Siemens Single Servo Axis Rotary Knife Solution
Packaging

20 Dec 2010, 15:49 Sinocorrugated

Siemens Single Servo Axis Rotary Knife Solution with High Performance-Price Ratio to be unveiled at SinoCorrugated 2011

Introduction
As China, one of the world's most voluminous manufacturers, continues to develop, the packaging industry is rapidly expanding its manufacture of industrial products. Today, China is the leader in the manufacturing corrugated packaging products, composite flexible packaging, metal drums, containers and plastic bags. With paper, plastics, metal, glass, printing, and machinery as the main components, China's packaging industry is now a relatively complete system characterized by modern technologies and equipment.

In the packaging industry, corrugated cardboard is widely used. Almost all products from light industry, such as food, beverages, tobacco and electronics are packaged in corrugated cartons. Moreover, cross-cutting is a very important step in the corrugated board production line and is also the last step before the manufacturing of packaging boxes. Therefore, the performance of the rotary knife is an important factor in the quality and output of products. The rotary knife stage is also one of the most highly automated steps in the corrugated board production line.

Industry Background
To meet requirements on machine speed, rejection rate and order-changing flexibility, Rotary knife is being promoted increasingly extensively. Depending on different control systems, the rotary knife can fall into two categories:

The first category is controlled via MCU (including closed-loop position) and general converter. The speed command is then sent to the converter that drives the feeding of the motor and board. The benefit of this is its low cost. But, as the cycle of the MCU's control, when it is in the closed-loop position, is longer, the precision of the speed setting falls as speeds increase. At the same time, as the subsequent performance of general converters is poor, converters do not perform the setting accurately. This brings about further errors.

The second category is realized via motion control system and servo drive. The closed loop position is directly controlled by the motion control system. Computing cycles lasting milliseconds, or even microseconds, guarantee a high precision of position setting. At the same time, the excellent tracing performance of the servo system guarantees higher precision.

The rotary knife solution described in this article uses the Siemens motion control system and servo drive.

Mechanical Structure
In the current corrugated paper production line, the cross-cutting section is commonly known as the cutting platform. Generally, there is only one knife roller motor on the cutting platform. There is no automatic feeding. Even if there is a feeding motor, it will be driven by a common converter instead of a servo drive. Therefore, the amount of corrugated board being fed in will first be detected by a measuring roll. This quantity will be sent to the motion control system. The knife roller drive will be controlled by electronic gears or via an electronic cam function.

System Configuration
The following figure shows the system configuration of the Siemens motion control system SIMOTION D410 and servo drive Sinamics S120.

The system includes the following components:

The upper Industrial PC acts as a human-machine interface. It has user settings, can manage orders and communicate with the entire control system;

SIMOTION D410 is the latest single axis motion control system from Siemens. It communicates with the upper Industrial PC via standard industrial ethernet (D410 PN). It can interpret settings, receive orders and send out the machine's real-time information (machine speed, motor current and motor temperature) to the Industrial PC for processing and display;

Servo drive Sinamics S120 receives the position command from the SIMOTION D410 and samples the knife roller position every 125 microseconds. It also controls the position closed-loop (when the Servo control function DSC is activated) and drives the knife roller motor's operation:The external encoder, installed on the measuring roll, detects how much corrugated board has been fed in, which marks the position of the electronic cam's main axis.

When you need to perform cross- cutting tasks according to the print mark on the corrugated board, you can connect the output of color code sensor to SIMOTION D's quick input point. SIMOTION D can also be programmed to achieve print mark position compensation.

The performance highlights of this solution include:

1.cutting with Electronic cam;

2.Quintic polynomial cam profile that reduces the impact on the mechanical systems;

3.Synchronized knife roller with and material moving during cutting. Over-speed synchronization can be achieved;

4.The cut length can be changed without shutting down the machine. It takes immediate effect;

5.Cutting based on print mark can be performed.

We at Siemens will be delighted to come face-to-face with visitors at Sino Corrugated 2011. We are looking forward to fully demonstrating the single servo axis rotary knife solution, meeting customers' needs and helping them maximize their profit with minimal investment. At Siemens our goal is to be the go-to partner for every one of our customers.



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