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Stellarator Core Metrology issues

NCSX WBS-1 Meeting

April 2, 2003

•What are we measuring?

•When?

•How do we take the measurements?

•How do we correlate to CAD data?

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What are we measuring?

< R0 > = 1.4 m, Btor = 2 T, A = 4.3, Ip < 350 kA

Primary component measurements include:

In-vessel components Limiter surfaces, internal liner contour, internal coil current center

position, magnetic loops, etc. Vacuum Vessel

Shell surface, flange locations, port locations, support points, etc. Conventional coils

winding dimensions, current center locations, etc. Modular coils

winding dimensions, current center locations, flange locations, support points etc.

We also must measure the magnetic field surfaces, and reference these back to the coil set geometry

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Winding form tolerances Tolerances must be divided among various elements:

Baseline winding concept assumes winding form will be used as-is and not be custom shimmed or adjusted

Element Tolerance budget

Comment

Winding form +/- 0.01 in. Baseline on drawing

Copper cladding TBD Could be used to improve winding form tolerance if shims are allowed

Insulated conductor size +/- 0.01 in. Based on NEEWC input

VPI process TBD Assumed to be small, but not known

Assembly of coil in field period

+/- 0.020 in Adjusted to best fit, coil-to-coil with custom shims

Assembly of field periods +/- 0.020 in Adjusted to best fit with custom shims

Total tolerance +/- 0.06 in.

(+/- 1.5 mm)

Minimum value, may be relaxed according to location around winding

Winding

Winding form

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When do we make the measurements?

< R0 > = 1.4 m, Btor = 2 T, A = 4.3, Ip < 350 kA

During component fabrication e.g. Mod coil winding form inspection at vendor site

During component subassembly e.g. Individual conductor location on modular coils during winding,

net current center estimate for completed coil, etc.

During field period assembly e.g. measure flanges to determine required shim dimensions

between coils in a 3 coil pack, track the 3-coil assembly position as it is maneuvered over the vacuum vessel

During final assembly e.g. determine shim dimensions for mod coil flange connections, VV

spacer dimensions, port locations, etc.

And keep track of everything during machine operation

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We need to track the mod coil location during field period assembly and locate the ports

PortExtension

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How do we take the measurements?

< R0 > = 1.4 m, Btor = 2 T, A = 4.3, Ip < 350 kA

We need one or more metrology systems that include:

Measurement instruments These could include portable CMMs, such as a FARO arm, a laser tracker, a laser scanner, theodolites, etc. and would include any data acquisition hardware or computers needed to record data from the measurement instruments

Measurement software This would include the software needed to manipulate the measured data and perform optimization and best fit calculations.

Measurement standards This would include any calibration equipment or standards needed to maintain and verify accuracy of the instruments.

Measurement targets and monuments This would include the set of tooling balls, reference marks, holes, countersinks or other features required on the various components to establish the frame of reference for transferring data between measurement sets or for establishing the rigid body location of an object relative to other objects.

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How do we take the measurements? (2)

Scanning laser that attaches to 7-axis Faro arm (PPPL has one)

Integrated video camera takes points along scanned line @ 23,000 points/sec

Software determines part profile along line, “paints” image on CRT for operator and compares directly to CAD surface data

Accuracy is a function of the Faro arm only: ~ .003” for 6 foot arm, < .001” for 4 foot arm.

One interesting system is from 3D Scanners (http://www.3dscanners.com/)

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How do we take the measurements? (3)

NSTX has targets on vacuum vessel that can be seen from inside or outside

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How do we correlate to CAD data?

This is major QA issue

Most systems have this capability built into software

We also need optimization software to “best-fit” part contours and features with theoretical part, and correlate targets/monuments with global coordinate system

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Maybe we need a measurement matrix

Think through the fab/assy/operating steps List what needs to be measured, when, and how

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Some issues

Accuracy of measurements vs speed Can we take our measurement system to

vendors to verify their measurements? Distortion of parts during assembly or during

operation (moves the targets/monuments relative to each other and part)

Targets disappear Comparison of measurements to CAD data Optimization / “best fit” of part to data How / when do we measure magnetic surfaces? $$$$

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What do we do next?

Form a task force to:

Develop measurement matrix for all components (what, when, how) with help of WBS managers

Determine best set of tools (hardware/software)

Develop plan for any needed R&D

Work with WBS managers to determine type and locations of targets/monuments that will provide continuity of measurements throughout fabrication/assembly/operation phases

Data needed soon for modular coils and vacuum vessel!