FR2888152A1 - Rotating mold for e.g. automobile industry, has plastic materials injected simultaneously by plastic material injecting units, respectively, when injection molding machine is in closed position, and parts mounted on respective plates - Google Patents

Abstract

The mold has parts (10, 13) whose one side is mounted in contact with respective fixed and movable plates (11, 18) of an injection molding machine (100) and other side has mold cavities connected to plastic material injecting units (104, 105), respectively. A part (12) is mounted rotating along rotational axis (15) on a frame (14) guided in movement (17) on two columns (16) of the machine. Plastic materials are injected simultaneously by the units (104, 105), respectively, when the machine is in closed position. Independent claims are also included for the following: (1) an injection molding machine for molding and overmolding parts in plastic material comprising rotating mold (2) an injecting method for molding and overmolding parts in plastic material comprising rotating mold.

Description

Rotary mold for the simultaneous injection of overmolded material parts

plastics.

  FIELD OF THE INVENTION The field of the invention is that of injection molding of plastics.

  More specifically, the invention relates to the field of multi-material molding for making parts and objects requiring the combination of at least two plastics having different properties and often complementary, both in terms of mechanical properties, and terms of aesthetic properties.

  The invention can of course also apply to the manufacture of mono material injected parts, whose complexity requires a superposition and / or assembly of a plurality of layers.

  The invention applies in particular, and without limitation, to any field requiring the manufacture of single-material, bi-material, tri-material, quad-material plastic parts, in particular the fields as varied as: automobile industry; the aviation industry; the toy industry; the supermarket industry; the DIY industry; the electricity and connector industry; the food packaging industry; the cosmetics industry; etc. 2. State of the art In the objective of manufacturing single or multi-material injected plastic parts and / or objects, a technique known from the prior art consists in using a two-part rotating mold. 25

  Such a mold makes it possible to produce the parts or objects by injecting a first material into a cavity assembly of a first end face of the mold. Once the first injection of the first material has been carried out, the mold is rotated 180 about an axis about which it is mounted, before the rear face of the mold comes to fit into a volume of predetermined shape, at a distance of inside which overmolding of the first injected material can be achieved by injection of a second plastic with predefined mechanical and / or aesthetic properties.

  As a purely illustrative and non-limiting example of a bi-material product that can be manufactured with such a mold, mention may be made of the body of a relatively hard plastic toothbrush, on which an overmolding of a second plastic material of characteristic promoting a relatively soft touch for the user of the toothbrush.

  A major disadvantage of this type of technique of the prior art is that it induces significant manufacturing costs.

  Indeed, such a mold according to the prior art almost doubles the molding cycle time, compared to a conventional mold.

  Another disadvantage of such a rotary mold according to the prior art concerns its limitation of the number of moldings, which leads to a limitation in terms of productivity, since the volumes of multi-material parts to produce are important.

  Another disadvantage of this type of mold according to the prior art is related to the fact that it is relatively expensive, since it requires the implementation of powerful and therefore often cumbersome means of closure of the press embedding this type of rotary mold , so as to compensate the injection pressure of the plastic material on one side of the mold.

  This type of rotary mold known from the prior art therefore goes against the current industrial constraints of productivity and cost reduction in the field of the manufacture of multi-material plastic injection parts and objects, which must besides being always more innovative in terms of association and / or combination of plastics to achieve new mechanical and / or aesthetic properties.

  3. OBJECTIVES OF THE INVENTION The invention particularly aims to overcome these various disadvantages of the state of the art.

  More specifically, an object of the invention is to provide a plastic injection molding technique that significantly reduces the price of the parts produced, regardless of the number of different plastic overmoldings to be made.

  Another object of the invention is to provide such a technique for simultaneously managing a large number of identical or different molding impressions, so as to promote greater productivity.

  A further object of the invention is to provide such a multi-material injection molding technique whose cycle time does not exceed that of conventional mono-material plastic injection molds.

  Yet another object of the invention is to provide a multi-material injection mold that is less expensive to manufacture than a rotary injection mold according to the prior art, since it does not require any specific closing power to counteract the pressures of injection.

  A final objective of the invention is to provide a multi-material injection mold which is simple to manufacture and implement, all remaining reduced cost in terms of operation and maintenance.

  4. SUMMARY OF THE INVENTION These objectives, as well as others which will become apparent later, are achieved according to the invention by means of a rotational mold for injection of plastic parts intended to equip a press ( 100) of plastic injection molding, comprising a plurality of moldings of predetermined shapes each corresponding to at least a portion of a molding and / or overmolding.

  According to the invention, such a mold advantageously comprises at least the following three parts (10, 12, 13): a first part (10) whose first face is mounted in contact with a first fixed plate (11) of the press Injection molding (100), the second face of which comprises a plurality of molding impressions connected to first means (104) for injecting at least a first plastic material of the molding press; a second portion (12) rotatably mounted along at least one axis (15) of rotation, on a frame (14) guided in motion (17) on at least two columns (16) of the press (100) molding; a third part (13) whose first face is mounted in contact with a second movable plate (18) of the injection molding press (100) and whose second face comprises a plurality of impressions (19) of molding connected to second means (105) for injecting at least a second plastic material of said molding press.

  Thus, in the closed position (20), at least the first and second plastics are injected simultaneously by the first (104) and second (105) injection means of said molding press (100), respectively.

  The invention is therefore part of a new and inventive approach to optimizing production and productivity, and reducing the unit cost of parts consisting of at least two plastics with different characteristics and / or properties, in the field of molding and overmolding by injection of plastics.

  The invention particularly relates to a mold and a plastic injection method advantageously for injecting several materials simultaneously or in offset injection, in a mold comprising from one to an indefinite number of molding impressions and / or overmolding, which may apply in a non-limiting way, to the injection of single-material injected parts, or even to bi-injection (bi-material), tri-injection (tri-material) or quadri-injection (quadri-material ).

  Preferably, the first part (10) comprises means for temperature regulation of the first injected plastic material. In addition, the first means (104) for injecting at least a first plastic material preferably consist of a plurality of injection nozzles of the first plastic material, at least in the molding cavities.

  Advantageously, the third portion (13) comprises means (102) for regulating the temperature of the second injected plastic material. In addition, the second means (105) for injecting at least one second plastic material of the molding press (100) advantageously consist of a plurality of injection nozzles for the second plastic material in the impressions (19). ), so as to easily perform overmolding.

  Advantageously, the first means (104) for injecting at least a first plastic material and the second means (105) for injecting at least a second plastic material are positioned on the upper part of the first (10) and third (13) parts.

  Preferably, the first part (10) further comprises plastic feed means of the third part (13) of the type belonging to the group comprising at least: insulated hot rod; at least one insulated hot runner; a hot block system; a set of electric hot nozzles; a set of open nozzles; a set of nozzles to shut off at least one injection point.

  Advantageously, the third part (13) comprises means for ejecting the molded and / or overmoulded part, the ejection means belonging to the group comprising at least: ejection means: o by thrust system passing through the third part (13); 25 o by upright sloping or inclined o by air; ejection means coupled to the injection press (100); at least one mechanical jack; at least one gas cylinder; a stripper; unscrewing means.

  The ejection means are advantageously positioned between the temperature control means (102) and the second movable platen (18) of the molding press (100).

  Preferably, the first (10) and third (13) parts further comprise at least one of the following elements belonging to the group comprising: sliders; rising wedges; some pins; snap-on cores; mechanical unscrewing; hydraulic unscrewing; electrical unscrewing; matrix passage locks.

  Also preferably, the second portion (12) comprises two identical faces respectively comprising a plurality of moldings (101) positioned positioned to complete the shapes of the indentations of each of the faces of the second (12) and third (13) ), and / or overmolding the already molded plastic inserts, when the press (100) is in position (20) closed.

  Advantageously, the frame (14) comprises moving guide means (17) collaborating with the press, the guide means belonging to the group comprising at least: a rack system; - a sliding system; a cylinder system; a hook system; roller skates; bronze skates.

  Also advantageously, these various means make it possible to efficiently and relatively simply support the movements of the plates and injection cores fitted to the molding press and / or overmoulding according to the invention. Advantageously, the second part ( 12) is controlled in rotation by a controlled electric motor (103), along at least one axis (15) of rotation belonging to the group comprising at least: - a vertical axis: a horizontal axis.

  Preferably, the second portion (12) also comprises means for regulating the temperature of the injected plastic material, the means being connected to the frame (14) of the injection press (100).

  The invention also relates advantageously to a press (100) injection mold molding and overmolding plastic parts, possibly of different type.

  According to the invention, such a press advantageously comprises at least one rotary mold for injection of plastic parts intended to equip a plastic injection molding press (100), the mold comprising a plurality of molding impressions of predetermined shapes. each corresponding to at least a part of a molding and / or overmolding part, and at least the following three parts (10, 12, 13): a first part (10) whose first face is mounted in contact with a first fixed platen (11) of the injection molding press (100), the second face of which comprises a plurality of molding cavities connected to first means (104) for injecting at least a first plastic material mold press; a second portion (12) rotatably mounted along at least one axis (15) of rotation, on a frame (14) guided in motion (17) on at least two columns (16) of the press (100) molding; a third portion (13) whose first face is mounted in contact with a second movable platen (18) of the injection molding press (100) and whose second face comprises a plurality of molding cavities (19) connected to second means (105) for injecting at least one second plastic material of the molding press; so that in position (20) closed, at least the first and second plastics are injected simultaneously by the first (104) and second (105) injection means of the molding press (100), respectively.

  Preferably, such an injection molding press comprises means for opening / closing the mold such that: in the open position (110, 300), the spaces (111, 301) are of dimensions allowing rotation (302) of the second part (12) of the mold, around at least one axis (303) of rotation passing through the frame (14); in the closed position (20), the closing power of the closing means is substantially zero, the injection pressures coming from the first (104) and second (105) injection means of the first (10) and third (13) parts canceling over a duration of an injection cycle time.

  Preferably, the opening / closing means equipping the press are of the type belonging to the group comprising: a rack and gear assembly; at least one electromagnet; at least one mechanical piston; at least one pneumatic piston; at least one hydraulic piston.

  Advantageously, the frame (14) of the press further comprises means (112, 21) for injecting plastic into the second portion (12) of the mold, which makes it possible, if necessary, to perform an overmoulding of a piece by means of a third plastic material, without increasing the injection cycle time, compared to a cycle time of a single-material injection, which further increases the economic attractiveness of a such invention.

  Finally, the invention also relates to an injection method for molding and / or overmolding plastic parts, possibly of different types.

  According to the invention, such a method advantageously employs a press (100) for injection molding and overmolding plastic parts comprising at least one rotary mold for injection of plastic parts, the mold comprising a plurality of molding impressions of predetermined shapes each corresponding to at least a part of a molding and / or overmolding part, and at least the following three parts (10, 12, 13): a first part (10), the first part (10) of which face is mounted in contact with a first fixed plate (11) of the injection molding press (100), and the second face of which comprises a plurality of molding cavities connected to first injection means (104). at least a first plastic material of the molding press; a second portion (12) rotatably mounted along at least one axis (15) of rotation, on a frame (14) guided in motion (17) on at least two columns (16) of the press (100) molding; a third portion (13) whose first face is mounted in contact with a second movable platen (18) of the injection molding press (100) and whose second face comprises a plurality of molding cavities (19) connected to second means (105) for injecting at least one second plastic material of the molding press.

  Such a method according to the invention also implements, and preferably, at least a first initialization step (40), and at least a second iterative step (41) of work.

  Advantageously, the initialization step (40) comprises at least the following sub-steps: closure (401) of the mold; injecting (402) the first plastic material through the first portion (11) and / or the second portion (12), such that the injected plastic inserts are held on the second portion (12) of the mold; opening (403) the mold to an open position (110) for rotating the second portion (12) of the mold; rotating (404) 180 degrees of the second portion (12) of the mold. Preferably, the second iterative step (415) step (41) of work comprises at least the following substeps: closure (410) of the mold; injecting (411) the first plastic material into the first portion (11) and the second plastic material into the third portion (13), such that the inserts made from the first plastic material in step (40) of initialization or injection sub-step (411) are overmoulded by the second plastic material on one of the faces of the second portion (12) and that new inserts made of the first plastic material are molded onto the another side of the second portion (12); opening (412) of the mold; withdrawing (413) overmoulded mold parts; rotating (414) 180 degrees of the second portion (12) of the mold.

  Preferably, the second step (41) iterative work is repeated a number of times substantially equal to the number of overmoulded parts to manufacture, until a step (420) end.

  The invention fits perfectly in a context of increasing the productivity of injection of single or multi-material parts, and reducing the cost of manufacturing such parts, and without increasing the cycle time. injection, compared to a molding method and / or overmolding injection mono material, according to the prior art.

  5. List of Figures Other features and advantages of the invention will appear more clearly on reading the following description of a preferred embodiment of the invention, given by way of illustrative and non-limiting example, made in reference to the accompanying drawings, in which: FIG. 1 is a view of all the parts of the rotary mold for injection of plastic parts according to the invention, and of the integration of these parts in an injection molding machine. open position; Figure 2 is a view of all parts of the rotary mold for injection of plastic parts according to the invention, and the integration of these parts in an injection press in the closed position; Figure 3 is a perspective view of the press according to the invention in the open position, the second part, so-called central rotational molding mold of plastic parts according to the invention being rotated; FIG. 4 presents a flowchart of the main steps of the molding and overmoulding process according to the invention.

  DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The present invention thus relates to a new multi-material injection mold for the production of molded products of one or more complementary plastic materials mechanically and / or ergonomically.

  By way of example of such products, mention may be made of a toothbrush whose structure is formed, most often, of a relatively hard or rigid plastic material, which is associated at least with a part of another material. Made of softer and more ergonomic plastic, to feel softer and anti-slip.

  Such a brush is necessarily made by means of an overmolding of the hard and / or rigid plastic structure, by injection of the second plastic material into a mold enclosing the insert of the structure of the toothbrush.

  The overmoulding techniques known from the prior art make it possible to achieve such a technical result, but practically double by two (for two-material molding) the molding cycle time, two successive injections being most often necessary.

  The undeniable advantage of the mold according to the invention advantageously makes it possible to considerably reduce the price of the parts produced by the large number of molding impressions and / or overmolding that it allows, while benefiting from an equivalent cycle time. to a conventional mold and a reduction in the number of mechanical parts necessary for the implementation and manufacture of the parts to be produced.

  Such a molding mold and / or overmolding injection of plastics material (s) according to the invention comprises at least three essential parts: a fixed plate side portion of the press receiving either punches or dies, and wherein one of the two materials is injected (as part of the production of bi-material parts); a central portion hinged about at least one axis of rotation rotating on itself and can be oriented 360. This part can receive either punches or molding dies; a movable side portion of the press also receiving either punches, or molding dies and / or overmolding in which is or is injected the second material.

  In terms of operation, the mold according to the invention is mounted on an injection press, in a manner substantially identical to that of a fixed or rotary injection mold.

  In a first phase of operation, the mold is closed in the molding position. The first material is injected on the insert side, at the fixed part and / or the movable part, and / or the central part, the choice being determined by the design of the mold and the injected part.

  It will be noted that advantageously in terms of ease of manufacture, the injected inserts remain on the rotating central portion of the mold, the objective being to facilitate the overmolding step of the bi-material part to be manufactured.

  In a second phase of operation subsequent to the first, the press opens with a gap necessary and sufficient for the rotatable central portion to pivot on at least one of its axes of rotation.

  The central portion carrying the inserts may be on the side of the movable part or the fixed part according to the initial design parameters of the mold.

  The first and second phases of operation jointly serve as an initialization phase for the molding of a large number of bi or multi-material plastic parts.

  In a third phase of operation, the press closes the mold and the two plastics are injected on either side of the rotating central part of the mold according to the invention. It is understood that an injection in offset time remains possible.

  A technical advantage of the invention is related to the fact that during simultaneous injection of the two plastics, the injection pressures on either side of the press are balanced, which avoids the implementation of means of strong closures of the press to compensate for the injection of plastic material when it is performed on only one of the injection face of the press, as in the known systems of the prior art.

  In a fourth phase of operation, the press opens releasing the mold, overmoulded parts are then ejected from the latter, before being taken by a robot, or by any other means of automatic or semi-automatic recovery. The parts located on the sides of the overmoulding inserts are maintained in position on the central part of the mold.

  In a fifth phase of operation and after a new closing of the press on the mold, the central part rotates around one of its axes of rotation.

  The molding and overmoulding cycle then resumes in the third phase and up to the fifth, and is then repeated as many times as necessary and on molding cycle rates in accordance with the specifications of the parts that are to be obtained. in manufacturing.

  In a possible variant of the multi-material injection mold, cold or hot control means, water and / or oil of all parts of the mold involved in the injection of molten plastic material. Such regulating means are implemented either by transfer on the central part through the frame (14) allowing the latter to be rotated, or directly on the mobile and central stationary fixed side parts. Any other thermal control means of the components of the mold and / or the molding press can of course be envisaged.

  Furthermore, various means of plastic injection can be envisaged at the press and the mold according to the invention, among which: hot block system with nozzles (with or without closure); sequential hot block system; direct injection with cold channels; three-plate motion injection; gas injection; -injection water.

  As regards the means for ejecting the mold of the manufactured parts, they may be of different types, depending, for example, on the specific features of the parts manufactured, in particular in terms of weight, size or volume: mechanical (press movement) hydraulic cylinder gas cylinder pneumatic cylinder stripper - unscrewing ejector / tubular / upright or inclined riser / air exhaust system / system from standard component suppliers.

  In addition, different movements in the mold can be envisaged to promote the molding and / or overmoulding of the parts to be manufactured, among which: slides (mechanical / hydraulic / pneumatic) upshifts (mechanical / hydraulic / pneumatic /) unscrewing (mechanical / hydraulic / pneumatic) lock system for removable cores.

  Means of control of the movements of the contactor type (eg telemechanical or commercial), magnetic detectors, may complete the assembly. 10

Claims (17)

  1. Rotary injection molding mold of plastic parts intended to equip a plastic injection molding press (100), comprising a plurality of molding impressions of predetermined shapes each corresponding to at least a part of a molding part and / or overmolding, characterized in that it comprises at least the following three parts (10, 12, 13): a first part (10) whose first face is mounted in contact with a first fixed plate (11) said injection molding press (100), the second face of which comprises a plurality of molding impressions connected to first means (104) for injecting at least a first plastic material of said molding press; a second portion (12) rotatably mounted along at least one axis (15) of rotation, on a frame (14) guided in motion (17) on at least two columns (16) of said molding press (100); a third portion (13) whose first face is mounted in contact with a second plate (18) movable from said injection molding press (100), and whose second face comprises a plurality of moldings (19) molding connected to second means (105) for injecting at least a second plastic material of said molding press; so that in position (20) closed, said at least first and second plastics are injected simultaneously by said first (104) and second (105) injection means of said molding press (100), respectively.   Rotary mold for injection of plastic parts according to claim 1, characterized in that said first part (10) comprises means for regulating the temperature of said first injected plastic material and in that said first means (104) injection of at least a first plastic material are constituted by a plurality of injection nozzles of said at least a first plastic material in said indentations.   3. Rotary injection molding mold of plastic parts according to any one of claims 1 and 2, characterized in that said third portion (13) comprises means (102) for temperature control of said second injected plastic material and said second means (105) for injecting at least one second plastic material of said molding press (100) comprises a plurality of injection nozzles of said second plastic material into said indentations (19), in order to perform an overmoulding.   Rotary mold for injection of plastic parts according to any one of claims 1 to 3, characterized in that said first means (104) for injecting at least a first plastic material and said second means (105). ) of injection of at least a second plastic material are positioned on the upper part of said first (10) and third (13) parts.   Rotary mold for injection of plastic parts according to any one of claims 1 to 4, characterized in that said first part (10) further comprises plastic supply means of said third part (13). ) of the type belonging to the group comprising: at least one insulated hot runner; a hot block system; a set of electric hot nozzles; a set of open nozzles; a set of nozzles to shut off at least one injection point.   6. Rotary injection molding mold of plastic parts according to any one of claims 3 to 5, characterized in that said third portion (13) comprises means for ejection of said molded part and / or overmoulded, said means ejection member belonging to the group comprising at least: ejection means: o thrust system passing through said third portion (13); o by straight up or inclined ascents o by air; ejection means coupled to said injection press (100); at least one mechanical jack; at least one gas cylinder; a stripper; unscrewing means; and in that said ejection means is positioned between said temperature control means (102) and said second movable platen (18) of said molding press (100).   Rotary mold for injection of plastic parts according to any one of claims 1 to 6, characterized in that said first (10) and third (13) parts furthermore comprise at least one of the following elements belonging to the group comprising: sliders; rising wedges; some pins; snap-on cores; mechanical unscrewing; hydraulic unscrewing; electrical unscrewing; matrix passage locks.   8. rotary mold for injection of plastic parts according to any one of claims 1 to 7, characterized in that said second portion (12) comprises two identical faces respectively comprising a plurality of moldings (101) positioned so as to complete the shapes of said indentations of each of the faces of said second (12) and third (13) parts, and / or to overwrap the plastic inserts already molded, when said press (100) is in position (20) closed.   9. rotary mold for injection of plastic parts according to any one of claims 1 to 8, characterized in that said frame (14) comprises moving guide means (17) collaborating with said press, said means of guidance belonging to the group comprising at least: a rack system; a sliding system; a cylinder system; a hook system; roller skates; bronze skates.   10. Rotary mold for injection of plastic parts according to any one of claims 1 to 9, characterized in that said second portion (12) is controlled in rotation by a motor (103) controlled electric, following at least one axis (15) of rotation belonging to the group comprising at least: a vertical axis; a horizontal axis.   11. Rotary mold for injection of plastic parts according to any one of claims 1 to 10, characterized in that said second portion (12) also comprises means for regulating the temperature of the injected plastic material, said means being connected to said frame (14) of said injection press (100).   12. Press (100) injection mold molding and overmolding plastic parts, possibly of different type, characterized in that it comprises at least one rotary mold for injection of plastic parts intended to equip a press ( 100), said mold comprising a plurality of moldings of predetermined shapes each corresponding to at least a part of a molding and / or overmolding part, and at least the three parts (10, 12). , 13): a first portion (10) whose first face is mounted in contact with a fixed first plate (11) of said injection molding press (100), and whose second face comprises a plurality of impressions moldings connected to first means (104) for injecting at least a first plastic material of said molding press; a second portion (12) rotatably mounted along at least one axis (15) of rotation, on a frame (14) guided in motion (17) on at least two columns (16) of said molding press (100); a third portion (13) whose first face is mounted in contact with a second plate (18) movable from said injection molding press (100), and whose second face comprises a plurality of moldings (19) molding connected to second means (105) for injecting at least a second plastic material of said molding press; so that in position (20) closed, said at least first and second plastics are injected simultaneously by said first (104) and second (105) injection means of said molding press (100), respectively.   13. press (100) injection mold molding and overmoulding of plastic parts, according to claim 12, characterized in that it comprises means for opening / closing said mold such that: in position (110, 300) open, the spaces (111, 301) are of dimensions allowing the rotation (302) of said second portion (12) of said mold, around at least one axis (303) of rotation passing through said frame (14); in the closed position (20), the closing power of said closing means is substantially zero, the injection pressures coming from said first (104) and second (105) injection means of said first (10) and third (13) parts canceling over a duration of an injection cycle time; said opening / closing means being of the type belonging to the group comprising: a rack and gear assembly; at least one electromagnet; at least one mechanical piston; at least one pneumatic piston; at least one hydraulic piston.   14. Injection molding press (100) composed of at least two plastics of different type, according to any one of claims 12 and 13, characterized in that said frame (14) further comprises means ( 112, 21) of plastic injection into said second portion (12) of said mold.   15. Injection method for molding and / or overmolding plastic parts, possibly of different type, characterized in that it implements a press (100) injection mold molding and overmoulding parts of materials plastic comprising at least one rotary mold for injection of plastic parts, said mold comprising a plurality of molding impressions of predetermined shapes each corresponding to at least a part of a molding and / or overmolding part, and to minus the following three parts (10, 12, 13): a first part (10) whose first face is mounted in contact with a fixed first plate (11) of said injection molding press (100), and whose second face comprises a plurality of molding impressions connected to first means (104) for injecting at least a first plastic material of said molding press; a second portion (12) rotatably mounted along at least one axis (15) of rotation, on a frame (14) guided in motion (17) on at least two columns (16) of said molding press (100); a third portion (13) whose first face is mounted in contact with a second plate (18) movable from said injection molding press (100), and whose second face comprises a plurality of moldings (19) molding connected to second means (105) for injecting at least a second plastic material of said molding press; and characterized in that it implements at least the following steps: a first initialization step (40); a second step (41) iterative work.   16. Injection method for molding and / or overmolding plastic parts according to claim 15, characterized in that said initialization step (40) comprises at least the following substeps: closure (401) said mold; injecting (402) said first plastic material through said first portion (11) and / or said second portion (12) such that the injected plastic inserts are held on said second portion (12) of said mold; opening (403) said mold to an open position (110) for rotating said second portion (12) of said mold; rotating (404) 180 degrees of said second portion (12) of said mold.   17. An injection method for molding and / or overmolding plastic parts according to any one of claims 15 and 16, characterized in that said second iterative step (415) step (41) of work comprises at least the following substeps: closing (410) said mold; injecting (411) said first plastic material into said first portion (11) and said second plastic material into said third portion (13), such that the inserts made of said first plastic material at said step (40) of said initialization or injection sub-step (411) is overmolded by said second plastic material on one side of said second portion (12) and new inserts of said first plastic material are molded onto the other face of said second portion (12); opening (412) of said mold; removing (413) said overmolded pieces from said mold; rotating (414) 180 degrees of said second portion (12) of said mold; and in that said second iterative step (41) of work is repeated a number of times substantially equal to the number of said overmolded pieces to be manufactured, until a step (420) of completion.