TWI474916B - Method for manufacturing flow channel of die - Google Patents

Description

Die flow path manufacturing method

The invention relates to a method for manufacturing a die flow channel, in particular to a die flow channel which is suitable for a hollow elliptical die and which can make the flow rate and density of the flow uniform and the thickness of the flow channel are thick. method.

The conventional hollow circular die can be divided into a continuous hollow circular die and an accumulator hollow head. The plastic material is melted by a screw and enters the die inlet, and can be divided into a center feed. And side feed two types, the central feed flow channel is symmetrical, the shape of the embryo is good; the side feed is asymmetrical at the front end, but can be rectified by the back flow channel; therefore, basically Whether the central feed or the side feed, the rear flow passage is usually symmetrical cylindrical, which can achieve good flow outlet uniformity and can easily control the axial thickness of the parison at the rear end. It is also the thickness of the runner so that the thickness of the hollow finished product is relatively uniform.

However, in products with large differences in large aspect ratios, such as bumpers, medical boards, pallets, etc., the cylindrical embryo has different elongation of the long and short axes, resulting in uneven thickness of the product after inflation; therefore, generally based on product appearance The hollow elliptical die designed by the hollow elliptical die is a hollow elliptical die with long and short axes, which has the disadvantage of asymmetrical flow channel exit, which results in uneven flow velocity and uneven density of the flow of the long and short shafts. Controlling the thickness leads to a reduction in the yield of the finished product.

In view of the above problems of the prior art, the object of the present invention is to provide a method for manufacturing a die flow path, which solves the problem that the conventional hollow elliptical die has uneven flow velocity, uneven density, and cannot be controlled by axial thickness. problem.

According to the object of the present invention, a method for manufacturing a die flow path is proposed, which is suitable for a hollow elliptical die, the inside of the die includes a flow path, and the die pushes the flow material through the flow path to form a parison, and the die flow path The manufacturing method comprises the steps of: providing a shaft segment parallel to the flow direction of the die, and having a first elliptical cross section and a second elliptical cross section at each end of the shaft segment; providing a first semi-long axis length of the first elliptical cross section and the first a semi-minor axis length, and a second half major axis length and a second half minor axis length corresponding to the first semi-major axis length and the first semi-minor axis length, respectively; using the first semi-major axis length, The half short axis length, the second half long axis length, and the second half minor axis length obtain a flow path length between each angle of the first elliptical cross section to each angle corresponding to the second elliptical cross section, and the flow path length satisfies the following conditions : Where L is the length of the flow channel, a is the length of the first half of the major axis, b is the length of the first semi-minor axis, c is the length of the second half of the major axis, d is the length of the second half of the minor axis, θ is the angle, z is The length of the shaft segment; the length of the flow channel corresponding to each angle is respectively corresponding to the thickness of the flow channel; the flow path corresponding to the length of each flow channel, the thickness of each flow channel and the shaft segment is prepared; wherein the length of the first half long axis and the first half The minor axis length, the second half major axis length, the second half minor axis length, and the length of the shaft segment satisfy the following conditions:

Preferably, the first elliptical cross section may be an elliptical shape (a≠b) or a circular shape (a=b), and the second elliptical cross section may be an elliptical shape or a circular shape.

Preferably, when the first elliptical section or the second elliptical section has a circular shape, the first semi-major axis length and the first semi-minor axis length may be equal, or the second semi-major axis length and the second semi-minor axis length may be equal.

Preferably, the thickness of the flow channel can satisfy the following conditions: Where H is the thickness of the runner, q is the flow per unit width, s is the reciprocal of the power index, m is the power consistency of the power, L is the length of the runner, and p is the pressure.

Preferably, the flow rate per unit width of the flow material can satisfy the following conditions: Where q is the unit width flow, Q is the total flow, W is the width, H is the runner thickness, n is the power index, p is the pressure, m is the power consistency, L is the runner length, s is the power The reciprocal of the secondary fluid index.

Preferably, the total flow rate of the flow material flowing in the flow channel can satisfy the following conditions: Where Q is the total flow, W is the width, H is the thickness of the runner, n is the power index, p is the pressure, m is the power consistency, L is the length of the runner, and s is the reciprocal of the power index.

Preferably, the viscosity of the flow material can satisfy the following conditions: Where η is the viscosity, For shear rate, m is the power consistency of the power, and n is the power index of the power.

According to the manufacturing method of the die flow path of the present invention, the long and short axes of the elliptical cross section conforming to the natural balance can be used, and the conditional expression can be substituted to calculate the flow path length of each angle, and then the flow path length is substituted. Another conditional expression is to obtain the thickness of the flow channel. When the lengths of the obtained flow channels are approximately equal, the thickness of the flow channel is also equal and thick, so that it is not necessary to repeatedly adjust the design flow path and thickness during the manufacturing process of the die to save. The purpose of time and material cost is also to achieve the balance of outlet flow and uniform density, thereby improving the yield of finished products.

1‧‧‧die

2‧‧‧ flow path

3‧‧‧ mandrel

C1‧‧‧ first elliptical section

C2‧‧‧Second elliptical section

L‧‧‧Flow path length

S11 to S15‧‧‧ steps

Z‧‧‧ shaft length

θ _C1 , θ _C2 ‧‧‧ angle

Fig. 1 is a flow chart showing a method of manufacturing a die flow path of the present invention.

Figure 2 is a schematic view of the die flow path of the present invention.

Figure 3 is a schematic view of the first elliptical section and the second elliptical section of the present invention.

Figure 4 is a schematic view of the length of the flow path of the present invention.

Please refer to FIG. 1 , which is a flow chart of a method for manufacturing a die flow path of the present invention. As shown in the figure, the method for manufacturing a die flow path of the present invention is applicable to a hollow elliptical die, the inside of the die includes a flow path, and the die pushes the flow material through the flow path to form a preform, and the die flow path The manufacturing method consists of the following steps:

In step S11, a shaft segment of a parallel die flow direction is provided, and both ends of the shaft segment have a vertical first elliptical cross section and a second elliptical cross section. Wherein, the flow direction of the die refers to the direction in which the flow material flows in the flow path of the die; the axial segment refers to the axial segment of the parallel flow direction of the target object to be extruded.

In step S12, a first semi-major axis length and a first semi-minor axis length of the first elliptical section are provided, and a second half of the second elliptical section corresponding to the first semi-major axis length and the first semi-minor axis length respectively Long shaft length and second half short shaft length. Where the first ellipse The surface C1 may be an elliptical shape or a circular shape, and the second elliptical cross section C2 may be an elliptical shape or a circular shape; when the cross section is a circular shape, the major axis and the minor axis have the same length, that is, the semi-major axis length and the semi-minor axis length. The length of the radius of the circle.

In step S13, the angles of the first elliptical section are obtained to the angles corresponding to the second elliptical section by using the first semi-major axis length, the first semi-minor axis length, the second semi-major axis length, and the second semi-minor axis length. The length of the flow path between the two, and the length of the flow path meets the following conditions: Where L is the length of the flow channel, a is the length of the first half of the major axis, b is the length of the first semi-minor axis, c is the length of the second half of the major axis, d is the length of the second half of the minor axis, θ is the angle, z is Length of the shaft segment.

In step S14, the channel thickness is respectively obtained by using the channel lengths of the respective angles.

In step S15, flow paths corresponding to the lengths of the respective channels, the thicknesses of the respective channels, and the shaft segments are produced.

Please refer to Figures 2 to 4 together. Figure 2 is a schematic view of the die flow path of the present invention; Figure 3 is a schematic view of the first elliptical section and the second elliptical section of the present invention; Schematic diagram of the length of the flow path of the present invention. As shown in the figure, the die 1 extrudes the flow material in the flow channel 2 to form a parison, and since the mold has a mandrel 3, the flow can be separated by the mandrel 3 to form a post-extrusion. The type of embryo is hollow, which facilitates the subsequent inflation molding process; however, since the die 1 is a hollow elliptical die, problems such as uneven flow rate and uneven density may occur due to the asymmetry of the discharge outlet; therefore, the present invention is Make each section correspond to the same length L of the flow channel between the same angles to achieve the flow out The flow rate of the mouth is the same; the following is a detailed description of the manufacturing method of the die flow path of the present invention.

First, find the axial section of the parallel flow direction of the target object to be extruded, and find the first elliptical section C1 and the second elliptical section C2 perpendicular to the shaft section and respectively located at both ends of the shaft section, the first elliptical section C1 includes a first half major axis length a, a first semi-minor axis length b, and a second elliptical cross section including a second half major axis length c and a second half minor axis length d.

The first elliptical section C1 and the second elliptical section C2 may meet the following conditions:

Moreover, the first half major axis length a, the first semi-minor axis length b, the second half major axis length c, the second half minor axis length d, and the shaft segment length z can satisfy the following conditions:

Further, the axial length z is the distance C2 from a first elliptical cross-section C1 and the second ellipse, the angle [theta] of the first elliptical cross C1 _{C1 C1} to a corresponding angle [theta] and the elliptical cross section of the same angle [theta] of the second C2 _C2 The length L of the runner can meet the following conditions:

Therefore, the length of the flow channel is derived

Please refer to Table 1 for further At the time of the flow path length of each axis, a comparison table.

In accordance with the above, when The flow path length L of each angle from the first elliptical section C1 to the second elliptical section C2 is the same.

On the other hand, according to the viscosity η of the flowing material, the flow rate q per unit width, the pressure p and the length L of the flow path, the thickness H of the flow path can be calculated, and the thickness H of the flow path can satisfy the following conditions:

Where H is the thickness of the runner, q is the flow per unit width, s is the reciprocal of the power index, m is the power consistency of the power, L is the length of the runner, and p is the pressure.

In detail, the unit width flow can meet the following conditions:

Where q is the unit width flow, Q is the total flow, W is the width, H is the runner thickness, n is the power index, p is the pressure, m is the power consistency, L is the runner length, s is the power The reciprocal of the secondary fluid index.

The total flow rate Q can satisfy the following conditions:

Where Q is the total flow, W is the width, H is the thickness of the runner, n is the power index, p is the pressure, m is the power consistency, L is the length of the runner, and s is the reciprocal of the power index.

The viscosity of the flow material can satisfy the following conditions, wherein the viscosity of the flow material is expressed by a power law fluid equation, however, the range of the flow material is not limited thereto:

Where η is the viscosity, For shear rate, m is the power consistency of the power, and n is the power index of the power.

Please refer to Table 2 for a comparison table corresponding to the channel thickness H of each channel length L in Table 1, where z=2, W=1, Q=1, s=1/n=1, m= 1, △ p = 1.

In accordance with the above, when When the flow path lengths of the respective angles from the first elliptical section C1 to the second elliptical section C2 are the same, the corresponding channel thickness H is also the same.

In general, in order to achieve consistent flow velocity at the exit of an asymmetric hollow die, conventional practices are The error design method repeatedly adjusts the thickness of the flow channel until the flow rate is consistent; however, this method is very time consuming, and the material wear cost is correspondingly increased; in contrast, the first elliptical section C1 of the present invention has the same correspondence with the second elliptical section C2. When the length L of each flow path between the angles is the same or less than 5-10% error, the thickness H of the flow channel can be set to a certain value, so that the flow velocity and density of the flow are uniform, and the thickness of the parison is uniform, and it is not necessary. As is conventional, the error is repeatedly adjusted to save manufacturing time and material cost.

In more detail, the relative relationship between the length L of the flow path and the angle θ can be derived according to the following conditional formula:

It can be seen from the conditional expression (11) that when (ac) ² = (bd) ² , the flow path length L is independent of the angle θ, and at this time, the die can be of a uniform design.

On the other hand, if (ac) ² ≠(bd) ^2, it means that the flow path length L is related to the angle θ, and the flow path thickness H will vary with the angle θ.

Further, if the channel thickness H varies with the angle θ, and the first half major axis length a, the first semi-minor axis length b, the second half major axis length c, and the second half minor axis length d satisfy the equation (4) ), the variation of the thickness of the runner thickness H will be within 10%; accordingly, when the die adopts a uniform design, the flow difference caused by it will be controlled within 10%.

For the above, please refer to Table 3 and Table 4, which are respectively And z=2, W=1, Q=1, m=1, Δp=1, corresponding to the comparison table of each channel length L and channel thickness H of each angle, wherein s=1.0, 2.0 respectively , 3.3 represents the rheological parameters of different materials.

As can be seen from Table 3 and Table 4, when When the die corresponds to various materials, the flow path length L or the flow path thickness H at each angle is the same, that is, when When the die corresponds to the flow path length L of each angle or the flow path thickness H is independent of the material of the flow material.

On the contrary, please refer to Table 5 and Table 6, which are respectively And z=2, W=1, Q=1, m=1, Δp=1, corresponding to the comparison table of each channel length L and channel thickness H of each angle, wherein s=1.0, 2.0 respectively , 3.3 represents the rheological parameters of different materials.

As can be seen from Table 5 and Table 6, when When the die corresponds to various materials, the flow path length L of each angle is different, and the thickness H of the flow channel corresponding to various materials at various angles is also different; and if different materials are changed (for example, materials with s=3) ), it may cause the gap thickness H of the corresponding angles to be too large, so that the flow balance cannot be achieved.

The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

S11 to S15‧‧‧ steps

Claims (7)

The invention discloses a method for manufacturing a die flow channel, which is suitable for a die having a hollow elliptical shape, and the die body comprises a first-class ball, and the die head extrudes a first-class material through the flow channel to form a type of embryo, and the die flow path The manufacturing method comprises the steps of: providing one of the axial segments parallel to the flow direction of the die, and having a first elliptical cross section and a second elliptical cross section at each end of the axial segment; providing the first half of the first elliptical cross section a length of the major axis and a length of the first semi-minor axis, and a length of the second semi-major axis corresponding to the length of the first semi-major axis and the length of the first semi-minor axis, respectively, and a second half-length a length of the shaft, using the first semi-major axis length, the first semi-minor axis length, the second semi-major axis length, and the second semi-minor axis length to obtain respective angles of the first elliptical cross section to the second elliptical cross section Corresponding to one of the flow path lengths between the angles, and the flow path length meets the following conditions: Where L is the length of the flow channel, a is the length of the first semi-major axis, b is the length of the first semi-minor axis, c is the length of the second semi-major axis, and d is the second half The length of the minor axis, θ is the angle, and the z is the length of the shaft; the length of the runner is respectively corresponding to the thickness of the runner; and the length of each runner, the thickness of the runner, and the axis are The flow path of the segment; wherein the first semi-major axis length, the first semi-minor axis length, the second semi-major axis length, the second semi-minor axis length, and the length of the shaft segment satisfy the following conditions: The method of manufacturing a die flow path according to claim 1, wherein the first elliptical cross section is an elliptical shape or a circular shape, and the second elliptical cross section is an elliptical shape or a circular shape. The method of manufacturing a die flow path according to claim 2, wherein the first semi-long axis length and the first half length are short when the first elliptical cross section or the second elliptical cross section is a circular shape The lengths of the shafts are equal, or the length of the second half major axis and the length of the second half minor axis are equal. The method for manufacturing a die flow path according to claim 3, wherein the thickness of the flow channel satisfies the following conditions: Where H is the thickness of the flow channel, q is a unit width flow, s is the reciprocal of the power index, m is the power consistency, L is the length of the channel, and p is the pressure. The method for manufacturing a die flow channel according to claim 4, wherein the flow rate per unit width of the flow material satisfies the following conditions: Where q is the unit width flow, Q is a total flow, W is the width, H is the thickness of the channel, n is the power index, p is the pressure, and m is the power consistency. , L is the length of the channel, and s is the reciprocal of the power index. The method of manufacturing a die flow path according to claim 5, wherein the total flow rate of the flow material flowing in the flow path satisfies the following conditions: Where Q is the total flow, W is the width, H is the thickness of the channel, n is the power index, p is the pressure, m is the power consistency, and L is the length of the channel. , s is the reciprocal of the power index. The method for manufacturing a die flow path according to claim 6, wherein the viscosity of one of the flow materials satisfies the following conditions: Where η is the viscosity, The shear rate is m, the m is the power consistency, and the n is the power index.