SYSTEM FOR INSULATING AN INDUCTION VACUUM FURNACE AND METHOD OF MAKING SAME

Abstract

A system and method for insulating an induction vacuum furnace is disclosed. An induction furnace for heating a workpiece includes a chamber, an insulation cylinder positioned within the chamber, and an induction coil positioned to surround at least a portion of the insulation cylinder. A susceptor is positioned within the insulation cylinder and inductively heated by the induction coil when a current is provided to the induction coil. An insulating jacket assembly including one of a carbide material and a refractory metal is positioned in a space between the insulating cylinder and the susceptor.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This is a national stage application under 35 U.S.C. §371(c) of prior-filed, co-pending, PCT application serial number PCT/US2013/038796, filed on Apr. 30, 2013, which claims priority to U.S. Provisional Application No. 61/694,869, filed Aug. 30, 2012, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Embodiments of the invention relate generally to induction furnaces for heating a workpiece in an inert atmosphere or vacuum and, more particularly, to a system for providing an insulation package for an induction furnace having improved insulation properties at temperatures above 1200 degrees Celsius.

Conventional induction furnaces include an induction heating system and a chamber that contains a susceptor that is susceptible to induction heating, with the chamber enclosing an inert atmosphere or vacuum therein. An electromagnetic coil sits outside the susceptor and receives high frequency alternating current from a power supply. The resulting alternating electromagnetic field heats the susceptor rapidly. The workpiece to be heated is placed in proximity to and generally within the susceptor so that when the susceptor is inductively heated by the induction heating system, the heat is transferred to the workpiece through radiation and/or conduction and convection. After a desired heating and processing of the workpiece is completed, the workpiece is then subsequently cooled in order to complete the heating/cooling cycle.

Induction heating can be used to bond, harden or soften metals or other conductive materials in a wide variety of manufacturing processes. The intended outcome of the induction heating process (e.g., bonding or hardening), the furnace efficiency and cycle time, as well as the size, geometry, and material properties of the workpiece are all factors that may be taken into account in a design of an induction furnace.

Prior art induction furnaces typically operate at temperatures at or below 1200 degrees Celsius. For certain manufacturing processes and workpiece materials, however, it would be desirable to operate the induction furnace at temperatures above 1200 degrees Celsius. Prior art induction furnaces experience a number of negative effects when operating at temperatures above 1200 degrees Celsius. For example, the operating efficiency of the furnace and the temperature uniformity within the furnace is negatively affected. Further, dielectric breakdown tends to occur around the induction coils of the furnace at furnace operating temperatures above 1200 degrees Celsius.

It would therefore be desirable to design an induction furnace capable of operating at temperatures above 1200 degrees Celsius, while maintaining efficient and uniform heating and preventing dielectric breakdown around the induction coils.

BRIEF DESCRIPTION OF THE INVENTION

Embodiments of the invention overcome the aforementioned drawbacks by providing a system and method for insulating an induction vacuum furnace.

In accordance with one aspect of the invention, an induction furnace for heating a workpiece includes a chamber, an insulation cylinder positioned within the chamber, and an induction coil positioned to surround at least a portion of the insulation cylinder. A susceptor is positioned within the insulation cylinder and inductively heated by the induction coil when a current is provided to the induction coil. An insulating jacket assembly including one of a carbide material and a refractory metal is positioned in a space between the insulating cylinder and the susceptor.

In accordance with another aspect of the invention, an induction furnace includes a chamber having a susceptor positioned therein. An interior volume of the susceptor defines a zone within the chamber for heating a workpiece. The induction furnace also includes an insulation package having a fused quartz cylinder positioned around the susceptor and a graphite jacket positioned between the fused quartz cylinder and the susceptor. A coil surrounds the insulation package and is configured to inductively heat the interior volume of the susceptor when a current is provided to the induction coil.

In accordance with yet another aspect of the invention, a method of making an induction furnace includes providing a vacuum chamber, coupling an insulation cylinder within the vacuum chamber, and coupling an induction coil to surround at least a portion of the insulation cylinder. The method also includes coupling a susceptor within the insulation cylinder and encapsulating the susceptor with an insulating jacket, wherein the insulating jacket comprises one of a carbide material and a refractory metal.

These and other advantages and features will be more readily understood from the following detailed description of embodiments of the invention that is provided in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate embodiments presently contemplated for carrying out the invention.

In the drawings:

FIG. 1 is a block schematic diagram of an induction furnace according to an embodiment of the invention.

FIG. 2 is an additional diagram of the induction furnace of FIG. 1 where a workpiece is in a lowered position.

FIG. 3 is a block schematic diagram of an induction furnace according to another embodiment of the invention.

FIG. 4 is an additional diagram of the induction furnace of FIG. 3 where a workpiece is in a lowered position.

FIG. 5 is a flowchart illustrating a technique for heating and cooling a workpiece using an induction furnace according to an embodiment of the invention.

FIG. 6 is a block schematic diagram of an induction furnace according to an alternative embodiment of the invention.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, the major components of an induction furnace 100 are shown. Induction furnace 100 includes an induction heating system 102 inside a chamber 104. Induction heating system 102 includes an insulation package 106 comprising an insulation cylinder 108 and an insulating jacket assembly 110. Insulation cylinder 108 includes a side wall 112, a first cover 114 for sealing one end of cylinder 108, and a second cover 116 for sealing the second end of cylinder 108. Induction heating system 102 includes a coil 118 and a power supply (not shown) that provides an alternating current that flows through coil 118 during a heating cycle. Coil 118 is wound to form a helical shape within chamber 104 about insulation cylinder 108 as shown in FIG. 1.

Contained within insulation cylinder 108 is a susceptor 120 that is susceptible to induction heating. That is, when an alternating current flows through coil 118, an alternating magnetic field is generated that induces eddy currents and other effects in susceptor 120 that cause the susceptor 120 to heat. The thermal energy that radiates from susceptor 120 is used to heat a workpiece 122. Susceptor 120 is shown as being cylindrical, but other shapes can be used. Susceptor 120 is made of any material susceptible to induction heating, such as, for example, graphite, molybdenum, steel, and tungsten. Susceptor 120 is arranged within insulation cylinder 108 in chamber 104. Insulation cylinder 108 is made from an insulative material that is not susceptible to induction heating such as, for example, fused quartz.

Susceptor 120 includes a side wall 124, a first cover 126 for sealing one end, and a second cover 128 for sealing the other end. A tray 130 for supporting workpiece 122 to be heated is connected to second cover 128 of susceptor 120. Although susceptor 120 is shown as having closed ends, this need not be the case. For example, the susceptor 120 can be in the form of a tube that is open at both ends or, for example, it can comprise one or more susceptor sheets. First cover 114 of cylinder 108 is coupled to chamber 104 via one or more posts 132, which in an embodiment, is constructed of a ceramic material. First cover 126 of susceptor 120 is coupled to first cover 114 via one or more additional posts 134.

Insulating jacket assembly 110 includes a plurality of insulating sheets 136 arranged in layers to cover the exterior surfaces of susceptor 120. As shown in FIG. 1, insulating sheets 136 are contained in the space between insulation cylinder 108 and susceptor 120 to prevent any loose material of insulating sheets 136 from contaminating the rest of the vacuum chamber or in the components being processed in induction furnace 100. In particular, a first portion 138 of insulating sheets 136 is positioned between outer surface 140 of side wall 124 of susceptor 120 and an inner surface 142 of side wall 112 of insulation cylinder 108. A second portion 144 of insulating sheets 136 are positioned between a top surface 146 of first cover 126 of susceptor 120 and an upper, inside surface 148 of insulation cylinder 108. A third portion 150 of insulating sheets 136 is positioned between a bottom surface 152 of second cover 128 and a lower, inside surface 154 of insulation cylinder 108.

Each layer of the insulating sheets 136 may be, for example, approximately ⅛ inch thick, and is woven at a frequency such that the material is transparent to induction. In one exemplary embodiment, the first portion 138 of insulating sheets 136 includes three (3) individual layers wrapped around susceptor 120, the second portion 144 of insulating sheets 136 includes four (4) individual layers sized to approximately match the geometry of the first cover 126 of susceptor 120, and third portion 150 of insulating sheets 136 includes ten (10) individual layers sized to approximately match the geometry of the second cover 128 of susceptor 120. However, one skilled in the art will recognize that the number of layers of insulating sheets 136 as well as the geometry and thickness of each layer may be varied based on desired insulating characteristics.

In one embodiment, insulation package 106 further includes an upper insulating plate 156 positioned atop the second portion 144 of insulating sheets 136 and a lower insulating plate 158 positioned below the third portion 150 of insulating sheets 136 to further contain second and third portions 144, 150 of insulating sheets 136. Upper and lower insulating plates 156, 158 retain insulating sheets 136 against susceptor 120 and provide additional insulation for susceptor 120. In an exemplary embodiment, upper insulating plate 156 and lower insulating plate 158 are constructed of graphite.

Insulating sheets 136, which comprise carbides or refractory metals, insulate the outside of susceptor 120 and mitigate radiative heat loss. In an exemplary embodiment, insulating sheets 136 are layers of graphite felt or wool. The graphite felt has a bulk density of approximately 0.10 g/cm³, a carbon content greater than approximately 99.5 percent, an ash content of approximately 0.05 percent, a thermal conductivity at 1500 degrees Celsius of approximately 0.08 W/mk, and a maximum process temperature of approximately 2400 degrees Celsius. While graphite materials are inherently susceptible to inductive heating, the configuration and arrangement of insulating sheets 136 within induction furnace 100 relative to the other elements of the insulating package, including insulation cylinder 108, minimizes the susceptibility of insulating sheets 136 to significant induction heating. Heat generated by induction heating system 102 is used to heat susceptor 120 rather than being lost on heating insulating sheets 136. As such, susceptor 120 is idealized for heating. Further, insulating sheets 136 are arranged so as to not heat each other and to not heat coil 118 at the elevated operating temperatures within the heating zone 164 of susceptor 120.

The graphite felt has a number of benefits over a traditional insulation package. For example, graphite felt has reduced susceptibility to contamination, has no issue with thermal shock, and functions well in vacuum. Ceramics, on the other hand, are brittle and prone to fracture in the high temperature environment of the furnace, absorb moisture, and may be problematic to maintaining vacuum within the furnace. Glass wool and firebrick, other traditional insulating materials, are not robust to thermal shock, and expel moisture and particulates that contaminate the furnace environment. Molybdenum sheets and other materials that function as a thermal mirror need to be replaced frequency and require a long cooling cycle.

Using insulating sheets 136 with insulation cylinder 108 also lends superior thermal performance as compared to a traditional insulation package constructed of ceramics, molybdenum sheets, glass wool, and/or firebrick. Graphite handles high temperatures well, is easy to machine, has a high resistivity, and is very efficient (e.g., approximately 85-90% efficient). Thus, insulating sheets 136 improve the heating cycle of induction furnace 100 and are approximately 60% more energy efficient and 30% more time efficient as compared to a traditional insulation.

As a result of the enhanced insulating properties gained by the inclusion of insulating sheets 136, induction furnace 100 may be operated to heat a workpiece at temperatures greater than the previous limit of 1200 degrees Celsius without experiencing dielectric breakdown around the coil 118 of induction furnace 100. For example, induction furnace 100 may be operated at temperatures above 1900 degrees Celsius. Also, insulating sheets 136 provide improved temperature control and reduced run-to-run variation. The improved insulation enables a reduction in power consumption and reduced cycle time.

FIG. 1 illustrates induction heating system 102 in a raised or heating position where workpiece 122 is positioned within susceptor 120 and is ready for heating according to induction furnace principles as described above. As shown in FIG. 2, induction heating system 102 is in a lowered position where access to workpiece 122 through a door 160 of chamber 104 is possible. Induction furnace 100 also includes a vacuum pump 162 for creating a vacuum within the chamber 104. Door 160 forms a hermetic seal when closed such that a vacuum created by vacuum pump 162 in an interior volume of chamber 104 is hermetically isolated from an ambient environment outside chamber 104.

In operation of induction furnace 102, the workpiece 122 is in a raised or heating position, i.e., within in a “heating zone” 164 defined by susceptor 120, when a heating operation is being undertaken. The workpiece 122 is then moved to the lowered or cooling position, i.e., within in a “cooling zone” 166 outside of the susceptor 120, when a cooling operation is being undertaken. Moving workpiece 122 to the cooling zone 166 after completion of the heating of workpiece 122 allows for a reduction in the primary overall furnace cycle time. That is, the time required for cooling workpiece 122 is an important factor in the overall furnace cycle time, as traditional cooling becomes increasingly inefficient at lower temperatures. According to embodiments the invention, faster cooling times are achieved at lower temperatures by dropping the parts out of the hot zone 164 and into the cool zone 166 of the vacuum chamber 104.

According to an exemplary embodiment of the invention, induction furnace 102 is constructed so as to facilitate movement of the workpiece 122 between the heating zone 164 and the cooling zone 166 while maintaining a desired vacuum pressure within chamber 104, and is further constructed to include elements to enhance cooling of the workpiece 122. Referring now to FIGS. 3 and 4, induction furnace 102 is shown as including a cooling system 168 for cooling chamber 104 after the workpiece 122 has been heated as desired. Cooling system 168 can include a heat exchanger 170 and a blower 172. Hot gas within the chamber 104 is drawn into the heat exchanger 170, and cooler gas is blown back into chamber 104 by blower 172.

After completion of a heating of workpiece 122, the second cover 128 and tray 130 are dropped using a vacuum-sealed bellows system 174 attached to second cover 116. Bellows system 174 includes a pair of vacuum-sealed bellows 176, 178 attached to respective coupling device 180, 182 that are coupled to chamber 104. A linear actuator 184 such as a piston is coupled to chamber 104 and is coupled to bellows 176, 178 via a plate 186. Embodiments of the invention contemplate that linear actuator 184 may be a pneumatic or hydraulic piston, an electro-mechanical piston, a manual actuator, or the like. The interior volumes of bellows 176, 178 and coupling devices 180, 182 are fluidly coupled to the interior volume of chamber 104. In this manner, movement of linear actuator 184 from the outside of chamber 104 allows the atmosphere and pressure inside chamber 104 to be maintained when plate 186 is moved either away from or toward chamber 104. Accordingly, workpiece 122 can be lowered from heating zone 164 to cooling zone 166.

According to various embodiments, the movement to the cooling position or zone may be governed by a threshold time and/or temperature, and may be triggered by pressure or RGA or partial pressure, or rates of any of these. In one embodiment, the part or workpiece 122 is dropped into the cool section 166 after the part has cooled to approximately 1200° C. This effectively opens the insulated hot zone 164 and allows the cooling gas to pass across the heated parts 122. Once the workpiece 122 drops out of the hot zone 164, the workpiece 122 experiences improved radiative and convective cooling. The area of the cooling zone 166 within chamber 104 has unique temperature control (i.e., ability to quench from high temperature to a lower, controlled temperature), which is particularly useful for heat treating applications. Due to the multi-zone configuration of the vacuum chamber, cooling times may be greatly reduced when compared with cooling inside heating zone 164, and faster cycle times can be met.

Referring now to FIG. 5, and with continued reference to the furnace of FIGS. 3 and 4, a technique 188 for heating and cooling a workpiece is illustrated according to an embodiment of the invention. As illustrated in FIG. 5, certain steps in the technique 188 are considered to be optional, as they would only be performed when the induction furnace is of a type as shown in FIGS. 3 and 4 or in certain workpiece heating/cooling processes. These optional steps in technique 188 are shown in phantom in FIG. 5, so as to highlight that they may not be performed in induction furnaces having a certain geometry/construction.

As shown in FIG. 5, the technique begins at STEP 190 with loading of a workpiece 122 into the furnace 100, such as by way of door 160, with the piece being positioned on tray 130 when it is in a lowered position. The furnace door 160 is then closed, and the technique continues at STEP 192, where the interior of the furnace 100 is brought to a high vacuum (when the induction furnace is configured as a vacuum induction furnace), such as a 10⁻⁷ vacuum pressure, by operation of vacuum pump 162. The workpiece 122 is then raised into the upper hot zone chamber 164 formed by insulating cylinder 108 and susceptor 120 at STEP 194. At STEP 196, the workpiece 122 is flushed with argon, and the interior of the furnace 100 may then be subsequently brought again to a high vacuum depending on the furnace configuration. The workpiece then begins to be heated at STEP 198, with an inert gas (e.g., nitrogen) then being introduced at partial pressure at STEP 200. The workpiece 122 is heated to 200-600° C. with the flowing inert gas to expedite removal of off-gassing, and the technique then continues at STEP 202 where the furnace chamber may again be (optionally) returned to a high vacuum via vacuum pump 162 and heated to a desired processing temperature. A material for coating the workpiece is then introduced if desired at STEP 204.

The workpiece is begun to cool at STEP 206, with such cooling occurring inside the vacuum in certain embodiments. According to an embodiment of the invention, the workpiece is cooled to a temperature below a cooling threshold, and the workpiece is lowered out of the heating zone 164 and into the cooling zone 166 after the threshold has been met using the vacuum sealed bellows system 174 at STEP 208. In this manner, the vacuum pressure created inside the furnace may be maintained when moving the workpiece to the cooling zone 166. A quenching gas such as helium, argon, or nitrogen is then injected at STEP 210, with the gas being injected at atmospheric pressure according to one embodiment.

According to various embodiments, gas may be injected at STEP 210 at either or both of the high and low workpiece positions, as faster cooling times can be achieved at lower temperatures by dropping the workpiece out of the hot zone 164 into the cool section 166 of the vacuum chamber 104. Thus, the process of injecting gas at STEP 210 can incorporate a repositioning of the workpiece down into the cooling zone 166 outside of susceptor 120 by lowering hot zone tray 130. As set forth above, the lowering of the workpiece 122 down into the cooling zone 166 may be governed by a threshold time and/or temperature, and may be triggered by pressure or RGA or partial pressure, or rates of any of these. In one embodiment, the workpiece 122 is dropped into the cool section after the workpiece has cooled to approximately 1200° C., as further cooling below this threshold temperature is achieved most efficiently by passing cooling gas across the heated workpiece 122 when it is located in the cooling zone 166. By selectively positioning the workpiece 122 in the hot zone 164 and the cooling zone 166, the cooling time of the workpiece can be reduced greatly and faster cycle times can be met.

Referring now to FIG. 6, an induction furnace 220 is shown according to another embodiment of the invention. While the induction furnace 220 is constructed to have an insulating jacket assembly 110 identical to that shown and described with respect to FIGS. 1-4 (with the insulating sheets 136 arranged in layers to cover the exterior surfaces of susceptor 120), the induction furnace 220 shown in FIG. 6 is constructed as a furnace that does not operate at a vacuum, but instead provides cooling to a workpiece 118 via a gasflow that has a non-recirculated flow path. As shown in FIG. 6, gas blower 144 provides a supply of cooling gas into the interior volume of the chamber 104 that is blown across the workpiece 118. After the cooling gas is blown across the workpiece 118, it is not recirculated through a cooling system for subsequent use, but is instead vented from the chamber 104 of induction furnace 220 out through an exit port 222 and to the ambient environment after cooling of the workpiece is performed.

Therefore, according to one embodiment of the invention, an induction furnace for heating a workpiece includes a chamber, an insulation cylinder positioned within the chamber, and an induction coil positioned to surround at least a portion of the insulation cylinder. A susceptor is positioned within the insulation cylinder and inductively heated by the induction coil when a current is provided to the induction coil. An insulating jacket assembly including one of a carbide material and a refractory metal is positioned in a space between the insulating cylinder and the susceptor.

According to another embodiment of the invention, an induction furnace includes a chamber having a susceptor positioned therein. An interior volume of the susceptor defines a zone within the chamber for heating a workpiece. The induction furnace also includes an insulation package having a fused quartz cylinder positioned around the susceptor and a graphite jacket positioned between the fused quartz cylinder and the susceptor. A coil surrounds the insulation package and is configured to inductively heat the interior volume of the susceptor when a current is provided to the induction coil.

According to yet another embodiment of the invention, a method of making an induction furnace includes providing a vacuum chamber, coupling an insulation cylinder within the vacuum chamber, and coupling an induction coil to surround at least a portion of the insulation cylinder. The method also includes coupling a susceptor within the insulation cylinder and encapsulating the susceptor with an insulating jacket, wherein the insulating jacket comprises one of a carbide material and a refractory metal.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

1. An induction furnace for heating a workpiece, the induction furnace comprising:

a chamber;

an insulation cylinder positioned within the chamber;

an induction coil positioned to surround at least a portion of the insulation cylinder;

a susceptor positioned within the insulation cylinder, the susceptor being inductively heated by the induction coil when a current is provided to the induction coil; and

an insulating jacket assembly comprising one of a carbide material and a refractory metal, the insulating jacket assembly positioned in a space between the insulating cylinder and the susceptor.

2. The induction furnace of claim 1 wherein the insulating jacket assembly is sized to substantially surround the susceptor.

3. The induction furnace of claim 1 wherein the insulating jacket assembly further comprises a plurality of layers.

4. The induction furnace of claim 3 wherein a first portion of the plurality of insulating layers surrounds a side wall of the susceptor.

5. The induction furnace of claim 3 wherein a second portion of the plurality of insulating layers is positioned above a top surface of the susceptor; and

wherein a third portion of the plurality of insulating layers is positioned below a bottom surface of the susceptor.

6. The induction furnace of claim 1 further comprising:

a first graphite plate; and

a second graphite plate; and wherein the first and second graphite plates are positioned to retain the insulating jacket assembly against the susceptor.

7. The induction furnace of claim 1 wherein the insulating jacket assembly comprises a graphite felt.

8. The induction furnace of claim 1 wherein the insulating jacket assembly comprises a material that is transparent to induction.

9. The induction furnace of claim 1 further comprising a linear actuator coupled to the chamber and a bottom cover of the insulation cylinder; and

wherein the linear actuator is configured to translate the bottom cover between a raised position, wherein the workpiece is positioned in a heating zone of the induction furnace within the susceptor, and a lowered position, wherein the workpiece is positioned in a cooling zone of the induction furnace, outside of the susceptor.

10. The induction furnace of claim 9 further comprising a bellows system coupled to the bottom surface of the insulation cylinder;

wherein the bellows system has an interior volume fluidly coupled to an interior volume of the chamber; and

wherein the bellows system is configured to maintain a hermetic seal in the chamber from an ambient environment during movement of the bottom cover between the raised and lowered positions.

11. An induction furnace comprising:

a chamber having a susceptor positioned therein, wherein an interior volume of the susceptor defines a zone within the chamber for heating a workpiece;

an insulation package comprising: a fused quartz cylinder positioned around the susceptor; and a graphite jacket positioned between the fused quartz cylinder and the susceptor; and

a coil surrounding the insulation package and configured to inductively heat the interior volume of the susceptor when a current is provided to the induction coil.

12. The induction furnace of claim 11 wherein the graphite jacket comprises a plurality of layers of graphite felt.

13. The induction furnace of claim 11 wherein a first portion of the graphite jacket surrounds a side wall of the susceptor;

wherein a second portion of the graphite jacket covers a top cover of the susceptor; and

wherein a third portion of the graphite jacket covers a bottom cover of the susceptor.

14. The induction furnace of claim 11 further comprising:

a first graphite plate positioned between the fused quartz cylinder and a top surface of the susceptor; and

a second graphite plate positioned between the fused quartz cylinder and a bottom surface of the susceptor.

15. The induction furnace of claim 11 further comprising:

a linear actuator coupled to a bottom cover of the fused quartz cylinder and configured to move the bottom cover in vertical manner between a raised position and a lowered position; and

a vacuum-sealed bellows system configured to maintain a vacuum pressure in the chamber during movement of the bottom cover of the fused quartz cylinder between the raised position and the lowered position by way of the linear actuator.

16. A method of making an induction furnace comprising:

providing a vacuum chamber;

coupling an insulation cylinder within the vacuum chamber;

coupling an induction coil to surround at least a portion of the insulation cylinder;

coupling a susceptor within the insulation cylinder; and

encapsulating the susceptor with an insulating jacket, wherein the insulating jacket comprises one of a carbide material and a refractory metal.

17. The method of claim 16 further comprising positioning a pair of graphite plates at respective top and bottom exterior surfaces of the susceptor.

18. The method of claim 16 wherein encapsulating the susceptor with an insulating jacket comprises covering exterior surfaces of the susceptor with a plurality of layers of graphite felt.

19. The method of claim 16 further comprising:

encapsulating a side wall of the susceptor with a first portion of the insulating jacket;

encapsulating a top surface of the susceptor with a second portion of the insulating jacket; and

encapsulating a bottom surface of the susceptor with a third portion of the insulating jacket.

20. The method of claim 16 further comprising:

coupling a bellows system to a bottom surface of the insulation cylinder, the bellows system having an interior volume fluidly coupled to an interior volume of the chamber;

coupling a linear actuator to the bellows system; and

configuring the linear actuator to selectively translate the bottom cover of the insulation cylinder between open and closed positions.