooling efficiency of the molded product is poor, and the mold is difficult to cool the cavity on the moving side and the fixed side. The temperature difference between
It is large at ~15℃. Furthermore, if the molding cycle is shortened, the temperature of the stationary side cavity increases, resulting in problems such as surface runout of the molded product and cylindricity of the tape core. [Problems to be Solved by the Invention] The object of the present invention is to provide a mold for forming a mold consisting of a fixed cavity core and a movable cavity core to be joined to the fixed cavity core on the gate side. The VTR tape reel obtained by providing cooling grooves as close to the cavity as possible during machining to sufficiently cool the fixed side cavity core and reduce the temperature difference between the moving and fixed side cavity cores. The object of the present invention is to reduce the surface runout of the tape, improve the cylindricity of the tape core, and shorten the molding cycle (injection + cooling time). [Means for Solving the Problem] That is, the present invention uses a hot runner type tape reel mold having a fixed core and a fixed cavity core on the gate side, and a movable core and a movable cavity core opposing these. When injection molding the reel, the cooling grooves provided at the periphery of the fixed side cavity core are divided and processed so that each end is connected by a V-shaped cooling groove, and these multiple V-shaped cooling grooves are The projected surface of the cooling groove portion is provided close to the cavity so that it overlaps with the cavity of the reel side plate, and the temperature difference during molding between the stationary side cavity core and the movable side cavity core is maintained within the range of 0 to 10℃. The present invention relates to a tape-reel molding method characterized by injection molding of resin, and according to the present invention, by sufficiently cooling the fixed side cavity, the temperature difference between the moving side and the fixed side cavity is small. The surface run-out of the tape reel and the cylindricity of the tape core are improved, and the molding cycle (injection +
(cooling time) can be shortened. [Example] Next, FIG. 3 showing a preferred embodiment of the present invention will be described. FIG. 3 shows the mold shown in FIG. 1 in which the cooling groove 24 is placed in the fixed cavity core 1 on the gate side to the top of the side plate of the tape reel so as to be closer to the cavity 5. be. Figure 4 shows A- of the cavity core in Figure 3.
A principal part plan view showing the positional relationship between the cooling groove 24 and the cavity 5 in cross section A' is shown. That is, the cooling groove 24 in the stationary cavity core provided at the peripheral portion is divided into several parts and each end is processed to be connected by a V-shaped cooling groove, and these plural V-shaped cooling grooves are connected. The projected surface of the groove portion overlaps the cavity of the reel side plate. Reference numerals 25-1 and 25-2 indicate a cooling water inlet path to the cooling groove 24 and an outlet path from the cooling groove 24, respectively. As shown in FIG. 2, the cooling grooves 24 of the conventional hot runner type tape reel mold were not located so that their projected surfaces overlapped with the cavities of the reel side plates (that is, within the outer circumferential ends 31). Now, by providing the cooling groove 24 so as to overlap the cavity of the side plate portion (that is, so that at least a portion thereof is inside the outer circumferential end 31) and bringing it close to the cavity,
Efficient cooling becomes possible. Although it depends on the molding conditions such as the molding cycle, the temperature difference between the fixed side and the moving side can be reduced to 0.
It can be lowered to ~10℃. The cooling groove should be installed as close to the cavity as possible, with its bottom separated by at least 2 mm from the surface of the cavity. If the thickness is less than 2 mm, it may be difficult to process. The length is preferably 30 mm or less, more preferably 5 to 20 mm, and is provided at an appropriate position from the viewpoint of processing and mold strength. The width of the groove is such that the projected surface of the cooling groove overlaps the reel side plate of the cavity. The center position of the cooling groove 24 shown in FIG. 3 is, for example, 15 mm from the cavity surface. FIG. 5 shows an example of the relationship between the molding cycle (injection+cooling time) and cavity temperature for the conventional method and the cooling method of the present invention. A is a case using the mold of the present invention as shown in FIG. 3, and B is a case using a mold having conventional cooling grooves as shown in FIG. Regarding the molding cycle, surface run-out of the tape side plate, and cylindricity of the tape winding core when the cooling method is a conventional method (Fig. 1) and when the proximity cooling method, which is an example of the present invention, is used (Fig. 3). It is shown in Table-1.

[Table] The molding conditions in Figure 5 and Table 1 are made using polyacetal resin (Polyplastic VC-10).
was used to inject a VHS type VTR tape reel with a diameter of 89 mm at an injection pressure of 700 Kg/cm ² , an injection speed of 3 m/min, and a mold temperature of 40
The molding was carried out under the conditions of ℃. Surface runout was measured using a surface roughness measuring machine manufactured by Kosaka Laboratory (SE-
4A), and the value is the upper part of the side plate,
This shows the difference between the highest point and the lowest point of downward deformation. The resin molded by the tape-reel molding method of the present invention is not particularly limited as long as it is an injection moldable thermoplastic resin, but polyacetal resin, polyester resin, ABS resin, etc. are suitable. [Effects of the Invention] By using the tape-reel molding method of the present invention, the following remarkable functions and effects are exhibited. (1) By reducing the temperature difference between the moving and fixed cavities and by providing sufficient cooling,
Surface runout and cylindricity are improved. (2) High-cycle molding becomes possible, reducing costs.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an example of a conventional hot runner type tape reel molding mold, FIG. 2 is a plan view of the main part of FIG. 1, and FIG. 3 is an embodiment of the mold used in the present invention. FIG. 4 is a schematic cross-sectional view of an example, FIG. 4 is a plan view of the main part of FIG. 3, and FIG. 5 is a graph showing test results of the conventional cooling method and the cooling method of the present invention. 1...Fixed side cavity core, 24, 24-
1, 24-2... Cooling groove, 1-1, 1-2... Divided block, 25, 25-1, 25-2... Cooling water inlet/outlet passage, 5... Cavity.

Claims (1)

[Claims] 1. When injection molding a tape reel using a hot runner type tape reel mold, which is equipped with a fixed core and a fixed cavity core on the gate side, and a moving core and a moving cavity core opposing these, the inside of the fixed cavity core is The cooling grooves provided on the periphery are divided and processed so that each end is connected by a V-shaped cooling groove, and the projected surface of these multiple V-shaped cooling grooves is the reel side plate. A tape reel, which is provided close to the cavity so as to overlap with the cavity, and is characterized in that the resin is injection molded while maintaining the temperature difference during molding between the stationary cavity core and the movable cavity core within the range of 0 to 10°C. Molding method.