The primary materials and auxiliary substances used in sofa manufacturing encompass support materials, springs, padding, nails, ropes, base belts and fabrics, adhesives, and metal hardware connectors. Modern sofas have innovated from traditional ones by partially substituting solid wood frame structures with artificial panels, reducing or eliminating springs, and adopting new materials such as sponge.

 

The frame structure of modern sofas has evolved from solid wood to a combination of solid wood and artificial panels. The materials and auxiliary substances for crafting sofa frames mainly include support materials, support accessories, and decorative materials.

 

Sofa Frame Support Materials

Wood, bamboo, metal, and plastic can all serve as structural materials for sofas. The selection of frame materials requires sufficient rigidity and appropriate toughness.

 

1. Use of Wood

Sofas predominantly utilize wood for their frames, facilitating the secure attachment of base belts, springs, taut ropes, base cloth, and upholstery, thereby providing adequate strength to withstand the dynamic and impact loads of normal use without damage. The stability of the wooden frame effectively shares the load with the sofa legs.

 

The majority of sofa wood frames are concealed within leather, fabric, and sponge. Typically, wood with lower density (often coniferous) such as pine, fir, birch, and other suitable materials with straight grain, fine texture, minimal shrinkage, and resistance to deformation, appropriate strength, and shock absorption, as well as good mechanical processability and nail-holding capacity, are used.

 

Wood must be free from living insects or termites; otherwise, pest control treatment should be conducted to enhance the quality of the support structure. Some sofa manufacturers also opt for wood legs, which, when exposed, are more vulnerable to moisture and termite hazards.

 

2. Use of Plywood

Plywood material dimensions are generally 1220mm × 2440mm, with thickness specifications such as 3, 9, 12, 15, 18, 25mm, etc. The 3mm thickness is primarily used to encase the exterior of the wood frame, providing a reference surface and shaping surface for subsequent sponge attachment; thicknesses like 9, 12, 18mm are typically used for internal structural components of the sofa wood frame.

 

Plywood is constructed by cross-layering multiple 1~2mm thick wood veneers, thereby exhibiting balanced and stable characteristics overall.

 

Plywood compensates for the shortcomings of wood, and its structural features indicate that the grain direction has been considered. The cross-layering technique results in an "isotropic" effect, meaning the plywood is mechanically balanced, has strong shape stability, and is less likely to warp, twist, or crack along the grain.

 

The balanced and stable nature of plywood makes it highly suitable for processing irregularly shaped parts (such as L-shaped seatback internal frame parts). Moreover, plywood is easy to process, has a high material yield, and good nail-holding capacity. Plywood is popular in the internal frame of upholstered furniture, working alongside lumber to shape the sofa product frame, ensuring strength and stable dimensions.

 

Sofa Frame Support Accessories Materials

The support accessory materials in the sofa frame mainly include springs, straps, plastic nets, cotton felt, bolts, nails, adhesives, etc.

 

1. Springs

Common springs used in upholstered furniture sofa products include cylindrical spiral springs, bow springs, and semi-conical spiral springs.

 

Bow springs are often used in seat and back frames to support the sponge and human load. Common wire specifications include diameters of φ3.0, φ3.5, φ4.0mm, etc., with the bow width being approximately 50mm.

 

Spiral springs are primarily used inside the sponge seat cushion. Wire specifications have diameters ranging from 1.0 to 2.5mm, and heights from 80 to 200mm. The conical spiral spring seat frame is a spring assembly that can be directly nailed to the sofa's wooden frame.

 

2. Straps

Straps, also known as webbing, are often used in conjunction with bow springs in sofa seat and back frames to support the sponge and bear the human load. Straps commonly come in width specifications of 75mm and 50mm, with the 75mm specification bearing more force, mainly used in seat frames, and the 50mm used for back frames with less force.

 

The elongation rate of the strap is between 40% to 140%, selectable according to different rebound requirements. When tightened onto the wooden frame, it should be appropriately stretched (the stretch amount is about 1/3 of the connection length), then nailed tightly.

 

3. Plastic Nets, Cotton Felt

Plastic nets and cotton felt are both placed above the bow spring-webbing elastic surface to isolate the elastic surface from the sponge material, preventing the sponge from being compressed into the bow spring, which could cause cracking and reduce service life. The functions of plastic nets and cotton felt are the same, and they are generally not used at the same time.

 

4. Bolts, Nails, Adhesives

Since the sofa's internal frame is essentially hidden within the internal, there is no need to mortise the lumber. Connections between lumber and between lumber and plywood are primarily the simplest nail connections; exposed parts of the lumber connections are tenon joints, bolt connections, etc.

 

The nails mainly used for making sofa internal frames include straight nails, U-nails, round nails, wood screws, foam nails, etc. Sometimes, internal frame parts need to be tightened with bolts to ensure connection strength; the ropes used include wax webbing, fine yarn, and embedded ropes; the adhesives mainly include modified white latex glue, etc.

 

Sofa Frame Decorative Materials

The parts exposed outside the sofa leather, leather, and fabric surfaces are usually armrests, sofa feet, and functional parts (such as small glass, metal surfaces, convenient for placing tea sets, etc.), and for overall aesthetic effects, the material styles of these parts are diverse.

 

These materials are either integrated with the sofa frame (such as armrests, sofa feet, etc.), serving both structural connection and decorative functions; or have strong independence, serving only decorative purposes or as functional parts.

 

1. Wood

Decorative wood is usually dense, with beautiful grain and good quality, to enhance ornamental appeal, such as mahogany, willow, camphor wood, plum wood, teak, oak, eucalyptus, fir, and other woods. Commonly used for sofa frames, sofa legs, and armrests.

 

2. Metal

Metal materials are widely used on sofas. Metal materials have high strength, strong plasticity, and can be bent and shaped at will. Metal tubes, sheets, profiles, and other materials can be used to create different shapes, and colorful surface decorative effects can be obtained through electroplating and spraying processes.

 

Electroplating materials include gold, chromium, etc., and stainless steel, mirror stainless steel, and other materials can be made into frosted, brushed, and laser-engraved effects. Metal is essential in the overall material of the sofa, whether it is the sofa frame, sofa legs, or metal accessories.

 

3. Plastic

Plastic is a polymer material with strong plasticity, heat insulation, and insulation characteristics. With avant-garde design concepts, combined with plastic processing technology, pouring, molding, and other processing can create sofa prefabricated accessories with both appearance and function.

 

The surface of plastic parts should be smooth, free of cracks, wrinkles, stains, and obvious color differences. Specially treated acrylic has characteristics such as scratch resistance, smooth and soft feel, and the surface is not easy to soil, stain, water stains, or fingerprints.