Plastic Blow Molding
Plastic blow molding first extrudes the plastic into a billet, passes compressed air to make it tightly adhere to the inner wall, and after cooling and demolding, it can become a seamless high-quality hollow part, which is used in the production of various bottles and containers.
Blow Mold Suppliers | Equipment Usage & Maintenance
Blow mold suppliers not only provide mold manufacturing services but also provide equipment maintenance to ensure the efficiency and normal production of theblow molding process. Before delivering the mold to the customer, the blow mold suppliers also need to perform a series of operations such as trial molding to ensure that the mold can produce high-quality products. At this point, manufacturers need to be proficient in using blow molding machines.
The main process of the plastic blow molding is to extrude or inject thermoplastic materials into tubular billets, heat and soften them, put them into the mold, close the mold and inject compressed air, blow and expand the plastic to tightly adhere to the inner wall, solidify it through the exhaust and cooling system, and demold to form hollow products.
Precautions for Using Blow Molding Equipment
Before the suppliers put the blow mold into use, it is necessary to have a certain understanding of the operation process and precautions of the blow molding machine, such as:
- Inspection and Preparation Before Startup
Before starting the mold, employees need to be familiar with and able to strictly operate according to the requirements of the blow molding equipment manual; It is necessary to check whether the electrical wiring and the foot bolts of the mold are loose and whether they meet the requirements for use; Check whether the insulation of components such as electric motors and heaters meets the requirements for start-up; Add sufficient lubricating oil or grease to each lubrication point as required; Check if the feeding and cooling systems are operating properly; The plastic raw materials used for blow molding production should be dried to meet the required drying requirements. If the plastic has a high water absorption rate, secondary drying is necessary; The specifications of the machine head need to be selected based on the variety and size of the product. The main process of installing the machine head is to install the machine head flange, mold body, mouth mold, porous plate, and filter screen; Check if the compressed air pipe is properly connected, install the head heating ring and core mold electric heating rod; Check the water system and flow channels; Ensure that the gaps in all parts of the mold are uniform and aligned with the centerline of the main and auxiliary machines; Start the locking device, extruder, robotic arm and other operating equipment to operate without load, ensuring the normal operation of various safety emergency devices, and promptly eliminate any faults found; Reasonably set the temperature of the extruder head and each heating section, and preheat them in advance. After the temperature of each section reaches the set temperature, maintain a constant temperature for 0.5-1 hour; On the programmable controller, set the thickness of the blank wall at each point according to the process specifications.
- Air Freight Transfer
The equipment operator needs to check whether the parameter values at each location are consistent with the process requirements; After starting the heating system, check the current indication values of each section of the heater promptly. When the extruder and billet head reach the temperature set by the process, perform two to three hours of insulation; Start the lubrication and cooling system, and start the main motor at low speed. After idling for three to five minutes, stop the machine. After the idling step is completed, check the screw for abnormalities and the motor ammeter for overload, and the pressure gauge for normal operation (the machine should not idle for too long) promptly.
- Steps for Booting up
Start the feeding, cooling, and lubrication system, set the speed control knob of the main motor to zero, then start the main motor at low speed, and gradually increase the speed uniformly and slowly. Usually, rotate at a speed of 10-20r/min for a few minutes until the molten material starts to be extruded from the machine head, and then continue to increase the speed of the main motor until it reaches the specified normal operating speed; At the beginning, gradually add a small amount of material. When the billet can be extruded normally and the values displayed by each control device meet the process requirements, gradually increase the extruder speed to the required speed. Before plastic extrusion, no one is allowed to be in front of the mouth mold; Subsequently, a large amount of plastic can be added to adjust the thickness of the billet; After the extrusion of the billet reaches a stable and uniform state, the mold closing operation can begin and finally enter normal production. To ensure normal production and good product quality, manufacturers should adjust process parameters promptly during the molding process, control the temperature, speed, and pressure on the melt of the extruder, and control the wall thickness and quality of the billet; While ensuring normal production and operation, the extrusion speed of the billet can be accelerated to accelerate the production cycle, ultimately reducing the weight sag of the billet; Ensure sufficient inflation pressure and fast blowing rate; Manufacturers also need to check whether the exhaust of the billet is sufficient; On the premise of ensuring that the product can be fully cooled, try to reduce the cooling time as much as possible and shorten the molding cycle.
- Inspection during Operation
During the operation of the equipment, check whether the current of the main motor remains stable. If the current fluctuates significantly, adjust it promptly, and if necessary, stop the machine for operation; Pay attention to whether there are any abnormal noises in the various components inside the equipment (especially the rotating parts). If there are any, the main consideration is whether there is wear or poor meshing of the gears, whether there are foreign objects mixed in the plastic, or whether the bearings are damaged. There may be abnormal noises during operation; It is necessary to check whether the heating and cooling, lubrication, and billet control systems are working properly. Check if the discharge is consistently stable and uniform.
- Shutdown
When performing a shutdown operation, the feeding system and the feeding gate of the hopper should be closed first, and then the speed of the main motor should be reduced. The material in the barrel should also be drained as much as possible. Wait until the materials are discharged, lower the speed control button of the main motor until it reaches zero, and turn off the power of the equipment and its heaters, cooling pumps, and lubrication hydraulic pumps. Finally, turn off the main power supply and all inlet valves.
Regular Maintenance of Blow Molding Equipment
Blow mold suppliers need to regularly inspect and maintain blow molding equipment. Normal maintenance and upkeep are conducted once a year, usually involving operators and professional maintenance personnel. The main contents of maintenance include:
- Regularly check the wear degree of the barrel and screw. For minor scratches and wear, use an oilstone or fine sandcloth for grinding until the surface is flat and smooth, and record the measured dimensions of the barrel and screw working surface.
- Regularly inspect the position of the electric heating device, cooling fan, and safety cover. If there is any deviation, adjust it promptly to ensure that they can continue to work normally and efficiently.
- Timely clean and scrub the oil and dust on various parts of the blow molding machine. Be careful not to use rough tools for cleaning to avoid wear and tear.
- Regularly inspect various pipelines (water, gas, and lubricating oil) to ensure they are unobstructed, and repair any leaking areas.
- Check the wear of various rotating parts, polish those with less wear, and map gears with more severe wear to prepare for the next maintenance and replacement.
- Test each safety alarm device to ensure its normal operation and reduce the risk of accidents.
- Disassemble the gearbox and bearing cover, and check the quality of the lubricating oil to ensure that it has not been severely contaminated. If the quality of the lubricating oil has affected normal use, it is necessary to clean and replace it promptly.
- Use a mercury thermometer to measure the heating temperature of the barrel and compare it with the temperature value displayed on the instrument to ensure the correct operation of the extrusion process temperature.
Common Equipment Malfunctions
When repairing blow molding mold, suppliers usually need to first analyze the faults that occur to obtain corresponding solutions. Common faults include:
When Starting, the Main Motor Stops
When this situation occurs, the blow mold suppliers should consider whether the power supply of the main motor is not connected; Is the main motor power supply wiring poorly connected or not connected; Whether the motor is overloaded; And check if each heater is operating properly.
Extruder Shutdown
Poor melt fluidity leads to overloaded operation of the extruder; Replace the plastic with a less viscous resin, or increase the heating temperature to accelerate melting; Check if the filter orifice plate of the machine head is blocked and clean it promptly; Heating time is too short or a certain section of the heater malfunctions, resulting in excessive torque and motor overload; Check the temperature of each section and determine the preheating and heating time. Check the heating ring and replace it promptly.
Rupture at the Head Connection
The extruder was forcibly turned on and did not reach the preheating temperature, which requires the blow mold suppliers to strictly follow the process operating procedures; The blockage of the machine head and impurities on the mesh board need to be cleaned promptly; The heating temperature of the machine head can be appropriately increased; Explosion-proof devices can be installed on blow molding equipment.
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