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Machine brand
Siemens Spindle Motor Repair and Service
We repair Siemens spindle motors and the mechanical spindle assemblies they are built into, from 1PH asynchronous motors to 1FE built-in motor kits. CNC Spindle Service is an independent workshop in Sankt Augustin, Germany, with no Siemens authorisation. Send the motor or the complete spindle to the workshop, or ask about on-site diagnosis, possible abroad only by prior technical arrangement. A written quotation comes after inspection.
Scope
Siemens spindle systems we work on
Siemens does not build machine tools. It supplies the motors, drives, encoders and controls that other builders fit, so a Siemens spindle is a component inside somebody else's machine. Our side of that is mechanical and electromechanical: the spindle assembly and the motor, including windings, bearings and the encoder mounting. Sinamics drive electronics and Sinumerik control hardware we diagnose and report on. We do not manufacture or resell them.
1PH asynchronous spindle motors
The separate motor arrangement: the motor sits behind the spindle and drives through a belt or a coupling, with its own bearings and its own encoder. Bearings, the encoder mount and the winding insulation are checked as a set, because a fault in one of them usually shows up as a symptom of another.
1FE built-in motor spindles
Supplied as a rotor and stator kit that the machine builder fits into the spindle housing, so the motor and the mechanics cannot be separated in service. A winding fault, a bearing fault and a cooling problem all present the same way from outside. These units are stripped completely and measured before anything is judged.
Water-cooled motor spindles
Most higher-power built-in motors run a cooling jacket around the stator. Blocked or furred channels raise the winding temperature slowly, and the first visible sign is thermal growth at the tool rather than an alarm. The jacket is flushed, pressure-tested and the temperature sensors are checked during rebuild.
Servo-driven live tool heads
Turning centres often use a Siemens servo motor to drive the powered tool holders in the turret. These heads are small, run hard and are usually neglected until they seize. We strip the head, replace bearings and seals, and check the motor and its feedback before it goes back.
The exact configuration depends on the machine model and the year of manufacture. Two machines with the same model designation can carry different spindle units, so we confirm the build from your nameplate photograph before quoting.
Symptoms
Faults we see most often on Siemens spindles
Noise and rising vibration
On a built-in motor the rotor is part of the rotating assembly, so imbalance and bearing wear read the same on a meter. The assembly is stripped and balanced to an ISO 21940 grade for its speed.
Overheating and thermal drift
Winding temperature and bearing temperature are logged separately by the drive, which helps. Insulation resistance, the cooling circuit and the sensor wiring are all checked before a winding is declared faulty.
Runout at the taper
The taper belongs to the machine builder's spindle, not to Siemens, but it is still ours to correct. It is reground and runout measured against the shaft; a bent shaft is reported before further spend.
Tool clamping problems
The clamping set is builder-specific hardware running through a Siemens-motored spindle. Belleville stack, gripper and release piston are measured, and pull force is recorded after reassembly rather than assumed.
Encoder and orientation faults
Orientation faults on Sinumerik machines are often a feedback problem, not a mechanical one. The encoder, its mounting and its cable are checked; if the fault sits in the drive, we report it as a drive fault.
Coolant or grease ingress
Coolant that reaches a built-in stator does more damage than it would in a separate motor, because the winding is potted into the housing. Seals, the rotary union and the drain path are examined at teardown.
Process
What a repair looks like
The spindle is logged in and inspected on arrival, then dismantled completely. We measure shaft and housing geometry, check the bearing seats, inspect windings and encoder, and photograph what we find. You receive a written quotation with the scope of work before anything is repaired. After the work is done the unit is dynamically balanced, run-in tested and shipped with a test report containing the measured values.
The individual operations — bearing replacement, rotor and stator rewinding, taper regrinding, drawbar and clamping repair, encoder work, seal and cooling circuit overhaul — are described on the services section of our homepage. On a Siemens spindle they are usually combined into one rebuild rather than ordered separately.
What to send with your enquiry
- Photographs of the spindle nameplate and of the tool interface
- Machine model, spindle type and year of manufacture
- A short description of the symptoms and when they appear
- Any measurements you already have — runout, temperature, vibration, current draw
- Whether the machine is still assembled or the spindle is already removed
Removal should be carried out by qualified personnel following the machine documentation. If that is not possible on site, ask us about removal and refitting as part of an on-site visit.
Shipping and on-site service
Our workshop is in Germany and we have no branch, warehouse or permanent staff in other countries. Customers outside Germany send the spindle to us by freight forwarder; we inspect, repair, test and return it. On-site work — removal, installation, alignment and commissioning — is possible internationally, but only after the job has been agreed technically in advance, so that the right parts and instruments travel with the technician.
Questions
Siemens spindle repair — frequently asked
Yes. We are an independent workshop, so a motor or a complete spindle can be sent to us directly, with no dealer in between and no tie to one parts catalogue. What we cannot claim is any form of Siemens authorisation or partnership. We have none. We repair the hardware; we do not represent the manufacturer.
Siemens does not build machine tools, so the motors reach us inside other builders' machines. In practice that means European machining centres and turning centres with Sinumerik controls, from builders such as DMG Mori, Hermle, Grob and Index. We work from the motor plate and the spindle drawing rather than from the machine badge.
No. We diagnose them. If the symptom points at the drive, the control or the parameter set rather than at the spindle, we say so and describe what we measured, so your electrician or your control supplier has something to work from. Repairing, manufacturing or reselling that electronics is outside what this workshop does.
Typically 5 to 10 working days from arrival, depending on parts availability and what the teardown reveals. That is an estimate, not a committed date; a binding date is only valid if confirmed in writing. A rewind, or a built-in stator that has to be replaced, usually pushes the job beyond that.
The motor or spindle is stripped, measured and electrically tested, and you receive a written quotation before repair work begins. The inspection is chargeable and we tell you that charge before you ship. If the quotation is declined, the unit goes back to you; carriage is yours in both directions.
Send us the spindle details
Tell us the machine model, the spindle type and what the machine is doing wrong. We come back with an initial assessment and a written quote before any work begins.