Quasar 4000 Applications FAQ
1. What are the basic limitations of the Quasar method?
The part being tested must be stiff enough to resonate. Most metal and ceramic parts can be tested. Assemblies are sometimes capable of being reliably tested, depending on the design and defect. Quasar offers a no-cost feasability testing service to quickly resolve this question.
2. How small a defect can Quasar find?
Quasar doesn't find defects - it rejects defective parts. Defective parts are those that will fail prematurely in service. That means that Quasar can identify and reject parts that are weaker than the good parts. As an example, consider a part type whose specified minimum strength is 5000 pounds and for which the strength of acceptable product is 5000 to 8000 pounds. If the part has a defect indication but still has a break strength over 5000 pounds, Quasar will not fail it. At the same time, if the break strength is 4000 pounds Quasar will fail it, even if there is no defect indication.
3. Do you identify defect type or location?
No, Quasar only determines whether the part is structurally sound. It cannot determine defect type or location.
4. Do Quasar systems ever fail to perform? Why?
If the application is appropriate, the Quasar system will perform. On occasion however, applications are considered failures. This happens for one of two reasons. First, the Quasar method may be misapplied. For example, Quasar may be expected to reject parts for cosmetic reasons, based on "indications." Since an indication may or may not signal an actual defect, Quasar frequency will not classify this same part to be defective. Second, any Quasar system unsupported by management will fail. While Quasar systems are designed to minimize maintenance, like any other piece of plant equipment, it must be properly maintained and operated by qualified personnel.
5. If we implement Quasar, can other NDT processes be shut down?
If the purpose of the other NDT is to reject defective parts, then Quasar should be able to replace it. However, if the purpose is to reject parts for cosmetic reasons, Quasar will not replace it.
6. What physical condition do the parts have to be in to be tested? For example, can parts be tested with cutting fluid or mold release on the parts?
There are three conditions required for Quasar testing. First, the parts should have major flash removed (some flash is acceptable, this should be discussed with the Quasar representative). Second, the parts should be dry, or at most damp - not wet. Third, the parts should be at a stable temperature between 5 and 55 degree centigrade. The actual temperature is not critical but the parts should not be changing temperature during the test.
7. What amount of part-to-part weight differential can Quasar handle?
Quasar has successful applications where the part weight varies up to +/- 5%.
8. Are there size limitations for the Quasar method?
Theoretically, there is no limit, but there are practical limits established by part geometry, defect type and relative size, and material handling. The largest parts tested currently are engine blocks that weigh up to 150 pounds (70 kg). The smallest are ½ inch ceramic balls.
9. Can Quasar be used on gray iron?
Some gray iron is stiff enough to resonate well, other is not. Evaluation of the parts by Quasar is typically required to verify the suitability of a particular gray iron for our testing method.
10. How is Quasar different from a resonant hammer (impulse) testing method?
Impulse testing is a method in which the part is struck with a hammer and a microphone is used to detect the vibration. A Fast Fourier Transform is applied to the audio signal to compute the resonant spectrum. The advantage of the impulse method is that it is fast and inexpensive. The disadvantage is that it is limited to detecting only the largest defects. The primary reason for this limitation is that normal process variations that are present in every manufacturing operation have a greater effect on the resonant frequencies than the effect of the defects. The result is that normal process variations mask the defects. While an impulse system often seems to provide satisfactory results if a single production lot of parts is tested, when many lots are tested, lots that represent a normal range of process variation, it is generally proven unsatisfactory. Quasar's Process Compensated Resonant Testing (PCRT) method compensates for process variation by precisely measuring several resonances and computing a resonant pattern that accepts good parts and rejects defective parts. See Quasar Technology for more detail on PCRT.