List of performance tests and inspection standards required for cement paper bag machines before they leave the factory

In the cement packaging industry, the performance and stability of cement paper bag machines directly affect the packaging efficiency and production costs of cement production lines . As an automated device integrating mechanical transmission, pneumatic control, and photoelectric detection, cement paper bag machines must undergo a series of rigorous performance tests and inspections before leaving the factory.

Only through these multi-dimensional tests can we ensure that the equipment maintains high precision and low failure rate even when operating under high loads for extended periods at the customer's site. Below is a list and detailed explanation of the various performance tests and inspection standards that must be performed on the cement paper bag machine before it leaves the factory.

I. Static Assembly and Visual Inspection: The Cornerstone of Precision

Before the equipment is powered on and put into operation, the assembly quality of the mechanical body must first be inspected according to strict standards. Although this step does not involve dynamic performance, it is the foundation for all subsequent tests.

1. Machine Body Levelness and Parallelism Verification:
Cement paper bag machines typically have a long machine body structure used to complete processes such as folding, bottom pasting, and valve affixing from roll paper to finished bags. Inspectors must use a precision level and laser calibrator to check the levelness of the main frame and each drive roller. Standards usually require that the longitudinal levelness not exceed 0.05mm/m , and the transverse parallelism must also be controlled within a very small error range. If the machine body is twisted, it will cause paper misalignment, bag bottom misalignment, and even inaccurate color registration during printing.

2. Dynamic Balance Inspection of Drive Rollers and Drums:
Rotating components of a paper bag machine, such as the traction rollers and embossing rollers, can generate significant centrifugal force and cause equipment vibration even with slight mass eccentricity during high-speed operation. Before leaving the factory, key rollers undergo dynamic balance testing . Depending on the rotational speed, the balance grade is typically required to reach G6.3 or higher. Only through dynamic balancing correction can the equipment operate smoothly at its designed maximum speed (e.g., 200-250 m/min), preventing premature bearing wear.

3. Pneumatic System Sealing Test:
Modern cement paper bag machines rely heavily on pneumatic components to complete complex folding and sealing operations. During testing, the entire pneumatic system must be pressurized to its rated pressure (typically 0.6-0.8 MPa) and held for a certain period (e.g., 30 minutes), observing the pressure drop on the pressure gauge. The stringent standard requirement is that the system pressure drop should approach zero when the air supply is cut off . Any minute leak not only wastes energy but also causes sluggish cylinder movement, affecting bag sealing accuracy.

II. No-load test run: testing the break-in process of the assembly.

After passing the static inspection, the equipment will enter the no-load test run phase. This test aims to observe the coordination of the various moving mechanisms of the equipment when there is no load (paper).

1. The bearing and transmission component temperature rise monitoring
equipment should run continuously under no-load for 4-8 hours. During this period, an infrared thermometer or thermocouple should be used to monitor the temperature of each major bearing housing and gearbox. Standards stipulate that the bearing temperature should not exceed the ambient temperature +40℃, and the maximum temperature should not exceed 75℃ . Localized high temperatures indicate insufficient assembly clearance, poor lubrication, or a quality problem with the bearing.

2. Noise and Vibration Testing:
Operational stability is a direct indicator of equipment manufacturing precision. Measured at a distance of 1 meter from the equipment, the no-load operating noise should generally not exceed 85 decibels (A) . Simultaneously, vibration velocity and amplitude at key points should be measured using a vibration tester. If periodic abnormal noises or severe vibrations are detected, it often indicates uneven gear meshing clearance or improper transmission chain tension, requiring immediate shutdown and troubleshooting.

III. Bag Making Precision Testing: Assessment of Core Processes

After the no-load operation is normal, the machine enters the material-carrying debugging stage. This is the core step of the cement paper bag machine's factory inspection, which directly determines whether the equipment can produce qualified cement bags.

1. Bag Length Cutting Accuracy Test:
The length of the cement bag directly affects the amount of cement dispensed during subsequent filling. The equipment must produce continuously at a set speed using servo traction or mechanical gear transmission. Inspectors will randomly select 50-100 finished bags from continuous production and measure their actual length. A high-standard factory requirement is that the bag length error be controlled within ±1.0mm . If the accuracy exceeds this standard, incomplete filling or dust leakage is very likely to occur during cement filling.

2. Valve Position and Folding Accuracy
: The valve position of the bag must be accurate; otherwise, misalignment or even failure to insert the bag may occur during packaging machine insertion. Before leaving the factory, the symmetry and folding depth of the valve opening must be visually inspected or manually sampled . For glued bottom bags, the glue application position and fold depth at the four bottom corners must also be checked one by one to ensure smooth opening during use.

3. Paper Web Tension Stability Test:
Cement paper bags typically use multi-layered stretchable paper. Improper tension control can lead to paper stretching deformation or breakage. Observe the fluctuation of the tension display instrument value during acceleration, deceleration, and constant speed processes. A qualified tension control system should be able to control the fluctuation range within ±5% of the set value , ensuring that the paper is transported flat without wrinkles or creases.

IV. Adhesive and Sealing System Inspection: Related to Bag Strength

The sealing strength of cement bags is a key indicator of their quality. The sealing system must undergo specific testing before leaving the factory.

1. Adhesive Application Uniformity Test:
Whether using cold or hot melt adhesive, the amount of adhesive applied must be precisely controlled. Too little adhesive will result in weak bonding and cement bag bursting during filling; too much adhesive will waste adhesive and contaminate the equipment. During testing, run the equipment at normal speed and place white test paper under the adhesive roller. Judge the uniformity of adhesive application by the width and continuity of the adhesive line . A high-precision system should ensure that the adhesive line is free of breaks and accumulation.

2. Adhesive strength tensile test:
Simulating a real-world usage scenario, the bottom of the pasted cement bag is cut into standard strips, and a tensile testing machine is used to perform a peel test. Standard requirements: Under specified temperature and humidity conditions, the peel force at the adhesive joint should reach a certain value (usually determined by the paper weight), and the failure mode should be tearing of the paper fibers, not adhesive separation . If the adhesive separates, it indicates a problem with the adhesive formulation or application process.

V. Electrical Control and Safety Protection Inspection

As automation levels increase, the complexity of control systems and safety standards for cement paper bag machines are also rising.

1. Safety Interlock Device Testing:
Modern equipment designs must comply with CE or national standards. Inspectors will test each safety door switch, emergency stop button, and light curtain protection device. When an emergency stop is triggered or the protective cover is opened, the main drive motor of the equipment should be de-energized and braked within a very short time (e.g., within 0.5 seconds) , and all dangerous actions must stop immediately. Simultaneously, the control system should record fault codes for troubleshooting.

2. Servo Drive and Synchronization Control Accuracy:
For multi-motor servo-driven paper bag machines, the synchronization between axes is crucial. Electronic virtual spindle technology is used to ensure speed synchronization of printing, traction, and cross-cutting units. Before leaving the factory, the following error of each axis must be monitored using an oscilloscope or driver software. The number of error pulses must be controlled within an extremely small range ; otherwise, misalignment of printed patterns or inaccurate cutting positions may occur.

3. Automatic paper breakage and material shortage detection
simulates paper breakage or glue depletion during production to test the sensor's response sensitivity. When the photoelectric sensor detects a paper breakage, the equipment should automatically stop within a set number of bags to prevent the generation of a large number of waste products . The low glue level alarm function must also be sensitive and reliable.

VI. Continuous Load Operation and Reliability Testing (“Stress Test”)

This is the final checkpoint before the product leaves the factory, and also the most challenging part.

1. The 48-hour continuous operation test
requires the equipment to operate continuously for more than 48 hours at the customer's commonly used production speed (e.g., 80%-90% of maximum speed). During this period, no downtime is allowed except for necessary raw material replenishment. The test standard is: the equipment's mean time between failures (MTBF) should reach the specified duration . Normal operational adjustments are permitted during this period, but downtime due to design flaws is not allowed.

2. Finished Product Rate Statistics:
During continuous operation, the ratio of the number of finished bags produced to the total number of bags produced is calculated. Industry standards for high-quality equipment typically require a finished product rate of over 98% upon delivery . The remaining 2% of defective products may be due to special stages such as paper splicing or machine acceleration; the defect rate should approach zero during steady-state production.

VII. Final Confirmation Before Packaging and Shipment

After the performance test is completed, the equipment enters the disassembly, protection and shipping stage, but the inspection is not over.

1. Oiling and Rust Prevention Inspection
: Inspectors must confirm that all exposed metal surfaces (such as guide rails and roller surfaces) are coated with rust-preventive oil and that desiccants are placed inside electrical cabinets. For marine equipment, there are higher standards for rust-preventive coating thickness and waterproof packaging.

2. Verification of Random Attachments and Documents
: The final step is to verify the random list, including specialized tools, spare parts (such as easily damaged rubber rollers and belts), and crucial inspection reports and certificates of conformity. In particular, the dynamic balancing report, the list of major bearing models, and the electrical schematic diagram are essential documents for future maintenance by the customer.

The factory inspection of cement paper bag machines is far more than a simple "power-on test"; it's a comprehensive system engineering project encompassing mechanical precision, electrical response, process effectiveness, and safety protection . Each machine should be accompanied by a detailed "Factory Inspection Report," recording the measured data for all the aforementioned key indicators. For users, checking each item against this checklist during equipment delivery and acceptance is essential to ensuring a return on investment and guaranteeing efficient future production. Only paper bag machines that pass this series of rigorous tests can operate reliably under the harsh dust environment and continuous operational pressure of cement plants.