Commonly used formulas for injection molding machines

1. Clamping force F(TON) F=Am*Pv/1000
F: Clamping force TON Am: Cavity projection area CM2
Pv: FILLING PRESSURE KG/CM2
(GENERALLY, THE FILLING PRESSURE OF PLASTIC MATERIALS IS 150-350KG/CM2)
(The lower value is taken for good flow, and the higher value is taken for poor flow)
Filling pressure/0.4-0.6 = injection pressure
FOR EXAMPLE, THE PROJECTION AREA OF THE CAVITY IS 270CM2 AND THE FILLING PRESSURE IS 220KG/CM2
CLAMPING FORCE = 270 * 220/1000 = 59.4TON
2. Injection pressure Pi KG/CM2 Pi=P*A/Ao
Pi: Injection pressure P: Pump pressure A: Effective area of injection cylinder
AO: Screw cross-sectional area
A= π*D2/4 D: Diameter π: Pi 3.14159
Example 1: Knowing the pumping pressure Finding the injection pressure?
PUMP PRESSURE = 75 KG/CM2 EFFECTIVE AREA OF INJECTION CYLINDER = 150CM2
SCREW cross-sectional area = 15.9CM2 (∮45)
Pi=75*150/15.9=707 KG/CM2
Example 2: Pump pressure is known to be pumped?
REQUIRED INJECTION PRESSURE = 900 KG/CM2 EFFECTIVE AREA OF INJECTION CYLINDER = 150CM2
SCREW cross-sectional area = 15.9CM2 (∮45)
PUMPING PRESSURE P= Pi*Ao/A=900*15.9/150=95.4 KG/CM2
3. Injection volume V CM3 V= π*Do2/4*ST
V: Injection volume CM3 π: Pi Do: Screw diameter CM
ST: INJECTION STROKE CM
For example, the diameter of the screw is 42mm, and the injection stroke is 165mm
V= π*4.2*4.2/4*16.5=228.6CM3
4. Injection weight G Vw=V*η*δ
Vw: Injection weight G V: Injection volume η: Specific gravity δ: Mechanical efficiency
EXAMPLE: INJECTION VOLUME=228.6 CM3 MECHANICAL EFFICIENCY=0.85 SPECIFIC GRAVITY=0.92
Injection weight Vw=228.6*0.85*0.92=178.7G
5. Injection speed S CM/SEC S=Q/A
S: Injection speed CM/SEC Qr: Pump discharge (per revolution/CC) CC/REV
A: Effective area of injection cylinder CM2 Q=Qr*RPM/60 (per minute/L)
Q: Pump output RPM: motor rotation per minute
FOR EXAMPLE, THE MOTOR SPEED IS 1000RPM, AND THE PUMP OUTPUT IS 85 CC/REV
THE EFFECTIVE AREA OF THE INJECTION CYLINDER IS 140 CM2
S=85*1000/60/140=10.1 CM/SEC
6. Injection rate Sv G/SEC Sv=S*Ao
Sv: Injection Rate G/SEC S: Injection Speed CM/SEC Ao: Screw cross-sectional area
EXAMPLE: INJECTION SPEED = 10CM/SEC SCREW DIAMETER ∮42
AREA = 3.14159 * 4.2 * 4.2/4 = 13.85CM2
Sv=13.85*10=138.5G/SEC