The bag making process of flexible packaging is called the "most complete" version in history!

1Introduction to process flow and procedure

1. Flexible packaging: collectively used to package goods with flexible materials. Packaged with plastic film or plastic film composite material is called plastic flexible packaging.

2. Process introduction

1) The plate making process is a process of manufacturing a printing plate that functions to transfer ink to a printing material during printing. The color of the original image is reproduced through the halftone dots made on the printing plate.

2) The printing process is the process of using the substrate, printing plate, ink, and printing machinery to achieve graphic reproduction. The graphics on the printing plate are transferred to the substrate.

According to the type of printing plate: gravure, flexographic, screen, letterpress, lithographic printing.

Most of China's flexible packaging is produced by the gravure printing process. During production, printing materials are discharged into the printing device through a unwinding device. The ink on the surface of the printing plate is scraped off by a scraper. After entering the oven, the solvent components in the ink evaporate in the heated and blown oven. After the printed film comes out of the oven, it passes through a cooling roller and is cooled and shaped. During multi-color printing, the computer's automatic overprinting device controls the overprinting between the colors. After printing is completed, the winding device takes up the printed product into a roll film.

3) The quality inspection process is the process of passing the printed semi-finished products through a quality inspection machine to detect and reject the printed unqualified products. Reduce the increase of post-process production loss and the difficulty of quality inspection.

4) The compounding process is to combine two or more materials together to form an integrated material. Composite materials can not only maintain the excellent characteristics of single-layer materials, but also overcome their respective shortcomings. After compounding, they have new characteristics to meet the different requirements of composite materials for food and other commodities.

Compound classification: dry compound method, wet compound method, extrusion compound method, solventless compound method, hot melt compound method, co-extrusion compound method.

Most of the flexible packaging is produced by the dry composite process. During production, the glued substrate is discharged into the glue coating device through the unwinding device, and the glue on the surface of the glue roller is scraped off by the scraper. When contact occurs when pressing, it is transferred to the surface of the gummed substrate, and then enters the oven, and the solvent component in the glue is volatilized in the heated and blown oven. After coming out of the oven, it is bonded together with the substrate released by another unwinding device in a heated and pressurized composite nip roller. After being cooled and shaped, it is taken up by a winding device into a rolled composite film.

5) The curing process is a process in which the main agent and the curing agent in the composite film complete the reaction. The newly-composited composite product cannot be processed in the next step because the adhesive layer is not solidified and set. Therefore, the curing agent must complete the reaction with the curing agent and the adhesive layer is set. The aging is divided into room temperature aging and heating aging. Normal temperature curing means that the composite film completes the reaction between the main agent and the curing agent under normal temperature conditions; heating and curing is that the composite film completes the reaction between the main agent and the curing agent at a specific temperature. Heating and ripening can speed up the reaction between the main agent and the curing agent, and shorten the production cycle.

6) Slitting is the process of cutting the composite film or printed film that does not need to be compounded to the required width. During production, the slitting material is discharged through the unwinding device, and the longitudinal travel position of the slitting material is controlled by the photoelectric control system, so that the cutter position of the slitted product is kept constant. The winding device rolls the slit product into a roll film. Some of the slit roll film is used as the finished product for the customer's automatic packaging machine, and some is used as the semi-finished product to be transferred to the next process for bag making.

7) The bag making process is a process of heat-sealing the composite film into a bag shape according to customer requirements. The inner layer of the composite film must be a film with heat-sealing properties. The flexible packaging bag making process is divided into two types: back-sealing bag and side-sealing bag. The back-sealing bag-making method is a split type.

During production, the bag-making material is discharged by the unwinding device and then enters the forming stage, which is mainly completed by the photoelectric control system, the forming plate and the adjusting device. The bag-making material enters the heat-sealing stage. The longitudinal and transverse heat-sealing devices are used to complete the heat-sealing of the bag, and the newly-heat-sealed part is cooled and shaped. The cutter device cuts the continuous bag material into individual bags.

Common bag shapes are: mid-sealed bag, mid-sealed accordion bag, trapezoidal mid-sealed accordion bag, side-sealed organ bag, four-sided sealed organ bag, three-sided sealed bag, self-supporting bag, three-sided sealed zipper bag, self-supported zipper bag, penguin Bags, tear-off bags, bags in boxes.

2

Introduction to heat seal materials

1.Heat sealing temperature



Note: The film in the above table refers to cast film or inflation film. Bidirectional stretch film cannot be heat-sealed into bags. It can be heat-sealed after coating a layer of heat-sealable material. For example: KOP means OPP coated with PVDC. membrane.

2. Comparison of commonly used heat sealing materials for bag making

There are two kinds of heat-sealing materials commonly used in bag making: CPP and LDPE. In the case of the same thickness and film making method:

Transparency: CPP is better than LDPE.

Quite hardness: CPP is better than LDPE.

Heat sealability: CPP is worse than LDPE.

3

Components and functions of bag making machine

1.Handheld device



It consists of unwinding base, heat sealing and cooling device, forming device, traction device and winding device.

1) Unwinding device: Place bag-making materials, provide materials for heat-sealing on the palm, and control the tension of the released materials.

It consists of a seat frame, a discharge shaft and a magnetic powder clutch.

2) Heat-seal cooling device: heat seal the joint material at the palm and cool it down.

It consists of a heat-sealing (left and right) knife, a pressing wheel, and a blowing device.

3) Forming device: Form the sheet material into a folded bag shape.

It consists of forming plate, forming auxiliary wheel and fixed frame.

4) Traction device: The traction clutching material travels on the machine to control the speed of the clutching.

It consists of motor and nip roller.

5) Rewinding device: Rewind the bag-making material that has been folded into a roll.

It consists of winding frame and transmission belt.

2.Bag cutting machine



It consists of a discharging device, a traction device, a heat sealing and cooling device, a photoelectric control device and a cutter device.

1) Unloading device: Place bag-making materials, provide materials for bag-making, and control the tension of the released materials.

It consists of a discharging rack and a braking device.

2) Traction device: Traction bag-making materials travel on the machine, control the speed and tension of bag-making, and control the feeding position with the photoelectric control system.

It consists of motor, pinch roller and floating roller.

3) Heat sealing and cooling device: heat sealing and cooling at the horizontal sealing position of bag making material.

It consists of a frame, a heating plate, a heat sealing knife, a cooling plate, a spring, and a silicone plate.

4) Photoelectric control device: It controls the longitudinal position of the bag-making material during stepping, and provides guarantee for the accuracy of the cutting and heat-sealing position. The photoelectric detection head can choose a variety of reflective material positions for detection.

It consists of photoelectric detection head and control box.

5) Cutter device: cut out the continuous bag-making material to form a single finished bag.

It consists of upper and lower cutters and connecting rods.

3.Edge sealing machine



It consists of unloading device, forming device, heat sealing and cooling device, traction device, photoelectric control device, tension control and bag cutting device.

1) Unloading device: Place bag-making rolls to provide materials for bag-making.

It consists of a frame, a reel, and a material detection device.

2) Forming device: Form the sheet-like composite material into a folded shape to align the front and back patterns.

It consists of two 45 ° forming plates, a cutter, and an alignment adjustment roller.

3) Heat sealing and cooling device: The formed bag-making material is heated and bonded at the heat sealing position, and then cooled and shaped. The pressure of heat sealing and cooling can be adjusted on this device.

It consists of a frame, a heating plate, a heat sealing knife, a cooling plate, a spring, and a silicone plate.

4) Tension control device: control the tension of bag-making materials during unwinding, forming and heat-sealing to meet the requirements of bag-making.

It consists of floating roller, pneumatic valve, air cylinder, and stroke control.

5) Photoelectric control device: Control the longitudinal position of the bag-making material during stepping, to ensure the accuracy of the forming, heat-sealing, die-cutting and bag-cutting positions. Detection object.

It consists of photoelectric detection head and control box.

6) Traction device: the traction material runs forward, so that the material completes the bag making process on the machine, and cooperates with the photoelectricity and tension control system to control the traction amount of the material. Discharging, forming and discharging traction device.

It consists of motor, upper and lower nip rollers.

7) Bag cutting device: Cut the continuous bag into a single finished bag.

It consists of upper and lower cutters and connecting rods.

8) Bottom material control device: Place the bottom material, control the tension of the material, fold and punch, so that the bottom material and the bag making material enter the heat sealing device synchronously.

It consists of a feeding base, a tension control device, a folding frame and a punching frame.

4

Bag making process

1.Cross palm process

1) According to the inner width of the back-sealing bag and the size of the organ, select a suitable molding board for installation on the machine.

2) Set the heat sealing temperature according to the material structure and process speed.

3) Adjust the discharge tension appropriately. When the bag-making material enters the forming plate, under the action of the forming auxiliary tool turning baffle and the advance rubber wheel, the bag-making material forms a closed palm shape on the forming plate, and the material edge is attached at the closing position. Adjust the unloading shaft to move left and right to align the fitted material edges.

4) The heat sealing knives on the left and right sides heat seal the joints of the palms, and then the heat seals enter the clamping wheels and are pressed to make the heat seal flat. Pay attention to the distance between the left and right heat seal knives. If the distance is too small, the heat seal material cannot enter. When the distance is too large, the bag-making material is far away from the heat seal knife and prone to heat seal failure.

5) The cold wind blown by the fan cools the heat-sealed and pressed heat-sealed position to make it cool and set.

6) The rewinding device rolls the heat-sealed bag-making material into a roll shape on a rewinding rack.

2, bag cutting process

1) According to the requirements of the horizontal sealing width of the bag, select a suitable heat sealing knife to install on the machine.

2) Adjust the unloading and feeding tension to make the material run stably.

3) Set the process temperature according to the material structure and bag making process speed.

4) Select the appropriate photoelectric detection object and adjust the working status; move the position of the photoelectric detection head to make the knife position of the bag correct, and move the heat seal and cooling knife holder to make the heat seal position of the bag correct.

5) Adjust the heat-sealing pressure, time and temperature to make the heat-sealing effect good. The heat-sealing temperature affects the heat-sealing effect of the bag the most. It can be adjusted according to the melting point of the heat-sealing material and the speed of the bag making machine. The faster the machine speed, the higher the heat sealing temperature, and vice versa; the higher the melting point of the heat sealing material, the higher the heat sealing temperature, and vice versa. When the heat-sealing temperature is too high, the heat-sealed place becomes brittle, easy to break, and the heat-sealing strength is low; when the heat-sealing temperature is too low, the heat-sealing material does not melt well and the heat-sealing strength is low.

6) The traction device sends out the heat-sealed continuous bag material and cuts it into a single divided bag by a cutter.

3.Side-sealing bag making process

1) According to the heat-sealing requirements of the bag, choose a suitable heat-sealing knife and install it on the machine.

2) Adjust photoelectric correction

When the bag-making material travels on the machine, it will affect the bag-making accuracy due to the factors of the material and the equipment. The photoelectric correction system is to correct the bag-making material when the bag-making material changes from front to back and left to right. The photoelectric detection head can detect a variety of colors and patterns to ensure the quality of bag making.

Usually there is a photoelectric correction device for forming and cutting the bag. The position of the cutter in the photoelectric correction control of the forming is optional. The detection head can select the edge or line as the detection object, but it is required that the edge or line has a significant color difference with the background color and is continuous. Deviation correction controls the position of feeding and discharging, adjusts the front-back position of the photoelectric head, and can adjust the position of the cutter of the bag. The detection object requires a clear color difference from the background color, and the position is flat and stable.

3) Set the material tension

According to the flatness of the material, the tensile strength adjusts the tension of each stage of discharging, molding and heat sealing. When the tension is too small, the bag-making material moves left and right, which affects the stability of the photoelectric correction control of each section. When the tension is too large, it is easy to form longitudinal wrinkles and traction slip, which affects the normal work of the vertical correction control.

4) Set heat seal pressure

Adjust according to the thickness of the material, the heat-sealing area, and the flatness of the heat-sealing knife and silicone sheet. If the pressure is too small, the heat-sealed area is prone to air bubbles due to inadequate bonding. When the pressure is too large, the heat-sealed area is thinned. The heat seal strength becomes small. The heat seal pressure adjustment of the existing three side sealers is to adjust the heat seal pressure by adjusting the pressure of the springs at the two ends of the knife holder on the knife holder.

5) Set the heat sealing time

Adjust according to the thickness of the material and heat sealability. When the heat-sealing time is too long, the production efficiency is low, and the surface material is wrinkled due to long heating time, which makes the heat-sealed place uneven. When the heat-sealing time is too short, the heat-seal time of the heat-sealing material is insufficient and it is easy to cause heat-sealing. Low strength and bubble problems. The heat sealing time of the existing three side sealers is mainly to adjust the speed to adjust the length of the heat seal time. The time of the heat seal knife falling time can also be adjusted on the heat seal knife holder to fine-tune the length of the heat seal time. .

6) Set the heat sealing temperature

Adjust according to the melting point of the heat-sealing material and the speed of the bag making machine. The faster the machine speed, the higher the heat sealing temperature, and vice versa; the higher the melting point of the heat sealing material, the higher the heat sealing temperature, and vice versa. Temperature adjustment is entered directly on the control screen. When the heat-sealing temperature is too high, the heat-sealed place becomes brittle, easy to break, and the heat-sealing strength is low; when the heat-sealing temperature is too low, the heat-sealing material does not melt well and the heat-sealing strength is low.

7) cooling

After the bag-making material is heat-sealed at high temperature, it needs to be cooled and shaped to make the heat-sealed place flat. At present, the cooling devices of the three side sealers are water-cooled. Pay attention to connecting cold water during production.

8) Cut the bag

The heat-sealed, cooled and punched bag-making material is sent out by a traction roller and cut into individual bags. The cutter position is controlled by the photoelectric detection head position. When the upper and lower knives wear out and become dull, there will be continuous cutting of the bag or burrs at the knives.

4.Three elements of heat sealing

In the bag making process of flexible packaging production, the factors affecting the quality of heat seal are mainly heat seal temperature, heat seal time and heat seal pressure.

1) Heat sealing temperature

The effect of heat-sealing temperature is to heat the adhesive film layer to a more ideal viscous state.

Because the polymer has no definite melting point, it is a melting temperature range, that is, there is a temperature region between the solid phase and the liquid phase. When heated to this temperature region, the film enters a molten state. The viscous flow temperature and decomposition temperature of the polymer are the lower and upper limits of the heat seal, respectively. The difference between the viscous flow temperature and the decomposition temperature is an important factor in measuring the difficulty of heat sealing.

The heat-sealing temperature is set according to the characteristics of the heat-sealing material, the thickness of the film, the number of times of heat-sealing pressing, and the size of the heat-sealing area. The number of hot pressings in the same part increases, the temperature can be appropriately reduced, and the temperature can be slightly higher when the heat-sealing area is large.

In the process of heat-sealing composite bag making, the heat-sealing temperature has the most direct effect on the heat-sealing strength. The melting temperature of various materials directly determines the minimum heat-sealing temperature of the composite bag. In the actual production process, the heat-sealing temperature is affected by factors such as the heat-sealing pressure, the speed of the bag making machine and the thickness of the composite substrate. Therefore, the actual heat-sealing temperature is often higher than the melting temperature of the heat-sealing material. If the heat-sealing temperature is lower than the softening point of the heat-sealing material, no matter how to increase the pressure or extend the heat-sealing time, the heat-sealing layer cannot be truly sealed. Generally speaking, as the heat-sealing temperature increases, the heat-sealing strength will increase, but after a certain temperature, the strength will not increase. If the heat-sealing temperature is too high, the heat-sealing material at the welding place will be easily damaged, and the phenomenon of "undercutting" will be caused by melt extrusion, which greatly reduces the heat-sealing strength of the seal and the impact resistance of the composite bag.

2) Heat sealing time

Heat sealing time refers to the time that the film stays under the heat knife. It is also a key factor affecting the strength and appearance of the heat seal. With the same heat-sealing temperature and pressure, the heat-sealing time is longer, the heat-sealing layer is more fully fused and the bonding is stronger. However, if the heat-sealing time is too long, it is easy to cause wrinkle deformation at the heat-sealed weld, which affects the flatness and appearance. At the same time, if the heat-sealing time is too long, macromolecules will be decomposed and the sealing interface sealing performance will be deteriorated.

The heat-sealing time is usually between 0.5 and 1 second. When welding the hot plate, a high temperature resistant silicon cloth should be lined on the hot plate, and the high temperature resistant silicon cloth should be fixed with screws.