JPH06293046A - Resin and color replacing method of injection molding machine - Google Patents

Abstract

PURPOSE:To easily and rapidly replace a resin and a color, in the resin and color replacing method in the cylinder of an injection molding machine, by discharging the residual resin in the cylinder in spite of a low viscosity resin. CONSTITUTION:In an injection molding machine of a low viscosity resin, a screw 7 is allowed to retreat by a specific quantity and subsequently rotated to perform plasticization. Thereafter, in such a state that the rotation of the screw is stopped, the advance A and retreat B of the screw are repeated so as to reach an advance limit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for changing resin of a low-viscosity resin and a method for changing resin of an injection molding machine suitable for changing color.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, when a high-viscosity resin such as nylon is changed or a color is changed, it is generally performed manually or automatically by the following method. This method will be described with reference to FIGS. 1 and 4. In FIG. 1, 1 is a hopper, 2 is a discharge port, 3 is a screw cylinder, 4 is an end cap, 7 is a screw, 8 is a taper portion, 9 is a screw head taper portion, 10 is a resin. To replace the resin, first remove the resin from the popper 1
It is completely removed by using, and the process is performed according to the process diagram shown in FIG. Note that, here, the steps after the new resin is put into the hopper 1 will be described.

First, when the screw 7 is rotated by a predetermined stroke for plasticization, the resin has a high viscosity, so that the resin stays in the cylinder 3 from the end cap 4 of the screw 7. Therefore, the screw 7 is retracted (plasticized retreat) up to the retreat limit. The stroke can be set with a limit switch, potentiometer, encoder, timer, or the like. 1 as shown in FIGS. 1 and 4.
The screw is moved forward A, backward B, forward A,
Repeat retreat B multiple times. At this time, the screw does not rotate.
At this time, the distance L1 for moving forward once is made larger than the distance L2 for moving backward once so that the forward limit is reached in several times.

Next, after the screw reaches the forward limit, when the screw 7 is rotated again for plasticization, the screw is retracted to the backward limit, and therefore the above-mentioned steps are repeated. Through the above steps, the high-viscosity resin 10 accumulated in the taper portion 8 of the end cap 4 and the screw head taper portion 9 is replaced with a new resin.

[0005]

However, it is a resin such as nylon or polycarbonate having a high viscosity property that the color and resin can be changed by the conventional steps as described above. However, even if a low-viscosity resin such as polypropylene is used in the above-mentioned conventional process, it is difficult to successfully change the color and the resin. That is, even if the plasticizing step is performed while rotating the screw, the low-viscosity resin is discharged from the nozzle, and the resin does not stay in the screw. Therefore, it is difficult to replace the resin of the taper portion of the end cap and the screw head taper portion with a new resin. The present invention is intended to solve the above-mentioned conventional problems, and to provide a method capable of changing the color and the resin of a low-viscosity resin.

[0006]

Therefore, in the present invention, as a resin changing method and a color changing method of an injection molding machine for a low-viscosity resin, after the screw is retracted by a predetermined amount, the screw is rotated to perform plasticization, Thereafter, with the screw rotation stopped, forward and backward movements of the screw are repeated until the forward limit is reached, and this is a means for solving the problem.

[0007]

In the present invention, the screw is first retracted to the predetermined position by the above means. Then, the screw is rotated to plasticize the resin. After that, with the screw rotation stopped, the screw is repeatedly moved forward and backward until the forward limit. As described above, by retracting the screw before the plasticizing step, the resin can be retained in the cylinder, and even the low-viscosity resin can be replaced with the resin and the color can be changed.

[0008]

Embodiments of the present invention will be described with reference to FIGS. 1 to 3. 1 is a hopper, 2 is a discharge port, 3 is a screw cylinder,
4 is an end cap, 7 is a screw, 8 is a tapered portion, 9
Is a screw head taper portion, and 10 is a resin. Next, the method will be described by taking a resin change of polypropylene, which is one of the low-viscosity resins, as an example. First, the polypropylene resin is completely removed from the hopper 1 using the discharge port 2. Then, as shown in FIG. 2, the screw 7 is forcibly retracted to the retract limit (predetermined), and new low-viscosity resin is charged into the hopper 1. Next, the screw 7 is rotated to perform plasticization. The resin stays in the tip of the cylinder 3. Then, as in the conventional case, the screw 7 is repeatedly moved forward and backward. That is, as shown in FIG. 3, the screw 3 is repeatedly moved forward A, backward B, forward A, and backward B in one injection process, but the screw does not rotate at this time. At this time, the distance L1 for moving forward once is made larger than the distance L2 for moving backward once so that the forward limit is reached in several times. The forward and backward distances are set by limit switches, encoders, potentiometers and timers.

Next, after the screw 7 reaches the forward limit,
The screw 7 is retracted to the rear limit again. Then, the screw 7 is rotated to perform plasticization, and the above steps are repeated. By retracting the screw before plasticizing in this way, even if the resin has a low viscosity, the resin remaining in the taper portion 8 of the end cap 4 and the screw head taper portion 9 is replaced with a new resin. be able to. That is, the resin accumulated in the cylinder disturbs the flow of the resin as the screw moves forward and backward, and the applied resin is peeled off by applying an impact, so that the resin can be changed and the color can be changed quickly. Further, the resin 11 surrounded by the check ring 5 and the check ring portion 12 of the screw head 6 moves the check ring 5 forward and backward by moving the screw forward and backward in a short time, disturbing the flow between both check ring portions, A resin can be changed and a color can be changed quickly by giving an impact.

[0010]

As described in detail above, according to the resin changing and color changing method of the injection molding machine of the present invention, the resin is retained in the cylinder by retracting the screw before plasticizing. it can. Therefore, even if the resin has a low viscosity, the residual resin in the cylinder can be easily and quickly discharged.

[Brief description of drawings]

FIG. 1 is a side sectional view of an injection molding machine.

FIG. 2 is a side sectional view showing a state in which a screw is retracted in a cylinder.

FIG. 3 is an explanatory view showing a resin changing or color changing process according to the present invention.

FIG. 4 is an explanatory diagram showing a conventional resin replacement or color replacement process.

[Explanation of symbols]

 1 Hopper 3 Cylinder 7 Screw

Claims (1)

[Claims] 1. In a low-viscosity resin injection molding machine, after the screw is retracted by a predetermined amount, the screw is rotated to perform plasticization, and then the screw is advanced and retracted to the forward limit while the screw rotation is stopped. A method of changing the resin and color of the injection molding machine, which is repeatedly performed until.