Space / Time Control

Width Calibration Manual
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Preface

The goal of groove width calibration is to align the depth signal sent by the software with the actual movement of the dynamic depth adjustment mechanism.

The SDMS head suspension box enables both mechanical and electrical adjustments for groove depth. The mechanical adjustment sets a base groove depth, while the electromagnetic system allows for dynamic and fine-grained depth control, which can be automated by the software.

Due to the V-shape geometry of a groove, its width is always twice its depth. Although the electromagnetic system technically controls groove depth, STC uses GROOVE WIDTH as the primary measurement for groove geometry, since this is what can be observed directly through the groove inspection microscope.
Read and follow the instructions below carefully. If unsure about a step, please contact our support. The signals sent to the system during the calibration procedure can potentially damage your system. You will perform all calibration steps at your own risk.

Prerequisites

Abbreviations
SDMS
Sillitoe Disk Mastering System hardware
STC
Space / Time Control software

References

STC Lathe Calibration Dialog
STC Lathe Calibration Dialog
SDMS Master Control and Space / Time Control Hardware Modules
SDMS Master Control and Space / Time Control Hardware Modules
All alphabetical and numerical references in this manual refer to the images above.

Calibration Procedure

Manual Baseline Cut

  1. Disable CARRIAGE L and HEAD P automation (LED buttons OFF)
  2. Enable DEPTH H automation (LED button ON)
  3. Perform a manual test cut of a silent groove for 3…5 revolutions
  4. Measure the average groove width using the groove inspection scope and record it as your GROOVE WIDTH BASELINE
In the default configuration of the groove inspection scope with a 10x objective, one division in the ocular scale equals 5 µm.

Groove Width Calibration

Prepare STC and SDMS for the calibration cut:

  1. Launch STC and open the Lathe Calibration dialog
  2. Confirm your SDMS Master Control and Space / Time Control hardware modules are connected 7
  3. Enter your GROOVE WIDTH BASELINE value as a negative WIDTH OFFSET 4
    (Example: If you manually cut a 50 µm wide groove, enter −50 µm as WIDTH OFFSET 4)
  4. Set the WIDTH FACTOR 5 to 2.00
  5. Select WIDTH CALIBRATION 1 as the source and set:
    • PITCH 2 to 100 µm
    • REVOLUTIONS 3 to 3 rev
  6. Enable automation for DEPTH H, CARRIAGE L and HEAD P (LED buttons ON)
  7. Ensure the carriage direction M is set to F(orward)
  8. Set the TURNTABLE SPEED to 33 J
  9. Switch on the TURNTABLE K and VACUUM & STYLUS HEAT Q

When ready to cut:

  1. Press REC 6 to start the calibration cut
  2. The software will cut a groove with increasing width from 50 µm to 90 µm Each width will be held constant for the number of revolutions you set above (default: 3 rev)
  3. The test will stop automatically when complete
Evaluation of the results
  1. Inspect the groove using the groove inspection scope
  2. Measure the average width of each groove section and note the values in the table below
Groove Width Calibration Results
EXPECTED WIDTH MEASURED WIDTH
50 µm
60 µm
70 µm
80 µm
90 µm
It's easiest to start from the end of the cut and count the revolutions backwards, to find the next section. The five sections of three revolutions at constant width will be separated by a slightly larger land area.

Send your measured results to calibration@spacetimecontrol.com for review and evaluation of your WIDTH FACTOR and WIDTH OFFSET parameters.

If you are already familiar with the width calibration procedure, you can also enter your results into the Width Calibration Utility and find the optimized values for WIDTH FACTOR and WIDTH OFFSET yourself.

Troubleshooting

Slight variations in lacquer thickness will create slightly wider or narrower grooves. The same is true after switching to a new stylus.

If you see a width offset in a test groove with a fresh lacquer or new stylus, you can correct the WIDTH OFFSET to recalibrate the system using the following formula:

Expected Groove Width = 50 µm

Measured Groove Width = 55 µm

Width Offset Delta = 50 µm − 55 µm = −5 µm