Configuring SINUMERIK 810T GA2 Turret Base Offset via MD5007

Configuring SINUMERIK 810T GA2 Turret Base Offset via MD5007 Bit 3

Problem Overview

On SINUMERIK 810T GA2 turning controls fitted to turret-equipped lathes (typical of the Spinner SB series and similar 1980s–1990s CNC slant-bed lathes), operators and setters can enter Base offset values into correction-memory parameters P8 and P9 of a cutting tool, but the controller silently rejects them. The most visible symptom is that a turret-mounted drill does not drive to the programmed spindle centerline during a drilling cycle. The turret indexing position is mechanically accurate to its dividing plate, but the program coordinates appear to be ignored because the additional X/Z axis offsets stored in P8/P9 never become active in the position calculation.

The underlying root cause is a single configuration bit: machine data word MD 5007, bit 3. On a default GA2 shipment the bit is cleared (0); the correction memory is presented to the user as a ten-parameter block but only parameters P0–P7 are evaluated as actual offsets. Until bit 3 of MD5007 is set to 1, P8 and P9 are displayed, can be written, and are lost the next time the tool is deleted.

Affected Systems

Understanding the Tool Offset Memory on SINUMERIK 810T GA2

The SINUMERIK 810T GA2 dedicates a fixed block of ten parameters to each defined cutting tool (typically tools T01–T32, depending on installed option). The block structure for GA2 is:

The first eight parameters (P0–P7) are always evaluated. The P8/P9 base offsets exist in the data structure but are gated by a configuration bit so that legacy 4-parameter or 8-parameter workflows can be preserved without bookkeeping noise.

Why a "Base" offset exists at all

On a turret lathe, every turret station is physically located on a different pitch-circle radius from the spindle centreline. Mechanical tolerances, repeated turret-indexing shock, and chucked-stock deflection all contribute to a station-by-station residual position error that is systematic — the same error appears every time the same station is indexed in. The compensation value is therefore constant per tool/station, not per part. The Base parameters (P8/P9) provide a clean place to store this systematic offset separately from the geometric length and wear offsets that change with grinding and re-sharpening.

Root Cause: MD5007 Bit 3 Inhibits Base Offset

The general machine bits word MD 5007 is a single 8-bit configuration value in the SINUMERIK 810T GA2 machine data list. Each bit toggles a discrete NC behaviour. Bit 3 specifically controls whether the upper half of the 10-parameter tool-offset block (P8/P9, the "Basis" slots) is included in the active offset calculation.

The displayed bit pattern is shown with the LSB on the right:

Bit:        7 6 5 4 3 2 1 0
Default:    X X X X 0 X X X
After fix:  X X X X 1 X X X

The other seven bits remain at their previous values — only bit 3 is being toggled. On a fresh or default-configuration machine, MD5007 is typically initialised to 0x00 (all bits clear), so P8/P9 are silently masked out. Entering non-zero values into P8 or P9 produces no alarm, no error code, and no operator message; the data simply has no effect on the part program.

This silent-rejection behaviour is, in practice, what makes the failure confusing: a setter confirms the values are entered, re-runs the drilling cycle, and observes that the tool still drives to the nominal spindle centreline rather than to the corrected position.

Diagnostic Procedure

Perform the following checks before changing any machine data. The goal is to confirm that the symptom is in fact the MD5007 bit-3 lockout and not a related fault (NC card defect, corrupted battery-backed SRAM, tool-management enabled with empty adapter data, or a wrong tool number invoked by the program).

1. Identify the generation. On the operator panel navigate to Diagnosis → Machine data and read MD 0000 (firmware identifier). A value starting with 02. or 03. indicates GA2/GA3 hardware. Confirm the NC card label (typical 6FX1132-8BB01 on GA2) against the machine documentation. See the official installation list at SINUMERIK 810 GA3 / 820 GA3 Installation Instructions for compatible NC card and module combinations.
2. Verify the offset memory layout. From the same screen, open any defined tool (for example T01) and confirm that ten parameter fields P0–P9 are present. If only eight fields are shown, the controller is in a reduced-offset mode and MD5007 bit 3 cannot be set meaningfully; investigate the machine-data bit configuration first.
3. Enter a test base offset. In P8 (Basis X), enter 1.000 mm. Press Input or Save. Re-read the value. If the value persists in the display but is reset to 0 after a tool-delete operation, this is consistent with the MD5007 bit-3 lockout (the value is held in storage but not used).
4. Check the active machine bits. Display MD 5007. Record the current value (e.g. 00001010). The third bit from the right is bit 3. If it is 0, proceed with the fix below.
5. Rule out tool-management confusion. If the machine is configured with tool management and adapter data (GA2 with tool-management option SW 3.x and later, or GA3), the offset for a given turret station is typically carried in the adapter data block rather than in P8/P9. In that case set the bit 3 of MD5007 only if you intend to use the classic P8/P9 base offset method — do not mix adapter-data offsets with manual P8/P9 values for the same tool, as the two paths will conflict.

Resolution: Setting MD5007 Bit 3

Set bit 3 of machine data word MD 5007 to 1 using the MASCH.-BITS softkey path. The procedure is intentionally short — the difficulty is not in execution but in recognising that this is the cause.

1. Place the control in Operator/Setup mode and ensure the machine is stopped, the drives are de-energised, and the part program is reset. The bit change itself does not require a particular mode, but tool-data edits and machine-data edits should be performed in setup with the part program reset.
2. Navigate to the machine-data display and select MD 5007.
3. Press the MASCH.-BITS softkey. The current value is displayed as eight characters, e.g. XXXX0XXX, where each X represents the unchanged value of that bit.
4. Move the cursor to the bit-3 position (fourth character from the right) and toggle it from 0 to 1. The seven other bits must remain unchanged.
5. Press Input (or Save) to commit. The control will typically display a confirmation prompt such as MD 5007 = XXXX1XXX?. Acknowledge.
6. Exit the machine-data editor. The change is effective immediately; a warm restart of the NC is not required on GA2 hardware, although a brief confirmation in the operating-mode screen is recommended.
7. Verify by entering a non-zero value into P8 and P9 for a test tool (see the verification section below).

Verification

Verify the fix in three layers: data persistence, NC behaviour, and machining result.

1. Data persistence test. Enter a recognisable non-zero value into P8 (Basis X) and P9 (Basis Z) for tool T01, for example P8 = +1.250 mm and P9 = +0.500 mm. Delete and re-create the tool (or power-cycle the NC). On re-display, the values must remain.
2. NC behaviour test. Run a part program that includes a positioning move in G0 or G1 to the T01 offset position with the test tool. With hand-wheel or incremental jog, command a move to the workpiece zero and verify that the displayed axis actual values reflect the offset by exactly the amount stored in P8/P9. A common quick test is to put a dial indicator on the turret station and command a 1 mm move; the indicator should reflect 1 mm plus the stored P8/P9 value.
3. Machining test. Run a simple drilling cycle (CYCLE81 or a hand-written drilling block) at the corrected station. The drill must enter the workpiece at the corrected centreline, not the nominal spindle centreline. Repeat with several turret stations to confirm the base offset is stored per tool, not globally.

Turret Pitch-Circle Compensation in Depth

Mechanical reality: on a 12-station disc turret the pitch-circle diameter is the bolt circle on which the twelve tool pockets lie. Manufacturing tolerance on this bolt circle is typically ±0.02 mm. Combined with chuck/clamping repeatability and the deflection of an extended boring bar (which can add another ±0.01 mm at the tool tip), the residual station-to-station variation often exceeds the diameter tolerance of a precision bored hole. That is the entire reason a per-station base offset exists.

The compensation workflow is straightforward:

1. Index each turret station to a known reference position (typically the spindle centreline) and measure the residual error with a dial test indicator (DTI) or a precision mandrel.
2. Record the signed error (X-axis error in P8, Z-axis error in P9) for each station.
3. Enter the values into the matching tool number's P8/P9 slots.
4. The control now adds P8 to the geometric X length (P1 + P4) and P9 to the geometric Z length (P0 + P3) for every positioning move that uses that tool.

Persistence and tool deletion

On a SINUMERIK 810T GA2 with MD5007 bit 3 set, P8/P9 are part of the tool's permanent record in SRAM. They survive part-program resets, mode changes, and power cycles. They are lost, however, when the tool is explicitly deleted via the tool-management delete softkey — that operation zeroes the entire 10-parameter block. Re-creation of the same tool number restores an empty record; the values must be re-entered. This is the desired behaviour for shops that wish to clear offsets deliberately, but it surprises users who treat P8/P9 as if they were machine data.

Adapter Data and Modern Tool Management

On later GA2 software loads (SW 3.x with the tool-management option) and on all GA3 machines, the cleanest way to carry per-station pitch-circle offsets is via adapter data. An adapter is a logical holder for a fixed mechanical relationship (chuck, turret station, angular head, etc.). Each adapter carries its own offset record, and a tool assigned to that adapter inherits the adapter offsets without having to write them into the tool's P8/P9 slots.

Practical guidance:

• If the machine is configured for tool management with adapters (check MD 0x1000–0x1FFF range and the user screen layout for an Adapter column), prefer adapter-data offsets over P8/P9. They survive tool deletion automatically and are easier to audit.
• If the machine is in legacy 10-parameter mode without tool management, MD5007 bit 3 = 1 with P8/P9 per tool is the correct and intended workflow.
• Do not mix the two for the same physical station. Whichever mechanism is active will overwrite the other in the active offset chain.

Bit Pattern Reference

For quick reference, here are the MD5007 bit assignments on SINUMERIK 810T GA2. Some bit functions are tool-related and some are general; the table reflects the most commonly documented usage. Always cross-check against the machine-data print-out shipped with the specific machine, as Siemens occasionally resampled bit semantics between software releases.

Hardware Considerations: 6FX1132-8BB01 and Compatible NC Cards

The SINUMERIK 810T GA2 system is built around the 6FX1 family of NC CPU cards. The 6FX1132-8BB01 part number is a common GA2-era NC card and is referenced in service notes for the family. When this or a compatible card fails, the replacement card is typically supplied with default machine data, which means MD 5007 returns to 0x00. After a card swap, the symptom described in this article (silent rejection of P8/P9) will reappear unless bit 3 of MD 5007 is re-enabled.

Procedure after an NC card replacement:

1. Restore the machine-data series from the documentation file or the prior backup. Verify MD 5007 is set correctly.
2. Verify the tool offset memory: at minimum, restore P0–P9 for every active tool from the backup set.
3. Verify part-program reference points and zero offsets.
4. Run a single-station cutting test on the most-used turret position before resuming production.

For ordering and compatibility information on 6FX1 spare parts, consult the Siemens product support portal directly; the part-number lifecycle for legacy 6FX1 cards ended many years ago and replacements may only be available as refurbished or repaired units.

Safety Considerations

Machine-data changes on a turning centre directly affect axis behaviour. Apply the following precautions:

• Perform the MD5007 change with the machine stopped, in setup mode, with the part program reset.
• Document the change in the machine log: original value, new value, date, and operator.
• Before running production parts, execute the verification block (data persistence → NC behaviour → machining test) end to end on the affected station.
• If the machine has tool management and adapter data configured, do not enable bit 3 of MD 5007 without first reviewing the offset chain; double-offsetting the same physical station can shift the spindle centreline by the sum of the two values and produce scrap or a tool crash on the first cut.

Troubleshooting Matrix

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