Quality control of Clairol Nice 'n Easy hair colorant kits, packed in cartons at Procter & Gamble's Seaton Delaval site near Newcastle, U.K., has been automated with a new custom-built checkweigher from OCS Checkweighers. The machine not only ensures that weight is correct, confirming the presence of three plastic bottles of liquid, but is also equipped to operate under minimal supervision, simultaneously checking for cartons with open flaps.
Previously, cartons were taken off line at random for manual inspection, a time-consuming process unable to uncover and reject any consecutive errors, possibly as a result of a filling machine fault. Now, with each carton individually assessed, further progress has been made towards Procter & Gamble's objective of 100 percent quality assurance.
P&G set its own specifications for the machine, which is based on an OCS HC-2000-2 model but includes an infeed conveyor with top and bottom belts, carton open flap detection, rejection verification and a level warning on the reject bin that allows the line to run continuously.
"The specification, rather than price, was the most important factor to meet," explains Gordon Fellows, project delivery engineer at the Seaton Delaval site. "OCS Checkweighers listened and quoted for the system we needed rather than others who suggested a standard offering. As a result, we got what we want, and the installation is performing well."
Cartons are rectangular and are fed from the cartoning machine to the checkweigher lying flat, long edge leading by a side-belt conveyor. This allows the checkweigher's top and bottom belt infeed conveyor to overlap the side-belt conveyor, ensuring that the cartons are positively controlled and accelerated at the correct pitch to the weigh platform.
Photocells immediately above the checkweigher infeed inform the machine of any unclosed carton flaps, inhibiting the checkweighing process and triggering the reject system to eject that particular carton. Cartons rejected for open flaps are listed separately in the production statistics gathered by the checkweigher, but held with other rejects in a common bin.
The optical controls are also able to inform the machine of any cartons that have become skewed and are not held square between the belts. These are also rejected to avoid any risk of a weighing error from an incorrect product length and to make sure products are presented correctly for the next process in the production line.
With the Clairol line designed to run under minimum operator supervision, the checkweigher's reject system itself has to be controlled and monitored on a fail-safe basis.
Therefore, the air supply is continuously monitored and the line stopped if pressure drops below the level at which there is sufficient power in the airblast to guarantee proper operation.
Rejection of the faulty pack is also positively confirmed on a shift register to ensure that only good products go forward to the next level of packaging. In addition, the reject bin is fitted with a fill-level sensor that provides a visible warning when three-quarters full, allowing an operator time to reach the machine and empty the bin before complete control of all rejects is compromised.
Once this warning is given, software in the controls, programmed to P&G's specifications, counts the number of further rejects and will stop the line automatically when the number reaches the maximum set for bin capacity. An error message appears on screen and the line can only be restarted when the operator confirms that he or she has emptied the reject bin and reset the checkweigher.
OCS also has equipped the checkweigher to automatically record all operating events and data such as speeds, throughput, actual weights and number of rejects for use in statistical reviews. A USB port allows the data collected to be downloaded to a memory stick. Overall, with a move to automatic quality control of Clairol cartons, P&G's principal need was a system that offered inherent dependability and minimum supervision.
This has been achieved, says Fellows: "The OCS machine has given us reliability in quality assurance and, in particular the open flap detection and self-calibrating auto tare are very much appreciated. Although this was only a small project, it is still a job well-done."
OCS Checkweighers Ltd., 678-344-8300. www.ocs-cw.com