Patent Application
20170246772
The present invention generally relates to a rotomolding process and more specifically relates to a process for manufacturing modular rotomolded structures and components.
In the recent years, the assembly processes in automobile industry have become quite time consuming and inefficient. The automotive body and chassis assembly process has evolved over the years to a stage where there is not much thought on changing the methodology of the process being set since years. Additionally, the current processes do not provide for modularity of the components making it difficult for assembling, integration and dissembling. Modularity is the degree to which a system's components may be separated and recombined. For example, the current automotive body assembly process consists of a Body in White (BIW) which could be a body on chassis or a monocoque construction. BIW refers to the stage in automotive design or automobile manufacturing in which the car body's sheet metal components have been welded together. The chassis is the underpart of a motor vehicle, consisting of a frame on which the body is mounted.
The BIW is processed on the main assembly line which is supplied with the major panel's sub-assemblies. The sub-assemblies have flanges that help in interfacing with each other to assemble as a single body unit. The processes used as of today are welding, riveting or bonding with adhesives as per the set guidelines of assembly. The BIW is either welded or riveted or bolted to the chassis.
Further, it is painted by a process which involves immersion coating processes, paint curing processes, under-body sealant application, polyvinyl chloride (PVC) and wax applications, and painting spray booths operations. The painted body is then fitted with the sub-components like engine, suspensions brakes and tires. Also, electrical harnesses are fitted on the body panels with the help of either clamps or tie straps as per the requirement. The electrical harness is routed through the main subassemblies of the body. This body is then trimmed on the trim chassis final assembly line.
The existing solutions in rotation molding disclose about the use of reinforcements in metal and structural foam filling between the walls of the rotomolded component. This is to provide strength to the structure. They also have multilayer material, which are inseparable or non-modular. This is mainly to cater to different chemical characteristics required by application. The rotomolding leads to increase in strength by use of reinforcements and use of structural foam. The process in itself has the potential to combine many functional parts into one.
However, the use of foam for strengthening of structure is not always reliable as we are not able to predict the exact strength of the structure which gets molded, because the introduction of foam and its curing is process dependent. There is a need felt for using a material whose strength characteristics can be predetermined. It could be increased or decreased depending on the application. Also, it should be lighter than steel or aluminum which are currently used as reinforcements.
All the above conventional processes add to the cost and time of assembly, which could be reduced by using process of rotomolding. Therefore, there is a need for a method of manufacturing integrated modular structure using rotomolding process, which is optimal in terms of cost, assembly time and provides for ease of component integration. Additionally, the electric harness does not required to be replaced unless there is a damage which is mainly caused due to tampering of the harness by user. Therefore, there is also a need for a method by which the electric harness is embedded into the base structure.
An embodiment of the present invention describes a method of manufacturing integrated modular structure using rotomolding process. The method comprises preparing at least a pair of molds embedded with at least one electric harness, wherein the pair of mold having a base mold and a first mold joined to form an enclosure, filling a first material in the base mold of the pair of molds, providing a heating and cooling cycle, wherein during heating at least the pair of molds being rotated for evenly spreading the molten first material and embedding the electric harness in the molten first material, obtaining a first molded part yielded by at least the pair of molds, and obtaining a second molded part yielded by at least a pair of molds, wherein the pair of molds having the first molded part and a second mold part, thereby the first molded part, the second molded part and the at least one embedded electric harness together forming the integrated modular structure.
In one embodiment obtaining the second molded part comprises a) replacing the first mold with the second mold when the pair of molds is cooled to a predefined temperature, b) filling a second material between the second mold and the base mold, wherein the first molded part is in the base mold, c) providing a heating and cooling cycle to the pair of molds, wherein, during the heating of the second mold, the base mold is shielded to restrict melting of the first material, the second material heats up and melts causing the molten second material to spread within the pair of molds forming connection at edge of the modular structure, and d) obtaining the integrated modular structure with the harness being located at the center of the integrated modular structure section.
The aforementioned aspects and other features of the present invention will be explained in the following description, taken in conjunction with the accompanying drawings, wherein:
The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments. The present invention can be modified in various forms. Thus, the embodiments of the present invention are only provided to explain more clearly the present invention to the ordinarily skilled in the art of the present invention. In the accompanying drawings, like reference numerals are used to indicate like components.
The specification may refer to “an”, “one” or “some” embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.
As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes”, “comprises”, “including” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations and arrangements of one or more of the associated listed items.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The electric harness 303 is flexible in structure and cannot be embedded in the mold as it will sway during rotation movement in the mold. To ensure that the electric harness 303 is embedded inside the structure being molded, it is necessary that the electric harness 303 does not move during the molding process. The movement of electric harness 303 does not allow the same to be centered in the structure, resulting in making the structure stronger in one portion while weaker in the other portion. Therefore, in order to avoid movement of the electric harness 303, one of the molds in the mold set has a screw 304 with spring 305 to hold the electric harness 303 in place. It is to be noted that any other method know in the art may be utilized to hold the electric harness 303 in place. As per the method of the invention, the electric harness is embedded well inside the structure and hence cannot be tampered with. Additionally, the harness does not burn or catch fire due to single coil wire and lack of exposure to oxygen. For prevention against over surge, a fuse may be provided or separate ground line may be provided in each structure. Hence, it is to be noted that the electric harness does not have to be replaced unless in case of extreme damage due an accident.
According to an embodiment of the present invention, providing strength in the lateral direction of the electric harness 303 ensures that when the melted polymer powder flows onto the electric harness 303, it will not sway or deform due to the viscosity of the molten polymer. The electric harness 303 is supported at a length which does not exceed 100 mm. While bending the electric harness 303, the radius of bend depends upon the geometry of the harness. For example, if the thickness is more than 3 mm, the bend radius needs to be greater than 40 mm. This is to ensure that it is held firmly and does not sway due to the forces during the process.
According to one embodiment of the present invention, the electric harness 303 is placed in a mold 501 and a single core solid wire 502 is enclosed in the electric harness 303. The screw 503 along with a nut 504, provide a holding mechanism that holds the electric harness 303 at a distance of 3 mm from the mold 501. A spacer 505 is embedded along with the electric harness 303. Any other holding mechanism known in the art may be used.
In case the distance of the electric harness 303 is kept less than 3 mm from the mold face, the electric harness 303 becomes soft in shorter time by reaching heat distortion temperature and this is due to faster convection of heat to the electric harness structure. Also, the molten polymer does not flow completely around the electric harness 303 which is undesirable. Therefore, the electric harness material has to be selected such that the heat distortion temperature is more than the melting point of the polymer powder being introduced in the mold for making the structure. Accordingly, the distance to be maintained between the harness and the mold face needs to be optimal.
According to an exemplary embodiment of the invention, the ideal oven temperature for the proposed process is 300 degree Celsius and peak indoor air temperature (PIAT) inside the mold set is 220 degree Celsius. The PIAT is dependent on the size of the part being molded i.e., on the amount of polymer powder loaded inside the mold to get a specific thickness of the final molded part. The heating of the mold is controlled at 220 degree Celsius and is heated at various temperatures with a predefined time difference. The heat melts the powdered polymer inside the mold and time taken depends on the size of the part being molded and the weight of powdered polymer added inside the mold.
The electric harness 303 is a single solid conductor which assists in better heat dissipation as the surface area of the electric harness 303 is more along with solid core wires. These solid core wires reduce the flexibility of the electric harness 303, which enables it to be held firmly at a distance from the mold face during the mold rotation.
Further, there could be static structures as well as dynamic structures. The two dynamic structures could be connected by simple knuckle type geometry which allows electrical connection between them. This reduces the time for assembly as the structures can be put together by having different male and female geometries on the interfacing structures. Thus, also creating an electrical connection between them which can have poka-yoke so that there cannot be a wrong way of connection.
Further, when the electric harness 303 is placed inside the structure it needs to be held at the center of the section i.e., at the neutral axis so that no strain is applied on the electric harness 303. The cross-sectional view as represented in the
Step 1: The electric harness 303 is held in a first mold 1102 and a first material 1103 is introduced in powder form in a base mold 1101. The base mold 1101 and the first mold 1102 are attached in such a way forming an enclosure.
Step 2: The oven is heated at, for example, 300 degree Celsius and the mold set is rotated about two axes. The PIAT reaches 220 degree Celsius which is controlled by factors like heating time, quantity of material inside the mold set.
Step 3: The heating and rotation of the mold set allows the material to melt and flow in between the electric harness and the mold. It also causes the molten material to flow over the electric harness 303 to embed it. The gap at which the electric harness 303 is held from the mold plays an important role.
Step 4: The mold set is removed from the oven and cooling cycle is applied to the part so formed inside the mold set. This cooling cycle depends on size of the molded part.
Step 5: First mold 1102 is removed from the mold set after the molded part is cooled to a predefined temperature such as 80 degree Celsius. The temperature of the part should be such that it can fuse with the next second material of the trim which will be introduced.
Step 6: First mold 1102 is replaced with the second mold 1104. The second material 1105 gets introduced between the base mold 1101 and second mold 1104, when the previously molded part is still inside the base mold 1101. In one embodiment, the second material is same as the first material and in another embodiment the second material is different from the first material.
Step 7: Before starting the heating process of mold set, a shield 1106 is provided on the base mold 1101 to protect it from being exposed to the oven and heat. This shield 1106 on the base mold 1101 avoids melting of the formed molded part due to the heat applied. In one exemplary embodiment, thermoelectric device is stuck to the mold for providing shield to the base mold. The present invention is adapted to use any method/device known in the art for providing shielding.
Step 8: Heating of the mold set would heat the second mold 1104 and the second material 1105 that is in powdered form would melt. As the base mold 1101 is shielded, temperature is controlled and restricts melting of the first material 1103.
Step 9: The second material 1105 that is now in molten state flows in the mold and bind at the edge of the previously molded part which is in base mold 1101. The cooling cycle is then applied as per the size of the part formed. The nature of connection made between the first material 1103 and the second material 1105 is illustrated in
Step 10: Final component 1107 with the embedded electric harness 303 along with the trim 1104 (i.e. second molded part 1104) in the structure is obtained. This forms the complete modular structure of the invention along with the integrated electric harness.
In one embodiment, the carbon fiber cloth 1201 should be maintained at a distance of minimum 20 mm from the edge of the mold wall. This distance mentioned is approximate and would dependent on geometry of mold and the application. The curing time for a resin would be dependent on type of resin being used to cure the CFC. The advantage of the process is that, the CFC is separated from the polymer of the part by heating the part above the melting point of the polymer. This makes the structure recyclable and the polymer could be reused for making new structures. It is to be noted that the carbon fiber cloth may or may not be embedded depending on the application requirement.
Although the exemplary embodiment has been for manufacturing rotomolded components for automotive, it is to be noted that the method of the invention may be extended for manufacturing modular rotomolded components for various applications. The other applications, for which the method of the invention may be used to create modular rotomolded structures, are, but not limited to, manufacturing cabinets, internal separators in building, airplane component, industrial components, etc. Thus, the method of the invention may be used for manufacturing rotomolded structure with an embedded electric harness for any application.
All equivalent relationships to those illustrated in the drawings and described in the invention are intended to be encompassed by the present invention. The examples used to illustrate the embodiments of the present invention, in no way limit the applicability of the present invention to them. It is to be noted that those with ordinary skill in the art will appreciate that various modifications and alternatives to the details could be developed in the light of the overall teachings of the disclosure, without departing from the scope of the invention. For example, the first material and the second material could be same or different. The temperatures mentioned are exemplary only and the optimal temperature required would be dependent on the application. The distance to be maintained between the electric harness and the mold wall would vary depending upon the application. The distance between the carbon fiber cloth and the mold wall edge would depend on the application. The width of the slots in the carbon fiber cloth would vary depending on the amount of requirement of strength of the modular structure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 3607/MUM/2014 | Nov 2014 | IN | national |
This application is a Continuation of International Patent Application No. PCT/IN2015/000411, filed Nov. 6, 2015, which claims the benefit of and priority to Indian Patent Application No. 3607/MUM/2014, filed Nov. 17, 2014. The entire disclosures of the foregoing applications are hereby incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/IN2015/000411 | Nov 2015 | US |
| Child | 15596980 | US |
