CN216670731U - Straight manifold clothes hanger type mould - Google Patents

Straight manifold clothes hanger type mould Download PDF

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CN216670731U
CN216670731U CN202123427167.0U CN202123427167U CN216670731U CN 216670731 U CN216670731 U CN 216670731U CN 202123427167 U CN202123427167 U CN 202123427167U CN 216670731 U CN216670731 U CN 216670731U
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麻向军
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South China University of Technology SCUT
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South China University of Technology SCUT
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Abstract

The utility model discloses a straight manifold clothes rack type mold, wherein a flow blocking area of a flow channel is designed into a flow blocking I area and a flow blocking II area with different thicknesses along the length direction of the flow channel, and a manifold is designed into a straight manifold with the section size unchanged along the width direction of the flow channel. The method also relates to a method for deducing a boundary curve of two flow-blocking areas by utilizing a rheology theory based on the condition that the flow rate of a melt outlet is uniform along the width direction of a flow passage through analyzing the flow behavior of the melt in the flow passage under the condition that an inlet area, a relaxation area and a forming area of a coat hanger type mold flow passage are not changed. The runner of the die has the advantages of short length of the flow resistance area and good uniformity of the flow rate of the melt outlet.

Description

Straight manifold clothes hanger type mould
Technical Field
The utility model relates to the technical field of mold design, in particular to a straight manifold clothes hanger type mold.
Background
The coat hanger type die is widely applied to extrusion molding of plastic sheets and cast films. In order to ensure the uniformity of the transverse thickness of the product, the flow channel design of the coat hanger type mould requires that the outlet flow rate of the melt is uniform along the width direction of the flow channel. Based on the principle that the outlet flow rate of the melt in the width direction of the runner is uniform and the residence time of the melt in the manifold and the flow-blocking area is equal, the size and the track of the manifold are calculated aiming at the flow-blocking area with single thickness, and the length of the flow-blocking area of the designed coat-hanger type die is large, so that the die is difficult to be used for extrusion molding of wide sheets and cast films. The improvement of the above method, which extends the residence time of the melt in the manifold to several times the residence time of the melt in the baffle, reduces the length of the baffle region of the runner, but increases the manifold radius, significantly increasing the residence time of the melt in the runner. The radius and the track of the manifold designed by the method are complex, and the difficulty of manufacturing the die is increased.
The runners of the coat hanger type mould used in industrial production mostly adopt the structures of straight manifolds and flow-resistant areas with single thickness. Due to the lack of guidance from design theory, engineering often uses empirical design and improves melt outlet flow rate uniformity by trial and repair. The addition of a flow-blocking rod in a mold is also a common method for improving the flow rate uniformity of a melt outlet, but when the structure design of a runner is poor, even if the flow-blocking rod is adjusted, the flow rate uniformity of the melt outlet cannot meet the molding requirement.
SUMMERY OF THE UTILITY MODEL
The utility model aims to overcome the defects of the prior art and provide a straight manifold clothes rack type mould which is short in choked flow area and good in uniformity of melt outlet flow rate.
The technical scheme of the utility model is as follows: the utility model provides a straight manifold clothes hanger formula mould, straight manifold clothes hanger formula mould's runner includes along the entry district that sets gradually, manifold, choked flow district, lax district and shaping district, the choked flow district includes choked flow I district and the choked flow II district of runner length direction design, and the thickness in choked flow I district and choked flow II district is unequal, the manifold is the straight manifold that cross-sectional dimension is unchangeable along runner width direction.
In the flow-blocking area, the area close to the manifold is a flow-blocking I area, and the area close to the relaxation area is a flow-blocking II area; the thickness of the flow resisting I area and the thickness of the flow resisting II area are not changed along the width direction of the flow passage.
The flow resisting I area is provided with a distance between the position of the symmetrical plane of the flow passage and the tail end of the flow passage and the manifold, and the flow resisting II area is provided with a distance between the position of the symmetrical plane of the flow passage and the tail end of the flow passage and the relaxation area; the cross section of the manifold is circular, and the radius of the manifold is not changed along the width direction of the flow channel.
A rheology design method of a straight manifold clothes rack type mold balance runner is suitable for designing runners of a mold symmetrical along the width direction, and comprises the following steps:
constructing a physical model: assume a. the melt is an incompressible fluid; b. the melt flow is steady laminar flow, and inertia force and volume force are ignored; c. the temperature of the melt is unchanged in the flowing process; d. the melt flows in the manifold only along the axial direction of the manifold, and flows in the flow-resisting I area, the flow-resisting II area, the relaxation area and the molding area only along the extrusion direction, and the flow of the melt in the manifold and the flow in the flow-resisting I area are not interfered with each other; e. neglecting the influence of two side walls at the tail end of the runner on the flow of the melt;
constructing a flow channel geometric model: the mould runner comprises an inlet area, a manifold, a flow blocking area, a relaxation area and a forming area which are sequentially arranged along the flow direction; designing the flow-resisting area as a flow-resisting area I and a flow-resisting area II along the extrusion direction, wherein the thicknesses of the flow-resisting area I and the flow-resisting area II are different; designing the manifold into a straight manifold with constant section size along the width direction of the runner;
and (3) deducing a boundary curve of a choked flow I area and a choked flow II area by using a rheology theory: a coordinate system is constructed. Calculating the pressure of the melt in the manifold along the width direction of the flow channel based on the uniform flow rate of the melt along the width direction of the flow channel, and calculating the pressure drop from the inlet of the flow-resisting I area to the outlet of the flow-resisting II area when the melt flows along the extrusion direction; and obtaining an expression of a boundary curve of the flow-resisting region I and the flow-resisting region II in the coordinate system according to the fact that the melt pressure in the manifold is equal to the melt pressure at the inlet of the flow-resisting region I and the melt pressure at the outlet of the flow-resisting region II is unchanged along the width direction of the flow channel.
Preferably, in the flow channel geometric model, the area close to the manifold is a flow-resisting I area, and the area close to the relaxation area is a flow-resisting II area.
Preferably, in the flow channel geometric model, the thickness of the flow-blocking I area and the flow-blocking II area is constant along the width direction of the flow channel.
Preferably, in the flow channel geometric model, the thickness of the flow-resisting region I is smaller than that of the flow-resisting region II.
Preferably, in the flow channel geometric model, the thickness of the flow-resisting region I is larger than that of the flow-resisting region II.
Preferably, the flow-resisting I area is provided with a distance between the position of the symmetry plane of the flow passage and the tail end of the flow passage and the manifold, and the flow-resisting II area is provided with a distance between the position of the symmetry plane of the flow passage and the tail end of the flow passage and the relaxation area.
Preferably, in the construction of the runner geometric model, the cross section of the manifold is circular, and the radius of the manifold is constant along the width direction of the runner.
Preferably, the thickness and length of the relaxation and shaping regions are constant across the width of the flow channel in constructing the geometric model of the flow channel.
Preferably, at any position in the width direction of the runner, the melt pressure in the manifold is equal to the melt pressure at the inlet of the flow-resisting I area, and the melt pressure at the outlet of the flow-resisting II area is constant in the width direction of the runner.
As a preference, the deduction process of the rheology theory is:
the temperature of the melt is not changed in the flowing process, and the viscosity of the melt is described by adopting a power law model, namely
Figure BDA0003452045480000031
Wherein eta is melt viscosity; k is the consistency coefficient;
Figure BDA0003452045480000032
is the shear rate; n is a power law index;
and taking half of the flow channel for analysis according to the symmetry of the flow channel in the width direction. Neglecting the influence of the inlet area, the cross section of the manifold is circular, the width direction of the flow channel is taken as the x axis, the length direction of the flow channel is taken as the y axis, and the boundary line between the manifold and the flow blocking I area is taken as the z axis to construct a coordinate system, as shown in FIG. 2.
The pressure gradient of the melt flowing along the manifold is
Figure BDA0003452045480000033
Wherein p (z) is the pressure of the melt in the manifold at z; q (z) is the volumetric flow rate of the melt in the manifold at z; r is the manifold radius;
assuming a volume flow rate of 2Q for the melt at the channel entrance0When the melt outlet flow rate is required to be uniform across the width of the flow channel, the volumetric flow rate of the melt in the manifold along the manifold is
Q(z)=Q0(1-zsinθ/W) (3)
In the formula, W is half of the width of the flow channel; theta is half of the expansion angle of the flow resisting region;
equation (3) is substituted for equation (2) and integrated, assuming melt pressure at the manifold end is pEIs provided with
Figure BDA0003452045480000034
According to said coordinate system, have
x=z sinθ (5)
p(x)=p(z) (6)
Wherein p (x) is the pressure of the melt in the manifold at x;
formulae (5) to (6) are substituted for formula (4) with
Figure BDA0003452045480000041
Because the thickness and the length of the relaxation area and the forming area are not changed along the width direction of the runner, when the flow rate of the melt outlet is required to be uniform along the width direction of the runner, the melt pressure at the outlet of the flow-resisting area II is not changed along the width direction of the runner. The length of the flow choking region on the symmetrical plane of the flow channel is L, and the melt pressure at the outlet of the flow choking II region (namely y is L) is pLAt any position in the width direction of the flow pathx, the pressure drop between the inlet of the flow-resistant zone I and the outlet of the flow-resistant zone II is
Figure BDA0003452045480000042
In the formula, h1And h2The thickness of the flow-resisting region I and the flow-resisting region II respectively; y is a boundary curve of the choked flow I area and the choked flow II area and is a function of the coordinate x;
at the end of the flow path in the width direction, i.e., x is W, y is yE,p(x)=pEIs substituted by formula (8)
Figure BDA0003452045480000043
From formulae (7) to (9)
Figure BDA0003452045480000044
Y in the formula (10) is an expression of a boundary curve of the flow-resisting region I and the flow-resisting region II in the coordinate system.
Preferably, the pressure drop of the melt flowing from the manifold inlet to the manifold and the choke zone along either path is equal and can be represented by the sum of the pressure drop of the melt flowing from the manifold inlet to the end of the manifold and the pressure drop of the melt flowing through the end of the choke zone at the end of the runner, i.e., the pressure drop of the melt flowing from the manifold inlet to the end of the manifold and the pressure drop of the melt flowing through the end of the choke zone at the end of the runner are equal
Figure BDA0003452045480000045
Preferably, numerical simulation software is adopted to perform numerical simulation on the flow field of the melt in the flow channel, and the ratio of the volume flow rate of a unit width at a certain position in the width direction of the flow channel at the melt outlet to the volume flow rate of an average unit width is defined as the dimensionless flow rate of the melt outlet, so as to reflect the uniformity of the flow rate of the melt outlet and further verify the reliability of the boundary curve.
The principle of the utility model is as follows: in the runner of the clothes rack type mould, the melt enters the manifold from the inlet area and flows along the manifold, and meanwhile, a part of the melt enters the flow resistance area and flows into the relaxation area and the forming area along the extrusion direction. The melt pressure in the manifold decreases non-linearly in the direction of flow, i.e., the melt pressure at the entrance to the choked flow region decreases non-linearly in the direction of the width of the flow path. Under the condition of not changing the shapes of the cross sections of the inlet area, the relaxation area and the forming area, the flow-resisting area is designed into two areas (namely a flow-resisting area I and a flow-resisting area II) with different thicknesses along the length direction (extrusion direction) of the runner, the manifold is designed into a straight manifold with the cross section dimension unchanged along the width direction of the runner, and the pressure of the melt at the outlet of the flow-resisting area II is unchanged along the width direction of the runner through the design of a boundary curve of the flow-resisting area I and the flow-resisting area II, or the pressure drop of the melt flowing through the manifold and the flow-resisting area along any path from the inlet of the manifold is equal, so that the aim of enabling the flow rate of the melt to be uniform along the width direction of the runner is fulfilled.
Compared with the prior art, the utility model has the following beneficial effects:
the utility model designs a flow channel flow choking area of a clothes rack type mould into two areas (a flow choking I area and a flow choking II area) with different thicknesses, designs a manifold into a straight manifold with the section size unchanged along the width direction of the flow channel, analyzes the flow of a melt in the flow channel of the clothes rack type mould, theoretically designs the structure and the size of the flow channel according to the rheology theory on the premise that the flow rate of a melt outlet is uniform along the width direction of the flow channel, and deduces a boundary curve of the flow choking I area and the flow choking II area.
The numerical simulation is carried out on the flow behavior of the melt in the coat hanger type mould runner designed by the design method of the boundary curve theory of the choked flow I area and the choked flow II area, the reliability of the boundary curve is verified, and the method can be used for designing the guide straight manifold coat hanger type mould runner.
Compared with the existing design method of the straight manifold clothes rack type mold runner, the design method provided by the utility model can effectively reduce the length of the flow choking area and further the length of the runner under the condition of meeting the requirement of uniform volume flow rate of a melt outlet.
Compared with the design method of the existing straight manifold clothes rack type mold runner, the design method can be used for designing the radius of the manifold, the length and the expansion angle of the flow resisting area, the thickness of the flow resisting area I and the flow resisting area II and the boundary shape curve of the flow resisting area II according to the molding requirement.
Drawings
Fig. 1 is a schematic view of a runner structure of a straight manifold clothes rack type mold designed in the present patent.
FIG. 2 is a schematic diagram of a rheological design model of a straight manifold coat hanger type mold runner in the embodiment.
Fig. 3 is a pressure contour line of the melt in the runner obtained by simulation calculation when n is 0.4 in the example.
Fig. 4 is a pressure contour line of the melt in the runner obtained by simulation calculation when n is 0.6 in the example.
Fig. 5 shows the dimensionless flow rate per unit width along the width direction of one side of the flow channel calculated by the simulation when n is 0.4 in the example.
Fig. 6 shows the dimensionless flow rate per unit width in the width direction of one side of the flow channel calculated by the simulation in the example where n is 0.6.
In the figure, 1 is an inlet zone, 2 is a manifold, 31 is a flow-resisting zone I, 32 is a flow-resisting zone II, 4 is a relaxation zone, and 5 is a molding zone.
Detailed Description
The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
The rheological design method of the straight manifold clothes rack type mold balance runner is suitable for designing the runner of the mold symmetrical along the width direction, and comprises the following steps:
s1, constructing a physical model: assume a. the melt is an incompressible fluid; b. the melt flow is steady laminar flow, and inertia force and volume force are ignored; c. the temperature of the melt is unchanged in the flowing process; d. the melt flows in the manifold only along the axial direction of the manifold, and flows in the flow-resisting I area, the flow-resisting II area, the relaxation area and the molding area only along the extrusion direction, and the flow of the melt in the manifold and the flow in the flow-resisting I area are not interfered with each other; e. neglecting the influence of the two side walls at the end of the runner on the melt flow.
S2, constructing a flow channel geometric model: as shown in fig. 1, the mold runner includes an inlet region 1, a manifold 2, a flow blocking region, a relaxation region 4 and a molding region 5, which are arranged in sequence along the melt flow direction; the flow blocking region is designed into a flow blocking I region 31 and a flow blocking II region 32 with different thicknesses along the length direction of the flow channel, the region close to the manifold is the flow blocking I region, the region close to the relaxation region is the flow blocking II region, and the thicknesses of the flow blocking I region and the flow blocking II region are not changed along the width direction of the flow channel; a gap is formed between the flow-resisting I area and the manifold at the position of the symmetrical plane of the flow passage and between the tail end of the flow passage and the manifold, and a gap is formed between the flow-resisting II area and the relaxation area at the position of the symmetrical plane of the flow passage and between the tail end of the flow passage and the manifold; the cross section of the manifold is designed to be circular, and the radius of the manifold is not changed along the width direction of the runner; the thickness and length of the relax and form regions are constant along the width of the flow channel.
S3, deducing a boundary curve of the choked flow I area and the choked flow II area by using a rheology theory: constructing a coordinate system, as shown in fig. 2, calculating the melt pressure in the manifold in the width direction of the flow channel based on the uniform outlet flow rate of the melt in the width direction of the flow channel, and calculating the pressure drop from the inlet of the flow-resisting region I to the outlet of the flow-resisting region II when the melt flows in the extrusion direction; and obtaining an expression of a boundary curve of the flow-resisting region I and the flow-resisting region II in the coordinate system according to the condition that the melt pressure at the inlet of the flow-resisting region I is equal to the melt pressure in the manifold and the melt pressure at the outlet of the flow-resisting region II is unchanged along the width direction of the flow channel.
The deduction process of the rheology theory is as follows:
and according to the symmetry of the flow channel in the width direction, taking half of the flow channel for analysis. Neglecting the influence of the inlet area, the cross section of the manifold is circular and has a constant size along the width direction of the flow channel, and other shapes can be converted by a shape factor. A coordinate system is established by taking the width direction of the flow channel as the x axis, the length direction of the flow channel as the y axis, and the boundary line between the manifold and the flow-resisting region I as the z axis, as shown in fig. 2.
The shear viscosity of the melt is described using a power law model, i.e.
Figure BDA0003452045480000071
Wherein eta is melt viscosity; k is the consistency coefficient;
Figure BDA0003452045480000072
is the shear rate; n is a power law exponent.
The pressure gradient of the melt flowing along the manifold is
Figure BDA0003452045480000073
Wherein p (z) is the pressure of the melt in the manifold at z; q (z) is the volumetric flow rate of the melt in the manifold at z; r is the manifold radius.
Assuming a volume flow rate of 2Q for the melt at the channel entrance0When the melt outlet flow rate is uniform across the width of the channel, the volumetric flow rate of the melt in the manifold along the manifold is
Q(z)=Q0(1-zsinθ/W) (3)
In the formula, W is half of the width of the flow channel; theta is half of the expansion angle of the flow-resisting region.
Equation (3) is substituted for equation (2) and integrated, assuming melt pressure at the manifold end is pEIs provided with
Figure BDA0003452045480000074
According to said coordinate system, have
x=z sinθ (5)
p(x)=p(z) (6)
Where p (x) is the pressure of the melt in the manifold at x.
Formulae (5) to (6) are substituted for formula (4) with
Figure BDA0003452045480000081
Because the thickness and the length of the relaxation area and the forming area are not changed along the width direction of the runner, when the flow rate of the fusant outlet is required to be uniform along the width direction of the runner, the pressure of the fusant at the outlet of the flow resisting area II is not changed along the width direction of the runner. The length of the flow choking region on the symmetrical plane of the flow channel is L, and the melt pressure at the outlet of the flow choking II region (namely y is L) is pLWhen the melt flows in the extrusion direction in the flow-blocking zone at any position x in the width direction of the flow channel, the pressure drop between the inlet of the flow-blocking zone I and the outlet of the flow-blocking zone II is
Figure BDA0003452045480000082
In the formula, h1And h2The thickness of the flow-resisting region I and the flow-resisting region II respectively; y is the boundary curve of the choked flow I area and the choked flow II area and is a function of the coordinate x.
At the end of the flow path in the width direction, i.e., x is W, y is yE,p(x)=pEIs substituted by formula (8)
Figure BDA0003452045480000083
From the formulae (7) to (9)
Figure BDA0003452045480000084
Y in the formula (10) is an expression of the boundary curve of the choked flow I area and the choked flow I area in the coordinate system.
From the formula (10), it can be seen that the boundary curves of the flow-impeding I and flow-impeding II zones are dependent on the channel width, the manifold radius, the thickness of the flow-impeding I and flow-impeding II zones, the length and the divergence angle of the flow-impeding zones, and the power law index n of the melt, and are independent of the consistency and yield of the melt.
When x is 0, the length of the choked flow I region obtained by the formula (10) at the symmetrical position in the width direction of the flow channel is
Figure BDA0003452045480000091
When the flow channel is designed, the sizes of all parts of the flow channel need to be comprehensively considered, and a proper distance is reserved between the flow-resisting I area and the flow-resisting II area in the length direction of the flow channel at any position in the width direction of the flow channel so as to facilitate the manufacture of a mold.
The pressure drop of the melt flowing from the manifold inlet along either path through the manifold and the choke zone is equal and can be expressed as
Figure BDA0003452045480000092
The first term at the right end of the formula (12) is the pressure drop of the melt flowing from the inlet of the manifold to the tail end of the manifold, and the second term is the pressure drop of the melt flowing through the flow-resisting I area and the flow-resisting II area at the tail end of the runner. When the flow channel is designed, the extrusion pressure can be adjusted through the design of the radius of the manifold, the thickness of the flow-resisting region I and the flow-resisting region II, the length of the flow-resisting region and the expansion angle.
S4, verification: in order to verify the reliability of boundary curves of the flow-resisting zone I and the flow-resisting zone II deduced by the method, two melts with different power law indexes are selected for flow channel design, and numerical simulation software is adopted to calculate the flow field of the melts in the flow channel. And defining the ratio of the volume flow rate of a unit width at a certain position in the width direction of the flow channel at the melt outlet to the volume flow rate of the average unit width as the dimensionless flow rate of the melt outlet, so as to reflect the uniformity of the flow rate of the melt outlet and verify the reliability of the boundary curve of the flow-resisting I area and the flow-resisting II area derived in the foregoing.
The sheet width (2W) was 2000mm, the thickness and length of the relaxation zone were 4mm and 40mm, respectively, and the thickness and length of the molding zone were 2mm and 20mm, respectively. Describing the rheological property of the melt by adopting a power law model, and respectively taking n as 0.4 and K as 8000 Pa.s-0.6And n is 0.6, K is 8000 Pa.s-0.4. The radius of the manifold is 15mm, the divergence angle (2 theta) of the flow-resistant area is 177 degrees, the length of the flow channel at the symmetrical plane of the width is 40mm, and y isETaking 34mm, taking 2.5mm as the thickness of the flow-resisting region II, taking 1.2mm and 1.6mm as the thickness of the flow-resisting region I when n is 0.4 and 0.6 respectively, and calculating according to the formula (10)The boundary curve to the choked flow I zone and the choked flow II zone. And performing geometric modeling on the flow channel by adopting three-dimensional design software, and calculating half of the flow channel according to the symmetry of the flow channel in the width direction.
Extrusion yield (2Q)0) Take 80000mm3The melt pressure contours in the flow channel obtained by simulation calculation at/s (i.e., an extrusion speed of 40mm/s) and n of 0.4 and 0.6 are shown in FIGS. 3 and 4, respectively. It can be seen that the pressure contour of the melt as it leaves the choked flow region is parallel to the channel outlet, thereby ensuring uniformity of the melt outlet flow rate across the width of the channel. When n is 0.4 and 0.6, the pressure drop of the melt flowing from the manifold inlet along either path through the manifold and the choke zone is 4.91MPa and 8.28MPa, respectively, in accordance with the calculation of equation (12).
Fig. 5 and 6 show the dimensionless flow rates of the melt outlet at one side of the runner across its width for n values of 0.4 and 0.6, respectively, from the numerical simulations. The melt outlet dimensionless flow rate increases across the width of the channel to a maximum at about 20mm from the end of the channel, increasing from 0.995 to 1.005 for n of 0.4 and from 0.997 to 1.003 for n of 0.6; and then, the flow rate begins to decline, and the flow rate of the melt dimensionless outlet is less than 1 only within the range of about 10mm at the tail end of the runner, because the influence of the side wall of the runner on the melt flow is neglected in theoretical derivation, and when the melt flow field is numerically simulated, a slip-free boundary is formed between the melt and the side wall, which is consistent with actual production.
As shown in fig. 1, a flow channel of the straight manifold clothes hanger type mold of the present embodiment includes an inlet region 1, a manifold 2, a flow blocking region, a relaxation region 4, and a molding region 5, which are sequentially arranged along a flow direction, the flow blocking region includes a flow blocking I region 31 and a flow blocking II region 32, which are designed along a length direction of the flow channel, thicknesses of the flow blocking I region and the flow blocking II region are different, and the manifold is a straight manifold with a cross-sectional dimension that is not changed along a width direction of the flow channel. In the flow-resisting area, the area close to the manifold is a flow-resisting area I, and the area close to the relaxation area is a flow-resisting area II; the thickness of the flow-resisting I area and the thickness of the flow-resisting II area are not changed along the width direction of the flow channel. A gap is formed between the flow-resisting I area and the manifold at the position of the symmetrical plane of the flow passage and between the tail end of the flow passage and the manifold, and a gap is formed between the flow-resisting II area and the relaxation area at the position of the symmetrical plane of the flow passage and between the tail end of the flow passage and the manifold; the cross section of the manifold is circular, and the radius of the manifold is not changed along the width direction of the flow channel.
In addition to the above-mentioned manner, for manifolds with other cross-sectional shapes, the melt pressure in the manifold can be converted by the shape factor, so as to obtain the boundary curve of the flow-resisting region i and the flow-resisting region ii corresponding to the manifolds with different cross-sectional shapes. These variations are all within the scope of the present invention.
In addition to the above-mentioned manner of the embodiment, the length of the flow-resisting region I and the flow-resisting region II at any position in the flow channel width direction is substantially determined for the boundary curve of the flow-resisting region I and the flow-resisting region II calculated by the above-mentioned design method, and therefore, the outlet volume flow rate can be ensured to be uniform by changing or decomposing the positions of the flow-resisting region I and the flow-resisting region II in the extrusion direction. These variations are all within the scope of the present invention.
In addition to the above-mentioned manner, the use of a chamfer or rounded transition between the flow-impeding I region and the flow-impeding II region does not affect the boundary curve between the flow-impeding I region and the flow-impeding II region. These variations are all within the scope of the present invention.
As mentioned above, the present invention can be better realized, and the above embodiments are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention; all equivalent changes and modifications made according to the present disclosure are intended to be covered by the scope of the claims of the present invention.

Claims (3)

1. The straight manifold clothes rack type mold is characterized in that a runner of the straight manifold clothes rack type mold comprises an inlet area, a manifold, a flow blocking area, a relaxation area and a forming area which are sequentially arranged in the flow direction, wherein the flow blocking area comprises a flow blocking I area and a flow blocking II area which are designed in the length direction of the runner, the thicknesses of the flow blocking I area and the flow blocking II area are different, and the cross section of the manifold is a straight manifold with the size unchanged in the width direction of the runner.
2. The straight manifold clothes hanger mold according to claim 1, wherein in the flow blocking area, the area close to the manifold is a flow blocking I area, and the area close to the relaxation area is a flow blocking II area; the thickness of the flow resisting I area and the thickness of the flow resisting II area are not changed along the width direction of the flow passage.
3. The straight manifold clothes rack type mold according to claim 1, wherein the flow-resisting region I is provided with a space between the position of the symmetry plane of the flow passage and the tail end of the flow passage and the manifold, and the flow-resisting region II is provided with a space between the position of the symmetry plane of the flow passage and the tail end of the flow passage and the relaxation region; the cross section of the manifold is circular, and the radius of the manifold is not changed along the width direction of the flow channel.
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