endless possibilities: understanding the expanding world of machined springs
DESCRIPTION
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 systemTRANSCRIPT
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
Moderator
Miles BudimirDesign World
Presenter
Gary BoehmHelical
Understanding the
Expanding World of
Machined Springs
4© 2013 Helical Products Co, Inc.
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.
Helical Products Company• Founded in 1958• Invented Beam
Style Couplings Shown here
6© 2013 Helical Products Co, Inc.
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Wire-Wound Springs
Springs
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Wire-Wound Springs
Machined Springs
Springs
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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
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Performance PrecisionDimension Precision
Wire Wound
Springs
Machined
Springs
Precision
10% yes yes
1% maybe yes
0.1% no maybe
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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)
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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.
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Machined Spring’s Advantageof Custom Attachments
Some of the many Machined Spring
Attachments available for
Compression and Extension
Springs
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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
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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
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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.
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.
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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.
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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.
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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.
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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.
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Number of StartsTriple
Available only in Machined Springs
DoubleAvailable only in Machined Springs
SingleAvailable in both
Wireand
Machined Springs
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Single Start Multiple Start
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Torsion Machined Spring’s Advantage of Custom Attachments
Some of the many Machined Spring
Attachments available for
Torsion Springs
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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
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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.
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www.heli-cal.com
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Thank you for sharing your time with us…
And now…Does anyone have a question?
© 2013 Helical Products Co, Inc.
Questions?
Design WorldMiles [email protected]: 440.234.4531Twitter: @DW_Motion
HelicalGary [email protected]: 805.928.3851Twitter: @HelicalProducts
Thank You This webinar will be available at designworldonline.com
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