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PET Bottle Blow Molding Machine 101: The Ultimate Guide Serial 1

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Blow Molder 101: The Ultimate Guide Serial 1

Blow Molding Machine 101 series includes answers to all the questions you may or may not know about blow molding machine production, operation, and maintenance.
This is the serial 1.

01.

What is a blow molding machine

definition

Simply put, it is a machine, specifically a machine for producing hollow containers. Generally, there are two types:

Pneumatic blow molding machine and hydraulic blow molding machine,

Pneumatic generally produces less than 10L, while hydraulic pressure is generally more than 10L because of its high energy consumption.

In a broad sense, blow molding machines include blow molding machines, blow molding machines, injection blowing machines, and the more commonly used two-step blow molding machines!

What is a blow molding machine

The majority of blow molding machines are still two-step processes, which means that the plastic raw materials must first be molded into preforms before being blown. PET polymers, which are environmentally friendly, are increasingly widely used.

What is the purpose of a blow molding machine? The machine’s wind pushes the plastic body into a certain shape of the mold cavity once the liquid plastic is sprayed out, resulting in a finished product. This sort of machine is known as a blow molding machine. A hydraulic blow molding machine, which is a type of blow molding machine, is also included.

02.

What is the blow molding process

The hot (or softened) tubular plastic parison formed by extrusion or injection molding of thermoplastic resin is put in a split mold, and compressed air is fed into the parison soon after the mold is closed to blow the plastic parison. It swells and adheres tightly to the inner wall of the mold, resulting in a variety of hollow objects after cooling and demoulding.

03.

History of the blow molding process

During World War II, the blow molding technology was first employed to make low density polyethylene vials. Blow molding technique became widely employed in the late 1950s, with the introduction of high-density polyethylene and the creation of blow molding equipment. Hollow containers may hold hundreds of liters of liquid, and some manufacturers use computer control. Polyethylene, polyvinyl chloride, polypropylene, polyester, and other plastics are ideal for blow molding, and the hollow containers produced are frequently utilized as industrial packing containers.​​

04.

What are the factors that affect the production of bottles by the blow molding machine?

The influencing factors in the process are: preform and its heating, pre-blow (position, pressure and flow), stretch rod, high pressure blow (pressure, position), and mold, etc.

1 perform

 PET pellets are used to make the preform, also known as the parison. It stipulates that the percentage of recycled materials must not exceed 10%, and the number of recyclables must not exceed two. Preforms used after injection molding or after heating must be chilled for at least 48 hours before being utilized, and they should not be stored for more than 6 months. Different manufacture dates cannot be blended, especially preforms with significant gaps. The key cause behind this is The type of raw materials used in the preform, the quantity of secondary materials mixed in, and the residual stress in the preform are all different, and all of these aspects have an influence on the bottle molding process and should be addressed.

2 heating

The heating furnace, which is manually set and automatically adjusted, completes the heating of the preform. The height of the heating furnace should be around 25mm, and the distance between it and the conveying wheel should be around 19.6mm. The preform is heated more uniformly and can be formed better by running continually through the oven on the conveying wheel, which solves the drawback of uneven heating due to static heating and manual rotation of the preform. However, if the heating furnace is not correctly set, it will result in an uneven distribution of the blown bottle wall thickness (such as the upper and lower weight), the bottle mouth becoming bigger than the norm, the hard neck, and other issues.

The heating temperature of the preform is generally set at 85-120 ° C, the colorless preform is higher, and the colored preform is lower. If the temperature is set too high or too low, it will cause product defects, such as tearing, white fog, etc.The temperature of each section may be modified depending on the product’s molding state, and the aperture of the oven light tube should also be considered. Furthermore, the oven’s output power setting has a significant impact on the heating of the preform, which affects the heat output of the whole oven. When the machine is turned on for the first time after a lengthy period of time, the initial output power should be set higher, and then progressively lowered over the usual production process. When the ambient temperature is below 5 degrees Celsius, the output power is typically about 80%. The impact is more noticeable.

The bottle blowing manufacturing process has a link with the temperature of the production environment. The ambient temperature is usually around 22 degrees Celsius. The product is susceptible to condensation point agglomeration if the temperature is too high; if the temperature is too low, the product performance is unstable when the machine is started, and the particular operation should be adjusted according to the real circumstances and experience.

3 blows before blowing

Pre-blowing is a step in the blowing process that helps the preform assume shape while also stretching it longitudinally using the stretching rod to improve its longitudinal strength. During the blowing process, the pre-blowing cam pushes the three-way valve to the pre-blowing position, and the one-way valve completes the operation. The quality of the bottle is affected by the pre-blow position, pressure, and flow.

If the pre-blowing position is correct, the bottom of the bottle’s center point will be skewed and thinned, the foot’s wall thickness will be uneven and white, the top will be heavy and the bottom will be light, the neck will be hard, and even the bottom will penetrate, among other defects; if the pre-blowing position is incorrect, defects such as upper light and lower weight, thickening of the center point, and depression will appear.

Flow of air A one-way valve controls the pre-blowing air flow, and it’s best to open it three to four turns. The air flow is strong, the bottom is heavy, the central point is narrow and biased, the feet are white, and the thickness of the walls is uneven;

Pressure The pre-blowing pressure should be between 0.8 and 1 MPa. When the pressure is high, the top becomes heavy and the bottom becomes light, the center point becomes skewed, the wall thickness of the foot becomes uneven, the foot becomes white, and so on; when the pressure is low, the bottom becomes heavy and the center point becomes thick.

The molding of the bottle foot and center point has a great influence on the quality of the bottle. Improper adjustment often leads to fatal defects such as bottle burst (under normal experimental conditions) and leakage.

4 stretch rods

The stretching rod is a mechanism that extends the heated preform while pre-blowing and then resets after high-pressure blowing and before exhaustion. During the blowing process, the stretching rod must be able to move vertically and smoothly, the driving pressure is 0.55-0.8MPa, and the gap with the bottom mold is 2.3-2.5mm, indicating that the preform thickness is 1/3-1/2. The center point on the bottom of the bottle will be displaced if the gap is too big; if the distance is too narrow, the center point will grow thinner.

5 high pressure blow

The purpose of high-pressure blowing is to fully stretch the molten material and adhere to the mold wall, resulting in a fully formed bottle that is also stretched laterally to increase lateral strength. Location and pressure are the two most important determining elements.

Depending on the characteristics of the mold and the properties of the filled beverage, the high-pressure blowing pressure is normally between 3.7 and 4 MPa (carbon dioxide). The position of high-pressure gas and the position of exhaust are the two options. The pressure holding time in the molding process is the period between the two, and the duration of this time has a significant impact on the bottle capacity stability. Inadequate high-pressure air might easily result in incorrect bottle molding and foot blowing.

6 molds

Mold is one of the most significant influences on bottle blow molding. The bottle body is made with a Huff mold, while the bottom is made with a separate blow molding mold. The mold should be kept at a steady temperature, clean, and the vent holes should not be clogged during the manufacturing process.

When the mold’s heating and cooling system fails, flaws such as crooked bottle necks, tilted bottles, volume and height changes, and a heavy bottom result; keeping a consistent temperature in the mold can help avoid condensation on the mold surface.

PET shrinkage after molding is quite high, averaging 1.8 percent, and it is partially decreased when glass fiber reinforcement is added, although it still ranges between 0.2 and 1.0 percent. The high mold temperature shrinkage rate is substantial under typical conditions, whereas the low mold temperature shrinkage rate is minimal. The mold temperature must be tightly regulated in order to preserve the PET bottle volume stability. The temperature of the bottle body is slightly greater, at 20-45°C, while the bottom temperature requirement is lower, at 6-15°C. The bottom will be heavier and the central point will be thicker if the bottom temperature is high.

In actual production, there are nozzles, etc., which will affect the molding of PET bottles.

05.

What is the production process of the blow molding machine?

1. Preheating

The preform (preform) is irradiated by an infrared high-temperature lamp, and the body part of the preform (preform) is heated and softened. In order to maintain the shape of the bottle mouth, the preform (preform) mouth does not need to be heated, so a certain amount of heat is required. cooling device to cool it.

2. Blow molding

In this stage, the preheated preform (preform) is placed in the blow mold that has already been prepared, high-pressure inflation is carried out in it, and the preform (preform) is blown and drawn into the desired bottle.

Blow molding machines on the market are generally divided into two types: automatic and semi-automatic.

The automatic bottle blowing machine completes the two blowing operations together through the operation of the manipulator, eliminating the process of manually placing the preheated preform (embryo) into the blow mold in the middle. Greatly accelerated the rate of production, of course, the price is higher than the semi-automatic.

06.

What is the daily operation procedure of the blow molding machine

  1. Lubricating oil must be applied to each moving element of the fully automated blow molding machine before each shift. (manipulator, manipulator guide rail, opening and closing guide rail for mold)
  2. The swing arm may be added once a day (3-4 times), and the heating machine’s large and tiny chains can be added once a month. Check for oil leaks in the main engine reducer and heating machine reducer on a regular basis, and replace the main engine bearing every 2 to 3 months.
  3. Check if the moving components are firm, whether the screws are loose or coming off, especially in regions with high impact force, and whether the belt transmission portion is anomalous before going into production.
  4. Verify that the high-pressure air supply, low-pressure air supply, power supply, and water supply are all operational.
  5. Make that the emergency stop switch, safety door switch, and protection device detection switch are all in good working order.
  6. Verify that the heating head enters the embryo and that the embryo-dropping mechanism functions properly. The nut of the pushing device can be changed if the embryo is not in position.
  7. Examine the light tube for any damage or breakage. To be replaced in due course.
  8. Inspect each pneumatic component for leaks and make sure the action is responsive.
  9. Make sure the triplet isn’t leaking abnormally, that it’s not obstructed, and that the water cup’s water storage capacity isn’t excessively full. 10. The solenoid valve of the blowing machine should be cleaned as soon as possible if it is malfunctioning (every 3.5 million blows are cleaned).
  10. It is necessary to clean and polish the blowing mold on a regular basis.
  11. Slowly open the high and low pressure air source switches to avoid the air source blowing too rapidly and causing dirt to enter the solenoid valve. Open the exhaust valve for 30 seconds at the same time to guarantee that the air is pure.
  12. When starting the machine, make sure that the mechanical parts are in good condition, there is no one inside the machine, and there is no foreign matter. Especially the crank position, so as not to hurt people. Also close the safety door.
  13. When starting the machine, the motor must be started first, and the heating machine should be started after a delay of 30 seconds to prevent voltage fluctuations. Make sure the cooling water is turned on before starting the heating.
  14. After the heating starts (2-3) minutes, wait for the oven temperature to rise evenly, and then press the embryo button. At the same time, the blowing bottle should be turned on when it is powered on, otherwise it will not blow the bottle.
  15. When the machine is running, it is necessary to pay close attention to whether the machine has abnormal noise. It is necessary to detect it early and stop it in time to solve it.
  16. In case of emergency, press the emergency stop button to brake in an emergency. Then analyze the cause of the formation according to the on-site situation, and find the problem and solve it quickly.
  17. To avoid the manipulator from injuring individuals, do not place any part of your body into the machine after it has run properly. After slowing down, you can hear if the machine makes any unusual noises.
  18. Once the machine is in regular production, the operator must constantly monitor the bottle’s quality to minimize voltage fluctuations or other factors impacting the blowing bottle’s quality.
  19. To guarantee a safe repair, push the touch screen fault repair button while the machine is being fixed. Pay attention to the position of the robot if you need to manually examine the movement of each cavity individually. Simultaneously, verify that you grasp the function of each particular button before moving it to avoid causing needless difficulties.
  20. After each maintenance of the machine, be sure to clean up tools and screws, so as not to leave them in the machine and affect the normal operation of the machine. The company mainly produces automatic blow molding machines

07.

How to adjust the quality of the bottles produced by the blow molding machine?

 

  1. The bottle body is milky white, indicating that the temperature of the light box is too high. Adjust the temperature of the corresponding lamp tube according to the whitening position.
  2. The bottle body is blue and stretched white, indicating that the temperature of the light box is low. Adjust the temperature of the corresponding lamp tube according to the whitening position.
  3. Aggregate at the bottle mouth, increase the temperature of the first layer of lamp tube, or close the cooling water outlet valve of the small bottle mouth.
  4. The deformation of the bottle mouth indicates that the temperature of the bottle mouth is too high, so reduce the temperature of the first layer.
  5. The belly button appears at the bottom of the bottle, and the pre-blowing delay is too high, so lower it in units of 0.01S
  6. The bottleneck becomes thicker, and the pre-blowing delay time is too short. Increase the pre-blowing delay in units of 0.01S. The company mainly produces automatic blow molding machines

08.

How to master the troubleshooting method of blow molding machine

  1. Various parameters to be recorded

Focus on recording various related parameters of the blowing machine after adjustment, such as the pressure parameters of the injection molding machine, the speed parameters of the blowing machine, the current, voltage, and speed of the blowing machine motor. Also note down the status of the relays, contactors, etc. in the electrical cabinet when they are energized and formally processed (on or off), as well as the status of all input and output LEDs of PC and PLC (bright, dark, flashing) or record the screen The upper PC and PLC status (input bit) and (output bit) are 0 or 1, which is very beneficial for future analysis and judgment of faults.

  1. To record the status of the hydraulic system

Also record the pressure of various pressure gauges in the hydraulic system during formal processing or non-processing, and the suction-off state of the solenoid valve, which is also very helpful for adjustment and judgment. The level of pressure directly affects whether the function of the blow molding machine is normal or not. It is important to record static and dynamic stress.

  1. Carry a notebook with you, and record the failures that occur every day and how to troubleshoot them one by one.

The human brain is easy to forget after a long time, “good memory is not as good as bad writing”, and it is very beneficial to record it. We found that some faults of the blow molding machine often occur repeatedly, and these faults always occur. Just check how they were solved at the time, and the fault can be eliminated in a few minutes, which is fast and good.  

09.

What are the bottle blowing machine manufacturing equipment on the market

At present, most of the two-step blow molding machines used in China are internationally advanced two-step blow molding machines made in Germany, France and other countries. 4-40 molds, some can reach more than 60, and the output per hour is about several thousand, and some can reach 20,000.

10.

What are the parts of the blow molding machine?

This type of equipment generally consists of five parts: blank supply system, heating system, main engine, control system and auxiliary machinery.

The most important one is the host, which is fully computer controlled, including the opening and closing of the host, the opening and closing of the oven lamp and the adjustment of the molding process

11.

What is the overall situation of the blow molding machine now?

As the price of crude oil has risen, the price of plastic raw materials has also risen, so container manufacturers are trying to reduce the weight of containers in order to save raw materials. Moreover, with the continuous awakening of environmental awareness, saving energy and reducing pollution has become an important indicator to measure the quality of products. In addition, the safety, quality, speed, cost, scope of application, and energy and raw material savings of the machine are all issues that bottle blowing machine manufacturers are devoted to.

In order to compete with China’s increasing quality of blow molding machines and win more domestic market share, some imported blow molding machine manufacturers are trying their best to reduce the price of the equipment. With the rising demand for high-quality products in the domestic market, imported machines with good performance will have better prospects.

Domestic blow molding machine manufacturers make great efforts to develop new technologies, improve quality, and strive for better prices and larger market shares with better machines.

In order to simplify the production process, the one-step bottle blowing machine integrates multiple processes of injection, drawing and blowing on one machine, saving a lot of energy and time. The one-step blow molding machine of Aokiku Research Institute is one of the outstanding representatives in this regard. The two-step rule is divided into two steps: preform production and stretch blow molding, which are completed on two independent machines. In the actual application process, the one-step method and the two-step method each have their own development space due to differences in product characteristics, environments and conditions.

Squeeze blow tends to be more economical and the molds are cheaper. When processing bottles with complex shapes, squeeze blowing should be used.

Speed ​​has become the focus of market competition. In response to this trend, Hong Kong Yaqi Group has developed a model with an hourly output of 6,000 pieces. Its blow molding machines can produce containers from 1 ml to 1000 liters.

Because PET material has the advantages of high transparency, good gloss, high strength, and stable chemical properties, its application in food, daily chemicals, etc. is becoming more and more extensive.

12.

What are the advantages of one-step blow molding machine: one-step blow molding saves time and money

The injection-stretch-blow molding machine provided by the Japan Research Institute (AOKI) takes its patented technology “Direct Heatcon” as its core technology, and realizes the production of high-quality plastics directly from raw materials by one machine. the purpose of the container. Its models are suitable for PET, PES, PC, PA, PP, HIPS, PEN and other materials. Packaging production.

The so-called “direct temperature adjustment method” refers to the use of the heat retained during the molding of the preform to directly extend and blow molding, thereby saving the energy consumption required for reheating, shortening the cooling time of the preform, and realizing the small size of the cold water equipment. configuration.

In addition, one-step bottle blowing has the following advantages:

  1. Directly use raw materials to produce containers, which saves the cost of material management and preform transportation, and reduces the risk of damage or contamination of preforms during transportation.
  2. Directly regulate the temperature distribution of the preform in the mold cavity, so that the preform has a very suitable temperature required for stretch blow molding, and the thickness is uniform. Generally speaking, reheating is easily affected by various factors (temperature and humidity, material state, etc.), and it is difficult to produce a uniform container. In order to prevent the occurrence of defective products, it is necessary to take a large safety margin – increase the thickness of the preform . This increases the weight of the container to a certain extent and wastes raw materials. AOKI’s preform forming technology thickens the parts that need to be extended and thins the parts that don’t need to be extended, so there is no need for safety margins and the product is lightweight.
  3. It only takes 4 seconds for the AOKI molding machine to take out the preform to extend-blow molding, and the rotating disc rotates 120 degrees. It saves many processes required by the two-step method, which helps to greatly reduce energy consumption.

AOKI series bottle blowing machines can also directly use the crushed-cleaned PET bottle recycle material for injection-stretch-blow molding, which does not require the use of traditional PET re-pelletizing and recycling systems, thus saving the cost of recrystallization . And the quality of the product is also very high.

A spokesman for AOKI pointed out that in recent years, the rise of PET bottles is due to the fact that it is lighter and safer than glass bottles, and does not have the unenvironmental and harmful characteristics of PVC bottles. In addition, its transparency allows consumers to clearly see the content. These advantages make PET bottles increasingly popular in many packaging applications.

Its spokesman also pointed out that the international crude oil prices rose sharply, so that the price of PET materials also rose. Packaging container manufacturers are therefore keen to reduce the weight of products of various sizes. Following this trend, a container with a volume of 1.5 liters and a weight of 16 grams, a container with a volume of 1 liter and a weight of 14 grams, and a container with a volume of 750 ml and a weight of 11 grams have been developed. These containers have membrane-thin walls and are easily crushed. Therefore, it is very environmentally friendly in terms of material saving and waste disposal.

AOKI Institute launched a soft and ultra-light container with lid called “Ugly Duckling” at Beverage Asia 2005. It saves half of the PET raw material than ordinary containers, and can be kneaded by hand after being discarded, reducing the volume of garbage. In any respect, it is an economical and environmentally friendly product.

The reason why it is called the “ugly duckling” is because it is easily crushed, cannot stand after filling, and there are a series of difficult problems in molding, filling, and listing. But it is developed in response to market demand, and has a lot of added value that is different from traditional bottles.

One of the benefits is that this model can produce containers with a large arc, which is easy to carry. The second is that its off-center bottle mouth and easy-to-pinch bottle make it easy to quickly pour even viscous liquids. Moreover, because air is not easily retained in the container, if the product is easily oxidized, it can be protected from deterioration during long-term use. In addition, the feel of its products is also very good, which can be described as soft and easy to handle.

The company’s spokesman also revealed that they attach great importance to the Chinese market and hope to serve more Chinese customers and bring good profits as China joins the WTO.

13.

What innovations does the blow molding machine have in terms of control?

Preform heating system: infrared heating controlled by thyristor, and each layer of infrared lamps can be independently controlled. The air flow in the heating area and the unique design of the bottleneck protection device enable the preform to obtain an ideal temperature curve, while the bottleneck is not affected by heating, supplemented by an infrared thermometer to achieve automatic temperature adjustment and intelligent heating control of the preform. The heating tube realizes individual regulation and control.

Operating system: human-machine dialogue operating system, which can directly reflect the production status. The heating temperature of the preform at all levels is displayed through the touch screen operation, and the control parameters can be adjusted according to the requirements of the fully automatic bottle blowing machine. Each mold can be easily controlled through the touch screen. Blowing parameters of the cavity.

Safety system: mechanical and electrical interlock protection of mold clamping to avoid damage to equipment when mold clamping is not smooth. Clamping mechanical electrical interlock protection ensures the safety of the mold and the mold base. The double limit detection of the bottom mold and the mold opening ensures that the bottom mold does not drop during the high-speed operation of the equipment. The sealing multi-point detection device greatly protects the safe operation of the manipulator and the stretching rod. Bottle picking detection ensures the safe operation of the blank feeding manipulator and the mold. The electronic inspection system accurately and automatically eliminates unformed bottles and defective preforms, preventing the risk of downtime. Heating lamp disconnection alarm detection

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