How to Effectively Apply Short Run SPC

Re: how to implement spc on low volume/Short run SPC

Our process is for manufacturing parts.we produce 20-30 parts per month.

Thanks

Re: how to implement spc on low volume/Short run SPC

chvrajus said:

Our process is for manufacturing parts.we produce 20-30 parts per month.

Thanks

Click to expand...

Is it assembly, machining, injection molding...? A little more specific is important. Thanks.

Re: how to implement spc on low volume/Short run SPC

Yes it is an assembly.

I don't know what information you need.

I am in Phase 1 in my implementation,
I need to prepare a demo where I have to explain how spc can be implemented in low volume/short run.

I need some explanation on the process and points given in my previous post.

Thanks
Ven


Is it assembly, machining, injection molding...? A little more specific is important. Thanks

bobdoering said:

Is it assembly, machining, injection molding...? A little more specific is important. Thanks.

Click to expand...

Re: how to implement spc on low volume/Short run SPC

chvrajus said:

Yes it is an assembly. <snip>

Click to expand...

Here are a sample of Short Run SPC resources:

Technique Review – Short Run SPC

(broken link removed)

(broken link removed)

Short Run SPC blank charts

Short-run SPC techniques

I either think that you just have to continue using a X-R and just conected the different batches, or a X-S could work so you could anylize the variation for each batch (don´t include the set up adjustment for the Cpk calculation)

A very important consideration when short run charting machining operations is that if a run is short enough, it will be totally affected by the special cause of "warm-up". Warm-up is a condition that is not in control because it is not stable or predictable. You can chart, but your reaction plan will be more concerned about adjustment to stay in spec, as your "process" in such a case is not the tool wear or even machine variation, but your adjustment technique itself!

I'm in the process of setting up SPC within our suppliers of injection moulded parts. Typically we are talking short run, large size product, although this does vary from part to part. (typically a batch of 8000 parts would be produced on an 8 cavity tool, taking about 2-4 hours)

The links so far have been of great use, as one of the concerns being voiced by our suppliers is that the runs are too small for SPC to be usable. I disagree, as there are techniques to allow short run data to be of use. The other major concern from suppliers is the cost of implementation, and I think I have almost convinced them that the aim is to save them money, not cost them money.

Once I make progress on the planning side I aim to put up a thread with attached examples of how we are going about this. The next 2 days will be almost entirely devoted to this as I'm currently at our China site, but they are on closedown for the next 2 days.

pearsonow said:

The links so far have been of great use, as one of the concerns being voiced by our suppliers is that the runs are too small for SPC to be usable. I disagree, as there are techniques to allow short run data to be of use. The other major concern from suppliers is the cost of implementation, and I think I have almost convinced them that the aim is to save them money, not cost them money.

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Even for molding, remember that the time it takes the press to achieve steady state - or warm-up - is a special cause and unsteady state. If the press does achieve that state within the run, any point after that may show a value in use of SPC to detect signals to address.

Indeed Bob. This is one of the concerns raised by our suppliers, and is an issue we are looking to address. The issue we have is if the press does not achieve steady-state with 'good' product being produced, how can we then use those parts with any confidence....

Our suppliers claim that their presses achieve steady-state fairly quickly, and I am inclined to believe them, but we need actual data before we can assess the validity of the claim in a factual manner.

Statistical process control (SPC) procedures can help you monitor process behavior. Statistical Process Control has been run on mass-producing and long spanning processes