Investigation of lubrication strategies in Ti6Al4V milling operations
Date
2008-12
Authors
Joubert, H. J.
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
There is a growing global demand for titanium. The aircraft industry is the driving force
behind the demand for titanium. The reason for this is that titanium has attractive
properties that justify its use both economically and environmentally. Titanium alloys
have superior strength-to-weight ratios. This implies that by substituting components
manufactured from other metals in the aircraft with titanium components, a substantial
reduction in structural weight can be achieved. From an economical point of view a
lower mass implies lower fuel consumption. From an environmental point of view lower
fuel consumption implies less harmful greenhouse emissions.
Ti6Al4V components are the most widely used titanium alloy products in aircraft
components. Ti6Al4V is known as a difficult-to-machine material. This is due to its low
thermal conductivity and small contact area between the tool and the chips causing
higher temperatures to be generated closer to the cutting edge of the insert. This will
subsequently increase the rate at which the cutting tool wears. For this reason relatively
low cutting speeds and feed rates are employed for the machining of Ti6Al4V compared
to the machining of steels. Ti6Al4V is an exceptionally high cost material. The low
cutting speeds and feed rates used in Ti6Al4V machining raises the machining cost of
parts and contributes to an increase in the price of Ti6Al4V parts. By employing higher
cutting speeds and feed rates machining times on Ti6Al4V products could be decreased,
subsequently lowering the price for Ti6Al4V components.
An increase in cutting speeds and feed rates will subsequently cause an increase in
generated cutting temperatures, resulting in an increase in tool wear. This stresses the
importance of controlling the cutting temperature during machining of Ti6Al4V in order to
prolong tool life. The focus of this work was to investigate different lubrication strategies
for polycrystalline diamond (PCD) and tungsten carbide inserts for Ti6Al4V milling
operations in the quest to develop improved feasible cutting parameters.
The results of this study showed that flood lubrication should be utilized for PCD inserts,
while a “softer” 60 bar high pressure through spindle lubrication worked best for the
tungsten carbide inserts. By utilizing these lubrication strategies, cutting speeds of 100 m/min and feeds per tooth of 0.05 mm/rev for both the PCD and tungsten carbide grades
could be attained with satisfactory tool life.
Description
Thesis (MScEng (Industrial Engineering))--Stellenbosch University, 2008.
Keywords
Ti6Al4V components, Dissertations -- Industrial engineering, Theses -- Industrial engineering