In process statistics help
In process statistics help
(OP)
We are a custom job shop with thousands of part numbers that rotate in and out over several years. Some products we might make 50 of in a year others we might make 1000s. I would like to implement some SPC to the floor to help reduce the amount of scrap that makes it to inspection.
I am trying to figure out how to approach this. I know what key dimensions should be checked but I dont know how often to develop good statistics within a run or from one run to the next.
We are a small company (little more 100 employees) so there is no budget for big statistical software like minitab either.
If you have some pointers or have implemented in process inspection in your facility please help me get off on the right foot.
Ryan
I am trying to figure out how to approach this. I know what key dimensions should be checked but I dont know how often to develop good statistics within a run or from one run to the next.
We are a small company (little more 100 employees) so there is no budget for big statistical software like minitab either.
If you have some pointers or have implemented in process inspection in your facility please help me get off on the right foot.
Ryan
RE: In process statistics help
Process control is about looking for trends and excessive variability. Getting the data into a viewable form is more important than the program. Much of the seminal work in SPC was done even before the availability of computers, much less SPC programs.
Don't forget that the key is NOT inspecting to weed out bad parts; it's to make sure that bad parts aren't made in the first place. That's usually a discipline problem, not a measurement or analysis problem.
TTFN

FAQ731-376: Eng-Tips.com Forum Policies
RE: In process statistics help
The key issue is to understand the difference between the process potential, and what it is actually doing.
So typically we'd run 30 parts without touching the machine setup.
Plot the data on a histogram. Is it normal? hooray. Is it bimodal or uniform - ooer. Then plot the values in the order they were taken - is there a trend? Can you explain it?
Then set the machine up again and run some more parts. Do they fit in the original distribution? great. If not, you have a setup problem.
There is an enormous industry in SPC, but if you find a little book called "The Seven Tools of TQC" by McConnell or similar then you probably have enough to get you going, and is enough to run an 80 vehicle per hour production line.
Incidentally you should probably read The Goal by Goldratt.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: In process statistics help
There is a large area of the plant where we plan on implementing this. I want to start in a small area to test the waters and see about getting the system in place to see what works and what doesnt work. I also have a few people that will be willing to work with me on the floor more so than others. So I'd rather start with some of them..
Does anyone have a recommendation on starting in an area where the process is pretty consistant (like punch and die) or not consistent (lathes and other manual)?
RE: In process statistics help
SPC on very short runs is not as useful (but there are many other things you can do).
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: In process statistics help
TTFN

FAQ731-376: Eng-Tips.com Forum Policies