When it comes to bottle making molds, the first thing people think of is the initial mold, the mold, the mouth mold and the bottom mold. Although the blowing head is also a member of the mold family, because of its small size and low cost, it is a junior of the mold family and has not attracted people’s attention. Although the blowing head is small, its function cannot be underestimated. It has a famous function. Now let’s talk about it:
How many breaths are there in one blower?
As the name implies, the function of the blowing head is to blow compressed air into the initial blank to make it inflate and form, but in order to cooperate with the thermobottle forming blowing head, several strands of air are blown in and out, see Figure 1.
Glass bottle drawing
Let’s take a look at what kind of air is in the blowing method:
1. Final Blow: Blow up the initial mold base to make it close to the four walls and bottom of the mold, and finally make the thermo bottle shape;
2. Exhaust out of the mold: Exhaust air from the inside of the hot bottle to the outside through the gap between the bottle mouth and the blowing pipe, and then through the exhaust plate to continuously discharge the heat in the hot bottle to the outside of the machine to achieve The cooling in the thermos forms the internal cooling gas (Internal Cooling) of the thermos, and this exhaust cooling is particularly important in the blowing & blowing method;
3. It is directly connected to the mouth of the bottle from the positive blowing part. This air is to protect the mouth of the bottle from deformation. It is called Equalizing Air in the industry;
4. The end face of the blowing head generally has a small groove or a small hole, which is used to discharge the gas (Vent) at the bottle mouth;
5. Driven by the positive blowing force, the inflated blank is close to the mold. At this time, the gas in the space between the blank and the mold is squeezed and passes through the mold’s own exhaust hole or vacuum ejector. outside (Mold Vented) to prevent the gas from creating an air cushion in this space and slow down the forming speed.
The following is a few notes on the important intake and exhaust.
2. Optimization of positive blowing:
People often ask to increase the speed and efficiency of the machine, and the simple answer is: just increase the pressure of positive blowing and it can be solved.
But it is not the case. If we are blowing air with high pressure from the beginning, because the initial mold blank is not in contact with the mold wall at this time, and the bottom of the mold does not hold the blank. The blank produces a large impact force, which will cause damage to the blank. Therefore, when the positive blowing starts, it should be blown in with low air pressure first, so that the initial mold blank is blown up and close to the wall and bottom of the mold. gas, forming a circulating exhaust cooling in the thermos. The optimization process is as follows: .
1 At the beginning of the positive blowing, the positive blowing blows up the blank and then sticks to the wall of the mold. Low air pressure (eg 1.2kg/cm²) should be used at this stage, which accounts for about 30% of the positive blowing time period allocation,
2. In the latter stage, the internal cooling period of the thermos is carried out. The positive blowing air can use high air pressure (such as 2.6kg/cm²), and the distribution in the time period is about 70%. While blowing high pressure into the thermos air, while venting to the outside of the machine to cool down.
This two-stage optimization procedure of positive blowing not only ensures the formation of the thermobottle by blowing up the initial blank, but also quickly discharges the heat of the thermobottle in the mold to the outside of the machine.
Three Theoretical Basis for Strengthening the Exhaust of Thermal Bottles
Some people will ask to increase the speed, as long as the cooling air can be increased?
In fact, it is not. We know that after the initial mold blank is placed into the mold, its inner surface temperature is still as high as about 1160 °C [1], which is almost the same as the gob temperature. Therefore, in order to increase the speed of the machine, in addition to increasing the cooling air, it is also necessary to discharge the heat inside the thermos, which is one of the keys to preventing the deformation of the thermos and increasing the speed of the machine.
According to the investigation and research of the original Emhart company, the heat dissipation at the molding place is as follows: the mold heat dissipation accounts for 42% (Transferred to mold), the bottom heat dissipation accounts for 16% (Bottom Plate), the positive blowing heat dissipation accounts for 22% (During Final Blow), convection The heat dissipation accounts for 13% (convective), and the internal cooling heat dissipation accounts for 7% (Internal Cooling) [2].
Although the internal cooling and heat dissipation of the positive blowing air only accounts for 7%, the difficulty lies in the cooling of the temperature in the thermos. The use of an internal cooling cycle is the only method, and other cooling methods are difficult to replace. This cooling process is especially useful for high-speed and thick-bottomed bottles.
According to the original Emhart company’s research, if the heat discharged from the thermos can be increased by 130%, the potential for increasing the machine speed is more than 10% according to different bottle shapes. (Original: Test and simulations at the Emhart Glass Research Center (EGRC) have proven that the inner glass container heat extraction can be increased up to 130%. Depending on the type of glass container, considerable speed increase potential is confirmed. Various container demonstrate speed increase potential of more than 10%.) [2]. It can be seen how important the cooling in the thermos is!
How can I discharge more heat from the thermos?
The exhaust hole plate is designed for the bottle making machine operator to adjust the size of the exhaust gas. It is a circular plate with 5-7 holes of different diameters drilled on it and fixed on the air blowing head bracket or air head with screws. The user can reasonably adjust the size of the vent hole according to the size, shape and bottle making process of the product.
2 According to the above description, optimizing the cooling time period (Internal Cooling) during positive blowing can increase the pressure of compressed air and improve the speed and effect of exhaust cooling.
3 Try to extend the positive blowing time on the electronic timing,
4 During the blowing process, the air is rotated to improve its ability or use “cold air” to blow, etc. Those skilled in this field are constantly exploring new technologies.
be careful:
In the pressing & blowing method, since the punch is directly punched into the glass liquid, the punch has a strong cooling effect, and the temperature of the inner wall of the thermos has been greatly reduced, about below 900 °C [1]. In this case, It is not a problem of cooling and heat dissipation, but to maintain the temperature in the thermos, so special attention should be paid to different treatment methods for different bottle-making processes.
4. Overall height of control bottle
Seeing this topic, some people will ask that the height of the glass bottle is the die + the mold, which seems to have little to do with the blowing head. In fact, it is not the case. The bottle maker has experienced it: when the blowing head blows air during the middle and night shifts, the red thermos will move upward under the action of compressed air, and the distance of this moving changes the glass bottle. the height of. At this time, the formula for the height of the glass bottle should be changed to: Mould + Molding + Distance from the hot bottle. The total height of the glass bottle is strictly guaranteed by the depth tolerance of the end face of the blowing head. The height may exceed the standard.
There are two points to draw attention to in the production process:
1. The blowing head is worn by the hot bottle. When the mold is repaired, it is often seen that there is a circle of bottle mouth-shaped marks on the inner end face of the mold. If the mark is too deep, it will affect the overall height of the bottle (the bottle will be too long), see Figure 3 left. Be careful to control tolerances when repairing. Another company pads a ring (Stopper Ring) inside it, which uses metal or non-metallic materials, and is regularly replaced to ensure the height of the glass bottle.
The blowing head repeatedly moves up and down at high frequency to press on the mold, and the end face of the blowing head is worn for a long time, which will also indirectly affect the height of the bottle. Service life, ensure the total height of the glass bottle.
5. Relationship between blowing head action and related timing
Electronic timing has been widely used in modern bottle making machines, and the air head and positive blowing have a series of correlations with some actions:
1 Final Blow On
The opening time of positive blowing should be determined according to the size and shape of the glass bottle. The opening of positive blowing is 5-10° later than that of blowing head.
The blowing head has a little bottle stabilization effect
On some old bottle making machines, the pneumatic cushioning effect of mold opening and closing is not good, and the hot bottle will shake left and right when the mold is opened. We can cut off the air under the air head when the mold is opened, but the air on the air head has not been turned on. At this time, the air head still stays on the mold, and when the mold is opened, it produces a little dragging friction with the air head. force, which can play the role of assisting the mold opening and buffering. The timing is: the air head is about 10° later than the mold opening.
Seven setting of blowing head height
When we set the gas head level, the general operation is:
1 After the mold is closed, it is impossible for the air head to sink when the air blowing head bracket is tapped. The poor fit often causes a gap between the air head and the mold.
2 When the mold is opened, hitting the blowing head bracket will cause the blowing head to drop too deep, causing the blowing head mechanism and the mold to be stressed. As a result, the mechanism will accelerate wear or cause mold damage. On the gob bottle making machine, it is recommended to use special set-up blowheads (Set-up Blowheads), which are shorter than the normal air head (Run Blowheads), about zero to minus zero.8 mm. The setting of the air head height should be considered according to the comprehensive factors such as the size, shape and forming method of the product.
Advantages of using a set gas head:
1 Quick setup saves time,
2 The setting of the mechanical method, which is consistent and standard,
3 Uniform settings reduce defects,
4 It can reduce the damage to the bottle-making mechanism and mold.
Note that when using the gas head for setting, there should be obvious signs, such as obvious paint or engraved with eye-catching numbers, etc., so as to avoid confusion with the normal gas head and cause losses after mistakenly installed on the bottle making machine.
8. Calibration before the blowing head is put on the machine
The blowing head includes positive blowing (Final Blow), cooling cycle exhaust (Exhaust Air), blowing head end face exhaust (Vent) and equalizing air (Equalizing Air) during the positive blowing process. The structure is very complex and important, and it is difficult to observe it with the naked eye. Therefore, it is recommended that after the new blower or repair, it is best to test it with special equipment to check whether the intake and exhaust pipes of each channel are smooth, so as to ensure that the effect reaches the maximum value. General foreign companies have special equipment to verify. We can also make a suitable gas head calibration device according to local conditions, which is mainly practical. If colleagues are interested in this, they can refer to a patent [4]: METHOD AND APPARATUS FOR TESTING DUAL-STAGE BLOWHEAD on the Internet.
9 Potential related defects of the gas head
Defects due to poor setting of positive blow and blow head:
1 Blow Out Finish
Manifestation: The mouth of the bottle bulges out (bulges), the cause: the balance air of the blowing head is blocked or does not work.
2 Crizzled Sealing Surface
Appearance: Shallow cracks on the top edge of the bottle mouth, cause: The inner end face of the blowing head is severely worn, and the hot bottle moves upwards when blowing, and it is caused by impact.
3 Bent Neck
Performance: The neck of the bottle is inclined and not straight. The cause is that the air blowing head is not smooth to exhaust the heat and the heat is not completely discharged, and the hot bottle is soft and deformed after being clamped out.
4 Blow Pipe mark
Symptoms: There are scratches on the inner wall of the bottle neck. Reason: Before blowing, the blowing pipe touches the blowing pipe mark formed on the inner wall of the bottle.
5 Not Blown Up Body
Symptoms: Insufficient forming of the bottle body. Causes: Insufficient air pressure or too short time for positive blowing, blockage of exhaust or improper adjustment of exhaust holes of exhaust plate.
6 Not Blown Up Shoulder
Performance: The glass bottle is not fully formed, resulting in deformation of the bottle shoulder. Reasons: insufficient cooling in the hot bottle, blockage of the exhaust or improper adjustment of the exhaust hole of the exhaust plate, and the soft shoulder of the hot bottle sags.
7 Unqualified verticality (bottle crooked) (LEANER)
Performance: The deviation between the center line of the bottle mouth and the vertical line of the bottom of the bottle, the cause: the cooling inside the hot bottle is not enough, causing the hot bottle to be too soft, and the hot bottle is tilted to one side, causing it to deviate from the center and deform.
The above is just my personal opinion, please correct me.
Post time: Sep-28-2022