Hi all,

Need your advise - for our injection molding machines, there are lot of gauges indicating various values for say temperatures, pressures etc.

Our current practise is to calibrate all gauges, which i think is a overkill. When I proposed this reduced calibration frequency to the management, they told that our Customers may not accept this. They donot want any observations from any of our customers on calibration as it impacts product quality directly.

Can I have ideas from the forum suggesting how can we reduce this calibration overkill ? If I could have any procedures supporting the reduced calibration (with justification) is also most welcome.

Thanks,

Hi, Qualityalways - always good questions!

The simple answer is that unless the gauge is used to make a decision about the 'quality' of the product or process - which affects product quality - (to spec), then it probably doesn't need calibrating. So a temperature may be important to a mold cavity, but the water pressure on the cold side of the mold, may not be so important to a good molded product. The screw pressure would be important to a complete fill, etc.

Often, a lot of the process equipment gauges are to indicate the presence of a particular utlility parameter, such as air pressure. The actual pressure value isn't always so important, as much as simply the presence of the air pressure.

Of course, if you find the potential cost savings, then that'll sell it!

You may, unfortunately, still get a finding from your customer, because they might not understand this reasoning. If not already part of your calibration process, you should write exclusion statements with a justification for the equipment not being in the cal. system.

Good luck.

Andy

Hi, Qualityalways - always good questions!

The simple answer is that unless the gauge is used to make a decision about the 'quality' of the product or process - which affects product quality - (to spec), then it probably doesn't need calibrating. So a temperature may be important to a mold cavity, but the water pressure on the cold side of the mold, may not be so important to a good molded product. The screw pressure would be important to a complete fill, etc.

Thanks Andy. Just to top up your comment, if a particular is "quality impacting" for one product but not for other product, we cover both gauges for calibration, right ?:thanx:

Tell me more..an example, please.

Andy

Nice answer, Andy.

Many times equipment like Injection molding machines and others are made with multiple, various gauges of all sorts. They indicate all kinds of pressures, temperatures, etc. for the different components on the equipment. Many of these gauges serve as diagnostic tools for service/troubleshooting, but not really quality assessments. In my experience, most of these gauges have For Reference Only on them.

Now, in my opinion, the necessity for calibration will depend. If you are using the gauges to assess a quality impact, then they should be calibrated. For example, "do not begin injection process until nozzle four gauge reads between 300 and 310", then I would say that gauge needs to be calibrated. If the operator starts the equipment up, lets it heat up, and as long as plastic is flowing at a consistent rate they start production, then I would say calibration is not required.

That is to the question of whether to calibrate or not.

Calibration frequency is another matter. First, determine if your requirements will allow a different frequency. Next, determine the impact if you extend the date. Do you have a final product inspection or something, where the gauge readings really don't matter? Then I would say the impact is small. Also, have these gauges been consistently passing calibration, with little or no adjustment? Are there any customer expectations?

Given all that, you might could build a case for extending the time frame with management.

To Andy's follow up question: I would keep a cautious eye on calibrating machine #1 and #2, but not calibrating machine #3 and #4. It will be difficult to assure that critical parts were not produced on #1 and 2.

However, the last suggestion is mere speculation on my part. Anyway, hope there is something here to help.

Many times equipment like Injection molding machines and others are made with multiple, various gauges of all sorts. They indicate all kinds of pressures, temperatures, etc. for the different components on the equipment. Many of these gauges serve as diagnostic tools for service/troubleshooting, but not really quality assessments. In my experience, most of these gauges have For Reference Only on them.

Now, in my opinion, the necessity for calibration will depend. If you are using the gauges to assess a quality impact, then they should be calibrated. For example, "do not begin injection process until nozzle four gauge reads between 300 and 310", then I would say that gauge needs to be calibrated. If the operator starts the equipment up, lets it heat up, and as long as plastic is flowing at a consistent rate they start production, then I would say calibration is not required.

That is to the question of whether to calibrate or not.

Calibration frequency is another matter. First, determine if your requirements will allow a different frequency. Next, determine the impact if you extend the date. Do you have a final product inspection or something, where the gauge readings really don't matter? Then I would say the impact is small. Also, have these gauges been consistently passing calibration, with little or no adjustment? Are there any customer expectations?

Given all that, you might could build a case for extending the time frame with management.

To Andy's follow up question: I would keep a cautious eye on calibrating machine #1 and #2, but not calibrating machine #3 and #4. It will be difficult to assure that critical parts were not produced on #1 and 2.

However, the last suggestion is mere speculation on my part. Anyway, hope there is something here to help.

Bred, thanks for the valuable suggestions.

Tell me more..an example, please.

Andy

Andy, unfortunately I donot have off-hand now. Our Operations guys often say that the quality impacting parameters of the machine for one part may not be quality impacting parameters on the same machine for another part.

Could this be possible ?

Bred, thanks for the valuable suggestions.



Andy, unfortunately I donot have off-hand now. Our Operations guys often say that the quality impacting parameters of the machine for one part may not be quality impacting parameters on the same machine for another part.

Could this be possible ?

It is possible, I guess, but improbable. It could be a design related issue. I have experience of a part where a particular defect was caused due to a process parameter, but the defect didn't occur on other parts because they weren't a similar design.

Otherwise, I'm thinking that these guys are using voodoo to run their processes:lmao:

Andy

It is possible, I guess, but improbable. It could be a design related issue. I have experience of a part where a particular defect was caused due to a process parameter, but the defect didn't occur on other parts because they weren't a similar design.

Otherwise, I'm thinking that these guys are using voodoo to run their processes:lmao:

Andy

Thanks Andy, on Monday will call a meeting with operations guys and see if I could get some more info. Have a nice weekend.