Inspection and Detection - Kit to production - Need an inspection routine

  • Thread starter Ross_Henderson - 2005
  • Start date
R

Ross_Henderson - 2005

#1
Inspection and Detection

I am getting ready to release some kit to production but need to come up with an inspection routine for this.

Inline monitoring is not a possibility so I need to tag QC onto the end of the process. The machine will output 3000 units an hour and due to the size of the staff the maximum inspection rate will be 1/250. The machine has a problem that causes it to occasionally produce ~10% defective units. The distribution of these defects are random throughout the finished units.

How do I use these figures to calculate the average amount of time to detect this issue or even if we are likely to detect it at all?

Obviously if I can show that employing an extra person to increase our inspection rate will save money overall then I can get this person.

Thanks in advance for you help.

Ross
 
Elsmar Forum Sponsor

Mike S.

Happy to be Alive
Trusted Information Resource
#2
Ross_Henderson said:
I am getting ready to release some kit to production but need to come up with an inspection routine for this.

Inline monitoring is not a possibility so I need to tag QC onto the end of the process. The machine will output 3000 units an hour and due to the size of the staff the maximum inspection rate will be 1/250. The machine has a problem that causes it to occasionally produce ~10% defective units. The distribution of these defects are random throughout the finished units.

How do I use these figures to calculate the average amount of time to detect this issue or even if we are likely to detect it at all?

Obviously if I can show that employing an extra person to increase our inspection rate will save money overall then I can get this person.

Thanks in advance for you help.

Ross
Let me see if I understand, please correct me if I am in error:

You only have time to inspect 1 out of every 250 parts the machine produces, or 12 per hour? Why?

You can't adjust the machine to correct it if a defect is found?

The machine sometimes produces 10% defective at random?

Is this right???
 
R

Ross_Henderson - 2005

#3
The machine seems to occasionally damage a piece within the machine, when this damage occurs seems to be random and our equipment engineers are unable to find the exact cause and it seems to happen once or twice a month. When this damage occurs around 10% defects are produced, not every unit is affected and it is random the equipment manufacturers are aware of the issue but have more or less classed it as a feature.

If we increase the inspection frequency we will need to stop the machine in order for the operators to carryout the inspection if we slow the machine down we will create a bottleneck in the process.

Hope this answers your questions.

Ross
 

Wes Bucey

Quite Involved in Discussions
#4
Ross_Henderson said:
The machine seems to occasionally damage a piece within the machine, when this damage occurs seems to be random and our equipment engineers are unable to find the exact cause and it seems to happen once or twice a month. When this damage occurs around 10% defects are produced, not every unit is affected and it is random the equipment manufacturers are aware of the issue but have more or less classed it as a feature.

If we increase the inspection frequency we will need to stop the machine in order for the operators to carryout the inspection if we slow the machine down we will create a bottleneck in the process.

Hope this answers your questions.

Ross
I have a sneaking suspicion Mike S. and I are thinking along the same lines.

Here's how I see it, Ross. If you need a temporary fix, consider this:
  1. What damage does the machine make when it goes "awry" - same defect or random defects? (This has NOTHING to do with the random distribution throughout the run.)
  2. Is this damage instantly visible to the naked eye or is it internal, microsopic, or some other condition which cannot be discerned by vision?
  3. Is there a possibility you can screen for JUST the damage on all the parts (100%), leaving your inspection methodology alone? (i.e. Is the balance of the process in control?)
While you do the TEMPORARY fix of detecting defects, you MUST find the root cause of the problem and fix it. Omitting this root cause analysis and subsequent fix by throwing up your hands and letting a machine manufacturer tell you
When this damage occurs around 10% defects are produced, not every unit is affected and it is random the equipment manufacturers are aware of the issue but have more or less classed it as a feature.
is to be a complete traitor to the Quality profession. If the current process cannot be fixed, you need a different process.

Would you give a gun to a soldier and tell him:
"This is a fine gun, but it has a peculiarity which we class as a "feature": Once in a while it develops a quirk and will blow up and kill the person wielding it once out of every ten shots. The anomoly is random. Work with it."
 

Mike S.

Happy to be Alive
Trusted Information Resource
#5
I think the answers to Wes' questions are very important.

I might add: You say "When this damage occurs around 10% defects are produced". Does that mean that when the process is "working" there are basically no defects and when it is "not working well" the defect rate is ~ 10% and not 1% or 3%, but always around 10%?

If so, once the machine starts damaging parts "once or twice a month" you should be able to detect this problem with a sampling plan, but sampling only 1 out of 250 will likely not detect it. I have forgotten much of my probability knowledge through lack of use, but I think you'd have to look at about 30 parts with no defects to have a >95% assurance that the machine is not on the blink. Looking at the OC curves of various sampling plans should help you pick a workable sampling plan if you can't 100% test for this defect.
 
#6
2400 defective parts per shift! I couldn't imagine that your management would even consider running a process with a defect rate of 10%.
Surely you jest.
 
D

dfirka

#7
Ross,

I agree with the comments made so far, and I think that the problem you described needs more background to be solved without "shots in the dark":

Some additional questions:

1- What is the impact of the effect on the customer or clients ?
2- What is the cost of reparing a defective unit?
3- What is the total cost of allowing a defective unit to reach the customer?

One possibility in the short term is to find an inspection procedure fulfilling two goals:

1- decrease the total cost of poor quality

2 (and very important)- collect data to help in the prevention of the problem, trying to solve the special cause, or trying to find a model to predict the frequency of occurrences of the problem.

Based on your description so far, this could be a very juicy project for any BB.

Pls take this as a very limited answer due to lack of profund knowledge of the problem. Hope this helps.

Daniel
 

Wes Bucey

Quite Involved in Discussions
#8
Ross_Henderson said:
The machine has a problem that causes it to occasionally produce ~10% defective units. The distribution of these defects are random throughout the finished units.

Obviously if I can show that employing an extra person to increase our inspection rate will save money overall then I can get this person.

Thanks in advance for you help.

Ross
Say, Ross, if I agree to come help your organization "resolve" its issues, can we go punting on the Thames and carouse in a lot of pubs?
 
G

Greg B

#9
Ross_Henderson said:
The machine seems to occasionally damage a piece within the machine, when this damage occurs seems to be random and our equipment engineers are unable to find the exact cause and it seems to happen once or twice a month. When this damage occurs around 10% defects are produced, not every unit is affected and it is random the equipment manufacturers are aware of the issue but have more or less classed it as a feature.

If we increase the inspection frequency we will need to stop the machine in order for the operators to carryout the inspection if we slow the machine down we will create a bottleneck in the process.

Ross
Ross,

Does the random defect occur within an area of the production line that cannot be inspected and does it then continue to produce the 10% of defects before being spotted? If it is in an area that cannot be visually monitored can a sensor (Rev counter,Belt wiegher, Under/Overspeed switch etc) be installed in the production line to find the anomaly earlier and thus reduce the amount of time the machine produces defects? I hope this makes sense.

On the other hand: If the customers are accepting of this 'Defect' is it really a defect? Should you change your specifications to allow for this lower end defect? We recently had a lot of product that did not meet OUR spec but it did meet the customers. We convened a meeting a everyone discussed why we had placed such a tough limit on our specs. The spec was chnaged and the NC product was then reclassifed to Conforming.

Bottom line though is the root cause of the anomaly should be found as stated by Wes and Mike.

Greg B
 
Thread starter Similar threads Forum Replies Date
Sean Kelley FMEA Visual Inspection Detection Rating FMEA and Control Plans 5
B "Detection, NOT Prevention!" - Relying on Final Inspection Quality Manager and Management Related Issues 48
V Detection rating for visual inspection in PFMEA FMEA and Control Plans 19
Y PFMEA detection value for checking C of C in receiving inspection FMEA and Control Plans 2
G Assignation of RPN rating (Detection) on Visual Inspection where subsequent operation FMEA and Control Plans 18
P Need a programmer for QVI's VMS software for optical inspection machine Inspection, Prints (Drawings), Testing, Sampling and Related Topics 0
silentmonkey How to decide what characteristics need to be verified during incoming inspection? ISO 13485:2016 - Medical Device Quality Management Systems 5
Y What are different Special Inspection Level 1-4 and General spesification 1-3 ? AQL - Acceptable Quality Level 0
J Mechanical inspection techniques of close tolerance parts Inspection, Prints (Drawings), Testing, Sampling and Related Topics 4
T Help to Suggest name for a new certification and inspection company Coffee Break and Water Cooler Discussions 7
B GM GP-12 Exit Criteria - Additional Safe Launch Inspection - (Also see GM1927-28 ) Customer and Company Specific Requirements 2
S Process Inspection -Sub assembly process inspection sheet Lean in Manufacturing and Service Industries 3
C OEE and In-process Inspection Manufacturing and Related Processes 2
R AS9100 - 8.4.2 - Receiving Inspection Requirements AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 1
I Mother bobbin final inspection criteria Inspection, Prints (Drawings), Testing, Sampling and Related Topics 3
Marc Visual Inspection - Color Vision Coffee Break and Water Cooler Discussions 15
G Inspection Logs - Asked to remove an Inspection Sheet ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 4
Skooma Receiving Inspection - Boss trying to save money AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 7
T Sample of 1st Article Inspection Report wanted APQP and PPAP 3
T Nonconforming product at customer detected by a routine inspection by field service Nonconformance and Corrective Action 9
A Definition of customer in ITP (Inspection & Test Plan) Contract Review Process 3
T Correct MSA study for an automated camera system which makes attribute inspection Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
A DCMA inspection for a drop-shipment AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 2
S QUALITY OBJECTIVEs for third party garments factory inspection ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 5
D Lean and Elimination of QC Inspection Points in a New factory Lean in Manufacturing and Service Industries 9
F FDA-registration and inspection cost 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 1
I Receiving Inspection Requirement in IATF IATF 16949 - Automotive Quality Systems Standard 3
R Supplier related drawings and verification of process requirements - Source Inspection AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 3
D AS9100 Inspection records - Is there a requirement to have gauge ID and calibration status AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 5
D Good Acceptance Activity/Inspection flowchart for reference - Wanted Please Process Maps, Process Mapping and Turtle Diagrams 2
K Inspection Certificate EN 10204 2.1 - Distribution company Other ISO and International Standards and European Regulations 4
S Improving Quality inspection gate in one piece flow manufacturing process Manufacturing and Related Processes 0
M Loss of a Quality Record - FDA Inspection Records and Data - Quality, Legal and Other Evidence 4
S Need Assistance in Visual Inspection - Tiny electronic components AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 11
S. Moore Is an Annual Layout Inspection the same as an Annual Re-validation? Internal Auditing 1
D Incoming (Receiving) Inspection - General form for incoming part inspection Document Control Systems, Procedures, Forms and Templates 17
K First Article Inspection (FAI) - Equipment used - Dimensions vs. Go/No-Go ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 7
M Informational USFDA Draft Guidance – Review and Update of Device Establishment Inspection Processes and Standards Medical Device and FDA Regulations and Standards News 0
S Inspection/sampling economics Inspection, Prints (Drawings), Testing, Sampling and Related Topics 3
C Is a First Article Inspection (FAI) Procedure required by ISO 13485? ISO 13485:2016 - Medical Device Quality Management Systems 3
T EN 10204 3.1 Inspection Certificate - Machine Shop Various Other Specifications, Standards, and related Requirements 4
A Doubt on multiple inspection carrying out for same balloon number during Stage Inspection and Final Inspection? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 3
M 3rd Party Sorting and Inspection Company Certification Service Industry Specific Topics 4
D FDA QSR task checklist based on inspection citations 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 5
John Predmore What size pinhole can be reliably detected using visual inspection? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 7
F Holes position inspection - Calculation of centre distance and plug sizes of a gauge Inspection, Prints (Drawings), Testing, Sampling and Related Topics 5
V Inspection with 3D Scanning - Reference Data Inspection, Prints (Drawings), Testing, Sampling and Related Topics 0
L Inspection Plan for Microscope Objective Lens Inspection, Prints (Drawings), Testing, Sampling and Related Topics 4
N Process Flow diagram steps for inspection and packaging APQP and PPAP 4
S Poka Yoke Inspection Retaining Ring (C-Clip) Inspection, Prints (Drawings), Testing, Sampling and Related Topics 4

Similar threads

Top Bottom