SPC chart for in-process inspection

[Former Member]

Hi all,

I am trying to create an SPC chart for in-process inspection, so after assigning MIC in routing it asks for sampling procedure and SPC criterion.

I have created a test sample procedure and assigned to MIC and while assigning SPC criterion it gives an error. I have tried using different option available in SPC criterion in routing. I created defect type and the different defects falling under particular defects and in MIC's control indicator i selected defect recording radio button.

Now i am confused whether SPC or control charts can be used for in-process inspection or  only for post production i.e. inspection plan..?

attached documents indicates the sampling procedure, routing and error. Please help me for this error

[Former Member]

Hi Santosh

You have not mentioned screen shot for sampling procedure & i can not see error message in screen shot.

However it very much possible to use control chart for in process inspection. I am attaching some screen shots from my system to help you

Please reward points if helpful

Singh Parminder

[Former Member]

Hi Parminder,

Thank you very much for the detailed description.

Still i have a doubt, if i am using a Qualitative MIC and i only want to record defects, so i have maintained catalog 9 in QS41, selected sets cannot be done for defects and for that MIC i have not tick characteristics attributes in control indicators...till here am i right..?

In routing i selected 150 as an inspection point and for operation 150 when i assign sampling procedure and SPC criterion it shows an error. screen shot is attached

[Former Member]

Hi Santosh

Operationaly SPC chart is of no use for qualitative characteristics. as there is not much statics & limits included in qualitative characteristics.

Bu you can try to use it, I am not sure what kind of graph it will put. In you example please check which control chart you are using in sampling procedure, try to use control chart 195.

However i recommend to use SPC only for quantitative charahteristics.

Singh Parminder

[Martin_H]

What do you expect do be shown on a shewhart chart if you would use a qualitative characteristic???

MH

[Former Member]

Hi Martin,

I made some MIC's as a defects i.e. user will record results only for defects.

I made sampling procedure with fixed sample, valuation as SPC and control chart type as 111 shewhart chart for x bar/ samples. when i assign these sampling procedure and SPC criterion in throws an error.

I have made these MIC's as an Qualitative, and time period as 1 hour in operation. I want to show these defects on the graphs.

So which control chart should i use..? am i following the right method..? please guide me if am wrong

[Martin_H]

Hi,

you should first inform yourself about what SPC is about, e.g. what is a shewhart chart and how/when it is used. Then you will find out if it makes sense (and is possible at all) to draw a control chart based on a qualitative characteristic.

Regards

MH

[Former Member]

Thank you Martin and Parminder..i got your point.

But one confusion, suppose i have maintained quantitative characteristics as a MIC's and in 1st inspection lot i recorded 14 defects and in 2nd inspection lot i recorded 8 defects.

So is there any method to get combined graphs..? i mean combination of 1st and 2nd inspection lot..?

[Martin_H]

Please check some QM method pages on SPC, your last comment shows that you did not research the concept of SPC completely. Try to understand it without SAP system first.

MH