HeidenhainROD-450-2540ROD 450 Incremental Rotary Encoder, 2540 Lines, 10 mm Solid Shaft, Integral Bearing

Product Description

What this part is

A Heidenhain ROD 450 incremental rotary encoder, 2540 lines per revolution, Heidenhain ID 251 568. It is a shaft-driven feedback device with an integral bearing: turn the shaft and it delivers quadrature incremental signals plus a reference mark, which the counter, drive or CNC turns into position, direction and speed.

Correcting the source data

The brand field previously read Heidenhain ROD. ROD is Heidenhain’s designation for its incremental rotary encoders with integral bearing and solid shaft, not part of the company name — the manufacturer is Heidenhain and ROD 450 is the model.

Decoding the designation

ROD — rotary encoder, incremental, integral bearing, solid shaft intended for use with a separate shaft coupling450 — the model within the ROD 400 range2540 — line count, i.e. 2540 signal periods per revolution251 568 — Heidenhain ID number, the identification the factory and its distributors work from. The trailing -1N is the variant marking on this unit.

Why 2540 lines, and why it matters

2540 is not a round metric number and it is not an accident. There are exactly 2540 hundredths of a millimetre in an inch, and 2540 divides cleanly by 10, 20 and 127 — the numbers that appear when an imperial-leadscrew machine has to display and position in inches without an awkward scaling factor. Encoders with counts like this are almost always fitted to imperial machine tools, imperial-pitch ballscrews and inch-based retrofits, where a 2500-line encoder would leave the control carrying a non-integer ratio. The practical consequence: if you are replacing a 2540-line encoder, replace it with a 2540-line encoder. Fitting a 2500-line unit in its place will not fault the machine — it will quietly produce a 1.6% position error, which is exactly the kind of fault that gets chased for a week.

Published specifications

Type: incremental rotary encoder with integral bearing, Heidenhain ROD 400 rangeModel: ROD 450Line count: 2540 per revolutionMeasuring steps after 4-fold evaluation: 10 160 per revolutionShaft: 10 mm solid shaft, for a separate shaft couplingMounting: synchro flange, coupled to the drive or spindle via a separate rotor couplingReference mark: oneHeidenhain ID: 251 568Variant marking on unit: -1NCountry of manufacture: Germany

Installation and setup notes

The ROD range is designed around a separate shaft coupling, and that is not optional good practice — a flexible or stator coupling absorbs the misalignment and axial float that would otherwise go straight into the encoder’s own bearing. Coupling a ROD rigidly to a shaft with runout will shorten its life and can degrade the signal. Keep the encoder cable screened, grounded at the housing, and routed away from motor and drive power cabling; incremental feedback picking up inverter noise produces intermittent count errors that look like a mechanical fault. Confirm the count direction against your axis convention at first jog rather than assuming it, and check the reference mark is found where the control expects before running a datum cycle at speed.

Quantity and configuration

One encoder. The shaft coupling, mating connector or cable assembly, mounting hardware and any counter, interpolation or interface electronics are not included.

Interchange guidance

Two things must match, not one. The line count has to be 2540, for the reason set out above. And the output interface has to match what your control expects — the Heidenhain ROD ranges were supplied with TTL square-wave, HTL and analogue outputs depending on the model, and a control expecting one will not read another, even though the flange and shaft bolt up identically. Order against the ID number 251 568 where you can, since it pins the exact build. Other ROD 400 models, such as the ROD 426, ROD 436, ROD 466 and ROD 486, share the family and the mounting concept but differ in shaft diameter, interface and available line counts — related items, not equivalents. Also written ROD450, ROD-450-2540, ROD 450.2540, ID 251568, 251-568-1N and 251 568-1N.