Laser Process Monitor: the LPM

THE SYSTEM

The LPM is a device that overlooks at the behaviour of laser processes by monitoring the constancy of applied power or energy levels; as soon as the pre-set limits of those parameters have been overtaken, alarms signals will be delivered. Since a drop of set laser parameters simply means that something is changing within the system (often not immediately perceived), the LPM is then an extremely useful tool for laser machine operators. Typical applications are based on monitoring below the focussing head because, together with no affection on productivity and stops in manufacturing, it adds the following advantages:

• to know the true power or energy delivered to the workpiece, independently from overall absorptions, optics losses, dirt, etc.
• exploit the synergic effect generated by cross-checking information coming from the process area and the laser controller.

This valuable information brings the LPM to be used in a variety of applications:

• to provide immediate warnings for predictive maintenance and eliminate downturns on the laser machine,
• to improve laser machine and process reliability,
• to speed-up alignments of beam delivery components,
• to control the system stability over time
• to control the constancy of process parameters during different working cycles.

Measurements can be made continuously, on scheduled plans, during working downtimes or change of parts. The adoption of LPMs to monitor laser processes consequently provides a substantial increase of efficiency in the system and reduction of costs.

SIMPLE AND POWERFUL

The LPM bears the function of fixing an operative range acceptable to maintain functionality and quality on the process and then get alarm signals, that avoid major damages and time losses, if that acceptable band has been overtaken. These limits can be either set directly on the electronics or via the LPM’s software (LPM-SOFT). There are various ports for external communication, all included as standard features: Analog Outputs (Opto-Isolated 0-10V or 4-20mA , Digital Output (Opto-Isolated RS232 (RS 485 Mod-BUS Protocol-optional)) and a Process GO/NO GO Relay (220V, 10A). The main page of LPM-SOFT, of very practical use when tracking laser stability or during beam path alignments, displays both the safe working band and shows a warning red led. The LPM can work with all types of detectors including LaserPoint’s FIT-H power probes (they provide complete information in 6 seconds and read up to 6KW without water cooling). An LPM set-up is made by the electronics, a detector and the application software. Detectors associated to the LPM can be installed at any convenient location on the working plane or along the laser beam path, e.g. after a beam sampling optics.

LPM ELECTRONICS.

The electronic board can be easily plugged inside any laser or machine cabinet on standard MR9 DIN rails and allows operation on 2 different modes, user’s selectable:

Remote operation

The LPM dialogues and gets commands from the machine control unit through its serial interface RS232 (RS485 on request). A full featured application SW (LPM-Soft) reads values, allows to set alarms for process monitoring or system malfunctioning, to carry out statistical evaluations on running measurements, to save and download data.

Local operation

It is the most simple way to use the LPM which will only generate alarms, for example by switching-on an alarm lamp. The LPM monitors the laser power/energy and checks whether their values remain within two acceptable (Min/Max) threshold limits, preset on the electronics itself. Those two values are stored within the LPM memory by a self learning algorithm after a simple exposure of the detector to the laser beam, running at the Min and Max levels . If power/energy are out of limits, the alarm is generated, e.g. by means of a relay connected to the laser PLC. Additional alarm LEDs, located on the board itself will turn their colours. Two additional analog outputs ( 0-10V and 4-20mA ) can be used to know the absolute value of power or energy or tracking laser stability by means of multimeters or plotters.

DETECTORS FOR THE LPM

The LPM can work with all kind of detector heads manufactured by LaserPoint: this adds flexibility and expands the range of applications to the system.

Power Meter Mode:

This mode allows a continuous measurement of laser power. It helps during machine settings, can be used to monitor long term laser stability, optics alignment, etc. Operating range is from very low powers up to 6KW, CW.

Laser Probe Mode:

the OEM laser probes (Fit-H Series) allow power monitoring done on short laser exposures. This mode of operation is carried out by special detector heads and a patented method that allows automatic measures made in just 4-6 seconds, depending on the head model. The range of operation is from 50W f.s. to 6KW f.s. Together with lower costs for the detectors, another major advantage is that there is no need for water cooling even at multi-kW powers. Measurements with Fit-H heads can be programmed between working cycles for a quick check of the constancy of laser power, to verify new set parameters (e.g. to verify that power is really what is needed by the workpiece ), after components have been changed or realigned, etc. In practice, whenever long running measurements are not necessary.

Energy Meter Mode:

This mode is used to measure single shot pulses. Typical application is the monitoring of marking or micro welding machines. Available ranges go up to 600J (long pulses).

LPM-SOFT: APPLICATION SOFTWARE

The LPM-Soft is a powerful application software provided as standard with each LPM . The LPM can plot evolution graphs of time behaviour of laser power, display energy or FIT-H readings in the form of histograms, show the absolute values of power and energy, provide all relevant statistical information and allow the storage of data to files, as a text format usable for Excel or other programs. The LPM also allows the management of laser processes and laser tuning.

Display Functions

• Head Model: shows the head model in use
• Lambda: shows detector’s calibration wavelength
• SN: shows the head serial number
• Actual Time: shows present day and time
• POWER (W/mW); ENERGY(mJ/J): shows measured power or energy values.
• User Calibration Factor: this number will multiply the actual measured value by a selectable factor to reach a desired value.
• Head Temperature (°C): shows the temperature on heads provided with temp. sensor
• ZERO: accomplishes an automatic Zeroing
• TUNING: Enables the Tuning Function
• SAVE: Enables the automatic function to save measurements on a file
• PRINT: prints the displayed window
• QUIT: leaves the program
• Power Measurement Scales
• Graph Power Max/Min (W) sets the extention of Y axis on power plot.
• Graph Time: sets the duration of Time axis (X) for the power plot; available time scales are 60(sec), 2(min), 5(min), 30(min), 1(hour), 12(hours).

Laser Process Management

An important feature offered by the LPM Software is the possibility to monitor the ongoing laser process and get an alarm feedback in case the acceptable range for power/energy levels have exceeded the pre-set limits. This feature extends the LPM applicability to rigorous control and monitoring of industrial applications.

• Setting Process Parameters
• MAX/Min Power Levels: set process limits that remain visible on the screen as red lines, defining the acceptable working range.
• Alarms: the rectangular Led, when green, shows that measured value is within the acceptable range . When red, it shows that measurement is no longer within the acceptable preset working range and that an intervention by the operator may be necessary

Statistical Functions

A full set of Statistical functions is provided by the LPM-Soft. The Duration of acquisition interval can be selected to be as long as 24 hours. Once data have been gathered, SAVE enables an automatic saving on file for data recording or future data tracking . Statistical Functions include:

• Max/Min (W,J): the max/min power/energy values measured during the last acquisition interval
• Avg (W,J): the average values of power/energy measured during the last acquisition interval
• PTP (%): the Peak-to-Peak stability
• STD (W): the Standard Deviation on measured data
• RMS (%): the RMS stability

Tuning

A fast and highly visible Tuning Bar is available for tweaking or alignments. It displays variations of measured power on a double colour bar (green and red). The Power Variation (%) box shows how much power was gained or lost from an initial reference level. To remind the operator what has been the highest reached value, the Power Max(W) box stores that value . Evolution of laser tuning can also be comfortably followed on the screen.

Warning Message

All times measurement heads undergo to power levels above their full scale, an OVERFLOW alarm is displayed. The same way, whenever the temperature of a detector head is above its safety working limit, a COOL alarm message is displayed.

Download LPM Laser Process Monitor Specifications here

Not sure of your selection? EXPLORER will allow you to quickly find which instrument best suits your application. Start Here