J
Jat999
Hi all
First post and relatively newbie to properly understanding SPC. I hope I am using the correct forum.
I am trying to establish whether a new filling machine is capable to deliver consistent weights across a varying range of different weights and filling materials. The company I work for makes food ingredients and under uk law, has to conform to average weight legislation. Obviously as a business, we need to operate as close as we can to target weight and not be giving away too much to our customers.
The machine in question is a twin head filler. There are inbuilt weigh heads measuring eac deposit. I am able to capture eac weight from each weigh-head.
The material types range from very small sugar balls to small fudge cubes, the jar sizes range from 60grams to 500 grams.
In terms of data captured already, (I have 100’s of sequential data elements), for each weigh head, I am calculating the mean, the SD, the UCL, LCL and I have calculated the CP and CPk.
Where I am struggling is around understanding the outputs.
One head seems to be much more in control than the other. The control limits are closer and operating closer to the target, yet for both heads, the CP and CPk are the same, both values for both heads =1.
I believe my questions are
1. Am I approaching this correctly?
2. Is it possible to have CP and CPk for both to = 1 yet have very different control limit spread?
3. Are there any resources that may help me understand better the application I am trying?
Apologies for the long rambling questions, I do believe SPC is the correct methodology, I need to establish whether there really is capability and importantly, repeatability, in the machine over a wide range of materials before we let the machine supplier leave.
I am happy to share the spreadsheet I am using to show sample output.
John
Edit - Spreadsheet added
First post and relatively newbie to properly understanding SPC. I hope I am using the correct forum.
I am trying to establish whether a new filling machine is capable to deliver consistent weights across a varying range of different weights and filling materials. The company I work for makes food ingredients and under uk law, has to conform to average weight legislation. Obviously as a business, we need to operate as close as we can to target weight and not be giving away too much to our customers.
The machine in question is a twin head filler. There are inbuilt weigh heads measuring eac deposit. I am able to capture eac weight from each weigh-head.
The material types range from very small sugar balls to small fudge cubes, the jar sizes range from 60grams to 500 grams.
In terms of data captured already, (I have 100’s of sequential data elements), for each weigh head, I am calculating the mean, the SD, the UCL, LCL and I have calculated the CP and CPk.
Where I am struggling is around understanding the outputs.
One head seems to be much more in control than the other. The control limits are closer and operating closer to the target, yet for both heads, the CP and CPk are the same, both values for both heads =1.
I believe my questions are
1. Am I approaching this correctly?
2. Is it possible to have CP and CPk for both to = 1 yet have very different control limit spread?
3. Are there any resources that may help me understand better the application I am trying?
Apologies for the long rambling questions, I do believe SPC is the correct methodology, I need to establish whether there really is capability and importantly, repeatability, in the machine over a wide range of materials before we let the machine supplier leave.
I am happy to share the spreadsheet I am using to show sample output.
John
Edit - Spreadsheet added
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