MZI Precision rebuilds spindle motors of all makes and models. Some are separate drive motors that are belt or coupled to the spindle. Integral motors are built into the spindle, typically between the bearings. Motor testing is part of every inspection. Rewinding is done through a specialist rewind partner we have worked with for years. Integral motor spindles take about twice the labor of a plain spindle, and this page explains where that time goes.

Different kinds of motors that drive the spindle

Separate drive motors. A Fanuc, Mitsubishi or similar motor sits above, beside or behind the spindle and drives it through a belt or a coupling. Some motors are servo types. The motor is tested, disassembled, cleaned and inspected like a spindle. Bearings are replaced, and it is rewound if the windings are bad.

Integral motor spindles. The motor is inside the spindle, with the rotor on the shaft between the bearings and the stator in the housing. There is no belt. These come to us as spindle jobs with a motor inside, and the motor roughly doubles the work.

Not sure which you have? Call. A model number or a photo is usually enough to tell.

How we tell a motor problem from a spindle problem

Failure analysis is like reading DNA. The cause shows in the bearings, the tool holder, the tool, and whatever is inside the spindle. A seized bearing, a crash, or coolant in the grease is a spindle problem. Burned windings, a failed thermostat, or a bad encoder is a motor problem. Often it is both, because a bearing that runs hot cooks the windings next to it, or vice versa.

That is why every integral motor spindle gets both the mechanical inspection and the electrical checks before we quote.

Motor testing

Every spindle with a motor in it gets:

  • Motor testing, before disassembly and again at assembly
  • Encoder testing
  • Proximity switch testing
  • Thermostat and lead checks

These are items 11 to 13 on our inspection checklist. The results go into the quote, so you know whether you are paying for bearings, a rewind, or both.

Rewinding

We do not rewind stators in our shop. Rewinding is a specialized trade of its own. It takes exact coil counts, the right wire gauge, and insulation or encapsulation chosen for each motor.

We send windings to a specialist rewind partner we have worked with for years, and we identify the motor make before choosing the shop. Some motors, Fanuc among them, are built with epoxy-encapsulated windings. A Fanuc that arrives without encapsulation has been rewound before, and that changes where it goes. Getting this right the first time is the difference between a spindle that ships running and one that comes back. When a rewind is part of the job, it is in the quote before you approve anything.

What makes an integral motor spindle twice the work

The coolant jacket. Drive your car at seventy miles an hour, park it, and touch the motor. A spindle motor in the cut runs that hot. So the stator housing has a coolant jacket, ports that circulate chilled coolant around the motor like a radiator. Those ports corrode. We clean the porting, replace the jacket O-rings, and then test the coolant flow and the seal.

The pressure test. We block one coolant port and fit the other with a gauge. We apply 15 PSI of air pressure and shut the valve. Then we watch the pressure gauge for an hour. If it loses no pressure, the jacket is sealed. If it loses any pressure, it is not. We find out why and repair the issue before the spindle goes back together.

The electrical side. Thermostats, leads, encoder, proximity switches, and the motor test, all repeated at assembly.

A plain belt-driven spindle has none of this. That is why integral motor spindles cost more than belt or gear driven, and why the quote spells out where the time goes.

Before you ship a motor or an integral motor spindle

  • Tell us the motor make if you know it. It decides how we handle a rewind.
  • Tell us what happened: smoke, a burnt smell, an alarm, a noise, when it started.
  • Send every rotating part: couplings, pulleys, the drawbar, and actuator parts.
  • Send a good tool holder with its retention knob for an integral motor milling spindle.
  • Fill out the repair request form and send it with the unit.

Ship to 5572 Buckingham Drive, Huntington Beach, CA 92649. Disassembly, inspection, motor testing and the quote are free until you approve the work with a purchase order.

Questions shops ask

Do you rewind spindle motors in-house?

No. Rewinding goes to a specialist rewind partner we have worked with for years. We handle everything else: testing, disassembly, bearings, the coolant jacket, assembly, run, test and balance.

Why does an integral motor spindle cost more to rebuild?

The motor roughly doubles the labor. On top of the full mechanical rebuild there is coolant jacket cleaning and O-ring replacement. Then a pressure test held for an hour, and the electrical checks.

Can you rebuild a Fanuc spindle motor?

Yes. Fanuc and Mitsubishi drive motors are common jobs. Tell us the manufacturer up front so a rewind is handled properly.

Call (714) 379-6505 and talk to a spindle expert. Or send the repair request form.

Talk to a Spindle Expert

Start with a phone call

Ed Zitney, President, MZI Precision Edward Zitney President (714) 475-4016 He has spent more than 44 years in spindle rebuilding and remanufacturing. He learned the trade over more than two decades at Precision Balancing & Analyzing, the shop long regarded in the industry as the standard for spindle work, later oversaw SKF Machine Tool Services, held service leadership roles at Setco, and wrote a published column on spindle remanufacturing for Fabricating & Metalworking.
Marco Guerrero, Partner, MZI Precision Marco Guerrero Partner (949) 374-0060 He came up on the shop side of this industry. He started with his hands, welding and fabricating for the racing industry, then spent fifteen years as general manager growing a machining job shop, the same kind of shop that sends MZI spindles today. He has sold CNC machines too, so he knows what new equipment costs and when a rebuild is the smarter call. Today he and Ed are partners in MZI Precision, and his standard is simple: every customer feels informed and supported from the first call to the day the spindle ships back.

Call (714) 379-6505 and describe what changed. With a little information about your spindle we can diagnose the problem and determine your best action.

What to expect on the call:

  • You talk directly with a spindle expert.
  • Some problems can be diagnosed over the phone, and a few do not require removing the spindle at all.
  • If your spindle should come in: disassembly, inspection, failure analysis, and a line-item quote, at no charge until your purchase order approves the rebuild.
Call (714) 379-6505 Request a Repair