Search the Elsmar Cove!
**Search ALL of Elsmar.com** with DuckDuckGo Especially for content not in the forum
Such as files in the Cove "Members" Directory

Gage Calibration - Non calibrated gages are not used for final dimensions?

#1
I am hoping somebody can settle a debate in our shop. In the past with both QS & ISO we have calibrated every gage in our facility and I have never had a problem during survelience audits. However, I am currently upgrading my newest company to TS from ISO. When doing the gap analysis, I found several gages on the shop floor were not calibrated. To top the whole situation off, they were not even controlled. When I asked about why this was permitted the answer is: The uncontrolled and non calibrated gages are not used for final dimensions. They are used during production, however the dimensions they are used for are not part of the final print. The processes used for final dimensions do have calibrated and controlled gages. After reviewing the requirements of 7.6 I have to agree. Has anybody else beein in this type of experience and what was said by your auditors? My company says they have been audited for this several times and the auditor said he did not like it, but it was within the requirements.
All help would be appreciated.
 
D

D.Scott

#2
I agree and I don't like it either. If you have non-calibrated gages on the floor, there is a possibility that they can be used for other than what was intended. In addition to that, if one of the gages was way off, it could be used upstream as a reference and out of spec product made because of it. The product may not make it past the official measurement point but the product is still bad. If caught when it happened, re-work and scrap could be avoided.

I have found it is a lot easier to maintain a system that applies across the board. If the gage is used only for reference, we still calibrate it although our intervals and tolerances may not be as strict. Some of those gages may end up marked "reference only" but they are still in the system. Whatever you end up doing, cover it in your procedure.

Dave
 

cncmarine

Quite Involved in Discussions
#3
I agree.

Having them all under one system is the only way that I feel comfortable with the program.


Why take the chance ?
 
M

M Komarmy - 2012

#4
Look at this from the operations perspective. ISO/TS 16949 is a process oriented standard and emphasizes process and quality planning. Part of the APQP process involves the PFMEA. As you look at the flowchart of your process, there are definitely features you machine that have an impact on the downstream customer or operation, even if they do not appear on the final part print. If these need to be controlled, the gauges should be calibrated and uncertainty understood.

Example: A diameter is turned on the post end of a crankshaft that will be finish ground later in the process. This diameter is used as a chucking/driving diameter in the operation that finishes the flange end machining. The diameter is undersized and does not allow sufficient clamping force. The grinding machine for the flange machining causes the part to run away (overcome the drive clamps and turn at excessive speed). The part breaks apart and destroys the machine fixture, compensating gauges, grinding wheel, and puts a dent in the ceiling just before coming to rest about 6 feet from the machine operator.

I would consider this diameter (as well as the clamp overtravel safety circuit) to be an important feature that required control. This situation actually happenned when I worked at GM. We were lucky nobody was hurt.

In most cases the cost of defects from upstream operations are difficult to quantify. They can drive such things as poor tool life from inconsistent stock removals, no-clean up scrap due to undersize incoming features, form errors due to uneven stock, etc. The FMEA should help you consider the proper controls for such issues.
 
Top Bottom