Drive interface board of an injection molding machine

A drive interface board connects the controller of an injection molding machine to its servo drive or frequency inverter. It passes the speed and pressure commands from the main CPU board to the drive and reads back the drive's status, such as ready, running and fault. On a servo-hydraulic machine, this link decides how fast the pump motor turns and how much pressure it builds in each step of the cycle.

Where the drive interface board sits

The board is mounted in the electrical cabinet with the CPU, I/O and power supply boards, as the drawing shows. A signal cable runs from it to the control terminals of the servo drive. Our drive interface board is described for servo drive and frequency inverter communication, runs on 24 V DC and is listed for Haitian MA and MA II series machines.

What signals it carries

The exact signals depend on the controller and the drive, but they fall into three groups:

• Commands: the flow (speed) and pressure set values for the current step of the cycle. They are sent as analog signals, commonly voltages in a 0–10 V range, or over a digital communication link.
• Control signals: on/off signals such as drive enable, start and fault reset.
• Status and feedback: drive ready, drive fault and alarm signals, and on some systems the actual speed or pressure.

On a servo-hydraulic machine, the pump has to deliver a set flow until the set pressure is reached and then hold that pressure. Depending on the system, the pressure loop is closed in the servo drive, which then reads a pressure transducer directly, or in the controller. The servo pump guide explains the hydraulic side.

Signs of a faulty drive interface board

• The panel shows "drive not ready" or a drive communication alarm while the drive itself shows no fault.
• The pump motor does not start, or runs but builds no pressure, although the drive is healthy.
• Speed or pressure does not follow the settings, or is unstable, in every movement rather than in one.
• The drive cannot be reset from the operator panel.

The same symptoms come from a damaged signal cable, a loose connector, a broken cable shield or poor grounding that lets electrical noise into the analog signals, and from faults in the drive itself. Always read the alarm code on the drive's own display first.

Inspecting and replacing a drive interface board

Measurements on live circuits and board replacement are for qualified electricians. Replace the board only with the machine switched off at the main isolator and locked out.

1. Read the alarms on the operator panel and on the servo drive's display, and look them up in both manuals.
2. Check the signal cable and its connectors at both ends, and that the shield is connected as the wiring diagram shows.
3. With the machine in a safe state, have the electrician measure the command signals at the drive terminals while a movement is called in manual mode.
4. Isolate and lock out the machine, wear a grounded wrist strap, photograph the board and label the connectors.
5. Fit a board of the same model, set any switches or jumpers as on the old one, and reconnect.
6. Check that speed and pressure follow the settings. Some machines need the pressure and flow calibration repeated after the drive control is changed; follow the machine manual.

What to send for a replacement quote

• The machine brand, model and serial number.
• The controller model printed on the operator panel and the boards, and the servo drive or inverter model from its nameplate.
• The board's model number or label, and photos of both sides with the connectors.
• The alarm codes shown on the panel and on the drive.

See the controller guide for the CPU board that sends the commands, the power supply board guide for the supply it runs on, and the electrical system guide for the overview.