Entry into automated power monitoring
The PowerMeasuringModule (PMM) is a robust laser power measurement system that determines optical power directly in the production zone. Thanks to the fieldbus interface, the PMM can be easily integrated into equipment controllers – various systems are available. Fully automated measurements can be carried out and documented due to the direct coupling to the machinery controller. This creates the basis for beam monitoring during processing – an essential component of quality assurance in manufacturing with lasers.
In the field
The PowerMeasuringModule is suited to users who have specialised in manufacturing with lasers. The system is used frequently in automotive manufacturing. Car bodies are frequently welded with robot-controlled solid-state lasers (Nd:YAG-, fibre, disk or diode lasers).
Laser power is monitored in the production breaks where necessary. The robot moves to a measuring position with the PMM for this purpose. The measurement is taken on the defocused beam.
The PowerMeasuringModule is suited to many other applications in automated manufacturing with solid-state lasers – not just in macro-processing, but also micro-processing. The PMM's field of application can optionally be extended to low average powers as well as pulsed beam sources.
Measurement methods – the principle
The PowerMeasuringModule measures the laser power calorimetrically. The absorber is irradiated by the laser for a defined period. With the heat capacity of the test body, the temperature increase and the exposure time, the optical power is calculated in a few seconds. The exposure time measurement increases the reliability of the results.
The measurement result is independent of the beam dimension and the beam position. The absorber cools via thermal conduction to the surrounding air. This restricts the measurement frequency of the system. The plant controller can query the absorber temperature at any time and determine the new irradiation period.
A mechanical closing device at the inlet opening and protective glass protect the measuring device from dirt.
The maximum power density on the absorber is 4 kW/cm² (at beam diameters >10 mm).
Fast measurement sequence
When the PowerMeasuringModule is integrated into a industrial robot manufacturing set-up, the aim is to achieve the shortest possible clock cycle when measuring. In order to reduce the measuring duration, the standstill time of the robot can be reduced to just the irradiation period of the PowerMeasuringModule.
The measurement results are displayed by the user autonomously at the system controller level. Data transfer is adapted to the fieldbus system used.
Measured beam parameters
Average laser power of solid-state lasers at:
- Wavelength: 450 - 550 nm, 900–1090 nm
- Maximum laser power: 12 kW
- Irradiation time: 0.1 – 2.0 s (depending on laser power)
0.1 – 1.0 s (type AP3s)
- Total duration until measurement value output:
< 5 s (AP3s); for devices with former thermalization standard: < 15 s
The PowerMeasuringModule is operated solely via the system controller. The sequence of a power measurement can be divided into three stages:
- Making ready to measure
- Carrying out measurement
- Evaluating measurement
AP3s – a new standard in power measurement
The PMM has received an upgrade and is now available as the PMM AP3s series.
The designation AP3s stands for the following improvements:
- A: Advanced absorber for power densities up to 12 kW/cm².
- P: Pulsed radiation measurement with a repetition rate up to 10 kHz at 50 % duty cycle and a minimum pulse length of 50 µs.
- 3s: Ultra fast results in only 3 seconds instead of former 15 s.
In a nutshell: More detailed power measurements at higher power densities in a shorter period of time.
Models and accessories
As a standard feature, the PowerMeasuringModule is supplied with exposure time measurement and also a protective glass cassette, which can be replaced quickly without tools. The following models are available:
- NEW: PowerMeasuringModule PMM AP3sM for power measurements in confined spaces, close to the focus. Equipped with an additional microlens array, it can handle up to 200 kW/cm² whenever space is limited and damage thresholds are difficult to be kept.
Available with any field bus interface.
- PowerMeasuringModule with PROFINET®
- PowerMeasuringModule with PROFINET® fibre optics
- PowerMeasuringModule with PROFIBUS®
- PowerMeasuringModule with EtherNet/IPTM
- PowerMeasuringModule with EtherCAT®
- PowerMeasuringModule with DeviceNetTM
- PowerMeasuringModule for use with low average power (of 50 W) and pulsed beams
The following parts are available as accessories or replacement parts for the PowerMeasuringModule:
- Protective glass cassette including protective glass
- Protective glass, set of 10
- Protective glass single