How to maintain the PUR hot melt adhesive machine to extend its lifespan and improve production efficiency?

Dongguan Saipu Electromechanical Device Co., Ltd. is a professional enterprise integrating R&D, manufacturing, marketing and after-service of hot melt glue spraying machinery. Since its establishment, we have been committed to meeting the diverse needs of the market by developing products with better performance, more complete functions and higher quality. We have built a professional team composed of experienced technical experts and senior managers, who rely on innovative technology and professional experience to promote the steady development of the company, and provide reliable hot melt glue spraying equipment and professional supporting services for various industries.

Detailed Maintenance Method for PUR Hot Melt Adhesive Machine (Saipu Professional Guidance)

1. Clean the glue gun nozzle and valve body: Use a special glue scraper or dust-free cloth to gently clean the solidified glue blocks remaining on the gun nozzle, so as to avoid wire drawing, dripping glue and glue breaking during production. It is strictly prohibited to scrape hard with a blade, so as not to scratch the sealing surface of the gun nozzle and cause glue leakage. Saipu reminds that the sealing performance of the gun nozzle is the key to ensuring stable glue output, and improper cleaning will directly affect the service life of the gun valve.

2. Check temperature and pressure parameters: Refer to the glue instruction manual and the equipment operation manual provided by Saipu, and check the three-section temperatures of the glue tank, glue pipe and gun body. The temperature fluctuation range shall not exceed ±5℃. At the same time, check the air source pressure, which is generally maintained at 0.4–0.6MPa. Unstable pressure will lead to uneven glue output, affecting the bonding quality of products. For the temperature setting, Saipu technical team suggests that it should be strictly based on the type of PUR glue, and it is not allowed to adjust the temperature at will.

3. Wipe the surface of the machine body and pipeline: Clean the dust, fibers, residual glue and oil stains on the surface of the machine body, glue pipe and electrical control box to prevent impurities from entering the heat dissipation port or bearing parts, which will lead to poor heat dissipation of the equipment and premature aging of components. For the electrical control box, special attention should be paid to keeping it dry and clean to avoid short circuit caused by dust accumulation.

4. Check air pipes, oil pipes and joints: Observe whether there is air leakage, glue seepage and hose cracking at the joints of air pipes, oil pipes and equipment. If the joint is loose, fasten it immediately to avoid pressure loss and glue waste. Saipu reminds that even slight air leakage will affect the glue output pressure, and long-term glue seepage will corrode the equipment surface and accelerate the damage of sealing parts.

5. Standard shutdown process: After the production is completed, stop glue output first, reduce the temperature of the gun nozzle by 20–30℃ and run for a few minutes, then turn off the heating, pump body, air source and main power supply in turn. It is strictly prohibited to cut off the power directly at high temperature. High-temperature direct shutdown will cause the glue in the pipeline to solidify rapidly, which will bring great trouble to the next startup and even damage the pipeline and gun valve.

（2）Weekly maintenance（Production interval execution, about 20–30 minutes）

Weekly maintenance is a key link to prevent equipment faults. It is necessary to carry out in-depth cleaning and inspection of key components to ensure the stable operation of the equipment for a long time. It is recommended to be operated by professional maintenance personnel or operators trained by Saipu.

1. Clean the floating glue and carbonized layer on the upper part of the glue tank: Open the glue tank cover, carefully remove the aging glue film on the surface of the glue liquid. The PUR glue is easy to turn yellow and brittle after repeated heating, and the carbonized glue will sink to the bottom of the tank and block the filter if not cleaned in time, affecting the glue supply efficiency. Saipu suggests that when cleaning, use a special tool to avoid scratching the inner wall of the glue tank.

2. Clean or replace the glue filter: Remove the glue inlet filter, soak and scrub it with anhydrous ethanol or special cleaning agent provided by Saipu. If the filter screen is seriously blocked, replace it directly. The blockage of the filter screen will cause slow glue output, insufficient pressure and reduced bonding strength, which will affect the production efficiency and product quality. Saipu recommends that the filter be replaced regularly according to the production intensity, generally once every 1–2 months.

3. Lubricate moving parts: Apply high-temperature grease to the moving parts such as cylinder piston rod, guide rail, slider and rotating shaft to reduce mechanical wear and abnormal noise, and extend the service life of moving parts. When lubricating, pay attention to the amount of grease, not too much or too little, and avoid grease entering the glue pipeline and polluting the glue liquid.

4. Check the heating tube and temperature sensing line: Check whether the heating line is damaged or exposed, and whether the temperature sensing probe is loose. Poor contact of the temperature sensing line will cause local overheating, burn the glue pipe and sealing parts, and even cause fire hazards. If any abnormality is found, stop the machine immediately for maintenance and replace the damaged parts in time.

5. Test the opening and closing sensitivity of the gun valve: Start the machine without glue, click to output glue, check whether the opening and closing of the gun valve is smooth, whether there is jamming or poor closing. If there is any abnormality, disassemble and inspect the gun valve in time to eliminate small faults and avoid serious damage to the gun valve.

（3）Monthly/Quarterly in-depth maintenance（Professional maintenance, about 1–2 hours）

Monthly/quarterly in-depth maintenance is a comprehensive inspection and maintenance of the equipment, which can effectively solve potential faults and extend the service life of the equipment. It is recommended to be operated by Saipu professional after-sales technicians or trained professional maintenance personnel.

1. Disassemble and clean the inside of the glue pump/gear pump: After emptying the residual glue in the glue tank and pipeline, disassemble the pump body, carefully remove the accumulated glue and solidified particles inside the pump body, and check the wear of the gears and bearings. The dirty blockage of the pump body will lead to large noise, unstable glue output and motor overload. If the gears are seriously worn, they should be replaced in time. Saipu reminds that the disassembly and assembly of the pump body must be carried out in accordance with the operation manual to avoid damage to the precision components.

2. Detect the heating system and calibrate the temperature: Use an independent thermometer to compare the temperature displayed by the equipment. If the deviation exceeds 10℃, it is necessary to recalibrate the temperature or replace the temperature sensing line. The decline of heating efficiency will prolong the glue melting time, reduce the production capacity, and even cause the glue to melt incompletely, affecting the bonding quality. Saipu after-sales team can provide professional temperature calibration services for customers.

3. Replace seals, O-rings and vulnerable glue pipes: Seals and O-rings are easy to harden, deform and lose elasticity under long-term high-temperature environment, which is the main cause of glue leakage. The inner wall of the glue pipe will age and shed residues after long-term use, which will block the gun nozzle. It is recommended to replace the seals, O-rings and vulnerable glue pipes as a whole regularly. Saipu provides original matching accessories to ensure the compatibility and stability of the equipment.

4. Comprehensively fasten the screws of the whole machine: The long-term vibration of the equipment will lead to the loosening of fixed screws, feet and brackets, which will cause equipment shaking, noise and displacement, and even affect the precision of glue spraying. It is necessary to fasten each point of the equipment one by one to ensure the stability of the equipment.

5. Clean the cooling fan and ventilation port: Clean the dust and flocs on the cooling fan and ventilation port of the electrical control box and motor to ensure the normal heat dissipation of the electrical control box and motor, prevent the circuit board from being burned due to high temperature, and avoid motor burnout caused by poor heat dissipation.

（4）Long-term shutdown maintenance（Shutdown ≥ 3 days）

1. Empty the residual glue in the glue tank and pipeline as much as possible: The PUR glue will cure irreversibly when it meets moisture. The residual glue will basically not melt when the machine is started next time, which is very easy to block the whole pipeline. When emptying the glue, it can be heated to the normal temperature, and the glue can be discharged completely by starting the pump body.

2. Seal the glue tank, glue pipe and gun nozzle: Use special plugs to seal all interfaces of the glue tank, glue pipe and gun nozzle to isolate air and moisture. If conditions permit, a small amount of dry nitrogen can be filled into the glue tank for protection, which can better prevent moisture from entering the system.

3. Power off, dust-proof and moisture-proof storage: Cover the equipment with a dust cover and place it in a dry and ventilated environment to avoid moisture in the humid workshop entering the interior of the equipment, which will corrode electrical components and pipeline parts.

4. Pre-treatment before restarting: Before restarting the machine, preheat and dry at low temperature for 30 minutes to eliminate the moisture inside the equipment, then gradually raise the temperature to the normal working temperature and test the machine. Avoid sudden heating, which will cause the glue liquid to boil and splash, and avoid damage to the equipment due to moisture.

Misunderstanding 1: The higher the temperature, the smoother the glue output and the stronger the bonding

• Wrong performance: In order to speed up the glue melting and improve the glue output efficiency, the operator arbitrarily increases the temperature of the glue tank, glue pipe and gun body by 20–50℃, thinking that higher temperature can make the glue output smoother and the bonding effect better.

• Hazards: PUR glue is easy to decompose, carbonize and turn yellow at high temperature, the viscosity drops sharply, and the bonding strength is greatly reduced, resulting in unqualified products; At the same time, high temperature will accelerate the aging of heating tubes, glue pipes and seals, shorten their service life, and even directly burn the gun valve and electrical components, leading to serious equipment faults.

• Correct practice: Strictly set the temperature according to the parameters recommended by the glue manufacturer and the equipment operation manual provided by Saipu. Generally, the temperature of the glue tank is 100–120℃, the temperature of the glue pipe is 110–130℃, and the temperature of the gun body is 110–130℃. If you have questions about the temperature setting, you can consult Saipu technical team at any time.

Misunderstanding 2: There is no need to clean the residual glue, and it can be melted and used continuously next time

• Wrong performance: The residual glue in the glue tank and pipeline is directly retained, and it is melted and used again when the machine is started next time, thinking that this can save glue and reduce costs.

• Hazards: PUR glue will age and cross-link after repeated heating, forming hard glue blocks, which will block the filter, pump body and gun nozzle, leading to intermittent glue output, uneven glue spraying, and even no glue output. In severe cases, the entire pipeline and pump body need to be replaced, and the maintenance cost is extremely high, which seriously affects the production progress.

• Correct practice: Clean the gun nozzle every shift, clean the residual glue on the surface of the glue tank every week, and empty the residual glue in the system when the machine is shut down for a long time. Saipu suggests that the residual glue that has been heated repeatedly should not be used again to avoid affecting the product quality and equipment performance.

Misunderstanding 3: Directly cut off the power when shutting down, without cooling and glue draining

• Wrong performance: After the production is completed, the operator directly cuts off the main power supply of the equipment, and the high-temperature glue liquid remains in the pipeline to cool naturally, saving shutdown time.

• Hazards: The high-temperature glue liquid will solidify completely in the glue pipe and gun valve, forming a "solid glue stick", which cannot be melted by ordinary heating. It can only be dredged by disassembling the machine or replacing the entire section of the glue pipe, which is time-consuming and laborious, and increases maintenance costs.

• Correct practice: Strictly follow the standard shutdown process: first stop glue output, reduce the temperature of the gun nozzle and run for a few minutes, then empty the residual glue in the pipeline, and finally turn off the heating, pump body, air source and main power supply in turn.

Misunderstanding 4: Use ordinary solvents such as gasoline and thinner to clean the PUR system

• Wrong performance: In order to save costs and convenience, operators use industrial solvents such as gasoline and thinner to soak and clean the pump body, gun nozzle and pipeline, thinking that these solvents can quickly remove the residual glue.

• Hazards: Ordinary solvents will corrode the PU material glue pipe and fluorine rubber seal ring, leading to cracking of the glue pipe, failure of the seal, and large-area glue leakage and air leakage. In severe cases, the entire glue supply system will be damaged, and the equipment cannot work normally.

• Correct practice: Use the special cleaning agent specified by the manufacturer or Saipu, or anhydrous ethanol, environment-friendly hot melt glue cleaning agent. When cleaning, follow the operation manual to avoid damage to the equipment.

Misunderstanding 5: As long as glue can be output, there is no need to replace the filter

• Wrong performance: When the filter is blocked and the glue output becomes slow, the operator still insists on production, thinking that as long as glue can be output, it will not affect the production, and replacing the filter will increase costs.

• Hazards: The blocked filter will increase the load of the pump body, leading to overload of the motor and even burnout of the motor; At the same time, the glue output pressure is unstable, which will cause glue shortage and false adhesion of products, resulting in batch scrapping of products and serious economic losses.

• Correct practice: Check the filter every week. If the glue output is obviously slow, the pressure is abnormal, or the filter screen is seriously blocked, clean or replace the filter immediately. Saipu recommends that the filter be replaced regularly according to the production intensity to ensure the smoothness of the glue supply system.

Misunderstanding 6: The maintenance of PUR glue machine is the same as that of ordinary EVA hot melt glue machine

• Wrong performance: Operators use the maintenance method of EVA hot melt glue machine to maintain PUR hot melt glue machine, ignoring the particularity of PUR glue.

• Hazards: EVA hot melt glue does not react with moisture, and its maintenance requirements are relatively simple, while PUR glue has a strong moisture curing reaction, which has higher requirements on sealing, moisture-proof and glue draining. Simple mixed use of maintenance methods will lead to frequent glue leakage, pipeline blockage and other faults of PUR hot melt glue machine, which will greatly shorten the service life of the equipment.

• Correct practice: Clarify the differences between PUR hot melt glue machine and EVA hot melt glue machine. PUR hot melt glue machine pays more attention to sealing and moisture-proof, timely glue draining and avoiding repeated heating. For specific maintenance differences, you can consult Saipu technical team to obtain professional guidance.

Misunderstanding 7: Slight glue leakage is irrelevant, and it can be used reluctantly

• Wrong performance: When there is a small amount of glue seepage at the gun nozzle and joint, the operator thinks that it does not affect the production and does not deal with it, thinking that it is a trivial matter and can be used reluctantly.

• Hazards: The leaked glue will continuously absorb dust and fibers in the air, form hard dirt, aggravate the wear of the sealing surface, and eventually develop into serious glue leakage. In severe cases, the glue will seep into the cylinder and circuit, causing serious faults of the whole machine, and even affecting the safety of operators.

• Correct practice: Once glue seepage is found, stop the machine immediately to check the sealing parts. If the seals are aged, deformed or damaged, replace them in time to avoid small faults developing into major ones.

Misunderstanding 8: No sealing protection is done when the machine is not used for a long time

• Wrong performance: When the equipment is idle, it is placed bare, and the interfaces of the glue tank, glue pipe and gun nozzle are not blocked, ignoring the impact of moisture and dust.

• Hazards: The moisture and dust in the workshop will enter the glue tank and pipeline, and the glue will react with moisture and solidify quickly when the machine is started next time, directly blocking the system. The maintenance of the blocked system is difficult and costly, and even the equipment cannot be restored to normal use.

• Correct practice: If the machine is shut down for more than 3 days, it is necessary to block all interfaces with special plugs, cover the dust cover, and place the equipment in a dry and ventilated environment to ensure that the interior of the equipment is free from moisture and dust.

Saipu After-sales Service Commitment

Dongguan Saipu Electromechanical Device Co., Ltd. has always adhered to the service objective of "Credibility First and Customer First". We not only provide high-quality PUR hot melt glue spraying equipment, but also provide professional after-sales service and technical support for customers. If you encounter any problems in the process of equipment maintenance and use, our professional after-sales team will provide you with timely and effective solutions. We will continue to improve our products and services, help customers maximize the value of equipment, and create a better future together with customers.