Important Considerations When Designing a Custom Spring

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Important Considerations When Designing a Custom Spring

  1. 1. Important Considerations to Consider When Designing a Custom Spring
  2. 2. This webinar will be available afterwards at www.designworldonline.com & email Q&A at the end of the presentation Hashtag for this webinar: #DWwebinar Before We Start
  3. 3. Presenter Gary L. Boehm Helical Products Co. Moderator Mary Gannon Design World
  4. 4. A Webinar based upon the Helical White Paper Wire Springs versus Machined Springs, A Comparison Authored by Gary L Boehm PE Helical Products Co Inc, Santa Maria, CA © 2014 Helical Products Co, Inc. 4
  5. 5. • Founded in 1958 • Invented Beam Style Couplings Shown here © 2014 Helical Products Co, Inc. 5
  6. 6. Wire-Wound Springs © 2014 Helical Products Co, Inc. 6 Springs
  7. 7. Wire-Wound Springs © 2014 Helical Products Co, Inc. 7 Machined Springs Springs
  8. 8. © 2014 Helical Products Co, Inc. 8 • Wire Springs existed before the Industrial Revolution • First Machined Springs in 1960’s • Now- New designs created daily • Both are manufactured with CNC controlled machines
  9. 9. Wire Wound Springs Machined Springs Precision 10% yes yes 1% maybe yes 0.1% no maybe © 2014 Helical Products Co, Inc. 9
  10. 10. Wire Wound Springs are typically made from medium and high strength steels, nickel alloys, titanium and stainless steels that gain their strength predominately from heat treating and cold reduction. CRES (Corrosion Resistant Steels), moderate to high strength a 17-4PH per AMS 5643 b 15-5PH per AMS 5659 c CC455 per AMS5617 d X750 Inconel per AMS 5667 and 5670 Very high strength steel a C300 per AMS6514 Other materials of interest a 7075-T6 Aluminum (high strength) b 7068-T6511 Aluminum (very high strength) c 38644 Beta C Titanium (very high strength and corrosion resistant) d Delrin 100 (machinable plastic) e Ultem 2300 (machinable plastic) © 2014 Helical Products Co, Inc. 1
  11. 11. © 2014 Helical Products Co, Inc. 1 A long, torsion Machined Spring using a dime for size comparison. Wire Springs can be larger. A small, compression Machined Spring. Wire Springs can be smaller.
  12. 12. Some of the many Machined Spring Attachments available for Compression and Extension Springs © 2014 Helical Products Co, Inc. 11
  13. 13. Some of the many Machined Spring Attachments available for Torsion Springs © 2014 Helical Products Co, Inc. 13
  14. 14. © 2014 Helical Products Co, Inc. 14 Feature Section Wire Wound Springs Machined Springs Coils Round yes no Square yes yes Rectangular, radial yes yes Rectangular, radial with high ratio no yes Rectangular, longitudinal yes yes Rectangular, longitudinal with high ratio yes yes Slots Zero width yes yes, with special process Zero width w/prestress yes no 0.100 inch yes yes Over 0.250 inch yes maybe Number of coils 1 coil minimum yes yes 20 coils yes yes 50 coils yes maybe
  15. 15. © 2014 Helical Products Co, Inc. 15 Percentage of Compression based upon Free Length Wire Wound Springs Machined Springs 10% yes yes 20% yes yes 30% yes yes 40% yes yes 50% yes maybe 60% yes maybe 70% maybe no 80% maybe no 90% no no
  16. 16. In a closed-ground wire compression spring, the active coil (that in which strain energy can be stored) extends to the very end of the spring. © 2014 Helical Products Co, Inc. 16
  17. 17. In a Machined, Compression Spring, the active spring coil stops short of the spring end relegating at each end one slot width and one structural width unavailable for storing energy. © 2014 Helical Products Co, Inc. 17
  18. 18. Production time is the major influence in cost. Cost wise, Wire Wound Springs benefit greatly from short production times. Machined Springs cannot approach the low cost of wire product. It would be very surprising to find a very simple and inexpensive Machined Spring, produced in high quantities costing less than $1 USD each. However, these value enhancements related to Machined Springs usage helps to validate their usage: • Integrated attachments • Enhanced performance or functionality • Via Multiple Starts, more uniform elastic reactions, and better control of internal moments • Higher precision • Reduced assembly and acquisition efforts • No sound creation from coil contacts • No debris created by coil contacts Without one or more of these benefits being present, there is usually little justification of employing Machined Springs in place of Wire Springs. © 2014 Helical Products Co, Inc. 18
  19. 19. Wire Springs Machined Springs Wire Springs are often shot peened for enhanced fatigue resistance. This process is possible because the gap between the coils is typically wide enough to permit passage of shot that can condition the inside of the opposite coil, as well as the outside of the coils. Machined Springs typically have coil slots that are too small for the passage of shot. Hence, shot peening is not common. To insure fatigue resistance, features such as stress relief holes and slots can be added to the slot ends. Selecting high strength, fatigue resistant, materials is also a significant benefit. © 2014 Helical Products Co, Inc. 19
  20. 20. Wire Springs Machined Springs It is not uncommon to plate Wire Springs with materials such as zinc and nickel for corrosion protection. Plating Machined Springs is uncommon because of the existence of sharp edge corners that typically receive insufficient coverage. The use of CRES and titanium materials provides excellent corrosion protection for most Machined Spring applications. Machined Springs made form aluminum are typically anodized or coated to prevent corrosion. © 2014 Helical Products Co, Inc. 20
  21. 21. Flexure configurations for Compression and Extension Springs that resist rotation given axial deformation. These techniques are difficult, but not exclusively unavailable for wire springs. © 2014 Helical Products Co, Inc. 21
  22. 22. © 2014 Helical Products Co, Inc. 22 Triple Available only in Machined Springs Double Available only in Machined Springs Single Available in both Wire and Machined Springs
  23. 23. © 2014 Helical Products Co, Inc. 23 Single Start Multiple Start
  24. 24. © 2014 Helical Products Co, Inc. 24
  25. 25. Some of the many Machined Spring Attachments available for Torsion Springs © 2014 Helical Products Co, Inc. 25
  26. 26. © 2014 Helical Products Co, Inc. 26 Attachment Type Wire Spring Machined Spring Tang (Radial) External and Internal yes* yes* Dual Tang (Radial) External and Internal no yes** Tang (Axial) External and Internal yes* yes* Dual Tang (Axial) External and Internal no yes** Dual Pin Holes (Axial) no yes** Geometric ID Shapes (square, hex, etc) no yes** *Force at distance requiring force resolution **Pure moment drive
  27. 27. Multiple Start Machined Springs have a history of providing effective Single Degree of Freedom elastic elements for such systems. Double Start Springs set the baseline for such usage, but Triple Start Springs are the gold standard because of their uniform stiffness in all lateral directions. © 2014 Helical Products Co, Inc. 27
  28. 28. © 2014 Helical Products Co, Inc. 28 www.heli-cal.com
  29. 29. Thank you for sharing your time with us… And now… Does anyone have a question? © 2014 Helical Products Co, Inc. 29
  30. 30. Questions? Mary Gannon Design World MGannon@wtwhmedia.com Phone: 440.234.4531 Twitter: @DW_MaryGannon Gary L. Boehm Helical Products Co. machinedsprings@heli-cal.com Phone: 877-353-9873
  31. 31. Thank You This webinar will be available at designworldonline.com & email Tweet with hashtag #DWwebinar Connect with Design World Discuss this on EngineeringExchange.com

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