A custom EPIC defect inspection system finds defects as small as 30 microns on 2 inch parts on a high speed line (600 parts per minute). Correctly identifying these defects at a highly repeatable rate for hundreds of products a minute allowed the manufacturer to eliminate a mandatory three-day product hold for all products, drastically reduce scrap product, and improve the facilities predictive maintenance capabilities while simultaneously reducing maintenance staff workload.
Challenging Production Environment with a High Cost Quality Problem
The production process for this product presented several challenges to the plant operations staff and for an automated quality assurance solution:
- Products were moved down the line using a high-force method of transport, which causes lots of vibration and unpredictable movements
- A high scrap rate was caused by the challenging process of assembling the product correctly
- A precise amount of force must be applied to properly assemble the end-product. If too little force is used the product can leak and become ineffective within hours or days. If too much force is applied, the product can deform. Machine parts quickly wear down from this repetitive assembly action and start applying different amounts of force based on their wear. Defects during this part of the process were common and caused much scrap.
- In addition, if a leaky product is packaged next to other products, it can ruin the products around it, which was also common
- Quality was only manually checked every few hours, so if a machine part started causing defects it could output hundreds or thousands of bad product before the error was corrected.
- Many of the defects were very small and leaks could be invisible to the human eye. For this reason, all product was being held on the warehouse floor for three days before shipment to allow leakage or defects to become more apparent. The product was then retested, resorted, and finally shipped.
- A previous attempt at automated quality inspection (not by EPIC) had been quickly damaged by the manufacturing conditions, when force from the line ripped several critical parts off the system.
- Parts were small (several inches max) and moving very quickly down the line (up to 600 parts per minute), and damaging defects were often invisible to the naked eye
Eliminating Scrap and Delivering Confidence in Product Quality
Using EPIC’s dedicated vision lab and design-build process, our engineers were able to design a custom solution designed to endure the harsh manufacturing conditions and deliver reliable, repeatable, accurate inspection results for defects as small as 30 microns. Capturing high quality images of every product, every time, is key to this, and how well designed the system is directly effects it’s ability to deliver reliable results over time. The process for delivering successful vision solutions begins with finding a system design that is:
As simple as possible from a programming standpoint. This reduces the chances that mistakes or conflicts in coding will cause the inspection to fail over time.
- High contrast – being able to see the defect you are inspecting at a high contrast every time means that you can accurately identify defects and get a highly reliable inspection. Poor lighting, poor contrast, or poor fields of view often cause automated inspection system failures, especially for unpredictably sized defects.
- Calibrated correctly for field of view and resolution – accurately measuring very small defects does not simply require a high resolution camera. Image quality will determine inspection quality, so having an appropriately sized field of view that still allows you to see defects clearly in a picture is critical. Many inspections make the mistake of having too large of a field of view, degrading image quality and missing blurred or “un-seeable” defects in the image.
- Identifying all the angles and inspections that need to be performed – this is where our vision lab truly helps. By simulating line conditions, including high line speeds, we can determine how many angles need to be covered, how many cameras, how many images to capture per product, etc. in order to provide an accurate inspection that finds all relevant defects.
- Custom made for unique production line conditions – Our vision systems usually come mounted on high-quality custom fabricated stands that do not touch the conveyors or other equipment and allow for few or no adjustments by operators so that the system is not effected by line vibrations and cannot be tweaked out of alignment once on the plant floor. In addition, these custom fabricated stands protect cameras and lights from dust, ambient light interference, and other plant-specific challenges.
- Seamlessly integrated into your line controls – this means minimal work for line operators at product turnover, as the vision system will automatically know when SKU’s change. In addition, alarms, scrap rates, and predictive maintenance capabilities can be layered into to existing plant controls and reporting systems giving you full, real-time visibility into what is happening on the line and providing optional automated process control.
For this particular application, EPIC designed a solution that:
- Came on custom vision system stands designed to avoid the vibrations and random forceful movements on the line that caused the previous (not EPIC) quality inspection system to fail
- Included backlighting for the products as the came into the systems field of view for higher contrast imaging
- Measured the diameter of the product, and the diameter of both ends of the product to check for malformation and dents or mismatched parts
- Inspected the surface of the product for defects as small as 30 microns in diameter
- Sounded an alarm as a cautionary warning when several defects in a row were detected and pinpointed the likely machine part causing them.
- Automatically logged defects and inspection results and alarms with key information (date, time, location, etc.)
The solution was tested and designed in our vision lab, then the full scale system was tested both before shipment and at arrival upon the plant floor. EPIC integrated the automated vision system into the existing plant controls, trained line operators and verified correct startup and commissioning before turning the system over.
Better Products, Lower Costs, Faster Shipping
The system was installed several years ago and is still operating reliably today. The impact of getting a reliable, automated quality assurance system included:
- Elimination of the mandatory three day hold and retesting of all products before shipment, which eliminated most “work-in-progress” inventory sitting on the plant floor and improved just-in-time product delivery
- A drastic reduction in scrap rate by catching repeated failures within a few products, alerting maintenance to line issues much faster, and preventing bad products from ruining good ones through leakage from hard-to-see defects
- A significant reduction in operational expenses for raw materials, manual QA inspections, and parts replacement
- Allowed for active troubleshooting and predictive maintenance while improving information for operators on which specific machining parts were causing defects for fast correction
- Speed up maintenance and make it more accurate