Post on 15-Jul-2015
Important Considerations to
Consider When Designing a
Custom Spring
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
Presenter
Gary L. BoehmHelical Products Co.
Moderator
Mary GannonDesign World
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
© 2014 Helical Products Co, Inc. 4
• Founded in 1958
• Invented Beam Style
Couplings
Shown here
© 2014 Helical Products Co, Inc. 5
Wire-WoundSprings
© 2014 Helical Products Co, Inc. 6
Springs
Wire-WoundSprings
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Machined Springs
Springs
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• 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
Wire Wound
Springs
Machined
Springs
Precision
10% yes yes
1% maybe yes
0.1% no maybe
© 2014 Helical Products Co, Inc. 9
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)
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0
© 2014 Helical Products Co, Inc. 1
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.
Some of the many
Machined Spring
Attachments
available for
Compression and
Extension Springs
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Some of the many
Machined Spring
Attachments
available for Torsion
Springs
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Feature SectionWire Wound
Springs
Machined
Springs
Coils
Round yes no
Square yes yes
Rectangular, radial yes yes
Rectangular, radial
with high rationo yes
Rectangular, longitudinal yes yes
Rectangular, longitudinal
with high ratioyes 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
© 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
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
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
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
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
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
Flexure 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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TripleAvailable only in
Machined Springs
DoubleAvailable only in
Machined Springs
SingleAvailable in both
Wire
and
Machined Springs
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Single Start Multiple Start
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Some of the many
Machined Spring
Attachments
available for Torsion
Springs
© 2014 Helical Products Co, Inc. 25
© 2014 Helical Products Co, Inc. 26
AttachmentType
Wire Spring
MachinedSpring
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
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
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www.heli-cal.com
Thank you for sharing your time with us…
And now…
Does anyone have a question?
© 2014 Helical Products Co, Inc. 29
Questions?
Mary GannonDesign WorldMGannon@wtwhmedia.com
Phone: 440.234.4531
Twitter: @DW_MaryGannon
Gary L. BoehmHelical Products Co.machinedsprings@heli-cal.com
Phone: 877-353-9873
Thank You
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