SIEMENS6FX1121-4BA01SINUMERIK 800 Servo Interface / Measuring Circuit Board — Actual-Value Input and Setpoint Output, 20 mm Module Width, Board Only

Product Description

What this part is

A Siemens 6FX1121-4BA01 servo interface board for the SINUMERIK 800 series of CNC controls — the 810, 820, 850 and 880 family. In Siemens’ own installation documentation the 6FX1121-4B.. family is described as the measuring circuit module, and it is documented under two headings: the actual-value input measuring circuit and the setpoint output measuring circuit.

That pairing is what the board does. It is the hardware that sits between the CNC and one axis of the machine: it reads position feedback coming back from the axis measuring system, and it issues the speed or position setpoint going out to the drive. It is the board that closes the position loop.

Board class: servo / measuring-circuit board. A SINUMERIK rack also carries machine-interface I/O boards, operator-panel interfaces and serial communications boards, which are separate part families. A lost axis, a drifting position or an encoder alarm is the fault class this board family serves.

Decoding the order code

6FX: Siemens machine-tool control and drive hardware.

1121: the measuring-circuit / servo interface board group within the SINUMERIK 800 range. Siemens documentation refers to the whole group as 6FX1121-4B.., which indicates the boards share a function and differ by configuration.

-4BA01: the specific variant. Siemens catalogue text for this number reads “SINUMERIK 800 servo interface 20 mm (SPC)”, where the 20 mm is the module width in the rack. Adjacent variants exist in the same 4B.. group, and the exact variant code is the match.

570 214 9201.01: the Siemens internal board / drawing number printed on the PCB. A board label carrying this form rather than the 6FX order number is the same board.

Published data

Platform: SINUMERIK 800 series (810, 820, 850, 880).

Function: servo interface / measuring circuit — actual-value input and setpoint output.

Module width in the rack: 20 mm.

Board dimensions: approximately 279 mm x 203 mm (11.0 in x 8.0 in), with a stated packaged depth of about 25 mm (1.0 in).

Siemens internal board number: 570 214 9201.01.

Documentation authority: the Siemens SINUMERIK 880 Software Versions 1/2/3/4/5/6 Installation Instructions, which covers the 6FX1121-4B.. module at section 4.5 and the actual-value and setpoint measuring circuits at sections 8.1 and 8.2. Siemens Industry Online Support still hosts that document, and it carries the channel count, encoder signal types, setpoint output form and range, supply voltage, jumper and switch tables and connector pinouts.

Board-level configuration

Boards in this family are configured by jumpers and switch settings on the board itself: encoder type, signal scaling and drive interface selection. A board carries its factory default settings as supplied, and the jumper and switch tables in the Siemens installation instructions define the settings for a given axis and measuring system. The photographs on this listing show the board, and a read of specific jumper positions as received is available on request.

Quantity and configuration

One board, sold individually. A multi-axis SINUMERIK machine takes a measuring-circuit board per axis. The SINUMERIK rack and backplane, the front cover and handle, cabling and mating connectors, the measuring system or encoder, the drive module, and Siemens software and machine data are each separate items.

Interchange and obsolescence guidance

Search forms include 6FX1121-4BA01, 6FX11214BA01, 6FX1121 4BA01, 6FX 1121-4BA01, 6FX1121-4B, 570 214 9201.01 and 5702149201.01. Related documentation: Siemens SINUMERIK 880 Installation Instructions sections 4.5, 8.1 and 8.2.

The SINUMERIK 800 series is long obsolete. Siemens’ migration path is SINUMERIK 828D and 840D sl, which is a complete control retrofit rather than a board swap — new rack, new drives, new measuring systems, new machine data. Independent repair and refurbishment for 6FX1121 boards remains available in Europe. That gap between replacing a board and retrofitting the control is why original SINUMERIK 800 boards still command a price.