A multifunctional hollow filter rod making device

Abstract

The application provides a multifunctional hollow filter rod preparation device, and relates to the technical field of hollow filter rods.The device comprises a forming cavity, a forming inner core located at least partially in the forming cavity, and a gas supply part for communicating with the forming cavity.The gas supply part comprises a heating bin for communicating with the forming cavity, a filter bin for communicating with the heating bin, and a gas pump arranged between the heating bin and the filter bin.The pure air filtered through the filter bin is heated at the heating bin under the drive of the gas pump, and the heated air finally reaches the forming cavity to contact with the polylactic acid fiber tows in the forming cavity, thereby achieving the forming effect of the polylactic acid fiber hollow filter rod.The application has the advantages of simple structure, the use of hot air heating to complete the filter rod forming, the preparation of the polylactic acid material hollow filter rod, the preparation of the multi-layer structure hollow filter rod, and the effective avoidance of the irregular problem of the filter rod hole wall when heated by steam, and the hollow filter rod has good forming effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hollow filter rods, in particular, the present application relates to a multifunctional hollow filter rod preparation device. BACKGROUND

[0002] With the development of cigarette production technology, the types and appearance of cigarettes are more diversified, and cigarettes with unique shapes are more likely to be loved by people, thus giving birth to this new type of hollow filter rod.

[0003] Using acetate tow to produce hollow (hollow) filter rods is a mature process technology. For example, Chinese patent invention patent CN113576024A discloses a hollow filter rod forming equipment, which comprises an opener, a filter rod forming device, a drawing device and a cutting device; the opener, the filter rod forming device, the drawing device and the cutting device are connected in sequence, and the opener comprises a first roller column conveying assembly, a first glycerol adding assembly, a second roller column conveying assembly and a second glycerol adding assembly; the first roller column conveying assembly and the first glycerol adding assembly are arranged at intervals; the second roller column conveying assembly and the second glycerol adding assembly are arranged at intervals, the filter rod forming device processes the acetate tow of the first glycerol adding assembly and the second glycerol adding assembly into a filter rod, the drawing device draws the filter rod to move to the cutting device, and the cutting device cuts the filter rod into segments.

[0004] Since polylactic acid has the advantages of low price, easy degradation and no pollution compared with acetate, the preparation and research of polylactic acid filter rods are very important now; but using polylactic acid tow to produce hollow (hollow) filter rods, the current process technology is indeed very lacking.

[0005] Acetate tow is used to produce hollow (hollow) filter rods, which are made into filter rods by steam heating and rapid solidification, but hollow (hollow) filter rods are usually round holes, but in the molding process, by selecting different shaped mandrels, various special shaped hollow (hollow) filter rods can be made, if steam heating is used, the bending part of the special shape is easy to produce steam condensation, causing unevenness of the molded hollow hole wall, and the filter rod shape is more irregular.

[0006] Moreover, polylactic acid PLA is a thermoplastic aliphatic polyester with a low glass transition temperature, which will appear rigidification and thermal collapse under high temperature conditions. In the initial stage of producing hollow (hollow) filter rods with polylactic acid tow, steam heating method is also used to trial-produce filter rods, but the steam temperature is too high, the effect is not good, the filter rod shape is irregular, and normal production is impossible.

[0007] Therefore, in order to solve the above problems, it is necessary for us to design a reasonable and efficient multifunctional hollow filter rod preparation device. SUMMARY

[0008] The present application aims to provide a multifunctional hollow filter rod preparation device, which is simple in structure, adopts a hot air heating mode to complete filter rod forming, can prepare a hollow filter rod made of polylactic acid material, can prepare a hollow filter rod with a multi-layer structure, and effectively avoids the problem of irregular filter rod hole wall when steam heating, and has good hollow filter rod forming effect.

[0009] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0010] A multifunctional hollow filter rod preparation device comprises a forming cavity, a forming inner core located at least in part in the forming cavity, and a gas supply part for communicating with the forming cavity, wherein the gas supply part comprises a heating bin for communicating with the forming cavity, a filter bin for communicating with the heating bin, and a gas pump arranged on the side of the filter bin close to the forming cavity.

[0011] The pure air filtered through the filter bin is heated at the heating bin under the driving of the gas pump, and the heated air finally contacts the polylactic acid fiber tows in the forming cavity, thereby achieving the forming effect of the polylactic acid fiber hollow filter rod.

[0012] As a preferred embodiment of the present application, the temperature of the air heated by the heating bin ranges from 65 DEG C to 85 DEG C.

[0013] As a preferred embodiment of the present application, the gas pump is a dry oil-free gas pump.

[0014] As a preferred embodiment of the present application, an outer sleeve cavity is arranged outside the forming cavity, and a first through hole is arranged between the outer sleeve cavity and the forming cavity.

[0015] As a preferred embodiment of the present application, the outer sleeve cavity is communicated with a steam bin.

[0016] The steam in the steam bin enters the forming cavity and contacts the acetate tow in the forming cavity, thereby achieving the forming effect of the acetate tow filter rod.

[0017] As a preferred embodiment of the present application, the forming inner core comprises a first inner core for extending into the forming cavity when heating the polylactic acid fiber tows and a second inner core for extending into the forming cavity when heating the acetate tows, and the outer diameter of the second inner core is greater than that of the first inner core.

[0018] As a preferred embodiment of the present application, the first inner core is provided with a hollow cavity, a second through hole is arranged on the outer side wall of the first inner core, and the first inner core is arranged in communication with the heating bin.

[0019] As a preferred embodiment of the present application, the second inner core is a solid cylindrical member.

[0020] As a preferred embodiment of the present application, the inner sidewall of the heating bin is provided with an electric heating wire and a temperature sensor electrically connected to the electric heating wire.

[0021] As a preferred embodiment of the present application, the inner sidewall of the forming cavity is smooth.

[0022] The multifunctional hollow filter rod preparation device has the advantages of simple structure, and can complete filter rod forming by using hot air heating, can prepare a hollow filter rod made of polylactic acid, can prepare a hollow filter rod with a multi-layer structure, and effectively avoids the problem of irregular filter rod hole wall when steam heating, and has good hollow filter rod forming effect. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1 FIG. 1 is a schematic diagram of the overall structure of an embodiment of the multifunctional hollow filter rod preparation device of the present application;

[0024] Fig. 2 FIG. 2 is a schematic diagram of the overall structure of another embodiment of the multifunctional hollow filter rod preparation device of the present application;

[0025] Fig. 3 FIG. 3 is a schematic diagram of the cross section of the (polylactic acid) hollow filter rod prepared by the multifunctional hollow filter rod preparation device of the present application;

[0026] Fig. 4 FIG. 4 is a schematic diagram of the structure for heating the acetate fiber tow when preparing a multi-layer hollow filter rod by the multifunctional hollow filter rod preparation device of the present application;

[0027] Fig. 5 FIG. 5 is a schematic diagram of the structure for heating the polylactic acid fiber tow when preparing a multi-layer hollow filter rod by the multifunctional hollow filter rod preparation device of the present application;

[0028] Fig. 6 FIG. 6 is a schematic diagram of the cross section of the multi-layer hollow filter rod prepared by the multifunctional hollow filter rod preparation device of the present application;

[0029] In the figure: 1, forming cavity, 2, forming inner core, 21, first inner core, 22, second inner core, 3, gas supply part, 31, heating bin, 32, filter bin, 33, air pump, 4, outer sleeve cavity, 41, steam bin. DETAILED DESCRIPTION

[0030] The following are specific embodiments of the present application, which further describe the technical solutions of the present application, but the present application is not limited to these embodiments.

[0031] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement and steps of the modules and steps set forth in these embodiments do not limit the scope of the present application unless otherwise specifically stated.

[0032] At the same time, it should be understood that, for ease of description, the process shown in the attached diagram is not performed in isolation, but rather involves multiple steps that overlap.

[0033] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0034] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0035] Techniques, methods, and systems known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of this specification.

[0036] Example 1: As Figs. 1 to 3 As shown, a multifunctional hollow filter rod preparation device includes a molding cavity 1, a molding inner core 2 with at least a portion located in the molding cavity 1, and an air supply unit 3 for communicating with the molding cavity 1. The air supply unit 3 includes a heating chamber 31 for communicating with the molding cavity 1, a filter chamber 32 for communicating with the heating chamber 31, and an air pump 33 disposed on the side of the filter chamber 32 near the molding cavity 1.

[0037] Driven by the air pump 33, the pure air filtered by the filter chamber 32 is heated in the heating chamber 31. The heated air finally reaches the forming cavity 1 and comes into contact with the polylactic acid fiber bundles in the forming cavity 1, thereby achieving the forming effect of polylactic acid fiber hollow filter rod.

[0038] In this invention, the heat forming process of cellulose acetate filter rods is relatively well-established, but the heat forming process of polylactic acid is lacking. Since polylactic acid has the advantages of low price, easy degradation and no pollution compared to cellulose acetate, the research on the preparation of polylactic acid filter rods is very important. The focus of this invention is to heat-prepare hollow filter rods of polylactic acid fiber.

[0039] Further, since the acetate fiber hollow filter rod mostly adopts the steam heating mode, the steam temperature can reach above 170℃. Since polylactic acid is a thermoplastic aliphatic polyester, the glass transition temperature is low, and under high temperature conditions, the rigidity and thermal collapse conditions will appear, so the high temperature steam heating mode is used for the preparation and forming of the polylactic acid hollow filter rod, and the forming effect is poor.

[0040] After many experiments and summaries, it is found that the heating preparation required for the polylactic acid hollow filter rod is less than 100℃, and the steam will condense into water, so the steam heating mode cannot be used.

[0041] Therefore, we creatively propose to directly use air heating to prepare and form the polylactic acid hollow filter rod, and the experimental verification has high feasibility, as follows:

[0042] The pure air is heated to a predetermined temperature, and then contacted with the opened polylactic acid fiber tows sent into the forming unit to heat and solidify the polylactic acid fiber tows to form a polylactic acid filter rod.

[0043] Specifically, the multifunctional hollow filter rod preparation device comprises a forming cavity 1, a forming inner core 2 located at least partially in the forming cavity 1, and a gas supply part 3 for communicating with the forming cavity 1. The gas supply part 3 comprises a heating bin 31 for communicating with the forming cavity 1, a filter bin 32 for communicating with the heating bin 31, and a gas pump 33 arranged on the side of the filter bin 32 close to the forming cavity 1.

[0044] When the forming inner core 2 extends into the forming cavity 1, the polylactic acid fiber tows can reach the space between the outside of the forming inner core 2 and the inside of the inner wall of the forming cavity 1, and contact with the heated air to form a polylactic acid hollow filter rod with a hollow hole (the shape depends on the structure of the forming inner core 2).

[0045] In addition, the air reaching the forming cavity 1 needs to be pure and the temperature needs to reach a predetermined temperature, so the filter bin 32 is used to filter the air to ensure that the pure air standard is met, and then the pure air is heated and input into the forming cavity 1.

[0046] In summary, under the drive of the gas pump 33, the pure air filtered through the filter bin 32 is heated at the heating bin 31, and the heated air finally reaches the forming cavity 1 and contacts with the polylactic acid fiber tows in the forming cavity 1 to achieve the forming effect of the polylactic acid fiber hollow filter rod.

[0047] Of course, the above-mentioned predetermined temperature, i.e. the heating temperature of polylactic acid, is the temperature range of the air heated by the heating bin 31, which is 65℃ to 85℃.

[0048] The experiment investigates the influence of different hot air temperature on filter rod forming production and filter rod physical index and appearance, and the results are as follows:

[0049] Table 1.1 Influence of different hot air temperature on polylactic acid forming (24.0mm x 120mm)

[0050]

[0051]

[0052] That is, the hollow filter rod is produced by using polylactic acid filament, when the hot air temperature is below 60℃, the production condition is poor, the filter rod is deformed, the roundness is poor, and the hardness is low, because the filter rod cannot be quickly solidified during the forming process; when the hot air temperature is 65-85℃, the production condition is normal, the filter rod index and appearance meet the requirements; when the hot air temperature is more than 90℃, the production condition is poor, and the roundness and concentricity of the filter rod are poor. Therefore, when the hollow filter rod is produced, the hot air temperature is 65-85℃, which is far lower than the high-temperature steam temperature used for preparing acetate filter rods.

[0053] Of course, the inner side wall of the heating bin 31 is provided with an electric heating wire and a temperature sensor electrically connected with the electric heating wire, and once the temperature deviates from the interval of 65-85℃, an alarm is sent in time.

[0054] In the present application, there are two ways for the heated air to enter the forming cavity 1:

[0055] The first way is the outside entering type, that is, the heated air flows into the forming cavity 1 from the outside of the forming cavity 1, and the outer side wall of the forming cavity 1 is provided with a through hole for communicating with the heating bin 31, as shown in Fig. 1 .

[0056] The second way is the center entering type, that is, the heated air flows into the forming cavity 1 from the center of the forming inner core 2 of the forming cavity 1, and the forming inner core 2 is hollow, the forming inner core 2 is in communication with the heating bin 31, and the outer side of the forming inner core 2 is provided with a through hole for communicating with the forming cavity 1, Fig. 2 as shown.

[0057] The multifunctional hollow filter rod preparation device of the present application has a simple structure, and the forming of the filter rod is completed by using the hot air heating mode, so that the hollow filter rod made of polylactic acid can be well prepared.

[0058] Example two, still as Figs. 1 to 3As shown, only one embodiment of the present application, on the basis of example one, in a multifunctional hollow filter rod preparation device, the air pump 33 is a dry oil-free air pump, which can avoid impurities and water vapor mixed into the air to be heated, preferably the air pump 33 is arranged between the filter bin 32 and the heating bin 31, that is, the air first passes through the filter bin 32, then passes through the air pump 33, and then passes through the heating bin 31 to reach the forming cavity 1, that is, the air pump 33 is arranged behind the filter bin 32, so that dust and impurities will not be twisted into the air pump 33; At the same time, the air pump 33 is arranged in front of the heating bin 31, so that the air pump 33 does not need to bear high temperature damage.

[0059] In addition, during the preparation of the polylactic acid hollow filter rod, a camera and a sensor are arranged at the forming cavity 1 to check the polylactic acid fiber tow supply in a timely manner and issue an alarm in a timely manner when an abnormality occurs.

[0060] It should be noted that the specification of the polylactic acid fiber tow supply at the forming cavity 1 is preferably 30000d×2-33000d×2 (equivalent to 60000-66000d).

[0061] The effects of different hot air temperatures on filter rod forming production and filter rod physical indexes and appearance were investigated by experiments, and the results are as follows:

[0062] Table 1.2 Different total denier polylactic acid tow forming conditions (24.0mm×120mm)

[0063]

[0064] That is, when the total denier of the polylactic acid tow is below 26000d×2 (i.e. 52,000 deniers), the production condition is poor, the filter rod roundness is poor, and the hardness is low; when the total denier of the polylactic acid tow is 30000d×2-33000d×2 (equivalent to 60000-66000d), the production condition is normal, and the filter rod indexes and appearance meet the requirements; when the total denier of the polylactic acid tow exceeds 35000d×2 (i.e. 7 million deniers), the production condition becomes worse, and the filter rod index fluctuation becomes larger. Therefore, for the production of conventional hollow (hollow) filter rods, the specification of polylactic acid tow is 30000d×2-33000d×2 (equivalent to 60000-66000d).

[0065] In addition, during the preparation of the polylactic acid hollow filter rod, an application port for applying glyceryl triacetate is arranged at the forming cavity 1, and glyceryl triacetate needs to be applied to the polylactic acid fiber tow to improve the forming effect.

[0066] The effects of different glyceryl triacetate application amounts on filter rod forming production and filter rod physical indexes and appearance were investigated by experiments, and the results are as follows:

[0067] Table 1.3 Influence of different triacetin application amounts on molding (24.0 mm x 120 mm)

[0068]

[0069]

[0070] That is, the hollow (hollow) filter rod is produced by using polylactic acid filament, when the triacetin application amount is less than 10%, the production is acceptable, but the filter rod is not formed after molding, and the hardness is low; when the triacetin application amount is 12% to 16%, the production is normal, and the filter rod index and appearance meet the requirements; when the triacetin application amount is more than 18%, the production is poor, and the filter rod index fluctuates greatly. Therefore, when producing polylactic acid hollow (hollow) filter rod, the triacetin application amount is 12% to 16%.

[0071] Of course, the inner side wall of the molding cavity 1 is smooth.

[0072] Finally, the outer side of the molding cavity 1 is provided with a sleeve cavity 4, and the sleeve cavity 4 and the molding cavity 1 are provided with a first through hole.

[0073] When the heating air enters the molding cavity 1 in the form of outside entry, the heating air can first reach the sleeve cavity 4, and then reach the molding cavity 1 from the first through hole. Of course, the first through hole is provided with a plurality of and is uniformly arranged, so that hot air enters all around the outer side of the molding cavity 1.

[0074] As shown in Example Three, Figs. 1 to 6 As shown in Example Three, it is only one of the embodiments of the present application, on the basis of any of the above embodiments, in a multifunctional hollow filter rod preparation device, due to the heating mode of air, the specific heat capacity of air is small, and the heating efficiency of the filter rod is low. When preparing large filter rods (filter rods with large diameter), the thickness of the heated polylactic acid filter rod (the distance between the outer wall of the molding inner core 2 and the inner wall of the molding cavity 1, which is represented by thickness) may not meet the requirements. In order to facilitate the molding effect, the large hollow filter rod can be provided as a multi-layer structure, that is, a hollow filter rod with a cellulose acetate material on the outside and a polylactic acid fiber material on the inside, as shown in Example Four, Fig. 6 In this way, the thickness of the polylactic acid fiber filament can be reduced, and the process requirement can be reduced.

[0075] The present application can still complete the preparation of the above-mentioned double-layer hollow filter rod.

[0076] Since the heating temperature requirement of the acetate fiber part is high, and the heating temperature of the polylactic acid fiber part is low, in order to facilitate the preparation of the multi-layer hollow filter rod, the acetate fiber part should be heated and formed first, and then the polylactic acid fiber part is heated and formed after the temperature drops, at this time, the acetate fiber part which has been formed will not be affected, and a double-layer hollow filter rod is prepared.

[0077] Therefore, the steam for heating the acetate fiber part is the outside entering type, and the air for heating the polylactic acid fiber part is the center entering type.

[0078] That is, the sleeve cavity 4 is communicated with the steam bin 41;

[0079] The steam (the temperature can reach 170℃) in the steam bin 41 enters the forming cavity 1 and contacts the acetate fiber tow in the forming cavity 1, so as to achieve the forming effect of the acetate fiber tow filter rod.

[0080] Further, the forming inner core 2 includes a first inner core 21 for extending into the forming cavity 1 when heating the polylactic acid fiber tow and a second inner core 22 for extending into the forming cavity 1 when heating the acetate fiber tow, and the outer diameter of the second inner core 22 is greater than that of the first inner core 21.

[0081] That is, the second inner core 22 is first extended into the forming cavity 1 to heat and form the acetate fiber part, and then the first inner core 21 is extended into the forming cavity 1 to heat and form the polylactic acid fiber part after the temperature drops.

[0082] Here, the first inner core 21 is provided with a hollow cavity, the second through hole is arranged on the outer side wall of the first inner core 21, and the first inner core 21 is arranged in communication with the heating bin 31, so that the heating air of the heating bin 31 can pass through the hollow cavity in the first inner core 21 and the second through hole of the first inner core 21 to reach the forming cavity 1.

[0083] Among them, the first inner core 21 can be peach heart shape, square, round, plum blossom shape or other various shapes, of course, the second inner core 22 is a dense structure cylindrical piece.

[0084] In this way, when the second inner core 22 is extended into the forming cavity 1 to heat and form the acetate fiber part, the acetate fiber part can be understood as a concentric ring structure, and the steam will not accumulate at the bending part to affect the forming effect; on the contrary, when the first inner core 21 is extended into the forming cavity 1 to heat and form the polylactic acid fiber part, since pure air is entered, there is no worry about any air accumulation at the special-shaped first inner core 21, and the forming effect can still be guaranteed.

[0085] However, with the development of the process, it is foreseeable that the thickness of the heatable polylactic acid filter rod can be larger and larger, and large or even super-large hollow filter rods can be prepared, and the large hollow filter rods are made of pure polylactic acid material.

[0086] However, the flow of the hot air entering the forming cavity 1 needs to be accurately controlled, and therefore, a flow meter needs to be added between the heating bin 31 and the filtering bin 32.

[0087] The multifunctional hollow filter rod preparation device has a simple structure, and is capable of completing filter rod forming by using a hot air heating mode, and is capable of not only preparing a hollow filter rod made of polylactic acid material, but also preparing a hollow filter rod with a multi-layer structure, and effectively avoids the problem of irregular filter rod hole walls when steam heating, and has good hollow filter rod forming effect.

[0088] The present application is not limited to the above specific embodiments, and various modifications and changes can be made to the present application. Any modification, equivalent replacement, improvement, etc. made to the above embodiments according to the technical essence of the present application shall be included in the protection scope of the present application.

Claims

1. A multi-functional hollow filter rod making apparatus characterized by: The molding cavity (1), at least one part of the molding core (2) in the molding cavity (1), and the air supply part (3) for communicating with the molding cavity (1), the air supply part (3) includes a heating bin (31) for communicating with the molding cavity (1), a filter bin (32) for communicating with the heating bin (31), and a gas pump (33) arranged on the side of the filter bin (32) close to the molding cavity (1); When the hollow filter rod is produced by using polylactic acid fiber tows, the pure air filtered through the filter bin (32) is heated at the heating bin (31) under the driving of the gas pump (33), the air heated to a temperature range of 65-85℃ finally reaches the molding cavity (1) and contacts with the polylactic acid fiber tows in the molding cavity (1), achieving the molding effect of the polylactic acid fiber hollow filter rod. When a large filter rod is prepared, the molding core (2) includes a first core (21) for extending into the molding cavity (1) when heating the polylactic acid fiber tows and a second core (22) for extending into the molding cavity (1) when heating the acetate fiber tows, the outer diameter of the second core (22) is greater than that of the first core (21), the large hollow filter rod is arranged in a multi-layer structure, i.e. the hollow filter rod with acetate fiber material on the outside and polylactic acid fiber material on the inside, the second core is first extended into the molding cavity, the acetate fiber part is heated and molded, and then the first core is extended into the molding cavity, the polylactic acid fiber part is heated and molded, which will not affect the molded acetate fiber part, and a double-layer hollow filter rod is prepared.

2. A multi-functional hollow filter rod making apparatus according to claim 1, characterized by: The gas pump (33) is a dry oil-free gas pump.

3. A multi-functional hollow filter rod making apparatus according to claim 1, wherein: The molding cavity (1) is provided with an outer sleeve cavity (4), and a first through hole is arranged between the outer sleeve cavity (4) and the molding cavity (1).

4. A multi-functional hollow filter rod making apparatus according to claim 3, wherein: The outer sleeve cavity (4) is communicated with a steam bin (41). The steam in the steam bin (41) enters the molding cavity (1) and contacts with the acetate fiber tows in the molding cavity (1), achieving the molding effect of the acetate fiber filter rod.

5. A multi-functional hollow filter rod making apparatus according to claim 4, characterized in that: The first core (21) is provided with a hollow cavity, a second through hole is arranged on the outer wall of the first core (21), and the hollow cavity of the first core (21) is communicated with the heating bin (31).

6. A multi-functional hollow filter rod making apparatus according to claim 4, wherein: The second core (22) is a dense cylindrical structure.

7. The multi-functional hollow filter rod making apparatus according to claim 1, wherein: The inner wall of the heating bin (31) is provided with an electric heating wire and a temperature sensor electrically connected with the electric heating wire.

8. The multi-functional hollow filter rod making apparatus according to claim 1, wherein: The inner wall of the molding cavity (1) is smooth.

Images