Cloth bags as necessities of life, is a set of materials science, mechanical engineering, aesthetic design as one of the craft manufacturing. Whether simple rucksacks or sophisticated leather handbags, they are made with a complete chain from the processing of the raw material to the inspection of the finished product. This paper will focus on the general process flow of bag duster and analyze the key stage of bag duster production.
Material Selection and Pre-treatment: Laying the Foundation for Quality
The performance and appearance of the bag is 70% dependent on the material selection. The materials commonly used in modern cloth bags are natural leather, synthetic leather (such as PU, PVC), fabric (nylon, canvas), composites, etc. In the case of synthetic leather case, the manufacturing process is as follows:
Preparation of basic materials
Synthetic leather usually consists of a base surface (such as knitted or non-woven fabric) and a surface coating (polyurethane or PVC). The bottom layer provides tensile strength, while the coating determines the feel and appearance.
Pre-treatment includes dust removal removal, electrostatic and humidity control to ensure that the material does not deform or stick together easily during processing. For example, electricity elimination reduce the surface charge of a material to a safe range to prevent bias during printing or cutting.
Lamination Process: To improve waterproofing or insulation, add functional film (e.g. aluminum foil or TPU film) between the substrate and coating. The laminating machine adopts the technique of hot pressing or bonding, which binds multiple layers of material tightly together to form a composite leather with uniform thickness.
Key Parameter Control: temperature (120-180°C), pressure (0.5-2MPa), velocity (5-30 m/min) need to be dynamically adjusted according to material characteristics.
ii. Precision Machining: from flat to three-dimensional: after material is prepared, it needs to be processed into a bag by cutting, printing, molding and so on.
Intelligent Cutting System: Traditional manual cutting has been replaced by laser cutting or CNC die-cutting. The accuracy of laser cutting ± 0.1mm, especially for complex patterns (such as hollowed patterns).
CNC die cutting adopts high-pressure cylinder driven blade to cut speed hundreds of times per minute, and equipped with a vacuum adsorption table to prevent material displacement. Cutting edges must be ground to prevent burrs from scratching the hand.
High-Precision Printing Technology: Screen printing or digital printing is used for surface decoration. Screen printing is suitable for mass production, using 200-300 mesh screen to evenly transfer ink to the surface of the material, achieve gradient and
metal texture and other special effects.
Digital printing supports small-batch customization, allowing design files to be fed directly into the printer without the need for a copy, but at a higher cost. After printing, UV curing or hot air drying is required to ensure strong adhesion of the ink.
3D Molding Process: Heat the flat material to its softening point (usually 100-150°C) and pressed it into a 3D shape (such as the curved bottom of the bag) using a mould. This process requires strict control of temperature and time to avoid excessive deformation or cracking of the material.
Sewing and Assembly: For components that need to be connected (such as bags and handles), use a high-speed flatbed panel sewing machines or a high head sewing machines. Thread tension, stitch length (usually 3-5 stitches/cm) and stitch density must be up to standard to ensure a strong and beautiful seam.
Edge treatment: Sewn edges can be folded, bound or glued to improve durability and mask rough edges. For example, leather bags are usually oiled with edges and involve multiple polishing and coloring processes to achieve a smooth, mirror-like finish.
III. Functional Enhancement and Detail Optimization: enhancing User Experience.
The practicality of the bag is often reflected in its detailed design. The following processes can greatly improve its performance:
Waterproofing: water repellent coating (e.g., fluorocarbon resin) or plasma treatment to alter the material's surface structure to create a lotus leaf effect to prevent water droplets infiltration.
Seams are sealed with hot melt strips or high frequency welding technology to prevent rainwater from seeping into the needle holes.
Load-Bearing Reinforcement: Metal rings or plastic buckles are embedded in load-bearing areas, such as handles and shoulder straps, with double-slit or X-shaped cross stitches for structural stability.
The bottom can be reinforced with a hard liner (such as a PP board) or abrasive pad to prevent the bag from buckling under heavy loads.
Hardware Installation: Zipper, magnetic clamp, D-ring and other accessories require to use professional equipment for precision installation. For example, the zipper pull must be engaged tightly with the zipper teeth to open and close smoothly and continuously, and the magnetic snap's adhesion must be tested to ensure it closes safely and opens easily.
