Behind the curtain of automated inspection

AS A rule of thumb, Vadain estimates that an average roll of fabric may contain a maximum of five defects, such as weaving errors or stains. In the best case, a fabric supplier has already marked the flaws in the roll. However, the responsibility for detecting and processing the defects is passed on to Vadain.

To prevent any defects, several checks are made between the receipt of goods and dispatching the finished product. The first check takes place when the material arrives and is stored in the warehouse. More checks are carried out prior to production and at the workshop before production, as well as a final quality check of the finished product before shipment. The inspection was done manually, by unrolling and rolling the fabric over light boxes.

While rolling, an employee visually checks for errors in the fabric – a very time-consuming and inefficient procedure, which can only be carried out by an employee for a short time with full attention.

Solution with machine vision

Seeking a more efficient, faster way to inspect the fabrics, Vadain presented the challenge to Sycade, which specialises in quality improvement through automation in the manufacturing industry. Sycade proposed a concept to automate the inspection process with a machine vision solution. The solution performs checks faster and more accurately, reduces complaints and cutting loss (which occurs when the roll are cut for production) and ultimately results in cost savings.

With the expertise of Vadain, the technology and innovative automation concept of OMRON, hardware of Eisenkolb and (camera light supplier), Sycade set up a solution using a 'standard' rolling machine to unroll rolls from position A, and roll up again to position B. The unrolled fabric passes over an assessment surface with an integrated cutting unit, located inside a dark unit with vision technology.

The lighting and camera inspection system can detect even the smallest deviations in substances, thanks to intelligent custom software from Sycade and 'customised' standard hardware from OMRON. However, it is not enough to simply find a fault in a roll of fabric. Fabrics are not all equally thick or transparent, and they come with different weave structures, colors and reflection. The correct light and camera adjustments and programming settings were discovered after a series of tests.

Detect, cut, register

What needs to be done when a defect is detected and assessed? In the case of dust, it can be removed by the operator and the machine receives a signal that it can pass. In the event of a stain or weaving error, the machine has already identified the location of the defect. The machine has also already measured how much fabric has been unrolled up to the defect. After cutting from the correct location, this partial roll is marked with a sticker with the parent roll plus partial roll marking, including the number of meters. This makes it possible to have an overview of how many meters of flawless fabric is in stock and in which cuts. This ensures that the workshop knows exactly which partial—and error free—roll can be used most efficiently for a particular order. In the administration, the total of the sub-rolls remains linked to the original meters of the parent roll, making it easy and efficient to reorder fabrics.

Thanks to the solution, pick-up and return movements in the warehouse have been halved. As the partial rolls are now all precisely measured, registered and pre-cut, complete rolls no longer need to be picked up, cut and returned to the warehouse. This saves 50% in the loading and unloading time and reduced transport movements between the racks improving safety.

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