High-resolution temperature control at sprue bushing-mold interior interface for injection molding of chalcogenide glasses

Abstract

A method for forming a precision optical element via injection molding is disclosed. The method comprises heating chalcogenide glass to form a glass melt and directing the glass melt along a passage from an injection device into a mold cavity of a mold that negatively defines the precision optical element. The passage comprises a nozzle passage defined by the injection device, a runner passage defined by a mold interior of the mold, and a sprue passage defined by a heated sprue bushing disposed in the mold. The method further comprises solidifying the glass melt in the mold to form the precision optical element and a runner element corresponding to the runner passage, and then ejecting the precision optical element and the runner element therefrom. The method further comprises heating a first portion of the sprue passage proximate the runner passage such that the solidified glass therein releases completely therefrom.

Description

HIGH-RESOLUTION TEMPERATURE CONTROL AT SPRUE BUSHING-MOLDINTERIOR INTERFACE FOR INJECTION MOLDING OF CHALCOGENIDE GLASSESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 63 / 603,408 filed November 28, 2023, the content of which is incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates to glass injection molding. In particular, the present disclosure relates to processes and equipment for the inj ection molding of chalcogenide glasses.BACKGROUND

[0003] Injection molding machines for making molded parts from polymers typically utilize two-part molds, having mold cavities formed therein, that can be separated to remove the molded part. The polymer molding material is heated to a molten state and forced through a passageway consisting of the injection device nozzle, sprue bushing, runner, and gate and into the mold cavity. Once the mold cavity is filled with molten material it is cooled so that the molded part solidifies. The two-part mold is then opened, and the molded part removed in the usual manner. This process requires that at some point along the passageway there be a cold / hot junction, one side of which the material solidifies along with the cooling part and the other side of which the material remains molten. This cold / hot junction is typically provided by means of a sprue bushing having an entry hole that forms a portion of the hot portion of the passageway and a smaller tapered hole in intersection with the entry hole that forms a portion of the cold portion of the passageway. This tapered hole leads into a runner portion of the passageway that leads directly to the mold cavity.

[0004] After the molded part is cooled, it has attached thereto the material from the runner and the tapered hole. When the molded part is ejected, the material from the tapered hole is typically configured to be pulled from the sprue bushing and ejected with molded part and the runner. However, the ease in which the material pulled from the sprue bushing releases from the sprue bushing depends on the type of material and other processing parameters, such as the temperature of the sprue bushing. The temperature of the sprue bushing depends on its type. Ingeneral, there are two types of sprue bushings: hot or heated sprue bushings and cold sprue bushings. A heated sprue bushing includes some form of supplemental heating, such as an external heating coil disposed around a peripheral portion of the sprue bushing. This supplemental heating enables the temperature of the hot sprue bushing to be higher than the region of the mold into which the hot sprue bushing is mounted. In contrast, a cold sprue bushing lacks any supplemental heating such that it assumes the temperature of the region of the mold into which the cold sprue bushing is mounted.

[0005] Applicant has developed processes and equipment for the injection molding of chalcogenide glasses. Chalcogenide glasses are non-oxide glasses that include one or more of the chalcogen elements (e.g., Group VIA elements, CAS nomenclature) sulfur (S), selenium (Se), and tellurium (Te) and one or more metals and / or semi-metals (e.g., metalloids). Though chalcogenide glasses have glass transition temperatures that are reasonably compatible with polymer-based injection molding systems, chalcogenide glasses (like most glasses) have steep viscosity curves such that even small variations in temperature can have drastic effects on the flow of the glass. This sensitivity of chalcogenide glasses to temperature exists throughout the entire injection molding system from the feedstock hopper to the mold cavities.

[0006] One issue with the injection molding of chalcogenide glasses relates to the transition from the injection system to the mold at the sprue bushing. Chalcogenide glass is very brittle and hard near the transition temperature, leading to breakage and non-release from existing cold sprue bushings that lack supplemental heating. Existing heated sprue bushings may not possess the thermal control and structural characteristics needed to minimize turbulence- induced defects, such as excessive bubbles within the molded parts, and complete allow nondestructive release of the material from the sprue.

[0007] Consequently, it would be advantageous to develop systems and methods for injection molding chalcogenide glass using heated sprue bushings with high-resolution temperature control at the sprue bushing-mold interior interface to overcome the aforementioned issues.SUMMARY

[0008] The following summary is a brief description of certain aspects of the present disclosure. The summary should not be considered as limiting of the breadth, scope, or applicability of the present disclosure.

[0009] According to aspect (1), a method for forming a precision optical element via injection molding is provided. The method comprises: heating, in an injection device, particles of chalcogenide glass to form a glass melt, the chalcogenide glass having a IO40P temperature of 500 °C or less and being resistant to crystallization at a shear rate in the range of 1,000 sec'1to 10,000 sec'1; directing the glass melt along a passage from the injection device into a mold cavity of a mold that negatively defines the precision optical element, the passage comprising: a nozzle passage through which the glass melt is configured to be directed from the injection device, the nozzle passage defined by the injection device, a runner passage through which the glass melt is configured to be directed into the mold cavity, the runner passage defined by a mold interior of the mold, and a sprue passage through which the glass melt is configured to be directed from the nozzle passage to the runner passage, the sprue passage defined by a heated sprue bushing that extends through the mold from the mold interior to a mold exterior that is separated from the mold interior; solidifying the glass melt within the mold interior to form (i) the precision optical element from the solidified glass in the mold cavity and (ii) a runner element from the solidified glass in the runner passage; ejecting the precision optical element and the runner element from the mold; and heating, with a first heater, a first sprue passage portion of the sprue passage proximate the runner passage such that when the runner element is ejected from the mold, the solidified glass within the first sprue passage portion is configured to release completely therefrom and eject with the runner element.

[0010] According to aspect (2), the method of aspect (1) is provided, wherein the heated sprue bushing has a first sprue bushing portion that defines the first sprue passage portion, and wherein heating the first sprue passage portion comprises varying a heating rate of the first heater so that the first sprue bushing portion has a first setpoint temperature concurrently with the ejecting.

[0011] According to aspect (3), the method of aspect (2) is provided, further comprising heating, with a second heater, a second sprue passage portion of the sprue passage proximate the nozzle passage such that the glass melt in the second sprue passage portion remains in liquid form.

[0012] According to aspect (4), the method of aspect (3) is provided, wherein the sprue passage comprises a narrowing transition that separates the first sprue passage portion from the second sprue passage portion.

[0013] According to aspect (5), the method of aspect (4) is provided, wherein the heated sprue bushing has a second sprue bushing portion that defines the second sprue passage portion, and wherein heating the second sprue passage portion comprises maintaining the second sprue bushing portion at a second setpoint temperature.

[0014] According to aspect (6), the method of aspect (5) is provided, wherein the first setpoint temperature is greater than or equal to the second setpoint temperature.

[0015] According to aspect (7), the method of aspect (5) is provided, wherein the first setpoint temperature is at least 10 °C greater than the second setpoint temperature.

[0016] According to aspect (8), the method of any one of aspects (1) to (7) is provided, wherein the mold comprises (i) a first mold half that is fixed in position relative to the injection device and (ii) a second mold half configured to translate relative to the first mold half, the heated sprue bushing disposed in the first mold half.

[0017] According to aspect (9), the method of aspect (8) is provided, wherein the second mold half is configured to translate between (i) a clamped position, during the directing and the solidifying, in which the second mold half is pressed against the first mold half and (ii) an open position, during the ejecting, in which the second mold half is spaced from the first mold half.

[0018] According to aspect (10), the method of any one of aspects (1) to (9) is provided, wherein the sprue passage is configured to be continuous along an entire length thereof between the mold exterior and the mold interior.

[0019] According to aspect (11), the method of any one of aspects (1) to (10) is provided, further comprising: prior to the directing, building a shot volume of the glass melt under a first pressure in the injection device; and after the shot volume is built, applying a second pressure that is greater than the first pressure to the shot volume for a first duration in the injection device to degas the glass melt.

[0020] According to aspect (12), an injection molding system is provided. The injection molding system comprises: an injection device configured heat particles of chalcogenide glass to form a glass melt, the chalcogenide glass having a IO40P temperature of 500 °C or less and being resistant to crystallization at a shear rate in the range of 1,000 sec'1to 10,000 sec'1, the injection device comprising a nozzle that defines a nozzle passage through which the glass melt is configured to be directed from the injection device; a mold having a mold exterior and a mold interior separated from the mold exterior, the mold interior defining a mold cavity and arunner passage through which the glass melt is configured to be directed into the mold cavity, the mold cavity configured to negatively define a precision optical element; a heated sprue bushing extending through the mold from the mold exterior to the mold interior, the heated sprue bushing defining a sprue passage through which the glass melt is configured to be directed from the nozzle passage to the runner passage; a controller configured to operate the injection molding system to: direct the glass melt from the injection device along the nozzle passage, the sprue passage, and the runner passage and into the mold cavity, solidify the glass melt within the mold interior to form (i) the precision optical element from the solidified glass in the mold cavity and (ii) a runner element from the solidified glass in the runner passage, and eject the precision optical element and the runner element from the mold; and a first heater configured to heat a first sprue passage portion of the sprue passage proximate the runner passage such that when the runner element is ejected from the mold, the solidified glass within the first sprue passage portion is configured to release completely therefrom and eject with the runner element.

[0021] According to aspect (13), the injection molding system of aspect (12) is provided, wherein: the heated sprue bushing has a first sprue bushing portion that defines the first sprue passage portion, the injection system further comprises a first sensor configured to detect a first temperature of the first sprue bushing portion, the controller is configured to (i) receive the first temperature from the first sensor, (ii) compare the first temperature to a first setpoint temperature, and (iii) generate a first command based on the comparison, and the first heater is configured to receive the first command and vary a heating rate of the first heater so that the first sprue bushing portion has the first setpoint temperature concurrently with the ejecting.

[0022] According to aspect (14), the injection molding system of aspect (13) is provided, further comprising a second heater configured to heat a second sprue passage portion of the sprue passage proximate the nozzle passage such that the glass melt in the second sprue passage portion remains in liquid form.

[0023] According to aspect (15), the injection molding system of aspect (14) is provided, wherein the sprue passage comprises a narrowing transition that separates the first sprue passage portion from the second sprue passage portion.

[0024] According to aspect (16), the injection molding system of aspect (15) is provided, wherein: the heated sprue bushing has a second sprue bushing portion that defines the second sprue passage portion, the injection system further comprises a second sensor configured todetect a second temperature of the second sprue bushing portion, the controller is configured to (i) receive the second temperature from the second sensor, (ii) compare the second temperature to a second setpoint temperature, and (iii) generate a second command based on the comparison, and the second heater is configured to receive the second command and maintain the second sprue bushing portion at the second setpoint temperature.

[0025] According to aspect (17), the injection molding system of aspect (16) is provided, wherein the first setpoint temperature is greater than or equal to the second setpoint temperature.

[0026] According to aspect (18), the injection molding system of aspect (16) is provided, wherein the first setpoint temperature is at least 10 °C greater than the second setpoint temperature.

[0027] According to aspect (19), the injection molding system of any one of aspects (12) to (18) is provided, wherein the mold comprises (i) a first mold half that is fixed in position relative to the injection device and (ii) a second mold half configured to translate relative to the first mold half, the heated sprue bushing disposed in the first mold half.

[0028] According to aspect (20), the injection molding system of aspect (19) is provided, wherein the second mold half is configured to translate between (i) a clamped position, when the glass melt is directed from the injection device and solidified within the mold interior, in which the second mold half is pressed against the first mold half and (ii) an open position, when the precision optical element and the runner element are ejected from the mold, in which the second mold half is spaced from the first mold half.

[0029] According to aspect (21), the injection molding system of any one of aspects (12) to (20) is provided, wherein the sprue passage is configured to be continuous along an entire length thereof between the mold exterior and the mold interior.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a schematic representation of an injection molding system configured to form a precision optical element from chalcogenide glass;

[0031] FIG. 2 is a schematic cross-sectional view of an injection device and a fixed mold half of the injection molding system of FIG. 1;

[0032] FIG. 3A is an enlarged schematic cross-sectional view of the fixed mold half of FIG. 2 that shows a heated sprue bushing with a first configuration of heaters;

[0033] FIG. 3B is a front schematic view of the fixed mold half of FIG. 3 A, showing a central region thereof in the direction of arrow 302 (FIG. 3 A);

[0034] FIG. 4 is an enlarged schematic cross-sectional view of the fixed mold half of FIG. 2 that shows a heated sprue bushing with a second configuration of heaters; and

[0035] FIG. 5 is an enlarged schematic cross-sectional view of the fixed mold half of FIG. 2 that shows a heated sprue bushing with a thermal isolation member.DETAILED DESCRIPTION

[0036] For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the disclosure is thereby intended. It is further understood that the present disclosure includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles disclosed herein as would normally occur to one skilled in the art to which this disclosure pertains.

[0037] As used herein, the term “and / or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0038] In this document, relational terms, such as first and second, top and bottom, and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions.

[0039] As used herein, the term “about” means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and / or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in theart. When the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to. Whether or not a numerical value or end-point of a range in the specification recites “about,” the numerical value or end-point of a range is intended to include two embodiments: one modified by “about,” and one not modified by “about.” It will be further understood that the end-points of each of the ranges are significant both in relation to the other end-point, and independently of the other end-point.

[0040] Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range was explicitly recited. As an illustration, a numerical range of “about 1 to about 5” should be interpreted to include not only the explicitly recited values of about 1 to about 5, but also to include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3, and 4, the sub ranges such as from 1-3, from 2-4, from 3-5, etc., as well as 1, 2, 3, 4, and 5 individually. The same principle applies to ranges reciting only one numerical value as a minimum or maximum. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described by the range.

[0041] The terms “substantial,” “substantially,” and variations thereof as used herein, unless defined elsewhere in association with specific terms or phrases, are intended to note that a described feature is equal or approximately equal to a value or description. For example, a “substantially planar” surface is intended to denote a surface that is planar or approximately planar. Moreover, “substantially” is intended to denote that two values are equal or approximately equal. In some embodiments, “substantially” may denote values within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0042] Directional terms as used herein — for example up, down, right, left, front, back, top, bottom, above, below, and the like — are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0043] As used herein the terms "the," "a," or "an," mean "at least one," and should not be limited to "only one" unless explicitly indicated to the contrary. Thus, for example, referenceto "a component" includes embodiments having two or more such components unless the context clearly indicates otherwise.

[0044] As used herein, the term “chalcogenide glass” means a non-oxide glass that includes one or more of the chalcogen elements sulfur (S), selenium (Se), and tellurium (Te) and one or more metals and / or semi-metals (e.g., metalloids). Chalcogenide glasses generally transmit electromagnetic radiation (light) in the 500-20,000 nm (0.5-20 pm) range of the infrared (IR) spectrum.

[0045] As used herein, the terms “hot-melt processing,” “hot-melt processes,” or the like refer to any process that involves heating the chalcogenide glass above its glass transition temperature (Tg) and applying pressure to the (molten) chalcogenide glass to form it into a glass article of interest. Examples of hot-melt processing include injection molding, extrusion, and transfer molding.

[0046] As used herein, the terms “10,000 poise temperature,” “10,000 P temperature,” “IO40P temperature,” or the like refer to a temperature at which glass has a viscosity of 10,000 P. The IO40P temperature is an approximate estimate of the temperature at which a glass can be worked according to the processes disclosed herein. The 104 0P temperature varies with the materials in the glass and can be determined using techniques known in the art. In embodiments, the chalcogenide glasses disclosed herein have IO40P temperatures of 500 °C or less, or preferably of 400 °C or less, which enables these glasses to be injection molded using equipment typically configured for hot-melt processing of polymer materials.

[0047] As used herein, the term “crystallization” refers to the formation of crystals or solid phases where the constituents of a material are arranged in a highly ordered microscopic structure. As used herein, the term “shear thickening” and “shear-induced crystallization” refer to the crystallization of a (fluid) material whose viscosity increases when the material is under (increasing) shear stress. As used herein, the term “shear thinning” refers to the behavior of a (fluid) material whose viscosity decreases when the material is under (increasing) shear stress. Shear thickening and shear thinning can exist under a constant temperature. In embodiments, crystallization is undesirable in the chalcogenide glass and methods disclosed herein. In embodiments, the chalcogenide glass disclosed herein is resistant to shear thickening during processing, particularly hot-melt processing during which the chalcogenide glass (e.g., molten chalcogenide glass) can be subjected to shear rates in a range of from about 1,000 sec'1to about10,000 sec1at temperatures common for such hot-melt processing (e.g., .from about 250 °C to about 500 °C or higher).

[0048] As used herein, the term “glass transition temperature” (Tg) of a material refers to the temperature at which glass transition occurs in an amorphous material. At temperatures below Tg, the material exists in a solid state whereas, at temperatures above Tg, the material exists in a molten state. Tgis lower than the melting temperature of a material in its crystalline state if a crystalline state exists for the material.

[0049] An injection molding system 100 configured to form a precision optical element from chalcogenide glass is now described with reference to FIGS. 1, 2, 3A, and 3B. The injection molding system 100 includes an injection unit 200, a mold 300, a clamping system 400, and a controller 500. The injection unit 200 comprises an injection device 204 configured to plasticize chalcogenide glass and inject the plasticized chalcogenide glass into the mold 300. In embodiments, the injection device 204 can be configured to plasticize and inject the chalcogenide glass by the “ram” process, the “screw” process, or a “screw-ram” process.

[0050] In the ram process, each stroke of a plunger pushes unmelted material into a heated cylinder, which in turn forces molten material at the front of the cylinder out through a nozzle and into a mold with one or more cavities configured in the shape of the part to be molded. In the screw process, unmelted granular material is conveyed forward, through a heated cylinder, by the rotation of an auger-type element. The material is converted to a viscous melt by the action of friction and heat conducted from the cylinder. The molten material, in front of the screw, is injected into a mold by translation / reciprocation of the screw itself. Similar to the mold in the ram process, the mold in the screw process has one or more cavities configured in the shape of the part to be molded.

[0051] Referring now to FIG. 2, an embodiment of the injection device 204 configured to plasticize and inject the chalcogenide glass using the screw-ram process is shown. As shown in FIG. 2, unmelted granular material is conveyed forward, through a heated cylinder 208, by the rotation of an auger-type element or screw 212. Similar to the screw process, the material is converted to a viscous melt by the action of friction from the screw 212 and heat conducted from the cylinder 208. However, the screw 212 used in the screw-ram process is substantially stationary, and the screw 212 is not used to inject the viscous melt into the mold 300. Instead, the molten material in front of the screw is directed to a separate cylinder 216 by the action of the screw 212 until a plunger 220 is compressed rearward in the separate cylinder 216 with apredetermined shot volume of the viscous melt. Thereafter, the plunger 220 is actuated to inject the molten material into the mold 300. In an exemplary embodiment, a screw-ram type injection molding system is preferred due to the better mixing and process consistency of the screw-ram process. In embodiments, the injection device 204 comprises a nozzle 232 that defines a nozzle passage 236 through which the glass melt is configured to be directed or discharged from the injection device 204.

[0052] Referring now to FIG. 1, the injection unit 200 comprises a feed device 224 configured to deliver or feed particles of chalcogenide glass to the injection device 204 through a feed port 228 (FIG. 2) in the injection device 204. In embodiments, the feed device 224 is configured to condition the particles of chalcogenide glass prior to delivering them to the injection device 204. For example, the particles of chalcogenide glass can be configured to dry at the bottom of the feed device 224 at drying temperature (e.g., a drying temperature between about 100 °C and about 140 °C, between about 110 °C and about 130 °C, or at about 120 °C) for a drying duration (e.g., a drying duration of about 5 hours, about 4 hours, about 3 hours, or about 2 hours). In embodiments, the particles of chalcogenide glass can be degassed in the feed device 224 prior to delivering them to the injection device 204.

[0053] The injection device 204 is configured heat the particles of chalcogenide glass to form a glass melt. In embodiments, the chalcogenide glass comprises a glass composition that has a IO4 0P temperature of 500 °C or less (e.g., 400 °C or less) and is resistant to crystallization at a shear rate in the range of 1,000 sec'1to 10,000 sec'1. The temperature of 500 °C or less corresponds to approximate maximum working temperatures of the injection molding system 100 according to embodiments. The temperature of 500 °C or less also corresponds to approximate maximum working temperatures of commercially available injection molding equipment. The shear rate in the range of 1,000 sec'1to 10,000 sec'1corresponds to the approximate shear rate that the glass melt can be exposed to during injection molding using the injection molding system 100 according to embodiments. Examples of chalcogenide glass compositions that can be injection molded using the injection molding system 100 are disclosed in U.S. Patent No. 7,116,888 Bl, issued on October 3, 2006, and U.S. Patent No. 10,519,061 B2, issued on December 31, 2019, the contents of each of which are incorporated herein by reference in their entireties.

[0054] The mold 300 and the clamping system 400 are now described with reference to FIGS. 1, 2, 3 A, and 3B. In embodiments, the mold 300 comprises a first mold half 304 that is fixed or stationary relative to the injection unit 200 and a second mold half 308 configured totranslate relative to the first mold half 304. The first mold half 304 may be interchangeably referred to as the A-half or the A-side, and the second mold half 308 may be interchangeably referred to as the B-half or B-side. The clamping system 400 comprises a first platen 404 that is fixed or stationary relative to the injection unit 200 and a second platen 408 configured to translate relative to the first platen 404. The first (stationary) mold half 304 is secured to the first (stationary) platen 404, and the second (movable) mold half 308 is secured to the second (movable) platen 408.

[0055] The clamping system 400 further comprises a drive system 412 configured to move the second platen 408, which in turn moves the second mold half 308, between a clamped position in which the second mold half 308 contacts the first mold half 304, as shown in FIG. 1, and an open position in which the second mold half 308 is spaced from the first mold half 304. When the second mold half 308 is in the clamped position, the clamping system 400 is further configured to press the second mold half 308 against the first mold half 304 with sufficient force to generate the high pressure therebetween needed to inject molten material into the mold 300 during an injection molding cycle, as described later in this disclosure. In an exemplary embodiment, the drive system is a hydraulic cylinder, such as shown in FIG. 1, configured to generate the high pressure between the first mold half 304 and the second mold half 308 during an injection molding cycle. Other drive systems can be used in other embodiments.

[0056] Referring now to FIGS. 2, 3 A, and 3B, each of the first mold half 304 and the second mold half 308 has a mold exterior 312 and a mold interior 316 that is separated from the mold exterior 312. The mold interior 316 includes the surfaces of the mold 300 that are open to or otherwise intersect a parting line or plane 320 (FIG. 1) that is formed when the second mold half 308 contacts / presses against the first mold half 304 in the clamped position. In the embodiment shown, the mold interior 316 of the first mold half 304 is configured to define a mold cavity 324 and a runner passage 328 through which the glass melt is configured to be directed into the mold cavity 324 during an injection molding cycle. The mold cavity 324 is configured to negatively define the precision optical element once the glass melt solidifies therein.

[0057] In embodiments, the precision optical element includes a glass body that is molded from the chalcogenide glass added to the injection molding system 100. The glass body is configured to define the structure of the precision optical element. In embodiments, the glass body (as molded) has one or more surfaces that are smooth (e.g., surface roughness < 10 nmRa), have simple or complex profiles (e.g., concave, convex, and / or true prismatic profiles), and / or have exacting surface features in the micron (e.g., < 500 pm) to sub-micron dimensional range, as needed for image forming or transmission applications. In embodiments, the precision optical element can be a lens, a microlens, an array of microlenses, a prism, a coupler, a sensor, a diffraction grating, a surface relief diffuser, a Fresnel lens, an optical fiber, or a precision optical device that incorporates multiple optical elements. In an exemplary embodiment, the precision optical element is a lens.

[0058] Although only one mold cavity 324 and one runner passage 328 are depicted in the figures, it should be appreciated that other embodiments can have any number and configuration of mold cavities and runners. Similarly, it should be appreciated that the first mold half 304 and / or the second mold half 308 can include additional features used to facilitate injection molding of the precision optical element, such as runners, gates, ejector pins, vents, removable or fixed inserts, and the like.

[0059] Referring again FIGS. 1, 2, 3 A, and 3B, the injection molding system 100 further comprises a heated sprue bushing 110 disposed in the first mold half 304. The heated sprue bushing 110 has a body 114 that comprises a head portion 118 and an elongated portion 122 that extends from the head portion 118. In embodiments, the head portion 118 and the elongated portion 122 have cylindrical outer peripheries that are arranged substantially concentric with one another. In such embodiments, the head portion 118 can have a diameter that is larger than a diameter of the elongated portion 122 so that the head portion 118 defines a flange 122. The first mold half 304 can have a through hole that extends between the mold exterior 312 and the mold interior 316 with a counterbore that opens to the mold exterior 312. The flange 126 is configured to abut a bottom of the counterbore 130 to position the heated sprue bushing 110 against the first mold half 304. The head portion 118 can have a contact surface 132 configured to abut the nozzle 232 of the injection device 204. In embodiments, such as shown in FIG. 3 A, the contact surface defines a concave, spherical depression that is configured to self-align the nozzle 232 with the heated sprue bushing 110.

[0060] As best shown in FIG. 3 A, the heated sprue bushing 110 extends through the mold 300 (e.g., the first mold half 304) from the mold exterior 312 to the mold interior 316. The body 114 of the heated sprue bushing 110 is configured to define a sprue passage 134 through which the glass melt is configured to be directed from the nozzle passage 236 to the runner passage 328. The heated sprue bushing 110 has a first sprue bushing portion 138 that defines a first sprue passage portion 140 of the sprue passage 134. The first sprue passage portion 140 isproximate (e.g., fluidically connected to) the runner passage 328. The heated sprue bushing 110 also has a second sprue bushing portion 142 that defines a second sprue passage portion 144 of the sprue passage 134. The second sprue passage portion 144 is proximate (e.g., fluidically connected to) the nozzle passage 236.

[0061] The sprue passage 134 comprises a narrowing transition 148 that separates the first sprue passage portion 140 from the second sprue passage portion 144. Since the first sprue bushing portion 138 and the second sprue bushing portion 142 define the first sprue passage portion 140 and the second sprue passage portion 144, respectively, the narrowing transition 148 correspondingly separates the first sprue bushing portion 138 from the second sprue bushing portion 142. In FIG. 3A, a dotted line positioned at the narrowing transition 148 and oriented substantially normal to a central axis of the sprue passage 134 is used to illustrate the separation between the first sprue bushing portion 138 (e.g., defining the first sprue passage portion 140) and the second sprue bushing portion 142 (e.g., defining the second sprue passage portion 144). In embodiments, the narrowing transition 148 comprises a reduced-diameter region of the sprue passage 134. The narrowing transition 148 can be located at any position along the sprue passage 134 though it is preferably located at a midpoint along the sprue passage or closer to the runner passage 328 than the midpoint. In an exemplary embodiments, the narrowing transition 148 is proximate the runner passage 328 by about 20%, 15%, 10%, 5%, or less of a total length of the sprue passage 134.

[0062] In embodiments, the sprue passage 134 is configured to be continuous along an entire length thereof between the mold exterior 312 and the mold interior 316. As used herein, the “continuous” means the surfaces that define the sprue passage 134 are smooth and without discontinuities that can induce turbulence as the glass melt flows through the sprue passage 134. For example, the sprue passage 134 is continuous when the sprue passage 134 is defined entirely by a monolithic region of the heated sprue bushing 110 (e.g., no threaded tips). The continuity and smoothness of the sprue passage 134 may influence the quantity of bubbles incorporated in an injection molded part formed from chalcogenide glass. More specifically, discontinuous and / or rough surfaces within the sprue passage 134 may increase the quantity of bubbles in the injected molded part, which may reduce infrared transmission through the injection molded part.

[0063] Referring now to FIGS. 2 and 3 A, the injection molding system 100 further comprises a first heater 150 configured to heat the first sprue passage portion 140 of the sprue passage 134 proximate the runner passage 328. In embodiments, the first heater 150 isconfigured to heat the first sprue passage portion 140 such that when a runner element is ejected from the mold 300, as described later in this disclosure, solidified glass within the first sprue passage portion 140 is configured to release completely therefrom and eject with the runner element.

[0064] The first heater 150 can be positioned to contact a periphery of the elongated portion 122 of the heated sprue bushing 110 such that it (completely) surrounds the first sprue bushing portion 138 and (completely) surrounds a corresponding portion of the second sprue bushing portion 142 associated with the elongated portion 122. The first heater 150 can heat the first sprue bushing portion 138, which in turn heats the corresponding first sprue passage portion 140 defined by the first sprue bushing portion 138. The first heater 150 can also heat the corresponding portion of the second sprue bushing portion 142 associated with the elongated portion 122, which in turn heats the corresponding second sprue passage portion 144 defined by the corresponding portion of second sprue bushing portion 142.

[0065] Referring still to FIGS. 2 and 3 A, the injection molding system 100 can further comprise a second heater 154 configured to heat the second sprue passage portion 144 of the sprue passage 134 proximate the nozzle passage 236. In embodiments, the second heater 154 is configured to heat the second sprue passage portion 144 such that the glass melt in the second sprue passage portion 144 remains in liquid form, for example, during an entirety of the injection molding cycle. In embodiments, the first heater 150 and the second heater 154 cooperate to heat the second sprue passage portion 144 such that the glass melt in the second sprue passage portion 144 remains in liquid form, for example, during an entirety of the injection molding cycle.

[0066] The second heater 154 can be positioned to contact a periphery of the head portion 118 of the heated sprue bushing 110 such that it (completely) surrounds a corresponding portion of the second sprue bushing portion 142 associated with the head portion 118. The second heater 154 can heat the corresponding portion of the second sprue bushing portion 142 associated with the head portion 118, which in turn heats the corresponding second sprue passage portion 144 defined by the corresponding portion of the second sprue bushing portion 142. In embodiments, the first heater 150 and the second heater 154 can be controlled independently from one another, as described later in this disclosure. In such embodiments, the heated sprue bushing 110 has two zones of temperature control.

[0067] FIG. 4 is an enlarged schematic cross-sectional view of the first (fixed) mold half 304 that shows the heated sprue bushing 110 with a different configuration of the heaters. For example, the first heater 150a can be positioned to contact a periphery of a portion of the elongated portion 122 of the heated sprue bushing 110 such that it (completely) surrounds only the first sprue bushing portion 138. The second heater 154a can be positioned to contact a periphery of a different portion of the elongated portion 122 of the heated sprue bushing 110 such that it (completely) surrounds only the corresponding portion of second sprue bushing portion 142 associated with the elongated portion 122. The second heater 154a can also be positioned to contact a periphery of the head portion 118 of the heated sprue bushing 110 such that it (completely) surrounds the corresponding portion of the second sprue bushing portion 142 associated with the head portion 118.

[0068] In the configuration shown in FIG. 4, the first heater 150a is configured to exclusively heat the first sprue bushing portion 138, which in turn heats the corresponding first sprue passage portion 140 defined by the first sprue bushing portion 138. The second heater 154a is configured to exclusively heat the second sprue bushing portion 142 (e.g., the corresponding portions of the second sprue bushing 142 associated with the head portion 118 and the elongated portion 122), which in turn heats the corresponding second sprue passage portion 144 defined by the second sprue bushing portion 142. In embodiments, the first heater 150a and the second heater 154a of FIG. 4 can be controlled independently from one another similar to the first heater 150 and the second heater 154 of FIGS. 2 and 3 A. In such embodiments, the heated sprue bushing 110 has two zones of temperature control.

[0069] In another configuration of the heaters described with reference to FIG. 4, the second heater 154a, which is positioned to contact a periphery of the head portion 118 of the heated sprue bushing 110, is further configured as a third heater 158 that can be controlled independently from the first heater 150a and the second heater 154a. In such a configuration, the heated sprue bushing 110 has three zones of temperature control. The configurations shown and described with reference to FIG. 4 can enable high-resolution temperature control of the first sprue passage portion 140 of the sprue passage 134, which can further facilitate release of solidified glass in the first sprue passage portion 140 during an injection cycle.

[0070] FIG. 5 is an enlarged schematic cross-sectional view of the first (fixed) mold half 304 that shows the heated sprue bushing 110 with one or more thermal isolation members 170, 174. In the embodiment shown, the thermal isolation members comprise a first thermal isolation member 170 disposed between the counterbore 130 of the first mold half 304 and abottom of the head portion 118 of the heated sprue bushing 110 along the flange 126. In this position, the first thermal isolation member 170 is configured to thermally isolate the heated sprue bushing 110 from the first mold half 304. The thermal isolation members can also include a second thermal isolation member 174 disposed at a top of the head portion 118 of the heated sprue bushing 110. In this position, the second thermal isolation member 174 is configured to thermally isolate the heated sprue bushing 110 from the nozzle 232 (FIG. 2) that abuts the heated sprue bushing 110 during an injection cycle.

[0071] In embodiments, the one or more thermal isolation members 170, 174 are configured in the shape of relatively thin washers with inside diameters and outside diameters sized to provide sufficient surface area contact for their thermal isolation function. In embodiments, the thermal isolation members 170, 174 are formed from a material configured to have sufficient compressive strength when positioned about the heat sprue bushing 110 as described herein. The material of the thermal isolation members 170, 174 is further configured to withstand degradation at temperatures up to about 500 °C (or more), which may correspond to the typical operating temperatures of the injection molding system disclosed herein. An example material that can be used for the thermal isolation member 170, 174 is Mica M / Cogetherm M / Pamitherm® M provided by Red Seal Electric Company. It should be appreciated that other materials can also be used for the thermal isolation members 170, 174 in other embodiments.

[0072] Referring again to FIG. 3 A, the injection molding system 100 further comprises one or more temperatures sensors 162(a), 162(b) configured to perform temperature measurements on one or more portions of the heated sprue bushing 110. The sensors can include a first sensor 162(a) configured to measure a first temperature of a portion of the heated sprue bushing 110. The sensors can further include a second sensor 162(b) configured to measure a second temperature of a portion of the heated sprue bushing 110. The sensors can include additional temperature sensors configured to measure multiple temperatures along corresponding multiple portions of either or both of the first sprue bushing portion 138 and the second sprue bushing portion 142. In the embodiment shown, the first sensor 162(a) and the second sensor 162(b) are positioned along different portions of the second sprue bushing portion 142. In an exemplary embodiment (not shown), the first sensor 162(a) is positioned along a portion of the first sprue bushing portion 138 to measure a first temperature thereof.

[0073] In embodiments, some of the methods, processes, actions, and / or steps described herein can be performed by a controller 500. The controller 500 can include operativeconnections to the various systems, devices, sensors, etc. associated with the injection molding system 100. For example, the one or more sensors 162(a), 162(b) can send the temperatures measured by the sensors to the controller 500 using a signal (e.g., an electrical signal, fiber optic signal, and / or wireless signal). The controller 500 can perform a determination such as a calculation using the signal data from the one or more sensors 162(a), 162(b), as described later in this disclosure. The controller 500 can then generate one or more commands based on the determination / calculation and transmit those one or more commands to start, adjust, and / or stop actions associated with the injection molding system 100. For example, one or more of the first heater 150, 150a and the second heater 154, 154a can be configured to receive one or more commands from the controller 500 in order to start, adjust, and / or stop heating parameters, such as turning the heater ON or OFF and / or adjusting a heating rate of the heater.

[0074] The controller 500 is configured to operate the injection molding system 100 to perform an injection molding cycle. In embodiments, the controller 500 is configured to operate the injection molding system 100 to direct the glass melt along a (continuous) passage (e.g., comprising the nozzle passage 236, the sprue passage 134, and the runner passage 328) from the injection device 204 into the mold cavity 324. For example, with reference to FIG. 2, once a shot volume of the glass melt is built within the cylinder 216, the controller can operate the plunger 220 to extend and discharge the shot volume of the glass melt towards the nozzle passage 236. The glass melt is continuously directed through the passage until the plunger 220 is fully extended within the cylinder 216 or the controller 500 halts extension of the plunger 220 prior to full extension.

[0075] In embodiments, after the glass melt is directed along the passage and fills the mold cavity 234, the controller 500 is configured to operate the injection molding system 100 to solidify the glass melt within the mold interior 316 of the mold 300 to form (i) the precision optical element from the solidified glass in the mold cavity 234 and (ii) a runner element from the solidified glass in the runner passage 328. In embodiments, solidifying the glass melt may comprise maintaining the mold 300 in the closed / clamped position for a solidifying dwell time. During the solidifying dwell time, the plunger 220 may still be operated to apply a packing pressure to the glass melt within the mold 300.

[0076] In embodiments, after the glass melt within the mold 300 is sufficiently solidified (i.e., the solidifying dwell time has been met), the controller 500 is configured to operate the injection molding system 100 to eject the precision optical element and the runner element from the mold 300. For example, the clamping system 400 can be actuated to move the secondmold half 308 into the open position, and one or more ejector pins in one or more of the first mold half 304 and the second mold half 308 can be actuated to eject the precision optical element and the runner element from the mold 300.

[0077] In embodiments, during any one or more of the heating (e.g., heating the particles of chalcogenide glass to form the glass melt), the directing (e.g., directing the glass melt along the passage), and the solidifying (e.g., solidifying the glass melt within the mold interior), the controller 500 is configured to operate the first heater 150, 150a to heat the first sprue passage portion 140 of the sprue passage 134 proximate the runner passage 328 such that when the runner element is ejected from the mold 300, the solidified glass within the first sprue passage portion 140 is configured to release completely therefrom and eject with the runner element. As used herein, the phrase “release completely” means that the solidified glass within the first sprue passage portion 140 (i) does not break or fracture when pulled from the first sprue passage portion 140 by the runner element and (ii) does not leave any residue (glass or otherwise) within the first sprue passage portion 140 when pulled from the first sprue passage portion 140 by the runner element.

[0078] In embodiments, heating the first sprue passage portion 140 further comprises varying a heating rate of the first heater 150 so that the first sprue bushing portion 138 has a first setpoint temperature concurrently with the ejecting of the precision optical element and the runner element. As used herein, the phrase “concurrently with the ejecting” means the first sprue bushing portion 138 has the first setpoint temperature at the earliest moment the precision optical element is ready to be ejected from the mold, such as at the moment the solidifying dwell time has been met after injecting the glass melt into the mold 300. In other words, the ejecting of the precision optical element is not to be delayed, allowing additional time for the first sprue bushing portion 138 to achieve the first setpoint temperature. Instead, the output of the first heater 150 is adjusted (i.e., by increasing / decreasing or otherwise varying the heating rate thereof) to ensure and the first sprue bushing portion 138 has the first setpoint temperature concurrently with the ejecting.

[0079] In embodiments, during any one or more of the heating (e.g., heating the particles of chalcogenide glass to form the glass melt), the directing (e.g., directing the glass melt along the passage), and the solidifying (e.g., solidifying the glass melt within the mold interior), the controller 500 is configured to operate the second heater 154, 154a to heat the second sprue passage portion 144 of the sprue passage 134 proximate the nozzle passage 236 such that the glass melt in the second sprue passage portion 144 remains in liquid form. In embodiments,heating the second sprue passage portion 144 comprises maintaining the second sprue bushing portion 142 at a second setpoint temperature. In embodiments, maintaining the second sprue bushing portion 142 at the second setpoint temperature can be achieved by using a constant heating rate for the second heater 154, 154a and / or cycling the second heater between an ON state and an OFF state, if needed.

[0080] In embodiments, the controller 500 is configured to implement a first routine to operate the first heater 150, 150a. For example, the controller can be configured to (i) receive the (measured) first temperature from the first sensor 162(a), (ii) compare the first temperature to a (predetermined) first setpoint temperature, and (iii) generate a first command based on the comparison. Thereafter, the first heater 150, 150a is configured to receive the first command and vary a heating rate thereof so that the first sprue bushing portion 138 has the first setpoint temperature concurrently with the ejecting. As an example of the first routine, consider the following two scenarios.

[0081] In both scenarios, the mold 300 has just been filled with the glass melt and the solidifying dwell time is approximately 10 seconds (e.g., the mold will be held in the clamped position for approximately 10 seconds to allow the glass melt therein to sufficiently solidify before ejecting the molded parts therefrom). In both scenarios, the (predetermined) first setpoint temperature for the first sprue bushing portion 138 of the sprue bushing 110 is approximately 290 °C. In a first scenario, the first sensor 162(a) measures a first temperature of approximately 288 °C at the first sprue bushing portion 138. In a second scenario, the first sensor 162(a) measures a first temperature of approximately 286 °C at the first sprue bushing portion 138. Thus, the first temperature of the second scenario has deviated further from the first setpoint temperature than the first temperature of the first scenario. Since both scenarios have the same amount of time (e.g., 10 seconds) to increase the measured first temperature of the first sprue bushing portion 138 to the first setpoint temperature, the controller 500 needs to implement a higher heating rate for the first heater in the second scenario than needed for the first heater in the first scenario in order to achieve the first setpoint temperature in time for the ejecting.

[0082] In embodiments, the controller 500 is configured to implement a second routine to operate the second heater 154, 154a. For example, the controller can be configured to (i) receive the (measured) second temperature from the second sensor 162(b), (ii) compare the second temperature to a (predetermined) second setpoint temperature, and (iii) generate a second command based on the comparison. Thereafter, the second heater 154, 154a is configured toreceive the second command and maintain the second sprue bushing portion 142 at the second setpoint temperature, for example, by using a constant heating rate for the second heater 154, 154a and / or cycling the second heater between an ON state and an OFF state.

[0083] In embodiments, the first setpoint temperature is configured to be greater than or equal to the second setpoint temperature. In embodiments, the first setpoint temperature is at least 10 °C greater than the second setpoint temperature, such as 11 °C, 12 °C, 13 °C, 14°C, 15 °C, 16 °C, 17 °C, 18 °C, 19 °C, 20 °C, or more greater than the second setpoint temperature.

[0084] Chalcogenide glasses have steep viscosity curves such that even exceedingly small variations in temperature can have drastic effects on the flow of the glass. In particular, during the step of solidifying the glass melt after the mold cavity 324 is filled until just before the step of opening the mold 300 to eject the molded part (e.g., the precision optical element), the temperature of the solidifying / solidified glass in the first sprue bushing portion 138 should be accurately controlled to ensure such solidified glass releases completely from the mold 300 during the ejecting of the precision optical element and the runner element. Existing heated sprue bushings may not provide sufficient resolution of temperature control due to the steep viscosity curves of chalcogenide glass. The heated sprue bushing disclosed herein along with the injection molding system 100 and operating methods disclosed herein enable injection molding of precision optical elements from chalcogenide glass that otherwise would not be possible.

[0085] The term “controller" should not be construed to limit the embodiments disclosed herein to any particular device type or system. In embodiments, the controller includes a computer system. The computer system may be a laptop computer, a desktop computer, or a mainframe computer. The computer system may include a graphical user interface (GUI) so that a user can interact with the computer system. The computer system may also include a computer processor (e.g., a microprocessor, microcontroller, digital signal processor, or general-purpose computer) for executing any of the methods and processes described above.

[0086] The computer system may further include a memory such as a semiconductor memory device (e g., a RAM, ROM, PROM, EEPROM, or Flash-Programmable RAM), a magnetic memory device (e.g., a diskette or fixed disk), an optical memory device (e.g., a CD- ROM), a PC card (e.g., PCMCIA card), or other memory device. This memory may be used to store, for example, the measured temperatures of the different portions of the heated sprue bushing 110 and the predetermined setpoint temperatures for these different portions.

[0087] Some of the methods and processes described above can be implemented as computer program logic for use with the computer processor. The computer program logic may be embodied in various forms, including a source code form or a computer executable form. Source code may include a series of computer program instructions in a variety of programming languages (e.g., an object code, an assembly language, or a high-level language such as C, C++, or JAVA). Such computer instructions can be stored in a non-transitory computer readable medium (e.g., memory) and executed by the computer processor. The computer instructions may be distributed in any form as a removable storage medium with accompanying printed or electronic documentation (e.g., shrink wrapped software), preloaded with a computer system (e.g., on system ROM or fixed disk), or distributed from a server or electronic bulletin board over a communication system (e.g., the Internet or World Wide Web).

[0088] Additionally, or alternatively, the controller may include discrete electronic components coupled to a printed circuit board, integrated circuitry (e.g., Application Specific Integrated Circuits (ASIC)), and / or programmable logic devices (e.g., a Field Programmable Gate Arrays (FPGA)). Any of the methods and processes described above can be implemented using such logic devices.

[0089] While the disclosure has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications, and further applications that come within the spirit of the disclosure are desired to be protected.

Claims

CLAIMSWhat is claimed is:

1. A method for forming a precision optical element via injection molding, comprising: heating, in an injection device, particles of chalcogenide glass to form a glass melt, the chalcogenide glass having a IO4 0P temperature of 500 °C or less and being resistant to crystallization at a shear rate in the range of 1,000 sec'1to 10,000 sec'1; directing the glass melt along a passage from the injection device into a mold cavity of a mold that negatively defines the precision optical element, the passage comprising: a nozzle passage through which the glass melt is configured to be directed from the injection device, the nozzle passage defined by the injection device, a runner passage through which the glass melt is configured to be directed into the mold cavity, the runner passage defined by a mold interior of the mold, and a sprue passage through which the glass melt is configured to be directed from the nozzle passage to the runner passage, the sprue passage defined by a heated sprue bushing that extends through the mold from the mold interior to a mold exterior that is separated from the mold interior; solidifying the glass melt within the mold interior to form (i) the precision optical element from the solidified glass in the mold cavity and (ii) a runner element from the solidified glass in the runner passage; ejecting the precision optical element and the runner element from the mold; and heating, with a first heater, a first sprue passage portion of the sprue passage proximate the runner passage such that when the runner element is ejected from the mold, the solidified glass within the first sprue passage portion is configured to release completely therefrom and eject with the runner element.

2. The method of claim 1, wherein the heated sprue bushing has a first sprue bushing portion that defines the first sprue passage portion, and wherein heating the first sprue passage portion comprises varying a heating rate of the first heater so that the first sprue bushing portion has a first setpoint temperature concurrently with the ejecting.

3. The method of claim 2, further comprising heating, with a second heater, a second sprue passage portion of the sprue passage proximate the nozzle passage such that the glass melt in the second sprue passage portion remains in liquid form.

4. The method of claim 3, wherein the sprue passage comprises a narrowing transition that separates the first sprue passage portion from the second sprue passage portion.

5. The method of claim 4, wherein the heated sprue bushing has a second sprue bushing portion that defines the second sprue passage portion, and wherein heating the second sprue passage portion comprises maintaining the second sprue bushing portion at a second setpoint temperature.

6. The method of claim 5, wherein the first setpoint temperature is greater than or equal to the second setpoint temperature.

7. The method of claim 5, wherein the first setpoint temperature is at least 10 °C greater than the second setpoint temperature.

8. The method of any one of claims 1-7, wherein the mold comprises (i) a first mold half that is fixed in position relative to the injection device and (ii) a second mold half configured to translate relative to the first mold half, the heated sprue bushing disposed in the first mold half.

9. The method of claim 8, wherein the second mold half is configured to translate between (i) a clamped position, during the directing and the solidifying, in which the second mold half is pressed against the first mold half and (ii) an open position, during the ejecting, in which the second mold half is spaced from the first mold half.

10. The method of any one of claims 1-9, wherein the sprue passage is configured to be continuous along an entire length thereof between the mold exterior and the mold interior.

11. The method of any one of claim 1-10, further comprising: prior to the directing, building a shot volume of the glass melt under a first pressure in the injection device; and after the shot volume is built, applying a second pressure that is greater than the first pressure to the shot volume for a first duration in the injection device to degas the glass melt.

12. An injection molding system, comprising: an injection device configured heat particles of chalcogenide glass to form a glass melt, the chalcogenide glass having a IO40P temperature of 500 °C or less and being resistant to crystallization at a shear rate in the range of 1,000 sec'1to 10,000 sec'1, the injection device comprising a nozzle that defines a nozzle passage through which the glass melt is configured to be directed from the injection device; a mold having a mold exterior and a mold interior separated from the mold exterior, the mold interior defining a mold cavity and a runner passage through which the glass melt is configured to be directed into the mold cavity, the mold cavity configured to negatively define a precision optical element; a heated sprue bushing extending through the mold from the mold exterior to the mold interior, the heated sprue bushing defining a sprue passage through which the glass melt is configured to be directed from the nozzle passage to the runner passage; a controller configured to operate the injection molding system to: direct the glass melt from the injection device along the nozzle passage, the sprue passage, and the runner passage and into the mold cavity, solidify the glass melt within the mold interior to form (i) the precision optical element from the solidified glass in the mold cavity and (ii) a runner element from the solidified glass in the runner passage, and eject the precision optical element and the runner element from the mold; and a first heater configured to heat a first sprue passage portion of the sprue passage proximate the runner passage such that when the runner element is ejected from the mold, the solidified glass within the first sprue passage portion is configured to release completely therefrom and eject with the runner element.

13. The injection molding system of claim 12, wherein: the heated sprue bushing has a first sprue bushing portion that defines the first sprue passage portion, the injection system further comprises a first sensor configured to detect a first temperature of the first sprue bushing portion, the controller is configured to (i) receive the first temperature from the first sensor, (ii) compare the first temperature to a first setpoint temperature, and (iii) generate a first command based on the comparison, andthe first heater is configured to receive the first command and vary a heating rate of the first heater so that the first sprue bushing portion has the first setpoint temperature concurrently with the ejecting.

14. The injection molding system of claim 13, further comprising a second heater configured to heat a second sprue passage portion of the sprue passage proximate the nozzle passage such that the glass melt in the second sprue passage portion remains in liquid form.

15. The injection molding system of claim 14, wherein the sprue passage comprises a narrowing transition that separates the first sprue passage portion from the second sprue passage portion.

16. The injection molding system of claim 15, wherein: the heated sprue bushing has a second sprue bushing portion that defines the second sprue passage portion, the injection system further comprises a second sensor configured to detect a second temperature of the second sprue bushing portion, the controller is configured to (i) receive the second temperature from the second sensor, (ii) compare the second temperature to a second setpoint temperature, and (iii) generate a second command based on the comparison, and the second heater is configured to receive the second command and maintain the second sprue bushing portion at the second setpoint temperature.

17. The injection molding system of claim 16, wherein the first setpoint temperature is greater than or equal to the second setpoint temperature.

18. The injection molding system of claim 16, wherein the first setpoint temperature is at least 10 °C greater than the second setpoint temperature.

19. The injection molding system of any one of claims 12-18, wherein the mold comprises (i) a first mold half that is fixed in position relative to the injection device and (ii) a second mold half configured to translate relative to the first mold half, the heated sprue bushing disposed in the first mold half.

20. The injection molding system of claim 19, wherein the second mold half is configured to translate between (i) a clamped position, when the glass melt is directed from the injection device and solidified within the mold interior, in which the second mold half is pressed against the first mold half and (ii) an open position, when the precision optical element and the runner element are ejected from the mold, in which the second mold half is spaced from the first mold half.

21. The injection molding system of any one of claims 12-20, wherein the sprue passage is configured to be continuous along an entire length thereof between the mold exterior and the mold interior.

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