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1 Introduction The cabinet structure forms the basis for the assembly of low-voltage switchgear; therefore, the manufacturing process of the cabinet becomes the foundation of that foundation. As a cabinet, it must not only meet the functional requirements for combining various electrical units (such as uniform design, standardization of combinations, and allocation of functions), but also fulfill the inherent requirements of a cabinet itself (such as durability, neatness and aesthetics, and ease of adjustment). Due to the varying requirements for cabinet structures and the different manufacturing methods employed by various producers, it is not possible to require that their manufacturing processes be exactly identical. However, there are also some key process characteristics of general significance in manufacturing; these characteristics will be briefly introduced here in conjunction with the selection of the cabinet structure. 2 Cabinet Structure and Manufacturing Features The cabinet structure and its manufacturing process can be distinguished based on aspects such as structural form, connection methods, and materials used for the components. 2.1 Classified by structural form: (1) Fixed type: It enables various electrical components to be fixed in definite positions within the cabinet. The shape of the cabinet is generally cubic, such as screen-type or box-type, and there are also frustum-shaped types like table-type. This type of cabinet comes in single rows as well as in arranged rows. To ensure the dimensional accuracy of the cabinet, components are typically assembled in stages; usually, two halves or the left and right sides are assembled first to form the cabinet structure, or the external shape requirements are met first before the internal components of the cabinet are connected one after another. The lengths of the parts that make up the edges of the cabinet must be correct (with negative tolerances) in order to ensure the various geometric dimensions, and thus meet the requirements regarding the overall shape. For the two side surfaces of the cabinet, considering the arrangement requirements, there must be no protrusions in the middle. Furthermore, from an installation perspective, the bottom surface must not be sunken. In arranged installation, a level foundation is a prerequisite; however, there are certain errors in both the levelness of the foundation and the cabinets themselves. During arrangement, efforts should be made to offset lateral differences so as to prevent their accumulation, as such accumulation can cause deformation of the cabinets, affect busbar connections, lead to improper installation of components and stress concentration, and even impact the lifespan of electrical equipment. Therefore, when arranging them, it is advisable to use the highest point of the foundation as the installation reference point, and then gradually adjust and expand the arrangement. Under conditions where the flatness of the base surface is satisfactory and predictable, it is also possible to expand from the center toward the sides to ensure that the cumulative differences are evenly distributed. To facilitate adjustment and counteract tolerance accumulation, the width tolerances of the cabinet are set to negative values. After the various components of the cabinet structure are assembled, shaping may also be carried out as needed to meet the dimensional and geometric requirements of each part. When manufacturing cabinets that are standardized or produced in large quantities, it is essential to make full use of fixtures to ensure the correct and consistent structure. It is advisable to use the bottom surface as the reference plane for the fixtures, and the positioning elements within these fixtures should be arranged in such a way as to facilitate handling during operation. As for the outer doors of the cabinets, which are prone to damage during transportation and installation, they are generally adjusted uniformly during the installation process. (2) Draw-out type: The draw-out type consists of a fixed cabinet body and a removable unit containing main electrical components such as switches. The removable part should be easy to move, and it must be able to be positioned accurately once inserted; in addition, drawers of the same type and specifications should be interchangeable. The manufacturing method for the cabinet body in the draw-out type is basically similar to that of the cabinet body in the fixed type. However, due to the requirements of interchanging, the precision of the cabinet body must be improved, and the relevant parts of its structure must have sufficient adjustment capacity. As for the movable components, they need to be able to be swapped as well as to securely hold the main components; therefore, they require high mechanical strength and high precision, with the relevant parts also needing sufficient adjustment capacity. The process characteristics of manufacturing drawer-type low-voltage cabinets are: (1) the fixed and movable parts must have a unified reference frame ； (2) The relevant components must be adjusted to their optimal positions; specialized standard tools should be used for this adjustment, including standard cabinets and standard drawers ； (3) The error of critical dimensions must not exceed the allowable limits ； (4) The interchangeability of drawers of the same type and specification must be possible*. 2.2 Classified by connection method: (1) Welded type: Its advantages are easy processing and durability* ； The disadvantages are large errors, easy deformation, difficulty in adjustment, poor aesthetics, and the workpieces generally cannot be pre-plated. In addition, certain requirements are placed on the welding fixture: ① It must have good rigidity and not be affected by the deformation of the workpiece ； ②Its external dimensions are slightly larger than the nominal dimensions of the workpiece, which helps to compensate for the shrinkage that occurs after welding ； ③Smooth, simple, and easy to operate; minimize rotating mechanisms to avoid jamming ； ④To prevent welding corrosion and facilitate maintenance and adjustment, the workpiece support must be properly selected, and anti-corrosion padding should also be added to the support. The post-welding deformation of workpieces is caused by stress resulting from the expansion of molecules at the welding site due to heating, which leads to microscopic displacement; this displacement cannot be reversed after cooling. To overcome the effects of deformation, the shaping process must be considered. The common methods for shaping include: ① Predicting the degree of deformation of the workpiece through testing, and forcing the workpiece to deform in the opposite direction before welding, in order to achieve the desired dimensions after welding ； ②Corrected using the positive method after welding ； ③The relative contraction after impact and pressure welding is utilized to achieve stress equilibrium ； ④The relatively loose and protruding areas after heating welding are treated to achieve the same degree of contraction as the welded area ； ⑤Perform overall heat treatment on the components if necessary. Furthermore, the selection of welding points, the direction of the welds, the welding sequence, and spot welding positioning all have an impact on post-welding deformation. Proper handling can reduce this deformation, but this depends on the specific circumstances. (2) Fastener connection: Its advantages include suitability for pre-plating of workpieces, ease of adjustment and beautification, the possibility of standardizing component designs, and the ability to pre-produce inventory, with minimal dimensional errors in the framework’s shape. The disadvantage is that it is not as strong as welding, it requires high precision in the components, and the processing cost is relatively higher. Fasteners are generally standard components; the main types include conventional screws, nuts, and rivets as well as pull rivets. There are also clamping nuts that can be pre-tightened and fine-tuned, pre-tightened locking nuts, and self-tapping screws. There are also special fastening screws (as most low-voltage cabinets imported from abroad use such special fastening screws). Process features: Shaping is achieved using fixtures, positioning is carried out with tooling, and pressure washers may be used as needed ； Riveting usually requires drilling, and pre-plated parts need to have their coating protected from damage ； For components manufactured using precision machining centers or specialized equipment, if a slight gap can be maintained between the various connection holes and the diameter of the fasteners, it is possible to assemble them without the use of fixtures and to achieve one-time forming ； The tightening of guiding and positioning components should be carried out by first using specialized measuring tools for positioning, and then checking with standard fixtures. (3) Welding and fastening hybrid connection: It can combine the advantages of the two methods mentioned above; generally, electric welding is used for the connections in the cabinet body, while the variable or adjustable parts are connected using fasteners. Due to the difficulties in coating larger cabinets after welding, their surfaces are usually treated with paint. For outdoor cabinets that use pre-coated materials as components and still require welding, the welded areas can be treated with thermally sprayed metal. 2.3 Classification by material source of components: (1) Profiles: These include angle steel, channel steel, as well as special-shaped pipes and special-shaped channels. Components made of angle steel and channel steel are mostly connected by welding; during processing, the connection ends must fit together with minimal gaps, otherwise it will affect the welds and increase deformation ； For the connection of special-shaped steel pipe components, either welding or fasteners can be used; generally, specialized connectors are required at the connection points, and these connectors must be sturdy and properly fitted, otherwise it will affect the appearance of the cabinet. Uniform special-shaped steel pipes are used, with holes arranged at uniform intervals (moduli) on a uniform surface; standard connecting components are employed, and the cabinets are assembled according to uniform modular systems. This facilitates cabinet design as well as the preparation of components and production processes. However, a large number of holes need to be drilled yet only a few are actually used, and space utilization is somewhat limited. The manufacturing process for this type of cabinet is characterized by the need to ensure the versatility and precision of its components and connectors. The basic structure of the cabinet is often reinforced by end plates. In addition to special-shaped steel pipes, the components of this type of cabinet can also be replaced by C-shaped channel steel made of steel plates or reinforced rectangular tubes. C-shaped channel steel is suitable for plating, while it is difficult to remove acid residues from reinforced rectangular tubes after pickling, which makes them prone to rusting after plating; therefore, a choice must be made based on specific circumstances. (2) Plate members (excluding the aforementioned C-shaped channel steel and ribbed rectangular tubes) can be shaped entirely according to requirements, with no predefined shaping constraints. This type of structural design involves a large amount of work, with few variations once it is finalized. Welding is primarily used in the main parts of the structure, while connections at areas where variations occur are usually made using fasteners (such as in low-voltage control boxes and consoles). Since sheet structures are often fabricated by welding or one-time forming, it is necessary to overcome the effects of contraction or relative bulging on the sheet surface caused by welding; therefore, the weld points should be spaced evenly, the welds should be smooth, the parts should be shaped after welding, the edges should be straight, and the middle sections on both sides must not protrude beyond the front and rear edges. If there are partitions in the middle, welding should be carried out after the sides have been properly processed. For desktop control cabinets, panels are the most suitable materials for construction; when multiple cabinets are arranged side by side, their surfaces should be adjusted and positioned uniformly after they are arranged together. 3 Conclusion From the above analysis, it can be seen that the various choices regarding the cabinet structure must be determined based on the functional requirements of the switching equipment, while also taking into account the manufacturing conditions. The level of manufacturing expertise has a direct impact on the structural design of the cabinet and the choice of materials used. This post was last edited by 771207 on 2008-2-18 20:17.]