Efficient engineering on one PLC platform

Author : Sandra Pringnitz and Mirzan Elmazi, Siemens AG Industry Automation

12 July 2010

Just three days after unpacking the S7-1200, Siemens’ new generation compact controller, it was integrated in an existing application. Sequential control was optimised, Ethernet communication with the vision system and an SAP computer were established, and the visualisation created. The new Step 7 Basic engineering system with integrated PLC and HMI functionalities makes rapid deployment possible.

The Simatic S71200 only provides a ready signal for bracing when the rotational position and direction of the needle-printed data matrix code are correct …
The Simatic S71200 only provides a ready signal for bracing when the rotational position and direction of the needle-printed data matrix code are correct …

Emcon Technologies Germany GmbH (Augsburg) wanted to establish more reliable production steps and subsequent assembly operations. The company also wanted to make these steps traceable in order to document the quality and process safety.

As part of the process a data matrix code is needle-printed in the shell of the cylindrical soot filter catalyser body (see photo). A specific, and difficult requirement was that after the assembly is finished, the needle-printed code must be legible from below.

Another requirement is to be able to use the code to ensure the correct order of components when welding, and thus the correct flow direction.

To achieve this when manually inserting the catalyser body into the welding equipment, it is necessary on the one hand to monitor the rotational position of the data matrix code and on the other hand its horizontal orientation. The connection flange and the catalyser body are braced together and welded only if the rotational position is exact to within ±2 degrees and the orientation is also correct.

After welding, the catalyser body is checked to see that the welding seams are tight and the data matrix code can still be read.

And finally, the results of these individual steps are automatically transferred to an SAP system and saved. This is a typical task for a vision system, and NeuPro Solutions GmbH, an experienced system integrator in this special field was commissioned with its interfacing. The  Vilsbiburg-based company is a Siemens Automation Solution Partner.

Integrated Profinet interface
Because it had to be carried out quickly and at low cost, it was agreed that the existing control program should not be significantly changed, and that a PC-based vision system together with an additional Simatic S71200 compact controller should be integrated into the existing process.

NeuPro selected the newly launched Simatic S71200 for the task. One of the main selection criteria (in addition to the price) was the integrated Profinet interface which permits fast Ethernet communication with a programming device, HMI systems, and other controllers without additional hardware.

… and then permits welding of the catalyser body and flanges.
… and then permits welding of the catalyser body and flanges.

Target met in three days
Matthias Koitzsch (PLC) and Martin Ecker (vision system), programmers at NeuPro Solutions, produced a stable solution within record-breaking time: the PLC was delivered on Tuesday afternoon, and the application was ready for on-site customer acceptance on the following Friday.

“In my opinion, the graphic engineering framework has an exceptionally clear design, you get a good feel for the system quickly and intuitively, and you can work fast,” said Matthias Koitzsch.

“It offers, within one system, editors with an almost identical structure for control and visualisation tasks which are uniform in both appearance and operation. The data are automatically updated and kept consistent, meaning that variables created during PLC programming are immediately available in the HMI component of the application, and vice versa. This saves multiple inputs, errors and time.”

The engineering system facilitates two basic approaches. The ‘portal’ view, with all editors for an automation project, leads beginners to their goal— oriented according to the tasks.

On the other hand, the ‘project’ view presents the hierarchical structures of the entire project in a tree structure. This allows fast access to all editors, parameters and project data. It is designed for an object-oriented approach.

There are pre-defined screen forms for certain system functions, such as the creation of an Ethernet connection. If the corresponding interface is clicked in the graphic display of the controller on the screen, a screen form is automatically opened in which the IP address and communication port can be entered, and the connection configured.

Thus the NeuPro programmers, who are already familiar with Siemens engineering systems, had little problem in doing their work without instruction or training. It was relatively easy to integrate the controller into the existing cell network thanks to a switch that was already available, and data exchange with the vision system and the host Box PC with certified SAP interface could be implemented quickly and easily.

Relevant production steps and statuses are recorded in data blocks and automatically archived via Ethernet following each cycle. Data are exchanged internally via an OPC server. A solution is being worked on for reading and sending I/O signals directly from the image processing program, which would mean even further simplification and acceleration.

The Simatic S7-1200, with a mid-performance CPU 1212C, controls the LED illumination, a protective cover for welding, as well as two diodes which signal the correct direction and rotational position of the catalyser body to the operator during insertion.

Functionality and economy in one package: With Simatic S71200 and Simatic Basic Panel KTP400 mono PN, Emcon Technologies modified an established production procedure quickly and efficiently.
Functionality and economy in one package: With Simatic S71200 and Simatic Basic Panel KTP400 mono PN, Emcon Technologies modified an established production procedure quickly and efficiently.

In this case the engineers used only the integrated functions of the compact controller, which has a 25 KB internal RAM and eight integrated digital inputs and six digital outputs. The central unit, which is only 90 mm wide, is snapped onto a standard DIN rail and has removable terminal blocks which simplify assembly and wiring.

If necessary, the modular control system can be expanded by digital or analogue I/Os using optional signal modules or signal boards which can be directly plugged onto the CPU. Additional communication modules for serial communication can also be retrofitted.

Compact and cost-efficient HMI
A Simatic HMI Basic Panel with a monochrome touch display was installed in the control abinet. It is the smallest (3.8 inch) and most inexpensive device of the new HMI family. It has four tactile function keys is connected to the controller over its Profinet interface. The panel was originally intended for visualisation at the insertion workstation, and subsequently used for diagnostics, optimisation and maintenance,

The HMI Basic Panel is configured like the S71200, using the Simatic Step 7 Basic engineering system with integrated WinCC Basic. The framework always offers the basic functions required for both ‘worlds’ at the same position and helps engineers avoid time-consuming searching right from the start..

When the machine is in production, the panel visualises a product number saved in the data matrix code, the current rotational position of the code during insertion, and whether the direction is correct or not.

The ‘library’ concept of the new engineering system is also useful. Software elements which have been created once, such as function blocks, variables, alarms, HMI screens or program modules, can be saved in local and global libraries and also imported into other projects as required.

The first application for NeuPro Solutions has shown good results. With the integrated Profinet interface, the new Simatic S71200 is ideally suited to a comparatively compact and cost-efficient automation solutions for inbound logistics scanners.

The production planner at Emcon Technologies was satisfied with the conversion process and results. The completion of the project in just three days, with little impact on the production facilities, made a particularly good impression. And this has remained the case—so there has not yet been an opportunity to work with the new system to test repair and maintenance.

—Sandra Pringnitz and Mirzan Elmazi, Siemens AG Industry Automation, Industrial Automation Systems, Nürnberg, Germany

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