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Technical Paper

Fail Safe Drilling of CFRP/Titanium and /Aluminium Stack with H8 Quality for Aerospace Applications

2013-09-17
2013-01-2223
Ever since the advent of fiber reinforced polymer materials in the field of Aerospace, Metal-FRP stacks started to gain importance due to their superior fatigue performance, phenomenal low weight and good specific strength. However the machining, specially drilling these multi stack materials has always proved to be a challenge for the field of manufacturing and assembly. Drilling holes in only metal with a drill (metal drill), the material removal is through a process of clear shearing since the tool is much harder and sharper than the base material. The tools hence wears at a much slower and gradual rate, also the malleable properties of the machined metal compensate to the reduced cutting capability of the worn out drill. These properties of the machined metal act like a ‘FAIL SAFE’ mechanism during the machining process assuring a trouble free fail safe environment during the drilling process. However, drilling FRP composites is altogether a different story.
Technical Paper

Impact of the Fourth Industrial Revolution to Complex Aerospace “CFRP/Ti Drilling Applications” in Conjunction with Advanced Cutting Tool Design and Electric ADU’s

2016-09-27
2016-01-2099
On CNC Machines, drilling holes under perfect condition is possible. For drilling holes into titanium, composite and aluminum stacked materials the specific cutting condition can be selected. Furthermore surrounding conditions such as peck cycle, MQL and force and torque monitoring can be easily adapted. When drilling holes in the final assembly, CNC machine tools cannot be employed due to sizes and accessibility. Power Feed Units or Automated Drill Units ADUs are very handy, flexible and depending upon the jig extremely rigid. Whenever a machine tool does not fit, ADUs are highly recommended. In comparison to machine tools, conventional pneumatic ADUs can be used with one fixed set of feed, speed and micro peck only. Due to that a compromise in cutting condition has to be chosen in drilling stacked material with different layers.
Journal Article

Axial and Orbital Drilling of Thick Stacks for New Aircraft Assembly Process

2013-09-17
2013-01-2226
This technical paper deals with design and manufacture of axial and orbital cutters for drilling large diameters holes in Carbon Fiber Reinforced Plastics (CFRP) / Titanium (TA6V) thick stack by means of an Automated Drilling Unit fixed on a drilling template. Creating tools that drill such stacked holes in a single operation is particularly difficult. The common strategies for tool designs designated to cutting composites stacked with metals as titanium include uncoated carbide, tools with a diamond coating applied by chemical vapor deposition (CVD). It is also question of what kind of drilling process should we use to achieve larger holes in minimum time. Therefore, axial drilling process with pilot, drill and ream steps find a competitor drilling process named orbital drilling which can achieve both operations in one step allowing then, burrless, free delamination, small and easy removable chips all with one tool being able to achieve different hole sizes.
Journal Article

Process Understanding of Dry Drilling CFRP/Aluminium and AL/AL Stacks in IT8 Quality

2016-09-27
2016-01-2116
Drilling holes into metal with MQL (Minimal Quantity Lubrication) is a normal procedure, because the drill is designed for drilling metal and the malleable capability of the metal compensates for the insufficient cutting capability of a worn out drill. Drilling composite materials using the same drill (designed for drilling metal) is a different procedure, because composite fibers are not malleable like metal at all. Due to this fact the tools become very hot trying to forge composite fibers like metal. The elastic behavior of the composite and the delamination inside the hole makes the tool temporary smaller than the diameter of the drill. The hole in the metal part of the stack remains slightly larger due to the heat and the thermal expansion rate. This paper shows how to drill metal and composite with the same diameter, so that achieving H8 quality is no longer a dream.
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