Industry : Manufacturing

Category : Turn-key solution

The Challenge:

To develop a machine vision system capable of identifying defects such as missing leads, lead offset, misalignment of slats in pencils and sorting them

The requirements also included:
• High speed inspection - About 21 pencils per second or 2 million pencils per day
• Sorting of pencils into different bins based on the defects
• Handle variations in wood types, textures and lead colors

Technology :

Hardware : Soliton FireWire Cameras M241_CFW03, Pneumatic ejectors, Encoders, PXI/Compact PCI, Data acquisition /control card-PCI 6025, Microcontroller-AT89c52, LED Strobe Light Controller-SCTLR-01, LED Strobe Light(Bar Type)-LSL12BW-120, LED Strobe Light(Ring Type)-LSL24RW-120
Software  : LabVIEW, IMAQ Vision

The Solution:

Soliton developed a high speed pencil sorting system using LabVIEW and the digital image acquisition hardware. The system design involved the use of two Soliton FireWire color cameras of VGA resolution for high speed image acquisition. The cameras focus at the two opposite ends of the pencil. High intensity lights are required for a very short integration time, of about 100us, and hence the halogen based fibre optic lamps were used in the system. The images then acquired from both the cameras are processed by the application software running in the PC and based on the defect definitions, the images are classified as either good or bad. A high-speed synchronization circuit using a microcontroller was designed for the precise ejection of the defective pencils

Recent Upgrades:

The initial system was designed using the halogen based fibre optic lights. The 24*7 operation of the system at very high intensities caused a significant deterioration in performance of the lights over time and hence these had to be replaced frequently. In order to tackle this issue, Soliton came up with the idea of replacing the halogen based fibre optic lights with LED lights. Soliton's expertise in manufacturing LED lights for OEMs helped to quickly develop customized lights with strobing capabilities for the new systems

Soliton's LED lights provided significant benefits over the previous halogen based fibre optic lights:
1. The LED lights helped to save power by a 100 times when compared to the halogen lights.
2. The performance of the LED lights would be uniform over years
3. Strobing helped to get the required intensity for capturing good quality images using the system
4. Strobing would help increase the life of the LED lights which in turn would have a significant impact on the costs involved in operating the systems

Engineering Challenges:

• Flexibility - The quality expectations varied for different grades of pencils and hence the system had to be flexible enough to allow the user to set up the machine accordingly
• Synchronization - Synchronizing the different ejectors served to be a major challenge
• 13 Color options – The system had to be designed to sort up to 13 different colors of pencils

Value Addition :

• Quality - The system provided a very high quality of sort with a resolution of 30 microns
• Statistical analysis - The statistical details on the various defects collected by the system enabled the problems in the raw materials and the upstream processes to be curbed at the source
• Complete automation - Completely automated data collection and report generation
• Quick Setup – The system allowed the user to change the set up for a different color of pencils within a second.

Commendation :

The application was one of the finalists under the Discrete Manufacturing/Process Control category for the NI Week Best Application contest
http://sine.ni.com/cs/app/doc/p/id/cs-457

Watch the high speed pencil sorting video here