Maximise blown film production output

Storing, conveying and distributing materials (especially additives) precisely and efficiently in a plastics processing plant can give significant cost savings. This is the case of Selene, a producer of thermoplastic film, which has recently implemented Winfactory, the innovative supervisory software of Piovan.

1 – Objectives

Automation, tracing, optimisation

Selene, an extruded plastic film manufacturer in Lucca, Italy, needed to organise their production processes for improved efficiency. The production process starts with order acquisition and booking in the company's ERP system. The process parameters are then analysed to plan production. This is where Winfactory comes in - Piovan's software for organising the distribution of raw materials from the silos to the extrusion lines, using conveying and blending equipment. The system sets up automatically and requires minimal operator intervention to ensure that the extrusion plant operates in accordance with the job orders. Winfactory provides total raw materials tracing in relation to production orders, as well as optimised handling of job queues, thus minimising wastage between production runs. The system also monitors materials to optimise stock management.

2 – Characteristics

Seventeen kilometres - that's a lot of pipe. That's how much pipe the Selene plant uses to transport its raw materials. The priorities are automation, precise and accurate distribution, and traceable consumption. Its collaboration with Piovan has enabled Selene to implement an effective interface between the company computer system and the extrusion lines, thanks to the use of Winfactory.

The system operates as follows. The data for the films to be produced - taken from customer orders - are booked into SAP. From this information, the system automatically sets up a production order and sends it to Winfactory; this assigns the production line and schedules production in relation to the overall sequence of orders. 

In practice, the company computer system determines the objectives and sends the order information to the Piovan system over the dedicated network. Winfactory checks the process parameters, ie. production time, processing stations, material percentages, batching, thickness and loading cycles. The entire process is thus set up automatically in line with the original job order.

When they installed their new line (the eleventh in the plant), Selene decided not to limit programming to the blenders, but to include the extrusion lines. In coordination with the supplier of the extrusion lines, a leading German company, Piovan developed the application for Winfactory to include the extrusion line parameters, so that the process be fully integrated and automated from raw material silo to roll of film.

The operator now only needs to select the order he wishes to run on screen, and start production. Winfactory already contains the optimal settings for the production line; programming is taken care of in advance, and there is no need for complex staff training.

Furthermore, Winfactory monitors and reports on consumption, roll weight, and all production cycles. The automation includes stocking information which has so far been entered manually at the warehouse. The process cycle is thus complete, and raw materials consumption is monitored for each individual production order.

Queue management

Winfactory not only controls, but also optimises the consumption of each raw material component. Managing job queues is instrumental in achieving this - the changeovers between production runs. This is handled in two ways. First of all, the automatic suction time setup: for each blending station, there is a matrix giving the optimal pipe suction and cleaning times; the receiver is completely filled, without leaving any material along the pipe. Secondly, the material feed is automatically adjusted, hence the blender station empties or stays full, depending on whether it is to be used in the next job order or not.

Winfactory knows in advance which stations will use the same material for successive orders and which ones require material changeovers.

Along with automation and automatic setup, Selene requested that wastage between production runs be reduced to a minimum. Previously, stations not in use had to be cleaned, and this led to significant wastage of materials. Winfactory takes successive orders into account and knows which materials will be used in them and which not. Before the next production run starts, the material feed to the stations which will no longer be used is ramped down: the changeover is thus done with those stations completely empty.

Monitoring and control

From the Selene control room, it is possible to see directly what is going on throughout the plant, starting from the extrusion line parameters. For each machine, there are over 1800 parameters, which are updated every 30 seconds. This data is stored, and can be called up when needed. Real time monitoring of production on each line allows the operator to know batch production times in advance and keep consumption under control. Simply weighing the roll - which is done anyway - is not sufficient for determining how long production will take; this can only be known by monitoring consumption in real time.

Film thickness is also monitored in real time, so that the measurements of each row of film remains within a specified tolerance. Finally, the power consumption of each line and the printing machines is monitored in real time.

Plant

Selene has eleven blown film extrusion lines. Each extruder is equipped with Piovan gravimetric blenders which collect the material from the raw material and additive distribution system pipes. A series of centralised vacuum pumps provide the suction that moves the materials.

The Piovan control panel provides integrated blending control, starting from the technical specification booked in the computer system which is automatically entered into the machine's settings along with the line settings and material recipe. Piovan distribution systems control the suction and send the raw materials and additives to the blenders. Selene has large outdoor silos for its most used materials, indoor silos for special materials and large storage bins for additives. The conveying system in equipped with automatic distribution stations, that select the material source automatically and delivers the right material to the extrusion line. Errors are thus completely eliminated.

Selene's most recently acquired line is to be used for detergent adhesive label film. This is a new and very complex application, with large consumption and stringent quality requirements. The system has been optimised for this type of production by the manufacturer.

Results

It is interesting to observe the technological development of Selene, that moved from a model of manual handling to a completely centralised and automatic solution. The plant is now fully organised, and the result is improved safety and product quality, along with reduced risk of film contamination, especially in relation to food safety, where Selene has to satisfy the entire range of European Regulations (1935/2004/CE, 2023/2006/CE (GMP), 10/2011/CE). Selene, as a manufacturer of food packaging, has to pay the closest attention to hygiene and safety issues. They have therefore implemented a hygiene self-control system based on risk assessments and control of potential contaminating materials and critical contamination points (HACCP) so as to minimise the risk of in-process contamination. The Winfactory system has given Selene significant management cost reductions, starting with the reduction of manual labour. Furthermore, the completely automated materials and additives handling gives certainty about production ingredients and equipment and improved safety and reliability in relation to finished product quality, with drastic reductions in human error. Above all, Selene has at its disposal the full range of data required for food safety certifications, since the process is fully tracked.

Remote assistance, i.e. the possibility of accessing the plant remotely via tablets or smartphones with security credentials, is another important component of Winfactory, ideal for quick troubleshooting of malfunctions. The device is equipped with a specific application linked to the company server. This function cannot be considered an accessory, but rather a fundamental component for real time production control, especially in such a highly evolved context.

Further developments may include optimisation of energy consumption and computerised tracking with barcodes of incoming raw materials and material batches, which is currently done with paper documentation. So many problems solved - and so many opportunities for improvement!

3 – Selene: products and applications

 

With its eleven three-layer blown film extrusion lines, Selene, established in 1958 and certified ISO 9001:2008 since 1994, produces polyethylene packaging film for FFS – Form Fill and Seal - industrial bags, printed and unprinted (50% of production), for stretch hoods, printed and unprinted (30% of production), for lamination (mainly for food industry applications) and sticky labels (20%).

The company is located in Lucca, and operates continuously 24 hours a days and seven days a week. In 2011, it manufactured around 20,000 tons of finished product, for a turnover of 50 million euro.

Export accounts for 50% of turnover, mainly to the European Union but also to the USA, Saudi Arabia, the Middle East and China. Applications go from plastic manufacturing, fertilisers, construction, domestic appliances, pet food/livestock feed, food additives, food, cosmetics and detergents. The material used is mainly polyethylene of various types (LDPE, LLDPE-C4/C6/C8, m-LLDPE, MDPE, HDPE, VLDPE, EVA), often with additives. Selene's main suppliers are the large producers of polyethylene including Exxon Mobil, LyondellBasell, Versalis and Dow Chemical, who are able to guarantee a constant high quality and are continually developing their compounds together with the client. The various formulations are developed by the R&D department in close collaboration with the customer. In some cases, the customer's specifications are used, and in others Selene technicians exploit their experience and analyses of samples of film to suggest the most suitable solutions. The company not only produces the extruded film, but also prints the film, on- or off-line.

Production waste is divided into printed and unprinted as part of the company's environmental safety policy. Unprinted film, divided by product category, is sent to a regeneration station equipped with a grinding mill and extruder for regranulation. This yields a high quality secondary raw material which is used in certain production runs. Printed film, on the other hand, is regranulated and sold for other applications.

Selene also has a cutting edge quality control and film characterisation laboratory. The laboratory measures the thickness of the film, its slipperiness, resistance to traction (dynamometer) and failure strength (Elmendorf, Dart Test), incoming material fluidity index, melting point (DSC), infrared absorption (IR/ATR), stratigraphy, hot and cold weld strength, and its optical properties and density.