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3-1 Chapter 3 Overview b Several variations to die casting b The variations depend on several factors: Temperature of the metal pump Temperature of the.

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Presentation on theme: "3-1 Chapter 3 Overview b Several variations to die casting b The variations depend on several factors: Temperature of the metal pump Temperature of the."— Presentation transcript:

1 3-1 Chapter 3 Overview b Several variations to die casting b The variations depend on several factors: Temperature of the metal pump Temperature of the metal pump Consistency of the metal when it is injected Consistency of the metal when it is injected Metal velocity Metal velocity Gating configuration Gating configuration Condition of die cavity at moment of injection Condition of die cavity at moment of injection

2 3-2 Chapter 3 Objectives b Identify the two major methods of injecting metal into the die b List advantages of hot chamber die casting b Explain why cold chamber die casting is used b Explain how vacuum die casting can reduce defects b List two emerging die casting technologies

3 3-3 New Terms b Billet A small metal bar A small metal bar b Static metal pressure The metal pressure in the die cavity at the instant that the cavity is full The metal pressure in the die cavity at the instant that the cavity is full b Thixotropy The property of a fluid mixture to become more fluid as the mixture is agitated The property of a fluid mixture to become more fluid as the mixture is agitated

4 3-4 Two Major Processes b Hot chamber and cold chamber die casting b Get name from temperature of metal pump relative to temperature of the metal In hot chamber, the metal pump is submerged in the metal and is same temperature as the metal In hot chamber, the metal pump is submerged in the metal and is same temperature as the metal In cold chamber, the metal pump is outside the furnace and is cold relative to the metal ladled into it In cold chamber, the metal pump is outside the furnace and is cold relative to the metal ladled into it

5 3-5 Hot Chamber Components b A Frame Suspends shot components above and in the furnace; mounted to stationary platen Suspends shot components above and in the furnace; mounted to stationary platen b Shot cylinder Actuates vertically; metal is injected with downward stroke of the shot cylinder Actuates vertically; metal is injected with downward stroke of the shot cylinder

6 3-6 b Coupling Connects shot cylinder to plunger rod and tip Connects shot cylinder to plunger rod and tip b Plunger rod and tip Pumps the metal; piston tip has 2 or 3 grooves in it for piston rings Pumps the metal; piston tip has 2 or 3 grooves in it for piston rings Hot Chamber Components

7 3-7 b Rings Prevents metal from bypassing tip; helps maintain metal pressure after die cavity is filled Prevents metal from bypassing tip; helps maintain metal pressure after die cavity is filled b Gooseneck Combination sleeve and metal path out of the metal pump Combination sleeve and metal path out of the metal pump Hot Chamber Components

8 3-8 Hot Chamber Components b Nozzle Tube connecting gooseneck to die cast die; extends from gooseneck, through stationary platen, to die cast die; its heated to keep the metal liquid in the nozzle Tube connecting gooseneck to die cast die; extends from gooseneck, through stationary platen, to die cast die; its heated to keep the metal liquid in the nozzle b Sprue bushing What the nozzle seats against; cooled to assure the metal in it freezes What the nozzle seats against; cooled to assure the metal in it freezes

9 Hot Chamber Machine Cycle 3-8

10 3-10 Hot Chamber Process Uses b For low melting point alloys and alloys with a small aluminum constituent b These alloys include those made from: Lead Lead Tin Tin The Zamak family of zinc alloys, ZA8 zinc alloy and a small amount of AZ91D magnesium alloy The Zamak family of zinc alloys, ZA8 zinc alloy and a small amount of AZ91D magnesium alloy

11 3-11 Cold Chamber Components b C-frame Structural framework that supports the shot components; mounted to stationary platen Structural framework that supports the shot components; mounted to stationary platen b Shot cylinder Mounted to the C-Frame; injects metal with its horizontal stroke Mounted to the C-Frame; injects metal with its horizontal stroke

12 3-12 b Coupling Connects the shot cylinder to the plunger rod and tip Connects the shot cylinder to the plunger rod and tip b Cold chamber Shot sleeve or tube that the plunger slides in to pump the metal Shot sleeve or tube that the plunger slides in to pump the metal Cold Chamber Components

13 3-13 Cold Chamber Components b Plunger rod and tip Pumps the metal; made from highly conductive material and is water-cooled Pumps the metal; made from highly conductive material and is water-cooled Conventional cold chamber plunger tips do not have rings; newest technology indicates that the tip may benefit from a design with rings Conventional cold chamber plunger tips do not have rings; newest technology indicates that the tip may benefit from a design with rings

14 Cold Chamber Machine Cycle 3-14

15 3-15 Cold Chamber Process Uses b Used for high melting point alloys and alloys with a significant aluminum constituent: Aluminum Aluminum Copper Copper Magnesium Magnesium Iron Iron Titanium Titanium Composite materials Composite materials

16 3-16 Hot Chamber Advantages b Metal temperature control is better maintained b Metal transfer not required b Cooling of piston tip and sleeve not required b Fewer oxidation losses

17 3-17 Process Limitations/Variations b Conventional process limited by internal porosity Due to trapped gases or solidification shrinkage Due to trapped gases or solidification shrinkage b New technologies developed to provide denser castings Use vacuum, squeeze casting, or semi-solid and thixotropic melting/casting methods Use vacuum, squeeze casting, or semi-solid and thixotropic melting/casting methods

18 3-18 Vacuum Process b Die cavity evacuated using a vacuum pump b Several commercially available systems b Limitations to how complete a vacuum can be achieved; inches of mercury seems adequate for most applications

19 3-19 Squeeze Casting b Gate velocity is much lower b Gate thickness is much higher b Metal pressures at the end of cavity filling are much higher

20 3-20 Semi-Solid Casting b Alloy cast is part liquid and part solid Premise: defects form during solidification; solids therefore should be free of defects Premise: defects form during solidification; solids therefore should be free of defects b Billet of material is preheated to casting temp. in a specially constructed induction heater b Billet placed in cold chamber, then injected b Uses low gate velocities and high metal pressures to make very dense castings

21 3-21 Thixotropic Casting b Takes advantage of the thixotropy of alloy When injected and forced through the gate, literally sheared and agitated, it flows like a plastic material When injected and forced through the gate, literally sheared and agitated, it flows like a plastic material b Injection system is a combination of the screw used in plastic injection and the plunger used in conventional die casting

22 3-22 Summary b Two major processes Components are similar Components are similar Process used is based on alloys melting point Process used is based on alloys melting point Hot chamber process has several advantages Hot chamber process has several advantages b Process variations are based on new technologies Try to overcome conventional die castings limitation of internal porosity Try to overcome conventional die castings limitation of internal porosity


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