WO2019136562A1

WO2019136562A1 - Method and apparatus for cleaning mold vent in mold of injection molding machine

Info

Publication number: WO2019136562A1
Application number: PCT/CA2019/050037
Authority: WO
Inventors: Robert D. Schad
Original assignee: Niigon Machines Ltd
Current assignee: Niigon Machines Ltd
Priority date: 2018-01-10
Filing date: 2019-01-10
Publication date: 2019-07-18
Anticipated expiration: 2020-07-10

Abstract

A method of cleaning a vent in a mold stack of an injection molding machine includes closing the mold stack, the mold stack having at least one mold cavity for receiving injection material to form a molded article, and a vent including a vent passageway in fluid communication with the mold cavity. While the mold stack is closed and the mold cavity is empty of injection material, a first stream of pressurized gas is forced through the vent passageway, the first stream of pressurized gas clearing away debris from the vent.

Description

METHOD AND APPARATUS FOR CLEANING MOLD VENT IN MOLD OF INJECTION MOLDING MACHINE

FIELD

[0001 ] The disclosure relates to methods and apparatuses for cleaning mold vents of molds for an injection molding machine, and methods and apparatuses for producing injection molded articles using molds with such cleaning features.

BACKGROUND

[0002] U.S. Pat. No. U.S. Pat. No. 2,550,140 (Dotson) relates to neck molds used in the press and blow method of making glass containers whose necks are provided exteriorly with projections in the form of threads, annular rings or beads, and the like, for the attachment of closures to the containers. A principal feature of the disclosed invention lies in providing neck molds with venting passages which are small enough to prevent the pressed glass from being forced into them while still permitting entrapped air to escape.

[0003] U.S. Pat. No. 8,709,326 (Sumitomo Heavy Industries) discloses an injection molding machine with a split mold where a gas discharge portion is formed at parting surfaces. Further, the cross-section of a flow passage of the gas discharge portion may be reduced at a predetermined timing after the start of the filling of a molding material. Since the cross-section of the flow passage of the gas discharge portion is reduced after a cavity space starts being filled with a molding material, it may be possible to make the amount of gas, which flows through the gas discharge portion, large until the cross-section of the flow passage of the gas discharge portion is reduced. It may be possible to prevent a foreign material from adhering to the inner peripheral surface of the gas discharge portion.

[0004] U.S. Pat. No. 9,238,321 (Husky Injection Molding Systems Ltd.) purports to disclose a method of cleaning a portion of a mold component, the portion of the mold component including a passage configured, in use, to allow passage of fluid and to prevent passage of melt, the method comprising: entering the mold component into a cleaning configuration, whereby a portion of the passage becomes part of a molding surface; performing a molding cycle to fill in at least the portion of the passage with molding material for incorporation and removal of a residue there from. Also provided is a mold having a first mold half and a second mold half, the halves being movable relative to each other. A mold shut height adjustment apparatus can provide for a change in the mold shut height.

[0005] WP03/033210 (Husky Injection Molding Systems Ltd.) purports to disclose a method and apparatus of using a dry ice blasting system to clean injection molds in and out of the injection molding machines that is easy to use and is particularly well suited to cleaning small mold features such as the vents on molding inserts.

[0006] JP03199023A (Toyo Seikan Kaisha Ltd) discloses an invention with the stated purpose to lessen the frequency of cleaning of an air vent part and improve the productivity by communicating a cavity and an air hole via a narrow air vent formed between split molds. A mold 1 is provided with an air vent mechanism 20, since molten resin injected every quantity from a gate 8 per one cycle completely fills the inner part of a cavity 10 while exhausting air in the cavity 10 to the outside of the mold 1. The constitution of the air vent mechanism 20 is made as an air vent wherein a narrow gap that is capable of letting air escape therefrom, and does not allow the molten resin to invade therein at the joint part with the cavity is formed at the mating part of the mold, and since a screw peripheral part 5a is lowered slightly one step from the mating surface 5b of the mold, extraction of heated air becomes well, resulting in the prevention of foaming at a preform mouth part and the prevention of adhesion of plate out to the air vent part, so that the frequency of cleaning in the mold can be decreased. Moreover, a groove 18 forms a passage 21 to promptly vent air from the air vent 14 to the outside.

SUMMARY

[0007] This summary is intended to introduce the reader to the more detailed description that follows and not to limit or define any claimed or as yet unclaimed invention. One or more inventions may reside in any combination or sub-combination of the elements or process steps disclosed in any part of this document including its claims and figures.

[0008] According to some aspects of the teachings disclosed herein, an injection molding machine, includes (a) a first platen and a second platen, at least one of the first and second platens movable along a machine axis toward and away from the other platen; (b) a mold stack including a mold core half mounted to the first platen and a mold cavity half mounted to the second platen, the mold stack movable between an open position in which the mold core half is spaced apart from the mold cavity half and a closed position in which the mold core half abuts the mold cavity half, the mold stack providing a plurality of enclosed mold cavities when in the closed position; (c) a plurality of mold vents in the mold stack, each mold vent including a vent passageway in fluid communication with a respective mold cavity for venting gas from the respective mold cavity when the mold stack is in the closed position; and (d) at least a first gas delivery apparatus for delivering a first pressurized gas to the mold stack, the first gas delivery apparatus operable in a first mode when the mold stack is closed and the mold cavity is empty of injection material to urge a first stream of pressurized gas through the vent passageways for clearing away debris from the vent passageways. [0009] In some examples, the first gas delivery apparatus provides the first stream of pressurized gas at relatively high pressure, and in some examples, the relatively high pressure is at least 6 bar. In some examples the first stream of pressurized gas is provided at a pressure of between about 6 bar and about 60 bar.

[0010] In some examples, the injection molding machine further includes a cleaning agent distribution apparatus for delivering a cleaning agent to the pressurized gas in the first mode. In some examples, the cleaning agent comprises solid carbon dioxide particles.

[0011 ] In some examples, the first gas delivery apparatus is operable in a second mode to provide a second stream of pressurized gas to the mold stack when the mold is open to facilitate ejection of the molded articles from the mold stack. In some examples, the first gas delivery apparatus provides the second stream of pressurized gas at pressure lower than the pressure of the gas of the first stream. In some examples, the first gas delivery apparatus provides the second stream of pressurized gas at a pressure of between about 5 bar and about 9 bar.

[0012] In some examples, the injection molding machine further includes a second gas delivery apparatus separate from the first gas delivery apparatus, the second gas delivery apparatus delivering a second stream of pressurized gas to the mold stack when the mold is open to facilitate ejection of molded articles from the mold stack. In some examples, the second gas delivery apparatus provides the second stream of pressurized gas at pressure lower than the pressure of the gas of the first stream. In some examples, the second gas delivery apparatus provides the second stream of pressurized gas at a pressure of between about 5 bar and about 9 bar. [0013] In some examples, each mold cavity in the mold stack is further defined by first and second transversely opposed neck ring segments for forming transversely protruding neck features at one end of the respective molded articles, and the vent passageways each comprise a flow gate defined by a gap between opposing shoulder surfaces of the opposed neck ring segments when the mold stack is in the closed position.

[0014] According to some aspects of the teaching disclosed herein, a method of cleaning a vent in a mold stack of an injection molding machine, includes: (a) closing the mold stack, the mold stack having at least one mold cavity for receiving injection material to form a molded article, and a vent comprising a vent passageway in fluid communication with the mold cavity; and (b) while the mold stack is closed and the mold cavity is empty of injection material, forcing a stream of pressurized gas through the vent passageway, the stream of pressurized gas clearing away debris from the vent.

[0015] In some examples, step (b) includes urging pressurized gas into the mold cavity and evacuating pressurized gas from the mold cavity via the first stream of pressurized gas passing through the vent passageway.

[0016] In some examples, the method further includes delivering pressurized gas to a header in the mold stack, the header in fluid communication with the mold cavity. In some examples, a gas supply source configured to facilitate ejection of the molded article from the mold stack during an ejection operation of the injection molding machine is also used to deliver the pressurized gas to the header during a vent cleaning operation of the injection molding machine.

[0017] In some examples, step (b) further includes urging the first stream of pressurized fluid through a flow gate of the vent passageway, the flow gate inhibiting the flow of injection material from the mold cavity into the vent passageway. In some examples, the flow gate includes a narrowed portion in the vent passageway having a passageway height of about 0.03mm. In some examples, the flow gate comprises a gap between opposing surfaces of opposed neck ring segments, the neck ring segments translatable along a transverse slide axis toward and away from the core for forming transversely protruding neck features on the molded article when the mold stack is in the closed position.

[0018] In some examples, the method further includes adding a cleaning agent to the first stream of pressurized gas to facilitate removal of debris from the vent passageway. In some examples, the cleaning agent includes solid carbon dioxide particles entrained in the stream of pressurized gas.

[0019] In some examples, the pressurized gas in the first stream of pressurized gas upstream of the vent has a relatively high pressure. In some examples, the pressurized gas in the first stream of pressurized gas upstream of the vent has a pressure of at least 5 times greater than atmosphere, and in some examples, has a pressure of between about 6 bar and about 60 bar.

[0020] In some examples, the stream of pressurized gas flows through the vent at a relatively high speed, and/or for a relatively short duration, or both for a short duration and at a high pressure (i.e. a short burst of high speed gas flow). In some examples, the relatively short duration of the pressurized gas flow through the vent during a cleaning cycle is less than 2.0 sec. In some examples, the relatively high speed of the pressurized through the vent during a cleaning cycle is at least 100 m/s.

DRAWINGS

[0021 ] The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the teaching of the present specification and are not intended to limit the scope of what is taught in any way.

[0022] In the drawings: [0023] Figure 1 is an elevation view of a portion of an injection molding machine viewed from the operator side;

[0024] Figure 2 is a side view of an article formed by the machine of Figure

1 ;

[0025] Figure 3 is an enlarged cross-sectional view of a portion of the machine of Figure 1 , taken in a vertical plane aligned with an axis of the article of Figure 2 being formed thereby;

[0026] Figure 4 is an enlarged view of a portion of the structure of Figure 3;

[0027] Figure 5 is a cross-sectional view of the structure of 4, taken along the lines 4-4;

[0028] Figure 6A is an enlarged portion of the structure of Figure 5;

[0029] Figure 6B shows the structure of Figure 6A but with neck ring segments in a retracted position; and

[0030] Figure 7 is a view of the structure of Figure 6B along the direction of lines 7-7.

DETAILED DESCRIPTION

[0031 ] Various apparatuses or processes will be described below to provide an example of an embodiment of each claimed invention. No embodiment described below limits any claimed invention and any claimed invention may cover processes or apparatuses that differ from those described below. The claimed inventions are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses described below. It is possible that an apparatus or process described below is not an embodiment of any claimed invention. Any invention disclosed in an apparatus or process described below that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim or dedicate to the public any such invention by its disclosure in this document.

[0032] Referring to Figure 1 , an example of an injection molding machine 100 includes a first platen 106 and a second platen 108. At least one of the first and second platens is movable along a machine axis 104 toward and away from the other platen. In the example illustrated, the platens 106, 108 are supported on a machine base 102. The first platen 106 is movable relative to the machine base along the machine axis 104 and is also referred to as moving platen 106. The second platen 108 is, in the example illustrated, fixed relative to the base 102 and is also referred to as stationary platen 108.

[0033] The injection molding machine 100 further includes a mold stack 110 including a mold core half 106a mounted to the first platen 106 and a mold cavity half 108a mounted to the second platen 108. The mold stack 110 is movable between an open position and a closed position. When the mold stack 110 is in the open position, the first platen 106 is retracted away from the second platen 108 and the mold core half 106a is spaced apart from the mold cavity half 108a. When the mold stack 110 is in the closed position, the first platen 106 is advanced toward the second platen 108 and the mold core half 106a abuts the mold cavity half 108a.

[0034] With reference to Figure 3, the mold stack 110 provides a plurality of enclosed mold cavities 112 when in the closed position. In the present example, the mold stack 110 provides 48 mold cavities 112, but the number of mold cavities can range from 24 to 96 or more. Each enclosed mold cavity 112 is formed in part by a mold core 114 provided on the mold core half 106a and a mold recess 116 provided on the mold cavity half 108a. The mold cores 114 and mold recesses 116 inter-engage when the mold stack 110 is in the closed position to form outer and inner surfaces of the article to be molded. An injection unit 118 is mounted to the machine base 102 for injecting resin or other mold material into the mold cavities 112 to form molded articles corresponding to the shape of the mold cavities 112.

[0035] Referring to Figure 2, in the example illustrated, the injection molding machine 100 is set up for producing molded articles in the form of preforms 122 that can be used as input material for subsequent processing, for example, a blow molding operation to produce beverage containers. With reference to Figure 2, an example preform 122 comprises a generally elongate tubular article extending along a preform axis 124. The preform 122 includes a preform open end 126 and a preform closed end 128 opposite the preform open end 126.

[0036] The preform 122 has a preform neck with transversely protruding neck features 130 adjacent the preform open end 126. In the example illustrated, the neck features 130 include external threads 132 for receiving a closure, such as a cap having complimentary internal threads, and a radially outwardly extending annular flange 134. The flange 134 is, in the example illustrated, adjacent the threaded portion 132, with the threaded portion 132 disposed axially between the preform open end 126 and the flange 134.

[0037] Referring to Figures 4 and 5, in the example illustrated, each mold cavity 112 in the mold stack 110 is further defined by a pair of neck ring segments 140 including first and second transversely opposed neck ring segments 140a, 140b for forming the neck features 130. Each neck ring segment 140a, 140b has a respective front face 142a, 142b directed towards the mold cavity 112. Each front face 142a, 142b includes a generally concave center portion 144a, 144b, with a profile shaped to form the neck features, and generally flat shoulder surfaces disposed on either side of the concave center portion, the shoulder surfaces including opposed first shoulder surfaces 146a, 146b on one side of the center portions and opposed second shoulder surfaces 148a, 148b on the other side of the center portions.

[0038] The neck ring segments 140a, 140b can move toward and away from each other in a direction generally perpendicular to the preform axis, between advanced and retracted positions. When the mold stack 110 is in the closed position (Figure 6A), the neck ring segments are in the advanced position, and the shoulder surfaces 146a, 148a of one neck ring segment 140a, abut the opposing shoulder surfaces 146b, 148b of the other, opposed neck ring segment 140b. When the mold stack 110 is in the open position (Figure 6B), the neck ring segments 140 are in the retracted position and the preform 122, and particularly the neck ring features 130, can move along the preform axis between the opposed front faces 142a, 142b of the neck ring segments 140a, 142b for ejection of the preforms from the mold stack 110.

[0039] Referring to Figures 6A, 6B, and 7, the mold stack 110 further includes a plurality of mold vents 150 in the mold stack 110. Each mold vent 150 includes a vent passageway 152 in fluid communication with a respective mold cavity 112 for venting effluent from the respective mold cavity 112 to atmosphere when the mold stack 110 is in the closed position. The effluent includes air that is present in the cavities when the mold stack moves from the open to the closed position and which must be displaced from the cavity 112 as the cavity 112 is filled with injection material (e.g. molten resin). The effluent also typically includes other gases and matter, such as volatile organic compounds and/or fine particulate entrained in the gas, some of which can be generated in front of the hot, molten injection material as it flows into the mold cavity.

[0040] The vents 150 are configured to permit passage of the effluent through the vent passageway 152, but to inhibit passage of the injection material when the mold stack is in the closed position. In the example illustrated, each vent passageway 152 includes a flow gate 154 defined by a gap 156 between opposed shoulder surfaces of the neck ring segments when the mold stack is in the closed position, the flow gate 154 having an inner (upstream) end 160 open to the mold cavity and an outer (downstream) end 162 open to an evacuation conduit 164 provided between the opposed shoulder surfaces 146a, 146b of the neck ring segments 140a, 140b and adjacent the flow gate 154.

[0041 ] The flow gate 154 corresponds to a narrowed portion of the vent passageway 152, and in the example illustrated is defined by a recessed portion 166 of the shoulder surface 146a of the first neck ring segment 140a, the recessed portion 166 disposed laterally inwardly (toward the core 114) of a non-recessed portion 168 of the shoulder surface 146a. The non-recessed portion 168 of the shoulder surface is configured to bear against the opposed shoulder surface 146b of the other neck ring segment 140b when the mold stack 110 is in the closed position, and is also referred to as seal surface 168.

[0042] In the example illustrated, the recessed portion 166 of the shoulder surface 146a is shy of, or set back from, the non-recessed portion 168 of the shoulder surface by a distance corresponding to the gap height 156, and the gap height 156 is, in the example illustrated, about 0.03mm. The evacuation conduit 164 includes, in the example illustrated, a groove 169 provided in the shoulder surface 146a and extending along a boundary between the recessed portion 166 and the non-recessed portion 168 (see Fig. 6B).

[0043] During operation of the machine 100, the vents 150, and particularly the flow gates 154, can get plugged. This can undesirably result in equipment malfunctions and defective parts. Manually cleaning the vents 150 can be time- consuming and can risk damaging the mold surfaces. Aspects of the teaching disclosed herein can facilitate automatic cleaning of the vents 150. [0044] In the example illustrated, the injection molding machine 100 further includes at least a first gas delivery apparatus 170 for delivering a first stream 172 of pressurized gas to the mold stack 110. The first gas delivery apparatus 170 is operable in at a least a first mode, when the mold stack 110 is in the closed position and the mold cavities 112 are empty of injection material, to urge the first stream 172 of pressurized gas through the vent passageways 152 for clearing away debris from the vent passageways 152 and the flow gates 154 thereof.

[0045] In the example illustrated, the first gas delivery apparatus 170 includes a first source of pressurized gas 174 and a first delivery conduit network 176 extending between the first source of pressurized gas 174 and the mold cavities 112. In the example illustrated, the first delivery conduit network 176 includes at least one delivery header 178 in the mold stack 110, the delivery header 178 in fluid communication with respective ones of the mold cavities 112.

[0046] The first gas delivery apparatus 170 is typically configured to provide the first stream 172 of pressurized gas at a high pressure. For example, the pressure of the first stream of pressurized gas is higher than atmospheric pressure and in some examples is higher (in some cases a multiple of times higher) than standard shop air pressure (standard shop air pressure being around 6 bar). In the example illustrated, the first gas delivery apparatus 170 includes a pressure booster 180 having an inlet port 182 for receiving gas at a pressure of about 6 bar and an outlet port 184 downstream of the inlet port for delivering gas at a higher pressure.

[0047] In the example illustrated, the injection molding machine 100 further includes an optional cleaning agent distribution apparatus 186 for delivering a cleaning agent 188 to the first stream 172 of pressurized gas in the first mode. In the example illustrated, the cleaning agent 188 comprises solid carbon dioxide particles. [0048] The injection molding machine 100 further is, in the example illustrated, configured to provide an optional second stream 192 of gas to each mold cavity 112 when the mold stack 110 is in the open position to facilitate ejection of the molded articles (i.e. preforms 122) from the mold stack 110. In some examples, the gas of the second stream of pressurized gas has a pressure that is lower than the pressure of the first stream of pressurized gas.

[0049] In some examples, the second stream 192 of pressurized gas is provided by operation of the first gas delivery apparatus 170 in a second mode. In the example illustrated, the second stream of gas 192 is provided by an optional second gas delivery apparatus 190 separate from the first gas delivery apparatus 170.

[0050] More specifically, in the example illustrated, the injection molding machine 100 further includes an optional second gas delivery apparatus 190 separate from the first gas delivery apparatus 192, the second gas delivery apparatus 190 delivering pressurized gas to the mold stack 110 to facilitate ejection of molded articles from the mold stack 110 via respective second streams 192 of pressurized gas. In some examples, the second gas delivery apparatus 190 provides the second stream 192 of pressurized gas at a pressure that is lower than the pressure of the first stream of pressurized gas.

[0051 ] Further details of a method of cleaning the vent 150 in the mold stack 110 of the injection molding machine 100 are described as follows. To initiate cleaning, the mold stack is moved to the closed position, providing a plurality of the generally enclosed mold cavities 112.

[0052] While the mold stack 110 is closed and the mold cavities 112 are empty of injection material, a first stream 172 of pressurized gas is urged through the vent passageway 152. The first stream 172 of pressurized gas clears away debris from the vent 150. More particularly, in the example illustrated, the first stream 172 of pressurized fluid is urged through the flow gate 154 of the vent passageway 152, to clear debris away from the flow gate 154 of the vent 150.

[0053] Furthermore, in the example illustrated, pressurized gas is urged into each mold cavity 110 and then evacuated from the mold cavities via the first stream of pressurized gas passing through the vent passageway. In some examples, pressurized is gas is delivered to a header 178 in the mold stack, and the gas then flows from the header to the mold cavities.

[0054] In some examples, a gas supply source is configured to facilitate ejection of the molded articles from the mold stack 110 during an ejection operation of the injection molding machine, and in some examples this same gas supply source is also used to also deliver the pressurized gas to the header during a vent cleaning operation of the injection molding machine.

[0055] In the example illustrated, the method of cleaning the vent 150 includes leaving a gap 154 between opposed surfaces of the neck ring segments when the neck ring segments have been moved toward each other to place the mold stack in the closed position, the gap defining a narrowed portion of the vent passageway.

[0056] In the example illustrated, an optional cleaning agent is added to the stream of pressurized gas to facilitate removal of debris from the vent passageway. The cleaning agent, in the example illustrated, is in the form of solid carbon dioxide particles.

Claims

What is claimed is:

1. An injection molding machine, comprising:

a) a first platen and a second platen, at least one of the first and second platens movable along a machine axis toward and away from the other platen;

b) a mold stack including a mold core half mounted to the first platen and a mold cavity half mounted to the second platen, the mold stack movable between an open position in which the mold core half is spaced apart from the mold cavity half and a closed position in which the mold core half abuts the mold cavity half, the mold stack providing a plurality of enclosed mold cavities when in the closed position; c) a plurality of mold vents in the mold stack, each mold vent including a vent passageway in fluid communication with a respective mold cavity for venting gas from the respective mold cavity to atmosphere when the mold stack is in the closed position; and

d) at least a first gas delivery apparatus for delivering a first pressurized gas to the mold stack, the first gas delivery apparatus operable in a first mode when the mold stack is closed and the mold cavity is empty of injection material to urge a first stream of pressurized gas through the vent passageways for clearing away debris from the vent passageways.

2. The injection molding machine of claim 2, wherein the first gas delivery apparatus provides the first stream of pressurized gas at a pressure of between about 6 bar and about 60 bar.

3. The injection molding machine of any one of claims 1 to 2, further comprising a cleaning agent distribution apparatus for delivering a cleaning agent to the pressurized gas in the first mode.

4. The injection molding machine of claim 3, wherein the cleaning agent comprises solid carbon dioxide particles.

5. The injection molding machine of any one claims 1 to 4, wherein the first gas delivery apparatus is operable in a second mode to provide a second stream of pressurized gas to the mold stack when the mold is open to facilitate ejection of the molded articles from the mold stack.

6. The injection molding machine of claim 5, wherein the first gas delivery apparatus provides the second stream of pressurized gas at a pressure of between about 5 bar and about 9 bar.

7. The injection molding machine of any one of claims 1 to 4, further comprising a second gas delivery apparatus separate from the first gas delivery apparatus, the second gas delivery apparatus delivering pressurized gas to the mold stack to facilitate ejection of molded articles from the mold stack via respective second streams of pressurized gas.

8. The injection molding machine of claim 7, wherein the second gas delivery apparatus provides the second stream of pressurized gas at a pressure of between about 5 bar and about 9 bar.

9. The injection molding machine of any one of claims 1 to 8, wherein each mold cavity in the mold stack is further defined by first and second transversely opposed neck ring segments for forming transversely protruding threads at one end of the respective molded articles, and wherein the vent passageways each comprise a flow gate defined by a gap between opposing shoulder surfaces of the opposed neck ring segments when the mold stack is in the closed position.

10. A method of cleaning a vent in a mold stack of an injection molding machine, comprising:

a) closing the mold stack, the mold stack having at least one mold cavity for receiving injection material to form a molded article, and a vent comprising a vent passageway in fluid communication with the mold cavity; and

b) while the mold stack is closed and the mold cavity is empty of injection material, forcing a stream of pressurized gas through the vent passageway, the stream of pressurized gas clearing away debris from the vent.

11. The method of claim 10, wherein step (b) comprises urging pressurized gas into the mold cavity and evacuating pressurized gas from the mold cavity via the stream of pressurized gas passing through the vent passageway.

12. The method of claim 11 , further comprising delivering pressurized gas to a header in the mold stack, the header in fluid communication with the mold cavity.

13. The method of claim 12, comprising using a gas supply source configured to facilitate ejection of the molded article from the mold stack during an ejection operation of the injection molding machine to also deliver the pressurized gas to the header during a vent cleaning operation of the injection molding machine.

14. The method of any one of claims 10 to 13, wherein step (b) includes urging the stream of pressurized fluid through a flow gate of the vent passageway, the flow gate inhibiting the flow of injection material from the mold cavity into the vent passageway.

15. The method of claim 14, wherein the flow gate comprises a narrowed portion in the vent passageway having a passageway height of about 0.03mm.

16. The method of claim 15, wherein the flow gate comprises a gap between opposed surfaces of a neck ring and a mold core, the neck ring translatable along a transverse slide axis toward and away from the core for forming transversely protruding neck features on the molded article when the mold stack is in the closed position.

17. The method of any one of claims 10 to 16, wherein a cleaning agent is added to the stream of pressurized gas to facilitate removal of debris from the vent passageway.

18. The method of claim 17, wherein the cleaning agent comprises solid carbon dioxide particles entrained in the stream of pressurized gas.

19. The method of any one of claims 10 to 18, wherein the pressurized gas in the stream of pressurized gas upstream of the vent has a relatively high pressure, in particular a pressure at least 5 times greater than atmosphere, and/or a pressure of between about 6 and about 60 bar.

20. The method of any one of claims 10 to 19, wherein the stream of pressurized gas flows through the vent for a relatively short duration, at a relatively high speed, or both for a relatively short duration and at a relatively high speed, a particular relatively short duration being less than 2.0 sec, and a particular relatively high speed being at least 100 m/s.