Investment Casting

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Investment Casting
A Titanium Golf Club Head
TMM 4180 Erica Purvis Kelly Houlker Justin Payne
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Contents

• 1. Function and requirements of a golf club head
• 2. Titanium and investment casting in golf
• 3. Fabrication methods
• 4. Materials

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Function Requirements of a golf club head

• Technical game dependent on skill, precision and
  equipment choice
• In a set of clubs there are 3 types woods
  (drivers), irons and putters
• Driver has 3 main parts grip shaft and head
• Driver purpose - ball into play, long straight
  distances

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Mechanical Physical Requirements

• Long shaft to increase power transferred to ball
• Sweet spot - ideal place to hit the ball on the
  head
• Hits the ball around 14 times a round - must be
  sturdy, durable able to cope with pressure of
  impact

Influential Performance Characteristics Size,
Thickness of face, Loft, Face height, Face angle,
Club length, Shaft type material, Driver material
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Thermal Chemical Exposure

• In normal use no exposure to chemicals or extreme
  conditions
• Corrosion resistant from rain
• Used in hot and cold conditions
• Deserts - highlands of Scotland (home of golf)

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Titanium Investment Casting in golf Requirements

• New Development in golf highest quality clubs
• High strength, low density
• Designers can increase size of a head without
  compromising weight
• Close geometrical tolerances is crucial
• Thin walled 1.016mm,
• Angle of lie and loft are with
  in 1 of specified
• Weight 2/-1g of specified
  weight

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Fabrication methods Investment Casting

• Also known as the Lost Wax Process
• Ancient casting technique used by Egyptians
  5000BC
• Modern industry due to aerospace, military
  defence, World War 2

• Improved technology
• High quality, tight dimensional control, thin
  items
• Metal hard to machine and fabricate

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Detailed method of investment casting (lost wax)
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1. Making of wax patterns.

• Normally
• Injection moulding

• Smaller volumes
• Rapid prototyping or
• Hand shaping

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Injection moulding

• The pattern is engineered extremely precisely
  using a precision die.

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Rapid prototyping or Hand shaping

• Topp class club heads

• hand shaped from cast epoxy resin
• CAD and Rapid Prototyping were previously used,
  but in every case the pattern required final hand
  shaping.

Pattern forming
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2. Assembly of wax sticks.

• Examined for defects
• Attached to a central wax stick by manual wax
  welding
• The tree houses the gating and feeding system.
• The tree, it is cleaned in a wetting agent or
  solvent solution, in order to remove any loose
  pieces or dirt.
• Clean water rinse

Wax Trees, Pre-Coating
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3. Ceramic shell building

• The tree is coated with a ceramic slurry mix.
• The first dip coat contains fine refractory
• Later coats contain coarser, dry particles
• Up to eight layers may be applied
• Hardened by chemical means or by drying in air

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4. Dewax (removing the pattern)

• The wax is melted out
• The ceramic shells are heated from the outside so
  that the surface layer of wax melts before the
  bulk of it expands under the heat.
• Lost wax

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4. Dewax (removing the pattern)

• flash and autoclave
• In flash, the shell is put into a furnace in the
  inverted position so that the wax will drain out

• In the autoclave method, superheated steam is
  used, at a pressure of around 6 bars, to provide
  rapid melting. The cycle is usually complete in
  15 minutes and the wax can then be recycled.

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5. Conventional casting

• The shells are heated to 1000C.
• Filled by molten metal
• left to cool for at least 24 hours

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6. Knockout

• The ceramic shell moulds are broken off by a
  variety of methods
• Vibration
• sledge hammer
• chopping saws
• shot blasting
• high pressure water blasting.
• Due to the mixture of different materials and
  gradings used in the refractory, the shell waste
  can not be reused

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7. Cut off of parts

• The parts are cut away from the central sprue
  using a high speed saw. 

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8. Finishing

• Investment castings often dont require any
  further machining due to the close tolerances
  that can be achieved.

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9. Final Product
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Alternative Fabrication Methods Forging

• The only other way used to make golf club heads
  is forging
• Until the 1970s, all golf club heads were forged
  because investment casting processes were not
  accurate enough until then.
• In general, forging is chosen over casting in
  circumstances where the final component has to
  withstand large stresses.

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Rough forging

• 1200? Celsius.
• massive forces

Raw forging

• 800? Celsius
• 250kg press

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Machining

• Metal working lathes are now used to machine the
  hosels to a specific outer diameter to match with
  the shaft to be used. Drill presses are used to
  bore holes of exact depth and diameter.

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Finishing

• Engraved with company details
• polished and buffed
• Nickel or Chrome is then applied to the heads via
  electroplating
• sandblasted to mark the score line
• painted as the final step
• each club head is forged at least 4 times, ground
  14 times and inspected nearly 20 times

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Welding

• Whether the head is cast or forged, the parts are
  joined by welding
• Titanium is one of the most difficult metals to
  weld because it is extremely reactive to oxygen.
• This means that the manufacturers must perform
  the welding in an inert atmosphere.

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Titanium

• Extremely reactive
• High strength weight ratio
• Good structural material, corrosion resistant,
  protected from the atmosphere by a thin surface
  oxide film.
• Difficult to fabricate as becomes brittle when
  exposed to certain gases
• - Vacuum furnace required! (Induction Scull
  Melting)

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Titanium alloys

• Four different groups
• Commercially Pure (CP) titanium Graded ASTM 1
  4, 7
• Alpha alloys Usually titanium and tin.
  Unresponsive to heat treatments. Weldable.
• Alpha-beta alloys Can undergo manufacture when
  ductle as usually heat treated. E.g. 6-4 titanium
• Beta alloys Highest density, good hardening
  cold forming capabilities. High strength
  properties if aged. E.g. 10-2-3 titanium

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Alternative Materials
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For golf club heads?

• Aluminium alloys lowest specific strength and
  hardness therefore used only in beginner clubs.
• Stainless steel although has a high strength,
  high density means that the size of the club head
  is restricted.
• Titanium alloys
• - Volume of head ? 500cc compared to 300cc
  with steel
• - High ratio of strength to elastic modulus
  gives improved spring performance and thinner
  club head face.
• - Harder than either stainless steel or
  aluminium, so less chance of deformation on
  impact.

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• Thank you for your time!

Questions?