Reliable sensors for industrial quality control

Acoustic testing of actuators and drives despite environmental noise

Sounds like rattling, whining, clicking or chirping are acoustic indicators that can be clearly identified as the proprietary acoustic signature of manufactured parts, which can be deteced by acousitc testing without contact using laser Doppler vibrometers. Drive systems which contain damaged or warped components – such as cogs – often generate unwanted operating noises and need to be detected and rejected during production. A product defect, especially in highly stressed components, can lead to the complete failure of the system and the end consumer complaining. Laser vibrometry has proven to be the perfect measurement technique for this process, as it allows for non-contact, high-precision, automatic and reliable quality control using frequency and order analyses.

In automated noise test stations, you can use laser vibrometers from Polytec to affordably, reliably and efficiently check your products with very short cycle times. Unlike microphones, the laser vibrometer only measures structure-borne sound and is not influenced by environmental noise. This saves you from using noise protection cabins. So, for example, you can ensure that micro drives have not been supplied with defects or disturbing noise. So customer complaints about “rattling”, “whining”, “clicking” or “chirping” are a thing of the past. You can define the perfect spot for acoustic quality control in advance by analyzing the component in detail with a PSV Scanning Vibrometer.

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Example of acoustic testing:

When manufacturing motor pump units for electro-hydraulic steering gears, during the complete check it is standard practice to examine even several operating conditions from standby to full load. Carrying out an order analysis with laser vibrometers from Polytec allows detailed conclusions to be drawn as to the cause of the fault, such as the pump shaft’s true running accuracy being inadequate. By measuring the outside surface with a laser spot in a non-invasive way, the true acoustic signature of parts allow quick and effective pass-fail decisions.

Quickly and contactlessly testing white goods

In the consumer and capital goods industries, both product optimization and process optimization play a vital role when it comes to economic success.

Experience has shown that spot checks performed on systems selected at random do not result in a reliable outcome. Only carrying out a complete check on the finished products guarantees a high quality standard. You should therefore opt to perform vibration tests with laser vibrometers from Polytec. Vibration analysis is ideal for distinguishing good products from faulty ones, which is why it is advisable to use vibrometers for quality control purposes. Laser vibrometry has established itself as the method of choice for non-contact testing. With the help of the laser vibrometer, the system reliably detects potential defects such as faulty or loose components or machine imbalance and provides information on the specific cause of the fault

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A practical example:

Electrically driven household appliances or their components which generate unwanted vibrations and noise are reliably detected in production by laser vibrometers and removed from the process. Examples include washing machines, vacuum cleaners and electric toothbrushes.

Manufacturing medical devices with maximum precision

People’s health is always the top priority in medicine. Therefore it is particularly important to ensure a consistent level of quality and reliability in medical device production. High-precision measurement and rapid analysis are very much in demand here, since even minor deviations can sometimes lead to unforeseeable and serious consequences.

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A practical example:

Pari GmbH manufactures nebulizers to treat respiratory diseases that accurately meter the liquid drug. The liquid is pressed through the holes in a membrane, which is stimulated to produce ultrasonic vibrations by piezo elements, and atomized. Using laser vibrometry guarantees a consistent nebulizer quality and thus an excellent reproducible drug effect for the patient.

Polytec’s laser vibrometers have even analyzed the membrane’s vibration behaviour at the product development stage and thereby enabled consistent design and functionality optimization.

Complete quality control in production also uses the contactless measurement method to ensure zero-fault quality. A semi-automatic measuring station was developed together with Polytec for this very purpose. A CLV Compact Laser Vibrometer measures the membrane’s movement with zero contact. The QuickCheck test software from Polytec saves and analyses the measurement data during production and allows for a good / bad decision to be made directly. Thanks to QuickCheck’s flexible architecture, quality engineers were able to continuously improve the evaluation algorithm and thereby reduce pseudo rejections.

Zero-fault production in the engine cold test

A complete check is carried out during the final inspection in combustion engine production for vehicles. Each individual unit is extensively tested before leaving the factory. For example, it is checked for undesirable noise and vibration when subjected to so-called noise, vibration and harshness (NVH) tests.

An electric motor pulls/spins/powers/drives the combustion engine during the engine cold test. In addition to measuring the vibration and noise behaviour of the engine as a whole, the component or assembly faults are also identifiedusing the vibration signal measured contactlessly with one or more laser vibrometers, so that targeted, effective repair or rework can be carried out.

You can use Polytec’s laser vibrometers to identify the following fault patterns, for example: damage or production deviations on cam shafts, incorrectly set valve clearance, faults on ancillary units such as high-pressure pumps, gear tooth faults, bearing damage or foreign bodies in the combustion chamber.

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A practical example:

Saab Medav Technologies, based in Uttenreuth and Ilmenau, specializes in digital signal processing, marker systems, radio monitoring, vibration analysis, information processing and measuring technology for quality checks. The Bavarian company has been relying on the high quality, precision and reliability of Polytec’s vibration measurement systems for more than 20 years now. And with good reason too, as Olaf Strama explains:

“We have been using laser vibrometers for vibration measurement since the mid-1990s. We started with a Polytec CLV, and then we purchased a batch of IVS-200 industrial vibration sensors. In the meantime, we have used its successor, the IVS-400, especially for measurement points that are difficult to access or where a high measurement bandwidth is required for automatic production.

Dipl.-Ing. Olaf Strama, Director of Industrial & Automotive Solutions (IAS) at Saab Medav Technologies