KR100307920B1 - Injection screw of injection device - Google Patents

Abstract

The present invention prevents black spots and silver streak due to carbonization phenomenon that is generated during melting / injection of a resin sensitive to shear rate, and also significantly shortens the plasticization time, thereby reducing cycle time. The injection screw of the injection device designed to improve the productivity,

Flight 104 having a pushing flight 104A and a trailing flight 104B in an axially continuous spiral on the outer circumferential surface of the screw shaft 102 rotatably built up in the cylinder barrel 50. And 70mm-150mm in diameter to melt / feed the resin material sensitive to shear rate such as flame-retardant ABS, flame-retardant PC + ABS synthetic resin, PC, PMMA, rigid PVC, etc. In the injection screw,

A predetermined section of the screw shaft 102 is divided into a supply unit 106 having a constant flight depth, a compression unit 108 having a tapered flight bone diameter, and a metering unit 110 having a constant constant flight diameter, The rounding (R) values of the pressing flight 104A and the trailing flight 104B of the compression unit 108 / metering unit 110 are varied.

Description

Injection screw of injection device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection screw applied to an injection apparatus. In particular, the present invention prevents black spots and silver streak due to carbonization caused by melting / injection of a resin sensitive to shear rate, and also plasticizes. The present invention relates to an injection screw of an injection apparatus, which is designed to be significantly shortened in time and to improve a production line.

In general, an injection device is made of a resin supplied through a hopper into a molten state using shear heat and heater heat between an injection screw rotating by a hydraulic motor and a barrel wound by a heater. Refers to a device that injects at a pressure and speed appropriate to the conditions.

The injection screw is the most important part to melt / extrude the resin, and is supplied from the hopper to supply the resin fed from the hopper, the compression part to melt / compress the resin from the supply part to the shear heat and the heater heat, and the conveyance from the compression part. It includes a metering unit for introducing the molten resin that has been supplied to the barrel head side by a predetermined amount.

At this time, the supply portion and the metering portion is a constant bone diameter section, the compression section is composed of a tapered section.

It is known that the sectional shape of each of the intervals of the injection screw and the threaded pushing flight and the trailing flight of the injection screw configured as described above have a great influence on the injection molded product.

However, the conventional injection screw is a resin that is sensitive to the transfer rate and heat due to the long screw feed portion and the short compression portion, for example, flame retardant ABS, flame-retardant PC + ABS synthetic resin, PC, PMMA, hard PVC, etc. generates excessive mechanical heat Carbonization (or sulfidation) of the resin, or yellow streak and silver streak defects are frequently generated.

In addition, the screw thread R in the metering section of the screw is too small, the circulation of the resin in the screw is not smooth, resulting in the stagnation of the resin, this stagnation section will cause carbonized black spots to cause defects in the molded article.

Therefore, by designing the screw used for injection molding of a resin that is sensitive to shear rate and heat according to the characteristics of the resin, an improvement is required to prevent carbonization of the resin and black spot defects caused by the temperature increase due to the shear rate.

The present invention is to solve the problems of the prior art as described above, and to prevent black spots and glitter defects caused by the carbonization phenomenon when melting / extrusion of the resin sensitive to shear rate, and significantly shorten the plasticization time It is an object of the present invention to provide an injection screw of an injection apparatus, which is designed to shorten cycle time and improve productivity.

The specific means of the present invention for achieving the above object is the axially continuous footing flight (104A) and trailing flight (104B) on the outer circumferential surface of the screw shaft (102) rotatably arranged in the barrel (50) A screw for melting / feeding a shear rate sensitive resin such as flame retardant ABS, PC + ABS, and PC, PMMA, hard PVC, etc. introduced from a hopper having a flight 104 and a flight valley 106 having In the injection screw having a diameter of 70mm-150mm, a predetermined portion of the screw shaft 102, the supply unit 106 constant flight diameter, the tapered compression unit 108 and the measurement unit constant flight bone diameter ( 110, but the round (R) values of the pressing holes 108 and the footing flight 104A and the trailing flight 104B of the metering unit 110 are changed, and the length 108 of the compression unit is changed to the metering unit. Length (11 It is designed to be 3.5 times longer than 0).

1 is a schematic diagram of an injection screw 100 according to an embodiment of the present invention.

2 is a front view of the injection screw 100 according to an embodiment of the present invention.

3 to 5 are cross-sectional views of main parts of the injection screw of FIG. 2, taken along line A-A, B-B and C-C of FIG.

6 to 8 is a diagram of the metering capacity according to the back pressure obtained while varying the rotational speed of the injection screw according to the embodiment of the present invention.

9 is a graph showing a temperature change of a resin raw material according to an embodiment of the present invention over time.

<Description of the symbols for the main parts of the drawings>

50: cylinder barrel 100: injection screw

102: screw shaft 104: flight

104A: Footing Flight 104B: Trailing Flight

105: flight goal 106: supply unit

108: compression section 110: metering section

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic view of the injection screw 100 according to an embodiment of the present invention, Figure 2 is a front view of the injection screw 100 according to an embodiment of the present invention, Figures 3 to 5 of the injection screw of Figure 2 Fig. 2 is an enlarged cross-sectional view of the AA, BB, and CC lines of the main parts in each section.

In Figures 1 and 2, the injection screw 100 is largely composed of a flight and the power connection, the flight is a main part of the injection screw 10, the supply unit 106 for supplying the support fee input from the hopper (not shown) And a compression unit 108 for melting / compressing the resin raw material transferred from the supply unit 106 by shear heat and heater heat and a molten resin transferred from the compression unit 108 to the head side of the barrel 50 by a predetermined amount. The metering unit 110 is configured to.

In this case, the supply unit 106 is an interzone section L1 having a constant diameter of the flight goal 105, the compression unit 108 is an interzone section L2 where the flight goal diameter is tapered, and the metering unit 110 is a zone between which the flight goal diameter is constant. When set to the section L3, these interzone sections L1, L2, L3 are closely related to the diameter D of the screw flight 104 and the round R of the footing flight 104A and the trailing flight 104B. Have

Experimental diagrams of the present embodiment for explaining the relationship between the above variables by the metering capability are shown in FIGS. 6 to 8.

6 to 8 show the inter-zone distance L1: L2: L3 for each section of the injection screw 100 having a diameter of 90 mm as 8D: 10D: 1D in the first diagram Q1, and the footing flight 104A. The round (R) value of the trailing flight 104B is set to 10 / 25mm over the entire period, and in the experimental second diagram Q2, the distance between zones is 7D: 11D: 1D, and the footing flight 104A and the trail are made. The round R value of the ring flight 104B is designed to be 6/34 mm in the supply part 106 as shown in FIG. 3 and 10/28 mm in the compression part 108 and the metering part 110, respectively. When the rotational speed of 100) was experimented at 35 RPM, 70 RPM, and 105 RPM in FIGS. 7, 8 and 9, respectively, it is a graph showing the weighing capacity (Kg / Hr) according to the back pressure (%). S) (inter-zone distance = 10: 5: 4, PR = 3, TR = 6) is also shown.

The Geiger PR is the round value of the fussing flight and TR is the round value of the trailing flight.

As shown in FIG. 6, in the case of the experiment first diagram Q1 and the experiment second diagram Q2 at 35 RPM, the weighing capacity was improved by 65% and 60%, respectively, and the experiment first diagram Q1 at 70 RPM as shown in FIG. 7. ) And Experiment 2nd diagram (Q2) were improved to 56% and 68%, respectively, Experiment 1st diagram (Q1) and Experiment 2nd diagram (Q2) improved to 64% and 91%, respectively, at 105 RPM as shown in FIG. It became.

This is because, as the R value of the supply portion of the injection screw 100 increases, the vertical resistance cross-sectional area decreases, the discharge amount is increased under the same conditions, and the plasticization time is shortened. Also, the zone-to-zone distance L2 of the compression section 108 is relative. This resulted in the removal of the resin due to the temperature increase due to the melting of the resin more stable than before.

Preferably, the round value of the trailing flight 104B of the supply part is within the range of the formula (A) below, depending on the outer diameter (D, mm) of the flight 104.

In addition, it is preferable that the round value of the trailing flight 104B of the compression section and the metering section be in the following formula (B) section according to the outer diameter (D, mm) of the flight 104.

In particular, it can be seen that this can be realized by changing the rounding values of the footing flight and the trailing flight that are changed from the supply unit 106 to the compression unit 108 or the metering unit 110. Table 1 below shows the results of plasticization experiments under the same conditions with screws with different R values and interzone distances of 105 mm in diameter.

This shows that, as mentioned above, the screw having a large R value has improved the plasticization capacity by more than 35%. This shortened the cycle time, resulting in a 33% increase in daily output per 850 Ton injection machine. Similar results were obtained in a screw experiment with a diameter of 115 mm.

9 compares the temperature deviation of the conventional injection screw and the head injection screw 100 when the rotation speed of the injection screw 100 is 35 RPM.

That is, the conventional temperature deviation diagram (T) increases the temperature change with time, whereas the T2 diagram of this embodiment shows that the temperature deviation with time is very small as the second experimental diagram under the above conditions. have.

The plot shown with the experimental data shows that:

The round (R) value of the trailing flight 104B of the compression unit 106 and the metering unit may be set within the following equation (B) section according to the outer diameter D of the flight 104.

If it is less than that, the adhesion of the resin raw material is severe, causing temperature rise, and defect generation.

In addition, the R value at the supply part 106, the compression part 108, and the metering part 110 should increase in the pushing flight 104A and decrease in the trailing plate 104B.

It is also required that the inter-zone distance L2 of the compression section 108 is at least 3.5 times the length of the metering section, which means that when the inter-zone distance L2 of the compression section 108 is less than this, the compressed unmelted resin in the compression section (solid bed) is not gradually melted, but rapidly melted, which causes the compressed solid bed to break, resulting in instability of the process, leading to uneven pressure and temperature, resulting in the injection of fine unmelted resin. The appearance of sunspots and yellow lines due to temperature rise in the compression section due to poor molding or excessive compression.

In addition, by reducing the inter-zone distance L3 of the metering unit 110 to 2D or less, it is possible to reduce the residence time in this space, thereby minimizing the rising factor of the resin temperature due to shear heat, thereby reducing the black spots and the yellow streak defects. Qualitative expressions of this can be expressed by the following equations (C) and (D).

L2 ≥ 3.5 * L3 ‥‥‥‥‥‥‥‥ (C)

L3 ≤ 2 * D ‥‥‥‥‥‥‥‥ (D)

In addition, as shown in FIG. 5, the bone height h of the metering unit 110 is set to meet the condition of Equation (E) below, and accordingly, the compression ratio h2 / h1 is within a 2.0-2.8 interval. The occurrence of thermal insulation can also be reduced.

On the other hand, the resin is compressed by providing a plurality of air discharge spiral groove 150 behind the supply portion 106 of the injection screw 100 in Figure 2 in order to reduce the gloss failure due to the air exhaust due to the relatively long length of the compression portion The air and gas generated from the raw material can be quickly discharged, which significantly reduces the product defect rate caused by the air mixing.

As described above, according to the present invention, by changing the distance between zones of each part of the injection screw and the round (R) value of the flight, resin stagnation and temperature rise are suppressed to minimize black streak defects by minimizing adhesion of the support material. It has the advantage of greatly reducing the capacity, and the ability of the resin is increased, which has the effect of greatly increasing the production due to the short cycle time.

Claims (6)

The flight 104 and flight valley 106 having the footing flight 104A and the trailing flight 104B in an axially continuous spiral on the outer circumferential surface of the screw shaft 102 rotatably built up in the cylinder barrel 50. In the injection screw for melting / conveying the resin material sensitive to the shear rate, such as flame-retardant ABS, PC, PMMA, PVC, etc. introduced from the hopper by the shear force, a constant flight diameter of the screw shaft 102 is constant The supply section 106, the compression section 108 tapered flight diameter and the metering section 110 constant flight bone diameter, but the round (R) value of the trailing flight 104B of the supply section 106 is Equation (A) is satisfied, and the round (R) value of the trailing flight 104B of the compression unit 108 and the metering unit 110 satisfies the following equation (B). screw. Where D is the flight outer diameter. The round (R) value of the trailing flight (104B) of the supply section (106) is within the range of the formula (A) with respect to the outer diameter (D) of the flight (104), and the compression section and the metering. An injection screw of an injection apparatus, characterized in that the round (R) value of the negative trailing flight (104B) is within the above formula (B) section with respect to the outer diameter (D) of the flight (104). The injection screw of claim 1, wherein the distance between zones (L2) of the compression unit (108) satisfies the range of the following formula (C) with respect to the distance between zones (L3) of the metering unit. Formula (C): L2≥3.5 * L3 The injection screw according to claim 1, wherein the distance between zones (L3) of the metering unit (110) satisfies the range of the following formula (D) with respect to the outer diameter (D) of the flight (104). Formula (C): L3≤2 * D The height of the flight valley 106 of the metering unit 110 satisfies the range of the following formula (E) with respect to the flight 104 outer diameter (D), and the compression ratio is 2.0-2.8. Injection screw of the injection apparatus, characterized in that within the section. The injection screw of claim 1, further comprising a plurality of spiral grooves (150) for discharging air toward the rear of the supply unit (106) of the injection screw (100).