CA2340263A1 - Hot runner nozzle with ceramic shut-off needle - Google Patents
Hot runner nozzle with ceramic shut-off needle Download PDFInfo
- Publication number
- CA2340263A1 CA2340263A1 CA002340263A CA2340263A CA2340263A1 CA 2340263 A1 CA2340263 A1 CA 2340263A1 CA 002340263 A CA002340263 A CA 002340263A CA 2340263 A CA2340263 A CA 2340263A CA 2340263 A1 CA2340263 A1 CA 2340263A1
- Authority
- CA
- Canada
- Prior art keywords
- needle
- shut
- hot runner
- ceramic
- runner nozzle
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000000919 ceramic Substances 0.000 title claims description 32
- 229910010293 ceramic material Inorganic materials 0.000 claims abstract description 6
- 238000000465 moulding Methods 0.000 claims description 36
- 239000000203 mixture Substances 0.000 claims description 19
- 238000002347 injection Methods 0.000 claims description 13
- 239000007924 injection Substances 0.000 claims description 13
- 239000004415 thermoplastic moulding composition Substances 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 claims description 10
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims description 10
- 229910001928 zirconium oxide Inorganic materials 0.000 claims description 10
- 239000000155 melt Substances 0.000 claims description 5
- 229910052839 forsterite Inorganic materials 0.000 claims description 2
- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 claims description 2
- 229910052573 porcelain Inorganic materials 0.000 claims description 2
- 239000000206 moulding compound Substances 0.000 abstract 1
- 238000009757 thermoplastic moulding Methods 0.000 abstract 1
- 238000001746 injection moulding Methods 0.000 description 15
- 229910000831 Steel Inorganic materials 0.000 description 11
- 239000010959 steel Substances 0.000 description 11
- 238000001816 cooling Methods 0.000 description 8
- 238000000034 method Methods 0.000 description 5
- 229910000760 Hardened steel Inorganic materials 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000005485 electric heating Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 229920001169 thermoplastic Polymers 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000012815 thermoplastic material Substances 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/26—Moulds
- B29C45/27—Sprue channels ; Runner channels or runner nozzles
- B29C45/28—Closure devices therefor
- B29C45/2806—Closure devices therefor consisting of needle valve systems
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/26—Moulds
- B29C45/27—Sprue channels ; Runner channels or runner nozzles
- B29C45/28—Closure devices therefor
- B29C45/2806—Closure devices therefor consisting of needle valve systems
- B29C2045/2858—Materials or coatings therefor
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
The invention relates to a hot runner nozzle (1) comprising a shut-off needl e (2) and designed for injecting thermoplastic moulding compounds into moulds, where the shut-off needle (2) consists fully or partly of a ceramic material .
Description
z . _ 1 _ Hot runner nozzle having a ceramic shut-off needle The present invention relates to a hot runner nozzle having a shut-off needle for injecting thermoplastic moulding compositions into moulds, the shut-off needle being wholly or partly of ceramic.
Hot runner nozzles are used in the prior art for manufacturing mouldings of thermoplastic moulding compositions by means of injection moulding. Hot runner nozzles serve to inject the melt of the thermoplastic moulding composition into the cavity of the mould without the melt solidifying. In order to keep the moulding composition above the melting point, the nozzle can be heated by means of electric heating elements.
Hot runner nozzles can be constructed with or without a shut-off needle.
Nozzles having a shut-off needle serve to close the mould cavity at the end of the injection procedure. When the mould is opened, no more melt from the thermoplastic material can then emerge from the hot runner nozzle. Shut-off needles also make it possible to manufacture mouldings which have a smooth surface at the injection point. A
smooth surface at the injection point can represent a substantial quality feature in the corresponding mouldings.
Known hot runner nozzles having shut-off needles, such as those described in 758 and EP 0 765 728, substantially comprise a nozzle housing surrounded by 25 electric heating elements and enclosing a melt runner, a nozzle orifice which can be shut off by a shut-off needle, and a needle drive unit. Known hot runner nozzles use hydraulic or pneumatic cylinders in order to be able to move the needle either directly or by way of a lever and open or close the shut-off point. When the cavity is filled, the hot moulding composition flows along the opened needle in the hot runner 30 nozzle. This warms the needle. After the needle has been closed, it forms a hot spot which favours adhesion of the moulding composition. By way of the surface through ~ _5 3 G 16 which the shut-off needle bears against the cooled mould wall, the needle tip is then cooled again. In order to achieve a high cooling capacity, a material of high thermal conductivity is conventionally used to manufacture the needles.
The needle of lmown hot runner nozzles is made for example of hardened steel.
Known hot runner nozzles having steel shut-off needles made have a number of disadvantages. Shut-off needles made of steel are subject to wear if the thermoplastic moulding compositions contain solid fillers, e.g. abrasive powders or mineral fibres.
Using steel shut-off needles with needle gates of large cross-section may result in adhesion of the moulding composition. When the mould is opened and the moulding removed, this adhesion of the moulding composition then results in instances of unevenness on the moulding in the region of the injection point, which reduces the quality.
Normally, problems with adhesion to the shut-off needle are solved by extending the cooling period in the process cycle. A longer cooling time also extends the overall process cycle time and in the end results in increased manufacturing costs for the mouldings. It is also possible to reduce the cross-section of the needle gate to overcome this problem. However, small cross-sections are disadvantageous for the injection procedure and hence limit the size of the moulding which can be manufactured without defects. Problems with adhesion can also be solved by reducing the temperature of the temperature-controlled mould in order to cool the needle better. However, reducing the mould temperature is only possible to a limited extent, since many moulding compositions only give high-quality mouldings within a very narrow temperature range.
Ultimately, the surface through which the needle bears against the cooled mould wall can be made larger to avoid adhesion. This salution has the aim of improving the cooling of the needle tip.
Hot runner nozzles are used in the prior art for manufacturing mouldings of thermoplastic moulding compositions by means of injection moulding. Hot runner nozzles serve to inject the melt of the thermoplastic moulding composition into the cavity of the mould without the melt solidifying. In order to keep the moulding composition above the melting point, the nozzle can be heated by means of electric heating elements.
Hot runner nozzles can be constructed with or without a shut-off needle.
Nozzles having a shut-off needle serve to close the mould cavity at the end of the injection procedure. When the mould is opened, no more melt from the thermoplastic material can then emerge from the hot runner nozzle. Shut-off needles also make it possible to manufacture mouldings which have a smooth surface at the injection point. A
smooth surface at the injection point can represent a substantial quality feature in the corresponding mouldings.
Known hot runner nozzles having shut-off needles, such as those described in 758 and EP 0 765 728, substantially comprise a nozzle housing surrounded by 25 electric heating elements and enclosing a melt runner, a nozzle orifice which can be shut off by a shut-off needle, and a needle drive unit. Known hot runner nozzles use hydraulic or pneumatic cylinders in order to be able to move the needle either directly or by way of a lever and open or close the shut-off point. When the cavity is filled, the hot moulding composition flows along the opened needle in the hot runner 30 nozzle. This warms the needle. After the needle has been closed, it forms a hot spot which favours adhesion of the moulding composition. By way of the surface through ~ _5 3 G 16 which the shut-off needle bears against the cooled mould wall, the needle tip is then cooled again. In order to achieve a high cooling capacity, a material of high thermal conductivity is conventionally used to manufacture the needles.
The needle of lmown hot runner nozzles is made for example of hardened steel.
Known hot runner nozzles having steel shut-off needles made have a number of disadvantages. Shut-off needles made of steel are subject to wear if the thermoplastic moulding compositions contain solid fillers, e.g. abrasive powders or mineral fibres.
Using steel shut-off needles with needle gates of large cross-section may result in adhesion of the moulding composition. When the mould is opened and the moulding removed, this adhesion of the moulding composition then results in instances of unevenness on the moulding in the region of the injection point, which reduces the quality.
Normally, problems with adhesion to the shut-off needle are solved by extending the cooling period in the process cycle. A longer cooling time also extends the overall process cycle time and in the end results in increased manufacturing costs for the mouldings. It is also possible to reduce the cross-section of the needle gate to overcome this problem. However, small cross-sections are disadvantageous for the injection procedure and hence limit the size of the moulding which can be manufactured without defects. Problems with adhesion can also be solved by reducing the temperature of the temperature-controlled mould in order to cool the needle better. However, reducing the mould temperature is only possible to a limited extent, since many moulding compositions only give high-quality mouldings within a very narrow temperature range.
Ultimately, the surface through which the needle bears against the cooled mould wall can be made larger to avoid adhesion. This salution has the aim of improving the cooling of the needle tip.
The object of the invention is to construct a hot runner nozzle having a shut-off needle such that high-quality mouldings can be manufactured in the mould while minimising wear of the needle and adhesion of the moulding composition and avoiding the other disadvantages of known arrangements.
This object is achieved in accordance with the invention in that a ceramic shut-off needle is inserted into the hot runner nozzle. Surprisingly, only ceramic needles of particular materials of low thermal conductivity give the desired result. This result is all the more surprising since previous experiences with needles made of steel had the aim of improving the cooling of the shut-off needle and the use of materials of high thermal conductivity. A shut-off needle of low thermal conductivity should rather, in accordance with the current view, make cooling of the needle worse and thus also make the quality of mouldings worse at the injection point.
1 S The invention relates to a hot runner nozzle having a shut-off needle, for the purpose of manufacturing mouldings from thermoplastic moulding compositions, having a heatable nozzle housing which encloses a melt runner and can be shut off by a shut off needle by means of a movable needle drive unit, characterised in that the shut-off needle is of a ceramic material having a thermal conductivity of less than 7 W/m.K
at 100°C.
In a further preferred embodiment of the present invention, only the tip of the shut-off needle is of ceramic, with the needle shaft itself being of metal, in particular of steel or hardened steel. This embodiment has the advantage that the coupling, between the needle and the hydraulic cylinder or the drive lever, and the needle guide can be manufactured of steel. This reduces the risk of breaking the needle when it is installed or during injection moulding.
All the current methods for manufacturing metal/ceramic bonds can be used to attach the ceramic tip to the needle made of steel. This bond should, however, be as resistant to pressure as possible. Preferably, the ceramic tip is manufactured by . . _4_ shrinking the metal needle shaft onto a ceramic pin at the opposite end of the ceramic shut-off needle.
The shut-off needle or ceramic needle tip is preferably of densely sintered and, to as large as possible an extent, non-porous ceramic material having a thermal conductivity of at most 7 W/m.K at 100°C, preferably at most 3 W/m.K at 100°C.
Examples of suitable ceramic material are zirconium oxide, porcelain, forsterite and steatite.
Shut-off needles or needle tips of sintered zirconium oxide or partially stabilised zirconium oxide are particularly preferred. Sintered zirconium oxide has a thermal conductivity in the region of 2 to 2.5 W/m.K. Sintered partially stabilised zirconium oxide, such as ZrOz partially stabilised by MgO, Ca0 or Y203, is particularly preferred as the ceramic material because of its high flexural strength.
The hot runner nozzle according to the invention can be used in a variety of ways in the injection mould, in particular in injection moulding machines for injection moulding thermoplastic polymers and other thermoplastic moulding compositions.
In particular, where hot runner nozzles having shut-off needles of large cross-section are required, the use of the hot runner nozzle according to the invention contributes to a reduction in the cycle time and hence better economy in the injection moulding process.
A particular application of the hot runner nozzle according to the invention is in the injection moulding of thermoplastic moulding compositions containing high quantities of ceramic powders. The injection moulding of these so-called ceramic moulding compositions, which contain in particular from 50 to 70 per cent by volume of ceramic powders, is generally known. 'Che mouldings are subsequently liberated from the organic constituents by the action of heat and then sintered at a temperature of >800°C to give dense ceramic bodies. These ceramic moulding compositions are very abrasive, wear conventional metal shut-off needles rapidly and have a particular tendency to temperature-dependent adhesion. The hot runner nozzles according to the invention having shut-off needles made of ceramic make it possible to manufacture mouldings of high quality from ceramic moulding compositions too, with a minimum of wear and adhesion to the shut-off needle.
The following can be mentioned as advantages of the hot runner nozzles according to the invention having ceramic shut-off needles. Among other things, the needle cross-section can be made bigger and hence the pressure during injection moulding can be reduced without problems with adhesion occurring. The injection moulding cycle time is also shorter than can be achieved with a steel shut-off needle. The ceramic needle according to the invention is more wear-resistant than the standard steel needle.
The invention will be described in more detail with reference to the following examples, without restricting the details of the invention.
In the drawings:
Fig. 1 shows a longitudinal section through the hot runner nozzle according to the line A-B in Fig. 2, Fig. 2 shows a longitudinal section through the hot runner nozzle according to the line C-D in Fig. 1, Fig. 3a shows a shut-off needle with a ceramic tip, Fig. 3b shows a shut-off needle according to Fig. 3a with the ceramic tip separate from it, and Fig. 4 shows an injection mould with the hot runner nozzle according to the invention.
Examples Example 1 An injection mould for manufacturing a moulding weighing approximately 120 g was constructed, as shown in Fig. 4, with a hot runner nozzle. The hot runner nozzle 1 was provided with a ceramic shut-off needle 6 (see Figs. 1 and 4). The hot runner nozzle 1 guides the injection moulding composition along the runner 4, through the electrically heated steel block 3 and 3a centrally to the base of the moulding 11.
During injection moulding, the needle 2 or 6 is opened and closed by the laterally disposed cylinder 5 using compressed air by way of the bars 9. A separately cooled ante-chamber 12 is disposed around the hot runner nozzle. The diameter of the shut-off needle tip 13 was 6 mm.
The shut-off needle 6 was constructed, as shown in Figs. 3a and 3b, from a steel needle 8 having a tip 7 of ceramic. The ceramic tip 7 comprised sintered zirconium oxide, partially stabilised with MgO, having a thermal conductivity of 2.5 W/m.K at 100°C, a density of 5.9 g/cm3 and a flexural strength of 500 N/mm2. The ceramic tip 7 was attached, as shown in Figs. 3a and 3b, to the needle shaft 8 of hardened steel by shrinking the tube 13 of the needle shaft 8 onto the pin 14 of the ceramic tip 7.
Injection moulding tests were carried out on an Arburg Allrounder 370 C
injection moulding machine with a locking force of 100 tonnes and a 35-mm injection unit. A
thermoplastic moulding composition comprising 84% by weight of ceramic powder and 16% of a thermoplastic polymer composition having a melting point of 94°C
was used. The injection moulding composition had a viscosity of 620 Pa.s at a temperature of 130°C.
The following operating parameters were used to injection mould the moulding:
Composition temperature, extruder 160°C
hot runner 160°C
Mould temperature, wall 62°C
ante-chamber 50°C
Injection time 0.7 s Holding pressure time 4 s Holding pressure 250 bar Remaining cooling time 15 s Total cycle time 31 s No adhesion to the shut-off needle made of zirconium oxide was observed. The mouldings obtained were completely free of defects.
Comparison example 2 Comparison tests using the same hot runner nozzle 1 but a shut-off needle 2 manufactured from hardened steel, and with otherwise the same injection moulding conditions as those described in Example 1 above, resulted in pronounced adhesion of the moulding composition to the shut-off needle 2. This adhesion has the effect that when the moulding 11 is removed from the mould it has an irregularly shaped depression. This depression cannot easily be dealt with by secondary finishing.
Lowering the mould temperature of the ante-chamber to 35°C or lowering the temperature of the moulding composition in the hot runner nozzle to 140°C could not completely prevent the adhesion of the moulding composition to the shut-off needle. Even extending the remaining cooling time by 5 to 10 seconds did not give defect-free mouldings.
This object is achieved in accordance with the invention in that a ceramic shut-off needle is inserted into the hot runner nozzle. Surprisingly, only ceramic needles of particular materials of low thermal conductivity give the desired result. This result is all the more surprising since previous experiences with needles made of steel had the aim of improving the cooling of the shut-off needle and the use of materials of high thermal conductivity. A shut-off needle of low thermal conductivity should rather, in accordance with the current view, make cooling of the needle worse and thus also make the quality of mouldings worse at the injection point.
1 S The invention relates to a hot runner nozzle having a shut-off needle, for the purpose of manufacturing mouldings from thermoplastic moulding compositions, having a heatable nozzle housing which encloses a melt runner and can be shut off by a shut off needle by means of a movable needle drive unit, characterised in that the shut-off needle is of a ceramic material having a thermal conductivity of less than 7 W/m.K
at 100°C.
In a further preferred embodiment of the present invention, only the tip of the shut-off needle is of ceramic, with the needle shaft itself being of metal, in particular of steel or hardened steel. This embodiment has the advantage that the coupling, between the needle and the hydraulic cylinder or the drive lever, and the needle guide can be manufactured of steel. This reduces the risk of breaking the needle when it is installed or during injection moulding.
All the current methods for manufacturing metal/ceramic bonds can be used to attach the ceramic tip to the needle made of steel. This bond should, however, be as resistant to pressure as possible. Preferably, the ceramic tip is manufactured by . . _4_ shrinking the metal needle shaft onto a ceramic pin at the opposite end of the ceramic shut-off needle.
The shut-off needle or ceramic needle tip is preferably of densely sintered and, to as large as possible an extent, non-porous ceramic material having a thermal conductivity of at most 7 W/m.K at 100°C, preferably at most 3 W/m.K at 100°C.
Examples of suitable ceramic material are zirconium oxide, porcelain, forsterite and steatite.
Shut-off needles or needle tips of sintered zirconium oxide or partially stabilised zirconium oxide are particularly preferred. Sintered zirconium oxide has a thermal conductivity in the region of 2 to 2.5 W/m.K. Sintered partially stabilised zirconium oxide, such as ZrOz partially stabilised by MgO, Ca0 or Y203, is particularly preferred as the ceramic material because of its high flexural strength.
The hot runner nozzle according to the invention can be used in a variety of ways in the injection mould, in particular in injection moulding machines for injection moulding thermoplastic polymers and other thermoplastic moulding compositions.
In particular, where hot runner nozzles having shut-off needles of large cross-section are required, the use of the hot runner nozzle according to the invention contributes to a reduction in the cycle time and hence better economy in the injection moulding process.
A particular application of the hot runner nozzle according to the invention is in the injection moulding of thermoplastic moulding compositions containing high quantities of ceramic powders. The injection moulding of these so-called ceramic moulding compositions, which contain in particular from 50 to 70 per cent by volume of ceramic powders, is generally known. 'Che mouldings are subsequently liberated from the organic constituents by the action of heat and then sintered at a temperature of >800°C to give dense ceramic bodies. These ceramic moulding compositions are very abrasive, wear conventional metal shut-off needles rapidly and have a particular tendency to temperature-dependent adhesion. The hot runner nozzles according to the invention having shut-off needles made of ceramic make it possible to manufacture mouldings of high quality from ceramic moulding compositions too, with a minimum of wear and adhesion to the shut-off needle.
The following can be mentioned as advantages of the hot runner nozzles according to the invention having ceramic shut-off needles. Among other things, the needle cross-section can be made bigger and hence the pressure during injection moulding can be reduced without problems with adhesion occurring. The injection moulding cycle time is also shorter than can be achieved with a steel shut-off needle. The ceramic needle according to the invention is more wear-resistant than the standard steel needle.
The invention will be described in more detail with reference to the following examples, without restricting the details of the invention.
In the drawings:
Fig. 1 shows a longitudinal section through the hot runner nozzle according to the line A-B in Fig. 2, Fig. 2 shows a longitudinal section through the hot runner nozzle according to the line C-D in Fig. 1, Fig. 3a shows a shut-off needle with a ceramic tip, Fig. 3b shows a shut-off needle according to Fig. 3a with the ceramic tip separate from it, and Fig. 4 shows an injection mould with the hot runner nozzle according to the invention.
Examples Example 1 An injection mould for manufacturing a moulding weighing approximately 120 g was constructed, as shown in Fig. 4, with a hot runner nozzle. The hot runner nozzle 1 was provided with a ceramic shut-off needle 6 (see Figs. 1 and 4). The hot runner nozzle 1 guides the injection moulding composition along the runner 4, through the electrically heated steel block 3 and 3a centrally to the base of the moulding 11.
During injection moulding, the needle 2 or 6 is opened and closed by the laterally disposed cylinder 5 using compressed air by way of the bars 9. A separately cooled ante-chamber 12 is disposed around the hot runner nozzle. The diameter of the shut-off needle tip 13 was 6 mm.
The shut-off needle 6 was constructed, as shown in Figs. 3a and 3b, from a steel needle 8 having a tip 7 of ceramic. The ceramic tip 7 comprised sintered zirconium oxide, partially stabilised with MgO, having a thermal conductivity of 2.5 W/m.K at 100°C, a density of 5.9 g/cm3 and a flexural strength of 500 N/mm2. The ceramic tip 7 was attached, as shown in Figs. 3a and 3b, to the needle shaft 8 of hardened steel by shrinking the tube 13 of the needle shaft 8 onto the pin 14 of the ceramic tip 7.
Injection moulding tests were carried out on an Arburg Allrounder 370 C
injection moulding machine with a locking force of 100 tonnes and a 35-mm injection unit. A
thermoplastic moulding composition comprising 84% by weight of ceramic powder and 16% of a thermoplastic polymer composition having a melting point of 94°C
was used. The injection moulding composition had a viscosity of 620 Pa.s at a temperature of 130°C.
The following operating parameters were used to injection mould the moulding:
Composition temperature, extruder 160°C
hot runner 160°C
Mould temperature, wall 62°C
ante-chamber 50°C
Injection time 0.7 s Holding pressure time 4 s Holding pressure 250 bar Remaining cooling time 15 s Total cycle time 31 s No adhesion to the shut-off needle made of zirconium oxide was observed. The mouldings obtained were completely free of defects.
Comparison example 2 Comparison tests using the same hot runner nozzle 1 but a shut-off needle 2 manufactured from hardened steel, and with otherwise the same injection moulding conditions as those described in Example 1 above, resulted in pronounced adhesion of the moulding composition to the shut-off needle 2. This adhesion has the effect that when the moulding 11 is removed from the mould it has an irregularly shaped depression. This depression cannot easily be dealt with by secondary finishing.
Lowering the mould temperature of the ante-chamber to 35°C or lowering the temperature of the moulding composition in the hot runner nozzle to 140°C could not completely prevent the adhesion of the moulding composition to the shut-off needle. Even extending the remaining cooling time by 5 to 10 seconds did not give defect-free mouldings.
Claims (6)
1. A hot runner nozzle (1) having a shut-off needle (2), for the purpose of manufacturing mouldings from thermoplastic moulding compositions, having a heatable nozzle housing (3, 3a) which encloses a melt runner (4), which hot runner nozzle can be shut off by a shut-off needle (2) by means of a movable needle drive unit, characterised in that the shut-off needle (2) is of a ceramic material having a thermal conductivity of at most 7 W/m.K, preferably at most 3 W/m.K.
2. A hot runner nozzle having a shut-off needle according to Claim 1, characterised in that the shut-off needle (2) is divided into a needle shaft (8) and a tip (7), and the tip (7) of the shut-off needle (2) is of ceramic.
3. A hot runner nozzle having a shut-off needle according to Claim 1 or 2, characterised in that the shut-off needle (2) or the needle tip (7) is substantially of zirconium oxide, porcelain, forsterite or steatite.
4. A hot runner nozzle having a shut-off needle according to Claim 3, characterised in that the shut-off needle (2) or the needle tip (7) is of sintered zirconium oxide or sintered, partially stabilised zirconium oxide.
5. An injection mould for manufacturing mouldings of thermoplastic moulding compositions, including a hot runner nozzle having a shut-off needle according to one of Claims 1 to 4.
6. Use of the hot runner nozzle according to one of Claims 1 to 4 for processing thermoplastic moulding compositions, in particular ceramic moulding compositions, preferably having a ceramic content of 50 to 70% by weight of the moulding composition.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19836506.3 | 1998-08-12 | ||
| DE19836506A DE19836506A1 (en) | 1998-08-12 | 1998-08-12 | Hot runner nozzle with ceramic needle |
| PCT/EP1999/005547 WO2000009311A1 (en) | 1998-08-12 | 1999-07-31 | Hot runner nozzle with ceramic shut-off needle |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2340263A1 true CA2340263A1 (en) | 2000-02-24 |
Family
ID=7877285
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002340263A Abandoned CA2340263A1 (en) | 1998-08-12 | 1999-07-31 | Hot runner nozzle with ceramic shut-off needle |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP1105275A1 (en) |
| JP (1) | JP2003521392A (en) |
| CN (1) | CN1312755A (en) |
| AU (1) | AU5417399A (en) |
| CA (1) | CA2340263A1 (en) |
| DE (1) | DE19836506A1 (en) |
| HK (1) | HK1040378A1 (en) |
| WO (1) | WO2000009311A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7014455B2 (en) | 2002-03-14 | 2006-03-21 | Mold-Masters Limited | Valve-gated injection molding system with side-mounted actuator |
| US7134868B2 (en) | 2003-11-26 | 2006-11-14 | Mold-Masters Limited | Injection molding nozzle with wear-resistant tip having diamond-type coating |
| CN1328027C (en) * | 2004-11-25 | 2007-07-25 | 李尚劼 | Method for processing crystal combination diamond and products thereof |
| DE202007017136U1 (en) * | 2007-12-06 | 2009-04-16 | Günther Heisskanaltechnik Gmbh | Valve needle for a needle valve nozzle |
| US8449287B2 (en) * | 2010-09-10 | 2013-05-28 | Mold-Masters (2007) Limited | Valve pin for accommodating side loading |
| WO2015013392A1 (en) * | 2013-07-23 | 2015-01-29 | Synventive Molding Solutions, Inc. | Two piece valve pin |
| CN104772854A (en) * | 2014-01-15 | 2015-07-15 | 圣万提注塑工业（苏州）有限公司 | Two material injection molding apparatus component and additive manufacturing process therefor |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2273646A1 (en) * | 1974-06-07 | 1976-01-02 | Matra Engins | Chilled runners for injection moulding liquid thermosetting resins - to allow recirculation of resin without precuring |
| JPS61272119A (en) * | 1985-05-27 | 1986-12-02 | Shinagawa Refract Co Ltd | Molding equipment for plastic material |
| DE3833220C2 (en) * | 1988-09-30 | 1998-04-30 | Agfa Gevaert Ag | Needle valve nozzle in an injection mold for processing thermoplastics |
| CA1292848C (en) * | 1989-02-14 | 1991-12-10 | Jobst Ulrich Gellert | Injection molding system having a valve member with a ribbed insulative portion |
| DE4230758A1 (en) | 1992-09-15 | 1994-03-17 | Wolff Hans Martin | Hot runner nozzle with needle valve - connected to centre of operating bar actuated by cylinders in parallel at each end of bar. |
| DE19535717C2 (en) | 1995-09-26 | 1999-11-18 | Michael Blank | Nozzle body for an injection molding nozzle |
| JPH10235683A (en) * | 1997-02-26 | 1998-09-08 | Fuji Seiki Kk | Mold assembly for injection molding |
-
1998
- 1998-08-12 DE DE19836506A patent/DE19836506A1/en not_active Withdrawn
-
1999
- 1999-07-31 AU AU54173/99A patent/AU5417399A/en not_active Abandoned
- 1999-07-31 CN CN99809532A patent/CN1312755A/en active Pending
- 1999-07-31 WO PCT/EP1999/005547 patent/WO2000009311A1/en not_active Application Discontinuation
- 1999-07-31 EP EP99940105A patent/EP1105275A1/en not_active Withdrawn
- 1999-07-31 CA CA002340263A patent/CA2340263A1/en not_active Abandoned
- 1999-07-31 JP JP2000564791A patent/JP2003521392A/en active Pending
-
2002
- 2002-03-08 HK HK02101799.9A patent/HK1040378A1/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JP2003521392A (en) | 2003-07-15 |
| DE19836506A1 (en) | 2000-03-02 |
| EP1105275A1 (en) | 2001-06-13 |
| WO2000009311A1 (en) | 2000-02-24 |
| AU5417399A (en) | 2000-03-06 |
| HK1040378A1 (en) | 2002-06-07 |
| CN1312755A (en) | 2001-09-12 |
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| Date | Code | Title | Description |
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| FZDE | Dead |