Which control charts to monitor waste produced on the shop floor

E

eag65

#1
I would like to generate two control charts to monitor waste produced on the shop floor.

Situation 1
The first control chart is to monitor the amount of waste produced at a set up. Unfortunately, due to the nature of the process, set up waste in unavoidable. So I would like to generate a control chart to monitor the amount of set up waste produced and highlight special cause variation. I would like to do this by machine, by job.

I have a fair amount of historical data and the waste is weighed (KG’s) so it should be relatively accurate.

When I look at the data in mini tab it is non-normal and as one would expect it is very much skewed to the right as it includes common and well as special cause variation.

What control chart should I use? (I-MR?) and what do I need to do to the data in order to calculate the control limits please?

Situation 2
During the production run, we also produce ‘Run’ waste, which we also weigh at regular intervals. As the process is continuous, we report the total amount of KG’s waste against the total amount of KG’s made.

Again, what control chart should I use and how should I calculate the control limits using the data already collated? I thought of doing a p-chart but I’m not sure.

Any help would be much appreciated!
 
Elsmar Forum Sponsor

Steve Prevette

Deming Disciple
Staff member
Super Moderator
#2
I would like to generate two control charts to monitor waste produced on the shop floor.

Situation 1
The first control chart is to monitor the amount of waste produced at a set up. Unfortunately, due to the nature of the process, set up waste in unavoidable. So I would like to generate a control chart to monitor the amount of set up waste produced and highlight special cause variation. I would like to do this by machine, by job.

I have a fair amount of historical data and the waste is weighed (KG’s) so it should be relatively accurate.

When I look at the data in mini tab it is non-normal and as one would expect it is very much skewed to the right as it includes common and well as special cause variation.

What control chart should I use? (I-MR?) and what do I need to do to the data in order to calculate the control limits please?

Situation 2
During the production run, we also produce ‘Run’ waste, which we also weigh at regular intervals. As the process is continuous, we report the total amount of KG’s waste against the total amount of KG’s made.

Again, what control chart should I use and how should I calculate the control limits using the data already collated? I thought of doing a p-chart but I’m not sure.

Any help would be much appreciated!

Since your percentage is based upon weight, you should stick to I-MR or xbar-R. P-chart would be inappropriate because the P-chart is based upon a series of go-no go results. Your kilogram units don't match this situation - you don't decide if each kilogram is good or is scrap. An item scrapped may weigh a fraction of a kilogram, or many kilograms. IF you had a count of parts that we declared "good" versus sent back for "waste" you could do a p chart.
 
E

eag65

#3
Since your percentage is based upon weight, you should stick to I-MR or xbar-R. P-chart would be inappropriate because the P-chart is based upon a series of go-no go results. Your kilogram units don't match this situation - you don't decide if each kilogram is good or is scrap. An item scrapped may weigh a fraction of a kilogram, or many kilograms. IF you had a count of parts that we declared "good" versus sent back for "waste" you could do a p chart.
Hi Steve, thanks for the reply.

So I should use an I-MR in both cases then I take it. Do I need to do anything with the data in order to use it to calculate the control limits, as it has special cause variation in it and it isn't normal.
 

Steve Prevette

Deming Disciple
Staff member
Super Moderator
#4
As discussed in other threads here on the Cove, control charts do not depend upon normality for their operation. The I-MR will work fine with non-normal data for both cases.
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#6
if you are unsure of your results don't hesitate to post your data here with your questions...
 
Thread starter Similar threads Forum Replies Date
J Using P-Charts for Glass Manufacturing to Monitor and Control Attributes Statistical Analysis Tools, Techniques and SPC 2
S Use of Attributes Control Charts Statistical Analysis Tools, Techniques and SPC 1
U Electronic templates for making paper control charts Reliability Analysis - Predictions, Testing and Standards 2
Rameshwar25 Other types of Control Charts described in Chapter II of SPC Manual Statistical Analysis Tools, Techniques and SPC 6
S Standard Deviation Selection on Control Charts - Minitab "pooled deviation" Statistical Analysis Tools, Techniques and SPC 3
N Injection Molding - Median individual control charts Statistical Analysis Tools, Techniques and SPC 6
Chennaiite Do Attribute Control Charts really help? Statistical Analysis Tools, Techniques and SPC 9
B Setting Lower Control Limit on Attributes Charts Statistical Analysis Tools, Techniques and SPC 9
M Interpreting X bar and R Control Charts Statistical Analysis Tools, Techniques and SPC 2
M Large Sample Size - up to 32 - for Control Charts Capability, Accuracy and Stability - Processes, Machines, etc. 2
T Is the use of Control Charts Mandatory or Optional? ISO 17025 Requirements ISO 17025 related Discussions 6
E Minitab for hourly patient census - Control Charts Using Minitab Software 6
M On Subgroups in Control Charts and Process Capability Statistical Analysis Tools, Techniques and SPC 3
S Help with Table of Constants and Formulas for Control Charts Statistical Analysis Tools, Techniques and SPC 5
Q Monthly Data Review through Control Charts - Monitoring Complaints ISO 13485:2016 - Medical Device Quality Management Systems 3
R "Control" as used in 4.1 c) - Process Flow Charts (Process Sequence Chart) ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 12
D Suitability of Attribute Control Charts for ppm Level Control Statistical Analysis Tools, Techniques and SPC 6
R Metrology Control Charts for Reference and Working Standards General Measurement Device and Calibration Topics 6
D One-Two-Three Sigma Control Limits - Calculating Control Limits for X-bar Charts Statistical Analysis Tools, Techniques and SPC 3
bobdoering Myth or Mythunderstanding: Implications of the Economic Design of Control Charts Statistical Analysis Tools, Techniques and SPC 1
E Performance Charts - Purchasing Department and Material Control Department Preventive Action and Continuous Improvement 6
J Control Charts for 29 Devices that I tested Reliability Analysis - Predictions, Testing and Standards 10
J Control Charts with different Sample Sizes Reliability Analysis - Predictions, Testing and Standards 2
T why CPK <1.0 regarding two pieces of control charts of torque wrench? Statistical Analysis Tools, Techniques and SPC 2
R Electronic Templates for making Paper Control Charts Document Control Systems, Procedures, Forms and Templates 9
S Multivariate Control Charts in Chemical Batch Processing Statistical Analysis Tools, Techniques and SPC 7
G Control Charts - Plotting Unwanted Data Excel .xls Spreadsheet Templates and Tools 5
Y Control Charts + Ishikawa Manufacturing and Related Processes 26
N SPC Light Program - Easy way of Cpk extraction from multiple control charts Statistical Analysis Tools, Techniques and SPC 4
K Calculating Control Limits in Average and Range Charts Statistical Analysis Tools, Techniques and SPC 3
G Adjusted Control Limits - Usage of Control Charts Statistical Analysis Tools, Techniques and SPC 26
U P Charts - Subgroup Sizes? Process Control Indicator Statistical Analysis Tools, Techniques and SPC 3
J Control limits for one sided control charts using WECO rules Statistical Analysis Tools, Techniques and SPC 5
T Rules for interpreting control charts Statistical Analysis Tools, Techniques and SPC 2
G Control charts of finished product characteristics..NonSense? Statistical Analysis Tools, Techniques and SPC 8
D Control limit calculation (Xbar R charts) using Minitab Statistical Analysis Tools, Techniques and SPC 14
H How to create Stoplight Control charts with excel? Excel .xls Spreadsheet Templates and Tools 16
S Calculating 1 sigma and 2 Sigma limits in Control Charts Statistical Analysis Tools, Techniques and SPC 1
M Control Charts - Points TOUCHING Limits = Stable? Statistical Analysis Tools, Techniques and SPC 12
T What is Average Run Length & Average Production Length when used in Control Charts? Statistical Analysis Tools, Techniques and SPC 4
T Using SPC Control Charts to Reduce AQL Sample Size AQL - Acceptable Quality Level 16
B Recommendation for a book to Explain Control Charts Book, Video, Blog and Web Site Reviews and Recommendations 6
C Designing Control Charts - Variable with Small Variation and Tight Control Limit Statistical Analysis Tools, Techniques and SPC 20
K Understanding Control Charts Methodology for Attributes like Plug Guages. Statistical Analysis Tools, Techniques and SPC 1
J Selection Procedure for the Use of Control Charts (Apendix C) Statistical Analysis Tools, Techniques and SPC 2
B Reaction to Out of Control SPC Charts Statistical Analysis Tools, Techniques and SPC 14
J Run Charts and Alternative Process Control Parameters Statistical Analysis Tools, Techniques and SPC 5
Steve Prevette Example SPC Control Charts posted by the Department of Energy EFCOG Statistical Analysis Tools, Techniques and SPC 1
B Why is the Mean preferred over Median in Control Charts? Statistical Analysis Tools, Techniques and SPC 12
R 100% Control and Control Charts Statistical Analysis Tools, Techniques and SPC 4

Similar threads

Top Bottom