In the first half of year 2008 our team realized full replacement on twenty year old computer directioned automatic production line for metal segments for grill pillars in department CRS - Kicevo for Emo - Ohrid.
The productions line process is fully automatic and it involves production of iron L - profil segments, from which grill pillars for electrical pilon (transmission tower) and similar metal constructions are composed. For example, the giant cross on Vodno hill near Skopje.
This project involved solving the following problems:

• Replacement of old computer system for programming based on 286 technology, with modern computer system using application developed with new Microsoft technologies, using Dot Net Framework 2.0.
• Replacement of old automation system based on electrical modules with newest technology with Programmable Logic Controllers (PLC) and interface modules.
• Galvanic separation and logical connection of the commands from the new automation equipment to the previous contactor disposition for control of the existing pneumatic and hydraulic executive components of the system.
• Replacement of electromotor drive with direct current direction with modern vector AC 3 phase motor.

Positioning the drilled profiles on horizontal axes is conducted with a mechanical hand mounted on a mobile platform. The hand holds the profile with pneumatic pliers. Positioning of the mobile platform provides translator offset of the metal profile, which can be drilled in extent of sixteen meters. For moving the mobile platform there was a DC motor with permanent magnets for 130 V voltage and 504 A maximal current.

Our solution is based on 3 phase servomotor 2.2 kW and vector drive for its direction. The power decrement of the drive motor is about 20 times, and it dousn't degenerate the characteristics of the drive, but opposite of that, they stay on same level as they were before. This is provided by modern vector regulation. The AC drive is directly commanded from a PLC, witch use incremental encoder as a callback information for positioning of the mobile platform .

With this solution we achieved:

• Drive for the mobile platform, without current picks and low energy spend
• Reliable and robust(fault resistance) drive,
• High precission positioning of the mobile platform with maximal error of +/- 0.25 mm.

Our engineers created a system for controlling the process line with a PLC, external I/O modules and standard electric relay and contactors for output devices.

This system use modern PLC's, programmed in Ladder logic like a part of world standards for building SCADA (Supervisory Control And Data Acquisition)systems.

With this we achieved:

• Easy upgradable system
• Easy maintenance of the automatic line
• Complete fullfilment of the client's demands

Equipment

PLC's and external modules are a standard equipment for systems involving automatic regulation of an industrial process.

We use equipment from a reliable vendor for production of PLCs and I/O modules - Unitronics. The full process control on this line is provided from one PLC and four I/O modules.
Programmable Logical Controllers are real time.
They regulate the process of manufacture drilled mettal profiles.

All PLCs are programmed, for manual and automatic mode, with all restrictions and validation for secure work .


Programming and Communications

Unitronics provide communication between Programmable Logic Controllers and PC with TCP/IP (30 years old reliable communication protocol). Their drivers, made for that purpose, are used by our application to exchange data from PC to PLC and visa versa.
The program loaded in the PLC can be easily replaced with newer and every future change or future upgrade can be done in the simplest way.
With this we provide permanent and stabile solution for a long period.

The application software offers it's user simple and efficient way for parameters setting, process monitoring and command execution. The entire process of process control and monitoring is followed by graphic representations of the industrial process. The shape of the metal profile and all actions that will be executed while processing it are graphically represented by picture drawings. This drawings is dynamically updated when a new action is added or a change is made. Also there is an animation of the process while the process is running.

The program offers several workings modes. They are automatic, step by step and manual. In manual mode the user executes command by his decision. In other modes, the software defines the steps of execution and their order.

During the process execution, the worker is ensured from taking actions that can provide material or machine damage. This is made by validation of entered values via checking the data range, data type and implementation of data constrains.

For software development we used Microsoft .NET framework 2.0. The software written in C# and the Database platform is MS Access 2003.

We used ethernet and the vendor's PLC driver for cimmunication between the PLC and the PC software.