Blown Film Thickness Measurement

NDC have supplied web gauging systems to the blown film industry for over 45 years. Its latest NDC 8110-BF system provides a fully functional web gauging platform for today’s competitive blown film market. There are two measurement configurations available from NDC, the choice of which largely depends on the type of product made.

The first measurement configuration is best suited to the commodity product market. It utilizes NDC's GBS (Gamma Backscatter) gauge for measuring the blown film thickness directly on the bubble, close to the die. Unlike competitive capacitance gauges, NDC's GBS gauge is insensitive to the film composition, ambient temperature and humidity, making it ideal for measuring the total thickness of products such as single layer and basic multilayer films.

For multi-layer products, NDC offers a unique blown film system configuration that measures the product on the layflat following the collapser. The significance of this approach is its ability to quickly determine the profile shape, the average web thickness and also critical product components such as the thickness of barrier layers like EVOH and Nylon. Typically this is accomplished in four scans or less, which provides responsive measurement, excellent process visibility and exceptional product quality. In order to achieve fast measurement and tighter control response, a MiniTrakTM O-Frame scanner is installed following the collapser that measures the double layflat film thickness with an FG710S infrared gauge. This gauge provides co-extrusion thickness measurement for up to 4 components and component-specific control for product quality assurance and cost savings.

This advanced blown film system incorporates three key features that provide significant performance benefits compared to conventional blown film configurations which simply measure the thickness of the film on the bubble. They are:

High-Speed Near Infrared Barrier Component Measurement
NDC is the industry leader for infrared measurement of coextruded structures. The flagship product in this line is the FG710, which can measure both the total film thickness and also critical coextrusion components such as EVOH and Nylon content in the film structure.

Double Layflat Separation Algorithm (DLSA)
The system measures the double layflat film with a proprietary algorithm which mathematically separates the top and bottom film layers to provide a continuous, full-width single layer thickness profile. The DLSA algorithm also includes Accumulator Modeling and Die Rotation Modeling that accurately maps the film against the die positions.

The DLSA uses the following elements as part of its control algorithm:

  • Hauloff position
  • Hauloff speed
  • Hauloff direction of travel
  • Bubble twist angle
  • Diebolt positions

Automatic Profile Control (APC)

The APC control supervises the die bolt positions based on the DLSA profile measurement. The control also includes a ‘smart’ pulse alignment profile map.

In summary, NDC's blown film solutions provide the following benefits: 

  • Improve product quality
  • Maximize product yield
  • Minimize production costs
  • Minimize scrap
  • Optimize the process
  • Reduce downtime
  • Shorter start-up time
  • Save on raw materials

 

NDC Blown Film Web Gauging Layflat thickness Measurement and Control System

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