05 feed system design
DESCRIPTION
05 Feed System DesignTRANSCRIPT
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e UN CFC – India – Zinc Die Casting
Joe Annetts
International Zinc Association
Die Design – Feed System and Thermal
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• Feed system design along with thermal design
are elements of die design.
• Both are critical elements of the die casting
process.
• They play a major role in defining casting
quality and cost
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Casting Defects
Porosity and flow marks make up around 80% of casting defects
• Poor feed system design is the major cause of porosity.
• Poor feed system and poor thermal design and control, are the
major cause of flow marks.
Porosity Flow Marks
Macro
Micro
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• The so called “tapered runner” method – optimises feed system
design
• Developed by IZA in 1970’s.
• Accepted around the world, but penetration of the method still
limited
• “Tapered runner” refers to the continuous and smooth reduction in
cross section area from nozzle to gate.
• But there is much more to it
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DEFINE THE CAVITY FILL
PATTERN WANTED
SELECT GATE LENGTH,
POSITION TO ACHIEVE FILL
PATTERN
DESIGN RUNNERS FROM
NOZZLE TO GATE TO
ACHIEVE DESIRED FILL
PATTERN
DEFINE FILL CONDITIONS
AND CALCULATE GATE
AREA TO ACHIEVE THIS.
CALCULATE GATE
THICKNESSES
DESIGN VENTS
DIECASTING
MACHINE INJECTION
CAPACITY
PRESSURE/FLOW
LOSSES -
DISCHARGE
COEFFICIENT
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Air pushed out through vents
Gate
Good filling
pattern - air
pushed
ahead of
uniform
metal flow
Poor filling pattern
resulting in flow
around the outside
of the cavity and
air entrapment
Gate
Vents blocked off before cavity fills
Cavity Filling Pattern
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Design Runners from Gate to Nozzle
A B
C
E
F
D Nozzle
Outlet
A B
D C
G
A
T
E
Cross
Section
Area
Gate
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Flow Angle
1) Flow component
along the runner
2) Flow
component
due to metal
pressure at
the gate
Resultant metal
flow direction
FlowAngle
Runner
A Gate = length X thickness
Ain
0 1.0 2.0
Ain / Ag
Flow
Angle
(degrees)
10
30
50
70
45
For example:
1. If the ratio is
1:1 the flow angle
will be 45 deg
2. If the ratio is
2.0 the flow angle
will be 27 deg
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Calculating gate area -& defining cavity fill conditions
MACHINE
INJECTION
ENERGY
PRESSURE
LOSSES IN
FLOW
SYSTEM
ENERGY AT
GATE DEFINES
GATE SPEED
AND FILL TIME
The recommended filling conditions are:
* Plating quality castings - Gate Velocity 40 to 50 metres/ second
Cavity Fill Time 0.01 to 0.02 seconds
* Other casting - Gate Velocity 40 to 50 metres / second
Cavity Fill Time 0.01 to 0.04 seconds
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Calculation of the Optimum Gate Area - When P - Q squared data not
available
Casting Volume ( cubic mm) = Casting Weight (gms)
0.00612 gms/ cubic mm
(Density of molten zinc alloy #3 = 0.00612 gms/ cubic mm)
Select a desired combination of gate speed and cavity fill time from the above
data and then calculate the gate area by substituting in the following equation:
Gate Area ( square mm) = Casting Volume (cubic mm)
Cavity fill time (seconds) X Gate speed (mm/second)
Calculating gate area
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Design Runners from Gate to Nozzle – design features
Sprue runners Sprue cone wall
0.0 - 0.3mm thick
Cross section through a cast sprue cone
2 – 4 mm
Sprue Design
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Design Runners from Gate to Nozzle – design features
Rule 1 - Gated “Y” junction : Ain = 110% x ( Aout1 + Aout2 )
Aout1 = Aout3 +Ag1 & Aout2 = Aout4 +Ag2
Rule 2 - The runner is not gated across the whole “Y” junction, the centre part is un gated
as shown in the diagram
Ain
Aout3 Aout4 Ag1 Ag2
Ain
Aout1 Aout2
Rule - Splitting an ungated “Y” junction: Ain = 110% (Aout1 + Aout2) - this type of “Y”
junction is commonly used to split a single runner into two runners to feed two cavities
Aout1
Aout2
‘Y’ Junction
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Design Runners from Gate to Nozzle – design features
2a
a
a
10 degrees
2a 45 degrees
Runner cross section - ungated Runner cross section - gated
Gate
Recommended runner cross sections
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Design Vents
GATE = 100mm X 0.3mm = 30 sq mm
Vent Area = 10 to 20% of gate area
At 10% of gate area, vent area = 3 sq mm
At 0.05mm gate thickness, vent length = 60 mm
20mm 20mm 20mm
VENT VENT VENT 0.05 – 0.15mm GATE
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Overflow at
point of last
fill Main
runner
Gated bends
“tangential”
runners
Sprue
using
“sprue
runner”
Shock absorber
Example of a “tapered runner” shot
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Example of a short shot
Use of long, thin
gate to achieve
optimum fill
pattern
An example of a Y junction
This
area not
gated
“Short
Shot”
shows
flow
pattern
as
predicted
from flow
angle
consider
ation
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Findings from Project:
• Short Shots
• Casting Yield
• Defects linked to feed system design
• Design work done and outcomes
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Short Shots 1
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Short Shots 2
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Short Shots 3
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Casting yield = weight of casting / total shot weight X100%
Casting Runners Sprue
Overflows Casting
Total Shot Weight = 200 grams Casting Weight = 75 gms
Casting yield = 75/200 X100 = 37.5%
Casting Yield
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Factory Shots measured
Minimum %
Maximum %
Average %
1 13 46 85 57
2 6 30 49 37
3 5 30 83 48
Good Yield = 60% +
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Zin
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Zin
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