Establishing SPC for small batches of 10-15 units

O

oleg_volf

#1
Hello

I need sum suggestions to establishing SPC for small batches 10-15 units or start SPC for new part in the production?
For every part I have critical dimensions from engineering/

Thanks

Oleg Volfson
CQE,CQM
 
Elsmar Forum Sponsor
S

Surehawk

#4
Not sure I completely understand the question. Since making a SPC chart for a batch of 10-15 units seams unececesary.

There is a very argued method called pre-control that unlike SPC is supposed to work directly and not need 10-15 units, is it something like that you need?

http://www.symphonytech.com/articles/pdfs/precontrol.pdf

Anyway, if you are able to explain a little more what you need the SPC chart for I am sure there will be plenty of help.
 
O

oleg_volf

#5
Thank you for your reply
I my previous post I offered to use a pre-control for the period of gathering enough data to build an imr or xbar charts/
After a reading a little more a understood that pre control is not very good control way/
because of that I asked if there is a similar chart for new process to prepare gathering data and perform spc on the critical dimensions/
 
S

Stevenli

#6
I think this is a great topic, as Surehawk mentioned, you may use Pre-control chart, other than that there are some other chart you may use, e.g. Difference or Deviation from Nominal (DNOM) Xbar-R chart or Standardized Xbar-R chart or even Standardized Attributes Control Charts etc.

You can search "Short Run" under this SPC forum.

Hope it works
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#7
oleg_volf: patience friend. As the banner notice says this is a holiday weekend in the US and many are 'away' to celebrate.

In the meantime, if you have a process that will eventually yield many subgroups, a simle run chart against the spec limits may suffice for you.

I recommend reading some of Donald Wheeler's papers on SPC. they are free and he deals with many topics that you may encounter.

I would also recommend posting your data for a characteristic or two here and a description of the process, characteristic and measurement system so we can provide better advice. The best advice is usually specific to each example.
 
O

oleg_volf

#8
Hello and thank you
I have a new part in production.
We made till know only 9 units and measured critical dimension.
See the data:
GazBock ?17.3-0.04
1) 17.284
2) 17.293
3) 17.296
4) 17.3
5) 17.3
6) 17.3
7) 17.287
8) 17.295
9) 17.279
I started to use pre control (attached)
In order to maintain the parts from been out of spec while I collecting the date for building the control limits for imr chart/
DNOM chart is not good for me because I paste hard copy on the machine and the worker marks each unit and monitors the trend and spec of the dimension/

I started to question myself after reading an article that pre control should not be used and because of this started this thread/'
 

Attachments

bobdoering

Stop X-bar/R Madness!!
Trusted Information Resource
#9
Before rubber stamping any SPC technique,you need to understand the type of variation you are expecting. What is the process you are trying to control, and what is the characteristic? Have you determined the characteristic you are trying to control is correct? If, for example, you are machining the dimension, none of the previously mentioned charts are likely to be correct.
 
O

oleg_volf

#10
Hello

Yes The dimensions are machined.
How should I proceed if you say that all before are not correct
 
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