The can-products that we currently see in the market (such as Coca-Cola, Sprite, and Pepsi) all have something in common: First, they are made entirely of aluminum sheet; Second, they are divided into can bodies and can lids. The lid consists of a round aluminum sheet and a pull tab. These products are called Two Pieces Can.
1. Can making process
(1) Unwind and lubricate The aluminum plate of the reel is pulled apart, and the lubricant is sprayed on the stamping surface to ensure good sliding between the punch and the aluminum plate during stamping so as to avoid damaging the plate. Lubricants are talcum powder, animal fat, mineral oil, petrolatum, etc.
(2) Roll forming The cylinder forming product is formed by a roll forming method, as shown in Fig. 3-21. The blank 3 is sandwiched between the swivel block 2 and the friction block 4, and the billet is pressed on the swivel block by the swivel tool 6. In this machining program, the billet, the swivel block, and the friction block rotate, and the rotary tool pair The quasi-swiveling centerline moves axially horizontally, and the metal is semi-pressed and half-bent shaped by the tool.
(3) Deep drawing forming (deep drawing forming) The flat blank is placed on the mouth of the cylinder die and clamped by the chuck to form the edge of the blank. Above it, a flat bottom punch with a smaller hole diameter than the die hole acts downwards, and the bottom of the blank is pressed and pulled. Stretch forming. The flat blank becomes two parts, one with the same diameter as the punch and one with the outer ring (flange), the former being the bottom and the latter being the cylindrical wall, as shown in Figure 3-22. The depth of lubricant used is undiluted oil, butter or soap emulsions.
(4) Washing, drying, and deepening The can body is covered with oil stains. It is necessary to enter the washing machine for oil removal and drying.
2. Printing process
Aluminum cans are printed using a typical curved printing method, which is a letterpress offset printing.
(1) Plate printing plates are arc-shaped copper plate or resin plate. Since the printing cylinder is cylindrical, the plate should also be curved to avoid excessive image distortion. Both ends of the plate are used for the upper plate, and two hooks should be made. There are crosshairs at both ends of the plate (see Figure 3-23), which are used for platemaking registration. The length of the plate on the printing plate is longer than the circumferential length of the can by 0.5-2 mm to form a printing overlapping edge to prevent the pattern connection from being exposed due to the deformation of the printing plate.
(2) Offset printing presses for printing presses are divided into four-color machines and six-color machines.
The printing part of the two-piece can production line consists of an inking system, a mandrel turntable, and a blanket turntable system. The inking system in the figure consists of 6 units, each of which is a color group, and 6 units are sequentially arranged around the rubber turntable. There are eight fan-shaped blankets on the blanket plate for transferring various color patterns. The counterclockwise rotation of the blanket turntable transferred the various patterns onto the 24 white cans set on the 24 mandrels on the mandrel turntable.
1 printing system introduction. In the printing area, a drive belt from the blanket turntable drives the cans on the mandrel and the blanket to rotate together (roll on) at the same linear speed. Since there are only 8 blankets and the mandrel (or white can) on the mandrel turntable is 24, so to maintain the same linear velocity, the angular velocity of the two turntables should be different, that is, the angular velocity of the blanket turntable is the core Shaft rotary speed 3 times.
The white cans (chemically processed, unprinted cans coming out of the front section) were transported from the top to the mandrel turntable. The 24 mandrels on the turntable, after being accurately positioned, were inhaled one by one and set on the mandrel. It is then transported to the printing section, the tangent to the mandrel and the blanket. Here, the white cans have been pre-rotated to the same speed as the surface speed of the blanket, and after printing with the blankets, the pattern is transferred from the blanket to the white cans.
After the printing is completed, it is transferred to the side of the tank body varnish, a layer of varnish is applied to the surface of the printed can body to protect the printed pattern and increase its brightness; then the primer is applied to protect The bottom of the tank; Finally in the oven at 170 °C temperature baking 2min, you can complete the processing of printed products.
2 ink system and blanket turntable. The 6 inking units are detachable. Because each unit corresponds to the angle of the blanket turntable, different angles are designed for the support frame of each inking system.
The blanket turntable consisted of eight fan-shaped irons covered with a blanket to receive the printed pattern transferred from each inking unit and then transferred to a white can. There are different lines (a total of six) on the eight iron scallops. This will be
The zero position when different inking systems are installed on the blanket turntable, ie, the gears of each inking system and the bull gear of the blanket turntable have fixed requirements on the meshing position, so that various patterns can be provided on the blanket. Fixed overprint position.
Here's an introduction to the ink system.
Although the six units have different angles, the basic structure is the same. The ink system performance of each ink roller and its role are described as follows:
E: ink fountain roller. It is made of a ceramic layer coated with steel. The steel roller has a fast heat dissipation and can increase the wear resistance and the affinity and transferability to the ink after the external plating of the ceramic. For the printing process requirements, the movement of the ink fountain roller is designed to rotate intermittently with adjustable stroke (for different ink volume requirements).
C: Swing roller (rubber roller). Swing from side to side during work to transfer the ink from the ink fountain roller to the below uniform ink system. Since the ink is transmitted by swinging left and right, the parallelism of the roller must be adjusted so that the ink of the entire ink roller can be transferred accurately and in time.
B1, B2, B3, B4: Ink rollers. All steel rollers are coated with ceramics, but the diameters of the rollers are different. In order to meet the requirements of heat dissipation, an internal water circulation thermostat is also specially provided for such rollers to avoid changes in the process characteristics (color, viscosity, etc.) of the ink due to the increase in the temperature of the rollers, and prevent the printing from proceeding normally.
D1, D2, D3: Ink roller. They are placed between the steel rollers and form a "steel soft" uniform ink system (the steel-steel combination is extremely abrasive and the glue-glue combination is prone to heat).
A1, A2, A3: Reliance on plate rollers. All are rubber rollers, but with different diameters, one is mainly used to ink the printing plate, the other is mainly used to even out the ink onto the printing plate so that the ink is evenly coated on the printing plate.
F: Plate roller. Because there is an indirect carrier-blanket between the plate and the substrate (white can), the plate used in the printing press can be resin-engraved.
The above inking system has the following process features:
• Thermostatic ceramic steel rollers ensure the stability of the process characteristics (such as color, viscosity, etc.) of the ink during the transfer process;
• Axial commutation of the externally plated steel roller and the structure of adjustable parallelism ensure that the ink axial transfer is uniform;
• The uniform ink system composed of different diameters of rubber rollers and steel rollers ensures that the radial transfer of ink is as uniform as possible (without bar).
8 on the device. In order to ensure accurate overprinting of the two-piece cans, it is necessary to ensure that the six-color (for the six-unit inking system) printing plate is based on the same reference, and that the color plates do not interfere with each other after adjusting the reference. For this purpose, a 0.03mm-precision aligner (shown in Figure 3-26) was designed to magnify the registration crosshairs for each color plate by 20 times for register adjustment. Therefore, as long as the crosshairs on the front and rear plates of the plate are tightly aligned, even if the error is 0.03mm or slightly larger, the accuracy of printing images can be guaranteed within 0.1mm. To meet the printing quality requirements.
Even if there is a slight error in the position when drawing or loading, the angle of the printing plate can be slightly adjusted in the circumferential direction as well as in the axial direction by using a mechanism in the machine that can adjust the position of the plate circumferentially and axially.
4 pneumatic devices. The printing machine is equipped with a plurality of pneumatic devices, which respectively control the advance and retreat of the printing blanket cylinder, advance and retreat of the needle wheel, advance and retreat of the polishing machine, and removal of can blanks. In this whole process, the mandrel is changed from air inhalation (when sucking white cans), airless (after printing), and inhaling (glazing oil) to blowing, blowing the cans to the transfer carousel On the suction cup that is inhaling, send the printed jar to other parts for further processing...
(3) Introduction to Printing Process The printing process principle of the printing tank is shown in Fig. 3-27 (only the three-color printing plate cylinder is shown in the figure).
After transfer to the can, the print cans are rotated to the upper light area.
(4) Postpress
1 Apply Varnish. The finished printing tank is driven by the needle wheel and enters the coating oil coating device. After coating the can body with coating varnish, it is also necessary to coat the protruding edge of the can with coating oil so that the jar can move and rub at the later filling operation. Reduced force;
2 spraying and flanging process. Same as three-piece cans;
3 easy to open the cover. The easy opening cover is an abbreviation for a pull ring type easy opening cover, which has an indentation and a pull ring, which is easy to open. The cover of the easy-open lid is the same as the three-piece can.
