Choosing In-Process Inspection Characteristics



Hi everybody:

I just joined and this is my first post; please forgive me if I do it wrong. My question is: does every characteristic in the part print need to be checked in the regular in-process inspections? To elaborate: I work in a job shop that makes metal formed parts. I was always taught that you should be able to "control" your process with around five characteristics. If you need more than that, you don't really understand your process. These five (or so) characteristics are what you routinely check and control chart. The reasoning being that it is better to check the "critical" characteristics more often than to try and do full dimensional layouts every hour or so. We do a full layout at set up. Some where I work insist on checking every characteristic every inspection, but this means many hours of production occur between checks. I hope I gave enough information for you folks to help. Thanks for your advice
Elsmar Forum Sponsor
I do the same in a similar environment - What I do minimizes the overall time and ends up by checking almost the entire part -
I conduct a First Piece Inspection at every department station. It starts with raw material incoming (stainless steel sheets), then I do one at the shear, waterjet or laser to verify those processes, then bending, then welding, then assembly, then finishing, etc. When done, the part is almost completely inspected, and as a first piece, this means not every part is done this way. We do repeat this every X amount of parts, depending on the run size.
In the end I am using a sampling inspection for the batch. The full inspection (every dimension and characteristic) is done with a FAI.


Involved In Discussions
In our company we do a FAI at the start of each department process, ex. Heading dept. Then during the run we do a visual inspection at 500 pcs. At 1000 pcs we do an in-process inspection and all characteristics are inspected and documented on an in-process inspection form.


It's been a few years since I worked in a shop manufacturing "commercial" products, but the inspection process was fairly straightforward there. Some parts had as few as three critical dimensions and I can't remember anything having more than a dozen. We did first piece/article inspections and from there we performed periodic floor inspections to verify operators were doing their own hourly inspections. Not very proactive. We did material testing similar to what was described above (raw material, plating thickness, etc.) We also performed inspections at each operation, but they were constantly moving toward cellular operations. So the floor layout changed. A lot. I could comment more, but then I'm afraid this would start to sound like a rant. :notme:

Last edited by a moderator:



Thanks for the reply. When your operators did their hourly rounds, did they check every characteristic on the print, or just several chosen ones? We can have prints with over 24 characteristics on them, and it takes a while to check all of them.


Stop X-bar/R Madness!!
Trusted Information Resource
The correct answer: it depends. For example, if you are machining, it is meaningful to measure the one tightest characteristic per tool path. In other areas, you amy need to check them all, simply because your process can randomly fail at any point in the process.


To clarify, in the case I mentioned the operators were only responsible for checks on products they were running. The inspectors were essentially “policing” them with their rounds, although the inspectors did also perform some in-process testing. This “policing” isn’t something I agree with, but this is getting a bit off topic.

In this case, each check was a full inspection of every characteristic. I believe this was necessary because the processes were not very well controlled and the machine capabilities were not even known. Unlike what the OP described, these checks could be completed within a few minutes, and even the in-process testing could be performed relatively quickly. They were using control charts for performance checks such as drill testing, so there were some good elements of their system. But they could have been much better.

To Bob Doering’s point, without knowing exactly what it is you’re running, there is no definitive answer. But I do feel that many companies could benefit from understanding their processes better.

I hope that this post is more to the point :lol:



Stop X-bar/R Madness!!
Trusted Information Resource
Two points to consider:

A comprehensive quality program uses Process Failure Mode Effects Analysis, or PFMEA. It answers the Why? of doing inspection for any characteristic. These are the bad things that will happen if you don't inspect that feature. If there is no "bad thing" then the need to measure it is low.

As far a frequency, here is the risk: if you find a dimension out, you should sort through all of the bad product to the last good inspection. If you inspect every 2 hours, that is a much lesser issue than ever four hours, and so on. Balance this simple risk.
Thread starter Similar threads Forum Replies Date
E Choosing correct MOPs IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
Q Choosing Nonconformities to Report ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 26
C Quantifying risk in choosing the number of parts, operators and replicates in a GR&R Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
Q Old products new class - Dental Devices - Choosing tests EU Medical Device Regulations 2
M Choosing Auditors - ISO 9001 / ISO 27001 (UK) IEC 27001 - Information Security Management Systems (ISMS) 2
T AS9100D - Scope of QMS for New Company - Only Choosing a Function Subset Due to Management AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 14
E Choosing an ISO 9001 registrar with auditors familiar with our industry Registrars and Notified Bodies 10
M Dilemma about choosing the most applicable clause related to Risk ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 19
J Choosing QMS Software for Aerospace Company Quality Assurance and Compliance Software Tools and Solutions 5
B Choosing not to calibrate (IATF 16949) IATF 16949 - Automotive Quality Systems Standard 6
Q Choosing between ISO 9001 (2015) & TL 9000 certifications ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 4
H On choosing touchscreen displays and ensuring IEC 60601 compliance IEC 60601 - Medical Electrical Equipment Safety Standards Series 6
L Choosing the correct Distribution for Acceptance Sampling Inspection, Prints (Drawings), Testing, Sampling and Related Topics 19
S Choosing a suitable type of Elisa to Test my Sample Misc. Quality Assurance and Business Systems Related Topics 3
S Choosing the correct Elisa Test Food Safety - ISO 22000, HACCP (21 CFR 120) 1
K Choosing a Six Sigma training organization Six Sigma 4
H Choosing between RABQSA Lead Auditor or ASQ CQA Certification Professional Certifications and Degrees 2
S Choosing ISO 9001 Training and if I need the training for work ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 8
S CE Marking choosing between module A, B CE Marking (Conformité Européene) / CB Scheme 2
A Getting Stuck Choosing a Sampling Plan Inspection, Prints (Drawings), Testing, Sampling and Related Topics 6
M Choosing the right Industry Financial Report Manufacturing and Related Processes 1
M Advice for choosing Rechargeable Lithium Batteries to be used in a Medical Device Other Medical Device Related Standards 16
L Choosing a Statistical Test for dissertation results! Statistical Analysis Tools, Techniques and SPC 4
I Choosing a X-Ray Fluorescence Measuring Device for Chrome Coating Inspection, Prints (Drawings), Testing, Sampling and Related Topics 5
J Choosing the Best Standard - ISO 9001 or ISO 13485 ISO 13485:2016 - Medical Device Quality Management Systems 14
B Choosing Inspection Level and AQL AQL - Acceptable Quality Level 1
I Choosing the alpha level in an ANOVA Study Statistical Analysis Tools, Techniques and SPC 3
M Tolerance vs. Study Variation - Choosing the right one Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 5
S Choosing a Higher EER Air Conditioner After Work and Weekend Discussion Topics 7
T Choosing a Mentor Career and Occupation Discussions 3
K Selection Criteria for choosing a Management Representative for QMS ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 13
A Choosing Document Control Software Document Control Systems, Procedures, Forms and Templates 13
S Choosing Parts for Attribute MSA (Measurement System Analysis) in 4th Edition, pg 132 Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
C Difference between softwares in choosing correct Taguchi designs Using Minitab Software 16
bio_subbu Choosing a laboratory for biocompatibility test ISO 13485:2016 - Medical Device Quality Management Systems 8
M Choosing a Laser Micrometer - Your recommendations? General Measurement Device and Calibration Topics 8
G Short TQM training - Choosing of most important points Training - Internal, External, Online and Distance Learning 3
B Choosing number of subgroups and subgroup size Statistical Analysis Tools, Techniques and SPC 4
D Choosing a Vision System - Recommendations for a User Friendlier System Quality Tools, Improvement and Analysis 3
D Need Help on choosing dimensional standards / equipment General Measurement Device and Calibration Topics 2
J Choosing Samples for Gage R&R - Randomly picked samples show very little variation Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 13
Tim Folkerts DOE: Choosing a Design - Factors that affect the choice of design The Reading Room 0
B ISO10012:2003 Question - Choosing or assessing the capability of a piece of equipment Other ISO and International Standards and European Regulations 1
G Choosing a Sampling plan for Start Up Fabless IC Company - Guarantee a 200 DPM limit Inspection, Prints (Drawings), Testing, Sampling and Related Topics 9
gard2372 Choosing between a Small Company or a Large Company Career and Occupation Discussions 17
D Choosing a notified body for a new start up company in the UK - Medical Device area Registrars and Notified Bodies 6
G Choosing Supplier Evaluation Methods - Determining what a Critical Supplier is Supplier Quality Assurance and other Supplier Issues 31
Steve Prevette Choosing Performance Indicators Registered Visitor Articles Archive 0
C Questions to Ask Prospective Registrars Before Choosing Registrars and Notified Bodies 3
L Choosing a Registrar - Need registrar selection advice Registrars and Notified Bodies 6

Similar threads

Top Bottom