Flow Solder Control Chart - I believe I need an Xm-R chart

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Chris May

Good Morning everyone,

It is nice and sunny here in Bristol, England.
The birdies are singing and all is well...(yeah right!)

I am looking to apply process control to our three wave/flow soldering systems.

There is a lot to do here, so I am taking it in small chunks.
The first area I am looking at are the temperature related elements which are the preheaters and the solder pot itself.

I want to generate a control chart to monitor the temps of both on each machine. Readings will be taken morning and early afternoon.

Presently, I am collecting readings of each every 30 minutes so that I can use these samples to generate the UCL & LCL values

The two daily readings would obviously be entered onto the control chart and as long as they stay within the limits, or we get a trend of plots, everything will be wonderful.

I have used simplistic control charts in the past, but having read up on the various types in more detail, I believe I need an Xm-R chart.

Would I be correct or is there a better chart type that I could use.?? :confused:
 
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Rick Goodson

Chris,

I think you are on the right track. I have used Individual X and Moving Range charts to track wave solder machines and they work well. I believe however, you may want to reconsider your morning and afternoon sample times. I would look at the results of the study you are doing every 30 minutes before deciding how often to do the ongoing sampling. Once you see the variation in the machine you may want to sample more often.

Regards,

Rick
 
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Chris May

:bonk:
Absolutely Rick and thanks for taking the time to reply.

I have been taking sample temps for nearly 2 days now. The two newer machines are Ok as you would expect. The USL & LSL for pot temp is 250 +- 5 degs and so far it looks as though the actual control limits will be within these bounds. In this case, obviously USL & LSL are based on the manufacturers spec.

The older machine however..:ko: :vfunny: :frust:

The temps for pot & preheat are wildly variable........but it is 17 years old.

These will not be within the SL's and so this machine will prove itself to be incapable (??!!)

My next steps for the other elements of the wave solder systems will be to "weigh" the flux deposition (known clean galss plate before and after fluxing) and compare to the manufacturers coverage per sq/cm spec (USL & LSL). Samples will lead me to the CL's for said systems.
The others will be conveyor speeds and wave heights. Not much thought gone into that as yet.

The Surface Mount lines will be interesting, though. Have you any thoughts to share on the approach to a Surface Mount line or two ??:smokin:
 
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Rick Goodson

Chris,

Sorry, I have no experience with surface mount lines. Hopefully someone else can offer a thought or two.

A passing thought on flux density. We monitored flux density and cleanliness the same way we did tool wear. While we did top off the flux as required, when the flux reached the alarm limit we would dump the flux and replace it with new material.

Best of luck with the rest of your project.

Regards,

Rick
 
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