Resolving Doosan Z290SM Part Catcher B-Axis Lockout

The part-catcher arm opens with M6, but its basket remains near the middle of Z travel and the B axis cannot move toward it. On the Doosan Z290SM with FANUC 18T control, this combination points to the B/Z2 reference-position interlock. Return the axis to the machine’s second reference position with G30 B0, then repeat the catcher sequence.

Initial position decision

1. Stop the automatic cycle and confirm that the catcher, workpiece, tools, Sauter heads, both spindles, and doors are in collision-free states. Do not issue a reference-return command until the expected B-axis path is clear.
2. Command the machine-specific catcher function M6. If the arm opens but does not travel along Z, inspect how the catcher is mounted. On this machine, the arm is fixed to the door; opening the arm does not provide independent Z positioning.
3. Attempt B-axis movement only under the machine’s permitted setup conditions. If alarm 2050, B/Z2-AXIS HOME POSITION NEED, appears, stop testing catcher motion and take the second-reference branch below.
4. Command G30 B0 to return B to Home #2. Confirm completion without alarm before requesting any further B-axis or catcher-related movement.
5. Repeat the intended positioning sequence. Do not move on until the B axis is released for commanded motion and its position brings the workpiece into the catcher’s pickup geometry.

Catcher and B-axis motion roles

The visible symptom can suggest that the catcher arm has failed to move in Z. That interpretation does not match this installation: the arm is permanently mounted to the door, so its opening action and the workpiece-to-basket positioning action are separate functions. The arm opens to place the basket in its receiving state; the machine then depends on B/Z2 positioning to establish the required relationship between the opposite spindle, its workpiece ejector, and the basket.

The functioning ejector does not prove that the B-axis reference condition is valid. Ejector output, catcher opening, and B-axis travel can have separate permissive chains. A successful M6 therefore confirms only that the arm-opening branch was accepted. Alarm 2050 identifies the branch that still blocks the sequence.

Treat M6 as a machine-builder assignment for this Z290SM configuration, not as a universal catcher command for every FANUC-controlled machine. FANUC executes the command interface, while the machine builder defines much of the auxiliary sequence and interlocking around doors, chucks, ejectors, and catchers.

Alarm 2050 interlock mechanism

Alarm 2050 carries the text B/Z2-AXIS HOME POSITION NEED. Its wording ties the rejected action to the reference status of B/Z2 rather than to the catcher actuator itself. A machine reference position is both a coordinate landmark and a logic state: the control or machine ladder can require that state before releasing another motion or auxiliary operation.

Normal axis position, a visually plausible location, and a valid home permissive are different conditions. An axis can display a coordinate and still fail the interlock because it has not completed the required reference-return operation. Likewise, reaching the primary machine reference does not substitute for a separately stored second reference position when the sequence expects Home #2.

The diagnostic rule is direct: when the arm opens and alarm 2050 appears as B motion is requested, establish Home #2 before investigating the ejector or treating the fixed catcher as a failed linear axis.

Home #2 positioning procedure

Before anything else, confirm that automatic movement toward the stored reference position cannot strike a spindle, tool, workpiece, catcher, or turret. Reference-return commands can move an axis immediately after cycle start.

1. Select the operating mode required by the machine to enter and execute a single CNC block.
2. Review the displayed B-axis position and the physical clearance around the complete moving assembly. Remove any setup condition that would make the stored return path unsafe.
3. Enter G30 B0 exactly as a B-axis block. Do not append unverified axes or auxiliary commands.
4. Execute the block while observing B-axis motion and the alarm display. Be ready to stop motion if the physical path differs from the expected return path.
5. Confirm that the command completes at Home #2 and that alarm 2050 is no longer preventing the next operation.
6. Request B-axis movement toward the catcher at a controlled commissioning pace. Confirm direction and clearance before approaching pickup position.
7. Open the catcher with the established machine sequence and test the ejector-to-basket alignment without committing to an unattended production cycle.

G30 B0 is the resolving command recorded for this machine and control combination. Do not replace it with a guessed reference-return block or edit stored reference data merely because the alarm contains the word “HOME.” The required target is Home #2.

Non-clearing alarm branch

If G30 B0 does not restore B motion, use the first new alarm or status indication as the next decision point. Repeating the command without identifying the active inhibit can conceal the actual prerequisite.

A lost or incorrect second-reference value changes the problem from normal operation to machine setup or service. Record the current coordinate display, alarm text, and relevant diagnostic states before changing reference-related data.

Controlled functional verification

1. Start from a known, collision-free condition and execute G30 B0.
2. Confirm Home #2 completion and verify that alarm 2050 does not reappear when the next B-axis action is requested.
3. Command M6 and confirm that the fixed door-mounted arm opens fully.
4. Move B toward the receiving position under observation. Confirm that the workpiece path aligns with the basket and that no turret, spindle, door, or catcher component enters an interference zone.
5. Test the opposite-spindle ejector with the basket correctly positioned, then confirm that the released part lands in and remains contained by the basket.

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