Twisted Racetrack Manufacturing & Metrology

Winding/metrology prototype chronology Various keystoning tests – Completed. –Established keystone effect vs. radius for several conductors. Plain oval – Completed. –Wound coil primarily for electro-mechanical testing. Verified that the VPI groove worked. Did not use the current conductor or chill plate design. No metrology on coil. Inchworm – Completed. Straight Tee – Near completion. Twisted Oval – Near Start. Full sized Prototype – Cancelled.

Winding/Metrology History - Inchworm –The inchworm is a prototype with the following goals. Develop winding techniques on a curved surface. Test the clamp system on a curved surface. Development of a mechanical measurement (MMT) tool. –The inchworm had the following conditions/limitations: The surface was not machined and was not a viable platform to make accurate measurements. –What we learned: The first generation clamps (swing arm clamp) were not viable – new clamps were designed and built. The MMT was a viable instrument for measurement. The MMT could be removed and re-installed onto the same location and reproduce the previous measurement to +/ ”. a G-10 pad between the conductor and the MMT is needed. In addition to being spongy, there are too many undulations in the glass-wrapped conductor. The width of this pad is critical. When laid onto a curve surface a wide pad produced as much as.020” error.

Winding/Metrology History-Straight Tee –The straight tee is a prototype with the following goals: Refine the sprue system. Take measurements with the MMT. Prototype the lead details. –The straight tee was wound with the following conditions: Clamps on 6” centers. No outer chill plates ” glass cloth shim inserted between each row. No spherical seat/no fastening of clamps on bottom end. No shimming to a predetermined height – the conductor was measured and compared to nominal growth. Statistical data was taken. –What was learned Stack gets “springy” as it grows. The copper chill plates must fit the tee geometry precisely or large deviations (+.020”) can occur. The ground wrap is in the way – the winding clamps and MMT had to be redesigned to make room. By varying clamping force and tamping of the conductor, the conductor surface can be moved +/ ”. (after 4-5 rows are installed). The pads used to spread the clamping loads got in the way had to be constantly shifted to accommodate the measurements.

Metrology/Measurement Results – Straight Tee The following is a summary of the measurements taken on the straight tee: –The form was measured to establish a baseline. Measurements were taken at six locations (between six-inch centers). Additional measurements were taken after the copper was installed and after the 2 nd, 5 th, 8 th and 10 th rows. All measurements were taken from the counter-bores at the top of the tee. A G-10 pad was placed on top of the conductor and the MMT was used to measure the height across the entire width of the four conductors. Final dimensions were derived by subtraction. –The precision of the MMT was established by making repeated measurements at the same location(s). The MMT would measure the same location to a precision of approximately +/ ”. This is very good considering that the machining of the straight tee was not to the greatest precision possible. –The standard deviation of the measurements was small – especially for the early rows. It got worse as the stack got spongier. –We did not/could nor measure between clamping locations. We don’t know what the bulge is, however when we wind with clamps at 3” centers it will be minimized. (we cannot get clamps any closer than 3”). –Recommend that we dissect the straight tee and evaluate the cross section.

Twisted tee – Measured results BaseBase+Cu2-turn5-turn**8-turn10-turn Desired (theoretical build-up)N/A Mean (average of all measurements)  Desired (ave. deviation from desired) N/A std. deviation of the mean Range (+/- extremes of measurementN/A-.001 to to to to to ** one data point excluded.

Metrology for the Twisted Racetrack Measurements: –For the Casting Using the Romer arm, the casting will be measured against the CAD model. A “best fit” to measured points will be performed. The best fit can be performed using measured points from the entire casing (which will yield the smallest  for the entire casting), or distinct features can be used for the alignment. Using distinct features to align can yield a tighter  for an important area, however the remaining area may fall out of tolerance by a greater amount. After the best fit is accepted, we shall always use 3 point alignment (3 tooling balls or holes). This will guarantee that we consistently realign to the same reference –For the Coil Winding Process The winding can be measured with a local measuring tool (micrometer based), or with the Romer. With either method the clamps and the pressure pads (they spread the clamping load over conductor surfaces) are in the way and will have to be moved. The Romer arm will require a CAD model with specific point(s) (for each turn) to be measured. The Mechanical measurement tool will use a specific gauge block for each elevation. The micrometer will be inserted onto the gauge block and zeroed. While measuring the conductor, a zero reading is perfect. Deviations (in +/- thousands of an inch) from the desired location will be read directly on the dial indicator. The arrangement of the conductors (shimming between layers) needs to be predetermined so that the gauge blocks can be fabricated for the specific measurements. With the MMT, we can also adjust “on- the-fly” by making the calculations in the field. For the Romer, we will have to have predetermined coil locations so that we can make CAD models to measure against. The mechanical measurement tool is limited in measuring at discreet locations between clamps. We can measure perpendicular to the filament along the entire height and width of the coil. Recommend that we measure and position the coil with the MMT. It will be as accurate and faster than the Romer. We should use the Romer for measuring the coil to verify the MMT measurements and to establish the experience/techniques.

Conclusions At each new step in the winding R&D we have had surprises that have forced us to redesign our tooling and rethink our methods. This will hold true for the twisted racetrack. We have not had an opportunity to wind a coil under the following conditions: –on a precisely machined, twisted cross section. –with the final chill plate design and cooling tubes. – with clamps on 3” centers. There are elements of the process that may present difficulties that are not determined/resolved: –Fitting copper chill plates onto the curved surface. –Laying in the ground wrap onto the curved surface. –Ability to install clamps on 3” centers in the tight radius areas. We may need to fabricate special saddles for these regions. –Configuration of the pads that spread the clamp load. We have no experience with pads for a curved surface. –Springiness of the pack and how it reacts as clamps are removed for winding and measuring. –Ability to reposition the coil back to the desired location after the outer chill plates and bag mold are installed. We loose sight of the coil!! The tools that we are measuring with (the MMT and the Romer) have the accuracy and precision to measure and locate the coil conductor within the prescribed accuracy. Our ability to keep it there as we go into the VPI stage is the largest variable in this process.