Delta inverter application in gravure printing machine

Taking actual gravure printing machine debugging as an example, the application of Delta VE series frequency inverter on gravure printing press is introduced.

Gravure printing is one of the printing processes. It is called four printing methods together with lithography, letterpress printing, and screen printing. Gravure printing is a direct printing method. Grooves on the printing plate are printed letters and patterns. The ink is filled in the grooves first during printing, and excess ink on the printing plate (ink on the non-printing surface) is scraped off. The ink knife is scraped off, and then the printing plate is pressed by the platen roller to press the ink from the concave surface of the printing plate to the object to be printed, thereby achieving the purpose of printing.

The selection of substrates for gravure printing is diverse, and the printing quality is stable. The printed matter is superior in terms of level performance and image quality. In Europe and the United States, it is developed as the main subject of mass-produced publishing and printing, and in Japan it is It is popular with the package gravure as the center.

According to the type of gravure used and printing methods, gravure printing can be divided into four categories: hand-engraved gravure printing, chemical etching gravure printing, electronic engraving gravure printing and indirect gravure printing. Gravure printing machine can be divided into unit type and satellite type; sheet-fed gravure printing machine and web gravure printing machine; monochrome gravure printing machine and multi-color gravure printing machine.

Gravure printing machine structure and system

The basic structure of a gravure printing machine is: a paper feeding device, a printing device, an inking device, and a delivery device.

The control system of the printing press is very complex and generally can be divided into several parts: the tension control system, the registration control system and the drying system. Today we mainly analyze the tension control system.

The purpose of the tension control system is to ensure that the tension of the printed material is constant or to meet customer requirements.

In the tension control system, the following three methods are commonly used:

1. Torque motor tension control system

2. Magnetic powder brake (magnetic clutch) tension control system

3. Frequency converter tension control system

Torque motor control system has the advantages of simple structure, stable tension, the disadvantage is narrow adjustable range, poor linearity, suitable for applications where tension accuracy is not high, such as cables. Magnetic powder brake control system has the advantage of good tension stability, the disadvantage is that the linearity is not good, the coil diameter range that can be controlled is not large, there is a fever problem in long-term work, need to dispose the external heat dissipation system. Inverter control system has the advantages of stable tension control, fast system response, simple structure, wide adjustable speed range, and support of special algorithms, which can well support occasions with large changes in coil diameter; through the common DC bus, Continuous roll-out occasions can play a role in energy conservation. With the development of semiconductor chip technology, the drive drive technology performance has been greatly improved, but the price has shown a downward trend, showing a good cost performance, and has been recognized by the majority of users.

Delta's actual application in gravure printing machine

1. basic introduction

The gravure printing machine commissioned in this case is a machine-type printing press, which is mainly used for preprinting of 80-400 g/m2 carton, paper printing for cigarette packs, paper boxes, etc. The printing color group is two colors. The maximum line speed is 100m/min, and the maximum reel diameter is 1500m.

Due to the tension of the device, the tension controller adopts the tension controller + magnetic powder brake + tension sensor, and the winding tension is controlled by the inverter. Therefore, the difficulty of the device lies in the control of the winding tension, and the tension should be appropriate: the tension is too small, Relax when rewinding; too much tension, wrinkles easily when rewinding. In addition, since the diameter of the paper is continuously increased at the time of winding, if the rotation speed of the take-up reel is kept constant, the rewinding speed of the paper becomes larger and larger, so that the problem of pulling the paper easily occurs.

2. Delta inverter application introduction

On this press, the VE series inverter that can be controlled by Delta, which can be controlled by Delta, can automatically realize the purpose of constant tension of the printer through the inverter's control of the motor. The entire application is easy to adjust and cost-effective.

The constant tension control formula is:

T = ( F * D ) / ( 2 * G )

Where T is the output torque of the motor, F is the tension on the wire, and D is the actual size of the take-up/discharge roll. The purpose of constant tension control is to control the size of F constant, but the inverter can only control the output torque T of the motor. If we know D, we can control T to achieve the purpose of controlling F.

Using Delta VE series inverters directly provides constant tension control by controlling the torque: Parameter 8-21=4.

Since the actual size D of the take-up/discharge roll changes with the running time, the accuracy of the D value is the key to the success of this method. At present, there are usually two ways to refer to: 1 thickness method; 2 line speed calculation method.

The principle of the thickness method is based on the knowledge of the thickness of the material. For each rotation of the motor, the diameter of the take-up roll increases by two thicknesses, and the diameter of the take-up roll reduces the thickness of the two materials. This method is mainly used in the case of a uniform thickness of the retractable roll material. The advantage is that the calculated thickness value is accurate. The disadvantage is that the user needs to input the material thickness information in the relevant parameters of the frequency converter.

The formula for the linear velocity calculation method is: D = (G * V) / (Ï€* n )

Where D is the current coil diameter, G is the mechanical transmission ratio, V is the current line speed, and n is the motor speed. The current line speed can be captured in analog or pulsed form. The linear velocity calculation method can be used in situations where the material thickness is not uniform and does not require the setting of the material thickness value, which reduces the requirement for the operator; the disadvantage is that the calculated current coil diameter value will be affected by the accuracy of the linear velocity collection. If the line speed fluctuates greatly, the current volume diameter will also fluctuate greatly.

Some curl control requires that the material tension be reduced as the diameter of the roll increases, to prevent damage to the spool and to improve the quality of the product. This device has the need for a tension taper.

There are various formulas for the tension taper. One of them is introduced here: F=F0 * [1-K(1-D0/D)]

Which F actual output tension, F0 set tension, K tension taper coefficient, D0 minimum roll diameter, D current roll diameter.

Because this device is a general-purpose device, the tension taper of different paper requirements is not the same, so the analog taper is required to set the tension taper.

3. parameter settings

The main traction motors are asynchronous motors (15kW, 380V, 29.6A, 1430r/m, 50Hz). The traction roller diameter is 320mm and is controlled by a 15kW B-series inverter. The maximum linear speed of this equipment is 100m/min. The winding motor is an ordinary asynchronous motor (380V, 58.5A, 4 pole, 50Hz/30kW). It is controlled by a 300V43A-2 inverter (EMV-PG01O). The motor has a 512ppr encoder with a reduction ratio of 6.77:1. The maximum winding diameter is 1500mm.

Based on analysis of customer requirements, we decided to use the thickness integral method to calculate the roll diameter, and the winding frequency converter adopts torque mode control. The analog given tension and the tension taper can be adjusted.

in conclusion

The Taiwan equipment uses Delta's inverter to control the winding part. Compared with the customer's previously used solution (tension clutch), it can achieve larger coil diameter change (maximum coil diameter can be 1500mm from 1000mm), and faster line speed (max. The line speed can be 100m from 60m, and the tension is stable, the debugging is convenient, and the value of the equipment has also been greatly improved. This program has been recognized by customers. Customers are currently requesting manufacturers to change the unwinding section to Delta inverter control mode.