I have heard that there has been some debate regarding the validity of SPC
data taken on a bulk material process. Has anyone heard anything about
this?
Also, Does anyone out there have a method for performing SPC on a textile
process such as adhesive coating a nonwoven and monitoring the total weight
of the product? I am currently taking sample across the width from a yard
taken off each roll produced and then using the average for the X-bar and
Range. I do not think that this would be considered a statistically valid sampling plan. Our roll size is 1,000 linear yards per roll.
Any help would be really great.

Thank you,
Frank C. Grace

Also see www.16949.com/ubb/Forum10/HTML/000035.html (http://www.16949.com/ubb/Forum10/HTML/000035.html)

From: "David J. Mulholland" mulholdj@home.com
Newsgroups: misc.industry.quality
Subject: Re: SPC of Bulk Material (Continous Textile Process) QS and ISO 9000
Date: Wed, 16 Aug 2000 02:50:13 GMT
X-Complaints-To: abuse@home.net
X-Trace: news1.rdc1.va.home.com 966394213 24.6.191.29 (Tue, 15 Aug 2000 19:50:13 PDT)

Frank,

Donald Wheeler, in one or more of his SPC press books gives a method...book title escapes me at the moment. It is listed under chemical industry topics, I think. Anyway, here is the summary:

1. Use XBar-R for tracking "within batch" variation.
2. Use X-MR (subgroup of 2) for tracking "between batch" variation.

I am doing this now for "Product" (vice Process) Control Charts on incoming materials plotting several tests (including weight in Oz/YD^2) on laminated and coated fabrics for helium filled vehicles and it meets my needs for process monitoring of my supplier.

I am using a sample size of 5...stratified random sampling where the 5 are drawn on different warp and fill yarns across the web of the fabric at one or both extreme ends of the finished roll. We have chosen each roll (100 to 800 yards) as the sampling interval, and every roll in each lot is tested.

Hope this helps. E-mail if you want to see a chart.

Dave Mulholland mulholdj@home.net

"FrankCGrace" <fbgrace@mediaone.net> wrote in message
news:u4Qb5.24885$Q8.184729@typhoon.ne.mediaone.net...
> I have heard that there has been some debate regarding the validity of SPC
> data taken on a bulk material process. Has anyone heard anything about
> this?
>
> Also, Does anyone out there have a method for performing SPC on a textile
> process such as adhesive coating a nonwoven and monitoring the total weight
> of the product? I am currently taking sample across the width from a yard
> taken off each roll produced and then using the average for the X-bar and
> Range. Any help would be really great.
>
> Thank you,
> Frank C. Grace
> fbgrace@mediaone.net