We have a print requirement to maintain a cpk of 1.67 on a certain dimension. It is very difficult to achieve. We need to figure out the best way to set up and monitor the measurement.
The part is a drawn stamped cup and the dimension is the outside diameter - lets say 2.500 p/m .002. We'll run maybe 5,000 to 10,000 pcs. each batch. Right now, we set a target dimension of p/m .0012. So we set the die up and adjust until we reach inside that target -- easier said than done. Generally, once it is set, it stays at that dimension with minimal variation.
So I am trying to figure out the best way to create the spc chart and calculate the cpk for each batch. If we wait until the end of the run we may have a batch that doesn't meet the cpk -- and creates a whole mess of other problems. So I am thinking of taking 20 samples from the first 100 pcs. to start the initial calculation. Then adding like 5 samples per hour or something until the end of the run to monitor. So we will probably end up with 30 to 50 sample measurements total.
Thoughts? Thanks in advance.
The part is a drawn stamped cup and the dimension is the outside diameter - lets say 2.500 p/m .002. We'll run maybe 5,000 to 10,000 pcs. each batch. Right now, we set a target dimension of p/m .0012. So we set the die up and adjust until we reach inside that target -- easier said than done. Generally, once it is set, it stays at that dimension with minimal variation.
So I am trying to figure out the best way to create the spc chart and calculate the cpk for each batch. If we wait until the end of the run we may have a batch that doesn't meet the cpk -- and creates a whole mess of other problems. So I am thinking of taking 20 samples from the first 100 pcs. to start the initial calculation. Then adding like 5 samples per hour or something until the end of the run to monitor. So we will probably end up with 30 to 50 sample measurements total.
Thoughts? Thanks in advance.
