Laser Beam Drilling

Brochure Laser Drilling

Brochure Laser Drilling

By laser radiation holes can be drilled with diameters ranging from less than one micrometer to several millimeters while maintaining the same drilling depths. The Fraunhofer Institute for Laser Technology ILT is developing several drilling processes ranging from fundamental research to industrial systems implementation. Application areas for laser drilling include injection nozzles, ventilation holes, air-cooling holes, contact drilling and filter holes.

The Method

Depending on component thickness as well as required quality (precision) and productivity (drilling duration), holes of approximately 1 μm to several millimeters in diameter are drilled into the workpiece by means of single pulse drilling, percussion drilling, trepanning, and helical drilling. The following table shows the distinctions among the various drilling methods with respect to diameter, depth and duration.

Single-pulse drilling can be performed “on the fly,” so that up to 300 holes per second with a diameter of 60 μm can be drilled into metal sheets of 1 mm in thickness. Trepanning, which involves relative movement between the workpiece and the laser beam, is used for drill hole diameters larger than approximately 300 μm. Helical drilling is used to create holes that have both highly precise geometry and superior metallurgical quality. Laser drilling is an alternative to methods such as electron beam drilling, electrical discharge machining, electrochemical drilling and ultrasound drilling. The use of “light as a tool” is preferred when the manufacturing process requires drill holes with diameters of approximately 1 to 500 μm and high aspect ratios (> 1:20) to be made under difficult conditions, such as those involving large inclination angles to the workpiece surface, or materials of high hardness (e.g. nickel-based alloys). Challenges exist with respect to the minimization of melt layers and the avoidance of micro cracks in the drill hole wall.

Physical Basis of the Process

Laser drilling methods can be distinguished into meltingdominated and evaporation-dominated methods. At pulse durations ranging from microseconds to milliseconds, the material is largely melted by the laser, a small portion evaporates. The resulting steam pressure expells the melt out of the drill hole. This drilling process is highly productive; however, melt layers with thicknesses of up to 100 μm still adhere to the drill hole walls.

At pulse durations of less than 10 ps, the material evaporates completely, and there is almost no heat transfer into the workpiece. With proper movement of the laser, drill holes can be created without leaving melt layers on the drill hole wall. Through the use of related systems technology, high quality cylindrical and conical drill holes can be created that feature high aspect ratios.

Application Areas

Due to the high intensity of the laser pulses, nearly all materials such as metals, ceramics, semiconductors, CFRPs, plastics, as well as multilayer systems made using these materials can be drilled with great precision. Areas of application include the making of air-cooling holes in turbomachinery components such as blades or combustion chambers, drill holes for fuel filters or injection nozzles, and ventilation holes for injection molds in tool manufacturing.

Plant and Systems Engineering

Aside from its process technology work, Fraunhofer ILT also develops the systems necessary for the industrial implementation of these drilling methods. This includes the development of specialized helical drilling optics with high-speed local laser beam modulation, in addition to drilling process integration within automated production systems.

Plant and Systems Engineering

In addition to its work on processes, Fraunhofer ILT also develops special laser drilling systems to support the industrial implementation of the drilling processes. The institute’s activities in this domain range from the development of special drilling optics with high-speed spatial laser beam modulation to their integration in existing manufacturing plants. The services provided include customized machining solutions complete with process monitoring and control, and extend to qualification of the customerready process on the basis of short manufacturing runs.

Equipment

Fraunhofer ILT has a number of modern laser systems used for laser drilling. These include:

  • Long-pulse lasers (pulse durations μs - ms) such as
    • IPG fiber lasers with 6 kW peak output power
    • IPG single-mode fiber lasers with 1.5 kW peak output power
  • Short-pulse lasers (pulse durations ns - μs) such as
    • Edgewave double-pulse laser with 2 x 40 W mean output, pulse duration 2 - 10 ns, 50 kHz
  • Ultrafast lasers (pulse durations fs - ps) such as
    • Amphos 500 with 400 W mean output, pulse duration 0.7 - 8 ps, repetition rate up to 54 MHz
    • Trumpf TruMicro 5270 with 60 W mean output, pulse duration 7 ps, repetition rate 400 kHz

For optical beam formation, Fraunhofer ILT also offers drilling optics with focal lengths of 70 to 300 mm, helical drilling optics, and various scanning systems.