What is vacuum?

Vacuum refers to a state in which the gas pressure of a space is lower than atmospheric pressure, and the standard atmospheric pressure based on sea level is 1 atmosphere pressure, and the sea end unit is as follows.
1atm (1 atmosphere) = 1.0332 kg/㎠ = 1013 mbar = 760 mmHg = 101.325 KPa

Overview

The charging time of the die cast is very short compared to that of general casting. In addition, there is not enough time to exhaust gas from existing air vents to improve quality and reduce defect rates as the shape of the product becomes increasingly complex. Due to the injection effect of the gate during high-speed casting, a large part of the molten metal comes into contact with the internal air and gas of the cavity, which affects the residual gas in the sleeve and affects the quality of the product. Accordingly, the purpose is to improve the quality of the product and solve problems such as existing bubbles, unformedness, and contraction by more actively exhausting air and gas inside the cavity using a vacuum device.

Vacuum die casting method

In the existing die casting method, internal quality defects due to fast charging have long been a concern. This device is a device that forcibly exhausts gas generated during air and hot water by suctioning the cavity inside the mold through vacuum. As a result, problems such as a decrease in the quantity, size, and unformed internal bubbles have been solved and are used in many areas such as automobile parts, oil pumps, water pumps, head drums, case covers for devices, and thin products.

In general, vacuum valve blocks show better vacuum than Chilvent blocks at the same suction volume, but higher vacuum does not mean that a product comes out better, and some molds do not change product quality even when actual vacuum blocks and Chilvent blocks are used alternately. Chilvent molds should remove oil stains, foreign substances, burrs, etc. at least once a day on Chilvent stairs, and vacuum valve blocks should also be disassembled at least once a day to clean, check for scratches on vent pins, operating pins, etc. In some cases, LOT defects occur by working with the lacquer vent covered with dirt (reducing vacuum effect), and in some cases, vent pins or operating pins of the vacuum valve are worn out to the vacuum valve block, so the entire block needs to be replaced.

Currently, Diecast does not use only one casting method, but also vacuum casting and squeeze as needed, and other hot water management, warm-aircraft use, jet cooler, release agent selection, and casting condition management are all items that users should consider for the best quality.

A schematic diagram

Work flow

• 01

  Formation
  closure

• 02

  Melting
  water
  charging

• 03

  Emission

• 04

  Chill

• 05

  Formation
  open

• 06

  Product
  pick-up

• 07

  Spray

• When forming and closingPreparation of vacuum work, pressure setting value or maximum value (vacuum density: max 0.1 mbar)
• When charging molten metalChilvent and general vacuum valve block flow → Preparing for vacuum operation
  TOSHIBA shut valve: vacuumed up to the mold
  TOYO VCS Method: Blocking Runner Pin and Vacuuming Cavity
• Injection STARTChilvent and general vacuum valve block flow → Preparing for vacuum operation
  TOSHIBA shut valve: vacuumed up to the mold
  TOYO VCS method: Open the runner pin and close the vent pin cavity vacuum pressure is decreasing.
• When the molten metal inlet is blockedAt 350 tons or less, vacuum of the cavity is usually started from this point.
  There are two methods of starting a vacuum by a timer after injection advance and specifying the plunger stroke position in a die casting machine.
• Injection fast switchingChilvent, general vacuum valve flow → Continue to vacuum
  TOSHIBA shut valve: Shut valve closed by vacuum END signal in high speed switching

Vacuum signal setting

※ Vacuum start time is different for molds and products, but in small sizes under 350 tons, the plunger usually starts blocking the molten inlet and gives -30-300mm in the high-speed section as it goes larger, and the melt filling rate inside the cavity is 10~30%, calculating the sleeve diameter and molten amount to specify the plunger stroke position.

• Airtightness of Molded Parting Line Molding
• Injection Speed and Vacuum Start Point
• Method of setting the vacuum start position of the lacquer vent and vacuum block
• Make the vacuum hose as short as possible
• Cross Sectional Area of Vacuum Runner and Vacuum Channel
• A Study on the Airtightness of Sleeve and Mold in High Vacuum Mold Design