What are the machines for producing valve-mouth cement bags? ——Detailed explanation of key equipment in valve-mouth cement bag production lines

In the cement, building materials, and chemical industries, valve-mouth cement bags have become a popular choice for packaging powdered materials due to their ease of filling, excellent sealing, and stable stacking. The production process for valve-mouth cement bags requires high levels of precision, stability, and automation, and production lines typically utilize multiple specialized machines. This article systematically introduces the main machine types and functions required for valve-mouth cement bag production, providing a reference for those in the relevant industry.

1. Basic characteristics and production requirements of valve bags

Valve bags are packaging bags with a sealed bottom and a valve at the top. During filling, materials are added through the valve, eliminating the need for sewing. The valve automatically closes after filling. This structure requires a sturdy bag body, precisely positioned valves, and adequate pressure and moisture resistance for both the inner and outer layers. Therefore, machines producing valve bags must be capable of high-precision coating, cutting, valve fabrication, and multi-layer lamination.

2. Main machine types for producing valve-mouth cement bags

A complete valve bag production line usually includes the following equipment:

1. Valve bags made with printing presses
   typically require the outer surface to be printed with a company logo, product information, and instructions. These presses utilize flexographic or gravure printing methods, enabling high-speed, multi-color printing on woven fabric or kraft paper. Modern presses are equipped with automatic registration systems and tension control to ensure clear and accurate print placement.
2. Because cement
   is susceptible to moisture, valve bags often utilize an inner coating or laminating process to enhance moisture resistance. Coating machines use a hot-melt extrusion process to coat a base material (such as woven fabric) with a polyethylene (PE) or polypropylene (PP) film. The uniformity and adhesion of the coating directly impact the bag's moisture resistance and strength.
3. The valve bag body of the folding machine
   needs to be folded to increase the longitudinal tensile strength. The folding machine folds the substrate on both sides through the guide roller and folding mechanism, and uses high temperature setting to ensure that the folded edge is flat and firm.
4. This machine cuts
   continuous webs to set lengths, forming individual bags. A high-precision servo control system ensures a cutting length error of less than ±0.5mm, while also pre-folding and creasing the bag bottom.
5. The valve port forming machine
   is a core piece of equipment in valve bag production, responsible for forming the valve port structure on the top of the bag sheet. The valve port is typically composed of multiple layers of material, including a base fabric, film, and reinforcement sheet. The valve port forming machine completes the forming process through punching, patching, and hot pressing, ensuring consistent valve port dimensions and a good seal.
6. Bottom-sewing machines
   are used to seal the bottom of valve bags, either by sewing or gluing them together to hold the contents. Sewing machines use industrial sewing thread for overlocking, while gluing machines seal the bag using heat or adhesive. Depending on the bag type, single or double-thread sewing is available, and thread breakage detection is also available.
7. The bag body sewing machine
   sews the sides of the bag to form a tubular bag body. This equipment uses a high-speed sewing head and an automatic feeding device to complete continuous sewing and thread processing.
8. Fully automatic
   forming machines integrate multiple processes, including hemming, valve installation, bottom sewing, and bag body sewing, to achieve continuous production from roll stock to finished bags. Automated production lines typically include PLC control systems, visual inspection units, and robotic handling devices, significantly improving production efficiency and consistency.
9. Finished bags undergo pressure testing, valve patency testing, and leak detection. Automatic inspection machines use pneumatic and optical sensors to reject defective products, while packaging
   machines bundle and palletize bags according to the set quantity.

3. Selection considerations

The following factors should be considered when selecting valve bag production equipment:

• Production requirements : Select the machine model based on production capacity (such as monthly output) and bag specifications (size, number of layers, material).
• Degree of automation : Semi-automatic equipment is suitable for small-batch and multi-variety production, while fully automatic lines are suitable for large-scale standardized production.
• The quality of key components : such as servo motors, PLC controllers, heat sealing modules, etc. directly affects the equipment life and yield rate.
• Energy consumption and maintenance : Pay attention to the unit energy consumption and daily maintenance costs of the equipment, and give priority to models with modular design and easy maintenance.

4. Technology Development Trends

The current valve bag production equipment is developing towards intelligent and green directions:

• Integrated control : Real-time monitoring of equipment data and remote fault diagnosis are achieved through the Industrial Internet of Things (IIoT).
• Energy-saving design : Adopting variable frequency motor and heat recovery system to reduce energy consumption and carbon footprint.
• Flexible production : The equipment is adaptable to a variety of materials (such as woven fabrics, kraft paper, composite materials) and bag type switching to meet customized needs.

The machinery used to produce valve-mouth cement bags is a multi-step system encompassing printing, laminating, forming, and testing. Technological advancements have enabled modern equipment to not only improve production efficiency and product consistency, but also address energy conservation and intelligent manufacturing requirements. When selecting equipment, companies should consider their product positioning and production capacity planning, choosing reliable and technologically scalable production lines to adapt to increasingly competitive markets.