# Short Run Capability - Batch quantity is 15,000 to 20,000

A

#### Andrews

We are a batch (small) production company manufacturing number of turned parts for the automotive industry.Usually the batch quantity is 15,000 to 20,000 nos. This batch quantity will be completed in 2- 3 shifts (8 hr shift).

For special characteristics, we have defined that products will be checked 5 nos. per hour. All SPC manuals require atleast 20 subgroups to be taken before calculating control limits. 20 subgroups will take atleast 2 - 2 1/2 shifts. So we are able to use the control limit calculated for only 1/2 shift in some cases.

R

#### Rick Goodson

Andrews,

By your own numbers you produce between 625 and 1,250 pieces per hour. You have selected a time period of one hour and a sample size of five pieces. The basic concepts of SPC do not dictate the sample size or time between samples. A sample of three pieces taken at 10 minute intervals would give you 20 subgroups in slightly over three hours. In addition, you could look at some of the short run techniques such as the nominal X chart for runs of parts with similar specifications. You would have to look at the short run requirements such as similar standard deviations to assure they would work. Go to www.i-q-i.com for more information on short run SPC.

A

#### Andrews

Rick said :
A sample of three pieces taken at 10 minute intervals would give you 20 subgroups in slightly over three hours
Problem is in addition to special characteristic , we have a min. of 15 characteristics on a product.We check these characteristics 20 nos. in an hour. Therefore it is difficult to check three pieces at 10 minute intervals for special characteristics.

S

#### Sam

Actually the requirement is 25 subgroups. Also, "the level of initial process capability shall be determined to be acceptable prior to submission for all special characteristics . . . . ". Sounds like you may need approval from your customer.

C

#### Chemman

Andrews,

I also have a problem similar to yours. Several thousand pound batch of material produces roughly 3000 parts over 2 - 3 shifts. There are several physical tests that are performed downstream after oven curing and machining. Parts are set out for QA and by the time the tests are complete, all the parts are sitting in the audit area. Due to the nature of the process, length and expense of the testing, it is impossible to sample parts at defined intervals to establish a control chart for that batch. The parts needed for testing are all pulled at one time to represent that batch. What we end up with is a chart where subgroup to subgroup is a different batch of material, with lots of points showing out of control, but after the parts are already made and obviously no way to then react and bring the process into control. So I end up with a chart of 25 subgroups, all from different batches of material. I do not believe this is proper use of SPC, but I have a hard time explaining this to the customer who only understands if a point is between the dotted lines or not. Between the customer and the auditor, it is driving me nuts and I have yet found a way to work around this. Is there any other way to do SPC in this situation?

Thanks,
Chemman

G

#### Graeme

I have recently discovered a book that may be useful for gaining insights into this topic.

Statistical Process Control Methods for Long and Short Runs, Second Edition by Gary K. Griffith. (ASQ Quality Press, 1996)

I have only recently started to study this book, but it has already refreshed one key thing I had pushed to the back of the brain -- focus on the PROCESS, not necessarily the parts. The goal is to determine (and monitor) the capability of the PROCESS.

Graeme

Thread starter Similar threads Forum Replies Date
S Precontrol and Process Capability - CNC Lathes that run small batches - Short Runs Statistical Analysis Tools, Techniques and SPC 12
SPC Short Run Advice of a Stamping Process Statistical Analysis Tools, Techniques and SPC 3
M Standardized P Chart for Short Run Production Statistical Analysis Tools, Techniques and SPC 13
How to Demonstrate Stability and Repeatability in very Short Run Process AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 10
IMR (Individuals and Moving Range) Chart for Short-Run SPC - How much data to include Statistical Analysis Tools, Techniques and SPC 1
R What is a "DNOM Chart" in reference to Short Run SPC? Statistical Analysis Tools, Techniques and SPC 2
P Analysis of the figures from Dr Wheeler's 'Short Run SPC' Using Minitab Software 3
S Book for SPC Short Run - Recommendations Book, Video, Blog and Web Site Reviews and Recommendations 12
Short Run Cpk and Minitab Capability, Accuracy and Stability - Processes, Machines, etc. 7
Short Run SPC Chart Template needed Document Control Systems, Procedures, Forms and Templates 5
N Which is more appropriate Regular or Short Run control charting? Statistical Analysis Tools, Techniques and SPC 8
E How to Effectively Apply Short Run SPC Statistical Analysis Tools, Techniques and SPC 33
Short Run Charts - Sample size N=1 Statistical Analysis Tools, Techniques and SPC 2
K Short run Z-bar & W charts - Can anyone tell me the formula used? Statistical Analysis Tools, Techniques and SPC 9
M Multivariable Control Chart - Target, Short Run, Group charts, T2, etc. Statistical Analysis Tools, Techniques and SPC 10
Short run SPC Seminars? Statistical Analysis Tools, Techniques and SPC 1
T Short Run - Low Volume Cpk Calculation Capability, Accuracy and Stability - Processes, Machines, etc. 10
M Short Run SPC with Tool Wear Statistical Analysis Tools, Techniques and SPC 2
T PPAPs for job shops that produce short run assemblies (i.e 100 to 10,000 units) APQP and PPAP 9
L Short Run Mfg Seeking QS9000 Certification QS-9000 - American Automotive Manufacturers Standard 2
Definitions - Short-term and Brief exposure Occupational Health & Safety Management Standards 2
My short yet eventful stint as a regulatory affairs lawyer dude is coming to an end! Career and Occupation Discussions 1
Uncertainty of staging a short line scale standard on longer measuring machine? Measurement Uncertainty (MU) 4
How to systemically improve product quality in short-term and long-term basis? Preventive Action and Continuous Improvement 1
Short term vs Long term Capability - We ship millions of parts in a year Capability, Accuracy and Stability - Processes, Machines, etc. 7
Short Term vs. Long Term SPC Study - Where is Cp and Cpk Defined Statistical Analysis Tools, Techniques and SPC 8
R Height gauge to measure short hard to access heights General Measurement Device and Calibration Topics 3
D Balancing between Strategic Objectives & Short Term Priorities Quality Manager and Management Related Issues 2
E Short Case Studies - Major/Minor Nonconformance, Observation or OK? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 9
Sample Size for Short Term & Long Term Process Capability Capability, Accuracy and Stability - Processes, Machines, etc. 2
B Quality-related short term course in Perth Australia Coffee Break and Water Cooler Discussions 5
W Supply Voltage Condition for Transformer O/L and S/C (open & short circuit) testing IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
E Expiration Date on Label for different Countries (Short Shelf Life Product) ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 5
How to comply with ISO 9001 and provide quick/short lead-time orders? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 13
P Understanding IEC 60601-1:2005, Clause 8.1 b) - Short Circuiting Double Insulation IEC 60601 - Medical Electrical Equipment Safety Standards Series 13
H Looking for short videos that cover what ISO 9001 is Training - Internal, External, Online and Distance Learning 1
Are multi-faults needed? Effects of a Short Circuit IEC 60601 - Medical Electrical Equipment Safety Standards Series 7
Should the fault tests pass if temperature goes high in short time? IEC 60601 - Medical Electrical Equipment Safety Standards Series 15
S Aspect vs. Impact and Hazard vs. Risk - Short/clear explanation & example Miscellaneous Environmental Standards and EMS Related Discussions 11
S Pp/Ppk & Cp/Cpk - Which is appropriate for Long/Short Term Study? Statistical Analysis Tools, Techniques and SPC 20
D Short Quality Cases for my Quality Workshop so I can make a Case Study Quality Tools, Improvement and Analysis 10
E Error Proofing to prevent Length Short - CNC Turning Process Manufacturing and Related Processes 4
Short notice audits - Have you been through or triggered one? Registrars and Notified Bodies 4
R Short-term vs. Long-term Variation Six Sigma 5
Short Term and Long Term Quality Objectives AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 20
Gage R&R Short Study vs. Long Study vs. Other Studies Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 25
Injection Mold 100% Visual Inspection - Short Shots and Debris not being found Inspection, Prints (Drawings), Testing, Sampling and Related Topics 22
A Normal Deviation - short cut/method to calculate sigma Statistical Analysis Tools, Techniques and SPC 2
Interpretation of Short term vs. Long term Capability Studies Statistical Analysis Tools, Techniques and SPC 3
M Any Bridge Courses or short term courses available which helps the Career Training - Internal, External, Online and Distance Learning 3