TANDEM COATER LAMINATOR

As an example of a typical project, we describe herein a job in which we carried out the upgrade of a tandem coater laminator line drive system for a large UK based flexographic packaging company.

This complex multi-drive line drive system used latest technology digital thyristor drive equipment, using a fibre optic network for all signal connection and "touch screen" operator stations for operator input. The use of such technology allowed a relatively simple and short installation time, minimising the project capital cost. The existing control system had just two large motors with line shafts and PIV gearboxes, powering half the machine each. The line shafts were completely removed and new motors and transmissions specified for each individual section. New load cells and rolls were added in the optimum web positions, in order to measure section tensions. The two existing motors were retained to drive the two laminating sections, in order to reduce cost. The line drives were designed to allow further inclusion of the unwind and rewind sections at a later date.

The basic steps involved in delivering and putting into service a drive system re-fit, can be summarised as:-

Quote to customer requirements
Detailed on-site survey
Project specification
Design
Drive system build
Functional test
Shipping and installation on site
Commission
Training of on site personnel
Service
The initial on-site survey is carried out by a skilled application engineer. For the best continuity, it is usually this engineer who will manage the future project.

The crucial part of any project is a highly detailed specification of requirements for the drive equipment. It is this document alone which allows the customer to evaluate the equipment that will be delivered to site. It also specifies the technical requirements to allow the design to proceed. It is the policy at Optima Control Solutions Ltd. that the design of any control system will not proceed without this detailed and mutually agreed project specification. In many cases, a brief specification is prepared, providing the necessary detail to allow an initial quote to proceed. As an example of the specification content, the following items are included:-

Customer information and contact names
General description of the drive system requirements
Motor and power transmission specification
Enclosure specification
User input / output description
Special requirements
Safety and EMC requirements
The General Description section for example would contain a detailed schematic diagram, similar to that shown below for the extrusion coater/laminator

With this diagram and some description, the basic control philosophy of the line drives is specified. Existing motor and transmission systems are discussed and new equipment specified. An important item is the naming of the various machine sections and operator controls.

During the design phase, close contact takes place with any mechanical subcontractors responsible for fitting of such equipment to ensure that mistakes do not occur. All design and construction work is in accordance with applicable national or international standards.

The enclosure specification discusses such topics as:-

Dimensions and Colour of enclosures
Operating environment
Ventilation
Incoming circuit breaker location
User connection terminal locations
The user input / output specification details each of the user controls, such as pushbuttons, potentiometers and operator stations. Each control is specified as to the type, location and functional description. Guidance is also given with regard to risk assessment and choice of emergency stop systems for the line drive, in order to meet the machinery directive.

For the extrusion coater laminator project, the use of fibre optic technology allowed a dramatic reduction in user control wiring but is not without pitfalls. For example, with plastic fibre cabling used for the drive system network and speed feedback, the cable lengths must be closely specified, and this was done in the project specification. The actual fibre optic cable routing was determined during the initial site survey. On completion and issue of the project specification, a simple change control procedure is used to ensure that changes can be easily tracked when new issues are released.

When the specification has been agreed with the customer, the design can proceed and electrical drawings prepared for the drive system. In this role, Optima Control Solutions Ltd. provide a design and consultancy service. The completed electrical drawings are then sub-contracted for panel build according to our own detailed construction specification. The completed drive system is then tested as fully as possible to minimise time on site during commissioning. All software is loaded in both drive and ancillary equipment such as PLC's. Where possible, software testing is also undertaken at this stage, to reduce site time. In this case, the use of plant simulation computer tools is being investigated in order to more thoroughly test PLC software, and further reduce on site de-bugging.

The installation phase can be organised by the customer or planned as part of a turnkey project. "Complex" cables, such as fibre optics and encoders are terminated up by our engineers, in order to reduce errors and improve system reliability.

The commissioning phase is where the machine is put into service and involves setting up drives, sequencing and control loops. A significant amount of testing takes place of critical items such as emergency stop systems etc. As commissioning proceeds it is usually the case that machine operators become more involved with the project, and significant machine training can take place at this stage.

Training is of vital importance to on site personnel, in order that the new equipment can be correctly operated and maintained. The issue of stocked spares is often raised at this stage as a conclusion to the project.