SPC (Statistical Process Control) on Go/No-Go Checks

Batguy

Registered
This may have been covered before, but I was unable to find reference to the topic. We are further implementing SPC on the shop floor and have come across an issue. What data, if any, is actually collected for a "Go/No-Go" check (i.e. internal thread gage, go/no-go pins on a bore). Just collecting "Go" and "No-Go" from the operators does give us historical data of the run, but that's about it.

My question to the forum members; "How have you addressed the collection and charting of 'attribute' or 'Go/No-Go data'" Especially the collection of such data...just have the operator mark "Go" or "no Go" for each part he checks?

Thanks in advance!
 
Last edited:
R

ralphsulser

SPC tools for no/no-go are "P" charts-percent defective, or "C" charts defects per unit if checking more than one hole on a single part.
The are part ot he "7 quality tools" along with X bar & R, Cause & Effect, Scatter diagrams,etc.
 
W

world quality

With a little mod and changing you can use this sample:

1. What size pins, etc are you using and remodify as required.
 

Attachments

  • Sample Att Gage R&R.xls
    86.5 KB · Views: 670
E

Effocus

My question to the forum members; "How have you addressed the collection and charting of 'attribute' or 'Go/No-Go data'" Especially the collection of such data...just have the operator mark "Go" or "no Go" for each part he checks?

Thanks in advance!

I would recommend you to read the SPC Manual from IAIG (Automobile industry) - in that it's very clearly explain how you can use such SPC.

Be careful on the conditions to apply for each chart p, np or c or u charts

:popcorn:
 
O

oleg_volf

SPC tools for no/no-go are "P" charts-percent defective, or "C" charts defects per unit if checking more than one hole on a single part.
The are part ot he "7 quality tools" along with X bar & R, Cause & Effect, Scatter diagrams,etc.
Hello


I have one question.
In my machining center 60% of dimensions measured by plug or thread gages/
What SPC chart can I implement for sample size 1?


Thanks



Oleg Volfson
 

Steve Prevette

Deming Disciple
Leader
Super Moderator
Hello
In my machining center 60% of dimensions measured by plug or thread gages/
What SPC chart can I implement for sample size 1?
Oleg Volfson

The p-chart would need some sample size larger than 1. In effect, you would only have 0% and 100% values. Unless for a single part you are talking about calculating the percent of dimensions checked that were acceptable.

There is a more advanced statistical technique called "logistic regression" that can work well with 0 or 1 data.
 
O

oleg_volf

Thanks For a quick replay
I am just thinking/
How can I or what chart should I place near the cnc machine to control the process for go nogo gages/

I just want a suggestion/
 

Steve Prevette

Deming Disciple
Leader
Super Moderator
You could do a sample size of 10, and have a grid on the chart that the operator could color in for every successful test, and at the end of the 10, the top of the bar would be at the percent success.

Or might be easier to color in if there is a failure.
 
O

oleg_volf

Thanks again
I am having a trouble visualize it/

Can we discuss it over phone conversation.
it just many things to explain that I do not know how to put it in writing

Thanks
Oleg
 

Steve Prevette

Deming Disciple
Leader
Super Moderator
I'll work up an example chart in Excel, but will need to do that tonight at home and I will post as a graphic.
 
Top Bottom