Pre-chamber bushing for a hot duct nozzle of a hot duct system of an injection molding tool of an injection molding machine, injection molding tool, injection molding machine and process

Description

[0001] The invention relates to a pre-chamber bushing for a hot runner nozzle of a hot runner system of an injection mold of an injection molding machine, an injection mold, an injection molding machine and a method.

[0002] In a hot runner system of an injection molding machine, pre-chamber bushings are used to connect a heated nozzle, namely a hot runner nozzle, to a cooled mold cavity. For this purpose, the pre-chamber bushing must be both thermally conductive for uniform cooling of the cavity and thermally insulating in the hot runner area. The latter is particularly important in the sprue channel of the pre-chamber bushing leading to the cavity of the injection mold.

[0003] Furthermore, the pre-chamber liner must withstand mechanical contact, for example, with a closing pin used to seal the sprue. For this purpose, DE202007006060U1 proposes welding a steel alloy onto a highly thermally conductive base body made of a copper alloy. The applied material forms the sprue and a first section on the front contour of the pre-chamber liner, which serves to delimit a cavity in the injection mold. This steel alloy sprue increases the mechanical stability in this area of ​​the pre-chamber liner. While the thermally conductive base body facilitates more uniform cooling of the cavity, it also significantly conducts heat from the hot runner nozzle to the injection mold – necessitating reheating of the hot runner nozzle and / or leading to fluctuating temperatures of the molten plastic over time.A reduction in the quality of the injection-molded part is therefore to be expected.

[0004] Starting from the prior art described above, the invention therefore aims to create a pre-chamber bushing which, despite high mechanical stability and high thermal conductivity towards the cavity, does not represent a thermal sink for a hot runner nozzle.

[0005] The invention solves the stated problem through the features of claim 1.

[0006] Since the base body is made of a primary steel alloy, a comparatively good thermal decoupling of the injection mold and hot runner nozzle is achieved, thus simplifying their temperature control. This results in a more uniform temperature of the plastic melt when the cavity is fed via the sprue. This thermal decoupling, however, does not impair cavity cooling because the pre-chamber liner features a primary weld overlay of a copper alloy on the outer surface of the base body. This primary weld overlay forms at least part of the lateral shell section and extends from the first section of the front contour to the second section of the front contour. Despite the relatively poor thermal conductivity of the base body, this primary weld overlay ensures sufficient heat dissipation from the cavity, which, for example, minimizes the risk of distortion in the injection-molded part.

[0007] The pre-chamber bushing according to the invention thus not only ensures a more uniform temperature of the plastic melt when the cavity is charged, but also ensures more uniform cooling of this plastic melt in order to guarantee a distortion-free injection-molded part. This enables the stable production of a high-quality injection-molded part.

[0008] Preferably, the second weld overlay is completely surrounded by the first weld overlay. This ensures a gap-free transition between the two weld overlays and thus enables reproducible process conditions.

[0009] For example, the second weld overlay connects to both the base body and the first weld overlay. This improves the strength of the connection between the first weld overlay and the pre-chamber bushing, thus increasing the durability of the pre-chamber bushing – especially when used with a hot runner nozzle.

[0010] The above can be further improved if a weld surface of the second build-up weld on the base body and / or on the first build-up weld extends outwards in a frustoconical shape.

[0011] If at least the front section of the runner channel is fully formed by the second weld overlay, the mechanical stability of the pre-chamber liner for receiving a hot runner nozzle can be further improved. This is especially true when using a hot runner shut-off nozzle. The shut-off then only comes into contact with the second weld overlay, which further increases the durability of the pre-chamber liner.

[0012] Preferably, the lateral shell section is formed from essentially cylindrical subsections, which can further improve the thermal contact between the first overlay weld and the injection mold for cooling the cavity.

[0013] For example, the lateral jacket section can have at least one annular groove for a ring seal to enable a tight connection of the pre-chamber bushing to the injection molding tool.

[0014] For this purpose, it can be provided that the base body has the first annular groove for the first ring seal, with the first overlay weld extending towards the front contour section after this first annular groove.

[0015] The seal between the injection mold and the pre-chamber bushing can be further improved if the first weld overlay has a second annular groove for a second ring seal.

[0016] Particularly high mechanical strength combined with excellent thermal conductivity can be achieved in the first weld overlay if the copper alloy used for the first weld overlay is an aluminum bronze. This is especially true if it is a two-phase aluminum bronze.

[0017] Preferably, the second steel alloy of the second weld overlay has a higher Rockwell hardness (HRC) than the first steel alloy of the base body in order to achieve particularly high wear resistance. For example, the second steel alloy of the second weld overlay has an FeCrMo base. Preferably, the second steel alloy of the second weld overlay has a minimum Rockwell hardness of 44 HRC, particularly 55 HRC.

[0018] Preferably, the copper alloy of the first overlay weld has a higher thermal conductivity than the first steel alloy of the base body and / or than the second steel alloy of the second overlay weld, in order to improve the thermal insulation of the hot runner nozzle relative to the tool.

[0019] For example, the base body has at least one contact surface for the hot runner nozzle in its receiving section, and the base body has a greater material thickness in the area of ​​the contact surface compared to the areas adjacent to it. This further reduces heat loss at the hot runner nozzle.

[0020] The pre-chamber bushing according to the invention is particularly suitable for an injection molding tool or for an injection molding machine with a hot runner system that has a hot runner nozzle projecting into the pre-chamber bushing.

[0021] The invention also aims to further increase the reproducibility in the production of an injection-molded part while reducing operating costs.

[0022] The invention solves the stated problem by claim 15.

[0023] The pre-chamber bushing according to the invention is particularly suitable for the production of an injection-molded part using the injection mold or injection molding machine according to the invention. This allows for a further increase in the reproducibility of the injection-molded part production, while reducing operating costs due to lower heat losses at the hot runner nozzle.

[0024] In The figures illustrate, for example, the subject matter of the invention in more detail by means of a variant embodiment. They show Fig. 1 shows a sectional view of a pre-chamber bushing in an installation situation on an injection molding machine, and Fig. 2 shows a three-dimensional view of the [unclear - possibly referring to the] Fig. 1 illustrated pre-chamber bushing.

[0025] After the Figuren 1 and 2A pre-chamber bushing 1 can be seen, which is provided in an injection molding machine 2, namely between an injection molding tool 3 with a cavity 4 and a hot runner nozzle 5.

[0026] This pre-chamber bushing 1 has a front contour section 1a and a lateral shell section 1b for abutting the tool part 3a of the injection mold 3. The lateral shell section 1b transitions into the front contour section 1a.

[0027] The pre-chamber bushing 1 also has a central receiving section 1c for receiving a hot runner nozzle 5. The hot runner nozzle 5 is – as in Fig.1 schematically represented - a hot runner needle valve nozzle with a valve needle 5a. However, any other hot runner nozzle is also conceivable, such as an open hot runner nozzle or a hot runner valve nozzle with at least one valve element, which includes the hot runner needle valve nozzle with the valve needle 5a.

[0028] A base body 6 of the pre-chamber bushing 1 is made of a first steel alloy. The pre-chamber bushing 1 also has a second weld overlay 7 made of a second steel alloy on the base body 6. For this purpose, a steel powder was welded over, with the first and second steel alloys differing from each other.

[0029] This second weld overlay 7 is provided on the front contour section 1a of the pre-chamber bushing 1 and forms a second, annular section A2 of the front contour section 1a in plan view. Furthermore, the second weld overlay 7 completely forms the front section of the sprue channel 8.

[0030] The base body 6 consists of a first steel alloy which, with its comparatively low thermal conductivity compared to the other materials of the injection mold 3 with higher thermal conductivity, enables thermal separation. The base body 6 preferably has a thermal conductivity of <30 W / (m*K), in particular ≤ 20 W / (m*K).

[0031] For example, the base body 6 is made of a steel from the DIN steel-iron list with the material number 1.4542 (X5-CrNiCuNb16-4). This material has, for example, a thermal conductivity of 16 W / (m*K). Alternatively, a steel from the DIN steel-iron list with the material number 1.2709 could be used.

[0032] However, this does not impair the cooling of the cavity 4, since according to the invention the pre-chamber bushing 1 has a first build-up weld 9 made of a copper alloy on the outside of the base body 6. This first build-up weld 9 forms at least part of the height of the lateral shell section 1b of the pre-chamber bushing 1 - the first build-up weld 9 runs continuously around the base body 6, as shown in Fig. 1 and in Fig. 2 to recognize.

[0033] Furthermore, the first weld overlay 9 extends from a first section A1 of the front contour section 1a to the second section A2 of the front contour section 1a. Since the first section A1 forms part of the mold surface of the cavity 4, sufficient cooling of the cavity 4 can be ensured – thus preventing distortion of the injection-molded part. In the exemplary embodiment, the front contour section 1a is thus formed by its first and second sections A1 and A2.

[0034] Furthermore, how the Fig. 2 The second weld overlay 7 is completely surrounded by the first weld overlay 9. The second weld overlay 7 also connects to both the base body 6 and the first weld overlay 9, forming weld surfaces 10 with the base body 6 and the first weld overlay 9 – which makes this second weld overlay 7 stable and thus mechanically highly resistant to stress on the pre-chamber bushing 1.

[0035] As in the Fig. 1 As can be seen, the weld surface 10 of the second build-up weld 7 on the base body 6 and on the first build-up weld 9 extends outwards in a frustoconical shape. This increases the bonding area, which improves the adhesion of the second build-up weld 7 to the pre-chamber bushing 1. This frustoconical weld surface 10 can be created, for example, by removing material, such as by milling or turning, after the first build-up weld 9 has been produced on the base body 6. The second build-up weld 7 can then be welded onto it in a subsequent step.

[0036] Again Fig. 2 As can be seen, the lateral shell section 1b consists on the outside of essentially cylindrical subsections Z1, Z2. The first subsection Z1 is formed by the first overlay weld 9.

[0037] Two annular grooves 11, 12 for ring seals 11a, 12a are provided on the lateral shell section 1b. The base body 6 has the first annular groove 11 for a first ring seal 11a. The base body 4 thus forms the second subsection Z2. The first weld overlay 9 forms the second annular groove 12 for a second ring seal 12a. This allows the pre-chamber bushing 1 to be tightly integrated into the injection mold 3 of the injection molding machine 2.

[0038] The copper alloy of the first overlay weld 9 is an aluminum bronze - in the exemplary embodiment two-phase - which enables excellent thermal conductivity at high strength and thus cools the cavity 4 particularly advantageously in order to guarantee freedom from distortion on the injection-molded part.

[0039] The copper alloy is applied as a powder by overlay welding. Aluminum bronze with an AlCu base, such as CuAl8, CuAl10, etc., is particularly suitable for this purpose. This AlCu base may contain a maximum of 12% aluminum and, if applicable, additions of a maximum of 2% silicon, a maximum of 6% iron, a maximum of 6% nickel, and / or a maximum of 14% manganese.

[0040] The second steel alloy of the second weld overlay 7 has a higher Rockwell hardness (HRC) than the first steel alloy of the base body 6. This makes the second steel alloy extremely resistant to abrasion and able to withstand the wear-resistant stresses of a hot runner nozzle 5. For this purpose, the second weld overlay in the exemplary embodiment has a Rockwell hardness of 55 HRC. A chemical analysis of the particularly preferred second steel alloy with an FeCrMo base showed: 7.00 wt.% chromium (Cr), 2.50 wt.% molybdenum (Mo), 0.5 wt.% carbon (C), 0.50 wt.% manganese (Mn), 0.40 wt.% silicon (Si), and the remainder being iron (Fe) as well as unavoidable impurities.

[0041] Furthermore, the Fig. 1It can be deduced that the base body 6 has at least one contact surface 13 for the hot runner nozzle 5 in its receiving section 1c. In the area of ​​the contact surface 13, the base body 6 has an increased material thickness compared to its adjacent areas in order to further reduce the heat loss of the hot runner nozzle 5. However, it is also conceivable that the hot runner nozzle 5 additionally has a material with comparatively poor thermal conductivity in this area or that a ceramic ring is provided as a spacer – which has not been shown.

[0042] In general, laser cladding is suitable for both types of overlay welding of powder steel alloys, although not exclusively.

Claims

1. Prechamber bushing (1) for a hot runner nozzle (5) of a hot runner system of an injection molding tool (3) of an injection molding machine (2), having a base body (6) made of a first steel alloy, having a second build-up weld (7) made of a second steel alloy on the base body (6), wherein the prechamber bushing (1) has a lateral jacket section (1b) for bearing against a mold part (3a) of the injection molding tool (3) of the injection molding machine (2), a front contour section (1a) for a cavity (4) of the injection molding tool (3), and a sprue channel (8) for the cavity (4) of the injection molding tool (3) emerging at the front contour section (1a), and wherein the second build-up weld (7) forms a second section (A2) on the front contour section (1a) and at least partially forms the sprue channel (8), characterized in that the prechamber bushing (1) has a first build-up weld (9) made of a copper alloy on the outside of the base body (6), wherein the first build-up weld (9) at least partially forms the lateral jacket section (1b) at least partially and extends over a first section (A1) of the front contour section (1a) to the second section (A2) of the front contour section (1a).

2. Prechamber bushing according to claim 1, characterized in that the second build-up weld (7) extends continuously around the first build-up weld (9).

3. Prechamber bushing according to claim 1 or 2, characterized in that the second build-up weld (7) connects to both the base body (6) and the first build-up weld (9).

4. Prechamber bushing according to one of claims 1 to 3, characterized in that a weld surface (10) of the second build-up weld (7) on the base body (6) and / or on the first build-up weld (9) widens / widen outward in a truncated cone shape.

5. Prechamber bushing according to one of claims 1 to 4, characterized in that at least the front section of the sprue channel (8) is completely formed by the second build-up weld (7).

6. Prechamber bushing according to one of claims 1 to 5, characterized in that the lateral jacket section (1b) is formed by substantially cylindrical subsections (Z1, Z2).

7. Prechamber bushing according to one of claims 1 to 6, characterized in that the lateral jacket section (1b) has at least one annular groove (11, 12) for an annular seal (11a, 12a).

8. Prechamber bushing according to claim 7, characterized in that the base body (6) has the first annular groove (11) for the first annular seal (11a), wherein the first build-up weld (9) extends in the direction of the front contour section (1a) after this first annular groove (11).

9. Prechamber bushing according to claim 7 or 8, characterized in that the first build-up weld (9) comprises the second annular groove (12) for a second annular seal (12a).

10. Prechamber bushing according to one of claims 1 to 9, characterized in that the copper alloy of the first build-up weld (9) is an aluminum bronze, more particularly a two-phase aluminum bronze.

11. Prechamber bushing according to one of claims 1 to 10, characterized in that the second steel alloy of the second build-up weld, more particularly with an FeCrMo base, has a higher Rockwell hardness (HRC) than the first steel alloy of the base body (7) and / or in that the second steel alloy of the second build-up weld has a minimum Rockwell hardness of 44 HRC, more particularly 55 HRC.

12. Prechamber bushing according to one of claims 1 to 11, characterized in that the copper alloy of the first build-up weld (9) has a higher thermal conductivity than the first steel alloy of the base body (4) and / or than the second steel alloy of the second build-up weld (7).

13. Prechamber bushing according to one of claims 1 to 12, characterized in that the base body (6) has at least one contact surface (13) for the hot runner nozzle (5) in its receiving section (1c) for the hot runner nozzle (5), wherein the base body (6) has an increased material thickness in the region of the contact surface (13) compared to regions adjacent thereto.

14. Injection molding tool or injection molding machine having a hot runner system comprising a hot runner nozzle (5) and a prechamber bushing (1) according to one of claims 1 to 13, wherein the hot runner nozzle (5) protrudes into the prechamber bushing (1).

15. Method for producing at least one injection molded part using an injection molding tool (3) or an injection molding machine (2) according to claim 14.