Non-Destructive Joint
Test MethodProject 05100
Non-Destructive Joint Test Method
Equipment Development
Preliminary Design Report
Project 05100 Design Team
Aleksandra Soldo – IE – Team Leader
Lauren Williams – IE
Joshua Chan – ME
Robert Lefferts – ME
Elizabeth A. Kesel – ME
Jason Mitchell –EE
Thinh Cao – EE
Executive Summary
Delphi Thermal & Interiors makes heater cores that are found inside many automobiles. They have a high standard of quality. A part failure further down the line at Delphi’s customers manufacturing facility costs hundreds of thousands of dollars. A leak while in use requires an extensive repair process and causes great inconvenience to the customer. Given this, they strive for 100% of the parts that leave their plant to be reliable for the life of the part.
There are several factors that may cause a bad part. The clinch that attaches the inlet and outlet pipes to the cores is a possible source of problems and will be our main focus. Delphi does not understand what pressure and temperatures different clinches can handle when in use. Delphi does not measure clinch on 100% of their parts. Parts are measured 4 times a shift by hand. Optimization of their parts and processes may lead to better quality.
In order to aid in quality improvement, the senior design team will research and recommend a method of accurately measuring the clinch. The measurement system will allow Delphi to measure clinch on 100% of their production heater cores. Measuring the 100% clinch will ensure that parts with out of specification clinches do not reach the customer. Also, the design team will run a series of tests to determine the relationship between clinch, temperature and pressure.
The overall goal of the project is to give Delphi the information it needs to improve first time quality, as well as the overall quality of products they provide to their customers.
Table of Contents
Executive Summary
Table of Contents
1.0Needs Assessment
1.1Mission Statement
1.2Project Description
1.2.1Project Background
1.2.2Causes of Leak Test Failure
1.3Parameters
1.4Stakeholders
1.5Key Business Goals
1.6Financial Analysis
2.0Concept Development
2.1Correlation Testing
2.1.2Test Analysis
2.2Measurement System
3.0Feasibility
3.1Clinch Measurement System Feasibility Assessment
3.2Testing Feasibility Assessment
3.3Feasibility Conclusion
3.3.1 Correlation Testing
3.3.2 Measurement System
4.0Future Plans
5.0Conclusion
References
Appendix
Appendix A – Assembly Process Map
Appendix B – Fish Bone Diagram
Appendix C – Brainstorming Concepts
Appendix D – Test Plan
Appendix E – Gantt chart
Appendix F – Work Breakdown Structure
Appendix G – Dependency Matrix
Appendix H – First Cut Objective tree
Appendix I – Revised Objective Tree
1.0Needs Assessment
1.1Mission Statement
The purpose of this senior design team is to help Delphi Thermal & Interiors improve the quality of their heater cores by providing them with a better understanding of the clinches found on each heater core, as well as a production environment test method to ensure the integrity of the part.
1.2Project Description
1.2.1Project Background
The scope of the project was described to us by Delphi as:
Develop a non-destructive test method and equipment/tools for verification of the long term integrity of the clinch portion of a heater core pipe to neckshell assembly for an assembly process in a production environment.
- Understand/Define the correlation between joint integrity (mechanical joint and leak portion) and the pressures & temperatures at which they leak. Develop a test method for production environment.
- How to accurately measure clinch.
Delphi provided us with background information as well as specifications with which to work with. Delphi Thermal & Interiors has been using this clinch method of assembling inlet and outlet pipes with heater cores for over 20 years. The clinch itself has a spec of 2 mm (fig. 1-1) that it must meet in order to pass as a good part. The clinching process is applied to the neckshells of various models of heater core units (fig. 1-2).
The clinch is used to mechanically prevent the pipes from displacing out of the neckshell under pressure. An o-ring is placed on the pipes to provide the seal. The joint is achieved by clinching one end of the pipe to neck-shell which is preassembled to the core by a brazing operation.
This assembly process takes place on one assembly stand. The assembly process map (Appendix A) shows the flow of processes. The operator completes the first 3 steps of the process. The rest of the process is automated.
- A heater core is placed into the fixture.
- O-rings are placed onto the inlet and outlet pipes, pipes are then placed into the fixture.
- The operator cycles the stand.
- Pipe hold-downs extend and exert between 80 psi -100 psi of pressure to press the pipes into the neckshell.
- Three clinch jaws for each pipe extend to a hard stop and clinch the neckshell over the pipes.
- Test heads extend into the pipes. A leak test (pressure decay) is performed. Parts that pass are advanced to the next process while failed parts are scrapped.
Currently the only test in place is the leak test. Clinch is not measured 100%; rather an audit check is performed 4 times a shift by an operator with feeler gauges.
Delphi currently produces roughly 16,000 heater cores a day. Very few bad heater cores are produced daily. First time quality is very good. One of the main concerns of Delphi is heater cores failing after they leave manufacturing and arriving at the customer. Although the occurrence of the issue is infrequent, any such incident is not cost effective for Delphi. Measuring the clinch on every shipped heater core will allow us to ensure the integrity of each joint.
Lab testing will be performed to gain a better knowledge of the relationship between different clinch gaps and what pressures and temperatures caused them to leak. This knowledge will allow our team to make recommendations to Delphi regarding changes to their production process and/or product design.
1.2.2Causes of Leak Test Failure
Various factors can cause heater cores to fail leak testing. The fishbone diagram located in Appendix B lists many causes of leak failure. The “5 Ms” (Material, Machine, Man, Mother-nature, Methods) were used to group possible causes.
Non-conforming material is a cause of leak. Components that are out of spec damaged or contaminated can cause heater cores to be assembled incorrectly.
Machines play a big part in the assembly process. Malfunctioning production tools will lead to incorrectly assembled parts. The clinch jaws and pipe hold down tool are set to clinch at a certain pressure and to travel to a certain position. Any change in that will lead to out of spec. parts.
The other part of the assembly process is performed by an operator. Operators place the heater cores and pipes into the fixture prior to clinching. Operators are also in charge of o-ring installation. Any variation from standard procedure (such as incorrect placement of the pipes and/or heater core, forgetting to install an o-ring, installing more than one o-ring per pipe) can cause out of spec parts.
Weather plays a big role in determining whether heater cores pass or fail leak test. Since the production leak test is pressure decay, a change in temperature will cause a false leak reading. Air density changes as temperature changes; pressure decay does not take this into account. Large temperature changes in the plant will lead to a spike in failures.
Whether a heater core passes or fails leak test relies on its measurement system. Malfunctioning or uncalibrated measurement equipment will cause false leak readings.
1.3Parameters
Clinch Measurement System
- The clinch measurement method must be non destructive.
- Must be applicable to the HC 340 and all heater core assemblies.
- The cost of equipment must not exceed $75,000.
- Must meet operator safety requirements.
- Must be ergonomically acceptable for the operator.
- Must be integrated within the planned assembly/test process.
- Test must be conducted within cycle time of production assembly (~20 sec).
- Must not adversely affect performance of joint or heater core assembly for use by the customer for the life of the product.
- Must be in production by April 2005.
- Test equipment must pass MSA (measurement systems analysis).
Correlation Testing
- Statistical proof of clinch vs. leak correlation.
All parameters that were given by Delphi are all feasible. We should be able to meet all of their specified parameters for both clinch measurement method and correlation testing.
1.4Stakeholders
The main stakeholder in this project is Delphi Thermal & Interior. Delphi will use the information gathered in this project to alter their manufacturing line and produce higher quality products.
1.5Key Business Goals
The first goal to be accomplished is to define a successful correlation between pressure, temperature, clinch gap, and leak. Once this correlation is found, the project will be successful if a way to monitor these properties during production is designed and tested on one manufacturing line.
1.6Financial Analysis
A $75,000 budget has been granted by Delphi for this project. The testing itself will be a low cost, if any. The majority of the money for this project will be used for the monitoring system for the clinch test stand. The financial breakdown for two possible measurement systems is as follows:
Part #LV-H37 Series (Laser Measurement System)
- Approximate Cost: $40k-60k
- Reason for variation due to different types of lasers and sensors
Part #CV-2100 Series (Camera Measurement System)
- Approximate Cost: $16k-22k
- Reason for variation due to different types of cameras, lenses, and lighting schemes.
2.0Concept Development
Group brainstorming allowed the design team to come up with various concepts for both of our objectives; correlation testingand clinch measurement. See Appendix C for a list of brainstorming concepts.
2.1Correlation Testing
The objective of this testing is to determine the relationship between clinch gap and leak on the heater core. The factors we are concerned about are pressure and temperature. The heater cores are exposed to operating pressures of 4 psi – 40 psi, as well as operating temperatures of 195° F – 240° F. A test plan (Appendix D) was formulated to include operating pressures and temperatures.
A major problem that we ran into was where we would perform this testing. A couple options were determined to be reasonable. Delphi Thermal & Interior was one of our obvious options as well as using RIT’s resources. RIT’s on campus Remanufacturing Facility happened to have a leak fixture setup that would be accessible to our team. A third option that was thought of was creating our own leak stand. A last option was using Delphi Energy & Chassis’s resources here in Rochester.
The testing concept was agreed upon by all the team members. Where our testing would take place needed assessment. Our testing location was selected using a feasibility assessment.
2.1.2Test Analysis
Once testing is completed, there will be an extensive set of data with the independent variables temperature, pressure and clinch gap and the response variable of leak rate. If possible, markings on the neck shells and presence or absence of oil on the o-ring will be included as factors as well. Regression analysis will relate the variables. The team will report to Delphi the maximum pressures and temperatures that correspond to a certain leak rate for a certain clinch gap. A request for about 30 random heater cores that are known to be good has been submitted. This sample will take some time to test. The power and confidence of the tests will be determined after the testing has been completed, and all conclusions will have to be interpreted in this light.
There are several possible sources of variation while testing. Holding the temperature constant while doing pressure testing may present a challenge. The team will attempt to counteract this by affixing thermocouples to the core and making note of the temperature at the time of testing. Also, if needed, the core will be placed in the oven again for reheating.
There is the possibility of the testing process showing less variation as time goes by due to the learning curve. The data will be tested for these effects at the analysis phase.
2.2Measurement System
The purpose of the measurement system is to measure the gap between the clinch and the pipe on the heater core. The factors involved with measuring the clinch gap are: repeatability, reliability, accuracy, and time. The main objective is to measure 100% of the heater cores on the assembly line at Delphi – Thermal & Interior. Because of the high production schedule, there is a very limited amount of time for an accurate measurement of the clinch gap. It is essential that the system be highly reliable to keep the production time of the heater cores to a minimum
There were four different measurement systems suggested. The first system suggested was by measuring the tool travels of the jaws that clinched the neckshell. The second system was a camera system that will take an image of the clinch and then calculate the gap width. The third system was a laser system. The lasers would reflect off of the neckshell and the width of the beam would be measured. The last method suggested was to use X-rays to obtain a clear picture of the clinch.
3.0Feasibility
3.1Clinch Measurement System Feasibility Assessment
1 (Low) / 2 / 3 (Med) / 4 / 5 (High)Camera / X
Laser / X
Tool Travel / X
X-ray / X
Feasibility Chart:
Rationale for each System:
Camera: The system is designed to measure gap at a high accuracy. Camera system is already designed and built.
Laser: System can precisely measure gap of clinch. Laser system already designed and built.
Tool Travel: System to measure the travel of the clinch tool. The system would be simple to implement. System would be inexpensive to design and build.
X-ray: System would give good image of clinch gap.
Problems and Remedies / Required Action for each System:
Camera: Pipe coming out of heater core might block image of all three clinches. The system needs to be tested with clinched heater cores to determine repeatability of tests. System is expensive.
Laser: Possible reflection problem from gap. The laser beam might not reflect properly due to the high reflectivity of the heater core. The system needs to be tested with clinched heater cores to determine repeatability of tests. System cost could be greater than budget.
Tool Travel: The current fixture does not hold the heater core securely in place, causing the heater core to sometimes move in the fixture. This movement causes inaccuracy in the tool travel. The fixture is currently being redesigned by Delphi to eliminate this problem.
X-ray: The system would require a large machine and the production time would not comply with the specified production time required to be viable for mass production. Also, the gap of the clinch would not be easily measurable.
3.2Testing Feasibility Assessment
Rationale for each system:
DelphiLockport: This option is already set-up for the testing that we would be emulating. With the test set-up already done, there is virtually no cost for this testing.
DelphiRochester: The facilities for testing are easily accessible and have the capabilities to measure leak. This set-up requires only slight modification` at a minor cost.
REMAN Facilities: The facilities used for this testing are highly accessible.
Design a Stand: Capability to build a stand that can meet all of our needs.
Problems and Remedies / Required Action for each System:
DelphiLockport: This facility is not easily accessible and does not record or display the exact leak measurement.
DelphiRochester: Requires some set-up time and some minor modifications.
REMAN Facilities: The overall system is not set-up for our needs. Reasons are that the fluid medium is water instead of air, and would require major modifications, which is not time and cost effective.
Design a Stand: This situation is highly ineffective in regards to time and cost.
3.3Feasibility Conclusion
3.3.1 Correlation Testing
In order to meet Delphi – Thermal & Interior’s needs to find a correlation between the leak and the clinch gap measurement, a decision was made based on the feasibility assessment conducted. The team has decided that the most feasible test method is the use of the Delphi facilities in Rochester. The accessibility of this facility is high, which aids in making it the most time effective because there is a high reduction in travel time. Also, the method chosen has a very miniscule cost associated with it when considering all the factors involved. There is very little modification done to the Rochester test facility as compared to the other options, which also is very cost effective. As you can see from the above chart, this test method scored the highest which shows that it is highly feasible.
3.3.2 Measurement System
If a legitimate correlation can be found between leak rate and clinch gap, a measurement system should be used to constantly monitor clinch gap on the manufacturing line. We will be using a camera measurement system by Keyence. The following is a list of camera specifications:
Part #CV-2100 Series (Camera Measurement System)
- Digital Image transfer
- Repeatability of ±0.05 pixels
- Ultra-high-speed processing of 20,000 parts/min.
- On-screen statistical data processing
- Edge area correction
- Trend edge function
- High-speed rotation search
This camera system will be mounted on the clinch stand and measure the clinch gap of each heater core that goes through the assembly. The camera works by taking a snapshot and counting pixels to measure the clinch gap. The number of pixels that is measured between the clinch and the pipe is then converted to millimeters by the camera system. This measurement is then compared to the 2 mm gap specification. Originally, we planned on using only one camera per pipe, but due to obstructions caused by the pipes, two cameras per pipe are required to accurately measure all three clinches.