Extrusion Machine HMI Alarm Troubleshooting: Mold Temperature and Emergency Stop Problems

Description

During the daily operation of an extrusion production line, some alarm messages may appear on the HMI screen. For machines that have already worked for several years, this is quite normal. The alarm may come from one simple problem, but sometimes it can also be related to electrical parts, oil circulation or other components.

From the HMI screen shown in the picture, we can see alarms such as Mold Temperature Low Pressure and Auxiliary Emergency Stop Pressed.

Floor extrusion equipment2

Below we share some common checking methods for these two problems.

1. Mold Temperature Machine Temperature Is Too Low

When the HMI shows a mold temperature machine alarm, the first thing is to check the actual temperature and the setting temperature.

If the actual temperature is much lower than the set temperature, the mold temperature controller may not be heating normally.

You can check the following points:

1. Check the heating tube

Check whether the heating tube is damaged and whether it is heating normally. If one or more heating tubes are damaged, the oil temperature may rise very slowly or cannot reach the set temperature.

2. Check the oil pressure

Check whether the oil pressure of the mold temperature machine is normal. If the pressure is too low, it may cause a low-pressure alarm. The pressure can be adjusted on the oil temperature controller according to the machine condition.

3. Check the oil level

Make sure there is enough heat transfer oil inside the system. Oil shortage may affect oil circulation and heating performance.

4. Check the heating contactor

Check whether the heating contactor can pull in normally. If the contactor does not work, the heating system may not receive power even if the HMI shows a heating command.

5. Check the temperature sensor

A damaged temperature sensor can send an incorrect temperature signal to the PLC. In this case, the real oil temperature may be normal, but the HMI still shows an abnormal value or gives an alarm.

What If the Alarm Appears Just After Starting the Machine?

If this alarm appears immediately after starting the extrusion line, it does not always mean that a component is damaged.

The oil and mold may still be cold, especially after the machine has stopped for a long time. We suggest running the heating system for some time and checking whether the actual temperature and pressure gradually become normal.

If the alarm disappears after the temperature rises, usually further repair is not necessary.

2. Emergency Stop Alarm on the HMI

Another alarm shown on the screen is:

“Auxiliary Emerg Stop Pressed”

For this alarm, first check all emergency stop buttons on the machine and make sure they have been correctly reset.

After resetting, clear the alarm and check the machine again.

If the emergency stop alarm is still there, there may be other problems, such as:

• Emergency stop button damaged
• Loose electrical connection
• Broken wire or poor contact
• PLC input signal problem
• Electrical contact or relay problem

In this situation, the electrical circuit should be checked step by step.

Older Extrusion Machines May Have More Possible Causes

For an extrusion machine that has been running for many years, troubleshooting cannot only depend on the alarm message shown on the HMI.

For example, a mold temperature low-pressure alarm may also be caused by blocked oil pipelines, dirty filters, poor oil circulation, oil pump problems or aging electrical components.

In some cases, the machine itself is working normally, but a PLC module contact, relay or signal connection has become unstable after long-term operation.

So the HMI alarm should be considered as the starting point for troubleshooting, not the final diagnosis.

Check the Actual Machine Condition

Every extrusion line has different working hours, maintenance conditions and production environments. The same alarm message can have different causes on different machines.

For simple problems, operators can first check the temperature, oil level, pressure, emergency stop buttons and electrical connections.

If the alarm continues after these basic checks, we recommend asking an experienced mechanical or electrical maintenance technician to inspect the machine on site and eliminate the possible causes one by one.

Regular inspection of the mold temperature controller, heating system, oil circuit, sensors and electrical components can also help reduce unexpected downtime and keep the extrusion line running more stably.