What is the Best Orientation for a Combustor During Drilling?

Question:

Laser drilling is new to us and we are planning to add this capability in the near future. In thinking about the machine configuration, we have been having an internal debate about the best orientation for a combustor liner during drilling. What is your experience?

Answer:

First of all, let me say that this a very good and frequently asked question.

Photo 1: Mounting the rotary table with its face in the horizontal (X-Y) plane provides advantages in drilling and cutting combustor components.

Our experience, which is based on over three decades of supplying laser systems for drilling combustor components is that combustors should be drilled as shown in the picture to the right (Photo 1), which is with the face of the rotary table oriented in the horizontal plane (parallel to the X-Y plane). There are a number of advantages of this configuration over the other choice which is the rotary table mounted to the vertical plane. These include:

• Considerably easier programming for drilling compound angled cooling holes, especially with compact profile of the LASERDYNE BD3Y BeamDirector®. This will be covered in system operation and program training.
• In this orientation, it is also easier to create drilling programs for parts with restricted information such as 2D drawings without a solid model (CAD) which is often the case when prototyping and producing high security combustor parts for which there may be limited information for laser drilled hole locations.
• Simplifies and reduces the size and weight of fixtures since horizontal mounting does not require heavy rigid fixture clamps which often restrict access to the parts. Smaller clamps will minimize and help to avoid interference between the clamps and laser gas assist nozzle.
  • Simpler setup and alignment means easier training of machine operators with a lower possibility for setup people and operators to make mistakes, some which can be costly.
• Setup and alignment of the fixture on the rotary table is faster, easier, and more accurate – gravity works for you, not against you as when the fixture is mounted to a vertical rotary table surface.
• With the part on a horizontal rotary table, it is possible to drill holes at a greater number of angles and positions on both the inside and outside of the part. As indicated in Photos 2 and 3, access for drilling from the inside of a part is limited when the rotary table face is vertical.

Photos 2 and 3: With the rotary table mounted with its face in a vertical plane, the depth into the part which can be accessed by the laser beam is limited.

• With the part on a horizontal rotary table, the BeamDirector® can be oriented normal (perpendicular) to the interior part surface which gives the greatest precision in mapping the part. (Let me know if you would like to have a separate discussion about mapping.)
• Significantly larger part diameters can be processed with the rotary table mounted with its face in the horizontal position.
  • One reason is that the rotary table can be easily re-positioned on the work table to provide for drilling parts larger in diameter than would be suggested by the axes travels.
  • Another reason is that the load capacity of the rotary mounted with its face in the vertical position is on the order of 50% that for the same table when its face is in the horizontal position.
• The operator has much easier access to the part for setup or in-process inspection, (see photo 2 and 3) especially given the walk-around work table.

We hope this helps. The overwhelming number of circular parts, like a combustor, are processed as described above. If you would like assistance in programming or fixture design please feel free to contact us and we will make the necessary arrangements.