Contributed by: Sciemetric Staff
Leak testing is often an art as much as it is a science. Manufacturing quality engineers and machine operators must contend with many external factors that can undermine accuracy and repeatability. On today’s factory floor, digital process signature (or waveform) analysis, coupled with powerful applications for big data analysis and visualization, can be used to eliminate much of the uncertainty and guesswork that plagued leak testing in the past.
The waveform, or digital process signature, of a manufacturing process or test cycle is like a complete video replay of a crucial event as it happens, versus just a few snapshots.
Take a hockey game with your favorite team on the ice. A contentious goal is scored and the referees go upstairs for a review of the play to decide if the goal will count. Now, what would you prefer as the basis for that decision – a video instant replay or snapshots of only a few isolated points in time as the puck passed through the goalie’s crease?
Using digital process signature data
A digital process signature is that full replay, while scalar data offers only a few snapshots.
By collecting the signature from every test cycle into a central database, you now have an archive, traceable by serial number, that can be used to drive the reliability and repeatability of your leak test. Below are a few ways to lever this data.
Create a histogram
Signatures can be converted into a histogram of leak rates to show the waveform for a good part and the range of acceptable deviation. This makes it easy to create and visualize a baseline against which to compare all parts. The more signatures you have, the easier it becomes to understand what waveform anomalies to watch for and what they signify. In addition to distinguishing good parts from bad, you can also spot problems with the test station itself.
Use a mapping exercise
Mapping involves taking a few known good parts and running them through the test station 20 times each to create a baseline. Specific defects, flaws or even test station setup problems are then introduced to see if and how they show up in the resulting test data. This takes the guesswork out of determining which limits to set to catch specific issues.
Do your math
Apply mathematical techniques directly to the process signature in the form of a “feature.” Applying post-processing features such as Slope, Peak to Peak values, Mean and Standard Deviation will help to quantify sections of the signature for further analysis.
If a part comes back from the field with a leak-related warranty issue, you can draw on your archive of leak test data to trace root cause. Use the warranty claim as an opportunity to drive continuous improvement.
Get to the bottom of that warranty claim
Check to see if there was anything off about the problem part’s original leak test signature, even within the range of standard deviation. And look at the signature data from the other processes upstream that touched the part – sometimes, a problem just doesn’t show up at the leak test station. Run the problem part through the test again to see how its signature compares to its original test. Lastly, create an algorithm to screen your archive of signature data for that type of part to see if any others have the same anomaly.
Get the full scoop in our free e-book: 7 steps to a better manufacturing leak test
We explore these and other best practices to boost the performance of your leak test in our e-book, “7 practical steps to a better manufacturing leak test.” What you will learn in this e-book:
- 1. 5 things to check to get the setup right: Even the best digital technology to make a leak test smarter won’t help if the test station suffers from mechanical issues.
- 2. How to address these 4 details to ensure repeatability: Tackle the culprits responsible when a leak test must be run a second time to get a pass, or results differ between repeated tests.
- 3. What to look for in the data: Understanding what digital process signature analysis can tell you.
- 4. The fastest way to set the right test limits: Use that signature data to find the sweet spot for quality so your test cycles are not a second longer than they need to be.
- 5. 6 tips to shorten cycle time: Use manufacturing analytics to focus, refine and chart the impact of the changes made by your team to make your leak test faster.
- 6. 4 ways to keep your leak tester honest: Trust your test station is optimized by using a master part and employing the right verification procedures.
- 7. Using warranty claims to drive continuous improvement: Historic signature data is key to limit recalls and minimize the financial and public relations impact.