Pinhole detection vital to protect packaging barrier

The Hawkeye Pinhole Detector monitors the metallising process by opacity measurement and defect detection to ensure consistent product quality.

It is located inside the vacuum chamber after the deposition head and measures the optical properties of the film every 25mm instead of the conventional 100mm pitching.

This enables measurements over and between boat positions, and offers full width metallised film inspection based on the optimised optics developed.

Bobst uses standard aluminium metallising machines as the basis for clear barrier coating.

This permits flexible processing of films including PET, BOPP, CPP and PLA.

The coated films are used in products such as baked goods and microwaveable products.

Detection limits​

Nick Copeland, R&D director Bobst Manchester, told FoodProductionDaily.com that it offers defect detection of 100 micron defect at 1000m/min.

“If defects are not detected and rectified during the metallising process sub-standard material is produced which could outside the acceptable levels required for the application.​

“As Hawkeye provides in-line, in vacuum opacity measurement and defect detection it detects defects including pin holes and practically with operator intervention the cause of the defects can be eliminated prior to producing several rolls of sub-standard material.”​

He said Bobst Manchester has demonstrated that defects such as pin holes can affect the barrier performance of the coated material and the associated shelf life of flexible food packaging.

Real time inspection​

In line in vacuum real time inspection of the metallised film can help to highlight product of defect levels which will affect the barrier performance of the coated film, said Copeland.

“Generally speaking for metallised film the issue of metalliser induced defects are related to spitting of the evaporator boats, which are running at the wrong temperature,” ​he said.

“Detection of the defects enables the operator to inspect the boat condition and rectify the issue via boat temperature adjustment. This methodology also enables defect density assessment to be used to determine if the evaporator boats need to be changed.”​  

BOBST Technology Centers in the UK, Germany and Italy hosted Open House events at the same time as the trade show in Dusseldorf.

They showcased the General K5000 vaccum metalliser, gravure printing with the Rotomec 4003MP and developments for improving print quality, operator ergonomics and machine availability in flexo printing at K Show.