Dear All,
I'm facing problems with establishing SPC in my production processes.
The production process has few sub-processes. Firstly one machine is feed with steel and make around 300 kg of sub-product. Then it goes to another machine that make some grinding, then it goes to furnace for heat treatment. Then few other machines that do different types of grinding. Batch created on the beginning of the process will go through it and finish as one batch also. Parts are small therefore in 300 kg I can have up to 400 000 parts.
Let's consider heat treatment. I take 5 samples of every batch and measure hardness with Rockwell hardness tester.
I tried Average and Range Control Chart but I have a lot of points out of CLs. This is because I have very small variation withing subgroups (short-term variation, part-to-part within the batch). Small Range -> tight Control Limits.
In my case batch-to-batch variation is significantly greater.
Now I know that this in not apropriate type of control chart. What do you suggest to try next?
I'm facing problems with establishing SPC in my production processes.
The production process has few sub-processes. Firstly one machine is feed with steel and make around 300 kg of sub-product. Then it goes to another machine that make some grinding, then it goes to furnace for heat treatment. Then few other machines that do different types of grinding. Batch created on the beginning of the process will go through it and finish as one batch also. Parts are small therefore in 300 kg I can have up to 400 000 parts.
Let's consider heat treatment. I take 5 samples of every batch and measure hardness with Rockwell hardness tester.
I tried Average and Range Control Chart but I have a lot of points out of CLs. This is because I have very small variation withing subgroups (short-term variation, part-to-part within the batch). Small Range -> tight Control Limits.
In my case batch-to-batch variation is significantly greater.
Now I know that this in not apropriate type of control chart. What do you suggest to try next?