Injection molding process for reducing flow marks in injection molded parts

Abstract

The application discloses an injection molding process for reducing flow marks of an injection molding workpiece, comprising the following steps: step 1: a control system controls an injection molding machine to start injecting plastic raw materials in a molten state into a cavity of a mold, and metal powder with ferromagnetism is mixed in the plastic raw materials; step 2: after the flow fills the cavity, the control system controls a magnetic field supply device to orient the metal powder in the molten raw materials; the magnetic field supply device is used for applying a parallel and uniform magnetic field to a cavity area of the mold, and the magnetic induction line direction of the parallel and uniform magnetic field is parallel to a product appearance surface of the injection molding workpiece. Through the orientation of the metal powder in the plastic raw materials in the molten state, the sheet-shaped metal particles can be parallel to the appearance surface of the product, and the flow marks formed by the spray-free material with a metallic texture after the injection molding is completed can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of injection molding technology, in particular to an injection molding process for reducing flow marks of an injection molded workpiece. BACKGROUND

[0002] With the increasing attention to environmental protection in social production and life, traditional spraying and powder spraying processes are gradually marginalized due to their disadvantages such as strong odor, poor operating environment, and toxicity. In order to meet the diversified needs of television products, materials with metallic texture but free of spraying are gradually showing their competitiveness. The free-spraying material refers to a kind of material that can achieve a metallic surface texture by direct injection molding. Currently, it is mainly achieved by adding a certain amount of metal particles such as iron powder, aluminum powder, silver powder, and copper powder in the base material. However, due to the uncertainty of the deflection of metal particles in the flow, at the site where the flow is welded, the metal particles are prone to lateral turning, forming an angle with the product surface, which is not easy to reflect light, leading to the formation of flow marks during the injection molding process, affecting the quality of the product.

[0003] When there are holes or convex column structures in the mold cavity that need to be avoided by the flow, the metal powder in the flow may accumulate before and after encountering the avoidance site. If the metal powder accumulates on the product surface, it will form a small continuous bright line. This line is not easy to detect when viewed directly, but when the light source is directed at it, the corresponding flow mark can be found. For high-quality products that require high surface presentation, improvements are needed. SUMMARY

[0004] In order to reduce the flow marks formed by the free-spraying material with metallic texture after injection molding, the present application provides an injection molding process for reducing flow marks of an injection molded workpiece.

[0005] The injection molding process for reducing flow marks of an injection molded workpiece provided by the present application adopts the following technical solution:

[0006] The injection molding process for reducing flow marks of an injection molded workpiece includes the following steps:

[0007] Step 1: The control system controls the injection molding machine to start injecting molten plastic raw materials into the mold cavity. The plastic raw materials contain metal powder with ferromagnetic properties.

[0008] Step 2: After the flow fills the cavity, the control system controls the magnetic field supply device to orient the metal powder in the molten raw materials. The magnetic field supply device is used to apply a parallel and uniform magnetic field to the cavity area of the mold. The magnetic field lines of the parallel and uniform magnetic field are parallel to the product appearance surface of the injection molded part.

[0009]

[0009] Step 3: When the flow cools down, the control system controls the magnetic field supply device to stop applying a magnetic field to the cavity area of the mold.

[0010] By adopting the technical scheme, in the process of filling the molten plastic raw material into the mold cavity, the control system controls the magnetic field supply device to apply a uniform magnetic field to the area where the mold cavity is located, so that the magnetic field of the magnetic field device orients the metal powder with magnetism. When the magnetic field is uniformly distributed, the metal powder can be kept parallel as much as possible. Therefore, when there is a structure in the cavity of the mold that causes the flow to converge or diverge, the metal powder is less likely to concentrate during the convergence and divergence of the flow. Therefore, the metal powder is less likely to form flow marks, which is beneficial to improve the uniformity of the distribution of the metal powder in the cavity. After the flow is cooled, the control system controls the magnetic field supply device to stop applying a magnetic field to the cavity area of the mold, which can reduce the situation that the metal powder continues to move towards the direction of the two magnetic poles of the magnetic field supply device under the action of the magnetic force. This is beneficial to the uniform distribution of the metal powder in the injection molded part.

[0011] Optionally, the magnetic field supply device includes a first magnetic field supply device and two second magnetic field supply devices. The openings of the two second magnetic field supply devices are oppositely arranged and perpendicular to the direction of the opening side of the first magnetic field supply device. In step 2, the first magnetic field supply device is used for orientation, then the first magnetic field supply device is removed, and then the two second magnetic field supply devices are used for orientation of the metal powder on the edge regions of the two opposite sides of the mold cavity.

[0012] By adopting the technical scheme, the metal powder in the mold cavity is arranged by the first magnetic field supply device. The side walls near the two magnetic poles of the main magnet in the mold cavity are prone to form a concentrated situation of metal powder. When the first magnetic field supply device is removed, the two second magnetic field supply devices are used to orient the metal powder on the edge regions near the two magnetic poles of the original first magnetic field supply device in the mold cavity. The distribution of the metal powder on the edge regions near the original first magnetic field region in the mold cavity is more uniform.

[0013] Optionally, the magnetic field supply device includes a main magnet and a magnetic yoke shell. The main magnet has a horseshoe structure. The magnetic yoke shell includes a slot body with a horseshoe structure. The two ends of the slot body are closed. The slot opening of the slot body faces the center region of the slot body. The slot body is detachably provided with an inner side cover. The inner side cover has a horseshoe structure. The inner side cover is used to close the slot opening of the slot body.

[0014] By adopting the technical scheme, when the magnetic field supply device is in use, the inner cover is separated from the groove body, and the area where the cavity of the mold is located is located in the inner area of the main magnet; the main magnet is arranged in a horseshoe-shaped structure, so that a relatively uniform magnetic field is formed in the inner area of the main magnet, and the magnetic circuit of the outer area of the main magnet is mainly concentrated in the interior of the magnetic yoke shell; and the flow in the cavity is subjected to the orientation effect of the uniform magnetic field. When the magnetic field of the shielding magnetic field supply device is shielded, the inner cover can cover the slot of the groove body, so that the magnetic field in the inner area of the main magnet can be distributed along the shape of the inner cover as much as possible, and the influence of the movement of the magnetic field in the inner area of the main magnet on the oriented metal powder is reduced.

[0015] Optionally, the groove body is provided with a first driving member, the first driving member is used to drive the inner cover to move laterally to close the slot of the groove body; the inner side surface of the main magnet is flush with the slot of the groove body, the inner cover abuts against the main magnet, the magnetic yoke shell is sleeved with a plurality of elastic coils, and the elastic coils are used to force the inner cover to abut against the slot of the groove body.

[0016] By adopting the technical scheme, the inner cover is driven by the first driving member, so that the opening and closing state of the inner cover can be remotely controlled, and meanwhile, the inner cover and the cover body are connected with each other through the first driving member, so that the groove body and the inner cover can move simultaneously. The elastic coil can force the inner cover to abut against the slot of the groove body by the elastic force, so that the inner cover can shield the magnetic field as much as possible, and the main material of the elastic coil is usually rubber, so that the elastic coil cannot easily affect the distribution of the magnetic field.

[0017] Optionally, the magnetic field supply device comprises two magnetic yoke half-frames, the magnetic yoke half-frame comprises a horizontal plate and two longitudinal plates, the horizontal plate and the two longitudinal plates are connected to form a half-enclosing structure, the horizontal plate is provided with a first magnetic pole plate, the first magnetic pole plate is located on the inner side of the magnetic yoke half-frame, a plurality of permanent magnets are arranged on the side of the first magnetic pole plate away from the horizontal plate, a second magnetic pole plate is arranged on the side of the permanent magnet away from the first magnetic pole plate, when the magnetic field supply device is in use, the two magnetic yoke half-frames are combined to form a frame-shaped structure by approaching each other, and the inner side of the magnetic yoke half-frame is provided with a magnetic yoke plate in a detachable manner, and the opposite two side edges of the magnetic yoke plate are in one-to-one correspondence with the two longitudinal plates of the magnetic yoke half-frame and abut against each other when the magnetic yoke plate is in use.

[0018] By adopting the technical scheme, the two yoke half-frames of the magnetic field supply device are spliced to form a frame structure, and the magnetic circuit generated by the magnetic field supply device sequentially passes through the magnet on one side, the second magnetic pole plate on one side, the second magnetic pole plate on the other side, the permanent magnet on the other side, the first magnetic pole plate on the other side, the yoke half-frame on the other side, the yoke half-frame on one side, the first magnetic pole plate on one side, and the permanent magnet on one side, thereby forming a loop. The magnetic field between the two second magnetic pole plates is uniformly distributed, and the frame structure formed by splicing the two yoke half-frames surrounds the mold, so that the magnetic field of the magnetic field device can orient the metal powder in the mold cavity. When it is necessary to shield the magnetic field of the magnetic field supply device, the magnetic plate is first placed between the two longitudinal plates of the yoke half-frame, and the yoke half-frame and the yoke plate are combined to form a frame structure, so that the magnetic field of the permanent magnet inside the yoke half-frame is mainly conducted through the yoke half-frame and the yoke, that is, the yoke half-frame has a shielding effect on the magnetic field inside the yoke half-frame. After the two yoke half-frames are separated from each other, the injection molded part in the mold can be taken out.

[0019] Optionally, opposite sides of the yoke plate are respectively provided with pressing plates, the pressing plates are perpendicular to the yoke plate, wide surfaces of the pressing plates face thickness surfaces of the yoke plate, one side of the pressing plate and the yoke plate are connected through a connecting plate, and an insertion gap for inserting the longitudinal plate is formed between the pressing plate and the thickness surface of the yoke plate, and a width of the insertion gap is smaller than a thickness of the longitudinal plate.

[0020] By adopting the technical scheme, when the yoke plate is inserted between the two longitudinal plates of the yoke half-frame, the two longitudinal plates of the yoke half-frame are inserted into the corresponding insertion gaps, and the longitudinal plate forces the insertion gap between the pressing plate and the yoke plate to increase, and at the same time, the pressing plate and the yoke plate form a clamping force on the longitudinal plate, so as to facilitate the thickness surface of the yoke plate to be fully attached to the longitudinal plate, and further facilitate the combination of the yoke half-frame and the yoke plate to form a good conduction effect on the magnetic field.

[0021] Optionally, an outer side wall of the yoke half-frame is provided with a rib plate, the rib plate includes a horizontal rib plate and two longitudinal rib plates, the horizontal rib plate is integrally connected with the two longitudinal rib plates, the horizontal rib plate is located on an outer side of the horizontal plate and is perpendicular to the horizontal plate, the two longitudinal rib plates correspond to the two longitudinal plates respectively, and the longitudinal rib plate is located on an outer side of the corresponding longitudinal plate and is perpendicular to the longitudinal plate.

[0022] By adopting the technical scheme, the rib plate has a reinforcing effect on the yoke half-frame, when the longitudinal plates of the two yoke half-frames are correspondingly abutted, the two longitudinal plates of the same yoke half-frame are not easy to deform to approach or separate from each other, the structural stability of the frame structure formed by combining the two yoke half-frames is enhanced, and the conduction of the magnetic field is facilitated.

[0023] Optionally, one of the two longitudinal plates is designated as the first longitudinal plate, and the other longitudinal plate is designated as the second longitudinal plate. The thickness surface of the first longitudinal plate on the side away from the horizontal plate is designated as an outwardly convex arc surface, and the thickness surface of the second longitudinal plate is designated as an inwardly concave arc surface that matches the outwardly convex arc surface. When the two magnetic yoke half-frames are spliced ​​together, the first longitudinal plate of one magnetic yoke half-frame and the second longitudinal plate of the other magnetic yoke half-frame are connected by the matching of the outwardly convex arc surface and the inwardly concave arc surface.

[0024] By adopting the above technical solution, when the two magnetic yoke half-frames are connected, the convex arc surface and the concave arc surface are adapted to each other, so that the first longitudinal plate of one magnetic yoke half-frame and the second longitudinal plate of the other magnetic yoke half-frame are aligned as much as possible along the thickness direction, so that the longitudinal plates of the two magnetic yoke half-frames can fit together more fully when they are connected, which is conducive to the combined structure formed by the two magnetic yoke half-frames forming a good magnetic field conduction effect.

[0025] Optionally, the convex arc surface is provided with a positioning protrusion, the center line of which is along the radial direction of the convex arc surface and parallel to the longitudinal plate, and the concave arc surface is provided with a positioning groove that matches the positioning protrusion.

[0026] By adopting the above technical solution, when the convex arc surface abuts against the concave arc surface, the positioning protrusion is inserted into the positioning groove. This helps to reduce the gap between the convex arc surface and the concave arc surface that extends along the center line of the convex arc surface, and further improves the fit between the convex arc surface and the concave arc surface. The concave arc surface has a guiding effect on the positioning protrusion, making it easier for the positioning protrusion to align with the positioning groove.

[0027] In summary, this application includes at least one of the following beneficial technical effects:

[0028] 1. By controlling the magnetic field supply device to apply a uniform magnetic field to the area of ​​the mold cavity through the control system, the magnetic field of the magnetic field device orients the magnetic metal powder. When there is a structure in the mold cavity that causes the material flow to converge or diverge, the metal powder is less likely to concentrate during the convergence and divergence of the material flow, thus making it less likely for the metal powder to form flow marks.

[0029] 2. After the metal powder in the mold cavity is processed by the first magnetic field supply device, the sidewalls of the two magnetic poles near the main magnet in the mold cavity are prone to metal powder concentration. When the first magnetic field supply device is removed, two second magnetic field supply devices are used to orient the metal powder in the edge area of ​​the mold cavity near the two magnetic poles of the original first magnetic field supply device, so that the distribution of metal powder in the edge area of ​​the mold cavity near the original first magnetic field area is more uniform. Attached Figure Description

[0030] Figure 1is a schematic diagram of the steps of the injection molding process for reducing flow marks of an injection molded workpiece of Example 1.

[0031] Figure 2 is a schematic diagram of the use state of the magnetic field supply device of Example 1.

[0032] Figure 3 is a schematic diagram for embodying the open state of the inner cover of Example 1.

[0033] Figure 4 is a schematic diagram for embodying the closed state of the inner cover of Example 1.

[0034] Figure 5 is a schematic diagram of the use state of the magnetic field supply device of Example 2.

[0035] Figure 6 is a schematic diagram for embodying the separated state of the magnetic yoke plate and the magnetic yoke half-frame of Example 2.

[0036] Figure 7 is a schematic diagram for embodying the connected state of the magnetic yoke plate and the magnetic yoke half-frame of Example 2.

[0037] Figure 8 is a schematic diagram for embodying the positional relationship between the first magnetic field supply device and the second magnetic field supply device of Example 3.

[0038] BRIEF DESCRIPTION OF DRAWINGS 1, magnetic field supply device; 11, main magnet; 12, magnetic yoke shell; 121, slot body; 122, inner cover; 123, first driving member; 124, elastic coil; 13, magnetic yoke half-frame; 131, horizontal plate; 132, vertical plate; 1321, first vertical plate; 1322, second vertical plate; 1323, outer convex arc surface; 1324, inner concave arc surface; 1325, positioning rod; 1326, positioning protrusion; 1327, positioning groove; 14, first magnetic pole plate; 15, permanent magnet; 16, second magnetic pole plate; 17, magnetic yoke plate; 171, pressing plate; 1711, inclined guide surface; 172, connecting plate; 173, plug-in gap; 174, inclined support piece; 18, rib plate; 181, horizontal rib plate; 182, vertical rib plate; 1821, notch; 101, first magnetic field supply device; 102, second magnetic field supply device. DETAILED DESCRIPTION

[0039] The following will be described in detail below with reference to the accompanying drawings. Figures 1-8 The present application is further described in detail.

[0040] Example 1

[0041] The present application discloses an injection molding process for reducing flow marks of an injection molded workpiece. Referring to the drawings, Figure 1 The injection molding process for reducing flow marks of an injection molded workpiece comprises the following steps:

[0042] Step 1: The control system controls the injection molding machine to start injecting the plastic raw material in a molten state into the cavity of the mold, and the plastic raw material is mixed with metal powder having ferromagnetic properties, and the material of the metal powder can be iron, cobalt, nickel or related alloy materials;

[0043] Step 2: During the process of the material flow into the mold cavity to fill the cavity, the control system controls the magnetic field supply device 1 to orient the metal powder in the molten raw material; the magnetic field supply device 1 is used to apply a parallel and uniform magnetic field to the cavity area of the mold, and the magnetic field supply device 1 is used to apply a parallel and uniform magnetic field to the cavity area of the mold. The direction of the magnetic field lines of the parallel and uniform magnetic field is parallel to the product appearance surface of the injection molded part;

[0044] Step 3: When the material flow cools down, the control system controls the magnetic field supply device to stop applying a magnetic field to the cavity area of the mold.

[0045] Referring to Figure 2 and Figure 3 , the magnetic field supply device 1 includes a main magnet 11 and a magnetic yoke shell 12, the magnetic yoke shell 12 is made of soft iron, A3 steel and soft magnetic alloy, etc., the main magnet 11 is in a horseshoe structure, the magnetic yoke shell 12 includes a slot body 121 in a horseshoe structure, the slot body 121 is closed at both ends, and the slot opening of the slot body 121 faces the center area of the slot body 121, and the slot body 121 is detachably provided with an inner side cover 122, the inner side cover 122 is a bent piece in a horseshoe structure, and the inner side cover 122 is used to close the slot opening of the slot body 121.

[0046] When the inner side cover 122 closes the slot opening of the slot body 121, the magnetic circuit inside the main magnet 11 is mainly conducted through the inner side cover 122, and under the joint action of the slot body 121 and the inner side cover 122, the magnetic circuit of the magnetic field supply device 1 is shielded, so that the metal powder in the mold cavity is difficult to continue to move towards the direction close to the two magnetic poles of the main magnet 11 under the action of the magnetic force, thereby reducing the problem of local excessive concentration of the metal powder.

[0047] Referring to Figure 3 and Figure 4 , the magnetic yoke shell 12 is provided with two first driving members 123, and the installation positions of the two first driving members 123 correspond to the two magnetic pole positions of the main magnet 11 respectively, the first driving member 123 can be a linear driving device such as a pneumatic cylinder or a hydraulic cylinder, and the first driving member 123 is used to drive the inner side cover 122 to move laterally to close the slot opening of the slot body 121. When the inner side cover 122 closes the slot body 121, the magnetic field inside the main magnet 11 is mainly conducted through the inner side cover 122, so that the uniform magnetic field of the magnetic field supply device 1 is shielded.

[0048] Referring to Figure 3The inner side of the main magnet 11 is flush with the slot of the slot body 121, the inner side cover 122 abuts against the main magnet 11, the magnetic yoke shell 12 is sleeved with a plurality of elastic coils 124, the elastic coils 124 can be made of rubber bands or elastic bands, the elastic coils 124 are arranged in sequence along the extension direction of the main magnet 11, the elastic coils 124 are always kept in tension, and the elastic coils 124 are used to force the inner side cover 122 to abut against the slot of the slot body 121.

[0049] The implementation principle of the embodiment is that: in the process of injecting the molten plastic raw material into the mold cavity, the magnetic field supply device 1 applies a uniform magnetic field to the flow, and for the metal powder which has ferromagnetic properties and is in the form of a sheet, the metal powder is usually parallel to the magnetic induction line direction of the magnetic field, so that the metal powder can be kept parallel as much as possible. When there is a structure in the cavity of the mold that causes the flow to converge or diverge, the metal powder is not prone to concentrate with the convergence and divergence of the flow under the action of the magnetic field, so that the metal powder is not prone to form flow marks. After the flow cools, the control system controls the magnetic field supply device to stop applying a magnetic field to the cavity area of the mold, which can prevent the metal powder from moving towards the direction of the two poles of the magnetic field supply device 1 under the action of the magnetic force, and is beneficial to make the metal powder distribute more uniformly in the injection molded part.

[0050] Embodiment 2

[0051] With reference to Figure 5 The difference between the embodiment and the embodiment is that: the magnetic field supply device 1 includes two magnetic yoke half-frames 13, the magnetic yoke half-frames 13 include a horizontal plate 131 and two vertical plates 132, the magnetic yoke half-frames 13 are integrated half-enclosing structures, the horizontal plate 131 is provided with a first magnetic pole plate 14, the first magnetic pole plate 14 is located on the inner side of the magnetic yoke half-frame 13, a plurality of permanent magnets 15 are arranged on the side of the first magnetic pole plate 14 away from the horizontal plate 131, and a second magnetic pole plate 16 is arranged on the side of the permanent magnet 15 away from the first magnetic pole plate 14. When the magnetic field supply device 1 is used, the two magnetic yoke half-frames 13 are combined to form a frame-shaped structure.

[0052] When the two magnetic yoke half-frames 13 of the magnetic field supply device 1 are spliced and combined, the magnetic circuit generated by the magnetic field supply device 1 sequentially passes through: a magnet on one side, a second magnetic pole plate 16 on one side, another second magnetic pole plate 16, a permanent magnet 15 on the other side, a first magnetic pole plate 14 on the other side, a magnetic yoke half-frame 13 on the other side, a magnetic yoke half-frame 13 on one side, a first magnetic pole plate 14 on one side, and a permanent magnet 15 on one side, thereby forming a loop. The magnetic field between the two second magnetic pole plates 16 is uniformly distributed, and by surrounding the mold with the two magnetic yoke half-frames 13, a uniform magnetic field can be applied to the cavity area of the mold. After the injection molding is completed, the two magnetic yoke half-frames 13 are separated, and the injection molded part in the mold can be taken out.

[0053] With reference to Figure 6 and Figure 7The inner side of the magnetic yoke half frame 13 is detachably provided with a magnetic yoke plate 17, the magnetic yoke plate 17 is parallel to the horizontal plate 131, and the magnetic yoke plate 17 is in abutment with the two longitudinal plates 132 through the thickness faces of the two opposite sides. When the magnetic field shielding of the magnetic field supply device 1 is needed, the magnetic yoke plate 17 is first placed between the two longitudinal plates 132 of the magnetic yoke half frame 13, and the combination between the magnetic yoke half frame 13 and the magnetic yoke plate 17 forms a frame-shaped structure, so that the magnetic field of the permanent magnet 15 in the inner side of the magnetic yoke half frame 13 is mainly conducted through the magnetic yoke half frame 13 and the magnetic yoke, that is, the magnetic yoke half frame 13 forms a shielding effect on the magnetic field in the inner side of the magnetic yoke half frame 13.

[0054] The magnetic yoke plate 17 in the embodiment can be manually installed and separated, or can be driven by a linear driving mechanism fixedly installed on the magnetic yoke half frame 13. The linear driving mechanism can be a pneumatic cylinder or a hydraulic cylinder.

[0055] Referring to Figure 6 , the two opposite sides of the magnetic yoke plate 17 are respectively provided with a pressing plate 171, the pressing plate 171 is perpendicular to the magnetic yoke plate 17, the wide face of the pressing plate 171 faces the thickness face of the magnetic yoke plate 17, and the pressing plate 171 is connected with the magnetic yoke plate 17 through a connecting plate 172 on one side. The connecting plate 172 is arc-shaped in whole, the thickness face between the pressing plate 171 and the magnetic yoke plate 17 forms an insertion gap 173 for the longitudinal plate 132, and the width of the insertion gap 173 is smaller than the thickness of the longitudinal plate 132. The thickness face of the side of the pressing plate 171 away from the connecting plate 172 and the side face close to the magnetic yoke plate 17 form an inclined guide face 1711, which is used for guiding the relative movement between the pressing plate 171 and the longitudinal plate 132.

[0056] When the magnetic yoke plate 17 is used, the magnetic yoke plate 17 is inserted between the two longitudinal plates 132 of the magnetic yoke half frame 13, and the vertical plate is inserted into the insertion gap 173 between the pressing plate 171 and the thickness face of the magnetic yoke plate 17. At this time, the pressing plate 171 and the magnetic yoke plate 17 form a clamping force on the longitudinal plate 132. When the two opposite sides of the magnetic yoke plate 17 are in abutment with the two longitudinal plates 132 of the magnetic yoke half frame 13 one by one, the fit can be more sufficient.

[0057] Referring to Figure 6 , the two opposite sides of the magnetic yoke plate 17 correspond to a group of inclined supporting pieces 174, the inclined supporting pieces 174 are elastic metal sheets, the number of each group of inclined supporting pieces 174 is two, the two inclined supporting pieces 174 in the same group are located on the two opposite sides of the magnetic yoke plate 17, one side of the inclined supporting piece 174 is fixedly connected with the side yoke plate, and the two inclined supporting pieces 174 in the same group gradually incline away from each other in the direction away from the magnetic yoke plate 17. The side of the inclined supporting piece 174 away from the fixed side is used for abutting against the magnetic yoke plate 17. By arranging two inclined supporting pieces 174, the stability of the magnetic yoke plate 17 when abutting against the longitudinal plate 132 is improved.

[0058] Referring to Figure 7, one of the two longitudinal plates 132 is provided as a first longitudinal plate 1321, and the other longitudinal plate 132 is provided as a second longitudinal plate 1322, the thickness surface of the first longitudinal plate 1321 away from the side of the horizontal plate 131 is provided as an outer convex arc surface 1323, and the thickness surface of the second longitudinal plate 1322 is provided as an inner concave arc surface 1324 matched with the outer convex arc surface 1323, when the two magnetic yoke half frames 13 are spliced, the first longitudinal plate 1321 of one of the magnetic yoke half frames 13 is connected with the second longitudinal plate 1322 of the other magnetic yoke half frame 13 through the matching of the outer convex arc surface 1323 and the inner concave arc surface 1324. The outer convex arc surface 1323 of the first longitudinal plate 1321 is inserted with a positioning rod 1325, the center line direction of the positioning rod 1325 is along the radial direction of the outer convex arc surface 1323, and is parallel to the first longitudinal plate 1321, the part of the positioning rod 1325 extending out of the outer convex arc surface 1323 is provided as a positioning protrusion 1326, and the inner concave arc surface 1324 is provided with a positioning groove 1327 matched with the positioning protrusion 1326.

[0059] The matching of the outer convex arc surface 1323 and the inner concave arc surface 1324 between the first longitudinal plate 1321 and the second longitudinal plate 1322 can make the two longitudinal plates 132 of the magnetic yoke half frame 13 as matched as possible. In addition, by matching the positioning protrusion 1326 with the positioning groove 1327, when the outer convex arc surface 1323 and the inner concave arc surface 1324 abut, it is not easy to form a gap with gradually changing width between the outer convex arc surface 1323 and the inner concave arc surface 1324, that is, it is beneficial to ensure the fit between the outer convex arc surface 1323 and the inner concave arc surface 1324.

[0060] Referring to Figure 6 The outer side wall of the magnetic yoke half frame 13 is provided with two rib plates 18, the two rib plates 18 are arranged in sequence along the extension direction of the intersection line between the horizontal plate 131 and the longitudinal plate 132, the rib plate 18 includes a horizontal rib plate 181 and two longitudinal rib plates 182, the horizontal rib plate 181 is integrally connected with the two longitudinal rib plates 182, the horizontal rib plate 181 is located on the outer side of the horizontal plate 131 and is perpendicular to the horizontal plate 131, the two longitudinal rib plates 182 correspond to the two longitudinal plates 132 respectively, the longitudinal rib plate 182 is located on the outer side of the corresponding longitudinal plate 132 and is perpendicular to the longitudinal plate 132, and the longitudinal rib plate 182 is provided with a notch 1821 for avoiding the pressing plate 171. The rib plate 18 strengthens the magnetic yoke half frame 13 and reduces the mutual extrusion deformation of the two half frames when aligned.

[0061] Embodiment 3

[0062] Referring to Figure 8The embodiment differs from the embodiment 1 in that the magnetic field supply device 1 comprises a first magnetic field supply device 101 and two second magnetic field supply devices 102, the two second magnetic field supply devices 102 are identical in structure with the first magnetic field supply device 101, the two second magnetic field supply devices 102 are oppositely arranged in the opening direction and are perpendicular to the orientation of the opening side of the first magnetic field supply device 101, the first magnetic field supply device 101 is used to orient the metal powder in step 2, then the first magnetic field supply device 101 is removed, and then the two second magnetic field supply devices 102 are used to orient the metal powder in the edge regions of the two opposite sides of the mold cavity.

[0063] After the metal powder in the mold cavity is arranged by the first magnetic field supply device 101, the sidewalls close to the two magnetic poles of the main magnet 11 in the mold cavity are prone to form a concentrated condition of the metal powder, when the first magnetic field supply device 101 is removed, the two second magnetic field supply devices 102 are used to orient the metal powder in the edge regions close to the two magnetic poles of the original first magnetic field supply device 101 in the mold cavity, so that the distribution of the metal powder in the edge regions close to the original first magnetic field region in the mold cavity is more uniform.

[0064] The above are the preferred embodiments of the present application, which do not limit the protection scope of the present application, therefore: any equivalent changes made on the structure, shape and principle of the present application should be covered within the protection scope of the present application.

Claims

1. An injection molding process for reducing flow marks in an injection molded article, characterized by: It comprises the following steps: Step 1: the control system controls the injection molding machine to start injecting plastic raw materials in a molten state into the cavity of the mold, and the plastic raw materials are mixed with metal powder having ferromagnetism; Step 2: after the flow fills the cavity, the control system controls the magnetic field supply device (1) to orient the metal powder in the molten raw material; the magnetic field supply device (1) is used to apply a parallel and uniform magnetic field to the cavity area of the mold, and the magnetic field of the parallel and uniform magnetic field is parallel to the product appearance surface of the injection molded part; Step 3: when the flow cools down, the control system controls the magnetic field supply device to stop applying a magnetic field to the cavity area of the mold; The magnetic field supply device (1) comprises two magnetic yoke half-frames (13), the magnetic yoke half-frames (13) comprise a horizontal plate (131) and two vertical plates (132), the horizontal plate (131) and the two vertical plates (132) are connected to form a half-enclosing structure, the horizontal plate (131) is provided with a first magnetic pole plate (14), the first magnetic pole plate (14) is located on the inner side of the magnetic yoke half-frame (13), a plurality of permanent magnets (15) are arranged on the side of the first magnetic pole plate (14) away from the horizontal plate (131), and a second magnetic pole plate (16) is arranged on the side of the permanent magnet (15) away from the first magnetic pole plate (14); when the magnetic field supply device (1) is used, the two magnetic yoke half-frames (13) are combined to form a frame structure by approaching each other; the inner side of the magnetic yoke half-frame (13) is detachably provided with a magnetic yoke plate (17), and the opposite two side edges of the magnetic yoke plate (17) are respectively in one-to-one correspondence with the two vertical plates (132) of the magnetic yoke half-frame (13) when the magnetic yoke plate (17) is used. The opposite two sides of the magnetic yoke plate (17) are respectively provided with a pressing plate (171), the pressing plate (171) is perpendicular to the magnetic yoke plate (17), the wide surface of the pressing plate (171) faces the thickness surface of the magnetic yoke plate (17), one side of the pressing plate (171) and the magnetic yoke plate (17) are connected through a connecting plate (172), and the thickness surface of the pressing plate (171) and the magnetic yoke plate (17) form a plug-in gap (173) for inserting the vertical plate (132), and the width of the plug-in gap (173) is smaller than the thickness of the vertical plate (132).

2. The injection molding process of reducing flow marks in an injection molded part of claim 1, wherein: The outer side wall of the magnetic yoke half-frame (13) is provided with a rib plate (18), the rib plate (18) comprises a horizontal rib plate (181) and two vertical rib plates (182), the horizontal rib plate (181) and the two vertical rib plates (182) are integrally connected, the two vertical rib plates (182) correspond to the two vertical plates (132) respectively, and the vertical rib plate (182) is located on the outer side of the corresponding vertical plate (132).

3. The injection molding process of reducing flow marks in an injection molded part of claim 1, wherein: One of the two longitudinal plates (132) is provided as a first longitudinal plate (1321), and the other longitudinal plate (132) is provided as a second longitudinal plate (1322), a thickness surface of the first longitudinal plate (1321) away from the transverse plate (131) is provided as an outer convex arc surface (1323), a thickness surface of the second longitudinal plate (1322) is provided as an inner concave arc surface (1324) matched with the outer convex arc surface (1323), when the two magnetic yoke half frames (13) are spliced, the first longitudinal plate (1321) of one of the magnetic yoke half frames (13) is connected with the second longitudinal plate (1322) of the other magnetic yoke half frame (13) through the matching of the outer convex arc surface (1323) and the inner concave arc surface (1324).

4. The injection molding process of reducing flow marks in an injection molded part of claim 3, wherein: The outer convex arc surface (1323) is convexly provided with a positioning protrusion (1326), a center line of the positioning protrusion (1326) is along a radial direction of the outer convex arc surface (1323) and parallel to the longitudinal plate (132), and the inner concave arc surface (1324) is provided with a positioning groove (1327) matched with the positioning protrusion (1326).

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