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We provide onsite support to our customers - any machine tool, any age

Experience in all CNC manufacturing industry fields, including automotive, aerospace, textiles, food & beverage, petrochemicals, R&D, science & education

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Blog Post

26th October 2018

Common Failure on CCU Boxes

"There's a funny smell coming from the electrical cabinet." The 50A spindle drive on the Siemens 810D went bang. All three phases failed the diode test (no surprise there).

This is a fairly common failure on CCU boxes, specifically on the 50A spindle drive.

Regularly check that the connections are tight and if you have a Meger, check the motor and power cable resistance. Infinity readings are what we like to see; however, if you get readings over 100 mg/ohms, your motor should be OK.

At Control CNC, we always do a full health check whenever we attend a failure like this, as quite often failures like this are caused by something else failing, such as a cable or motor.

In this case, one of the blocks in the drive failed. Regular preventative maintenance can lessen the chance of failures like this. Look after your machine and your machine will keep on producing!

Diode Failure
multiple X axis alarms

Previous Post

2nd October 2018

Looking at a Hardinge 710 Mill with 828D and Sinamics drives today with multiple X axis alarms. After a few tests, a faulty motor was diagnosed, more specifically the SMI 20 unit, which had failed to break the motor encoder communications to drive.

YouTube Video for Healthy CCU Start-Up

Next Post

26th November 2018

This is the Siemens 810D CCU start-up procedure from power on to completed boot. A healthy CCU is a number 6, green +5v, green PR and a flashing amber CB.

The whole process takes around 1 minute..


A family business established in 2016, Control CNC Services Ltd. has over 30 years of experience in the CNC machine tool industry. 

Our engineers support all aspects of CNC applications. We provide a total breakdown solutions package; whether the fault is mechanical, electrical, electronic, software, control, or drive, our multi-disciplined engineers will resolve the problem.

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