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Machine brand
Heidenhain Encoder and Spindle Repair
We rebuild spindles fitted with Heidenhain encoders and sort out the feedback side that goes with them: mounting, signal quality and orientation. CNC Spindle Service is an independent workshop in Sankt Augustin, Germany, with no Heidenhain authorisation. Send the spindle in, or ask about on-site diagnosis, which is possible abroad only by prior technical arrangement. You get a written quotation before any work starts.
Scope
Heidenhain spindle systems we work on
Heidenhain builds encoders and controls, not machine tools, so its parts arrive inside other builders' spindles. The thing that matters in a rebuild is that most spindle encoders are modular: a scanning head reading a graduated drum or ring that is mounted on the shaft itself, with no bearings of its own. Signal quality is therefore a mechanical result. We repair the spindle and fit the feedback; TNC control hardware we diagnose only.
Motor spindles with incremental rotary encoders
The common arrangement: a sealed or modular rotary encoder giving sine-cosine signals for speed and position. Amplitude, offset and phase are measured on the bench, and the encoder is refitted with the gap and concentricity the mounting drawing calls for, not by feel.
Absolute encoders with EnDat feedback
Used where the control needs spindle position at switch-on, typically for tool change and for milling with a positioned spindle. These are checked as a system: the encoder, its cable, the mounting and the mechanical zero. A drifting orientation is often a loose taper on the encoder hub rather than a failed device.
Modular ring encoders on the spindle shaft
A graduated ring shrunk or clamped onto the shaft and read by a separate scanning head. There is nothing between the ring and the bearings, so runout, thermal growth and a poorly seated ring all show up as feedback noise. The ring seat is measured during the rebuild.
Spindles with dual feedback
Some TNC-controlled machines carry one encoder on the motor and a second on the spindle shaft, so the control can see what the belt or gearbox does in between. Both have to agree after a rebuild. We check the mounting of each and report any mismatch we cannot resolve mechanically.
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 Heidenhain spindles
Noise and rising vibration
Bearing wear shows in the feedback before it is audible, as rising position noise at constant speed. We read the encoder signals, then strip the spindle and measure rather than trusting one symptom.
Overheating and thermal drift
Heat moves the encoder hub as well as the shaft, so drift can look like a scaling error in the control. Bearing preload, lubrication and the encoder seat are all assessed at teardown.
Runout at the taper
Runout at the tool and runout at the encoder ring are separate measurements. The taper is reground and corrected; if the shaft is bent, that is reported before the encoder side is touched.
Tool clamping problems
A TNC will refuse a tool change if clamping and spindle position disagree, which sends people to the encoder first. The drawbar stack and pull force are measured before the feedback is blamed.
Encoder and orientation faults
The core case here. Signal amplitude, reference mark behaviour, cable and connector condition and the mounting gap are all measured; a failed encoder is replaced with a like-for-like part sourced on the open market.
Coolant or grease ingress
Encoders in the spindle rear are exposed to mist and grease creep. Contamination on the graduation gives intermittent errors that come and go with temperature; the housing sealing is examined along with the bearings.
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 Heidenhain 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
Heidenhain spindle repair — frequently asked
Yes. We are an independent workshop, so the spindle can come to us directly, with no dealer in the middle. Replacement encoders are sourced on the open market. What we cannot claim is Heidenhain authorisation, certification or partnership of any kind. We have none, and we would rather say that plainly than let it be assumed.
Heidenhain does not build machine tools, so the encoders reach us fitted inside other builders' spindles. In practice that means TNC-controlled milling machines and machining centres from European builders, along with retrofitted older machines where the encoder was changed at some point. The machine badge matters less than the encoder type and its mounting drawing.
Usually, and that is most of the value in sending the whole spindle. Signals are read on the bench while the shaft turns, so a genuine encoder fault, a bad mounting and a bearing that is moving the shaft can be told apart. If the fault turns out to sit in the TNC or the drive, we report that instead.
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. Obsolete encoder types are the usual reason a job runs longer than that.
The spindle is stripped, measured and the feedback signals are read, and you get a written quotation before any repair work starts. The inspection is chargeable, and we tell you the charge before you ship so nothing is a surprise. Declined quotations mean the unit is returned; carriage is yours either way.
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.