2Life Testing Overview What is Life Testing? Life Testing in OrganizationsHow Does Life Testing Work?Who Uses Life Testing?Motorola’s ProcessPaper Clip Life TestingSummary
3What is Life Testing?A process done under controlled conditions to determine how and when a product will fail in its intended environmentImproves a product’s reliabilityFinds the weakest and strongest points of a productThis test is done before any products enter the market. Once the weakest and strongest points are found, the testing determines how the product will be redesigned to fix the failures found during the testing.Information Found from:
4Life Testing in Organizations Design Life Cycle:Have an ideaDesign itMake a prototypeFinal definitionDesign and evaluationimplementationProducts want to be entered into markets fast. For a product to make it to the market fast, Life Testing or Accelerated Life Testing needs to be implemented. The design cycle helps show that life testing should only be done with a prototype. It takes a shorter time period to make a simple prototype and test that rather than make an entire batch. Making an entire batch will increase costs, and if there is vast amount of failures the entire batch will be useless.
5Life Testing in Organizations Life testing design cycle:Idea Design PrototypePrototype is tested for failuresDesign cycle stops with prototypesAlthough it is not the entire design cycle used when tested, in the end each step will be followed. The tests done to the prototype will re vamp the finial design.
6Life Testing in Organizations Customers believe that quality is inherent is all productLife testing validates this assumption.Specific directions are followed in a uniform fashionLife testing allows a product exist without failures. To find valid data that can help make the product better, failures have to be induced. A consistent set of instructions are performed each time a prototype is tested. At each stage of the process it must be documented what was done and how, so upon completion the product can be redesigned.
7Three Types of Tests Type of tests performed: Qualitative Tests ESS (Environmental Stress Screening)Accelerated Life TestingAll three of these type will usually be used with different products. A test is done to see what type of test should be used on a particular product.
8Qualitative Tests Gives the product tested the most failures Failures produced by high and low stressesTo pass the product must live through the entire test without failure ¹As a prototype the product may not be designed as intended by the blueprints. This test could make a product break or fail if it is tested beyond the means it is intended for. For the test to be effective, it should allow the product to meet what it is expected to meet when put on the market. To test for something it is not going to encounter could be costly and inefficient. As the definition states, it is to be tested for its intended environment.Footnotes:1.
9ESS-Environmental Stress Screening Applies environmental stimulus to productsGoal: ¹To find latent defects and eliminate themTo find defects not found with inspection or electrical testingESS is usually the test that is used on electronic or electromechanical products.Footnotes:1.
10Accelerated Life Testing Similar to Life TestingTesting moves at a faster paceUses quantitative dataEnd results yield times-to-failure dataTimes-to-failure: how long it takes till a failure is madeStandard Life testing is not used as much any more because it is so time consuming. Accelerated Life testing is a more recent technology. The reason is that it makes the times-to-failure happen faster and can get the product fixed and out on the market. Example: You will not expect a new dishwasher to fail in the first year but if it fails twice in ten years accelerated life testing was successful. It is successful because life testing will fix the failures a product is supposed to encounter but not all.
11Accelerated Life Testing Life distributions show how fast a product will fail ¹Two methods used to get times-to-failure information:Usage rate accelerationOverstress accelerationFootnotes:1.
12Usage Rate Acceleration A test used for products that only operate for small amounts of time ¹It increases the time to make failures happen quicker than if it were used normallyFootnotes:1.
13Overstress Acceleration Backup to usage rateUsed if usage rate is not appropriate means ¹Tests products that are constantly usedUses stress levels that it would not normally encounterDefects that are found in accelerated life testing are found from low and high levels of stress and cold temperatures. Testers also are required to use high humidity, high heat, pressure and vibration. Many other techniques are used. The same basic idea is conveyed, that they need to break the product in turn to make it better. All things done with accelerated life testing is done faster than normal.Footnote:1.
14How Does Life Testing Work? Majority of tests done on small sample4 to 6 unitsBegin test with lowest level of the productFailures must be documented as they happenSince such a small sample is tested, the testers do not want to destroy all prototypes. Therefore to test correctly, the least destructive test is performed first and then the stress or whichever method used is increased. Soft failures will not show up if you continue to move on with test. As the test happens and failures are found documentation will help find failures that the tester could have overlooked.
15How Does Life Testing Work? Soft failures occur when there is damage made but the product returns to its normal stateHard failures are permanent damages done to the productFor More Information go to:
16Margins and Reliability The difference between soft and hard failures is the margin for stress ¹Once the failures are found and fixed, the margins have reached their maxMaximized margins increase reliability and the life of the productFootnotes:1.This figure shows the stress and its number of failures. The curves represent the distribution of failure that is responsible for that limit. This is a good imitation of a large sample instead of 4 to 6 units. The reason is because the failure will be detected and as long as it is detected then it does not matter where. As soon as the curves move toward the operating margin then the failure is considered an out of box failure.
17Who Uses Life Testing? Motorola Mission to produce cell phones with “virtually no defects”Use accelerated life testing to accomplish missionHelps to validate their six sigma corporate standardMotorola has their own reliability engineering department. Once that department believes that the product meets and or exceeds customer satisfaction then they will sell to the market.
18Motorola’s Process Determine environment Perform life testing in all environments.Four to six weeks of testing is required ¹Motorola uses accelerated life testing with their products. It is based on Standard rules of life testing.Footnotes:1.
19Motorola’s Process Drop Testing ¹ Hot and Cold Temperatures ² Samples are dropped on different surfaces of the phone multiple times.Hot and Cold Temperatures ²The phones receive extreme temperatures of hot and cold.Testing simultaneously with audio quality and simulated callsFootnotes:1.2.
20Motorola’s Process Electro-Static Discharge ¹ Dust Exposure ² Zap products with an electric pulse at “discharge” pointsDust Exposure ²Products are placed in dust chamberDust is shaken all over the product and then left to settleThe “discharge” points are jolted with thousands of volts of electro static discharges. A discharge gun is used to shoot the charges into the holes of the product.Footnotes:2.
21Motorola’s Process Vibration Testing ¹ Horizontal and vertical vibration testing.Placed into vibration table and controlled by testerThe tests vary in the extremes of vibrations givenDuring the test it places a call and must be stable throughout the processFootnotes:1.
22Motorola’s Process Environmental Aging Tests ¹ Certification Testing ² Temperature cycling: moving from low to high heat and coldTemperature shockCertification Testing ²Sudden Impact TestingEndurance TestingPackage Drop TestingTransport SimulationFootnotes:2.
23Motorola Summary Life testing cuts Motorola’s costs Less return of products that fail for the customerTheir design exceeds customer satisfaction with “virtually no defects”
24Paper Clip Life Testing Follow these directions to determine how fast a paper clip will break using the life testing methods. ¹Footnotes:1. Reliasoft.com (2001). "http://www.weibull.com/AccelTestWeb/paper_clip_example.htmIn , Tucson, Arizona
25Follow These StepsWith one hand, hold the clip by the longer, outer loop.With the thumb and forefinger of the other hand, grasp the smaller, inner loop.Pull the smaller, inner loop out and down 90 degrees so that a right angle is formed as shown.All of this information is from:Reliasoft.com (2001). "http://www.weibull.com/AccelTestWeb/paper_clip_example.htmIn , Tucson, Arizona
26Follow These StepsWith one hand, continue to hold the clip by the longer, outer loop.With the thumb and forefinger of the other hand, grasp the smaller, inner loop.All of this information comes from:Reliasoft.com (2001). "http://www.weibull.com/AccelTestWeb/paper_clip_example.htmIn , Tucson, Arizona
27Follow These StepsPush the smaller inner loop up and in 90 degrees so that the smaller loop is returned to the original upright position in line with the larger, outer loop as shown.All of this information comes from:Reliasoft.com (2001). "http://www.weibull.com/AccelTestWeb/paper_clip_example.htmIn , Tucson, Arizona
28Follow These Steps This completes one cycle. Repeat until the paper clip breaks. Count and record the cycles-to-failure for each clip.For this particular example, the larger size paper clips were demonstrated. Different sized paper clips will give different information. Throughout the life testing cycle of the paper clip be careful to use the same stress each time through.All of this information comes from:Reliasoft.com (2001). "http://www.weibull.com/AccelTestWeb/paper_clip_example.htm, Tucson, Arizonaweibull.com is part of Reliasoft.com who made Weibull ++ 6 for Life Data Analyses which sets the standards for Reliability Life testing.
29Summary Quality is inherent in most products Life Testing allows the consumer to have reliable information because it is consistent throughout the testingSome life testing can cause permanent damage, and some aspects of the testing do notPrototypes are used to test because it is cheaper and easier to run tests on samples
30Summary Life Testing can be done with ease or tremendous detail Any way it is done it will yield the same informationThe tester must document what and how they do thingsThree sources I used: