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Knowledge - basic

Vacuum industrial definition

Pressure of specific space is lower than at mospheric pressure (JISZ8126)
Reference Vacuum unit
P2 (Specific space) < P1 (Atmospheric pressure)
1atm = 760Torr = 1.01325×105Pa = 1.01325×102kPa
<Refer, Unit vacuum>
Low Vacuum 100kPa~ 100Pa (Common vacuum die casting)
Mid Vacuum 100Pa ~0.1Pa
High Vacuum 0.1Pa ~10-5 Pa
Knowledge - basic 2
Reference  gas exhaust speed
Please refer to left picture,cross section of valve is decided by following condition.
Exhaust speed V=250 〜 280m/s (Sound velocity 340m/s)
V x S > V1 x S
V : Exhaust speed
S : Valve cross section
V1 :Plunger speed
S1 :Plunger cross section
Gas of die casting produce and solution
Gas of mold cavity and sleeve

Vacuum die casting can solve this gas completely.

Gas of release agent

Please use water soluble release agent or
make sure temperature of mold is higher than 120 degrees Celsius.

Gas of chip lubricant

If chip lubricant is not used any more,  no such gas happens.

Relationship between gas value and product quality
We judge quality by gas value
Gasvalue and Quality evaluation
  • Less than 2cc/100g T6 is possible, very good quality T6
  • 5~10cc/100g Very good quality
  • 10~15cc/100g Good quality 15~25cc/100g Unstable quality
  • Higher than 25cc/100g Defective percentage is high
  • Gas value of vacuum die casting is 7~13cc/100g
Bad gas of castings and reason
  • Gas type Reason
  • N2 If no vacuum suction, nitrogen of air is involved
  • H2 When mold temperature is too low, water of
    release agent is involved
  • O2 Not involved
Reference density value and quality evaluation (ADC12)
Density value and Quality evaluation
  • Low than 2.68 = Low quality
  • 2.68~2.70 = Unstable quality
  • 2.70~2.72 = Good quality
  • 2.765 = So far, this is the best density
    by using our company’s vacuum system

Vacuum Casting Process