Machine part image for slideshow

Servo Motor Repair FAQ’s

Fanuc Servo Motor Repair Part Inventory2016-12-21T06:40:46+00:00

Fanuc Servo Motor Repair Part Inventory

Repair Part InventoryFanuc is the largest manufacturer of automated machinery in the world. Yet, a majority of the replacement parts needed to maintain Fanuc motors and machines have 16-20 week delivery times, if they are available at all. Ultimately Fanuc limits what “end users” can and can’t do to their machines. Servotech knows that our customers can’t wait 16 weeks for a part, and can’t have a machine down for 16 weeks. We also know it’s impractical for our customers to stock every part they may need, just in case the motor breaks.

Since Fanuc has limited part availability, Servotech has made it our policy to stock as many Fanuc servo motor components as we can. By inventorying more parts, different parts and higher quantities of all parts we eliminate the 16-week delivery time. From spindle motors fans to sensors, we have a healthy supply of the most commonly used components that are vital to Fanuc servo motor and Fanuc spindle motor repairs.

Even though we stock a large quantity of parts, there is the challenge of obtaining servo motor parts that completely unavailable. We came to a point where we either had to give up or get creative. We chose creative ingenuity. We now stamp our own Fanuc Fanuc Partsgaskets for back caps and conduit box covers. Through the use of additive manufacturing (3-D printing) we can recreate or replace small or easily broken plastic components right in house. In the case of some spindle motors we have even re-designed the motors with hybrid bearings.

It is because of these measures that Servotech is able to offer a reliable, rapid response option for Fanuc servo motor repairs, as well as a multitude of other manufacturers whose parts are un-obtainable. Our parts are as good as, or even better than, the original Fanuc components, and our response time for repairs leads the servo motor industry. Ultimately we work hard every day to keep our shelves stocked with parts, so you can keep making parts.


Maintenance & DC Servo Motor Repair – Undercutting2016-12-21T06:45:03+00:00

Maintenance & DC Servo Motor Repair – Undercutting

Undercut Your Motors, Not Your Success

Did you know that changing the brushes in your DC servo motor may fix some of your issues and keep you running in a pinch? Did you also know that a brush change is only a temporary fix?

DC Servo Motor Repair - UndercuttingIt stands to reason that as brushes wear out. The carbon they are comprised of turns to dust, which only has one place to end up – inside your servo motor! Changing the brushes is a good maintenance step, but it is also an admission that at least one set of brushes worth of carbon is now caked on the inside of the motor.

Furthermore, as brushes wear down, so does the copper motor commutator. Over time a commutator can develop a ridge or grove where brushes have been riding, causing brushes to wear out more quickly or not make proper contact, which leads to higher current draw.

When brushes wear improperly the excessive carbon can get lodged in between the commutator bars and cause a short circuit. The only way to make a DC motor last indefinitely is to rebuild it.

DC Servo Motor Refurbishment – Done Right by Servotech

At Servotech we remove the motor armature and put it through a process known as “Undercutting.” A small toothed blade is actually used to clean out the grooves in between commutator bars, then the armature is put in the lathe and all of the bars are turned down to one smooth surface. Once the bars are smooth, consistent and clean, the motor can be rebuilt, and the brushes can be set properly so that they will run true, and last.

For more information, read about our DC Motor Repair Process or see our article about DC Servo Motor Brush Wear.

Find Authorized Servo Motor Repair2016-12-21T07:02:01+00:00

Find Authorized Servo Motor Repair

Servo motor repair is a specialized challenging field. Servo repair techniques and procedures are often the result of companies who have researched through trial and experience. Servo motor manufacturers like to model their business after the automotive industry; constantly pushing new products lines, innovating year after year, and encouraging the sales of newer, faster and more precise machines.

A lot of companies out there throw around terms like, “Qualified Servo Motor Repair Center”, or “Official Servo Motor Authority”. It is a strategy in search engine optimization to favor certain words and phrases. There is no harm in turning a phrase, except when it is deliberately misleading.

The questions is: “How can you determine if a repair shop is a legitimate authorized servo motor repair center? Is it possible to confirm affiliation with a servo motor manufacturer?” When it comes to servo repair, the shortest response is usually – no they are not authorized, and they are not affiliated!

3rd Party Servo Motor Repair Shops Are Rare

Most manufacturers of CNC machines, and by association servo motors, are not interested in having third party shops repair their equipment. Companies like Fanuc and Mitsubishi do offer repair but at prices that promote buying new servo motors and machines. Because large manufacturers do not find it cost effective to repair their equipment, they just don’t. Additionally, they have no interest in certifying other companies as authorized servo motor repair facilities.

Authorized Servo Motor Repair Claims

Beware the use of servo motor factory logos on websites. It doesn’t take a lot of effort to copy and paste an image of a logo and incorporate it into a website. This can lead consumers to misconstrue a false connection between the motor manufacturer logo and the servo motor repair company. Never assume that a logo is the equivalent of a factory certification.

Some companies use phrases like “Master Servo Motor Repair Center,” and “Primary Servo Motor Repair Center,” to make an implication that there is some connection between the servo repair shop and the servo motor manufacturers they repair. Using language to mislead a customer into choosing a service on false pretenses is dishonest.

Perspective can be difficult to maintain, especially with a machine down, and the need for quick action.

Truly Authorized Servo Motor Repair

Servo motor repair, like any other industry, has its leaders who thrive on the quality of their honest work. At Servotech is has always been our mission to exceed customer expectations and servo motor manufacturer standards. Many of our servo repair processes result in a servo motor that is better than a brand new one from the manufacturer.

During our years in business, we have earned the distinction of being an actual authorized servo motor repair center for some of the world’s biggest servo motor manufacturers. We maintain factory drives, rigorous procedures and the very best servo motor repair procedures to maintain these certifications. Find our more on our:

Stop Overpaying for an OEM Servo Motor!2016-12-31T06:57:56+00:00

 Stop Overpaying for an OEM Servo Motor!Servo Motor Repair

You May Be Paying Too Much for Your OEM Servo Motor

Are you buying your servo motors from your machine manufacturer? You may be paying way too much money! Have you called the servo motor manufacturer and been told “we cannot sell you this motor, call your OEM”? Before you give up hope, there is a strong possibility you can obtain a replacement motor for much less!

How to Configure an OEM Servo Motor Replacement

  • Find the OEM servo motor part number breakdown (frequently found on series datasheet).
  • Find your servo motor part number.
  • Break down your part number to see what’s been changed from the base model.
    • If the change corresponds to a seal, connector, etc. Order the base model servo motor and buy the seal or connector separately.
    • If it’s something else or if you can’t find the change, call 1-888-80SERVO.

Details on OEM Servo Motors

Most OEM servo motors have had modifications made to them specific to their application. These modifications can range from something as simple as connector pin assignments, to something as involved as installing special feedback in the servo. In order to determine the modifications made to the motor there are a few pieces of information you need.

Try to obtain a datasheet or brochure that matches your specific servo motor series from the motor manufacturer. This will very often give you a description of how to break down the servo motor part number – showing how the part number identifies specific properties of your servo. Now you will need the part number off of your motor. Break down your part number using the same format, and see what is different. You will usually find a letter or number in your part number that is not listed as an option in the datasheet – this will correspond with what is different about your servo.

If the change in the part number corresponds to something like a connector or seal that is the most simple option. You can order a servo motor with the closest matching part number and buy the seal or connector separately, directly from the servo manufacturer. Remove the stock seal, connector, etc. and install the unique one – and you just saved a lot of money!

Sometimes the part number will have extra characters at the end, or unique sections that will correspond to something complicated – such as motor torque or shaft dimensions. Look through the manufacturer datasheet and compare all of you servo motor’s physical and electrical specifications to the stock servo, and you should find the modification.

Hopefully you find what makes your OEM servo motor unique, and you can eliminate the high costs and long lead times, and simply buy your servo motor straight from the manufacturer.

If you need assistance in locating a direct replacement for your OEM servo motor, our technicians are here to help! If a replacement does not exist we are your best source for refurbishing your servo motors to new condition – so you can avoid overpaying for an OEM servo motor!

Contact us for more information on buying a servo motor or for servo motor repairs.

Servo Motor Resolver Wiring: Colors & Functions2016-12-21T13:49:21+00:00

Servo Motor Resolver Wiring: Colors & Functions

If you ever plan to replace or test a resolver then you need to know the functions of each wire. This can be very difficult to determine with out a little knowledge and a voltmeter.

There is an industry standard for resolver wire colors that most manufacturers choose to use. These colors are as follows:

Resolver Wire Colors
Wire ColorRed/WhiteBlack/WhiteRedBlackYellowBlue
Wire FunctionExcitation +Excitation –Cos +Cos –Sin +Sin –


Proprietary Wire Colors

Sometimes Yellow/White can be used in the place of Black/White for Excitation. These are industry standard wire colors but you will come across other brands of resolvers with their own proprietary color designations. When this happens you will need to use a voltmeter to assist you in determining wire color versus function.

Determining Circuits

Almost all resolvers have 6 leads. Use a voltmeter to ring out the leads and determine which 3 pairs of wire are circuits. Then record the resistance of each circuit. The Cos and Sin circuit will have the same resistance, so the circuit with the different resistance will be your excitation circuit. If any circuits ring open, or all three circuits have different resistances then your resolver could have a damaged winding and need to be replaced/rebuilt.

These are some basic tips on how to determine a resolvers wiring. In order to continue on and designate exact wire functions on nonstandard wire colors you will need to excite the windings with the proper frequency and use an oscilloscope.

Further Questions

How Can I Excite the Windings?

Before you can determine exact functions of your resolver wires you will need background information concerning the type of output your motor drive or controller is looking for. Most manuals will describe the specific sin and cos outputs used based on the direction rotation. You need this information to proceed.

In order to test your resolver you will need to excite your resolver with the proper voltage and frequency which is typically written on the resolver label. Most resolvers are between 4-6V at 3-10KHz. People who don’t have test equipment that can feed high frequency hook their resolvers to their drive and check the sin and cos outputs either on the drives test points or directly off of the resolver.

Once you have the resolver running on the scope you just need to set up the outputs of the resolver to match the drive/controllers specifications paying attention to the direction of rotation.

Here are some links with some more information on resolver windings:

Does the Mechanical Position of a Resolver Matter When Fitting to a Servo Motor?

The angular position of the resolver stator to the resolver rotor is critical. Most resolver stators are mounted in a way that they can be rotated 360 degrees easily in relation to the motor housing with no alignment pin or key. When the resolver stator or rotor is rotated independent of the other, however, the electrical angle of the resolver relative to the servo motor will change and you will lose your proper alignment.

You can rotate the entire resolver as a unit to any physical position relative to the motor. Many resolver manufacturers mark a line from the rotor to the stator to designate 0 degrees. As long as the lines line up you can put the resolver in any position you like and know your resolver is at 0 electrical degrees.

How Can I Determine Rotor to Resolver Position for Correct Commutation Signals to the Servo Drive?

Your best bet is to find documentation on the drive. There is no way to determine the correct alignment with just the motor. The alignment is whatever the drive needs it to be, which varies drive to drive.

Another way to determine the correct alignment is by examining a sister motor. You will need to use your controller or other equipment to determine the angle of the resolver as there is no zero degree mark.

Servo Motor Connectors: Where Can I Find Them?2016-12-21T13:51:40+00:00

Servo Motor Connectors: Where Can I Find Them?

Your servo motor needs a new connector. The connector is cracked and the pins are all bent. You look at it and think, “Where am I ever going to find this plug?” And even if you find the plug and get it on time, can it be changed easily? Connectors can quickly become a headache. With so many styles, manufacturers, and specific needs there are millions of plugs in production to choose from. Finding your connector can be extremely difficult if you do not know how to search.

Once You Have Found Your Servo Motor Connector…

  • Do you have the tooling you need to install it correctly?
  • Do you have the information recorded when you disconnect the old servo motor connector to connect the new one?

Refine the Search

The first step to finding your servo motor connector is refining your search. This will limit the number if connectors to search through by specific characteristics. Many online companies that sell connectors will let you limit your search by choosing variables such as rated current, shape, number of pins, etc.

If you know the manufacturer of you your servo motor connector (give it a good look over) then you can limit your search or go straight to that manufacturers online site.

If you can obtain a manufacturers part number, many online sites will cross it to their own part number. If at all possible, get a datasheet and verify dimensions before purchasing, you don’t want a close match, you want an exact match.

Collect the Tools You Need

There are some tools that are necessary to install connectors on your servo motor. You will need a soldering iron to solder the pins and sockets. Even if they are crimp pins, many people will solder the crimp to strengthen the joint and prevent fraying.

If the pins need to be crimped invest in a crimper for that style connector. Many connectors are threaded together and you will need wrenches and pliers.

Document Servo Motor Connector Wiring

Always document the servo motor connector wiring before removing the old one. Write down wire colors relative to pin numbers. If possible also document wire functions to pin number as colors are not always easy to differentiate.

Most people forget to document the orientation of the connector in relation to the motor, and also the orientation of the connector hub to the housing of the connector. If these are not correct you may not realize it until you motor is reinstalled into your machine and now the cable does not reach or mate with your motor.

In Summary

These are some considerations to make when changing your connectors on your servo motor. There are many good places to shop for servo motor connectors, and prices can fluctuate greatly, so shop around. If you are having someone else change your connectors make sure they are replacing you old connector with a proper match. Many repair facilities will use unsealed or lower quality replacement servo motor connectors resulting in more problems down the road for you.

Servotech has technicians who spend their day dealing with servo motor connectors, plugs, and manufacturing cables. If you do not have the time or desire to find your connector or build your own cable, we will gladly do it for you!

Contact us for servo motor repair.

How do I disassemble/rebuild my DC servo motor?2018-09-22T12:59:57+00:00

So you think you’ve got what it takes to rebuild your broken DC servo motor. Just a rotor with a couple bearings right? Wrong. There are many factors to consider before disassembling your own DC servo motor.

Substandard insulation, exposed copperElectricity will go to ground
Scratched insulationCorrosion of affection area
Improper winding configurationCommutator worn out, repair or replacement necessary
Nicked or damaged wires in windingsMalfunctioning or burned up motor
Armature removed from wrong type of field frameLoss of magnet strength, demagnetization, servo failure
Damage to tachometer armatures or windingsReplacements necessary
Poor field frame positioning relative to brush riggingTorque loss, over current, motor failure

You Must Be Able to:

Test the Armature Insulation Correctly

There are special testers used to test the insulation that protects the winding from grounding out to the iron on the armature. It is very important that the insulation be up to standard. When the motor is being run under load there is potential for electricity to go to ground.

If there is any exposed copper on the winding this would be a high potential for grounding out during operation. Any area were the insulation is scratched will have a high potential to corrode over time and fail.

Test the Armature Circuit Correctly

There is also special testing equipment to test each circuit of the armature insuring that the windings are going to work to specification. Special attention needs to be paid to the commutator. If the commutator is worn or burned it will need to be turned in a lathe or replaced.

Avoid Damage to the Electrical Windings as You Separate the Armature from the Field Frame

Removing the armature is a delicate process, which is compounded by the magnetic force of the field frame. The exposed wires, and commutator are extremely prone to getting nicked or damaged during the disassembly process. Even minor physical damage to the circuit of the armature can cause a motor to malfunction and burn up.

Separate the Armature from Its Magnetic Field without Causing Demagnetization

There are many types of magnets. The most popular types used in servo motors are Neodymium Iron Boron (NdFeB or NIB), Samarium Cobalt (SmCo), Alnico, Ceramic, Ferrite and Rare Earth. Certain magnet types require that their fields not be broken. If a motor or tachometer armature is removed from the wrong type of field frame, the magnets will loose their strength effectively ruining the servo. The only way to rectify demagnetized field frames on a disassembled servo motor is to recharge the magnets. Otherwise the servo will never run properly.

Avoid Damage to the Tachometer Armature as you Remove It from the Motor Armature

Often, as you try to take the Tachometer off of the motor shaft it can be very hard to remove because of corrosion and tight tolerances. We have made several special removal tools to take the tachometer armatures off to prevent destroying them. The windings on a tachometer armature are smaller than the hairs on your head, and much less resilient to forces applied to them.

Assemble the Field Frame on the Brush Rigging Correctly

The relative position of the field frame to the brush rigging needs to be correct. If this relationship is not correct the motor will not commutate correctly resulting in torque loss, over current, and motor failure.

In Summary

These are a few of the important things to know before you start to take apart your own DC servo motor. If you decided that you want your motor professionally repaired then send it to Servotech Inc. We have all the necessary knowledge and equipment to rebuild you DC servo motor.

How do I disassemble/rebuild my DC servo motor?

Keep Coolant and Oil Out

Replace Shaft Seal When the Motor Is Worked on

Routine maintenance? Replace the seal. Changing bearings? Replace the seal. It is common for maintenance personal to reuse old seals versus replacing with new ones due to time constraints, budget, or laziness.

Even Environmentally Sealed Plugs Leak over Time

Replace worn plugs especially if there are loose pins that liquid could get around.

Servo Motor Connectors Need to be Mated

Even sealed connectors need to be mated with matching sealed cable connectors to ensure proper protection. Unsealed cable connectors will allow contaminants into gap between motor and cable connectors. As no seal is perfect, this unnecessary exposure to the plug surface will lessen the time it takes for contaminants to infiltrate the connector.

Stacked Laminations Allow Liquid to Leak through

AC servo motors have a stator that is made up of stacked laminations which will allow liquid to slowly leak through them. Some brands, such as Yaskawa, put a thin metal case around the stator to prevent liquid intrusion. Many other manufacturers such as Fanuc do not and just paint over the laminations. We have found that sealing the laminations with a two part epoxy paint significantly reduces the chance of contamination through the laminations.

Avoid Direct Spray on Servo by Oil or Coolant

Make sure that your servo is not being directly sprayed by oil or coolant. If it is not possible, there are many custom solutions out there to modify the motor or cabling to limit exposure.

In Summary

These are some general tips on preventing liquid intrusion into your servo motor. If your servo motor is flooded and you need help send it in to us and we will repair your servo and work with you to find a way to prevent flooding in the future.

Servo Motor Torque Loss2016-12-21T13:55:03+00:00

Servo Motor Torque Loss

Your servo motor does not have the power it once had. You are starting to encounter current and torque alarms on your machine. You check the couplings, bearings, maybe even swap drives. Nothing seems wrong and the problem is probably in the motor.

Your Servo Motor Has Lost Torque – Now What?

There are several reasons that your servo could be losing power. Figuring out what is wrong with your motor will determine how difficult it is to fix, and who is even capable of fixing it.

Does Your Servo Motor Have a Brake?

If there is a brake in your motor then you need to check the voltage going to the brake. Most motors will have the brake voltage written on the label.

If the brake is not opened when the motor runs, then you will lose significant torque and also destroy the brake. This is a common problem and is often caused by faulty relays in the cabinet.

Are Your Servos Magnets Demagnetized?

This can be determined by checking the BEMF of the servo, which will probably require you to send the motor out to be evaluated. If the servo is demagnetized then you will need to find a company that can re-magnetize your servos’ magnets.

Has Your Servo Ever Been Disassembled?

If the encoder has been removed and reinstalled the alignment might be off. A bad alignment can cause you servo to run, but run poorly drawing high current. If this is your problem then you need to have your servo serviced and realigned.

In Summary

Torque loss is a common servo motor problem. The root cause needs to be determined so that you can be sure you are fixing the right problem. If you find you have to send your servo out for repair, it is best to make sure they have the equipment to do the job.

If you don’t know what to do or where to have your servo repaired, Servotech has the equipment and knowledge to restore your servo motors torque to its original factory specifications. Contact us for a fast repair quote, or to discuss your servo motor unit’s torque loss.

Servo Motor Resolver Overspeed2016-12-21T13:56:19+00:00

Your servo drive pops an error code. You write down the error code and look it up in the manual – it corresponds to a “resolver overspeed” alarm. Next to that is written “check the feedback cables” as a probable solution. You replace the cable and get the same alarm.

Servo Motor Resolver Overspeed

How to Identify the Source of a Servo Motor Resolver

Overspeed Error

A servo motor resolver overspeed error is a very common alarm, and can have many causes. Many of these error or alarm causes are easy to fix. With a process of elimination you often can determine what part of your system needs repair.

Are Your Cables Properly Shielded?

Your cables should have an internal shield that is properly grounded. Shields are usually grounded directly to the inside of a cabinet. Resolver based systems are very sensitive to noise and can be prone to alarms if not properly shielded.

Has Your Servo Motor Been Disassembled?

Have you had your servo motor rebuilt, or tried to rebuilt it yourself? If so, was the resolver properly aligned to the motor? If for any reason your resolver has changed its position in relation to your servo motor your system will not run. A misaligned resolver can cause many alarms, including resolver overspeed.

Has Your Servo Resolver Wiring Been Changed?

If you have swapped drives or changed cables then your wires could have been connected incorrectly. Swapping resolver wires can cause the resolver to swap direction, change to location of the zero position, or not function at all. Miswired resolvers can cause overspeed alarms.

In Summary

These are some tips to remove a coupling from the shaft while minimizing possible damage to your servomotor.

Tips on Using Slings to Remove and Install Your Heavy Servo or Spindle Motor2016-12-23T15:22:19+00:00

Tips on Using Slings to Remove and Install Your Heavy Servo or Spindle Motor

The Problem

Your motor has failed and you need to remove it from your machine. You have disconnected all the electrical, disconnected the coupling, cursed the engineer who designed the machine, and are now ready to remove the motor. There is just one obstacle left however, the motor weighs way more than you can lift by hand.

The Solution

You decide to use a forklift or ceiling crane to lift the motor out of the machine. You see that the motor has one or two eye-bolts that you can attach slings to. Just connect the motor to the crane and lift right? Almost, but there are a few things you must do to insure your personal safety and the safety of the motor.

Using a Sling

Slings Are Specifically Rated for Certain Loads

These loads vary depending on the manner in which you utilize the sling. These loads should be documented on the sling label. If the label is missing or you are using a sub-par sling you should consider throwing it away and investing in proper slings.

Learn the Right and Wrong Ways to Attach a Sling

Wear-flex has a web page on the proper use of their slings. Knowing when a sling is being used improperly will reduce the likelihood of undue strain leading to sling failure.

Always Use One Sling per Eye-bolt

Never loop the sling through two eye-bolts. This mistake is common. When the sling loops from one eye-bolt to another it puts force on the bolts at an improper angle that can lead to them bending or breaking. Always lift an eye-bolt straight up from the top of the bolt, and check that the bolt is tight before lifting.

These are some tips on safely lifting your motor out of your machine and putting it back in.

What to Consider When Your Motor Has a Bad Bearing Fit2016-12-21T13:59:26+00:00

What to Consider When Your Motor Has a Bad Bearing Fit

Servo Sounds Created by Bad Bearing Fit

Hearing servo sounds like knocking, or your servo motor has a strong vibration? You send it somewhere for repair and you are told that the bearing fit is no good. You get a quote to change the bearings and repair the bearing fit. Problem solved you say…. Then your servo is returned and fails again. What is so difficult about fixing a bearing fit?

Why Is the Bearing Fit Failing?

Failure of a bearing fit is a common problem with all electric motors. Bearing fits fail when the fit is not the correct bore, the bearing was incorrectly installed, or the bearing seized. If a bearing fit fails this can lead to many other problems with your servo motor.

Feedback Devices Are Damaged Easily by Oscillation

Feedback devices are very sensitive. Encoders often have glass scales that shatter and resolvers have windings that are damaged when their axis of rotation is not perfectly central.

Rotor Shafts Can Bend or Break

Servos need to run true and broken shafts can occur under the armature where they are often missed until the motor is under load in your machine.

Damaged Stator Laminations Ground Power Leads

The air gap between rotor and stator is small, so when there is an oscillation in the rotor it will bang into the stator laminations. Bending the laminations can cause high spots that rub and also cause the lamination to pinch the coil under it shorting the motor windings to ground.

Who Can Repair the Bearing Fit Once and for All?

When your servo motor has a failed bearing fit be cautious where you have it repaired. Regular motor shops will not be capable of evaluating or repairing the feedback on your servo. Most places will see a failed fit and look no further. Being aware of the side effects of a bad fit will improve the likelihood that your servo gets properly repaired the first time.

Servotech has the tools and knowledge to solve this problem. Call 1-866-80SERVO to discuss your issue with us.

Minimizing Noise on Your Servo Motor System2019-08-04T14:05:31+00:00

Your servo suffers from intermittent failure, feedback loss, runs choppy, or trips out on some sort of encoder error. Could electrical noise be the culprit?


Minimizing Noise on Your Servo Motor System

Reducing Electrical Noise in Your
Servo Motor

Electrical noise is present in every electrical system. It can disrupt the feedback signals (especially with resolvers) on the motor and cause the drive to misread information and not perform as instructed. Noise is a little thought, high impact problem that is relatively easy to minimize.

Cable Selection Is Crucial

Try to buy cable with the correct number of wires. Use twisted pairs for the send and return of each circuit if possible. Keep your cables as short as possible, and do not just coil up the extra cable and leave it in a cabinet.

Always Use Shielded Cabling

Just having a shield inside the cable is not enough; it needs to be properly grounded at either the motor or the drive but not both. Shielded cabling can actually make your problem worse if you do not have a solid ground.

Keep Feedback Cables from Looping around or Running Closely Parallel to High Voltage Cables

Maximizing distance between communication and high voltage cabling will minimize the impact of noise on your system.

In Summary

Servo motors, drives and encoders are often misdiagnosed as bad when they are really just being affected by noise. Minimizing noise will save you downtime and unnecessary repair costs.

Oil and Coolant, A Killer of Servomotors2016-12-21T14:01:54+00:00

Oil and Coolant, A Killer of Servomotors

Coolant and Oil in Your Motor

Your machine is down and you pull out a faulty servomotor and send it out for repair. The diagnosis is quick, there is coolant or oil in your motor and it needs to be rebuilt. Your motor had a seal on the shaft, sealed plugs, and gaskets between all of the exposed parts. How did your servo motor fill with oil?

There are a number of common routes liquids can take to get into your motor. You need to know these routes in order to prevent liquid intrusion from happening again.

Keep Coolant and Oil Out

Replace Shaft Seal When the Motor Is Worked on

Routine maintenance? Replace the seal. Changing bearings? Replace the seal. It is common for maintenance personal to reuse old seals versus replacing with new ones due to time constraints, budget, or laziness.

Even Environmentally Sealed Plugs Leak over Time

Replace worn plugs especially if there are loose pins that liquid could get around.

Servo Motor Connectors Need to be Mated

Even sealed connectors need to be mated with matching sealed cable connectors to ensure proper protection. Unsealed cable connectors will allow contaminants into gap between motor and cable connectors. As no seal is perfect, this unnecessary exposure to the plug surface will lessen the time it takes for contaminants to infiltrate the connector.

Stacked Laminations Allow Liquid to Leak through

AC servo motors have a stator that is made up of stacked laminations which will allow liquid to slowly leak through them. Some brands, such as Yaskawa, put a thin metal case around the stator to prevent liquid intrusion. Many other manufacturers such as Fanuc do not and just paint over the laminations. We have found that sealing the laminations with a two part epoxy paint significantly reduces the chance of contamination through the laminations.

Avoid Direct Spray on Servo by Oil or Coolant

Make sure that your servo is not being directly sprayed by oil or coolant. If it is not possible, there are many custom solutions out there to modify the motor or cabling to limit exposure.

In Summary

These are some general tips on preventing liquid intrusion into your servo motor. If your servo motor is flooded and you need help send it in to us and we will repair your servo and work with you to find a way to prevent flooding in the future.

DC Servo Motor Brush Wear2016-12-21T14:03:15+00:00

DC Servo Motor Brush Wear

DC servo motors very often come in for repair because their brushes have worn out. This seems like a straight forward problem with an easy solution; install new brushes! And while this could be true, premature brush wear can be a sign of larger problems with your servo motor. There are a few points you can check to narrow down the cause of your premature brush wear.

Check Your Brush

Is the Head of the Brush Broken or Chipped?

If it is then your could have a high bar or piece of mica on your commutator which means you will need to clean up your comm or possibly rewind your armature.

Are There Grooves in the Brushes?

If there are thin grooves in the brush then there are probably matching thin grooves in the commutator. This problem is called threading because the grooves resemble the threads of a bolt. This could be an indicator that you have the wrong type of brushes installed or are running the motor with too light a load. This is a common problem with long life brushes.

Does the Brush Show Signs of Burning or Arcing?

If the servo motor’s electrical neutral is not properly set then there will be voltage potential between the brush and the commutator bar before the brush is contacting that bar, which will cause arcing when they get close to each other.

In Summary

Servotech uses Helwig brushes for almost all of our servo motor repairs. Knowing why your brushes are wearing will help you determine if your DC servo motor needs repair or if you can modify the brushes you use and save money and downtime.

Simple things to check before sending in your servo motor for repair2016-12-21T14:04:16+00:00

Servotech repairs thousands of servo motors a year, and occasionally we receive repair orders with simple issues that the customer likely could have addressed themselves.

We’ve complied a list of the top simple issues that should be checked before sending in your servo motor for repair. Please note this is not meant to be an insult… we very often spend time trouble shooting over the phone to eliminate simple errors or problems. Double check everything before electing to send in a motor for repair, otherwise time has been lost in both the shipping and evaluation.

1. Occam’s Razor: The simplest explanation is most often correct. Make sure everything is plugged in. Try turning your drive and controller off, and reboot.

2. Check All Servo Motor Cables. Look for items such as:

  • Broken Wiring
  • Loose Connections
  • Dirty and Corroded Connectors – bad connections can interfere with the power and signals that are vital to proper servo operation.
  • Check Overall Cable Conditions
  • Making Sure that the Correct Cable is Connected to the Correct Drive

3. Check Grounds and Shields. Just because a cable is in good shape doesn’t mean it is properly grounded. Keep in mind that:

  • Grounds and shields are important for protecting signal wires from harmful noise that can disrupt feedback communication.
  • Motor power grounds are important because they facilitate the tripping of over current protection devices.
  • If a motor has an inconsistent ground that is not continuous with a drive ground the power cable can throw an unmanageable amount of noise onto a properly shielded feedback cable.

4. Is Your Servo Still Broken? We can help trouble-shoot servo motor problems. Give us a call at 1-866-80-Servo (1-866-807-3786), or contact us through our easy online repair form, and we can help determine what type of repair your servo motor may require.

Simple things to check before sending in your servo motor for repair

Your Servo Motor Experts

Servotech is ready to assist with any servo motor repair order. We are here to help, so don’t hesitate to contact us.
Need help now? Call us at 1-866-80SERVO or visit our online form.

Fanuc Servo Motor Repair – Finding the Fanuc Motor Part Number2016-12-21T14:08:25+00:00

Fanuc Servo Motor Repair – Finding the Fanuc Motor Part Number

We get a lot of customers who call us and say, “I have a Fanuc A06B Motor, can you fix that?”

The answer is “Yes”! But did you know that ALL Fanuc servo motors, no matter what size or purpose, have a part number that starts with A06B? Fanuc part numbers are broken down into three portions: A06B denotes a servo motor, the middle section of numbers refers to the windings of the motor and its electrical performance, and the final group of letters and digits denote feedback and shaft specifications.

Take a look at these two Fanuc AC servo motors. At first glance they look like the same motor with different output shafts. If we inspect the part numbers however, the motor on the left is designated A06B-0128-B077, where as the motor on the right is an A06B-0313-B574. Not only are the shafts different, but so are all of the electrical characteristics and the encoders.

Fanuc Servo Motor Repair     Fanuc Servo Motor Repair

Part numbers are a quick reference that can unlock more information about a servo motor, however you don’t need to be an expert – that’s what we are here for! Contact us or fill out and online form noting the A06B Number. We can very easily get you pricing for repairs, availability of parts and we can figure out what kind of feedback device the motor utilizes in case you need a new one. Once we know the part number we know everything: gaskets, seals, connectors, bearings and even hardware.

Feedback Servo Motor Part Numbers

As if it wasn’t confusing enough there are also a lot of part numbers that start “A860” which stands for some form of “feedback.” Feedback refers to sensors and encoders, the integrated technology on the back of a servo motor or spindle motor that communicates with the drive or controller.

View our complete line of replacement Fanuc encoders, our servo motor parts and more on our Fanuc Servo Motor Repair Processes. If you need more help determining which Fanuc servo motor, or any motor manufacturer, you have – contact us – we’re here to help.


Servo motors repaired and delivered in five business days. 48-hr rapid turnaround available on most repairs for a 15% expediting fee.

Call 866-80SERVO (866-807-3786)

Request a servo motor repair online