03.07.2025 by Viktor Siebert

Loss of Power: “I can no longer machine heavy parts.”

A long-time customer contacted us with a clear issue: his Mitsubishi MDS-B-SP-260 spindle drive had lost performance over the years. At first, the problem was subtle. But eventually, the machine was no longer able to process heavier workpieces with the usual power and precision—a clear indication that the drive was no longer delivering full output.

First Countermeasures: Program adjustments and reduced feeds

The customer initially tried to compensate by adjusting the machining programs. Feeds were lowered, cycle times were extended, and cutting parameters were softened. This worked for a while—but the performance gap kept growing.

Red Flag: “Overload” errors occurring more and more frequently

Soon, the “Overload” alarm became a daily issue—appearing multiple times per shift. This kind of error typically indicates:

• Deterioration of power electronics
• Overload of aging internal components
• Thermal buildup or fan failure
• Capacitor degradation

In many cases, it also reflects unstable current regulation—an early warning sign that preventive action is needed before major damage occurs.

Smart Decision: Repair before total failure

Fortunately, the customer made the right decision and contacted us before things got worse. He requested a professional overhaul before the spindle drive caused a full production stop or damaged surrounding equipment like the motor or power supply unit.

Our Preventive Repair Process: Standardized, tested, documented

We’ve developed a structured and proven repair process for MDS-B-SP-260 drives, based on many years of field experience:

Visual Inspection & Analysis

• Check for visible damage, thermal wear, and signs of previous repairs
• Review the fault history (if available)
• Inspect fan function, terminal connections, and interface ports

Electronic Diagnostics & Component Replacement

• Replace all known wear-prone components—regardless of their current status
• Exchange of capacitors, relays, IGBT modules, gate drivers, and opto-couplers
• Cleaning and resealing of heat-conducting surfaces
• Fan replacement or overhaul

Load Testing on Test Bench

• Functional testing under 200 V / 3-phase simulated load
• Simulated real-world operation with overload pulses
• Temperature, voltage, and current monitored throughout

Final Inspection & Documentation

• Isolation resistance check, ripple current test, and leak current measurement
• Full documentation of replaced parts and performed actions
• Drive serial number logged for traceability

Our Tip: Don’t wait for the next error

Spindle drives like the MDS-B-SP-260 are the heart of your CNC machine. Declining performance or recurring errors are not minor annoyances—they’re your system’s early warning signals. Acting quickly can save downtime, reduce costs, and prevent catastrophic failures.

To mentioned Mitsubishi Drive: Mitsubishi MDS-B-SP-260 Spindle Drive Unit

More details about our Mitsubishi repair services can be found here:
Mitsubishi drive Repair by Industrypart

📞 Feel free to contact us with any questions about your Mitsubishi drive technology.
Our expert team is happy to help!

Technical Specifications – Mitsubishi MDS-B-SP-260

Parameter	Specification
Model	MDS-B-SP-260
Drive Type	AC Spindle Drive Unit
Rated Output Power	26 kW
Input Voltage	DC 270–311 V (from power supply unit)
Input Current	115 A DC
Input AC (for fan etc.)	0.2 A, 1-phase, 200–230 V, 50/60 Hz
Output Current	97 A
Output Voltage	3-phase, 200 V, 0–833 Hz
Cooling	Forced air cooling (internal fan)
Installation	Panel mounting in control cabinet
Dimensions (H×W×D)	380 × 150 × 300 mm
Weight	10.0 kg
Manual Reference	BNP-B3759B (Specification Manual)
Compatible Power Supply	MDS-B-CV-260 (DC power supply unit, 260 V, 97 A compatible)
Environment (Operation)	0–55 °C, 90% RH or less, no condensation, indoor use only
Environment (Storage)	−15 to +70 °C, dry, dust-free storage

Alarm and Warning Messages – Mitsubishi MDS-B-SP-260

Alarm No.	Abbr.	Name	Description
12	ME1	Memory error 1	A checksum or RAM error occurred in the spindle drive control card ROM
13	SWE	Software process error	Software process did not finish within the set time
17	ADE	AD error	The AD converter did not function correctly during initialization
21	NS2	No signal (spindle encoder)	No signal input from spindle encoder or abnormal signal level
23	OSE	Excessive speed deflection	Speed command and actual speed deviation exceeded specified limits
31	OS	Overspeed	Motor speed exceeded 115% of the maximum set speed
32	PMOC	Power module overcurrent	Current exceeding the set value flowed into the IPM of the drive
34	DP	CRC error	CRC error occurred in communication data from the NC
35	DE	Data error	NC movement command exceeded limit during position control
36	TE	Transmission error	Periodic data transmission from NC was interrupted
37	PE	Parameter error	A parameter value exceeding the tolerable range was set
38	TP1	Protocol error 1	Protocol error in NC communication (frame level)
39	TP2	Protocol error 2	Protocol error in NC communication (information level)
40	KE1	TK unit change error	Changeover signal procedure was incorrect using the TK unit
41	KE2	TK unit communication error	Communication with TK unit was incorrect
44	CAXE	C-axis changeover alarm	Coil changeover alarm when using H coil for C-axis control
46	OHM	Motor overheat	Overload or cooling blower stop caused thermal protection to activate
50	OL	Overload	Motor current exceeded the set overload time constant
52	OD	Excessive error	Position tracking error exceeded specified limits in the loop control
5C	ORFE	Orientation feedback error	Orientation pulse value was outside the set range at orientation complete
60–7F	–	–	Refer to power supply section for related alarms
82	NSP	Power supply no signal	Breakage or misconnection of cable from power supply detected
E1	WOL	Overload warning	Motor current exceeded 80% of detection time constant
E7	NCE	NC emergency stop	Emergency stop signal received from the CNC