100% inspection system work flows
When manufacturing discrete items like boxes of biscuits, pharmaceutical products, cans and bottles there has always been the capability to inspect and reject. When operating in a roll to roll process the challenges are quite different. It is not always possible to stop the line so when a defect is detected it will continue to the rewind and become part of the product to be shipped. What do I do then?
The common approach is to mark the edge of the web or apply a tag as shown below. This works well and an operator in a converting department can then stop and cut the waste out. That is one form of smart converting
100% inspection systems detect many defects
Anyone that has used a 100% automated inspection system understands that there are many more defects detected than what operators would have once seen and tagged for rework. The image below shows a graphical roll map of a plastic roll of material 1800m in length and 1.4m wide. There were close to 2,300 issues with the roll.
In this case the user only wanted to mark holes, so it was easy for the inspection system to classify the defect and automate the slitter to stop and ignore the other 2200 issues. There were over 200 instances of contamination. If a tag was to be inserted for each instance, the end result would be a telescoped roll that looked like a hedgehog with many tags.
So how to optimize slits without tagging each defect
So if an inspection system is installed on a slitter to inspect material prior to shipping, then it can be considered a quality control device. If installed on the process that produces the defects then it can be considered a process control device providing early warning and allowing the operator to stop further issues. If you add the ability to track defects from the upstream process to the converting department you now have process control and a quality management system in place. This could also be referred to as smart converting. Machine vision systems enable this process.
There are a number of requirements to smart converting:
- Storage of defect images and statistics to enable a review.
- Classification of defects.
- Software to filter defects.
- Synchronisation method so as to stop slitter at correct position.
- Composite view of all quality data including web gauge data
The image below shows a snapshot from RQMS Express screen to allow an operator view all data and devise a strategy to control a rewinder and automate the waste management. It should also be possible to isolate defects according to the expected location by generating expected roll maps according to a slit strategy. So if the rejectable defects are to be found in the second child roll on slit 4, then that roll can be isolated and doctored and the rest shipped without concerns. Synchromization can be achieved by zeroing out on an event or using barcoded tags every say 300m on the roll, and read that tag and locate it in the database.
In summary there are a number of approaches to implementing smart converting processes using 100% inspection data. OneBoxVision's advice is to choose the approach that fits best to your process and resources. Feel free to contact OneBoxVision to get a free consult. Follow the link below to download an overview on RQMS Express and composite mapping.