Initial situation and fault description.

The Okuma Servo Drive MIV06DB-1-B1 with Okuma part number 1006-2265 was sent to us with the information that alarm A.L. 04 occurred only occasionally. According to the technician’s report, the drive had been tested on the CNC machine with an external motor. When attempting to rotate the motor, an overcurrent alarm was triggered sporadically and immediately. The fault could not be reproduced consistently, which made diagnosis considerably more difficult.

Such intermittent overcurrent alarms often lead to incorrect assumptions in practice. In many cases, the motor, mechanics or cabling are suspected first, although the actual cause lies within the drive itself or in the surrounding environmental conditions.

Findings during incoming inspection

Already during the initial opening of the unit, it became apparent that the drive was heavily contaminated internally. A closer inspection revealed that this was not ordinary dust or oil residue, but fine graphite deposits. This type of contamination is particularly critical for electronic assemblies.

Graphite is electrically conductive. If it accumulates across PCB tracks, component leads or heat sinks, the insulation resistance can be significantly reduced. This leads to unintended current paths, distorted measurement signals and, ultimately, protective shutdowns such as overcurrent alarms that appear to occur without a clear pattern.

Analysis of environmental conditions

Based on the extent of the contamination, it was immediately clear that these deposits could not have formed over a short period of time. The graphite had accumulated over a long operating period. We contacted the customer and informed them in detail about our findings.

During the subsequent discussion, the suspicion was confirmed. The machine in question regularly processes components involving graphite-containing materials. This clearly identified the root cause. In such cases, it is particularly critical that not only a single drive is affected. As a rule, other electronic assemblies in the control cabinet are exposed to similar conditions.

For this reason, we strongly recommended inspecting additional drives and electronic components of the machine for contamination.

Preventive measures and extension of the repair scope

After this clarification, the customer decided to send further units for inspection and cleaning. These showed very similar conditions. Some of the units were still operating without active alarms at the time, but already exhibited significant deposits that would inevitably have led to failures in the medium term.

The originally submitted MIV06DB-1-B1 was therefore not only repaired but also preventively overhauled. The objective was not merely to eliminate the current fault, but to restore the long-term operational reliability of the drive.

Repair and overhaul process

The first step involved a complete and professional cleaning of all assemblies. All printed circuit boards, heat sinks, connectors and transitions between the power and control sections were thoroughly cleaned of graphite residues. These transition areas are particularly sensitive in graphite-laden environments, as power currents and sensitive control signals converge there.

Afterwards, all relevant assemblies underwent a detailed visual and electrical inspection. The goal was to ensure that the conductive deposits had not caused permanent damage to PCB traces, insulation distances or components. Only after these inspections were completed was the drive reassembled.

Functional testing under load on the in-house machine

Following the preventive overhaul, the Okuma Servo Drive was tested on our in-house machine under real load conditions. The drive operated stably over an extended period without any recurrence of overcurrent alarms or secondary fault messages. Start-up behavior, current consumption, control stability and thermal performance all remained within the specified nominal ranges.

Especially in cases where faults originally occurred only sporadically, such a load test is essential. Only under realistic operating conditions can it be reliably determined whether a drive will function consistently in long-term operation or whether hidden weaknesses remain.

Final inspection and release

After successfully completing the endurance and load tests, the MIV06DB-1-B1 was fully documented and released for return shipment. The customer was additionally advised to implement regular cleaning and inspection intervals for electronic assemblies when operating in graphite-contaminated environments.

This case clearly demonstrates that not every malfunction is caused by a classic electrical defect. Environmental conditions and process residues play a decisive role in the service life and reliability of servo and drive electronics. Early maintenance and preventive overhaul can effectively prevent unplanned downtime and consequential damage.

Price and Delivery Time for Okuma Servo Drive Unit MIV06DB-1-B1 Teilenummer 1006-2265

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Technical Specifications

Operating environment and compatible devices

The Okuma MIV06DB-1-B1 is a single-axis servo inverter from the MIV series and is used in Okuma CNC machines to control axis motors. Typical applications include turning machines, machining centers and special-purpose machines equipped with OSP controls. The drive operates in combination with central Okuma power supply units of the MPS or MPR series and is designed for BL and PREX motors.

Functional description

The MIV06DB-1-B1 Drive Unit converts the DC voltage supplied by the central DC bus into precisely controlled motor currents. Via the Okuma servo link system, the drive communicates with the CNC control and receives setpoints for torque, speed and position. Integrated protection functions monitor motor current, temperature, DC bus voltage and internal signals. In the event of deviations, operation is immediately stopped and a corresponding alarm is displayed via the 7-segment LED.

Alarm messages and troubleshooting (excerpt)

Components – Okuma Servo Drive Unit MIV06DB-1-B1 (1006-2265)