THE LASER USER
ISSUE 114 AUTUMN 2024 BEAM DELIVERY
mirrors and spinning wedge beam manipulation techniques have been discussed and both have been deployed in real situations for laser machining or cleaning. The heads can readily be interfaced with robotic actuator systems as well as manual manipulators.
Figure 3: MEMS head under test in laboratory machining compressor blade at 20 W average power.
Further work is currently looking at higher power delivery and other beam manipulation techniques, and OpTek continues to develop novel solutions to address even more challenging applications
Figure 5: Head tested inside Rolls-Royce engine. Bright dot indicates region being machined. Image courtesy of Rolls-Royce plc.
Spinning optics
Figure 4: Head assembled on to endoflex arm. Head diameter 8 mm.
control wires are all contained within the 8 mm diameter section. The main arm and conduit also includes laser interlock wires to shut down the laser in case the fibre is broken. A protective window is mounted on the outer body to keep contaminants away from the internal optics and MEMS structure.
The system shown in Figures 3 and 4 has been successfully demonstrated on engine repair procedures at Rolls-Royce. Here the head was manually manipulated round a series of in-engine obstacles to its final location at the processing point. Whilst not a fully proven-out and deployed technology, this test demonstrates that the technology is capable of meeting the customer requirements.
The capabilities of the restricted-access machining head were extended within the Innovate UK COBRA (Continuum Robot for Remote Applications) project [2]. In collaboration with Rolls-Royce, the University of Nottingham and UKAEA RACE (Remote Applications in Challenging Environments), OpTek designed an end effector to attach to a continuum robot system. In this case, adding 1mm to the head diameter allowed 3 cameras and 3 LED illuminators to be included, all contained within an overall diameter of 9mm! In addition, the snake component contained a shape sensing fibre which allowed tracking the progress of the head through a convoluted route inside an engine or other installation.
This unit was successfully demonstrated on an engine repair similar to that shown in Figure 5 and the robot remotely controlled from a different geographic location.
The MEMS mirror system has been demonstrated up to 50 W of average laser power and pulse energies of >1 mJ.
A second head developed at OpTek for Rolls- Royce avoids many of the trade-offs inherent in the MEMS approach, and is compatible with higher powers, including a purely transmissive configuration where required.
In this head we spin two (or more) optical wedges driven by micro motors. The small size of the motors excludes built-in encoders, therefore a fibre-optic based encoder system has been developed to monitor rotational position and velocity. This allows synchronisation of the wedges and feedback to the laser for on-the-fly power control.
The system can be configured for forward, sideways or backward firing depending on the application (Figure 6).
Figure 7: A 12 mm diameter spinning optics head mounted on a continuum robot arm inside a jet engine for a machining demonstration at the University of Nottingham. The machining point is apparent from the bright plasma light. Image courtesy of Rolls-Royce.
Figure 6: Spinning wedge head configurable for forward or side firing.
For higher power laser delivery, the head can be cooled using compressed air fed through the conduit and into small tubes in the body. This technique is also a way of delivering assist gas if required (Figures 7 & 8). This head can also be manipulated manually or mounted on a robot.
Summary
OpTek has developed miniaturised laser processing heads for machining in restricted access situations. MEMS-based scanning
Contact: Mike O'Key
mokey@opteksystems.com
www.opteksystems.com
Mike O'Key is Fiber Optic Development Manager at OpTek Systems where he has developed OpTek’s LaserCleave machines and novel laser processing techniques.
SEE BS EE OBSERVATIONS P26 29 25
Figure 8: A circular region of organic deposit removed from inside an aluminium component using the head of Figure 7.
[1]
https://www.nottingham.ac.uk/utc- manuonwingtech/
index.aspx
[2]
https://gtr.ukri.org/projects?ref=104066
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