DIE CASTING CALCULATIONS 1. Wt of casting (gms) 2. Density(gms/cc): based on alloy used for casting. Al- 2.6 to 2.7; Zn- 7.8; Cu-9; Mg- 1.7 3. Projected Area Casting
: Surface Area (cm2)
4. Volume of Casting cm 3
: (Wt of Comp) / Density
5. Shot Weight = Wt of Casting + (Wt of Runner + Overflow) + Wt of Biscuits Wt of Runner + Overflow – 10% of Wt of Casting Wt of Biscuits – 20% of Wt of Casting 6. Gate Velocity (Vg) in m/sec (Refer Table 2) 7. Gate Thickness – Hg (mm) , Hg = n/3 – n/4 , n – thickness of casting 8. Volume of metal through gate : P (cm3) .
P = vol of casting + vol of overflow (10% of vol of casting)
9. Fill Rate (Q) cm3/sec .
Q = (P x 1000) / t ; t – fill time in milli sec’s
10. Gate area (Ag) (cm2) .
Ag = (Q) / (100 x Vg)
11. Gate Length – Lg (mm) .
Lg = ( Ag x 100 ) / Hg
12. Runner Area – Ar (cm2) .
Ar = 1.25 Ag – 1.6 Ag
13. 13 Runner Depth – D (mm) D = (Ar / 1.6)(1/2) - (Ar / 2)(1/2)
14. Runner Width (W = 2D) (mm) 15. Locking Force – F (Metric Tonnes) .
F = ( A X P) / 1000 i. A – Projected Area (cm2) ii. P – Specific injection pressure ( kg / cm2)
16. Machine Specification:- Select Machine based on the locking force. 17. Effective Plunger Stroke (cms) :– Maximum plunger stroke – 20/25 mm for biscuits 18. Plunger Diameter – d (cm) .
Shot wt = Plunger Area x Eff. Plunger Stroke x 0.75 x 2.5 (gm)
.
Shot wt = [ (Π X d2 ) / 4 ]x Eff. Plunger Stroke Plunger x 0.75 x 2.5 (gm)
.
4 x Shot wt = (Π X d2 ) x Eff. Plunger Stroke x 0.75 x 2.5 (gm)
.
d2 = ( 4 x shot wt) / (Π X Eff. Plunger Stroke x 0.75 x 2.5)
.
d=
√ [ ( 4 x shot wt) / (Π X Eff. Plunger Stroke x 0.75 x 2.5) ]
TABLE I Specific Injection Pressure Zn 100 200 Engineering Parts 200 300 Pressure Tight Parts 250 400 Decorative Parts
3.175 – 3.87 34 – 43 4.572 – 5.08 31 – 40 3.75 - Above 28 – 35 Use lower values for warmer dies and hot metals Use higher values for colder dies and colder metals TABLE III METAL & DIE TEMPERATURE Alloy Zn Alloy Mg Alloy Al Alloy
Metal Temperature 393 C (740 F) 657 C (1215 F) 657 C (1215 F)
Die Temperature 393 C (740 F) 332 C (630 F) 332 C (630 F)
Die Filling Time For Zn, Al, Mg Alloys Average Wall Thickness (mm) Max Die Filling Time (milli sec) 1 10 – 30 1.5 10 – 35 1.8 20 – 40 2.0 30 – 60 2.5 40 – 90 3 50 – 100 4 50 – 120 For higher values – fill time – 7ms for every 0.5mm wall thickness For Brass Average Wall Thickness (mm) 1.5 1.75 2 2.5 3 4
Max Die Filling Time (milli sec) 20 – 25 25 – 30 25 – 35 30 – 40 35 – 45 40 – 50
Highest value apply for Al Medium value apply for Zn Lowest value apply for Mg TABLE IV Gate Thickness Wall Thickness (mm) Gate Thickness (mm) Al Mg
Ejection System Assuming ejecting area to be 4% of the area of the casting Total Ejecting area = Projected area of Component X 4% Area of selected Ejector Pin Diameter = A Area of Ejector Pin = ( Π X A2 ) / 4 No of Ejector Pins Required = Total Ejection Area / Area of Ejection Pin
