How to conduct "trial production" and "process parameter optimization" for a cement paper bag machine? Standard process introduction.

In the cement packaging industry, the stable operation of paper bag machines directly affects production efficiency and product quality. Whether it's after the installation and commissioning of new equipment, or after a major overhaul or a long period of downtime, "trial production" and "process parameter optimization" are essential and crucial steps. Many companies are often impatient for quick results at this stage, rushing things and resulting in a series of problems after production begins—poor sealing, poor opening, paper wrinkles, low output, etc. These problems, when traced back to their root causes, are mostly related to inadequate work during the trial production phase.

Today, we'll systematically discuss how to conduct trial production and optimize process parameters for cement paper bag machines, and what the standard procedure is.

Why is it important to focus on the trial production stage?

Trial production is not simply "turning the machine on for a couple of runs and taking a look". Its core purpose is to fully verify the collaborative working ability of each system of the equipment before formal production, identify potential problems, and adjust all process parameters to the optimal state.

Cement paper bag machines typically consist of multiple functional units—paper roll holder, printing unit, tube making unit, bottom gluing unit, conveying and stacking unit, etc.—each unit is interconnected. An improper parameter setting can trigger a chain reaction. For example, poor paper tension control can lead to inaccurate printing registration and unstable tube length; improper control of the glue amount for bottom gluing can cause glue separation or overflow problems.

The value of the trial production phase lies in the fact that it allows for a relatively low-cost time investment in exchange for a high return on long-term stable operation.

II. Preparatory work before trial production

Before pressing the start button, the following preparations must be completed:

1. Equipment inspection and confirmation

First, check the installation of each mechanical component against the equipment manual and installation records. Key points include:

• Are the bolts in each transmission part tightened?
• Have the lubrication points been filled with grease or lubricating oil as required?
• Is the air system clean? Does the air pressure reach the set value (usually required to be 0.6-0.8 MPa)?
• Are the electrical wirings correct? Are the signals from each sensor being fed back normally?
• Are the safety protection devices installed in place?

This step may seem trivial, but in practice, many abnormal shutdowns that occur during trial production are caused by the failure to do these basic tasks properly.

2. Raw material preparation

Prepare the necessary materials for trial production, including paper rolls, inner liner paper, kraft paper backing, and adhesives. It is important to note that during the trial production phase, use the same raw material specifications and brands as in the full-scale production; otherwise, subsequent parameter adjustments may not be relevant.

Cement packaging paper bags are typically made of stretchable paper or all-pulp paper. The basis weight, moisture content, and transverse ring crush strength of the paper all affect the bag-making effect. It is recommended to test the key indicators of the incoming paper in advance and keep records.

3. Preparation of tooling and fixtures

Prepare the necessary measuring tools, including:

• Use a steel ruler or tape measure to measure the length and bottom width of the bag.
• Vernier calipers (for measuring paper thickness and adhesive layer thickness)
• Stopwatch (for measuring the production cycle time of a single bag)
• Thermometer and hygrometer (for monitoring workshop environment)
• Tensile testing machine (if available, for testing the strength of the paste base).

4. Personnel Preparation

Clearly define the roles and responsibilities of personnel involved in trial production. This typically includes equipment operators, maintenance electricians, mechanical repair workers, process technicians, and team leaders. Everyone must understand their duties during the trial production process.

III. No-load test run – Verification of mechanical transmission and electrical systems

Before inserting the paper, a no-load test run is performed. The purpose of this step is to verify the coordination of the various moving parts of the equipment and the stability of the electrical control system.

No-load test runs are typically divided into three speed phases:

• Run at low speed (approximately 30% of the design speed) for 15-20 minutes, observing whether each unit operates smoothly and without any abnormal noises.
• Run at medium speed (approximately 60% of the design speed) for 30 minutes, then check if the temperature rise of each transmission component is normal. The bearing temperature should generally not exceed 40°C above the ambient temperature.
• Run the machine at high speed (80%-90% of the design speed) for 15 minutes, observe the overall vibration, and confirm that there is no abnormal vibration or noise.

During no-load operation, the following points should be paid special attention to:

• Check whether each servo motor is running smoothly, and whether there are any vibrations or overload alarms.
• Whether the pneumatic actuator moves sensitively and accurately, and whether the cylinder moves without jamming.
• The accuracy of photoelectric sensor detection, especially for key sensors used in bag length detection and color mark detection, is crucial.
• Are the emergency stop button and safety door switch functions properly?

After the no-load test run is completed, check whether all fasteners are loose and whether there is enough lubricating oil seeping from each lubrication point. Only after confirming that there are no abnormalities can the load test production stage begin.

IV. Load Trial Production – Gradually Establishing Process Parameters

The trial production phase is the most critical stage in the entire process. It is recommended to proceed step by step, following the principle of "first individual machine debugging, then online linkage".

Step 1: Threading the paper and setting the tension

Following the paper feeding path specified by the equipment, feed the paper sequentially through each guide roller, printing unit, and tube forming unit. Pay attention to the orientation of the paper during feeding, ensuring the printing side faces outwards (if printing is required).

Tension setting is fundamental to bag production quality. Insufficient tension will cause the paper to run unsteadily, easily resulting in deviation and wrinkles; excessive tension will cause the paper to stretch and deform, affecting the bag length accuracy, and in severe cases, even breaking the paper.

The initial tension value can be referenced from the recommended value in the equipment manual, generally based on the premise that the paper does not exhibit significant shaking and the edges are flat during normal operation. During actual debugging, a "gradual method" can be used—starting with a lower tension and gradually increasing it, observing the paper's movement to find the optimal tension point.

Step 2: Printing unit debugging (if printing is required)

For cement paper bags that require printed labels, the printing unit should be tested before bag making. The main adjustments are as follows:

• The gap between the printing roller and the impression roller ensures uniform printing pressure.
• Adjust the ink volume to avoid excessive ink causing smudging or insufficient ink causing unclear text.
• Alignment of the color mark sensor ensures accurate identification of printed marks during subsequent bag making and cutting.

After the printing quality is confirmed to be up to standard, subsequent bag-making and debugging will be carried out.

Step 3: Tube-making unit debugging

The core of the tube-making unit is the control of the bag length and the stability of the center seam overlap.

Bag length adjustment is typically accomplished through a servo motor control system. First, a theoretical bag length value is set (e.g., a standard cement bag length of 640mm). Then, the equipment is run, and the actual length of 10-20 semi-finished bags is continuously measured using a steel ruler. The average and range are calculated. If the actual length deviates from the set value by more than ±2mm, correction is needed by adjusting the electronic gear ratio of the servo system or the clamping force of the traction roller.

The center seam overlap refers to the overlap width at the seam of the paper bag tube, which is usually required to be controlled between 8-12mm, and the glue line at the seam should be uniform and continuous. Two main points should be considered during adjustment: the guide angle of the forming plate and the uniformity of the glue application device.

Step 4: Debugging the base unit

Sealing the bottom is the most problematic step in cement paper bag production. A strong seal directly affects whether the bag will crack from the bottom after cement is filled.

The debugging of the paste base unit involves the following key points:

Positioning of the bottom sticker : The bottom sticker must accurately cover the predetermined position on the bottom of the bag, with a lateral offset not exceeding 1.5mm. This is achieved by adjusting the position of the stop gauge and pressure roller of the bottom sticker feeding device.

Glue application control : Too little glue will result in poor adhesion, while too much glue will cause glue overflow, affecting the appearance of the finished product and even causing paper jams by sticking to the conveyor belt. Glue application is usually adjusted by regulating the gap of the glue rollers or the pressure of the scraper. An empirical method of judgment is: when tearing the glued area of ​​the finished product after gluing, the paper fibers should be frayed, rather than the glue layer itself detaching.

Pressing pressure and time : Sufficient pressure and holding time are required when pressing the bottom sticker to the bag tube. The pressure is generally adjusted by a spring or cylinder, and the goal is to achieve no obvious air bubbles and uniform spread of the adhesive line after pressing.

Heating temperature (if using hot melt adhesive): When using hot melt adhesive, the temperature of the glue tank and the glue gun needs to be precisely controlled. If the temperature is too low, the adhesive will have poor flowability and uneven coating; if the temperature is too high, the adhesive will easily age and fail. Different types of hot melt adhesives have different temperature requirements, generally between 150-180℃, and the technical parameters provided by the adhesive supplier shall prevail.

Step 5: Gradual Speed ​​Increase and Integrated Debugging

Once all units can operate stably at low speeds, the operating speed of the equipment can be gradually increased.

During the speed increase process, it is recommended to increase the speed in increments of 20-30 bags per minute. After each speed increase, run the machine stably for 10-15 minutes and observe the following indicators:

• Is the bag length dimension stable? (As speed increases, changes in paper inertia may cause bag length drift.)
• Does the paste quality remain good?
• Is the equipment operating current within the rated range?
• Are there any new abnormal noises or vibrations caused by the increase in speed?

If a quality anomaly occurs at a certain speed, the speed should be reduced and reversed first. The cause should be analyzed and adjustments made before increasing the speed again. The ultimate goal is to achieve stable operation within 85%-95% of the design speed, leaving a certain speed margin to cope with fluctuations in raw material prices.

V. Recording and Curing of Process Parameters

During trial production, every effective parameter adjustment should be recorded. It is recommended to establish a "Process Parameter Record Sheet" to record the following details:

• Production date, trial production batch
• Paper specifications (brand, basis weight, width)
• Adhesive type and mixing ratio
• Tension setting values ​​for each unit
• Operating parameters of each servo motor
• Bag length set value and actual measurement value
• Parameters for controlling the amount of adhesive applied to the base coat (gap between applicators, pressure of the scraper, etc.)
• Pressing pressure value
• Heating temperature (if applicable)
• Equipment operating speed
• Ambient temperature and humidity

These parameters are crucial for subsequent formal production. When production conditions change (such as changing paper batches or seasonal variations in ambient temperature and humidity), these basic parameters can be used for targeted fine-tuning to quickly restore stable production.

VI. Inspection and Verification after Trial Production

Finished products produced during the trial production phase cannot be used directly for filling and require comprehensive quality inspection. Inspection items typically include:

Visual inspection :

• The bag surface is flat, without wrinkles or damage.
• Clear printing and accurate registration
• The glue is applied evenly, with no peeling or excess glue.
• The center seams overlap neatly, and the glue lines are even.

Dimensional inspection :

• The bag length, bag width, and bottom width meet the standard requirements.
• Bag length tolerance controlled within ±2mm
• The positional deviation of the bottom sticker should not exceed 1.5mm.

Physical performance testing (if conditions permit):

• Paste peel strength test
• Center seam overlap peel strength test
• Paper bag compressive strength test

Only when the batch inspection pass rate consistently reaches 98% or higher can the conditions for transitioning to formal production be met.

VII. Common Problems and Solutions

During trial production, some typical problems are often encountered. Here are a few categories and corresponding solutions:

Problem 1: Possible causes of unstable bag length
: tension fluctuations, insufficient clamping force of the traction roller, improper servo system parameters, and unstable detection by the photoelectric sensor.
Solution: First, check if the tension fluctuates with speed changes; then, check for wear or adhesive residue on the surface of the traction roller; finally, check if the sensor signal is stable.

Question 2: Possible causes of adhesive failure on the backing
: insufficient adhesive, insufficient pressing pressure, insufficient pressing time, oil stains on the paper or backing paper surface, or adhesive failure.
Solution: Check each item systematically, starting with the amount of adhesive, then gradually checking the pressure, time, cleanliness of the raw materials, and the adhesive's expiration date.

Question 3: Possible causes of paper misalignment
: non-parallel guide rollers, uneven tension, misaligned forming plate, and uneven end faces of the paper roll itself.
Solution: Use a level to check the parallelism of each guide roller and a tension meter to check if the tension on both sides of the paper is consistent.

Question 4: Severe adhesive overflow.
Possible causes: excessive adhesive application, insufficient gap between the glue roller and paper, or excessively low adhesive viscosity.
Solution: Readjust the glue roller gap and check if the adhesive viscosity meets requirements.

VIII. Summary

The trial production and process parameter optimization of cement paper bag machines is essentially a process of "slow and meticulous work." It tests not the operator's ability to run the equipment fast, but their ability to identify, analyze, and solve problems.

A complete trial production process, from preparation to no-load operation, from low-speed load to high-speed linkage, from parameter adjustment to quality verification, requires sufficient patience and meticulousness at every stage. Only by doing a solid job in the trial production phase can subsequent formal production avoid detours and malfunctions.

Finally, it's important to emphasize that process parameters are not static. Factors such as changes in paper batches, seasonal variations in temperature and humidity, and equipment wear and tear can all impact bag quality. Therefore, parameters established during trial production should only serve as a baseline template and require flexible adjustments based on specific circumstances in actual production. Establishing a comprehensive process parameter management mechanism and cultivating parameter awareness among operators are fundamental to ensuring the long-term stable operation of cement paper bag machines.