Dorna Servos on Paper Cutting Machines with High Performance and High Precision

Basic Info

Model NO.	servo drive
Starting Mode	Variable Frequency Starting
Certification	ISO9001, Ce
Brand	Dorna
Transport Package	Oversea Package
Specification	0.2-7.5kw
Trademark	DORNA
Origin	China
HS Code	8504409999
Production Capacity	50000 Pieces Per Year

Product Description

Application of Dorna Servos on Paper Cutting Machines

Abstract: This paper describes application of Dorna EPS series servo system on paper cutting machines based on analysis of working principle of paper cutting machines. Settings of critical of parameters of servo drives are also given.
1. Introduction
Paper industry often requires high-precision position synchronization control, especially paper cutting machines which require very high position accuracy.Speed control by ordinary inverter has been difficult to meet the requirements, and only AC servo system can achieve synchronized high-precision position control.

2. Composition of a paper cutting device

1. Traditional methodTraditional cutter is relatively simple and is driven by only one asynchronous motorgeared with a reducer to drag feeding and cutter. Length of cut paper is adjusted by cutter gear ratio. This program is simple, but paper cut error is high, resulting in poor product consistency.Each cutting length is relied on manual adjustment which is a waste of material and time.
2. Reformed approachAsynchronous motor is replaced by an AC servo motor, using the original speed proportion control to adjust speed, drive system eccentric cutter uniform motion. Feeding servo motor drives feeding rollers according to the speed of the cutter to achieve the fixed-length cutting.Entire system includes PLC, HMI, servo systems and other components. HMI utilizes touch screens for operators to set parameters and monitor the running status of the whole equipment and human-machine communications. PLC, as core program carrier, is responsible for sending pulse signals, controlling servos and processing feedback signals; controlling and coordinating the whole system. Servo system is consisted of servo drive, servo motor and encoder.As major motion component, servo system mainly carries out restraints of positioning accuracy and restraints of PLC pulse command. Meanwhile, it shall ensure self-motion steadiness and fast response during repeated loadings.The performance of servos directly reflects overall performance and quality of the whole equipment.

The appearance of areformed paper cutting machine is shown in Figure 1.

Figure 1 Appearance of a reformed paper cutting machine
3. Description of working principle of a paper cutting machine
The working principle of a paper cutting machine actually relies on a servo drive that acts as the driver. As the servo motor can calculate the detailed number of revolutions, the movement distance can be obtained. Inside the control cabinet of the paper cutting machine are servo module and calculation base board, which are used to control action of the servo motor and calculate relative position respectively.
The servo driver, according to pulse instructions from PLC, drives the motor, which then in turn drives the machine head to make positioning movement. The operation during positioning movement should be smooth. Whether the efficiency of the paper cutting machine will meet customer application needs depends on the servo operation speed. Overshoot, oscillation and excessive setting time are not allowed during high-speed positioning.
4.Dorna servo parameter settings
Set servo control, gear ratio and other parameters, and then reciprocate test. If the positioning accuracy and speed meet the requirements, commissioning is complete; If not, then increase the speed loop gain, at this time if the motor is stopped or overshoot or jitter, or the motor has noise, then means loop control parameters are too strong, then decrease appropriate or increase the integration time constant until the position and speed accuracy meet the requirements, then the position loop and speed loop proportional and integral time constant are the appropriate values.
Parameter settings for Dorna servo control system used on a certain Zhejiang paper cutting machine are given below.
X axis:
PA000=0000 (control mode selection, 0: position control);
PA012=16 (motor model selection, varying depending on motors);
PA100=500 (first position loop gain, range 1-1000);
PA101=400 (first velocity loop gain, range 1-3000);
PA102=600 (first velocity loop integral time constant, range 1-2000);
PA510=0010(logic negation of pulse input);
PA205=10(input instruction pulse multiplication numerator);
PA206=1(input instruction pulse multiplication denominator);
P508=0000(no negation of input signals);
Y axis:
PA4=0 (control mode selection, 0: position control);
PA012=16 (motor model selection, varying depending on motors);
PA11=3500 (position loop gain, range 500-8000);
PA14=1500 (velocity loop gain, range 500-8000);
PA15=3000 (velocity loop integral time constant, range 500-8000);
PA27=1(logic negation of pulse input, range 0-1);
PA31=10(input instruction pulse multiplication numerator);
PA32=1(input instruction pulse multiplication denominator);
PA38=1000 (current loop gain, range 500-8000);
PA41=10 (current loop integration time constant, range 10-50);
P64=0(enabling mode, 0: internal enabling, 64: external enabling);

Note: electronic gear ratio=PA205/PA206==Ppulse / P
Where Ppulse: Number of pulses per revolution of the motor, i.e. number of pulses from motor feedback components for each revolution of the motor (pulse/revolution). For a 2500-wire increment encoder, the number of feedback pulses to the driver is 2500×4=10000;
P: Number of instruction pulses that need to be received by the servo from the host computer to enable one revolution of the motor (pulse/revolution);
5. Notes for commissioning
To ensure reliable, stable, and correct operation of the servo driver, pay attention to the following matters during installation, commissioning, and use of the servo system:
1) Correct wiring: Dorna servo is designed with standard encoder wires and motor power wires. However, during wiring, always make sure to correct the signal wires between the servo driver and the controller, otherwise the servo will not function normally;
2) Set correct servo control mode: As each type of machine has different applications, correct setting of servo control mode is the precondition for normal operation of the servo;
3) Match gain parameters correctly depending on actual operation results. Besides, Dorna servo should not set electronic position loop and gear ratio parameters in servo enabling mode or during operation of the motor;
4) Ensure proper grounding of the motor. Connect the driver to equipment enclosure to avoid disturbance and leakage current.
5) Signal wires should adopt shielded twisted pairs as much as possible. The shield layer is typically connect to terminal shell;
6) Pay attention to interference issues to prevent the encoder signals and control signals from being disturbed. Encoder wires and signal wires should not be tied together with motor lines and power supply lines or run in the same cable tray with them. They should be routed at a certain distance.
6. Conclusion
This paper cutting device achieves highest customer satisfaction by taking advantage of features of Dorna EPS series including rapid response, precise positioning, short setting time, and stable operation. This equipment makes a full exhibition of benefits of Dorna servos,which helps improve competitive ability of paper cutting machines.