Molding tool assembly and method for powder injection molding of components

Abstract

The invention relates to a moulding tool assembly (5) for powder injection moulding of a component (1), a method for manufacturing a component (1), and a component obtainable by the method wherein the moulding tool assembly (5) comprises: i) at least a first and a second tool part (21, 22, 22a, 22b, 23, 24), the first tool part and the second tool part are arranged to define a mold cavity (25) for forming a component (1); ii) an inlet channel (30) for filling the mold cavity (25) with a molding material (3), the inlet channel (30) extending through an opening in the first tool part (21) to the mold cavity (25) and comprising an outlet end (33) having an outlet opening (34) for discharging the molding material (3) from the inlet channel (30) into the mold cavity (25); iii) a core pin (40) extending through an opening in the second tool portion (22, 22a, 22b), the core pin (40) being movable along a horizontal axis between a rear end position and a front end position, the horizontal axis extending through a center of the core pin (40) and a center of the inlet channel (30), the core pin (40) comprising an end portion (41), the end portion (41) has an end surface (42) facing the outlet opening (34); the core pin (40) is configured to seal the opening in the second tool portion (22, 22a, 22b) with the end portion (41) thereof when the core pin (40) is positioned in a rear end position; and wherein, when the core pin (40) is in its front end position, the core pin (40) is positioned such that the molding material (3) entering the molding cavity (25) impinges on the core pin (40); and iv) a power source (43) configured to maintain the core pin (40) in its front end position until a predetermined pressure threshold is exceeded during filling of the mold cavity (25), while moving the core pin (40) to the rear end position; or v) a power source (43) configured to hold the core pin (40) in its front end position for a predetermined time and to move the core pin (40) to the rear end position after the predetermined time.

Description

Technical Field

[0001] The present invention relates to a method for powder injection moulding of a component and a moulding tool assembly for use in the method. The invention also relates to a component obtainable by the method. Background Art

[0002] Powder injection molding (PIM) is a manufacturing technique in which a liquid compound, for example consisting of a polymer binder, metal carbide and a binder metal, is injected into a mold cavity of a molding tool component.

[0003] A common problem when manufacturing components using the PIM technique is the formation of defect structures that trap air present in the mold cavity, which can lead in particular to weld lines and / or internal porosity, which can ultimately lead to cracks after sintering. These problems have been solved to a certain extent by providing pores in the cavity through which the air present in the cavity is released. Nevertheless, problems related to weld lines and / or internal porosity in the manufactured components still exist. Therefore, the object of the present invention is to alleviate the problems of the prior art so as to eliminate or at least reduce the defects in the manufactured components, in particular in components without through holes. Therefore, the present invention aims to provide a method for alleviating these problems and an apparatus for performing the method. Summary of the invention

[0004] The present invention relates to a molding tool assembly for powder injection molding parts, comprising: i) at least a first tool part and a second tool part, said first tool part and said second tool part being arranged to define a mould cavity for forming a component; ii) an inlet channel for filling the mould cavity with moulding material, the inlet channel extending through an opening in the first tool part to the mould cavity and comprising an outlet end having an outlet opening for discharging the moulding material from the inlet channel into the mould cavity; iii) a core pin extending through an opening in the second tool portion, the core pin being movable between a rear end position and a front end position along a horizontal axis extending through a center of the core pin and a center of the inlet passage, the core pin including an end portion having an end surface facing the outlet opening; the core pin being constructed so that when the core pin is positioned in its rear end position, the core pin seals the opening in the second tool portion with its end portion; and wherein, when the core pin is in its front end position, the core pin is positioned so that molding material entering the mold cavity impinges on the core pin; and iv) a power source configured to maintain the core pin in its forward position until a predetermined pressure threshold is exceeded during filling of the mold cavity to move the core pin to the rearward position; or v) a power source configured to maintain the core pin in its front end position for a predetermined time and to move the core pin to the rear end position after the predetermined time.

[0005] The invention also relates to a molding tool assembly for a powder injection molded part, comprising: i) at least a first tool part and a second tool part, said first tool part and said second tool part being arranged to define a mould cavity for forming a component; ii) an inlet channel for filling the mould cavity with moulding material, the inlet channel extending through an opening in the first tool part to the mould cavity and comprising an outlet end having an outlet opening for discharging the moulding material from the inlet channel into the mould cavity; iii) a core pin extending through an opening in the second tool part, the core pin being movable between a rear end position and a front end position along a horizontal axis extending through a center of the core pin and a center of the inlet passage, the core pin including an end portion having an end surface facing the outlet opening; the core pin being configured to seal the opening in the second tool part with its end portion when the core pin is positioned in its rear end position; and wherein, when the core pin is in its front end position, the core pin is positioned such that: the end surface of the core pin is positioned at a distance of at most 20 mm from the outlet opening (34); and iv) a power source configured to maintain the core pin in its forward position until a predetermined pressure threshold is exceeded during filling of the mold cavity to move the core pin to its rearward position; or v) a power source configured to maintain the core pin in its front end position for a predetermined time and to move the core pin to its rear end position after the predetermined time; the molding tool assembly further comprising a control unit connected to the power source to control the power source.

[0006] According to one embodiment, the power source comprises hydraulic and / or pneumatic means, such as compressed air, and is configured to keep the core pin in its front end position until the pressure exerted by the discharged molding material during filling of the mold cavity reaches a range of 0.1 to 20 bar, such as 1 to 12 bar, preferably 5 to 10 bar, and more preferably 6 to 8 bar, which moves the core pin to the rear end position. The predetermined pressure threshold corresponds to the time period during which the core pin is kept in its front end position from the point in time when the molding material starts to fill the mold cavity.

[0007] According to one embodiment, the power source includes an electric device, which includes an electric servo motor, and the power source is constructed to: start from the time when the molding material starts to fill the mold cavity, the power source keeps the core pin in its front end position for a time period ranging from 0.001 to 0.5 seconds, preferably 0.01 to 0.25 seconds, and more preferably 0.05 to 0.15 seconds or 0.05 to 0.1 seconds.

[0008] According to one embodiment, the feed rate of the molding material into the mold cavity ranges from 1 to 70 cm 3 Molding material / second, for example 5 to 60, 5 to 55, 5 to 20 or 12 to 18 cm 3 Molding material / sec.

[0009] The expression "facing the outlet opening" means that the end surface of the core pin faces the outlet opening at least in its rear end position. In some embodiments, in the front end position of the core pin, the end surface of the core pin is positioned inside the inlet channel. Therefore, the expression "facing the outlet opening" includes such embodiments, wherein the end surface of the core pin is positioned inside the inlet channel when the core pin is in its front end position. Such an embodiment can be realized when the diameter of the core pin is smaller than the inner diameter of the inlet channel, so that the core pin (e.g., formed as a cylinder) can pass through the outlet opening of the outlet end of the inlet channel.

[0010] The present molding tool assembly allows the manufacture of high quality components without through holes, for example cutting tool inserts made of, for example, cemented carbide, ceramic or cermet and bonded metal. It has been found that the molding tool assembly can eliminate or at least reduce internal porosity and / or weld lines in the manufactured component by providing a more uniform flow of molding material into the mold cavity, compared to a molding tool assembly without a core pin struck by the molding material and said core pin subsequently retracted from its front position to the rear position.

[0011] The expression "impacts onto the core pin" means that the molding material discharged into the mold cavity directly impinges onto the end portion of the core pin, or the molding material impinges onto a molding material layer that has been formed on the end portion of the core pin.

[0012] According to one embodiment, the molding tool assembly comprises four tool parts, which are arranged to define a mold cavity. According to one embodiment, the molding tool assembly comprises two tool parts or three tool parts or five tool parts or more than five tool parts. In these embodiments, at least one of the tool parts is arranged in a movably manner so that the mold cavity can be opened and closed to allow removal of the formed component.

[0013] According to one embodiment, the second tool part consists of two tool halves. When the mould cavity is closed, the two tool halves of the second tool part together form the second tool part. Preferably, each of the two tool halves of the second tool part is provided with a peripheral recess, for example of semi-cylindrical shape, which together form an opening, preferably a cylindrical opening, through which the core pin can extend when the two tool halves are combined.

[0014] According to one embodiment, the inlet channel may protrude into the mould cavity by up to 10% of the distance between the outlet opening and the end surface of the core pin when the core pin is positioned in its rear end position. Preferably, however, the outlet opening is flush with the inner surface of the first tool part facing the mould cavity so that the inlet channel does not protrude into the mould cavity.

[0015] According to one embodiment, the molding material comprises: hard particles selected from at least one of WC, TiC, TiN and / or TiCN and a binder metal preferably selected from Co and / or Fe and / or Ni; and a polymer binder.

[0016] According to one embodiment, the power source used herein comprises electric means, hydraulic means and / or pneumatic means. Preferably, the power source comprises an electric servomotor.

[0017] The term "servomotor" as used herein refers in particular to a power source for driving the movement of the core pin. The servomotor is preferably connected to a control unit programmed to command the servomotor to move the core pin to a commanded rear end position and a front end position at a predetermined time point at a predetermined speed. Therefore, the molding tool assembly preferably further comprises a control unit connected to the power source for controlling the power source.

[0018] The "predetermined time" and the "predetermined pressure threshold" for holding the core pin in its front end position before moving it to the rear end position can be determined by performing tests, for example in a transparent mold cavity, before executing the method for manufacturing a component, in which the impact can be studied as a function of the distance between the end surface of the core pin and the outlet opening for a given feed rate of the molding material as disclosed herein. The flow behavior of the molding material can be studied with the aid of a high-speed camera (which is capable of capturing moving images with an exposure of less than 1 / 1000 second). Therefore, the front end position of the core pin can be varied by increasing the distance from the (minimum) distance (the distance at which the impact occurs) to determine the maximum distance at which the impact still occurs at a given feed rate of the molding material into the mold cavity. For a given position of the core pin in its front end position (in which the impact occurs), the point in time at which the retraction of the core pin can be started can be determined from the volume of the mold cavity occupied by the molding material when the flow front impacts on the end surface of the core pin and the feed rate of the molding material. Thus, as the flow front of the molding material strikes the end surface of the core pin, the portion of the volume in the mold cavity that is filled with the molding material at a given feed rate corresponds to a certain period of time that elapses before the retraction begins. In addition, since the volume of the entire mold cavity is also known, the portion that has not been filled at the start of the retraction of the core pin can be determined by subtracting the filled volume from the entire volume of the mold cavity. Thus, the time period for completing the entire filling can be determined, and thus the time period required for the core pin to have completed its retraction before the filling is completed. For example, if the end surface of the core pin is positioned so that the core pin is struck when 50% of the mold cavity has been filled, if the feed rate is constant, the time taken to fill the remaining portion (50% of the volume) will be the same as the filled volume. Therefore, by controlling the feed rate, the propagation of the flow front in the mold cavity (and the volume occupied by the molding material) over time is controlled. The speed of the core pin can be set so that the core pin retracts at a rate that keeps the flow front of the molding material in contact with the end surface of the core pin.

[0019] Where an electric device is used as the power source, the electric servomotor must, of course, be selected to resist the initial build-up of pressure as the molding material enters the mold cavity until the point in time when the core pin is retracted.

[0020] Servo motors, such as electric servomotors, are generally known to drive various mechanisms in molding tool assemblies, such as drive mechanisms for screws (screw plungers), etc. Servo motors are generally well known and are described in, for example, US 4,785,221, US 4,540,359, US 9,475,224 and DE 1 995 9739.

[0021] The electric servomotor enables the movement of the core pin to be precisely controlled and independent of the pressure within the mold cavity, which can vary during cavity filling.

[0022] According to one embodiment, the electric device comprises an electric servomotor, and the control unit is configured to control the electric servomotor to: i) before starting to fill the mold cavity, move the core pin to its front position; ii) after filling has commenced, while the cavity is being filled, retracting the core pin from its forward position to its rearward position; iii) Before filling is completed, position the core pin in its rear end position.

[0023] According to one embodiment, the power source comprises a pneumatic device, such as compressed air. Compressed air can be used to move the core pin and maintain the core pin in its front end position by pressing the rear end of the core pin opposite to the outlet opening along the horizontal axis towards the outlet opening at a predetermined pressure. For example, compressed air can be applied to the rear end of the core pin via a hose or other conduit with an appropriate connection device, such as a nipple screwed into a hole at the center of the rear end of the core pin. A valve can be used to adjust the pressure applied to the rear end of the core pin. The degree of pressure applied to the rear end of the core pin will determine the pressure threshold at which the core pin is pressed back to the rear end position by the pressure applied by the molding material entering the mold cavity. The higher the degree of compressed air applied, the longer the delay before reaching the pressure threshold. Therefore, the pressure of the applied compressed air can be used to control the time point at which the core pin should begin its retraction to the rear end position. Preferably, a further valve (such as an adjustable needle valve) can be arranged to the hose or other conduit to discharge the trapped compressed air when the core pin is retracted after the pressure threshold has been exceeded in the mold cavity. Since the adjustable valve can be adjusted to discharge compressed air to different degrees, the retraction speed of the core pin can be controlled by the valve. A lower degree of compressed air discharge will result in a slower retraction of the core pin, while a higher degree of compressed air discharge will allow a faster retraction of the core pin. Preferably, the speed of retraction of the core pin is selected so that the end portion of the core pin remains in contact with the flow front of the molding material throughout the retraction of the core pin.

[0024] Preferably, the inlet channel extends centrally through the opening in the first tool part.Thereby, the mould cavity can be filled more evenly.

[0025] Preferably, the core pin extends centrally through the opening in the second tool part.

[0026] According to one embodiment, the end surface of the core pin has a flat, centrally protruding or centrally concave shape.The shape of the end surface of the core pin will affect the shape of the manufactured component.

[0027] According to one embodiment, when the core pin is in its rear end position, the end surface of the core pin is flush with the second tool part. In the case of a recessed or protruding end surface, the periphery of the end surface of the core pin is preferably flush with the surrounding surface of the second tool part.

[0028] The recessed or protruding end surface may extend axially up to about 0.1 mm or up to 0.3 mm or up to 0.5 mm or up to 1 mm along the horizontal axis of the core pin. In these embodiments, the recessed or protruding surface constitutes a limited portion of the total length of the core pin, considering that the core pin may extend within the mold cavity, for example, by at least 10 mm or at least 15 mm or up to, for example, 20 mm, depending on the volume of the mold cavity.

[0029] According to one embodiment, the cross-section of the core pin is circular, square, triangular, elliptical or oval, preferably circular or elliptical, and most preferably circular.

[0030] According to one embodiment, the core pin has a constant cross section at least over its entire axial extension within the mould cavity.

[0031] According to one embodiment, the core pin has a rear end outside the mold cavity facing away from the outlet opening, the rear end having a larger cross section than a portion of the core pin extending in the mold cavity.

[0032] According to one embodiment, a mechanical stopper is arranged outside the mold cavity to prevent the core pin from moving beyond its front and rear positions. The mechanical stopper can, for example, be arranged to mechanically contact and stop the rear end of the core pin, the rear end of the core pin having a larger cross-section than the rest of the core pin.

[0033] According to one embodiment, the core pin has a cylindrical cross section over its entire length.According to one embodiment, the core pin has a diameter in the range of 2 to 14 mm, such as 3 to 9 mm or 7 to 9 mm, at least along its extension in the mould cavity.

[0034] According to one embodiment, the inlet channel is cylindrical. According to one embodiment, the outlet opening is circular and has a diameter in the range of 1 to 12 mm, for example 3 to 6 mm or 7 to 9 mm. The area of ​​the outlet opening is appropriately selected, in particular based on the volume of the mold cavity to be filled.

[0035] According to one embodiment, the ratio of the area of ​​the end surface of the core pin to the area of ​​the outlet opening is in the range of 1.5:1 to 1:1.5, preferably from 0.8:1 to 1:0.8, and more preferably from 0.9:1 to 1:0.9. The area ratio of the end surface specified here provides a preferred impact condition and contributes to a uniform flow of the molding material in the mold cavity.

[0036] The mold cavity can have any suitable geometric shape. For example, the mold cavity can have the shape of a blade for making a drill tip, a milling tip or any other suitable design. However, the maximum size of the formed part is limited by the cooling and solidification properties of the molded material. Large volumes may cause cracks during the solidification process. As the size of the part to be formed increases, the possibility of crack formation also increases. Therefore, the volume of the mold cavity is preferably 50cm 3 or smaller, for example 40cm 3 The minimum volume of the mold cavity is set by the size requirements of the part, and thus the volume can be from, for example, 0.05 to 50 cm 3 Preferably, the diameter of the component manufactured by the method described herein is up to 40 mm, such as up to 30 mm or up to 20 mm or up to 15 mm, such as up to 10 mm, for example from 3 to 40 mm, or from 3 to 30 mm, or for example from 5 to 10 mm.

[0037] According to one embodiment, the molding tool assembly is used in a cold channel system or a hot channel system. A hot channel system generally includes a heated runner or manifold connected to an inlet channel. In a hot channel system, the molding tool may include several mold cavities (defined by several tool parts), wherein each mold cavity is supplied with molding material from a separate inlet channel.

[0038] As further defined herein, the present invention also relates to a method of manufacturing a component in a molding tool assembly by powder injection molding, the method comprising: i) positioning the core pin in its front end position, where the end surface of the core pin is located at most 20 mm from the outlet opening, where the molding material entering the mold cavity impinges on the core pin; ii) filling the mold cavity with molding material discharged through the outlet opening of the inlet channel; iii) retracting the core pin from the front end position to its rear end position at a speed such that the retraction of the core pin from the front end position is completed before the filling of the mold cavity is completed.

[0039] The invention also relates to a method for manufacturing a component in a molding tool assembly by powder injection molding, the method comprising: i) positioning the core pin in its front end position by means of a power source, in which position the end surface of the core pin is positioned at most 20 mm from the outlet opening; ii) filling the mold cavity with molding material discharged through the outlet opening of the inlet channel; iii) retracting the core pin from the front position to the rear position with the aid of a power source at a speed such that the core pin is retracted before the filling of the mold cavity is completed; The power source includes: i) a hydraulic device and / or a pneumatic device configured to hold the core pin in its forward position until a pressure ranging from 0.1 to 20 bar is reached during filling of the mould cavity, causing the core pin to move to the rearward position; or ii) an electric device including an electric servomotor configured to: the power source maintain the core pin in its forward position for a period of time ranging from 0.001 to 0.5 seconds from the point in time when the molding material begins to fill the mold cavity; The molding tool assembly further comprises a control unit connected to the power source for controlling the power source.

[0040] Preferably, the power source is controlled by the control unit to move the core pin from the rear end position to the front end position and from the front end position to the rear end position.

[0041] Step i) of the method may be performed before or after the start of discharging the molding material into the mold cavity, as long as the core pin is positioned in its front end position before the molding material impinges on the core pin in its front end position.

[0042] Because the molding material impinges upon the core pin as it enters the mold cavity, a more uniform flow can be achieved. Thus, the elimination or reduction of defects such as internal porosity and weld lines can be achieved. By completing the retraction of the core pin before filling is complete, the manufactured part will not exhibit any holes or cavities formed due to the core pin not being retracted in time before the part begins to solidify.

[0043] According to one embodiment, the method further comprises: retracting the core pin at a speed such that the end portion of the core pin remains in contact with the flow front of the molding material throughout the entire process of retracting from the front position to the rear position. It has been found that this can achieve an even more uniform filling of the mold cavity, which thereby further reduces or eliminates the formation of weld lines and / or internal pores in the manufactured parts.

[0044] As the molding material flows in the direction that retracts the core pin, its linear flow may vary depending on the shape of the mold cavity. For example, a mold cavity defining a tapered shape extending along a horizontal axis will result in an increase or decrease in the linear flow rate. 3 / second) is preferably kept constant, so it is preferred that the speed of the core pin is adjusted so that the end portion of the core pin and the flow front of the molding material remain in contact during the entire filling process. Thus, for example, when the section of the mold cavity extending along the horizontal axis is larger than other sections of the mold cavity, a lower retraction speed of the core pin is used to keep the end portion of the core pin in contact with the flow front also in this larger section.

[0045] According to one embodiment, the method comprises: moving the core pin by means of an electric servomotor, the electric servomotor being connected to a control unit which controls the electric servomotor. Thereby, the control unit can be programmed to move the core pin by commanding the electric servomotor to move the core pin accordingly. Precise and accurate control of the movement of the core pin and the speed of movement of the core pin will impart even fewer defects and thus lead to the manufacture of improved components.

[0046] According to one embodiment, as further disclosed herein, the method comprises controlling a power source by a control unit, the power source comprising a hydraulic device and / or a pneumatic device, such as compressed air. According to one embodiment, the method comprises moving the core pin by means of compressed air as a power source, preferably in combination with a control unit that controls the degree of compressed air applied to the core pin. Thus, the control unit can be programmed to apply compressed air to the core pin to move the core pin to its front end position. The core pin comprises a rear end facing away from the outlet opening, and the compressed air is preferably applied to the rear end of the core pin at a certain pressure, which is in the range of from 0.1 to 20 bar, for example 1 to 12 bar or 4 to 12 bar or 6 to 8 bar. The pressure corresponds to a predetermined pressure threshold further described herein. The pressure of the compressed air applied to the rear end of the core pin affects the time point of exceeding the threshold pressure, at which the core pin is pressed back to its rear end position by the incoming molding material. The higher pressure applied by the compressed air results in a more delayed retraction of the core pin. Preferably, as further described herein, a valve is arranged for controlling the pressure that presses the core pin to its front end position. The control including the opening and closing of the valve may be performed by a control unit, such as a main control unit that further controls other functions of the molding tool assembly. In such an embodiment, the control unit may be programmed to: when compressed air is to be supplied to the rear end of the core pin, the control unit opens the valve; and when molding material enters the mold cavity, the control unit closes the valve.

[0047] When the core pin begins to retract, the compressed air applied to the rear end of the core pin is preferably exhausted. The compressed air can be exhausted to varying degrees by means of an adjustable valve further described herein. The degree of exhausting the air can be used to adjust the speed of the core pin so that the end portion of the core pin remains in contact with the flow front of the molding material and the core pin reaches its rear end position at a point in time before the filling of the mold cavity has been completed.

[0048] According to one embodiment, step iii) of the method comprises: completing the retraction of the core pin to its rear end position up to 0.1 seconds or up to 0.05 seconds or up to 0.01 seconds before completing the filling of the mold cavity. Preferably, the retraction of the core pin is completed at least 0.005 seconds before the filling of the mold cavity is completed, for example 0.01 seconds before the filling is completed. Preferably, the completion of the retraction is selected to shorten the production cycle as much as possible, while having a short margin before the filling is completed.

[0049] According to one embodiment, the filling of the mold cavity is completed within 5 seconds, such as within 4 seconds or 3 seconds, such as within 1 second, such as within 0.1 to 1 second, or within 0.1 to 0.35 seconds. The filling time also depends to a large extent on the volume of the mold cavity. Preferably, the filling rate of the mold cavity is kept constant by the main control unit.

[0050] According to one embodiment, step iii) of the method comprises: completing the retraction of the core pin to its rear end position after at least 80% or at least 95% or at least 99% of the volume of the mold cavity has been filled and before the filling is completed. It can be clearly seen from the disclosure of this article that before executing the method, that is, before starting production, the time period for completing the filling of the mold cavity can be calculated in advance based on the knowledge of the volume of the mold cavity and the filling rate used. For example, 80% filling of the volume of the mold cavity can be easily calculated thereby. In one embodiment, sensors that monitor the degree of filling can also be used to control the filling.

[0051] According to one embodiment, the ratio of the time of retraction of the core pin from its front end position to its rear end position to the filling time is 80:100 to 99:100, such as 90:100 to 199:100, or 95:100 to 99:100.

[0052] According to one embodiment, step i) of the method comprises positioning the core pin in its front end position at a predetermined distance d, said predetermined distance d being up to 60% of the total distance between the outlet opening and the end surface of the core pin when the core pin is positioned in its rear end position. According to one embodiment, when the core pin is positioned in its rear end position, i.e. when the end surface of the core pin is flush with the inner surface of the second tool part, said distance d is up to 50% or up to 40% or up to 30% or up to 20% or up to 10% or up to 5% or up to 3% or up to 1% of the distance between the outlet opening and the end surface of the core pin. Preferably, when the core pin is positioned in its rear end position, i.e. when the end surface of the core pin is flush with the inner surface of the second tool part, said distance d is at least 1% of the distance between the outlet opening and the end surface.

[0053] The predetermined distance d is measured from a point on the end surface of the core pin when the core pin is positioned at its front end position to a point on the outlet opening, where the point is intersected by a horizontal axis extending through the center of the core pin and the center of the inlet passage (e.g. Figure 4a-4c as further shown).

[0054] According to one embodiment, the predetermined distance d ranges from 1 mm to 20 mm, such as from 1 mm to 15 mm, such as from 1 mm to 10 mm, preferably from 1 mm to 5 mm or from 1 mm to 2 mm.

[0055] According to one embodiment, the core pin is positioned in its front end position so that the end surface of the core pin is positioned 1 mm to 20 mm from the outlet opening, for example 1 mm to 15 mm from the outlet opening, for example 1 mm to 10 mm from the outlet opening, preferably 1 mm to 5 mm or 1 mm to 2 mm from the outlet opening.

[0056] The predetermined distance d is selected before starting to manufacture the component, and the selection of the predetermined distance d can be based on several tests, for example, carried out in a transparent mold cavity, in which the flow behavior of the molding material at different distances d can be studied, for example with the help of a high-speed camera capable of capturing moving images with an exposure time of less than 1 / 1000 second. Thereby, the point in time at which the molding material hits the core pin can be easily observed. If, for example, the distance d is too long, irregular filling occurs, resulting in air inclusions, weld lines and / or air-filled internal pores. In this case, shorter distances d can be tested to study the impact behavior. In addition, the quality of the obtained component can also be analyzed. With the help of, for example, a microscope (such as an optical microscope), the presence of weld lines is easily detected. In addition, in these tests, by studying the flow of the molding material and the filling of the mold cavity, the retraction speed of the core pin can be configured so that the end portion of the core pin remains in contact with the flow front of the molding material. According to one embodiment, a sensor can be positioned on the core pin to detect a pulse when the front of the molding material hits the core pin.

[0057] According to one embodiment, after the steps of the method described herein, the component is cooled and solidified in the mold cavity for a predetermined period of time and then removed from the mold cavity after the mold cavity is opened. According to one embodiment, in a subsequent step, the component is suitably debonded and sintered in a conventional manner known in the art. Sintering can be performed by placing the component in a sintering furnace, which is generally heated to a temperature above the melting point of the binder metal in the component, but below the melting point of the hard particles. After sintering, the component preferably consists of the remaining cemented carbide, ceramic or cermet; and binder metal, and can be recovered as a final product.

[0058] The invention also relates to a component obtainable by the method described herein, which component is a cutting insert without through holes and without weld lines, comprising cemented carbide, ceramic or cermet. Examples of cutting inserts include drill tips, milling tips, indexable inserts, or other types of cutting inserts without through holes and without weld lines and comprising cemented carbide, ceramic or cermet. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 A schematic diagram of a molding tool assembly is shown.

[0060] Figure 2aA schematic diagram of a molding tool assembly is shown with the core pin in its forward position. Figure 2b A schematic diagram of a molding tool assembly is shown with the positions of a core pin on its way to its rear and front positions, respectively, according to the indicated arrows. Figure 2c A schematic diagram of a molding tool assembly is shown with the core pin in its rear end position.

[0061] Figure 3a-3d A schematic diagram of a molding tool assembly is shown, wherein the core pin is positioned in the rear end position ( Figure 3a ), the core pin is on its way to the front position ( Figure 3b ), the core pin is positioned at its front end position ( Figure 3c ), and the core pin on its way to its rear end position ( Figure 3d ).

[0062] Figure 4a-4c A schematic diagram showing an embodiment of an end surface of a core pin and an outlet opening of an inlet channel.

[0063] Figure 5a and 5b An embodiment illustrating the movement of the core pin between its respective end positions is shown from a side view and a perspective view.

[0064] Figure 6a A schematic diagram of a core pin controlled by compressed air as a power source and a mechanical stop preventing the core pin from moving beyond its end position is shown. Figure 6b A detail view showing compressed air being applied to the rear end of the core pin.

[0065] Figure 7a and 7b They respectively show that by Figure 7a ) and without removable core pin ( Figure 7b ) is a green body (component) obtained by performing the method in a molding tool assembly.

[0066] Figure 8 A flow chart showing the main steps for manufacturing a component according to the invention. DETAILED DESCRIPTION

[0067] Figure 1 A molding tool assembly 5 is schematically shown, comprising an inlet channel 30 for a molding material 3, wherein the molding material 3 is supplied to the inlet channel 30 via an injection unit 10 and a hopper 11 receiving the molding material 3. The molding material 3 is a compound or feedstock, such as a carbide, nitride and / or carbonitride; a binder metal and a polymer binder.

[0068] In the pre-treatment step performed before discharging the molding material 3 into the mold cavity 25 according to the present invention, the molding material 3 is supplied in a molten form via the heated cylinder 12, which melts the polymer binder in the molding material 3 so that the molding material 3 forms a liquid slurry. A spiral plunger (commonly referred to as a screw) 13 is arranged in the cylinder 12 to mix and feed the molding material 3 in the cylinder 12 and force the molding material to be discharged from the cylinder 12 by axially moving through the nozzle 14 of the injection unit 10.

[0069] The molding tool assembly 5 includes a first tool portion 21 and a second tool portion 22 arranged opposite to each other. The molding tool assembly 5 also includes a third tool portion 23 and a fourth tool portion 24, which are also arranged opposite to each other to define a mold cavity 25 together with the first tool portion 21 and the second tool portion 22. The tool portions 21, 22, 23 and 24 are arranged to allow the mold cavity 25 to be opened and closed. The second tool portion 22 can be moved toward and away from the mold cavity 25 in the axial direction (in the Figure 1 The third tool part 23 and the fourth tool part 24 are arranged to be able to move towards and away from each other (in Figure 1 The molding tool assembly 5 further comprises a movable pressing plate 26 holding the second movable tool part 22 and a stationary pressing plate 27 holding the first tool part 21 stationary.

[0070] Movable core pin 40 ( Figure 1 The inlet channel 30 extends through an opening in the first tool part 21 into the mold cavity 25. The inlet channel 30 has an inlet opening 32 which is in fluid communication with the nozzle 14 of the injection unit 10.

[0071] A portion of the inlet channel 30 is tapered so that it narrows in a direction from the outlet opening 34 to the inlet opening 32. The inlet channel 30 has an outlet end 33 having an outlet opening 34 for discharging the molding material 3 into the mold cavity 25. The center of the core pin 40 is horizontally aligned with the center of the inlet channel 30.

[0072] Figures 2a to 2c The core pin 40 is shown in its front end position ( Figure 2a ), the position of the core pin 40 on the way to its front end position and rear end position ( Figure 2b ) and the core pin 40 at its rear end position ( Figure 2c ). Figure 2aIn FIG. 4 , the distance d between the end surface 42 of the core pin 40 and the outlet opening 34 is indicated when the core pin 40 is in its front end position. Figure 2c In the middle, the end surface 42 is flush with the inner surface of the second tool part 22. In the rear end position ( Figure 2c ), the end portion 41 of the core pin 40 seals the opening in the second tool part 22 through which the core pin 40 extends. Figures 2a to 2c , a horizontal center axis X extends through the center of the mold cavity 25 , the center of the core pin 40 , and the center of the inlet passage 30 .

[0073] Figure 3a-3d The core pin 40 is shown in its rear end position ( Figure 3a ), the core pin 40 is on its way to its front end position ( Figure 3b ), the core pin 40 is positioned at its front end position ( Figure 3c ), and the core pin 40 is on its way to its rear end position ( Figure 3d ).exist Figures 3a to 3d In the embodiment shown in FIG. 1 , the cross section of the core pin 40 is larger than the outlet opening 34 .

[0074] Figure 4a A core pin 40 is shown having a flat end surface 42 . Figure 4b A core pin 40 is shown having a concave end surface 42 . Figure 4c A core pin 40 is shown having a raised end surface 42 .

[0075] The distance d between the end surface 42 of the core pin 40 and the outlet opening 34 is defined as the distance between the point on the end surface 42 of the core pin 40 that intersects the horizontal center axis and the point on the outlet opening 34 that intersects the horizontal center axis, as Figure 4a-4c shown.

[0076] Figure 5a A control unit 51 is shown connected to the electric servomotor 43. The control unit 51 is programmed to instruct the electric servomotor 43 to rotate the ball screw 50. The electric servomotor 43 is equipped with a gearbox 46 which transmits the rotation of the servomotor 43 to the ball screw 50 via the shaft 43a. As the ball screw 50 rotates, the nut 56 will rotate and follow the ball screw thread 64 of the ball screw 50 and thereby move up or down along the axial extension of the ball screw 50 depending on the direction of rotation of the ball screw 50 controlled via the control unit 51 and the gearbox 46 of the electric servomotor 43. As the nuts 56 rotate along the ball screw 50, they will cause the crossbar 60 to move up or down along the ball screw 50, as shown in FIG. Figure 5b The crossbar 60 is fixed to the track 45a by means of screws 65 and is further connected to the ball screw 50 via nuts 56. Figure 5aAlso shown is a core pin plate 44 to which the core pin 40 is attached. The core pin plate 44 is provided with an attachment device 55, which is provided with a rounded retainer 55a, such as Figure 5b As further shown, the segment 53 including the core pin 40 is fixedly attached to the core pin plate 44 by means of screws 71 .

[0077] The core pin 40 is provided with a rear end 48 having a larger diameter than the rest of the core pin 40, which prevents the core pin 40 from moving away from the section 53. The guide bearing 55b is mounted in the groove 45 of the track 45a and is further fixed to the rounded retainer 55a of the attachment device 55, as shown in FIG. Figure 5b As shown. The groove 45 is angled (acute angle) with the vertical plane. When the rotating ball screw 50 moves the cross bar 60 upward or downward, the position of the guide bearing 55b in the groove 45 will change. Because the groove 45 is angled with the vertical plane, when the cross bar 60 and the track 45a are displaced upward or downward, the attachment device 55 and the core pin plate 44 to which the attachment device 55 is attached will move toward or away from the mold cavity 25 along the horizontal axis in a direction perpendicular to the vertical plane of the core pin plate 44. The downward movement of the cross bar 60 will press the attachment device 55, the core pin plate 44 and the core pin 40 away from the mold cavity 25 (towards the rear end position), and the upward movement will cause the attachment device 55, the core pin plate 44 and the core pin 40 to move toward the mold cavity 25 (towards the front end position). The design is arranged so that the horizontal displacement of the core pin plate 44 corresponds to the movement of the core pin 40 between its rear end position and the front end position. Figure 5a In the embodiment, a guide rod 70 is also provided for guiding the movement of the core pin plate 44.

[0078] Figure 5a Further shown is a tool part 22, which together with the tool part 21 defines a mould cavity 25. The movement of the tool part 22 is controlled by a main control unit 61 via a plate 52. The main control unit 61 is connected to the control unit 51 to establish a two-way communication between the control unit 51 and the main control unit 61, which further controls various control and regulation functions in the moulding tool assembly 5, including, for example, moving the plate 52 equipped with means suitable for opening and closing the mould cavity 25 by controlling the tool part 22, controlling the screw plunger 13 to feed the moulding material 3 to the mould cavity 25, etc. in a conventional manner known in the art.

[0079] exist Figure 6a, the core pin 40 is located at its rear end position. Mechanical stops 49 are provided on either side of the rear end 48 of the core pin 40. The diameter of the rear end 48 is larger than the rest of the core pin 40. The rear end 48 of the core pin 40 is able to move axially in the cylinder space 66 of the insertion element 67. The mechanical stop 49 prevents the rear end 48 from moving beyond the mechanical stop 49, thereby preventing the end surface 42 of the core pin 40 from moving beyond the rear end position and the front end position of the core pin 40. The tool portion 21 and the tool portion 22 including the tool halves 22a and 22b are also indicated.

[0080] exist Figure 6a and 6b , compressed air is schematically shown as the power source 43. A two-way valve 62 positioned along a gas line 57 (hose) is controlled by a main control unit 61 so that the valve 62 opens when the mold cavity 25 is closed, and closes when the filling of the molding material 3 is completed. The hose 57 is connected to a nipple 58 at one end, and to the valve 62 at the other end thereof. The nipple 58 is connected at the other end thereof to a central threaded hole 59 in the rear end 48 of the core pin 40.

[0081] When the rear end 48 of the core pin 40 is exposed to the compressed air, the core pin 40 is pressed to its front end position. When the molding material 3 subsequently enters the mold cavity 25, the core pin 40 will begin to retract when the threshold pressure is exceeded, thereby pushing the core pin 40 back to its rear end position. As the core pin 40 retracts, the compressed air trapped in the hose 57 is exhausted via the adjustable needle valve 63, which is at least partially opened to enable the exhaust. By adjusting the needle valve 63, the degree of exhaust of the trapped air is controlled, and therefore the speed of the retracting core pin 40 is controlled to maintain contact between the end portion 41 of the core pin 40 and the flow front of the molding material.

[0082] Figure 7b A green body produced in a moulding tool assembly 5 without a moving core pin 40 is shown, in which a weld line 47 has been formed. Figure 7a A green body produced in a molding tool assembly 5 with a moving core pin 40 according to the invention is shown, in which green body there is no weld line.

[0083] The following describes how the molding tool assembly 5 may operate, as follows: Figure 8 As further illustrated in the flowchart: 1) In a first step, the openable mold cavity 25 of the molding tool assembly is opened, and the core pin 40 is moved from its rear end position to its front end position. The core pin 40 is connected to a power source 43, which may be an electric servomotor 43 that drives the core pin 40 to move. The electric servomotor 43 is controlled by a control unit 51, which is programmed to move the core pin 40 according to a command from the control unit 51. 2) In a second step, the main control unit 61 closes the molding tool 20 of the molding tool assembly 5. The main control unit 61 is programmed to control all operations in the injection molding assembly 5, except for the core pin 40 which is controlled by the control unit 51. An alternative way to control all operations of the injection molding assembly 5 is a main control unit 61 as described herein, which also controls the core pin 40, for example by integrating the control unit 51 therein. In the embodiment described herein, the control unit 51 is connected to the main control unit 61, and the control unit allows two-way communication. 3) In the third step, when the core pin 40 has moved to its front end position and thus executes the command from the control unit 51, the electric servomotor 43 sends a clear signal to the control unit 51. The clear signal is then forwarded from the control unit 51 to the main control unit 61, after which the main control unit 60 sends a signal to start the filling of the cavity 25. Then, a trigger signal is sent from the main control unit 61 to the control unit 51, so that the filling of the cavity 25 has been started. When the filling starts, the control unit 51, which is programmed to control the core pin 40 via the electric servomotor 43, controls the core pin to retract from its front end position to its rear end position. The main control unit 61 is programmed to fill the cavity 25 with the molding material 3 at a predetermined flow rate. Since the volume of the cavity 25 has been determined and the predetermined flow rate of the molding material 3 has been programmed in the main control unit 61, the time required to fill the cavity 25 is used to program the control unit 51 so that the core pin 40 retracts before the cavity 25 is completely filled. Therefore, the control unit 51 sends a signal to the electric servomotor 43 to move the core pin 40 at a predetermined time point and at a speed that allows the core pin 40 to reach its rear end position before the completion of the filling operation. Then, a check signal is sent from the electric servomotor 43 to the control unit 51 to check that the core pin 40 is positioned at its rear end position. 4) In the fourth step, the main control unit 61 receives the inspection signal in step 3 from the control unit 51 and retains the mold cavity 25 filled with the molding material 3 for a predetermined period of time to allow the component to solidify and cool. 5) In a fifth step, the moulding tool assembly 5 causes the mould cavity 25 to be opened via the main control unit 61, whereby the tool part 22 is axially withdrawn from the tool part 21. The produced component 1 is removed in a conventional manner, for example by means of a robot arm.

[0084] The removed assembly is then suitably debonded and sintered.A new process cycle for manufacturing a component is started in the same manner in the molding tool assembly by following steps 1-5.

[0085] Example

[0086] A drill tip having a diameter of 16 mm is powder injection molded using a molding tool assembly 5 having a cylindrical movable core pin 40, wherein the core pin 40 is positioned in its front end position of the mold cavity 25 before the molding material 3 is injected. The volume of the mold cavity 25 is 3.5-4 cm 3 The end surface 42 of the core pin 40 is positioned at its front end position 8 mm from its rear end position and 8 mm from the outlet opening 34. When the core pin 40 is at its rear end position (with Figure 1 The outlet opening 34 is flush with the tool part 22 in the mold cavity), and the distance between the outlet opening 34 and the end surface 42 of the core pin 40 is 16 mm. A hose 57 is connected to the rear end 48 of the core pin 40 (facing away from the outlet opening 34) outside the mold cavity 25. A threaded joint 58 connected to the hose 57 is attached via a central hole 59 at the rear end 48 of the core pin 40 to enable pressurized air to be supplied via the hose 57. Compressed air at a pressure of approximately 7 bar is applied to the rear end 48 of the core pin 40 in the direction towards the outlet opening 34. Therefore, the core pin 40 is initially positioned and pressed towards its front end position. At a distance of 15 cm 3 After the molding material 3 is discharged into the mold cavity 25 at a flow rate of 1 / s, when the pressure applied by the molding material 3 exceeds the threshold pressure, the core pin 40 is retracted to its rear end position. When the core pin 40 reaches the rear end position, the flat end surface 42 of the retracted core pin 40 is flush with the surrounding surface of the tool portion 22. The mechanical stopper 49 is arranged to prevent the core pin 40 from moving beyond its corresponding end position, such as Figure 6a As further described in .

[0087] Filling of the mold cavity 25 is completed 0.3 seconds after the start of filling, and the core pin 40 retreats to its rear end position about 0.1 seconds before the completion of filling.

[0088] In FIG. 7 , it can be noted that the component 1 (green body) manufactured with the movable core pin 40 has no weld line (see Figure 7a ), while part 2 manufactured without moving the core pin (which remained in its rear end position during the method) had a visible weld line 47 (see Figure 7b ).

Claims

1. A molding tool assembly (5) for powder injection molding a component (1), comprising: i) at least a first tool part and a second tool part (21, 22, 22a, 22b, 23, 24), the first tool part and the second tool part being arranged to define a mould cavity (25) for forming a component (1); ii) an inlet channel (30) for filling the mould cavity (25) with moulding material (3), the inlet channel (30) extending through an opening in the first tool part (21) to the mould cavity (25), and the inlet channel (30) comprising an outlet end (33) having an outlet opening (34) for discharging the moulding material (3) from the inlet channel (30) into the mould cavity (25); iii) a core pin (40), the core pin (40) extending through an opening in the second tool part (22, 22a, 22b), the core pin (40) being movable along a horizontal axis between a rear end position and a front end position, the horizontal axis extending through the center of the core pin (40) and the center of the inlet passage (30), the core pin (40) comprising an end portion (41), the end portion (41) having an end surface (42) facing the outlet opening (34); the core pin (40) being configured to seal the opening in the second tool part (22, 22a, 22b) with its end portion (41) when the core pin (40) is positioned in its rear end position; and wherein, when the core pin (40) is in its front end position, the core pin (40) is positioned so that molding material (3) entering the mold cavity (25) impacts the core pin (40); and iv) a power source (43) configured to maintain the core pin (40) in its forward position until a predetermined pressure threshold is exceeded during filling of the mold cavity (25) to move the core pin (40) to the rearward position; or v) a power source (43) configured to maintain the core pin (40) in its front end position for a predetermined time and to move the core pin (40) to the rear end position after the predetermined time.

2. The molding tool assembly (5) according to claim 1, further comprising a control unit (51), the control unit (51) being connected to the power source (43) for controlling the power source (43).

3. The molding tool assembly (5) according to claim 1 or 2, wherein the power source (43) comprises an electric device, a hydraulic device or a pneumatic device.

4. The molding tool assembly (5) according to claim 3, wherein the electric device comprises an electric servomotor, and wherein, The control unit (51) is configured to control the electric servomotor to perform the following operations: a. before starting to fill the mold cavity (25), moving the core pin (40) to its front end position; b. after the filling has begun, while the mold cavity (25) is being filled, retracting the core pin (40) from its front end position to its rear end position; c. Before completing the filling, positioning the core pin (40) in its rear end position.

5. The molding tool assembly (5) according to any one of claims 1 to 4, wherein the outlet opening (34) is flush with an inner surface of the first tool part (21) facing the molding cavity (25).

6. The moulding tool assembly (5) according to any one of claims 1 to 5, wherein the inlet channel (30) extends centrally through the opening in the first tool part (21).

7. The molding tool assembly (5) according to any one of claims 1 to 6, wherein the ratio of the area of ​​the end surface (42) of the core pin to the area of ​​the outlet opening (34) is in the range of 1.5:1 to 1:1.

5.

8. A molding tool assembly (5) according to any one of claims 1 to 7, wherein the core pin (40) has a rear end (48), the rear end (48) faces away from the outlet opening (34), and the cross-section of the rear end (48) outside the mold cavity (25) is larger than the cross-section inside the mold cavity (25).

9. The molding tool assembly (5) according to any one of claims 1 to 8, wherein a mechanical stopper (49) is arranged outside the mold cavity, and the mechanical stopper (49) is used to prevent the core pin (40) from moving beyond the front end position and the rear end position of the core pin (40).

10. The molding tool assembly (5) according to any one of claims 1 to 9, wherein: i) the power source (43) is configured to maintain the core pin (40) in its forward position until a pressure in the range of 0.1 to 20 bar is exceeded during filling of the mould cavity (25) causing the core pin (40) to move to the rearward position; or ii) the power source (43) is configured to maintain the core pin (40) at its front end position for a period of time ranging from 0.001 to 1 second, starting from the point in time when the molding material starts to fill the mold cavity (25).

11. A molding tool assembly (5) according to any one of claims 1 to 10, wherein when the core pin (40) is in its front end position, the core pin (40) is positioned so that: the end surface (42) of the core pin (40) is positioned 1 to 20 mm away from the outlet opening (34).

12. Method for manufacturing a component (1) in a molding tool assembly (5) according to any one of claims 1 to 11 by powder injection molding, the method comprising: i) positioning the core pin (40) in its front end position, at which the end surface (42) of the core pin (40) is positioned up to 20 mm from the outlet opening (34) and at which the molding material (3) entering the mold cavity (25) impinges on the core pin (40); ii) filling the mould cavity (25) with moulding material (3) discharged through the outlet opening (34) of the inlet channel (30); iii) retracting the core pin (40) from the front end position to the rear end position at a speed such that the retraction of the core pin (40) is completed before the filling of the mold cavity is completed.

13. The method according to claim 12, comprising: The core pin (40) is retracted at a certain speed so that: during the entire process of retracting from the front end position to the rear end position, the end portion (41) of the core pin (40) maintains contact with the flow front of the molding material (25).

14. The method according to claim 12 or 13, comprising: The core pin (40) is moved by means of an electric servomotor (43), which is connected to a control unit (51) which controls the electric servomotor (43).

15. The method according to any one of claims 12 to 14, wherein step iii) comprises: Retraction of the core pin to its rear end position is completed up to 0.01 seconds before complete filling of the mold cavity.

16. The method according to any one of claims 12 to 15, wherein step iii) comprises: After at least 80% of the volume of the mold cavity (25) has been filled, and before the filling is completed, the retraction of the core pin (40) to its rear end position is completed.

17. The method according to any one of claims 12 to 16, wherein the molding tool assembly comprises a control unit (51), the control unit (51) being connected to the power source (43) to control the power source (43); wherein the control unit (51) is configured to control the pneumatic device and / or the hydraulic device or the electric servomotor to perform the following operations: a. before starting to fill the mold cavity (25), moving the core pin (40) to its front end position; b. after the filling has begun, while the mold cavity (25) is being filled, retracting the core pin (40) from its front end position to its rear end position; c. Before completing the filling, positioning the core pin (40) in its rear end position.

18. Method according to any one of claims 12 to 17, wherein a sensor is connected to the control unit to monitor the speed of the core pin (40).

19. A component (1) obtainable by a method according to any one of claims 12 to 18, wherein The component (1) is a blade without a through hole and a weld line, and the blade comprises a cemented carbide, ceramic or metal ceramic blade.

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