Flexo printing machine technology

First, slitting machine / rewinding machine

When people are considering adding web offset printing machines, they may encounter a variety of different roll paper principle models. Because of the different performances of various types of slitting and rewinding machines, several important and common problems have been collected here for reference and helping people find a satisfactory reel.

Before deciding to purchase, a reputable provider will ask the customer several questions:

1. What is your product?

2. What is the basic weight and thickness of the substrate processed by the rewinder?

3, roll paper adjustment how?

Although each feature of the device is important for its overall performance, the three points mentioned above are the most important because they largely determine the type of machine that should be bought. For example: Paper tension is always greater than plastic tension, so plastics require special handling techniques such as low-weight components or tension-driven guide sticks.

Relatively speaking, in the above mentioned three points, web tension adjustment is the most important. It is not only an element of calculating reel tension, but also a direct influence on reel quality and production efficiency. For example, low spool tension can cause scratches on the product, causing the web to tear on the tight roll and eventually causing paper overlap during slitting. On the contrary, excessively high reel tension threatens the overall consistency of the printing material, resulting in tension or breakage of the material.

Of course, the technical issues to be considered when purchasing a rewinder are more than just these three points. In addition, they should also consider:

1, the width of the substrate

The maximum width of the sheet determines the width, shaft width, and horsepower required of the rewinder drum. If the minimum width of the sheet is too small (as compared to the maximum width), the quality of the drum can be adversely affected.

2, the speed of rewinding

Only by knowing the maximum and minimum line speeds of the rewinding machine can we find the right-sized unwinding, rewinding and pulling roller drives.

3, roller diameter

The ratio of the diameter of the drum to the diameter of the core has a great influence on the size and the driving horsepower of the braking device.

4, roller weight

The size of cranes, lift tables, hydraulic unloading cylinders, and material handling systems all have a large relationship with the weight of the drum.

5, magnetic core size

The reel market has magnetic cores with diameters from 3 inches to 12 inches. The elliptical core will affect the cylinder plate, causing the roller to spring up and disrupt the rewinding tension somewhere in the rewinding process.

Second, roll device and reel

The next thing to consider is proper auxiliary equipment, one of which is the reel drive. There are many kinds of driving devices on the market. According to the different needs of customers, the manufacturers of reel machines will provide specialized driving devices for factories that install equipment.

Scroll type is another important factor to consider. When selecting reels for a central reel, deflection and deflection of the drum weight and composition are the most important factors. Iron reels are less deflected, but they are heavy; aluminum reels are lighter, but the material handled is also lighter. Carbon fiber reels are lightweight and can handle heavy materials, but at a high price. Customers can ask the provider to purchase the most suitable reel.

Slitter requirements

If the product requires slitting, the main types of slitters that can be considered include miter cuts, indentation slits, and razor cuts. The type of slitting machine depends on the type of material being cut.

The chamfer requires two interacting sharp knives, and the cut material passes between the two knives like scissors. The upper cutting knife and the lower cutting knife form a sharp cutting part, but the type of the cutting knife must be decided according to the use of different requirements. Chamfering is a very common cutting method because it is very efficient and has a wide range of applications. It is suitable for a wide variety of materials, such as foils, paper jams, and very heavy webs.

The indentation slitter consists of an upper cutter and a hard roller. The upper cutter acts pneumatically or spring loaded on the roll of material, with the drum behind the upper cutter. In this cutting mode, the material is accurately crushed or separated. Unlike the beveling mode, when the setting is to be changed, the worker does not have to remove the material roll from the knife edge position to reposition the cutting knife, and the material roll can remain in place.

Razor cutters are mainly used for plastics, sheets, or films (thicknesses less than 10-12 in.). The razor is mounted on an inflatable cylinder for access to the drum. Sometimes the grooved roller is used as a guide for the razor, and the razor can also be suspended in air or through a reel.

Other considerations:

Before purchasing a reel, in addition to determining the type of machine according to the process, a number of other features of the reel must also be considered. When reeling or unwinding, the reel must be pulled from one end under pressure. If the pulling distance is too large, web tension adjustment will be affected resulting in imperfect print cylinders or poor quality print registration. Pull the roller to isolate the tension of the reel or to help the elastic, brittle, soft material pass through the reel. The pulling roller located between the roll-up mechanism and the unwinding mechanism determines the line speed. The most common pull rolls are vise type and s wrap type. Vacuum drums are another method of isolating the tension on the drum. Many flexo printers have matching rollers.

Sometimes paper rolls are used to connect the paper cutters to ensure that the slitter rolls are evenly spaced without overprinting. In recent years, the drum design has also taken into account the slitting roll. There are generally concave drums, elastic slitting drums, gusseted adjustable drums, and bow rollers. Only arcuate rollers are discussed below because they are the most common designs.

There are two basic types of bow drums: fixed and variable. The angle of installation of a fixed bow roller is determined by the type of material, the reel tension and the number of cuts; the variable bow drum is the most flexible in reel cutting, and its installation angle and rotation angle are variable.

The type and number of bow rollers depends on the number of cuts, the frequency of cut width change, the material being wound, and the roll tension adjustment range. There is such an experience: for a six or less cut, a bow roller is enough; seven or more times, two variable bow rollers are required.

Third, load cell and floating roller

The most important function of all components is the roll tension adjustment, which is controlled by the load cell and the floating roller. The load cell is responsible for monitoring the roll tension adjustment. It is a sensitive electronic component that senses the force of the material roll acting on the idler. The load cell then sends a voltage signal corresponding to the roll power to the machine. On the brake, depending on the size of the voltage signal, the brake then decides whether to accelerate or decelerate.

Floating rollers are mechanical devices. Changes in the reel tension will cause the idle wheel to oscillate back and forth in the middle. The electronic potentiometer attached to the swing axis sends a voltage signal to the brake. The brake determines the speed of the machine based on the voltage signal and sends a signal of speed change to the rotary axis to restore the intermediate state.

Uncoilers and reelers

The next step in assessing the purchase is to decide what type of uncoiler and reeler is best suited for production and operation. The uncoiler is the process of opening the wound material in a controlled manner. Presses, coaters, laminators, and slitters all have associated unwinding mechanisms. In order to avoid affecting the registration during flexo printing, a flexo press requires an automated, continuous unwinding mechanism.

The unwinding machine can be equipped with a variety of additional equipment: tension controllers using floating rollers or load cells, edge (center) roll guides, skew adjustments, edge adjustments, roll rolls, and the like. These devices will directly affect the unwinding of the web, based on the type of material being rolled and the process.

There are two basic principles for reel and rewind machines: surface roll and center roll. All reelers use a combination of these two principles. There are two main reel machines in the flexographic industry. The first type has three to four coiled drums that can cut off and transfer the reel in motion. This type of machine is best suited for the paper that rolls need. Rollers with a maximum diameter of 60 inches and a maximum width of 108 inches can easily exceed 1500 fpm. The other is the automatic turret reel. It includes two reels that rotate around or around the center axis and can automatically change the reeling task. This type of machine is best suited for plastics, films, and sheets, but it can also be used for paper. It is often used in narrow-web printers because it is cheaper than automated surface reels.

There are some new variable operations for off-line cutting. According to operation needs, online cutting may be considered, that is, cutting raw materials with different required widths in the printing process, which can reduce the use of the off-line cutting system.

Although there are many possible methods for the same cutting/coiling task, the materials for each machine are different. Also, each raw material has its own unique machine requirements. The above suggestions can be used as reference for people to buy machines, but the best way is to provide the provider with as much information as possible before buying.