Mould for injection moulding plastic parts, and method for demoulding plastic parts
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- BRAUNFORM GMBH
- Filing Date
- 2025-10-13
- Publication Date
- 2026-06-25
Smart Images
Figure EP2025079493_25062026_PF_FP_ABST
Abstract
Description
[0001] TOOL FOR INJECTION MOLDING OF PLASTIC PARTS AND METHOD FOR DEMOLISHING PLASTIC PARTS
[0002] The present invention relates to a tool for injection molding plastic parts and a method for demolding plastic parts.
[0003] The tool according to the invention is used for one-component injection molding as well as two- or multi-component injection molding of plastic parts. Furthermore, the tool according to the invention can be used for processing thermoplastics. Applications with thermosets and elastomers are also conceivable.
[0004] Injection molds for plastic parts generally consist of two mold halves that can be moved apart and together. When the mold is closed, i.e., when the two mold halves are against each other, at least one cavity is formed between them. The viscous plastic is injected into this cavity. After cooling, the two mold halves can be moved apart and the molded plastic parts ejected.
[0005] CN 103 46 54 50 discloses a variant of the bearing arrangement for a scraper strip with sliding guide pins arranged on both sides of the mold core. These pins increase the weight of the scraper strip and, moreover, require some play, which is detrimental to the relative guidance of the scraper strip with respect to the lifting plate. If an additional scraper strip were added, a person skilled in the art would provide twice the number of sliding guide pins in the same position on the mirror side of the lifting plate. This means that the extension of the lifting plate must always be at least twice as wide as the insertion depth of the sliding bearing pins, resulting in a large space requirement within the lifting plate and reduced design freedom.While it is possible to arrange the sliding guide pins on both sides in an offset configuration, the wiper strips are then not interchangeable, and two different wiper strips must always be kept on hand for tool manufacturing and repair. Furthermore, this design of the guide mechanism lacks an end stop. Implementing such an end stop would make a double-sided arrangement of a wiper strip on each side of the lifting plate impossible or would significantly complicate the design. Patent EP 2 753463 B1 describes a tool for injection molding plastic parts of the generic type. This tool features a separate mechanism that is activated when the finished molded parts are to be ejected after the two tool halves have separated.The ejector mechanism consists of a stripper bar, which is mounted on the mold cores, such as mold pins, and is movably mounted on them. Moving the stripper bar forward strips the molded parts from their mold cores. There is no separate guide system to support the stripper bar's own weight. Furthermore, in the stripping position, the stripper bars are only secured by the mold cores. This can place excessive stress on the mold cores, and the stripper bar can even jam. Additionally, the demolding force bends the stripper bar, which also leads to jamming and wear. Each of these issues results in enormous wear on the mating surfaces of the stripper system, particularly between the mold core and the stripper bar. This can even lead to breakage or partial irreversible deformation, and thus to production downtime.
[0006] Another problem with this device is that the lifting plate, and therefore the mold cores, are not actively cooled or temperature-controlled. Injection molds must dissipate a large amount of heat as the injected molten plastic cools. If forming components such as mold cores and their receiving plates are not actively temperature-controlled, they heat up excessively compared to actively cooled areas. This results in a lower-quality molding process and tool wear at the joints due to uneven thermal expansion.
[0007] The aforementioned patent specification also shows the lateral arrangement of the guide plates for guiding the stripper bars. In this arrangement, the guide plates significantly overlap the main parting line and thus extend into the working area of the other tool half. Therefore, arranging the guide plates within the tool structure is only possible to a limited extent and necessitates large recesses in the fixed side of the tool. These recesses, however, destabilize the tool, reducing its rigidity against the clamping force and resulting in increased wear on the mating surfaces in the mold area, particularly on the mold cores. The number of mold cores per stripper bar is thus limited. Consequently, the tool size, or rather the maximum number of cores for a single tool, is also limited.
[0008] Based on this, the invention aims to optimize the wiping mechanism consisting of at least a lifting plate, a mold core, a wiping strip and a guide device.
[0009] The present invention solves this problem by providing a tool according to the invention with the features of claim 1 and by providing a method with the features of claim 16.
[0010] A tool according to the invention is used for injection molding plastic parts in the form of molded parts. It comprises two tool sides in the form of a demolding side and a nozzle side, at least one of which is extendable relative to the other tool side or retractable to form at least one cavity.
[0011] The tool further comprises a demolding unit arranged on or in a side of the tool, with a mold core retaining element and with at least one mold core projecting substantially along its edge from the mold core retaining element. Preferably, several mold cores are provided parallel to each other along one edge of the demolding unit.
[0012] A molded part is injected onto the respective mold core.
[0013] The demolding unit has at least one stripper bar that is linearly movable relative to the mold core holder. Preferably, the demolding unit has two stripper bars arranged linearly movable on opposite edges of the mold core holder. Preferably, the mold core holder is plate-shaped.
[0014] Furthermore, the demolding unit has a guide plate which is movably mounted relative to the mold core retaining element. Specifically, the guide plate is movably arranged perpendicular to the direction of movement of the stripper bars relative to the mold core retaining element. The guide plate has a rib- or groove-shaped guide element with a defined guide path. If the guide element is groove-shaped, the guide path corresponds to the groove's path along the guide plate. The same applies to the path of the guide rib along the surface of the guide plate in the case of a rib-shaped guide element.
[0015] The guide element in question engages with a corresponding engagement element of the wiper blade. In the case of a groove-shaped guide element, the engagement element can be designed as a guide pin, or in the case of a blade-shaped guide element, as a slot-shaped recess.
[0016] The engagement guides the wiper blade along the guide plate in a forced path while performing a relative movement between the guide plate and the mold core holder. This results in a movement of the wiper blade relative to the mold core holder synchronized with the relative movement between the guide plate and the mold core holder. Either the guide plate or the mold core holder can move, while the other component remains stationary relative to the other components on the tool side. It is also possible for both components to move simultaneously.
[0017] The mold core is positioned relative to the stripper bar in such a way that finished molded parts formed on the mold core can be stripped off by the stripper bar. A small clearance between the stripper bar and the mold core is permissible. However, this clearance should be such that the molded part is still gripped by the stripper bar during stripping.
[0018] The guide path defined by the strip- or groove-shaped guide element has a curved profile to ensure gentle removal of the molded part from the mold core.
[0019] Since the risk of disruption to the movement sequence is increased with such a curved path of the forced guidance, the linear bearing of the wiper bar relative to the mold core holding element should be achieved by rolling elements in order to avoid failure of the wiper function.
[0020] Advantageous embodiments of the invention are the subject of the dependent claims.
[0021] The guide element can advantageously be designed as a guide groove, and a guide pin arranged on the scraper bar can engage with the guide groove. Particularly preferably, the guide pin can have a roller, so that the guide pin is mounted on roller bearings in the guide groove.
[0022] Furthermore, the guide path of the guide element, in particular the guide groove, can have a multiply curved profile. This allows the scraper blade to be both decelerated and subsequently accelerated, especially in a central section of the guide path.
[0023] The demolding unit can be advantageously designed such that the guide plate is arranged to be relatively movable relative to the mold core retaining element. This mobility of the guide plate allows it to be partially or completely recessed into the side of the mold.
[0024] Advantageously, a plurality of mold cores can be arranged on two opposite sides of the mold core holder. The stripper bar can have a stripper bushing for each of the mold cores on one side, the stripper bushings of a stripper bar preferably having at least two different lengths. The different lengths allow the stripper bar to be offset against only a portion of the molded parts at a time, thus requiring less force to be applied to the stripper bar to remove the molded parts.
[0025] It is advantageous if the linear bearing of the wiper bar has a bearing pin arranged centrally on the core holder and a guide bushing arranged on or in the wiper bar, in which the rolling elements are arranged and which is mounted on the bearing pin in a rolling manner.
[0026] To reduce uneven thermal expansion and thus minimize disruption to the movement sequence, the demolding unit may have a temperature control line for conveying a temperature control medium into the mold core holding device and / or, particularly preferably, into the individual mold cores of the mold core holding device.
[0027] It is advantageous if the temperature control fluid line extends over at least 60%, preferably at least 85%, of the length of the mold core. This comprehensive and uniform temperature control facilitates easier stripping of the molded parts. Furthermore, the mold core retainer can be located at least partially in the demolding side of the mold and have a surface facing the nozzle side, with the guide plate being arranged relative to the mold core retainer such that, in the injection position, it is flush with the surface of the mold core retainer facing the nozzle side.
[0028] Advantageous for a compact basic structure, the surface of the guide plate can be located anywhere below but no more than 20 mm above the surface of the mold core holding element.
[0029] For a particularly wide variety of manufacturing variants, it is advantageous if the mold core holding device is designed as a lifting plate, preferably as a rotatably mounted index plate, in particular with at least two opposing scraper strips.
[0030] It is of course also possible to provide two scraper strips on opposite sides of the mold core holding device, especially in the case of a non-rotating lifting plate.
[0031] To check the lifting or recessed position of the demolding unit, it is advantageous if the tool has a measuring device, preferably an optical measuring device, particularly preferably a light barrier or a camera.
[0032] For mass production, it is advantageous to arrange a number of demolding units, preferably identical demolding units, in one tool.
[0033] Furthermore, it is advantageous to center the wiper bushing using a centering surface of the mold insert.
[0034] Furthermore, according to the invention, a method for demolding injection-molded plastic parts, in particular by means of a tool according to one of the preceding claims, wherein the tool has at least one demolding unit on a demolding side comprising a mold core retainer with at least one mold core, a guide plate and a stripper strip, and wherein the demolding side also has at least one or more mold inserts, wherein the method comprises the following steps: A. Performing a lifting movement of the entire demolding unit relative to the mold insert and / or a lowering movement of the mold insert relative to the entire demolding unit;
[0035] B. Performing a lifting movement of the guide plate relative to the mold core holding device under positive guidance of the wiper bar, such that it performs a linear movement relative to the mold core holding device; and
[0036] C Stop of the scraper bar in an end position opposite the mold core holder middle.
[0037] The end position can advantageously be stopped at an end stop of the linear bearing.
[0038] Furthermore, it is advantageous to provide a contour bend in the guide path of a strip-shaped or groove-shaped guide means arranged on the guide plate immediately before and / or at the contact point of the wiper strip with the injection molded part.
[0039] The invention is explained in more detail below with reference to an exemplary embodiment and several figures. The invention is not limited to the illustrated embodiment. A person skilled in the art can make numerous modifications based on the illustrated embodiment by applying their specialist knowledge. The figures show:
[0040] Fig. 1 Perspective view of a demolding unit of a tool according to the invention in an injection position in relation to a group of mold inserts of the tool;
[0041] Fig. 2 Perspective view of the demolding unit in a first traversing position opposite the group of mold inserts of the tool;
[0042] Fig. 3 Perspective view of the demolding unit in a second travel position;
[0043] Fig. 4 Perspective view of the demolding unit in a third travel position; Fig. 5 Perspective view of the demolding unit in a fourth travel position;
[0044] Fig. 6 Sectional view through the demolding unit in the position of Fig. 1 along a temperature control plane;
[0045] Fig. 7 Sectional view of the demolding unit of Fig. 11 along the section plane CC;
[0046] Fig. 8a Top view of the demolding unit of Fig. 1 with section plane BB shown;
[0047] Fig. 8b Top view of the demolding unit of Fig. 1 with section plane AA shown;
[0048] Fig. 9 Sectional view of the section plane BB of Fig. 13a;
[0049] Fig. 10 Sectional view of the section plane AA of Fig. 13b;
[0050] Fig. 11 Detail view of a temperature control medium guide of a single mold core of Fig. 11;
[0051] Fig. 12 Sectional view AA of the demolding unit in the first travel position;
[0052] Fig. 13 Sectional view AA of the demolding unit in the second travel position;
[0053] Fig. 14 Sectional view AA of the demolding unit in the third travel position;
[0054] Fig. 15 Sectional view AA of the demolding unit in the fourth travel position;
[0055] Fig. 16 Side view of a tool according to the invention;
[0056] Fig. 17 Detailed sectional view of Fig. 21
[0057] Fig. 18 Perspective view of the demolding side of the tool of Fig. 21 in injection position; Fig. 1 shows a demolding unit of a tool according to the invention.
[0058] The tool, used for two-component injection molding of plastic parts, has at least two tool sides, 1 and 2, a so-called demolding side 1 and a nozzle side 2. For the design of a corresponding tool with two tool halves, reference is made to EP 2 753 463 B1. These two tool halves are openable and closable. The tool halves define mold cavities between them for injection molding the corresponding components of a molded part. The corresponding tool halves do not have to be of the same size. The tool can also include additional components besides the tool halves. The tool halves thus define the two aforementioned tool sides in the form of the demolding side and the nozzle side. Accordingly, the term "tool half" does not limit the scope of protection of a tool according to the invention to only two components. The aforementioned tool sides define a main parting line.
[0059] EP 2 753 463 B1 also describes a lifting plate. This can be raised via a lifting rod and, if necessary, rotated to act as an index plate. This allows, for example, the production of a two-component injection molded part. The inventive guide for the wiper bar, described below, can also be applied to this variant to reduce wear. However, Figures 1-18 show a different variant, which is equipped for injection molding a single-component part.
[0060] Fig. 1, as well as Fig. 8a, Fig. 8b, Fig. 9 and Fig. 10 show a demolding unit 100 of a tool according to the invention in an injection position SP in relation to a group of mold inserts 16 of the tool. Alternatively, only one mold insert may be provided. The demolding unit 100 and the mold inserts 16 are assigned to one side of the tool, in particular one half of the tool, the so-called demolding side.
[0061] The demolding unit 100 comprises a preferably plate-shaped core retainer 4, to which one or more cores 5 are attached. Each core 5 is arranged in a cavity 25, which is partially bounded by the core insert 16 and by one or more further core inserts (not shown), e.g., from another side of the mold. In injection position SP, a liquid plastic melt is introduced into the cavity from the second side of the mold (not shown), the nozzle side, and demolded in the cavity. Both sides of the mold must be designed to withstand the corresponding pressure during demolding. Therefore, the sides of the mold comprise a stack of several, preferably solid, plates, such as a retainer plate for the core inserts, a mounting plate, and optionally, further plates.After the molded part(s) have been demolded, the mold is opened by separating the mold sides. The formed part(s) remain attached to the mold cores, from which they are stripped and ejected.
[0062] The preceding explanation is known to those skilled in the art of plastic injection molding and serves to explain the field of application of the present invention.
[0063] The demolding unit 100 serves to demold a molded part 9 formed in a cavity 25 from the mold core 5.
[0064] For this purpose, the demolding unit 100 has a mold core holding device 4 and a stripper bar 6 arranged thereon and movable relative to the mold core holding device 4. The movableness of the stripper bar 6 can preferably be designed as a linear movableness.
[0065] The stripper bar 6 has openings 33 through which the respective mold core(s) 5 are passed. Each mold core 5 has a longitudinal axis. The stripper bar 6 moves linearly in a direction parallel to the longitudinal axis of the respective mold core 5.
[0066] The stripper bar 6 is guided during its linear movement by a guide system. The guide system comprises at least one guide plate 7 arranged on the edge of the mold core holding element 4, with at least one guide groove 8 having a curved profile. The guide groove defines a travel speed of the stripper bar 6 away from the mold core holding element 4. Due to the curved profile, a non-uniform speed profile is formed for the linear movement between the respective stripper bar 6 and the mold core holding element 4, while the feed rate between the mold core holding element 4 and the guide plate 7 remains constant. To follow the profile of the guide groove 8, the corresponding stripper bar 6 has a guide pin 11, which preferably projects from the edge of the stripper bar 7. The guide pin 11 can optionally be recessed to reduce jamming.have a guide roller which rests on the surface of the guide groove 8 and rolls along this surface during a relative movement of the wiper bar 6 with respect to the mold core retaining element 4.
[0067] Furthermore, the guide system comprises a bearing journal 13 with a longitudinal axis parallel to the longitudinal axes of the mold core 5. The bearing journal 13 is fixed to the mold core holding element 4. The stripper bar 6 is guided on the bearing journal 13, so that the mold cores 5 are relieved of stress and have a certain amount of play relative to the stripper bar 6 or a stripper bushing 15 arranged thereon. This stripper bushing 15 projects from the stripper bar 6 in the direction of the cavity 25. In Fig. 1, one stripper bushing 15 is provided for each mold core, so that several stripper bushings 15 are arranged parallel to each other and fixed to the stripper bar 6.
[0068] If several wiper bushings 15 are arranged on a wiper strip 6, they have at least two different lengths. The length differences may be less than 1 mm. These length differences are advantageous because the forces transmitted by the wiper strip 6 to the molded parts 9 are distributed across two or more extension positions of the wiper strip 6. This results in less mechanical stress and damage to the molded parts 9.
[0069] To guide and support the wiper strip 6 on the bearing journal 13, the wiper strip 6 has a guide bushing 12 with rolling elements 40, which are shown in detail in Fig. 14. The rolling element bearing significantly reduces wear and the risk of jamming when the guide journal 11 passes through the guide groove 8.
[0070] For uniform force distribution and trouble-free guidance, it is advantageous if the rolling element bearing of each wiper strip is provided with a bearing journal 13 and a corresponding guide bushing 12 on both sides with respect to the arrangement of the mold cores 5 on a wiper strip 6. The edge-side arrangement of a guide plate 7 should also be made on two opposite edges of the wiper strip 6 and / or the mold core retaining element 4.
[0071] To prevent the wiper bar 6 from unintentionally detaching from the mold core holding element in the extended state and to further limit the linear movement of the wiper bar, the bearing pin 13 can have a stop, here in the form of a burst sleeve.
[0072] In the injection position PS, the demolding unit 100 is arranged along a so-called main parting line 23. This main parting line 23 runs above the cavity parting line 20 between two opposing cavity-forming mold inserts 16 on two sides of the mold. The main parting line 23 and the cavity parting line 20 have a defined distance x in the injection position. This is shown, among other things, in Fig. 15.
[0073] In Fig. 2, the demolding unit 100 is raised relative to the arrangement of mold inserts 16. The stroke 101 and 102 ensures that the demolding unit 100 is therefore positioned above the main parting line 23. Both the guide plate 7 and the mold core retainer 4 with the stripper bars 6 attached to it are raised by the same amount.
[0074] The strokes 101 and 102 are necessary in this design variant to enable the injection molded parts 9 to be lifted out of the mold inserts 16 and, on the other hand, to allow a relative movement of the guide plate 7 to the mold core retaining device 4 against the stroke direction 102 and thus to allow movement of the guide pin 11 in the guide groove 8.
[0075] The stroke reveals the structure of the mold insert 16. In addition to the cavity 25, it has an adjacent sealing and centering surface 22, located towards the mold core holder 4, for interaction with the mold core 5 in the injection position. A centering surface 21 is also provided on the opposite side of the cavity 25 for centering the respective wiper bushing 15. This centering surface pre-centers the wiper bushing 15, and thus also the mold core 5 (which is supported by a clearance or transition fit), when the mold core 5 is inserted. During fine centering, the wiper bushing 15 is relieved of stress by the centering surface 22. This reduces wear and increases service life. In the first travel position PO shown in Fig. 2, the wiper strip 6 is preferably in a position without a gap to the mold core holder 4 or with a minimal gap to this mold core holder 4.
[0076] The position of the guide pin 11 within the guide groove 8 of the guide plate 7 is analogous in the first approach position PO in Fig. 2 to the position in Fig. 1 in the injection position SP.
[0077] Fig. 3 shows the demolding unit 100 in a second travel position P1. In this position, the guide plate 7 is raised relative to the mold core holder 4 by an additional stroke 102. The guide groove 8 of the guide plate 7 provides positive guidance for the guide pin 11, causing the associated wiper bar 6 to move linearly away from the mold core holder 4 in the travel direction 103. The same occurs with the second wiper bar 6 on the opposite side of the mold core holder. The bearing and guidance during this linear movement are provided by the rolling element bearing 10, which is arranged in the guide bushing 12. The guide bushing 12 is preferably a recirculating ball bushing, which is arranged in the wiper bar in a space-saving manner and protected from contamination. A rolling element cage is not provided for ball recirculating bushings, as this bearing bushing is based on the principle of the further transport of the rolling elements.
[0078] As can be seen in Fig. 3, the scraper bar 6 is spaced or moved away from the mold core holding means 4 by a certain amount.
[0079] In Fig. 4, the demolding unit 100 is in a third travel position P2.
[0080] In this process, the guide plate 7 was raised relative to the mold core holding device 7 by a further stroke 102, whereby the forced movement of the guide pin 11 in the guide groove 8 triggered by the stroke leads to a further linear displacement 103 of the wiper strip 6 relative to the mold core holding device 4.
[0081] The curved contour of the guide groove 8 is explained in more detail with reference to Fig. 5. Starting from a first opening of the guide groove in a first edge surface of the guide plate 7, the guide groove has a steep, in this case even vertical, drop 26 until a first curvature 27, in which the rolling path defined by the guide groove 8 is deflected by at least 30°, preferably by 40-90°. As it passes through this curvature 27, the scraper bar 6 is spaced away from the mold core retaining element at an accelerated rate.
[0082] This deflection due to the curvature 27 culminates in a maximum or contour kink 28, where the flattening profile of the guide groove 8 transitions into a steeper curvature region 29. In this curvature region, an initially very small linear displacement of the wiper blade occurs.
[0083] 6 with simultaneously increased force. At this point of low feed of the stripper bar, the stripper bushings 15 come into contact with the molded part 9. Here, a slow, gradual demolding is to take place. Therefore, the stripper bar 6 is guided by the positive guide 104 through the contour of the guide groove.
[0084] 7 immediately upon contact with the injection mold 9, the feed rate is slowed or adjusted to a low feed rate.
[0085] After the molded parts 9 have been gently detached from the mold core 5, the stripper bar 6 undergoes an accelerated linear movement for the purpose of ejecting the molded parts 9. This is achieved via a linearly extending section 30 of the guide groove 8, which opens at a second edge surface perpendicular to the first edge surface of the first opening.
[0086] As the expert can therefore see from the multiply curved contour of the guide groove 8, the feed of the linear movement of the scraper bar 6 relative to the mold core holding means 4 is determined by the positive guidance of the guide pin 11 in the guide groove 8.
[0087] During the entire demolding process, the guide pin 11 does not leave the positive guidance 104 of the guide groove 8. The movement of the guide pin 11 within the guide groove 8 is controlled by the axial stop 14 of the rolling element bearing, which is located on the bearing pin 13.
[0088] In Fig. 5, demolding unit 100 is located at the fourth travel position P3 with the stripper bar 6 in its fully extended position relative to the mold core retainer 4. In this position, a plate-shaped mold core hold-down device 18 is visible. This is attached to the mold cores 5. The mold cores 5 have an end thickening (not shown), e.g., a foot section or the like, which sits in a corresponding recess in the mold core retainer 4. This is shown in detail in Fig. 11. The mold cores 5 can be replaced by loosening the mold core hold-down device 18.
[0089] The wiper bushings 15 can also be adapted to the contour of the molded part 9, for example, in length and shape. If, for example, a molded part with a spur gear toothing is produced, a wiper bushing 15 with mating teeth is recommended to ensure full contact with the end faces. It is therefore advantageous if the wiper bushings 15 are detachably and replaceably arranged on the wiper strip. In the variant shown in Fig. 5, the wiper bushings 15 are held on the wiper strip 6 by detachable wiper bushing retainers 19.
[0090] Another aspect is the cooling of the mold cores 5 for this demolding unit 100.
[0091] The device disclosed in EP 2 753 463 B1 has a lifting plate that is not actively cooled or temperature-controlled. Consequently, the mold cores are also not actively cooled. Injection molds must dissipate a large amount of heat as the injected plastic melt cools. If forming components such as mold cores and their receiving tool plates are not actively temperature-controlled, they heat up excessively compared to actively temperature-controlled areas. Due to the large number of moving components in the demolding unit 100 according to the invention and the possibility of fixing a large number of mold cores, increased heat input into the mold is likely.This results in increased tool wear on the fits, in particular on the moving and precisely guided stripping strips 6 and the mold core holding device 4 due to uneven thermal expansion, especially compared to other actively cooled components, such as the mold inserts 14 with the cavities 25.
[0092] Therefore, it is advantageous to provide a temperature control fluid line 31 for conveying a temperature control fluid into the mold core holding device 4 and / or, particularly preferably, into the individual mold cores 5 of the mold core holding device 4. Such a temperature control fluid line 31 is shown in its entirety in Fig. 6 and in an enlarged view with a flow pattern for a mold core in Fig. 11.
[0093] Fig. 6 shows a section of the demolding unit 100 at the level of a temperature control plane. The temperature control fluid is supplied via a supply line 32 below the demolding unit 100. This can be done, for example, as in EP 2 753 463 B1, via a lifting rod or other actuating means, with which the first traverse step PO can be carried out with the total stroke of the demolding unit 100.
[0094] From the supply line 32, the coolant is routed to at least one first temperature distribution line, which extends parallel to the longitudinal axis of the mold part holding device 4. From the temperature distribution line, the coolant is transferred to a mold core supply channel 34, which branches off perpendicularly to the temperature distribution line and runs parallel to the mold core 5. Parallel to the mold core supply channel 34, a discharge channel 35 extends over at least 60%, preferably at least 85%, of the length of the mold core 5.
[0095] The respective discharge channels 35 open into one or more secondary temperature control fluid discharges 36, which extend parallel to the longitudinal axis of the mold core holding element 4. Finally, the temperature control fluid section 36 opens into a discharge 37, which is provided downwards by an actuating element (not shown) for moving the demolding unit 100.
[0096] The temperature control fluid line 31 is shown in a section perpendicular to Fig. 6 in Fig. 10. The temperature control distribution line 24, which is centrally located in the embodiment shown in Figs. 1-15, can be seen. This can also be arranged decentrally and / or divided into several lines. The core feed channel 34 extends over a large part of the length of the core for cooling purposes. The same applies to the discharge channel 35, which, in the case of Figs. 10 and 11, extends coaxially to the core feed channel 34 within the core 5. Furthermore, Fig. 10 again shows the main parting line 23 and the cavity parting line 20, which is offset from it. In the injection position shown in Figs. 10 and 11, the perpendicular distance between the two aforementioned parting lines is x.This amount x is preferably less than the maximum overall height of the demolding unit 100 or less than the height of the mold core retaining element 4, which extends perpendicular to the longitudinal axis of the mold core retaining element 4. The guide plate 7 of the demolding unit 100 is flush with the main parting line 23, so that a large part of the guide plate 7 is recessed in a receptacle of the tool side, i.e., in the demolding side of the tool according to the invention. Fig. 7 also shows a side view of the arrangement consisting of the demolding unit 100 and the mold inserts 16. The structure of the tool side continues below the mold inserts and the demolding unit 100 by means of further plates. Clearly visible in Fig. 7 are the retainers of the stripper bushings 15 and the bearing journals 13 of the roller guide of the stripper strip 6, which are arranged at the edge for the arrangement of the mold cores 5.
[0097] Figures 8a and 8b each show a top view of the demolding unit 100 with several section planes AA and BB indicated, which are shown in more detail in Figures 9 and 10. In these figures, the demolding unit is also in the injection position SP. Figure 11 shows the cooling fluid line 38 through the mold inserts 16, which serves, among other things, to cool the cavity 25. The cross-section of the cooling fluid line 38 shows the extent of cooling in this area. In contrast, the mold cores 5 were previously uncooled during this type of demolding, resulting in an uneven heat distribution and significant differences in thermal expansion within the tool. Cooling the mold cores reduces, among other things, wear on the fits and increases the quality of the produced molded parts 9.
[0098] Figure 11 further illustrates the flow path of the temperature control medium within a mold core 5 as part of the temperature control line 31 of the demolding unit 100. Starting from the temperature control distributor line 24, a first diversion occurs in the direction of the longitudinal axis of the mold core 5 into the mold core feed channel 34. Finally, the temperature control medium is diverted 180° into the discharge channel 35 and returned to the mold core holder 4.
[0099] Fig. 11 also shows several centering surfaces 21 and sealing surfaces 22 of individual components, for example the wiper bushing 15 and the cavity 25 opposite the mold core.
[0100] Starting from the injection position SP in Fig. 10, a motion study of this sectional view AA in the respective travel positions PO and P3 is carried out using Figs. 12-15. As can be seen in Fig. 12, an additional stroke y occurs in the travel position PO, so that the distance between the main parting line 23 and the cavity parting line 20 increases to a value x+y. The guide plate 7 then moves relative to the mold core holding element 4 in the stroke direction, resulting in positive guidance and a deflection of the movement into a linear motion by the wiper bars 6 perpendicular to the stroke direction of the guide plate 7.
[0101] In Fig. 13, the stripper bar 6 moves into a travel position P1. In Fig. 14, the stripper bar 6 makes contact with the molded part 9 in travel position P2 and the molded part 9 is slowly stripped from the mold core 5. Finally, after stripping, the molded part 9 is advanced axially on the mold core 6 to a final position P3, which is shown in Fig. 15.
[0102] Fig. 16 shows a side view of a tool according to the invention with at least a first and a second tool side, which are preferably designed as two tool halves. In this embodiment, the tool side, the demolding side 1, is designed as a movable tool side, and the tool side, the nozzle side 2, is designed as a fixed tool side. The tool also has a measuring device 41 for detecting the position of the demolding unit 100. This can be, for example, a light sensor for detecting a light signal, e.g., as part of a photoelectric sensor. Furthermore, the tool has a photoelectric sensor for generating a light beam 43 as part of the photoelectric sensor. Other measuring devices, in particular other optical measuring devices, for detecting the position of the demolding unit 100, e.g., a camera or the like, can also be used alternatively. These serve, for example,the detection of whether the demolding unit 100 is in injection position SP, so that a plastic melt can be introduced and / or the two tool sides can be brought together.
[0103] Furthermore, Fig. 17 shows a mold insert 17 of the nozzle side 2, which together with the mold insert 16 forms the injection molding cavity.
[0104] Fig. 18 also shows a frame-shaped retaining plate 42, by means of which the demolding unit 100 is fixed in the injection position in the mold. This can simultaneously position and / or support the mold inserts 16.
[0105] Furthermore, as can be seen in Fig. 18, the surface of the guide plate 7 facing the nozzle side is preferably flush with the surface of the mold core retaining element 4. This means that no, or at least no large, recess is required on the nozzle side, which in turn significantly reduces tool stiffness. Moreover, this simplifies the integration of tool cooling in terms of installation space. Considering these aspects, the aforementioned surface of the guide plate 7 can in any case be located below, but at most 20 mm above, the mold core retaining element.
[0106] As mentioned in the introduction, the number of mold cores per stripper strip is limited by the demolding forces. By limiting the overhang of the guide plate 7 relative to the mold part holder 4 and its recess into the demolding side, a compact demolding unit 100 can be realized that can be replicated in any number within a single tool design, thus maximizing cost-effectiveness. Figures 23-25 show four such demolding units 100. It is particularly evident that a plurality of demolding units are arranged in a plurality of rows.
[0107] The tool exhibits a first and a second direction of thermal expansion, W and V, which, due to differing temperature distributions, are subject to varying degrees of expansion in different areas. Therefore, adjusting the temperature conditions through temperature control or cooling is advantageous.
[0108] Fig. 18 shows the demolding side of the tool of Fig. 16 in injection position.
[0109] The embodiment shown in Figs. 1-18 is only one example within the scope of the present invention. It is also possible, for instance, for the mold inserts 16 to retract relative to the demolding unit 100 so that the exposed molded parts 9 are stripped off. In this case, the mold inserts 16 perform a negative stroke relative to the demolding unit 100, which remains in its position.
[0110] In the illustrated embodiment, the guide plate 7 moves relative to the mold core holding element 4 and the stripper bars 6 attached to it. This mold core holding element 4 preferably remains rigid relative to the rest of the tool side during the execution of the linear movement of the ejector bar 6.
[0111] Alternatively, as part of a mechanical reversal, it is also possible that the guide plate 7 is rigidly arranged on the rest of the tool side, at least during the linear movement of the ejector bar 6, and that the mold core holding device 4 is movable during the extension, in particular arranged linearly relative to the guide plate 7.
[0112] Furthermore, the mold core holder 4 can be designed as a rotatably mounted index holder. This is particularly advantageous when implementing a two-component injection molding process, in which a different component of the finished molded part is provided on each side of the index holder by means of one or more mold cores. In a one-component injection molding process, the mold core holder 4 can alternatively be designed as a non-rotating lift plate, and the same molded parts are formed on each side of this lift plate.
[0113] Furthermore, in the context of a mechanical reversal, the guide groove 8 can also be designed as a strip-shaped guide projection, and the wiper strip 6 can have a guide groove which engages with the guide projection. Both the guide groove 8 and the guide projection define a guide path for the positive guidance 104.
[0114] Reference sign
[0115] 1 demolding side
[0116] 2 nozzle side
[0117] 4 mold core retaining devices
[0118] 5 mold core
[0119] 6 scraper strip
[0120] 7 Guide plate
[0121] 8 guide groove
[0122] 9 sprue
[0123] 10 rolling element bearing
[0124] 11 guide pins
[0125] 12 Guide bushing
[0126] 13 bearing journals
[0127] 14 Axial stop
[0128] 15 wiper bushing
[0129] 16 Mold insert
[0130] 17 Mold insertion
[0131] 18 Mold core hold-downs
[0132] 19 wiper bushing retainers
[0133] 20 Cavity separation plane
[0134] 21 Centering area
[0135] 22 Sealing and centering surface
[0136] 23 Main separation plane
[0137] 24 Temperature control fluid distribution line
[0138] 25 cavities
[0139] 26 Waste
[0140] 27 first bend
[0141] 28 contour bend
[0142] 29 second curvature
[0143] Section 30
[0144] 31 Temperature control fluid line
[0145] 32 Supply line
[0146] 33 Opening
[0147] 34 Mold core feed channel
[0148] 35 Drainage channel
[0149] 36 temperature control fluid drains
[0150] 37 Derivation
[0151] 38 Temperature control fluid line 40 Rolling elements
[0152] 41 Measuring device
[0153] 42 Mounting plate
[0154] 43 Light beam
[0155] 100 demolding units
[0156] 101 Lifting direction
[0157] 102 Lifting direction
[0158] 103 linear direction of travel 104 forced guidance
[0159] SP injection position
[0160] P0-P3 Travel position x Distance main parting plane - cavity parting plane y Stroke
Claims
Claims 1. Tool for injection molding plastic parts in the form of injection molded parts (9), comprising two tool sides, a demolding side (1) and a nozzle side (2), at least one of which is extendable relative to the other tool side or retractable to form at least one cavity; comprising a demolding unit (100) arranged on or in a tool side, comprising a core retaining element (4) and at least one core (5) projecting substantially at its edges from the core retaining element (4), onto which an injection molded part (9) is injected, wherein the demolding unit (100) has at least one stripper bar (6) that is linearly movable relative to the core retaining element (4);wherein the demolding unit (100) furthermore includes a guide plate (7) which is movably mounted relative to the core holding means (4) and wherein the guide plate (7) has a rib- or groove-shaped guide means defining a guide path which engages with a corresponding engagement means with the stripper bar (6), so that the stripper bar (6) is guided in a positive guidance (104) along the guide plate (7) when performing a relative movement between the guide plate (7) and the core holding means (4) and thereby a movement of the stripper bar (6) relative to the core holding means (4) takes place synchronously with the relative movement; wherein the core (5) is arranged relative to the stripper bar (6) such that finished molded parts (9) formed on the core (5) can be stripped from the core by the stripper bar (6);wherein the guide path defined by the strip- or groove-shaped guide means has a curved profile; characterized in that the linear support of the wiper strip (6) relative to the mold core holding means (4) is provided by rolling elements (40).
2. Tool according to claim 1, characterized in that the guide means is designed as a guide groove (8) and that a guide pin (11) arranged on the wiper bar (6) engages with the guide groove and is preferably mounted on roller bearings in this guide groove (8).
3. Tool according to claim 1 or 2, characterized in that the guide path of the guide means, in particular the guide groove (8), has a multiply curved profile.
4. Tool according to one of the preceding claims, characterized in that the demolding unit (100) is designed such that the guide plate is arranged to be relatively movable relative to the mold core holding means (4).
5. Tool according to one of the preceding claims, characterized in that a plurality of mold cores (5) are arranged on two opposite sides of the mold core holding means (4) and that the stripper bar (6) has a stripper bushing (16) for each of the mold cores (5) of one side, wherein the stripper bushings (16) of a stripper bar (6) preferably have at least two different lengths.
6. Tool according to one of the preceding claims, characterized in that the linear bearing of the wiper bar (5) has a bearing pin (13) arranged on the form core holder middle (4) and a guide bushing (12) arranged on or in the wiper bar (6), in which the rolling elements (40) are arranged and which is mounted on the bearing pin (13) in a rolling manner.
7. Tool according to one of the preceding claims, characterized in that the demolding unit (100) has a tempering medium line (31) for conveying a tempering medium into the mold core holding means (4) and / or particularly preferably into the individual mold cores (5) of the mold core holding means (4).
8. Tool according to one of the preceding claims, characterized in that the temperature control medium line (31) extends over at least 60%, preferably over at least 85%, of the length of the mold core (5).
9. Tool according to one of the preceding claims, characterized in that the mold core retaining means (4) is at least partially embedded in the demolding side (2) of the tool and has a surface facing the nozzle side (2), wherein the guide plate (7) is arranged relative to the mold core retaining means (4) such that it is in The injection position is preferably flush with a surface of the mold core retaining element (4) facing the nozzle side (2).
10. Tool according to claim 9, characterized in that the surface of the guide plate (7) is located arbitrarily below but at most 20 mm above the surface of the mold core holding means (4).
11. Tool according to one of the preceding claims, characterized in that at least two scraper bars are arranged on opposite sides of the mold core holding means, in particular on a lifting plate.
12. Tool according to one of the preceding claims, characterized in that the mold core holding means (4) is designed as a lifting plate, preferably as a rotatably mounted index plate, in particular with at least two opposing scraper strips (6).
13. Tool according to one of the preceding claims, characterized in that the tool comprises a measuring device (41), preferably an optical measuring device, particularly preferably a light barrier or a camera.
14. Tool according to one of the preceding claims, characterized in that a plurality of demolding units (100) are arranged in a tool.
15. Tool according to one of the preceding claims, characterized in that the stripper bushing (15) is centered by a centering surface (21) of the mold insert (16).
16. Method for demolding injection-molded plastic parts, in particular by means of a tool according to one of the preceding claims, wherein the tool has at least one demolding unit (100) on a demolding side comprising a mold core retainer (4) with at least one mold core (5), a guide plate (7) and a stripper strip (6), and wherein the demolding side also has at least one or more mold inserts (16), wherein the method is characterized by the following steps: A Performing a lifting movement of the entire demolding unit (100) relative to the mold insert (16) and / or a lowering movement of the mold insert (16) relative to the entire demolding unit (100); B. Executing a lifting movement of the guide plate (7) relative to the mold core holding means (5) under positive guidance of the wiper bar (6), such that the wiper bar executes a linear movement relative to the mold core holding means (5); and C Stop of the wiper bar (6) in an end position relative to the mold core holding device (5).
17. Method according to claim 16, characterized in that the stop of the end position takes place at an end stop of the linear bearing.
18. Method according to claim 16 or 17, characterized in that a contour kink (28) of the guide path of a strip-shaped or groove-shaped guide means arranged on the guide plate (7) is provided immediately before and / or at the contact point of the wiper strip (6) with the injection molded part (9).