endless possibilities: understanding the expanding world of machined springs

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Endless Possibilities: Understanding the Expanding World of Machined Springs

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This webinar addresses the high points of the original Choosing Between Machined and Wire Wound Springs webinar, and then goes into more detail regarding the unique differences that can significantly affect design considerations. In particular, issues regarding coil and slot geometries plus length limitations will be discussed. The topic of Multiple Starts and why these are becoming more important in many modern spring applications will be viewed from both the performance and cost vantage points. Torsion springs will be revisited with examples of moment computations. The discussion will conclude with examples of springs in dynamic, resonant usage. Attended this webinar to learn: • Differences in spring coil geometries revealed • Design considerations: differences of machined springs vs wire wound springs • Insights into torsional spring attachments • Single Degree of Freedom spring-mass functioning system

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Page 1: Endless Possibilities: Understanding the Expanding World of Machined Springs

Endless Possibilities:Understanding the Expanding World of

Machined Springs

Page 2: Endless Possibilities: Understanding the Expanding World of Machined Springs

This webinar will be available afterwards at designworldonline.com & email

Q&A at the end of the presentation

Hashtag for this webinar: #DWwebinar

Before We Start

Page 3: Endless Possibilities: Understanding the Expanding World of Machined Springs

Moderator

Miles BudimirDesign World

Presenter

Gary BoehmHelical

Page 4: Endless Possibilities: Understanding the Expanding World of Machined Springs

Understanding the

Expanding World of

Machined Springs

4© 2013 Helical Products Co, Inc.

Page 5: Endless Possibilities: Understanding the Expanding World of Machined Springs

A Webinar based upon the Helical White Paper

Wire Springs versus Machined Springs,

A ComparisonAuthored by

Gary L Boehm PE

Helical Products Co Inc, Santa Maria, CA

5© 2013 Helical Products Co, Inc.

Page 6: Endless Possibilities: Understanding the Expanding World of Machined Springs

Helical Products Company• Founded in 1958• Invented Beam

Style Couplings Shown here

6© 2013 Helical Products Co, Inc.

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© 2013 Helical Products Co, Inc. 7

Wire-Wound Springs

Springs

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Wire-Wound Springs

Machined Springs

Springs

© 2013 Helical Products Co, Inc.

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Background• 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

© 2013 Helical Products Co, Inc.

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Performance PrecisionDimension Precision

Wire Wound

Springs

Machined

Springs

Precision

10% yes yes

1% maybe yes

0.1% no maybe

© 2013 Helical Products Co, Inc.

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Machined Spring MaterialsWire 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 strengtha 17-4PH per AMS 5643b 15-5PH per AMS 5659c CC455 per AMS5617d X750 Inconel per AMS 5667 and 5670 Very high strength steela C300 per AMS6514 Other materials of interesta 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)

© 2013 Helical Products Co, Inc.

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Machined Spring Sizes

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.

© 2013 Helical Products Co, Inc.

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Machined Spring’s Advantageof Custom Attachments

Some of the many Machined Spring

Attachments available for

Compression and Extension

Springs

© 2013 Helical Products Co, Inc.

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Coils and Slots of Wire and

Machined SpringsFeature Section

Wire WoundSprings

MachinedSprings

Coils

Round yes noSquare yes yesRectangular, radial yes yesRectangular, radialwith high ratio no yes

Rectangular, longitudinal yes yesRectangular, longitudinalwith high ratio yes yes

Slots

Zero width yesyes, withspecial process

Zero width w/prestress yes no0.100 inch yes yesOver 0.250 inch yes maybe

Numberof

coils

1 coil minimum yes yes20 coils yes yes50 coils yes maybe

© 2013 Helical Products Co, Inc.

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Wire Spring Slots tend to be wider than those on

Machined Springs

Percentage of Compression

based upon Free Length

Wire WoundSprings

MachinedSprings

10% yes yes20% yes yes30% yes yes40% yes yes50% yes maybe60% yes maybe

70% maybe no80% maybe no90% no no

© 2013 Helical Products Co, Inc.

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Equivalent Machined Springs

Must be longer• 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.

© 2013 Helical Products Co, Inc.

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Equivalent Machined Springs

Must be longer• 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.

17© 2013 Helical Products Co, Inc.

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Cost DifferencesProduction 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.

© 2013 Helical Products Co, Inc.

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Metal Improvement for Spring

Materials

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.

© 2013 Helical Products Co, Inc.

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Plating of SpringsWire 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.

© 2013 Helical Products Co, Inc.

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Machined Spring’s Advantage

of No RotationFlexure configurations for

Compression and Extension Springs that resist rotation given axial deformation.

These techniques are difficult, but not exclusively unavailable for wire springs.

© 2013 Helical Products Co, Inc.

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Number of StartsTriple

Available only in Machined Springs

DoubleAvailable only in Machined Springs

SingleAvailable in both

Wireand

Machined Springs

© 2013 Helical Products Co, Inc.

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Single Start Multiple Start

© 2013 Helical Products Co, Inc.

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© 2013 Helical Products Co, Inc.

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Torsion Machined Spring’s Advantage of Custom Attachments

Some of the many Machined Spring

Attachments available for

Torsion Springs

© 2013 Helical Products Co, Inc.

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Torsional SpringsAttachment

TypeWire Spring Machined

SpringTang (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

© 2013 Helical Products Co, Inc.

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Resonance Ready SpringsMultiple 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.

© 2013 Helical Products Co, Inc.

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www.heli-cal.com

© 2013 Helical Products Co, Inc.

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Thank you for sharing your time with us…

And now…Does anyone have a question?

© 2013 Helical Products Co, Inc.

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Questions?

Design WorldMiles [email protected]: 440.234.4531Twitter: @DW_Motion

HelicalGary [email protected]: 805.928.3851Twitter: @HelicalProducts

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Thank You This webinar will be available at designworldonline.com

& email

Tweet with hashtag #DWwebinar

Connect with

Discuss this on EngineeringExchange.com

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