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Die Casting Parts Review

Pinless tag clip- zinc die casting parts

  • Zinc: ZA-8
  • Weight: 0.35 oz
  • Miniature  zinc
  • 100,000 parts in 4 weeks

Power conditioning module chases – aluminum die casting parts

  • Aluminum: 380
  • Weight: 2..3lbs
  • ̴12”ꭗ12” (30ꭗ30 cm)
  • Die built in 8 weeks
  • Replace machined component
  • Significant cost savings

Steering knuckles

Performance

  • Passed 1.4g cornering load at 130,000 min and 280,000 cycle’s max (4 to 8ꭗ req.)
  • UTS > 2ꭗ customer requirements in all tests
  • Lower control arm test: unbreakable (fixture failure)
  • Outperformed all previous AI knuckles
  • 10% weight reduction
  • 5% cost reduction

Thrust rods

Performance

  • ̴50% weight reduction
  • Ribs allowed stiffness needed
  • Three parts consolidated into one
  • Replaced stamped steel parts

Engine base bracket

Performance

  • 43.6% weight reduction over stamped steel fabrication
  • Met strength and ductility requirements
  • 16 parts to 1
  • 4 different brackets now one common bracket
  • Cost reduction confidential per customer
  • Up to 1M per year

Engine subframe

Performance

  • Welded to hydro/bulge formed and squeeze cast parts
  • 46% weld length reduction  ̴40% lighter
  • Down to 16 parts from 48 (66% less)
  • Cost reduction realized, but confidential

Shock tower

Performance

  • 40% weight savings
  • Eliminated 5 part steel assembly
  • Exceeded requirements
  • Elongation allowed self-piercing riveting
  • Allowed thin wall heat treatment

Porosity – background

  • Common in many die castings
  • Common in metal casting
  • All defects are characteristics of the process
  • Considered a defect when porosity level exceed requirements

Outline

  • Sources of casting defects
  • Process control of defects
  • Design control of defects
  • Measuring defects

The cause of defects

Background

  • Two sources of porosity
  • Solidification
  • Gas (various sources)
  • Smooth pores formed at high liquid fractions
  • Jagged pores formed at a lower liquid fraction
  • Many aluminum alloys shrink  ̴6%
  • Common casting pore fraction < 3%

Shrinkage porosity – summary

  • Shrinkage can account for all the porosity
  • To reduce shrinkage porosity
  • Feeding, feeding, feeding
  • Bigger gates
  • High pressure
  • Etc
  • Alloy design
  • Interacts with gas porosity

Dissolved gas porosity

Three major causes of gas

  • Hydrogen gas
  • Entrained air
  • Evaporation of lubes, water, etc…

cannot be separated from shrinkage easily

gas will fill shrinkage pores

Hydrogen porosity

hydrogen solubility

  • high in liquid
  • low in solid

during solidification

  • hydrogen gas rejection
  • forms porosity

typically

  • microspores
  • combine with larger pores

Entrained air porosity

air caught during filling

  • in short sleeve
  • during injection
  • poor venting

difficult to predict quantitatively

process variables and design affects air entrainment

The vacuum can be effective

Other gas porosity

typical other sources of porosity include:

  • die lube
  • plunger tip lube
  • water
  • hydraulic oil/heating oil leaks

color of porosity can help identify sources

  • dark = lubes
  • light/shiny = water

Reduce leaking

  • impregnation
  • reduce porosity
  • avoid removing skin
  • avoid soldering
  • move knit lines

practically

  • process control
  • gating
  • design

Design for Die casting manufacturing

Design guideline

  • Similar to injection moulding. Consider die casting when the inserted part does not have sufficient strength.
  • Wall thickness function of alloy (typ 1.0 – 3mm). can go up to 10mm (will be permeable –a power not proportional to the wall)
  • Ribs 80% wall thickness shrinkage less of an issue.
  • Cooling time proportional to wall thickness (injection is t^2), so can have faster cycle times and thicker walls.
  • Draft depends on alloy. Assume > 1.0 deg, esp. on cavity side.
  • Tolerance is a function of alloy, part geometry and dies construction.
  • Zinc alloy linear: + / − 0.025mm across up to 50mm.
  • Zinc alloy hole: + / − 0.015mm up to 25mm diameter.
  • need over flow wells and secondary ops − > $$
  • No internal slides or snap fits.

The die casting option: broad range

  • Agriculture machinery
  • Auto motive vehicle
  • Building hardware
  • Electrical and electronic equipment
  • Hand tools
  • Home appliances
  • Industrial product
  • Instrumentation
  • Lawn and garden equipment
  • Office furniture
  • Recreational equipment
  • Portable power tools

Cold chamber

  1. Advantages
  2. Large complex parts
  3. Higher pressure
  4. Many production layouts possible

Hot chamber Die casting

  1. Advantages
  2. Metal temperature control.
  3. Automatic refill
  4. No cooling
  5. Less oxidation

Types of dies

  • Single cavity die
  • Multiple cavity die
  • Family die
  • Unit die

Injection sizing

  • Critical variables
  • Hydraulic pressure
  • Cylinder size
  • Dry shot speed
  • Gate area
  • Part volume
  • Fill rate

Clamping tonnage

  • Projected area of shot X metal pressure
  • Metal pressure   ͏͏͏͏̴ 10,000 psi (70 MPa)
  • Example
  • 100 ꭗ 10000/2000=500t (450mt) of clamping force required

Other process design concerns

  • Filling pattern and plunger speed profile
  • Venting and vacuum
  • Thermal control
  • Dimensional control

Thixocasting (semi – solid)

  • Most casting processes use a fully liquid feed material
  • Semi – solid casting uses as feed material that is 50% liquid and 50% solid

Semi – solid metal casting

    Advantages

  • Viscous  flow (less air trapped)
  • Shorter cycle time (colder material)
  • Increased tool life (less shock)
  • Reduced shrinkage (narrower cooling range)
  • Reduced porosity (directional solidification)
  • Improved mechanical properties

Example part

  • Turbocharger impeller

Squeeze casting

  • Fully liquid feel metal
  • Inject slowly
  • Avoid turbulence associated with conventional de casting

Processes

  • Horizontal (HSC)
  • Horizontal vertical (HVSC)
  • Vertical (VSC)

Squeeze casting

  • Process specific advantages
  • Non – turbulent flow
  • Reduced porosity (directional solidification)
  • Improved mechanical properties
  • Process specific disadvantages
  • Casting wall thickness Min 4 to 5mm (0.150 to 0.200”)
  • Large gates 6mm to 38mm (0.25 to 1.5”)
  • Large runners
  • Directional solidification (gate location)
  • Limited cavity number (orientation in die, pressure opening die)

High integrity die casting processes

Vacuum Die casting

  • Fully liquid feed
  • Fast fill
  • Vacuum level in the die cavity of 100 millibar or less
  • Eliminates cavity gasses from the shot sleeve and die
  • Used for crash resistant automotive castings

When to Use Die Casting

Metal Casters have the luxury of choosing between several casting methods to accomplish their goals. Often times the metal caster chooses one method and sticks with it for several years until need directs him to another. Of course, there are those adventurous few who like to sample each casting method to find the best fit. Sure, sand casting might be the most popular but what about Lost Foam or Investment?

What about Die casting?


Die casting is used by industrial foundries and manufacturers to create practically anything and everything, such as die cast cars. Many small foundries, like the one in your garage, backyard, of workshop may find that die casting is really just not economical. But who said that having fun and trying new things was ever economical? This process we aslo called high pressure die casting or pressure die casting, The process of Die Casting involves a simple concept. The molten metal is injected with high pressure into the mold or mold cavities. The mold used in die casting can have several small civilities of either the same pattern or different pattern.


The name Die Casting comes from the molds which are called dies. These molds are reusable and are often made from steel but other alloys can be used as long as they can withstand high pressure. The reason dies must be created from metal and not from sand or other material is due to the high amount of pressure used to get the molten metal into the mold. If sand molds were used in a Die casting procedure then the mold would crumble. There are plenty of advantages of using dies in a casting procedure which makes this method desirable for anyone wishing to create a high volume of similar castings.

Die casting is perfect for anyone that needs to make a lot of the same thing without any quality or pattern deviation. This is especially helpful in certain industries where quantity and quality count. Many hobbyists may have no use for die casting on a practical basis but will often try at least one Die casting for the sake of trying.

There are two types of machines used in the Die Cast procedure. These machines are essentially the same and are called the Hot-chamber and the Cold-chamber.

The Hot-chamber machine melts the alloy and feeds it into a section of the machine referred to as the gooseneck. A piston then forces the alloy into the mold. A separate furnace is not needed but the draw back of this is that metals with higher melting points can not be used.



The Cold-chamber is used for metals that can not be used by the Hot-chamber such as aluminum and copper. A separate furnace is needed to melt the alloy which is then poured into the injection cylinder and then shot into the mold.

The advantages of using Die casting vary but the most noticeable advantages are the repeated quality, smooth casting surface, and the quick production of casts. While the initial cost of Die Casting exceeds several of the other casting procedures, those that need a high number of casts in the shortest amount of time possibly will benefit greatly from the investment.

Die casting is commonly used to create commercial goods as it yields a high volume. The molds, or dies, used vary in life cycle depending upon the material used to create the die. The die can have one cavity or several cavities depending upon the need.

Everyone should try Aluminum die casting, magneium die casting or zinc die casting at least once if they can afford the initial cost. Besides, who knows when you’ll need a small battalion of metal soldiers which can be made quickly and easily with die casting.