JPS5845037A - Runnerless injection molding method - Google Patents

Abstract

PURPOSE:To produce an inexpensive mold that does not require a sprue or a runner part, by forming a nozzle into a projected shape and the gate of a mold into a recessed cone shape, and bringing them into contact with each other. CONSTITUTION:The mold 1 having a cavity 2 is formed with a cone surface 3 having about 90 deg. (the angle alpha). On the other hand, the nozzle 4 is formed with a cone 6 that will abut on the cone surface 3. The nozzle and the mold are abutted and centered to perform a runnerless injection molding.

Description

[Detailed description of the invention] The present invention relates to a runnerless injection molding method.

A typical mold is provided with a sprue and a runner, and the molten resin injected from the nozzle of the injection molding machine flows through the sprue part and the runner part into the cavity where the product will be produced. However, although the resin in the capitice is taken out as a product, the resin in the sprue runner remains as N and is cooled and solidified.
Removal is necessary for each molding cycle, and the removal work is extremely troublesome. In addition, the resin left in the sprue and launch section and cooled and solidified is discarded, but it is crushed and recycled, so if it is discarded, it is a waste of material, and when it is recycled, there is a lot of work time and energy loss. . Therefore, molds that can economically perform molding without using sprues or runners, ie, runnerless molds, have come to be used.

For example, a bot runner that does not solidify the sprue portion or runner portion, or an extended nozzle method in which the nozzle of an injection molding machine extends and directly contacts the mold gate are known. However, these methods require a heating device for heating the bot runner or the extended nozzle, making the mold complex and expensive.

The object of the present invention is to provide a runnerless injection molding method in which the nozzle tip directly contacts the mold cavity without using an extension nozzle, hot runner, etc. as in the conventional method.
To explain the present invention in more detail, alignment is performed by bringing the concave and conical surfaces of the nozzle tip and the mold into contact with each other, and a land portion is placed at the bottom of the concave conical surface provided on the mold side. The gate of the sharp edge that is not provided is opened, and the shape of the nozzle side that comes into contact with the concave conical surface is a truncated conical shape having a flat part with the same diameter as the nozzle opening diameter at the tip, and the sprue and runner are connected from the nozzle opening. This is an injection molding method in which resin is directly injected into the cavity without any molding.

Next, one embodiment of the present invention will be explained with reference to FIG. 1.
is a mold having a cavity 2. Reference numeral 3 denotes a concave conical surface provided on the mold 1, and the bottom thereof has no land portion and a gate 5 opens directly into the cavity 2. A sharp edge is provided so that no protrusion remains on the molded product when the gate 5 is cut after molding. The angle α of the conical surface 3 is determined based on mold strength constraints, securing the flow path area of the nozzle, centering when the nozzle and mold come into contact, and preventing resin leakage during injection. It is necessary to decide based on securing the surface pressure, but it is recommended to set it at approximately 90 degrees (but it is possible to fully perform its function within the range of 20 degrees. 4 is the nozzle, and the tip is attached to the mold l mentioned above. It has a truncated conical shape 6 that protrudes from the concave conical surface 3 provided, and a nozzle opening 7 is provided with the same diameter as the tip surface.

Moreover, the uneven conical surfaces are mutually Kl! It is effective for centering fences that have a large contact area, but if the V is too large, the amount of heat oscillating from the nozzle side to the metal fittings will be large, making it easy for the temperature of the nozzle to drop, so keep it to the minimum necessary. It is necessary that 1
According to tests conducted by the inventors, the appropriate length of the conical surface VcfB from the tip is 3 to 81 degrees and 111 degrees.
ii I was able to do it.

With the above configuration, since the resin remains in the sprue and runner parts, not only is there no waste, but the molding structure is simple and inexpensive.

Since the metal structure is simple, there is no need to waste time when changing one color, and there is no need to consider the cooling time of the sprue and launch parts. The gold 11 perpendicular to the axis A of the conical part
Even more effective centering can be achieved by letting mec&if move plane C.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a state before a mold and a nozzle come into contact, showing one embodiment of the present invention. FIG. 2 is a diagram showing another embodiment of the present invention, in which the nozzle is in contact with the mold. 1... Mold, 3... Concave conical surface, 4... Nozzle,
5...Gate, 6...Truncated conical surface, 7...Nozzle opening. Applicant: Toshiba Machine Co., Ltd.

Claims (1)

[Scope of Claims] 1. Align the nozzle tip and the mold by bringing their convex and conical surfaces into contact with each other, and aligning the nozzle tip and the mold with the bottom f of the concave conical surface provided in the mold. A sharp edge gate opens directly into the mold cavity, and the nozzle shape west of the concave conical surface is a truncated conical surface whose tip surface is a plane with the same diameter as the nozzle opening;
A runnerless plane having a plane perpendicular to the injection axis is provided, the nozzle opening is in close contact with the gate of the mold during injection molding, and the molten resin from the nozzle opening is directly injected into the gate; A patented molding method characterized by bringing the two halves into close contact during injection molding. 3. The apex angle of the cone on the uneven conical surface is 90. Claim 1 characterized in that the angle is ±20°.
Runnerless injection molding method according to Items 1 and 2. 4. The runnerless injection molding method according to items 1 to 3 above, wherein the convex and concave surfaces are in contact with each other over a length of 3 to 8 liters along the conical surface from the tip of the nozzle part. .