WO2022073326A1

WO2022073326A1 - Plastic weld line evaluation method and evaluation kit

Info

Publication number: WO2022073326A1
Application number: PCT/CN2021/082673
Authority: WO
Inventors: 欧相麟; 严卫卫; 俞飞; 张云青; 杨良波; 黄佳佳; 周琴平; 杨明; 孙长周; 丁正亚
Original assignee: 金发科技股份有限公司
Priority date: 2020-10-09
Filing date: 2021-03-24
Publication date: 2022-04-14
Also published as: CN112140490A

Abstract

Provided in the present invention are a plastic weld line evaluation method and a corresponding evaluation kit. The evaluation kit comprises an insert and an injection mold. Evaluation structures with different weld lines are obtained by means of changing inserts, which have different shapes, in the injection mold and thus changing the confluence angle of molten resin, and then the appearance and mechanical properties of the weld lines are tested based on the evaluation structures, so that the quality of the weld lines generated at different confluence angles of the molten resin during injection molding can be effectively and accurately evaluated. In addition, the insert can be fixed in the injection mold by means of bonding, magnetic attraction, embedding, etc., so that the inserts which have different shapes can be conveniently replaced without changing the original structure of the injection mold, and the usage is convenient and fast.

Description

A kind of plastic welding line evaluation method and evaluation kit

technical field

The invention belongs to the technical field of injection molding, and particularly relates to an evaluation kit and an evaluation method for plastic welding lines.

Background technique

During the injection molding production of plastic products, the molten resin flows in at least two directions in the mold. When two or more strands of molten resin meet, the molten resin close to the mold cavity will rapidly cool, resulting in two or more strands of molten resin. If the joints of the strands of molten resin are not completely combined, a weld line will be formed in the plastic product, and the weld line will affect the appearance and mechanical properties of the plastic product, such as: streaks and nicks may appear in the weld line area; There is trapped air, which will hinder the entanglement effect between polymer molecules, causing the molecular chains to separate from each other, so that the mechanical strength of the weld line area will be lower than that of the non-weld line area. Most injection molding products have weld lines, and it is difficult to completely eliminate the weld lines. We can only minimize the impact on the product, and different mold structures and different materials will have an impact on the generation and performance of weld lines. This puts forward higher requirements for the evaluation method of welded lines.

At present, the technicians in the injection molding factory usually design molds or debug the injection molding process by virtue of their experience, so that the weld lines on the injection molding products meet the requirements of appearance and mechanical properties, but there is no systematic and effective evaluation system, which wastes energy. and trial cost.

To sum up, the current prior art cannot accurately, effectively and objectively evaluate the appearance and mechanical properties of the weld line, so the prior art needs to be improved.

SUMMARY OF THE INVENTION

The present invention provides an evaluation method and a corresponding evaluation kit for plastic welding lines, which are used to solve the problem that the appearance and mechanical properties of the welding lines cannot be accurately, effectively and objectively evaluated in the prior art. The evaluation method includes the following steps:

Step 1: Prepare an insert, the insert includes a split part and a confluence part, the divert part is used to divide the injected molten resin, and the confluence part is used to guide the molten resin from different directions to converge in one place;

Step 2: Prepare an injection mold, the injection mold has a gate and can accommodate the insert;

Step 3: Fix the insert in the injection mold, the shunt part is close to the gate, and the confluence part is far away from the gate;

Step 4: The molten resin is injected from the gate into the injection mold on which the insert is fixed, and after cooling and molding, the injection mold is opened to obtain an evaluation structure, and a weld line is formed on the evaluation structure;

Step 5: Evaluate the quality of the weld line.

Further, the number of the inserts prepared in the step 1 is more than one;

It also includes step 6, judging whether all the inserts have been used in steps 3 to 5, and if so, end; if not, replace the inserts with different merging parts to change the merging angle of the molten resin, and then Repeat steps three to six.

Further, the evaluation in the fifth step includes evaluating the appearance and/or mechanical properties of the weld line.

Further, in the step 5, the appearance of the weld line is evaluated by providing the depth, length, morphology or structure of the weld line; and/or, by testing the tensile strength, flexural strength and Impact strength evaluates the mechanical properties of the weld lines.

Further, in the third step, the insert is fixed in the injection mold, specifically by means of bonding, magnetic attraction or inlay.

The present invention also provides a plastic fusion line evaluation insert, which includes a shunt part and a junction part, the shape of the junction part is a triangle, and the apex angle of the end of the junction part away from the shunt part is set as the fusion part. The supplementary angle of the merging angle of the resin; the extension direction of the opposite side of the top angle is set as the transverse direction, and the direction perpendicular to the opposite side in the plane of the merging portion is the longitudinal direction; the transverse length of the shunt portion is along the The longitudinal direction increases from a direction away from the opposite side to approaching the opposite side.

Further, the shape of the shunt is any one of a triangle, a semicircle or a polygon.

Further, the insert is a left-right symmetrical structure.

Further, the material of the insert is a material whose temperature resistance is higher than the melting temperature of the resin.

Further, the length of the bottom side of the shunt is L1, the width of the gate is L2, t is the wall thickness of the evaluation structure, and the above parameters satisfy the following formula:

L2≥L1, L1≥10t.

Suitably, the present invention also provides a plastic weld line evaluation kit, comprising an insert and an injection mold, the injection mold has a gate and can accommodate the insert; the insert is the insert described above.

Further, a bonding structure, a magnetic attraction structure or a mosaic structure is provided between the insert and the injection mold.

The present invention at least includes the following beneficial effects: by installing inserts of different shapes in the injection mold, the confluence angle of the molten resin can be easily changed, so that the evaluation structure with weld lines corresponding to different confluence angles can be easily obtained, which can be accurate and efficient. , Objectively evaluate the appearance and mechanical properties of the weld line. The insert can be a metal material, which is fixed in the injection mold through a magnetic attraction structure or an inlay structure, which is convenient for replacing inserts of different shapes; the insert can also be glued and fixed in the injection mold, and there is no need to make any changes to the insert and the injection mold. The additional processing is convenient to replace the inserts of different shapes, the inserts will not shake and shift, so that the inserts can be positioned accurately and the accuracy of the evaluation can be improved; at the same time, the inserts can be made of plastic materials or materials with higher temperature resistance than molten resin, It is not easy to scratch the mold while reducing the cost.

Description of drawings

The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

FIG. 1 is a flow chart of a method of using a method for evaluating a plastic weld line according to an embodiment of the present invention.

2 is a schematic diagram of inserts of different shapes of an evaluation kit for plastic welding lines according to an embodiment of the present invention.

FIG. 3 is a schematic view of the evaluation structure of an evaluation kit for plastic welding lines according to an embodiment of the present invention.

4 is a schematic diagram of an evaluation structure and a corresponding insert of an evaluation kit for a plastic welding line according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of the design dimension of the evaluation structure of an evaluation kit for a plastic welding line according to an embodiment of the present invention.

1- Evaluation structure, 11- Hole structure, 111- Upper part, 112- Lower part, 12- Weld line, 2- Insert, 21- Divide part, 22- Confluence part.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not intended to limit the present invention.

The specific implementation of the present invention is described in detail below in conjunction with specific embodiments:

The present invention provides a method for evaluating a plastic welding line as shown in FIG. 1, comprising:

Step 1: Prepare the insert 2. The insert 2 includes a split part 21 and a confluence part 22. The split part 21 is used to divide the injected molten resin, and the confluence part 22 is used to guide the molten resin from different directions to converge in one place;

Step 2: Prepare an injection mold, the injection mold has a gate and can accommodate the insert 2;

Step 3: Fix the insert 2 in the injection mold, the shunt part 21 is close to the gate, and the confluence part 22 is far away from the gate;

Step 4: The molten resin is injected from the gate into the injection mold with the insert 2 fixed, and after cooling and molding, the injection mold is opened to obtain the evaluation structure 1, and the evaluation structure 1 is formed with a welding line 12;

Step 5: Evaluate the quality of the welding line 12 .

Further, the number of inserts 2 prepared in the above step 1 is more than one; it also includes step 6, judging whether all the inserts 2 have been used in steps 3 to 5, if so, the end; if not, replace it with a different convergence Part 22 of the insert 2 to change the confluence angle of the molten resin, and then repeat steps three to six.

As shown in FIG. 2 , a schematic diagram of the insert 2 of this embodiment is shown. The insert 2 of this embodiment has a left-right symmetrical structure formed integrally, and includes a converging part 22 and a branching part 21 . The shape of the branching part 21 can be any one of triangle, semicircle or polygon; the shape of the confluence part 22 is a triangle. The apex angle of the end of the confluence part 22 away from the branching part 21 is set as the supplementary angle of the confluence angle of the molten resin; the extension direction of the opposite side of the apex angle is set as the transverse direction, and the direction perpendicular to the opposite side in the plane of the confluence part 22 is the longitudinal direction; the lateral length of the splitting portion 21 increases along the longitudinal direction from the direction away from the opposite side to the direction close to the opposite side. When the insert 2 is placed in the injection mold, the branching part 21 needs to be close to the gate of the injection mold, and the confluence part 22 needs to be far away from the gate of the injection mold.

In this embodiment, the insert 2 is installed in the injection mold. For example, an adhesive structure is provided between the injection mold and the insert 2. Therefore, the insert 2 can be bonded through the adhesive structure without changing the mold structure. in an injection mold. For example, epoxy resin is used as an adhesive between the insert 2 and the injection mold to fix the insert 2 in the injection mold. In this way, the original structure of the injection mold does not need to be changed, the installation is easy, and the surface of the injection mold can be protected. No damage and cost reduction. Alternatively, an insert structure matching the insert 2 can also be provided in the injection mold, so that the insert 2 can be fixed in the injection mold through the insert structure.

In some embodiments, the material of the insert 2 may be plastic, metal or other materials whose temperature resistance is higher than that of molten resin. When the insert 2 is made of metal, a magnetic attraction structure, such as a strong magnetic block, can be arranged inside the injection mold, so that the insert 2 is fixed in the injection mold under the magnetic field formed by the strong magnetic block, which can achieve Easy to put and easy to take effect. The insert 2 can also be made of plastic material. Exemplarily, the insert 2 is bonded to the injection mold by epoxy resin. In this way, the original structure of the injection mold does not need to be changed, the installation is easy, and the surface of the injection mold can be protected from damage. and reduce costs. Regardless of whether it is a metal material or a plastic material, the temperature resistance needs to be higher than that of the molten resin, so as to prevent the insert 2 from being bonded to the molten resin due to high temperature melting during the injection molding process, so that the evaluation structure 1 cannot be demolded smoothly.

After the mold is closed, the molten resin is injected into the injection mold and divided by the shunt part 21 of the insert 2. The shunted molten resin then flows along the junction part 22, at the top corner of the end of the junction part 22 away from the shunt part 21 with a certain amount. Convergence Angle Convergence. The apex angle of one end of the converging portion 22 away from the branching portion 21 is set as α, and α is in a complementary relationship with the converging angle.

After that, the molten resin was cooled in an injection mold, and the injection mold was opened to obtain Evaluation Structure 1. As shown in FIG. 3 , the evaluation structure 1 includes a hole structure 11 and a welding line 12 , wherein the hole structure 11 is formed in the form of an insert 2 , and the shape of the hole structure 11 is the same as that of the insert 2 , and it is symmetrical. The welding line 12 is a thin line that is produced by the molten resin from different directions failing to be completely fused at the merging portion 22 at a certain merging angle.

Different weld lines 12 are obtained by exchanging inserts 2 with different α-merging portions 22 in the injection mold and changing the merging angle of the molten resin. Among them, the range of α is 0°-180°. Further, testing the appearance and mechanical properties of the weld line 12 can effectively evaluate the appearance and mechanical properties of the weld line 12 produced by different fusion angles of the molten resin during injection molding.

FIG. 4 is a schematic diagram of the evaluation structure 1 and the corresponding insert 2 according to the embodiment of the present invention. By replacing the inserts 2 with different α merging parts as shown in Fig. 4(a) in the injection mold so that the merging angles of the molten resin are 90°, 135° and 150°, respectively, as shown in Fig. 4(b) The evaluation structure shown in 1. As shown in Fig. 4(b), when the confluence angle is 90°, the weld line 12 is longer in length, has a more obvious V-shaped notch and is deeper; The weld line 12 at ° is shallow in depth, short in length, and no obvious V-shaped notch is observed; the weld line 12 with a confluence angle of 150° is the least obvious among the three groups of weld lines 12, and can hardly be observed. According to the depth and length of the weld line, the quality of the weld line can be qualitatively evaluated. According to the above appearance results, the weld line with a merging angle of 150° has a shallow depth and a short length, and the quality of the weld line is relatively good.

Further, the tensile strength of the weld line 12 was tested using the plastic tensile properties test method (ISO527/2), the flexural strength was tested using the plastics - method of determination of flexural properties (ISO178), and the flexural strength was tested using the plastics - Izod impact test method (ISO180) The impact strength is used to quantitatively evaluate the mechanical properties of the weld line 12. The evaluation results are as follows:

Table 1 Test results of tensile strength, flexural strength and impact strength of weld lines

汇合角度(°)Convergence angle (°)	拉伸强度(MPa)Tensile strength (MPa)	弯曲强度(MPa)Bending strength (MPa)	冲击强度(kJ/m ²) Impact Strength (kJ/m ² )
9090	15.4615.46	16381638	25.7125.71
120120	16.5616.56	17551755	27.5427.54
150150	17.4817.48	18521852	29.0729.07

It can be seen from Table 1 that when the convergence angle of the weld line is 90°, the tensile strength is 15.46MPa, the bending strength is 1638MPa, and the impact strength is 25.71kJ/m ² ; when the convergence angle of the weld line is 120°, the tensile strength is 15.46MPa. The strength is 16.56MPa, the bending strength is 1755MPa, and the impact strength is 27.54kJ/m ² ; when the merging angle of the weld line is 150°, the tensile strength is 17.48MPa, the bending strength is 1852MPa, and the impact strength is 29.07kJ/m ² . From the above evaluation results, it can be seen that the larger the merging angle of the weld line 12, the greater the tensile strength, bending strength and impact strength of the weld line position, and the less easily deformed and broken at the weld line position.

As shown in FIG. 5 , in this embodiment, the length of the bottom side of the shunt 21 is L1, the width of the gate is L2, and the height of the shunt 21 is h1. When the insert 2 is fixed in the injection mold, the shunt 21 to the The distance of the gate is h2, and t is the wall thickness of the evaluation structure 1. The size of h1, that is, the height of the shunt portion 21 affects the shunt of the molten resin; the size of h2, that is, the distance from the shunt portion 21 to the gate, affects the flow direction of the molten resin. Among them, h2 is less than h1, and h1 is less than L1. Preferably, the above parameters satisfy the following formula:

L2≥L1, L1≥10t.

Through the evaluation kit and evaluation method of the present invention, the appearance and mechanical properties of the welding lines 12 with different confluence angles of the plastics that need to be evaluated can be obtained. In a specific embodiment, the induction cooker base is produced by injection molding of ABS material, and it is found through mold flow simulation analysis that the position of the induction cooker base heat dissipation grille has a welding line 12 with a 70° converging angle, while the induction cooker base heat dissipation grille has a larger volume and a different shape. It is irregular, and the welding line 12 at this part cannot be easily evaluated with a testing instrument. The present invention uses the same ABS material as this part to obtain the evaluation structure 1 with the fusion line 12 with a 70° converging angle through injection molding of the evaluation kit. Whether the appearance and mechanical properties meet the requirements.

Thus, the present invention provides an evaluation kit and an evaluation method for a plastic welding line, the evaluation kit includes an insert and an injection mold. By changing the inserts of different shapes in the injection mold, and changing the fusion angle of the molten resin, the evaluation structures with different fusion lines of the fusion angle were obtained. The appearance and mechanical properties of the weld line are then tested, which can effectively and accurately evaluate the appearance and mechanical properties of the weld line produced by different fusion angles of the molten resin during injection molding.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims

A method for evaluating plastic weld lines, comprising the following steps:

Step 1: Prepare an insert, the insert includes a split part and a confluence part, the divert part is used to divide the injected molten resin, and the confluence part is used to guide the molten resin from different directions to converge in one place;

Step 2: Prepare an injection mold, the injection mold has a gate and can accommodate the insert;

Step 3: Fix the insert in the injection mold, the shunt part is close to the gate, and the confluence part is far away from the gate;

Step 4: The molten resin is injected from the gate into the injection mold on which the insert is fixed, and after cooling and molding, the injection mold is opened to obtain an evaluation structure, and a weld line is formed on the evaluation structure;

Step 5: Evaluate the quality of the weld line.
A method for evaluating plastic weld lines according to claim 1, wherein the number of the inserts prepared in the step 1 is more than one;

It also includes step 6, judging whether all the inserts have been used in steps 3 to 5, and if so, end; if not, replace the inserts with different merging parts to change the merging angle of the molten resin, and then Repeat steps three to six.
A method for evaluating plastic weld lines according to claim 1, wherein the evaluation in step 5 includes evaluating the appearance and/or mechanical properties of the weld lines.
The method for evaluating a plastic weld line according to claim 3, wherein in the step 5, the appearance of the weld line is evaluated by providing the depth, length, morphology or structure of the weld line; and /or, evaluating the mechanical properties of the weld line by testing the tensile strength, flexural strength and impact strength of the weld line.
A method for evaluating plastic weld lines according to claim 1, wherein in the step 3, the insert is fixed in the injection mold, specifically by means of bonding, magnetic attraction or inlay. of.
A plastic welding line evaluation insert is characterized in that it comprises a shunt part and a junction part, the shape of the junction part is a triangle, and the vertex angle of the end of the junction part away from the shunt part is set to the molten resin The supplementary angle of the merging angle; the extension direction of the opposite side of the vertex angle is set to be transverse, and the direction perpendicular to the opposite side in the plane of the junction is the longitudinal direction; the transverse length of the shunt is along the The longitudinal direction increases from the direction away from the opposite side to the direction close to the opposite side.
The plastic weld line evaluation insert according to claim 6, wherein the shape of the shunt is any one of a triangle, a semicircle or a polygon.
The plastic weld line evaluation insert according to claim 6, wherein the insert is a left-right symmetrical structure.
The plastic welding line evaluation insert according to claim 6, wherein the material of the insert is a material whose temperature resistance is higher than the melting temperature of the resin.
The plastic welding line evaluation insert according to claim 6, characterized in that, the length of the bottom side of the shunt is L1, the width of the gate is L2, and t is the wall thickness of the evaluation structure, The above parameters satisfy the following formula:

L2≥L1, L1≥10t.
A plastic weld line evaluation kit, characterized by comprising an insert and an injection mold, the injection mold having a gate and capable of accommodating the insert; the insert is the one described in any one of claims 10-14 insert.
The plastic welding line evaluation insert according to claim 11, wherein an adhesive structure, a magnetic attraction structure or an inlay structure is provided between the insert and the injection mold.