Colour sensors reliably match car carpet sets

Automotive customers have absolute standards for colour matching carpet pieces and use of a colour sensor has substantially increased yields of perfect carpet sets and lowered scrap rate.

Tier One automotive supplier, Collins and Aikman (C and A), provides carpet sets to several major automotive manufacturers.

These carpet sets, manufactured in its Greenville, SC, Old Fort, and Farmville, North Carolina, USA locations The sets are made up of high quality carpet material.

As many as four vinyl wear pads are added to increase the durability of the carpet sets.

Each of these sets is available in carefully selected colours with all elements, carpet and padding, matching specific customer specifications.

Collins and Aikman, as part of its continuing quality improvement programme, decided to automate the colour matching process to assure colour match quality from sample to sample, and to eliminate mistakes in colour matching due to human error.

The problem, though, was one of finding a reliable colour sensor.

After trying various sensors, CandA Greenville came to Balluff.

C and A had tried colour sensors using fiber optic technology, which failed due to inadequate separation of sensor lenses.

Contrast sensors had also failed due to their inability to read colours off the carpet texture.

One of the major problems in reading true carpet colour is that due to handling, the nap or pile can lay differently from one piece of carpet to the next, which changes its perceived colour.

Balluff went to work on the problem under the direction of C and A's process engineer, Ted Manning.

Roger Altendorf, Balluff's photoelectric sensor specialist went on site to analyse the situation.

"The trick in this application was to accurately read and match colour from two completely different materials.

Different textures, materials, and nap angles dramatically complicated the problem, with the carpet material tending to display variable hue," said Altendorf.

After trying a number of possible sensors and process systems, the Balluff team chose the Balluff BFS 26K colour sensor as a basis for the final colour matching process.

Up to four Balluff sensors read the vinyl pads and two more read the carpet.

The BFS 26K carpet sensors were taught to recognise the carpet colour regardless of nap/pile orientation.

The full-colour Balluff sensor has three programmable outputs, which give it sufficient flexibility to be set up for 'go/no go' for all the colour variations C and A wanted.

* Solid fixturing - solid fixturing is key for any colour matching application.

The carpet must be read at precisely the right angle and precisely the right distance.

Set-up distance was not as critical on the vinyl wear pad colour match, but a specific sensing angle was still needed to correctly read all the colours.

The other key solution factor was that all elements in the process - sensors, carpet, and pads - had to be absolutely still for a split second.

The C and A team recognised this and devoted considerable effort to provide solid, protective fixtures for the Balluff sensors.

Manning said, "Our automotive customers have absolute standards when it comes to colour match on these carpet pieces.

Balluff has substantially increased our yields of perfect carpet sets, while simultaneously raising our productivity and lowering our scrap rate".

The success of Balluff's accurate colour matching solution led to a second application for Balluff's BFS 26K sensors.

C and A uses a water jet cutter to prepare the finished carpet assemblies for correct installation in specific vehicles.

Two Balluff BFS 26K sensors are now used in a final process check to make sure that only carpet sets that meet C and A's total quality parts criteria are cut for final installation.

Said Manning, "Quality and productivity is the name of the game when it comes to the automotive industry.

Balluff gave us the means of simultaneously increasing our quality and our productivity to more than meet the requirements of our automotive customers when it came to this particular production process.

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