process stability by Price technique

[Rojan]

Hi,

I read this article: https://www.rjginc.co.uk/paperclip/uploads/36/original/April_2013.pdf
The article mentions the Price 32-shot technique. Do you know how to use it?

Robert

[tbramel]

Here is a link to the first part of this article. See if this helps to explain.

[MTUHusky]

It sounds like they are taking 32 shots and recording the weight, and if the deviation is 0.4% or below you are good. I have never seen or used this myself. Typically shot weight is recorded to not only reach the target print weight but to ensure that the gate is sealed. I didn't dive real deep into this but I would think it might be useful as long as you do your DOE fill studies and gate seal studies as well. But I wouldnt rely on just the 32 shot study.

[chrisprocess]

Not familiar with the Price Technique but 30 or 32 is generally the minimum amount of value points needed to have a 'normal' distribution to calculate capability (Cpk, Ppk) and have a statistical high-level confidence of your value. Maybe this is what they're referring to?

[JayDub]

I think the aim is to use weight as a proxy for dimensions, and weight measurement as a sanity check on the process. If the weights are all over the place, chances are you aren't going to have good dimensional capability. Anybody can use a scale, so it's a cheap, quick and dirty, way to assess a process without tying up a metrology tech and a CMM. I can see this being useful after you've run an aesthetic widow study - run a 32 piece sample at the center point, measure a couple of parts/critical dimensions with a caliper, then check weights to get a sense of overall capability. It's not going to give you anything you can make final decisions on, but it will let you know if you're way off-base.

[rickbatey]

Our standard is 50 pieces and we do what the customers require. Weight first then dimensions as required on print such as on a fixture or free state. Oftentimes there's only a handful of critical dimensions anyway.
Rick.