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3.5 System Setup

The following sections describe the conditions required to startup a thermal or valve gate hot runner system.

3.5.1 Thermal Gate Setup

Thermal Gate (or hot tip) systems only require the connection of the power and

thermocouple cables from the hot runner to the controller. The mold cooling system must also be connected to the hot runner and mold.

CAUTION!

In order to avoid damage to the hot runner, never use more carriage pressure than what is required.

A normal setting for the carriage force is no more than 6804 kg (15000 lb) pushing on the sprue. Excessive carriage force will cause damage to the hot runner and will not be covered under warranty.

Force = (Carriage Cylinder Cross-Sectional Area - Rod Area) x Number of Cylinders x Hydraulic Pressure

CAUTION!

Nozzles must be at room temperature (< 25 °C or < 77 °F) prior to installing the cavity plate to avoid damage to the system at the sealing surfaces.

3–12 Air Operated Valve Gate Setup

3.5.2 Air Operated Valve Gate Setup

• Air operated valve gates (VG) require airline connections to the mold from the machine, in addition to power, thermocouple, and cooling connections.

• Typically, valve gated systems require air pressure between 5.5 to 8.3 bar (80 to 120 psi).

• The maximum available air pressure may be limited in some areas of the United States.

In this case, always use the maximum air pressure set by your region if the maximum allowed is less than what is required by the hot runner.

• Use clean dry air. Do not use lubricated air. An air filter and oil separation kit is available from Husky to meet the requirements of the system. See Section 3.6 for more

information.

• The controls for the solenoid air valves interlock for safe operation. This requires the valve gate air supply to be separate from the other air functions of the mold so that it can remain activated and maintain closed valve gates while other machine air is locked out.

• Never operate the valve stems for more than 2 or 3 shots at startup without resin in the system. Repeated impact of the valve stem on the bare metal of the gate may result in damage to the gate.

• The open time of the valve stems should be adjustable through timers. Generally the valve stems should close just as injection hold times out. See Section 3.6 for more information.

3.6 Recommendations for Optimal Valve Gate Performance

• A quick exhaust valve should be installed on both air lines between the hot runner and solenoid to increase the speed at which the valve stems open and close. This often improves gate quality.

• Air hoses should be rated to at least 17 bar (250 psi) to prevent ballooning of the lines during operation.

• For optimal performance, air pressures up to 12.4 bar (180 psi) may be required for LX and SX pistons.

• All air system components (hoses, valves, fittings, solenoids, exhausts, etc.) should be of adequate size to permit fast air flow to/from the hot runner system, but not so large that time is wasted filling the excess volume of the lines.

• “Airline” shut off type quick connects should not be used unless the mold was designed for their use. They may restrict the airflow.

WARNING!

Hot resin spray hazard – risk of serious injury. Residual pressure may be present in the hot runner and may cause hot resin to spray from the nozzle tips if released. Wear Personal Protective Equipment (PPE) including a face shield over safety glasses, heat resistant gloves and heat resistant clothing whenever entering the mold area.

Additionally, where possible, make sure the hot runner valve gates are closed and the machine nozzle is retracted from the mold sprue to reduce the chance of hot resin unexpectedly spraying into the mold area.

Recommendations for Optimal Valve Gate Performance 3–13

• Air lines between the mold, quick exhausts and the solenoid valve should be as short as possible.

• In most cases the machine valve gate open signal to the valve gate air solenoid should be energized 0.2 to 0.3 seconds before the machine injection signal. This will allow enough time for the valve stem fully open and minimize the effects of side loading and resin flow over the valve stem

• Some injection molding machines allow the valve stem to be opened prior to the mold being put under full clamp tonnage. In this case the valve stem should be energized when the mold faces first touch (clamp up). The time between clamp and latch (full tonnage) is typically enough time for the valve stem to travel to the full open position.

The injection signal would only be enabled after the machine is under full clamp tonnage. This sequence allows optimization of the machine and mold without affecting the cycle time of the tool.

NOTE: If requested, Husky can supply complete air solenoid kits for valve gated systems, including quick exhaust valves, filters, separators and lockouts for the air supply.

Figure 3-8 Valve Gate Air Kit 1. From Air Supply 2. To Mold

WARNING!

Hot resin spray hazard – risk of serious injury. Residual pressure may be present in the hot runner and may cause hot resin to spray from the nozzle tips if released. Do not push on the valve stems when cleaning cavities and wear Personal Protective Equipment (PPE) consisting of a heat-resistant coat, heat-resistant gloves and a full face shield over safety glasses to avoid injury.

3–14 Recommended Startup Procedure

3.7 Recommended Startup Procedure

Before using the hot runner in production, do the following: