Manufacturing and Quality Assurance

1. Manufacturing and Quality Assurance Magnet Production Workshop Frank DePaola April 11-12, 2012

2. Abstract Manufacturing and Quality Assurance Frank DePaola, NSLS-II Project Building Quality into the Magnets necessitates that the quality requirements for the performance specifications are incorporated into the production process and methods used to produce the magnets. This is accomplished through manufacturing travelers, documented procedures, early QA involvement that takes a proactive approach for preventing defects, and the use of established best practices for manufacturing the coils and yokes. *Work performed under auspices of the United States Department of Energy, under contract DE-AC02-98CH10886 DOE Review of the NSLS II Project, November 15 - 17, 2010 2

3. OUTLINE • Manufacturing and Quality Assurance Interface • Build Quality into the Product • Manufacturing Travelers • Role of Quality Assurance in Manufacturing • Magnet Production • Magnet Yoke Fabrication • Magnet Coil Fabrication • Magnet Assembly Magnet Production Workshop – April 11-12, 2012 3

4. Build Quality Into The Product Successful manufacturers build quality into their products • The quality necessary to achieve the required specification is designed and planned into the product upfront – it than becomes integrated into the manufacturing methods used to produce the product • This is accomplished through the use of manufacturing travelers, documented procedures, inspection and test plans, engineered tooling and fixtures, and continuous improvement Magnet Production Workshop – April 11-12, 2012 4

5. Manufacturing Travelers The single most important item is the manufacturing traveler • Sequential listing of required tasks • References special work instructions and procedures • Incorporates in-process inspection and test requirements • Captures individual part data (actual measurements & test results) • Provides hold points that require approval prior to proceeding • Historical record for each individual item produced • Provides consistency from part to part throughout the production run Magnet Production Workshop – April 11-12, 2012 5

6. Role of Quality Assurance in Manufacturing • Provide a systematic and proactive approach for preventing defects • Implement procedures that ensure manufactured products consistently meet the required quality specifications • Incorporate the QA requirements into the manufacturing traveler • Perform audits to ensure: • Established procedures are being followed • Personnel performing the work are adequately trained • Equipment is calibrated and in good repair Magnet Production Workshop – April 11-12, 2012 6

7. Magnet Yoke Fabrication MATERIAL • Ideally all magnets from the same family are manufactured from a single batch of steel (same heat) • Shuffling systematically distributes the steel properties among all the yoke segments and ensures that all the magnets in a single family have reproducible and uniform magnetic properties • Sorting ensures that variations in the sheet thickness (caused by crowning during the rolling process) are systematically distributed – If the laminations are symmetrical they can be flipped during the stacking process Magnet Production Workshop – April 11-12, 2012 7

8. Magnet Yoke Fabrication Solid Steel Yokes or Steel Laminated Yokes Solid Steel Yokes • Machined from a solid block of material • Cannot be cycled or pulsed rapidly (eddy currents) • Acceptable for use in storage ring accelerator applications • Should be considered if a small number of magnets are required Magnet Production Workshop – April 11-12, 2012 8

9. Magnet Yoke Fabrication Solid Steel Yokes or Steel Laminated Yokes Laminated Steel Yokes • Joining Methods – Glued / Welded / Combination of gluing and welding • Gluing is generally used for magnets that are < 0.5 meter in length • Longer dipole magnets are more suited to a welded construction • Trying to glue dipole magnets that have a long length to yoke cross section ratio is very difficult to accomplish – and stacking curved dipole magnets adds yet another level of complexity Magnet Production Workshop – April 11-12, 2012 9

10. Magnet Yoke Fabrication Solid Steel Yokes or Steel Laminated Yokes Cost Comparison “ Typical undocumented studies have shown that the cost of fabricating a few (≤ 4) laminated magnet yokes is dominated by the tooling costs and exceeds the cost of machining the same number of yokes from solid blocks. However, these same studies have shown that the cost of machining exceeds the cost of fabricating laminated cores for the typical accelerator application where the tooling costs can be shared by the larger number of core segments.” (J. T. Tanabe) If secondary machining is required to achieve high mechanical precision the cost advantage offered by laminated yokes is lost Magnet Production Workshop – April 11-12, 2012 10

11. Manufacturing Process Comparison Magnet Production Workshop – April 11-12, 2012 11

12. Magnet Yoke Fabrication Preparing Laminations for Stacking and Bonding • Unclean laminations will result in poorly bonded yokes • Laminations contaminated with stamping lubricants or cutting oils and handling laminations with bare hands that can leave dirt and oily finger prints on the surface • Important to handle the laminations wearing clean lint free gloves and cleaning the laminations prior to stacking using a recommended or proven cleaning method Magnet Production Workshop – April 11-12, 2012 12

13. Magnet Yoke Fabrication Preparing Laminations for Stacking and Bonding • Burrs on lamination cut edges and other defects (bent or creased laminations) will result in poorly bonded yokes with low and inconsistent packing densities • Indications of these defects can generally be observed on the outer surface of the yoke at the un-bonded area • Incorporate a visual inspection of laminations – a deburring process – and a sorting procedure to ensure that defective laminations do not end up in the stacked yoke Magnet Production Workshop – April 11-12, 2012 13

14. Magnet Yoke Fabrication Yoke Stacking / Bonding Fixture • Stacking fixtures that do not apply an evenly distributed pressure across the entire yoke and a constant pressure throughout the bonding cycle will result in poorly bonded yokes • Some stacking fixtures had to be modified to incorporate the following standard practices and features A) Engineered to be sufficiently rigid so that it will not deflect or deform under the applied forces Magnet Production Workshop – April 11-12, 2012 14

15. Magnet Yoke Fabrication Yoke Stacking / Bonding Fixture B) The clamping arrangement must apply a uniform pressure across the entire yoke • Provide as many clamping positions as possible • Ideally located directly over the laminations or at least as close as possible to the laminations • Positioned in a symmetrical arrangement Magnet Production Workshop – April 11-12, 2012 15

16. Magnet Yoke Fabrication Yoke Stacking / Bonding Fixture C) Belleville washers are used to apply a constant pressure throughout the bonding cycle D) If top and bottom yoke halves are stacked at the same time using the same fixture – Stacking the laminations in series generally has better results than stacking them side by side E) Registration surfaces must be smooth and coated with a molybdenum based lubricant to minimize frictional forces (Molykote leaves no trace of contamination) Magnet Production Workshop – April 11-12, 2012 16

17. Magnet Yoke Fabrication Yoke Bonding • Optimized bonding conditions (pressure , time and temperature) are paramount in producing strongly bonded yokes • Material manufacturers generally give a broad range for the bonding conditions – The optimized conditions are dependent on the actual yoke size and geometry as well as the method of heating • Optimized conditions are best developed through the use of engineering analysis that take into account the following considerations Magnet Production Workshop – April 11-12, 2012 17

18. Magnet Yoke Fabrication Yoke Bonding Applied Pressure • Stay within the material manufacturer’s recommended range for applied pressure if possible • Pressure measurement film is an accurate and visual representation of the pressure distribution that is being applied to the yoke by the stacking fixture under actual conditions at room temperature • Applied pressure should be maintained for as long as possible during the yoke cool down period Magnet Production Workshop – April 11-12, 2012 18

19. Magnet Yoke Fabrication Yoke Bonding Time and Temperature • Analysis should be performed to determine the heating profile (ramp-up rate, maximum temperature, soak time, and cool-down rate) using the actual geometry and mass of both the yoke plus the stacking fixture • For the most accurate readings – Thermal couples used to monitor the yoke temperature are attached as close as possible to the center of the yoke Magnet Production Workshop – April 11-12, 2012 19

20. Magnet Yoke Fabrication Packing Density • A packing density greater than 98% with less than a 0.2% variation between the top and bottom yokes is required for high precision quality magnets • Magnet asymmetries caused by a variation in packing density between the top & bottom yokes can often cause disturbance to the field as a result of a displacement between the mechanical and magnetic centers Magnet Production Workshop – April 11-12, 2012 20

21. Magnet Coil Fabrication • Vacuum impregnation of the coils and the use of a potting mold was specified in order to accurately produce the coil’s final shape and close mechanical tolerance requirements for • Coil installation onto the poles • Providing the clearance necessary for installation of the vacuum chamber and other components • Solutions to production issues that were encountered during coil fabrication are shown on the next three slides Magnet Production Workshop – April 11-12, 2012 21

22. Magnet Coil Fabrication Coil Preparation Prior to Potting • Preformed G10 reinforcement blocks are used to provide the structural support necessary to strain relieve the conductor leads as they exit the encapsulated coil assembly – The conductor and reinforcement block must be secured to the coil assembly using fiberglass tape • A ground wrap of fiberglass tape is wound around the completed coil assembly securing its shape during potting Magnet Production Workshop – April 11-12, 2012 22

23. Magnet Coil Fabrication Coil Potting Mold • Coat the inside surfaces of the mold cavity with a mold releasing agent to facilitate the removal of the cured coil • G10 strips are used to center the wound coil within the mold allowing the epoxy to flow uniformly around the entire coil assembly • Large molds containing cavities for multiple coils to be potted simultaneously can potentially cause problems trying to fill all of the cavities in the allotted time before the epoxy starts to cure Magnet Production Workshop – April 11-12, 2012 23

24. Magnet Coil Fabrication Coil Potting (Encapsulation) Process Vacuum impregnation of the coils • In order to completely evacuate air from the mold cavity – The vacuum pump draws the mixed epoxy into the cavity from the bottom of the mold – completely fills the cavity – and exists through the top of the mold • Alumina filled epoxy resin prolongs the life of the coils by providing added radiation resistance – Getting the mixture to flow uniformly through the mold cavity proved to be a challenging task for most until the exact recipe (alumina particle size, mixing time and temperature) was established Magnet Production Workshop – April 11-12, 2012 24

25. Magnet Assembly Secondary Processing Small variations during fabrication and assembly have an adverse effect on magnet performance and repeatability. Reducing these variations to an acceptable level requires secondary processing of the magnet after bonding and assembly. Magnet Production Workshop – April 11-12, 2012 25

26. Magnet Assembly Secondary Processing To achieve the high precision quality requirements of the magnetic field and to ensure repeatable magnetic performance after disassembly and reassembly of the magnet • Machine the mating registration surfaces of each yoke half and each mid-plane spacer • Assemble yoke halves using a documented bolt tightening sequence and torque procedure • Best magnetic field quality results are achieved when the pole profile is machined in the assembled magnet Magnet Production Workshop – April 11-12, 2012 26

27. Manufacturing Process Comparison Magnet Production Workshop – April 11-12, 2012 27

28. Acknowledgements THANKS TO THE BNL MAGNET TEAM AND OUR INDUSTRIAL CONTRACTORS AROUND THE WORLD Lessons Learned Workshop, April 11-13, 2012 28