How Does Sequence Injection Timer Work?

sequential valve gate controller types

For those who are new to the injection molding industry, may be confused about this product. This article will introduce you the usage, types, and advantages of the Sequence Injection Timer. And how to use the 3 modes of the sequential controller correctly to prevent burn marks, weld line, short shot, and other part defects in injection molding.

In fact, it is simple to operate, the difficulty is how to debug in production, change the melt flow, to achieve the product quality requirements. It is not used in general hot runner systems, but large, complex products will use the hot runner sequential controller. In recent years, major automotive companies are using hot runner valve gate systems, which could effectively change the appearance of the product quality.

General Schematic

hot runner valve gate system Schematic

Uses

The sequential controller is used for molds with multi-cavity valve gate hot runner systems. Control the flow of plastic into the mold cavity using mechanical shut-off pins that allow the hot runner nozzle to open and close at the tip. The quality of the moulded part can be improved by removing or re-positioning of weld lines on visual surfaces, or sections where a weld fine would cause a weakness.

hot runner valve gate system Schematic

Sequence Injection Timer Types

sequential valve gate controller types

It’s divided into two common types: Modular plug-in sequential control system (max. 24 gates) and 8 gates timer control. But at Hitcontrols, besides common types, we provide optional touch screen 8 gates sequence timer, and high-cavity combined temperature control & sequential timer control.

Standard power supply, single phase AC220V/50,60Hz. Input signal: DC24V or Switch. Output voltage: DC24V or AC 220V.

sequential injection controller wiring

The modular plug-in sequential controller is more functional, with three modes to choose from. Like the hot runner temperature controller, the module can be flexibly removed for easy maintenance and expansion. Compact type, most of them have only 8 groups of gate control, two modes selection. But it can meet most of the molding needs. Compact volume, convenient in installation. Hitcontrols’ 8-gate sequential controller support 3 modes of selection, contact us for details.

Advantages

  1. Removal or Positioning of Weld Lines

Weld line injection molded part

For large plastic products such as electrical shells, and automobile door panels with strict shape requirements, there should be at least two or more filling gates to fill the product for a set hot runner system mould. For common hot runner system, the gates are filled at the same time during injection.

If the product needs to change the weld line position, can only be changed the melt flow rate through the temperature difference from hot runner temperature controller. Process debugging is complicated and tedious, and it is difficult to ensure stable product quality and bring passive production efficiency.

But with a sequence timer controller, only need to adjust the gate opening time & closing time, to change the melt flow position and achieve the weld line position displacement. Although it also takes time to debug, it can ensure long-term stable production without defects caused by the temperature differences of the hot runner gate.

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2. Regulation of the Injection Quantity by Gate Operation

weld line, flash, short shot, burn marks in injection molding

Short shots, flash, burn marks could be improved by the regulation of the Injection Quantity from each individual gate.

For the hot runner system with more than two drops, when defects such as flash, short cavity, burn marks in the injection molding processing. Usually to adjust the defects through multi-stage injection’s pressure speed. Moreover, sometimes it is difficult to debug and can only be solved by mold repair. Using the sequence timer controller, product defects can be improved by changing the opening time and closing time of individual valve gates.

3. Reduction of Clamping Force

Injection is performed with minimum clamping force because all of the gates are not opened simultaneously.

4. Reduction of Flow Marks

Flow marks are minimised by being able to raise the injection rate of the gate.

Sequence Injection Timer Mode Type Selection

General sequence timer controllers may be set in three modes. The opening/closing operation of the gate differs according to the setting mode as illustrated below

The user can adjust Gate open/close/delay time for the optional injection application in a convenient way.

Mode A (Continuous Sequence)

sequence timer Mode A

After the injection signal has been received, the gate remains closed during the DEL time. After the DEL time has elapsed, the gate opens and remains open until the end of the injection signal.
Example: Injection time 10 seconds/DEL time 3 seconds: Gate opens 3 seconds after receiving the injection signal and remains open for 7 seconds and then closes.

Mode B (Intermittent Sequence)

sequential controller Mode B

After the injection signal has been received, the gate remains closed during the DEL time. After the DEL time has elapsed, the gate opens for the OPEN time setting. After the OPEN time has elapsed, the gate closes and remains closed.
Example: Injection time 10 seconds/DEL time 3 seconds/ OPEN time 4 seconds. Gate opens 3 seconds after receiving the injection signal and remains in the open condition for 4 seconds and then closes.

Mode C (Delay Sequence)

sequence injection timer Mode C

In Mode C, users can carry out Mode B operation twice successively.

Example: Injection time: 20 seconds. The first Del. time: 3 seconds, the first Open time: 4 seconds. The second Del. time: 5 seconds, the second Open time: 6 seconds.

Operation: After 3 sec. delay, the Gate opens for 4 seconds. Successively after 5 sec. close, the Gate opens for 6 seconds.

How To Convert The MODE Setting

sequence injection controller mode selection

(here is take Hitcontrols SVG-H8 for example). Press MODE key for 4 seconds, the buzzer rings, and MODE indicator blink.  1st gate’s mode indicator blinks. Press < or >  to switch Mode A/B/C and gate off. Press ∧ or ∨ for gate switching.

Note: Mode A indicator blinks means Mode A selected, Mode B indicator blinks means Mode B selected, and both A & B indicator blinks mean Mode C.

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Sequence Controller System Application

(here is take Hitcontrols SVG-H8 for example). Press MODE key for 4 seconds, the buzzer rings, and MODE indicator blink.  1st gate’s mode indicator blinks. Press < or >  to switch Mode A/B/C and gate off. Press ∧ or ∨ for gate switching.

Note: Mode A indicator blinks means Mode A selected, Mode B indicator blinks means Mode B selected, and both A & B indicator blinks mean Mode C.

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  1. MODE A application

1.1 In case of short shot on product

Open Gate 1 first to enlarge filling area, then open Gate 2 later to fill up well.

Mode A application_1

1.2 To injection products which have a big dimensional difference per cavity.

Open Gate 1 first to fill up the big size, and then open Gate 2 later to make the balance. It can optimize the injection precision.

Mode A application_2

2. MODE B application

To inject complicated products which have a big dimensional difference, apply MODE 1 for Gate 1-4, and Mode B only for Gate 5. It is used to fill up the very small sizes dimension just before the injection ends.

Mode B application

3. MODE C application

It is used to apply “one and after” injection signal control. Opening the gates first which could have fill-up unbalanced if users open the all gates at the same time, and then close the gates keeping time with fill up.
It is designed to avoid the excessive filling pressure. Although this is also possible in MODE B operation, the function to keep up the holding pressure in channel by opening the Gate (The sequence timer controller itself keeps the injection signal in an open condition) is possible only in MODE C. MODE C is a new type of output pattern which is able to optimize the various sequence controls to match the product feature and injection peculiarity.

Mode C application

“Do you have a problem with hot runner sequence timer controller?”

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