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Doe As Process Control Introduction

Jun 12, 2015



Process Control Basics taught by the discipline needed to run a successful DOE

  • 1. Using Designed Experimentation as a practical introduction to Process Control in a Thermal Spray Shop
    Kelly D. Brown, Ph.D. MBB
    Avalanche Process Improvement, LLC
    John Sauer, PE
    Sauer Engineering
    September 10, 2010

2. Process Control in 2 Parts
Part 1 Process Control Concepts and example of Thermal Spray troubleshooting with Root Cause Analysis
Part 2 Advanced Process Control using Designed Experimentation (DOE) in a Thermal Spray operation
3. Process Control Concepts for a Thermal Spray Shop
Model TS Shop Process
Spray Part
Metrics are a product of the process design, measures and inputs and outputs used to spray parts.
Measures Part quantity, specifications, part prep, and more
Metrics Production output, cycle time, quality, and more
Process Inputs Gas flows, current, voltage,
Process Outputs part temp, film thickness, microstructure,
Process Design arrangement of the process steps
4. Thermal Spray Shop Controls
Model TS Shop Process
Spray Part
Process Control Facts - 1
Problems can result from errors in Measures, Inputs, Outputs, or Metrics.
Problems can be caused, hidden, repaired by Process Design
Outputs become inputs for downstream processes
Problems with inputs expand, or can go underground
Process design usually determines the speed and throughput of the shop
Process inputs and outputs usually determine quality ofpart
Poor quality spills over as a speed and throughput problem
5. Thermal Spray Shop Controls
Model TS Shop Process
Spray Part
Process Control Facts - 2
Processes operate with inputs and outputs
Problems are generally reported as metrics
Root cause of process problems not resolved with metrics
Must locate problem in the process to formulate best solution
6. Root Cause Analysis aka,RCA or 5-Why analysis.
You keep asking Why? until you are exhausted!!!
An experienced facilitator can help your organization learn to do 5-why right
First Step Root Cause Analysis
Define the Problem
Define the Process
Start asking why until one or more actionable causes are determined
Generate permanent corrective actions
Document and track results
7. PROBLEM:50% failure rate from inconsistent large un-melts found in T800 coatings
Using Root Cause Analysis to Identify Best Fit Solutions & DOEs
Powder ?
Root Cause Analysis (5-Why) as tool to focus potential DOE improvements

  • Not all problems need DOE to resolve

8. Orient DOE testing in area likely be responsible for failures 9. Manage resource to resolve most important challenges firstSpecs?
10. RCA: 5-Why Analysis of T800 failure with Actionable Solutions
2. Incorrect Spray Parameters?
3. Powder Surging during Plasma Spray
Model TS Shop Process
High percentage of 006G & 006S microstructure unmelts
Insufficient heat to melt large particles
Specifications not available on floor
Need production right away
Spray Part
1. Specifications not acknowledged by vendors
Unmelts and Oxides
Good materials are not available
Large Particles visible in Micrographs
Engineering validation OKs particle size variance
Vendors not asked to fix problems
Large Particles in Powders
11. Problems Need The Right Team
What You Can Do Depends on What Team You Are On
Design(Owned by Management / Engineering)
Equipment SelectionProcess Steps / Sequence
Shop Measures (Owned by customer)
SpecificationsQuantity / type of parts
Process Inputs(Owned by Management / Engineering)
Gas flowsPower settings
Gas pressuresPart setup
Process Outputs (Controlled by design, measures and process inputs)
Metrics( Owned by Customers / Management)
ThroughputQuality / Speed
12. RCA Results Multiple Problems
Problem Location determines solution type
Insufficient heat to melt large particles
1. Powder Size Problem:
NOT DOE Process Design Problem, possible problem with specifications
Change process design & resolve issues with vendors / specifications
1. Specifications requirement not delivered by buyers
2. Spray Parameter Problem:
DOE Process Input Problem,
Unmelts canresult from low particle temperature and velocity, driven by spray parameter inputs
2. Incorrect Spray Parameters?
3. Powder Surging Problem:
PossibleDOE May be related to maintenance or to powder delivery and gas flow settings
3. Powder Surging during Plasma Spray
13. Thermal Spray Inputs & Outputs
How many of these parameters to you monitor in your shop?
What are the best setting for T-800?
Will more than one set of parameters work well for T-800?
What is the optimal settings for T-800, or any other coating?
How would you go about finding the best settings?
DOE is the ideal tool for answering Thermal Spray questions like these with known certainty
14. More Process Control facts for Thermal Spray Shops

  • Broken equipment produces broken results

15. Process design inputs must be held constant if you want a consistent outcome 16. You can see a lot more than you can measure 17. You already know a lot more than you use about your process 18. Not everything that you can measure is important 19. Many important things are difficult to measure 20. Good measurements require skill, repeatable measurements discipline 21. Environmental noise in your shop every day. It is not a LAB! 22. There are many possible parameters but a few are stronger than the rest 23. If strong parameters are set correctly, minor parameters are easier (sweet spot) 24. Parts that closely related can be processed with similar or the same process parameters 25. Some technologies are easier than others. 26. Sometimes you get lucky, but your customers are not big fans of luck.

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