Delta Tau to Centroid Oak Retrofit on a Defiance VTX-1

Retrofit Scope and Machine Baseline

This is a field reference for replacing a Delta Tau motion control platform on a Defiance VTX-1 vertical machining center with a Centroid Oak control, retaining the existing Yaskawa drive package and spindle. The retrofit keeps all mechanical and power-conversion hardware that is still serviceable and replaces only the control layer, operator interface, logic power distribution, and safety circuit.

Control Architecture: Replace the Control, Keep the Drives

Retaining the Yaskawa axis and spindle drives is the decision that sets the entire interface strategy. The drives already match the motors, thermal load, and mechanical inertia of the machine, so the retrofit reduces to producing correct command, enable, and feedback signals from the Oak.

1. Confirm the drive command mode. Determine from the installed Yaskawa drive documentation whether each axis drive accepts an analog velocity command or a step/direction (pulse train) command, and confirm the Oak I/O set you are installing supports that mode. Do not assume the mode from the Delta Tau wiring alone — record the actual drive parameter settings before disturbing anything.
2. Capture the existing feedback path. Identify where encoder feedback terminates today (drive only, or drive plus Delta Tau). If the drive closes the position loop, the Oak issues a command and the drive reports ready/fault. If the control closes the loop, an encoder path back to the Oak is required.
3. Map drive status contacts. Drive ready, drive fault/alarm, and brake release (if fitted on the vertical axis) must land on discrete Oak inputs so faults surface as control messages instead of silent motion loss.
4. Preserve the Z-axis brake behavior. On a vertical spindle machine the Z brake must remain engaged until the drive is enabled and holding. Route the brake through the safety circuit so an E-stop drops the brake to the engaged state.
5. Re-establish home and limit references. Home switches, overtravel limits, and any hard-stop offsets from the original build must be re-verified after the control change; software travel limits are reset on the Oak, not inherited.

Power Distribution and 24 VDC Segregation

Incoming power is a single 220 VAC three-phase connection, with circuit breakers for branch protection. Two separate 24 VDC supplies are used rather than one:

Bond the 0 V references of both supplies to the enclosure ground bar at a single point unless a specific isolation requirement dictates otherwise, and document that point on the schematic. Keep the two 24 VDC rails on physically separate terminal blocks and label them distinctly — mixing them during later service is the most common way this design gets defeated.

Sizing the incoming feeder

Compute the service requirement from the sum of connected loads (spindle drive, three axis drives, chiller, coolant/hydraulic pumps, ATC, control transformer, and logic supplies), not from a nameplate guess. For the 220 VAC three-phase feed:

kVA = sqrt(3) x V_LL x I_line / 1000
I_line = (kVA x 1000) / (sqrt(3) x V_LL)

Example form only: with V_LL = 220 V, a 10 kVA aggregate load draws I_line = 10000 / (1.732 x 220) = 26.2 A. Substitute the actual measured or nameplate values for this machine; do not carry the example number forward. Verify breaker and conductor sizing against the applicable electrical code for the installation site, and size the chiller circuit for its locked-rotor/compressor starting characteristic rather than running current alone.

Safety Circuit, E-Stop, and Shutdown

Safety relays handle E-stop and machine shutdown as a hardwired function independent of the Oak and the PC. Software must never be the sole means of removing motion power.

1. E-stop devices in series into the safety relay input, with dual-channel monitoring if the relay and devices support it.
2. Safety relay output contacts drop the drive enable / main motion contactor. Do not rely on a PLC output to break motion power.
3. A second safety-rated contact set provides an input to the Oak so the control knows E-stop is active and can post a message and halt program execution cleanly.
4. Reset must be a deliberate manual action after all E-stop devices are released — no auto-restart on contact restoration.
5. Spindle stop on E-stop must account for a 25,000 rpm rotating mass. Confirm whether the Yaskawa spindle drive is configured for controlled deceleration on the shutdown path, and verify that the enclosure door interlock timing (if any) exceeds actual spindle coast-down time measured on the machine.

Custom Tool Changer PLC: 12 Position, ISO 10

The ATC logic is written from scratch in the Oak PLC because the original changer sequence lived in the Delta Tau program. Before writing code, instrument the changer and record actual behavior.

Structure the sequence as an interlocked state machine with confirmation on every motion:

PRECONDITIONS (all must be TRUE before ATC start)
  Air pressure OK
  Z at tool change height (machine coordinate, referenced)
  Spindle stopped and oriented (orient_complete = 1)
  No axis motion in progress
  Carousel retracted (retract_confirmed = 1)

SEQUENCE (each step waits for confirmation, times out on fail)
  1. Index carousel to target pocket -> pocket_at_position
  2. Advance carousel/arm         -> advance_confirmed
  3. Unclamp drawbar              -> tool_unclamped
  4. Z up out of taper            -> Z at clear height
  5. Index to new pocket          -> pocket_at_position
  6. Z down into taper            -> Z at change height
  7. Clamp drawbar                -> tool_clamped AND tool_present
  8. Air blast pulse, then retract-> retract_confirmed

Give every wait a timeout that raises a specific operator message identifying the failed step. A generic "tool change fault" costs hours on the floor; "drawbar unclamp confirm timeout" costs minutes. Verify each step manually in a PLC diagnostic/monitor screen with the spindle disabled before running an automatic cycle.

Spindle and Chiller Interlocks

The Swiss TDM spindle is rated 30,000 rpm and set to run at 25,000 rpm, matching the original configuration. Enforce that ceiling in two independent places: a maximum-RPM limit in the Oak spindle configuration and the corresponding upper frequency/speed limit parameter in the Yaskawa spindle drive. A limit in the control alone can be bypassed by a manual drive command or an MDI entry mismatch.

The liquid chiller runs an automatic cycle. Interlock it as follows:

• Chiller run/ready and any flow or temperature-alarm contact wired to Oak inputs.
• Spindle enable inhibited unless chiller status is healthy; a coolant loss at 25,000 rpm damages bearings quickly.
• Chiller allowed to continue running after spindle stop so residual heat is removed before machine shutdown — do not tie chiller power directly to the spindle enable output.

Commissioning and Acceptance Verification

Target performance for the completed machine is 400 ipm rapid, with linear accuracy and repeatability of 0.0002 (inch units, consistent with the ipm feed specification). Verify in this order:

1. Dry-run electrical checks. Motors disconnected mechanically where practical; confirm E-stop drops the motion contactor, confirm both 24 VDC rails at load, confirm all limit and home inputs toggle correctly in the Oak I/O monitor.
2. Axis direction and scaling. Jog each axis a commanded distance and measure with an indicator; correct counts-per-unit before tuning. A scaling error found after tuning wastes the tuning work.
3. Servo tuning. Tune each axis for stable following error at low speed, then step up to full rapid. Confirm no overshoot at rapid-to-stop transitions and no audible resonance.
4. Rapid verification. Command a long axis move and confirm 400 ipm is reached and sustained without drive fault or following-error trip.
5. Accuracy and repeatability. Measure linear positioning accuracy and bidirectional repeatability against the 0.0002 targets using a laser interferometer or calibrated ballbar/indicator setup. Record backlash separately; apply compensation only after mechanical condition is confirmed acceptable.
6. ATC endurance. Run all 12 pockets repeatedly with dummy ISO 10 holders, then with real tooling at working weight, and confirm no timeout faults across a full cycle set.
7. Spindle run-up. Step the spindle to 25,000 rpm in stages with chiller running, monitoring bearing temperature and drive current at each step.
8. Cut a test part. Final proof is a machined circle-diamond-square or equivalent geometry check, not a jog test.

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