My company produces extrusion laminated flexible packaging material that is mostly used to package food and pharmaceutical products. This the paper/poly/foil material used to make pouches for many of the products you might see in a grocery store. The illustration below is a basic representation of the process. Typically an outer barrier layer and an interior heat-sealable layer are bonded together with a layer of molten extruded plastic. Bond between these layers is critical to product performance.
Our complaints and returns data shows a growing number of issues related to delamination and poor bond between layers of our material, and so I’m leading an improvement effort to improve this trend. After analysis of the issue data, one of the many projects we decided to launch is to verify with a Gage R&R that we can actually trust the data coming from our lab. We currently don’t use SPC, and simply calibrate our instruments and trust the data. This is convenient, but probably not helping us. We could be calling good parts bad and bad parts good, and making process adjustments based on inaccurate date.
One of the most important tests we do, and want to ensure we can trust, is a Bond Test based on ASTM F 904. This test involves cutting a 1” wide strip of test material, mechanically or chemically separating specific layers on one end, mounting in a tensile tester, and then measuring the average force required to pull the layers apart for 2” after the first 1”. Our specification tolerance is one sided, a minimum (ex: 400gm/in).
Our laminated material is produced in large rolls, typically 60”wide, 40”dia, and may have 20,000 linear feet of material on a roll. These rolls come off a large extrusion laminator at a rate of approximately 1 every 20-30 minutes. We may produce 10 rolls of one specification in a typical job order, and may not run that job again for months; if ever.
For every roll we produce, we roll up about 6’ of material from the top of the finished roll (roll-up sample) and send to the lab for testing as soon as it is produced. For Bond Testing we will typically cut three strips as shown. Properties of the finished material tend to very across the web, and are more homogenous along the machine direction.
I’ve got Minitab set up, I’ve read all I could here on the Cove, elsewhere on the web, and even read a copy of the AIAG MSA Manual, but I’ve still got questions. We have 3 operators, and one testing machine. I should be able to cut as many test pieces as I need from each roll-up sample, and can get 5-10 roll up samples for a Job Order, but I can’t get many different Job Orders (Batches) because we run them so infrequently.
Sorry if all the background info is too much. Below are my specific questions. Thanks in advance for any advice!
Our complaints and returns data shows a growing number of issues related to delamination and poor bond between layers of our material, and so I’m leading an improvement effort to improve this trend. After analysis of the issue data, one of the many projects we decided to launch is to verify with a Gage R&R that we can actually trust the data coming from our lab. We currently don’t use SPC, and simply calibrate our instruments and trust the data. This is convenient, but probably not helping us. We could be calling good parts bad and bad parts good, and making process adjustments based on inaccurate date.
One of the most important tests we do, and want to ensure we can trust, is a Bond Test based on ASTM F 904. This test involves cutting a 1” wide strip of test material, mechanically or chemically separating specific layers on one end, mounting in a tensile tester, and then measuring the average force required to pull the layers apart for 2” after the first 1”. Our specification tolerance is one sided, a minimum (ex: 400gm/in).
Our laminated material is produced in large rolls, typically 60”wide, 40”dia, and may have 20,000 linear feet of material on a roll. These rolls come off a large extrusion laminator at a rate of approximately 1 every 20-30 minutes. We may produce 10 rolls of one specification in a typical job order, and may not run that job again for months; if ever.
For every roll we produce, we roll up about 6’ of material from the top of the finished roll (roll-up sample) and send to the lab for testing as soon as it is produced. For Bond Testing we will typically cut three strips as shown. Properties of the finished material tend to very across the web, and are more homogenous along the machine direction.
I’ve got Minitab set up, I’ve read all I could here on the Cove, elsewhere on the web, and even read a copy of the AIAG MSA Manual, but I’ve still got questions. We have 3 operators, and one testing machine. I should be able to cut as many test pieces as I need from each roll-up sample, and can get 5-10 roll up samples for a Job Order, but I can’t get many different Job Orders (Batches) because we run them so infrequently.
Sorry if all the background info is too much. Below are my specific questions. Thanks in advance for any advice!
- What is a Batch, what is a Part, and how many do I need? If I make 10 rolls in one Job Order, is that entire Job Order (all 10 rolls) considered a batch or is each roll a batch? Is each roll considered a part or are the test pieces cut from each roll the parts? Can I use test pieces (Parts) from only one Job Order (Batch)? If not, how many batches are needed? If indeed each Job Order is a Batch, and many batches are required, then I may need years to collect enough samples since we have a long time between running the same job.
- What is my Number of Replicates? Assuming that each test piece is a part, and it is a destructive test, how can I test more than once? Minitab says I must have at least 2 replicates.
- How can I assume that all parts within a single batch are identical - Because I’m doing destructive testing, I’ve read that I must be able to assume that all parts within a single batch are identical enough to claim that they are the same part. How do I know I can make this assumption? What basis do I have? How identical is identical enough? If I’m unable to make this assumption then part-to-part variation within a batch will mask the measurement system variation. I’ve also read that I need to ensure that I select parts that represent the actual or expected range of process variation. If all parts are identical, then how can they represent a range of process variation?
- Which method: Crossed, or Nested? According to Minitab choosing between a crossed or nested Gage R&R Study depends on how my measurement process is set up. If all operators measure parts from each batch, then use Gage R&R Study (Crossed). If each batch is only measured by a single operator, then you use Gage R&R Study (Nested). If I only test parts from one batch, and I have 3 operators, then all operators measure parts from that batch and I use Crossed. Is this correct? I’ve also read that you have to use Nested for Destructive Testing because each part is only measured by 1 operator. So which to use; Nested or Crossed?
