Precise plastic mold for consumer electronics
By inserting high-thermal conductivity alloy thermal strips into the electronic cigarette insert and accelerating heat transfer using thermal conductivity and nanofluid, the problem of low cooling efficiency of the insert is solved and faster cooling time is achieved.
Patent Information
- Application Number
- CN202510187212.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-20
- Publication Date
- 2025-04-01
AI Technical Summary
The thermal conductivity of the electronic cigarette insert is average, resulting in poor cooling efficiency of the mold, resulting in a longer cooling time.
Insert alloy thermal conductivity strips with better thermal conductivity into the insert, and heat transfer is accelerated through the thermal conductivity parts and nanofluids on the alloy thermal conductivity strips and improve thermal conductivity efficiency.
It improves thermal conductivity, shortens cooling time, and solves the problem of poor cooling efficiency of electronic cigarette inserts.
Smart Images
Figure CN119734405A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of plastic state forming, and in particular to a precision plastic mold for consumer electronic products. Background Art
[0002] Electronic cigarettes are consumer electronic products. The processing of electronic cigarette shells usually adopts the injection molding process. Plastic molds are indispensable injection molding tools in the injection molding process. The plastic shell materials of electronic cigarettes are mostly high-temperature materials. Since the temperature of high-temperature materials can easily lead to various problems in the injection molding process, the cooling effect of the mold is particularly important. Electronic cigarette inserts are key components in electronic cigarette molds and are usually used to mold electronic cigarette shells. Therefore, the cooling water channel design of electronic cigarette inserts in injection molds is particularly critical. Reasonable cooling water channel design can quickly take away the heat in the mold and significantly improve the cooling efficiency, thereby ensuring the dimensional accuracy and yield rate of the product.
[0003] The size of the electronic cigarette insert is small, and the length of the water channel can be easily limited in a limited space, which will cause the cooling water to flow out of the insert quickly. The cooling water is less effective in taking away heat. Therefore, 3D printing is used to print electronic cigarette inserts. 3D printing can produce complex cooling water channels to improve cooling efficiency.
[0004] However, in the process of implementing relevant technical solutions, it was found that at least the following technical problems exist: if the cost of 3D printing the entire insert is high, in order to save costs, electronic cigarette inserts are generally printed by grafting. Grafting printing refers to the method of first using CNC workpiece processing for the insert base with a relatively simple structure, and then printing one or more electronic cigarette shell mold cores with complex conformal cooling water channels on the insert base. The materials of the 3D printed part and the base part are generally mold steel. Although mold steel has good strength, hardness and wear resistance, the thermal conductivity of mold steel is general, which will eventually lead to poor cooling efficiency of the mold and a long cooling time. Summary of the invention
[0005] The present invention provides a precision plastic mold for consumer electronic products, thereby solving the technical problem in the prior art that the thermal conductivity of electronic cigarette inserts is average, resulting in poor cooling efficiency of the mold and a long cooling time. The present invention inserts an alloy thermal conductive strip with better thermal conductivity into the insert, thereby improving the thermal conductivity efficiency and shortening the cooling time.
[0006] The present invention provides a precision plastic mold for consumer electronic products, comprising an insert, wherein the insert comprises a machined mold base and a grafted printed shell mold core, wherein the shell mold core comprises a mold core bottom plate attached to the top surface of the mold base and a plurality of convex core pieces arranged and printed on the mold core bottom plate, an alloy heat-conducting strip is inserted between the mold base and the shell mold core, the thermal conductivity of the alloy heat-conducting strip is higher than the thermal conductivity of the mold base and the shell mold core, a plug hole 1 is opened in the mold base corresponding to each of the convex core pieces, a plug hole 2 connected to the plug hole 1 is formed in the convex core piece, and a conformal water channel is formed in the convex core piece and located outside the plug hole 2, wherein the alloy heat-conducting strip comprises: a plug bar 1, which is completely inserted in the plug hole 1; a plug bar 2, which is inserted between the plug hole 2 and the plug hole 1 and plugged into the end of the plug bar 1; and a plug bar 3, which is completely inserted in the plug hole 2 and inserted into the end of the plug bar 2.
[0007] Furthermore, the width of the convex core piece near one end of the mold base is greater than that of the other end, and side grooves are formed on both sides of the second plug hole near the bottom of the convex core piece; a hollow hole is formed in the second insertion strip, and a symmetrically arranged heat-conducting part is slidably connected in the hollow hole, and the heat-conducting part includes a heat-conducting back plate and a plurality of heat-conducting fins formed on the heat-conducting back plate, and the heat-conducting fins are used to enter the side grooves of the convex core piece and fit to the groove walls of the side grooves; a guide hole 1 is formed in the first insertion strip and passes through the two end surfaces of the first insertion strip; a guide hole 2 is formed in the second insertion strip, one end of which is connected to the hollow hole and the other end of which is connected to the first guide hole; the first guide hole and the second guide hole are both used to pass nanofluids and flow into the hollow hole.
[0008] Furthermore, the alloy heat-conducting strip also includes an insertion rod, which is inserted into the first guide hole and the second guide hole, and is used to prevent the nanofluid in the hollow hole from flowing out.
[0009] Furthermore, a guide plate is formed at one end of the thermal conductive back plate close to the guide hole 2, and the guide plate is located on the side of the thermal conductive back plate facing the thermal conductive fins, and the angle between the thermal conductive back plates in the heat conductive parts on both sides toward the guide hole 2 is an obtuse angle.
[0010] Furthermore, a slide groove is formed on the inner wall of the hollow hole, and a slide bar which is gap-matched with the slide groove is formed on the heat conducting member.
[0011] Furthermore, a heat dissipation groove is formed on the bottom surface of the mold base at the position of each of the first insertion holes, and a plurality of heat dissipation fins are formed on one end of the first insertion strip away from the second insertion strip, and the heat dissipation fins are located in the heat dissipation groove.
[0012] Furthermore, an end of the first plug-in strip close to the second plug-in strip and an end of the second plug-in strip close to the third plug-in strip are both provided with plug-in holes, an end of the second plug-in strip close to the first plug-in strip and an end of the third plug-in strip close to the second plug-in strip are both formed with plug-in blocks, and the plug-in blocks and the plug-in holes are interference fit.
[0013] One or more technical solutions provided in the present invention have at least the following technical effects or advantages: 1: Due to the use of alloy thermal conductive strips, after the electronic cigarette shell is injection molded, the two thermal conductive parts on the alloy thermal conductive strip can accelerate the heat transfer of the convex core part in the insert, and the nanofluid also accelerates the heat transfer. The thermal conductive core of the gold thermal conductive strip is higher than the mold base and the shell mold core. The first, second and third inserts in the alloy thermal conductive strip can transfer heat to the mold base of the insert and the shell mold core respectively, thereby improving the thermal conductivity efficiency and shortening the mold cooling time, solving the technical problems of poor cooling efficiency and long cooling time of electronic cigarette inserts in the prior art.
[0014] 2: Due to the various shapes of electronic cigarette shells, the machined mold base in the insert can be used multiple times, and shell mold cores of different shapes can be printed on the mold base according to different needs. Therefore, the alloy thermal conductive strip is designed to be composed of multiple sections, and different inserts can be replaced to adapt to shell mold cores of different shapes, reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 This is a schematic diagram of the overall structure of a precision plastic mold for consumer electronic products in an embodiment of the present invention; Figure 2 It is a schematic diagram of the structure of the insert in the embodiment of the present invention; Figure 3 for Figure 1 Schematic cross-sectional view of ; Figure 4 for Figure 2 A cross-sectional schematic diagram of another cut surface of the middle shell mold core; Figure 5 An exploded schematic diagram of an insert in an embodiment of the present invention; Figure 6 for Figure 5 Another perspective of the picture; Figure 7 An exploded schematic diagram of an alloy heat-conducting strip in an embodiment of the present invention; Figure 8 is a cross-sectional schematic diagram of a second cutting strip according to an embodiment of the present invention; Fig. 9 A result schematic diagram of a heat conducting member in an embodiment of the present invention; Fig.10 is a cross-sectional schematic diagram of a first cutting in an embodiment of the present invention; In the figure: 100, insert; 101, mold base; 1011, heat dissipation groove; 1012, cooling water channel; 102, shell mold core; 1021, mold core bottom plate; 1022, convex core piece; 103, alloy heat conduction strip; 31, insert strip one; 311, guide hole one; 312, heat dissipation fin; 32, insert strip two; 321, hollow hole; 3211, slide groove; 32 2. Guide hole two; 33. Insert strip three; 34. Heat conducting part; 341. Heat conducting back plate; 342. Heat conducting fin; 343. Guide plate; 344. Slide bar; 35. Insert rod; 301. Plug hole; 302. Plug block; 11. Plug hole one; 12. Plug hole two; 121. Side groove; 13. Conformal water channel; 200. Fixed mold; 300. Moving mold; 400. Mold core. DETAILED DESCRIPTION
[0016] The embodiment of the present invention discloses a precision plastic mold for consumer electronic products. By inserting an alloy heat-conducting strip 103 into an insert 100, the heat-conducting core of the alloy heat-conducting strip 103 is higher than the mold base 101 and the shell mold core 102. The insert strip 1 31, the insert strip 2 32 and the insert strip 3 33 in the alloy heat-conducting strip 103 can accelerate the heat transfer to the mold base 101 and the shell mold core 102 of the insert 100, and the two heat-conducting parts 34 on the alloy heat-conducting strip 103 can also accelerate the heat transfer of the convex core part 1022 in the insert 100, thereby solving the technical problem in the prior art that the thermal conductivity of the electronic cigarette insert is average, resulting in poor cooling efficiency of the mold and a long cooling time.
[0017] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.
[0018] Reference Figure 1 and Figure 2 A precision plastic mold for consumer electronic products, including an insert 100, a fixed mold 200, a movable mold 300, and a mold core 400. The mold core 400 is located between the fixed mold 200 and the movable mold 300, and the insert 100 is fixedly installed in the mold core 400. The insert 100 includes a mold base 101 and a shell mold core 102. The mold base 101 can be made by CNC machining, and the shell mold core 102 can be printed by a 3D printer on the top surface of the mold base 101. The materials of the mold base 101 and the shell mold core 102 can both be mold steel. Mold steel has good strength, hardness and wear resistance, and the cost is also low. In addition, the shell mold core 102 includes a core bottom plate 1021 and a convex core piece 1022. The convex core piece 1022 is a part used to form an electronic cigarette shell. A plurality of evenly arranged convex core pieces 1022 are formed on the core bottom plate 1021, so that multiple electronic cigarette shells can be formed during one injection molding.
[0019] Reference Figure 3-Figure 5The mold base 101 is provided with a vertical socket 11, the cross section of which is rectangular, there are multiple sockets 11 and the number is the same as the number of the convex core pieces 1022, each socket 11 corresponds to each convex core, and the bottom surface of the mold base 101 is provided with a heat dissipation groove 1011 at the position of each socket 11, the cross section of the heat dissipation groove 1011 is also rectangular, and the area is larger than the cross-sectional area of the socket 11, and the mold base 101 is also provided with a cooling water channel 1012. The convex core piece 1022 is formed with a conformal water channel 13 during the printing process, and the conformal water channel 13 is connected with the cooling water channel 1012, and the cooling water channel 1012 and the conformal water channel 13 are both loop designs, and the cooling system in the mold will pass cooling water into the cooling water channel 1012 of the mold base 101, and the cooling water will enter the conformal water channel 13 of the convex core piece 1022, thereby cooling the insert 100. The convex core piece 1022 is formed with the second socket 12 during the printing process. The second socket 12 overlaps and is connected to the first socket 11. In addition, for the stability of the convex core piece 1022, the width of the convex core piece 1022 at one end close to the mold base 101 is greater than that at the other end, and the outer surface is an inclined surface. The portion of the convex core piece 1022 where the width gradually increases does not have the function of injection molding to form an electronic cigarette shell, and the straight portion of the convex core piece 1022 has the function of injection molding an electronic cigarette shell. Therefore, the portion of the second socket 12 close to the bottom of the convex core piece 1022 is thicker. Therefore, during the printing process of the convex core piece 1022, there is enough space on both sides of the second socket 12 close to the bottom of the convex core piece 1022 to form side grooves 121, and the side grooves 121 are vertical rectangular grooves.
[0020] Reference Figure 5-Figure 7 An alloy heat-conducting bar 103 is inserted between the mold base 101 and the shell mold core 102 . The material of the alloy heat-conducting bar 103 may be a copper alloy. The thermal conductivity of the alloy heat-conducting bar 103 is higher than that of the mold base 101 and the shell mold core 102 . The alloy heat-conducting strip 103 is composed of multiple sections, and the alloy heat-conducting strip 103 includes an insert strip 1 31, an insert strip 2 32, and an insert strip 33. The insert strip 1 31 is completely inserted into the insert hole 11; one end of the insert strip 2 32 is inserted into the insert hole 2 12 and crosses the side groove 121, and the other end is inserted into the insert hole 11; the insert strip 33 is completely inserted into the insert hole 2 12, and is located on the side of the side groove 121 away from the insert hole 11; the end of the insert strip 1 31 close to the insert strip 2 32 and the end of the insert strip 2 32 close to the insert strip 33 are both provided with a plug-in hole 301, and the end of the insert strip 2 32 close to the insert strip 1 31 and the end of the insert strip 33 close to the insert strip 2 32 are both formed with a plug-in block 302, and the plug-in block 302 and the plug-in hole 301 are interference fit, so that the insert strip 1 31, the insert strip 2 32, and the insert strip 33 can be tightly connected.
[0021] Reference Figure 8-Figure 10A hollow hole 321 is provided in the second plug strip 32. The hollow hole 321 is a vertical hole, and the openings on both sides are respectively used to correspond to the side grooves 121 on both sides of the second plug hole 12. A sliding groove 3211 is provided on the inner wall of the hollow hole 321. The sliding groove 3211 is used to slide and connect the heat conducting member 34. Two heat conducting members 34 are provided and symmetrically arranged on both sides of the hollow hole 321. The two heat conducting members 34 are respectively used to slide into the side grooves 121 on both sides of the second plug hole 12. The heat-conducting member 34 includes a heat-conducting back plate 341 and a plurality of heat-conducting fins 342. The heat-conducting back plate 341 is vertically arranged in the hollow hole 321. The plurality of heat-conducting fins 342 are arranged on a side surface of the heat-conducting back plate 341 facing the outside of the hollow hole 321. When both heat-conducting members 34 are located in the hollow hole 321, there is a gap between the heat-conducting back plates 341 on both sides. A slide bar 344 is formed on the heat-conducting member 34 to match the gap with the slide groove 3211.
[0022] Continue to refer to Figure 8-Figure 10 The first plug 31 is provided with a guide hole 311 penetrating through both end surfaces of the first plug 31, and the second plug 32 is provided with a guide hole 322 whose one end is connected to the hollow hole 321 and the other end is connected to the guide hole 311. The guide hole 311 and the guide hole 322 are both used to pass nanofluid and flow into the hollow hole 321. The nanofluid has the characteristic of high thermal conductivity. The nanofluid can be formed by adding nanoparticles (such as copper and aluminum oxide) to a basic liquid (such as water and oil). In addition, a guide plate 343 is formed at one end of the heat-conducting back plate 341 close to the guide hole 322. The guide plate 343 is parallel to the heat-conducting fins 342. The guide plate 343 is located on the side of the heat-conducting back plate 341 facing the heat-conducting fins 342. The angle between the heat-conducting back plates 341 in the heat-conducting parts 34 on both sides facing the guide hole 322 is an obtuse angle. Therefore, when the nanofluid flows out of the guide hole 322, it will enter between the heat-conducting back plates 341 of the heat-conducting parts 34 on both sides under the guidance of the guide plate 343. The nanofluid will push the heat-conducting parts 34 on both sides away from each other and enter the side grooves 121 on both sides of the convex core part 1022, and finally the heat-conducting fins 342 on the heat-conducting parts 34 will hit the groove wall of the side groove 121. Furthermore, the alloy heat conductive strip 103 also includes an insertion rod 35, which is inserted into the guide hole 1 311 at one end of the insertion strip 1 31 away from the insertion strip 2 32, and enters the guide hole 2 322. When the nanofluid enters the hollow hole 321, the insertion rod 35 is inserted into the guide hole 1 311 and the guide hole 2 322. The insertion rod 35 can prevent the nanofluid in the hollow hole 321 from flowing out. The material of the insertion rod 35 can also be copper alloy, which can also play a heat conductive role.
[0023] Reference Figure 6 and Figure 7A plurality of heat dissipation fins 312 are formed at one end of the first insert 31 away from the second insert 32, and the heat dissipation fins 312 are located in the heat dissipation groove 1011. When the alloy heat conductive strip 103 transfers the heat in the mold base 101 and the shell mold core 102 to one end of the bottom surface of the mold base 101, the heat dissipation fins 312 at the end of the first insert 31 can be used to quickly dissipate the heat on the alloy heat conductive strip 103, further improving the cooling efficiency of the insert 100.
[0024] The present invention can be explained by the following operation mode: The mold base 101 is first processed by CNC machine, and then the shell mold core 102 is grafted on the top surface of the mold base 101 by 3D printing. The mold base 101 and the shell mold core 102 form the insert 100 of the electronic cigarette shell. Then, the insert strip 1 31, the insert strip 2 32 and the insert strip 3 33 in the alloy heat conductive strip 103 are plugged and connected. After the connection, the alloy heat conductive strip 103 is inserted into the insert 100 from the socket 1 11 on the mold base 101 until the plug strip hits the bottom of the socket 2 12 of the convex core piece 1022. At this time, the two heat conductive parts 34 in the alloy heat conductive strip 103 correspond to the two side grooves 121 in the convex core piece 1022, and then the heat conductive strip 34 is passed into the guide hole 1 311. The nanofluid will enter the hollow hole 321 through the guide hole 322, and then under the guidance of the guide plate 343, the nanofluid will enter between the heat-conducting back plates 341 of the heat-conducting parts 34 on both sides, and the nanofluid will push the heat-conducting parts 34 on both sides away from each other and enter the side grooves 121 on both sides of the convex core part 1022, and finally the heat-conducting fins 342 on the heat-conducting parts 34 will hit the groove wall of the side grooves 121, and the nanofluid will be retained in the hollow hole 321 and the side grooves 121, and then the insertion rod 35 is inserted into the guide hole 1 311 and the guide hole 2 322, and the insertion rod 35 can prevent the nanofluid in the hollow hole 321 from flowing out, and the insertion rod 35 also plays a heat-conducting role.
[0025] Therefore, after each injection molding of the electronic cigarette shell, the two heat-conducting parts 34 on the alloy heat-conducting strip 103 can accelerate the heat transfer of the convex core part 1022 in the insert 100, and the nanofluid also accelerates the heat transfer. The heat-conducting core of the alloy heat-conducting strip 103 is higher than the mold base 101 and the shell mold core 102. The insert 1 31, the insert 2 32 and the insert 3 33 in the alloy heat-conducting strip 103 can transfer heat to the mold base 101 and the shell mold core 102 of the insert 100 respectively. This solves the technical problem that the thermal conductivity of the electronic cigarette insert in the prior art is general, resulting in poor cooling efficiency of the mold and a long cooling time. The alloy heat-conducting strip 103 with better thermal conductivity is inserted into the insert 100, thereby improving the thermal conductivity efficiency and shortening the cooling time.
[0026] In addition, since the shapes of the electronic cigarette shell are various, the machined mold base 101 in the insert 100 can be used multiple times, and the shell mold core 102 of different shapes can be printed on the mold base 101 according to different needs. Therefore, the alloy heat conductive strip 103 is designed to be composed of multiple sections, and different inserts 33 can be replaced to adapt to the shell mold core 102 of different shapes, reducing costs. Furthermore, when the insert 100 is scrapped, the nanofluid can be poured out and can be recycled, further reducing costs.
[0027] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.
[0028] What has been described above are only preferred specific implementations of the embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and concepts of the present invention, which should be covered by the protection scope of the present invention.
Claims
1. A precision plastic mold for a consumer electronic product, comprising an insert (100), wherein the insert (100) comprises a machined mold base (101) and a grafted printed shell mold core (102), wherein the shell mold core (102) comprises a core mold bottom plate (1021) attached to the top surface of the mold base (101) and a plurality of convex core pieces (1022) arranged and printed on the core mold bottom plate (1021), characterized in that: An alloy heat-conducting strip (103) is inserted between the mold base (101) and the shell mold core (102); the heat conductivity of the alloy heat-conducting strip (103) is higher than that of the mold base (101) and the shell mold core (102); a first plug hole (11) is provided in the mold base (101) corresponding to each of the convex core pieces (1022); a second plug hole (12) connected to the first plug hole (11) is formed in the convex core piece (1022); a conformal water channel (13) is formed in the convex core piece (1022) and is located outside the second plug hole (12); wherein the alloy heat-conducting strip (103) comprises: Insert strip one (31), which is completely inserted into the insertion hole one (11); Insertion strip 2 (32) is inserted between the insertion hole 2 (12) and the insertion hole 1 (11), and is plugged into the end of the insertion strip 1 (31); Insertion strip three (33) is completely inserted into the insertion hole two (12) and is inserted at the end of the insertion strip two (32).
2. A precision plastic mold for consumer electronic products as claimed in claim 1, characterized in that: The width of the convex core member (1022) at one end close to the mold base (101) is greater than that at the other end, and side grooves (121) are formed on both sides of the second insertion hole (12) close to the bottom of the convex core member (1022); a hollow hole (321) is formed in the second insertion strip (32), and a symmetrically arranged heat conducting member (34) is slidably connected in the hollow hole (321), and the heat conducting member (34) includes a heat conducting back plate (341) and a plurality of heat conducting fins (342) formed on the heat conducting back plate (341), and the heat conducting fins (34 2) used to enter the side groove (121) of the convex core member (1022) and fit to the groove wall of the side groove (121), the first insert (31) is provided with a first guide hole (311) penetrating through the two end surfaces of the first insert (31), the second insert (32) is provided with a second guide hole (322) having one end connected to the hollow hole (321) and the other end connected to the first guide hole (311), the first guide hole (311) and the second guide hole (322) are both used to allow nanofluid to flow into the hollow hole (321).
3. A precision plastic mold for consumer electronic products as claimed in claim 2, characterized in that: The alloy heat-conducting strip (103) further comprises an insertion rod (35), wherein the insertion rod (35) is inserted into the first flow guide hole (311) and the second flow guide hole (322), and the insertion rod (35) is used to prevent the nanofluid in the hollow hole (321) from flowing out.
4. A precision plastic mold for consumer electronic products as claimed in claim 2, characterized in that: A guide plate (343) is formed at one end of the heat-conducting back plate (341) close to the second guide hole (322); the guide plate (343) is located on a side of the heat-conducting back plate (341) facing the heat-conducting fin (342); and the angle between the heat-conducting back plates (341) in the heat-conducting parts (34) on both sides toward the second guide hole (322) is an obtuse angle.
5. A precision plastic mold for consumer electronic products as claimed in claim 2, characterized in that: The inner wall of the hollow hole (321) is provided with a sliding groove (3211), and the heat conducting member (34) is formed with a sliding strip (344) which is gap-matched with the sliding groove (3211).
6. A precision plastic mold for consumer electronic products as claimed in claim 2, characterized in that: The bottom surface of the mold base (101) is provided with a heat dissipation groove (1011) at the position of each of the first plug holes (11), and a plurality of heat dissipation fins (312) are formed at one end of the first plug strip (31) away from the second plug strip (32), and the heat dissipation fins (312) are located in the heat dissipation groove (1011).
7. A precision plastic mold for consumer electronic products as claimed in claim 1, characterized in that: An end of the first plug-in strip (31) close to the second plug-in strip (32) and an end of the second plug-in strip (32) close to the third plug-in strip (33) are both provided with plug-in holes (301), and an end of the second plug-in strip (32) close to the first plug-in strip (31) and an end of the third plug-in strip (33) close to the second plug-in strip (32) are both formed with plug-in blocks (302), and the plug-in blocks (302) and the plug-in holes (301) are interference-fitted.