1. Important Considerations to
Consider When Designing a
Custom Spring

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. Presenter
Gary L. Boehm
Helical Products Co.
Moderator
Mary Gannon
Design World

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. • Founded in 1958
• Invented Beam Style
Couplings
Shown here
© 2014 Helical Products Co, Inc. 5

6. Wire-Wound
Springs
© 2014 Helical Products Co, Inc. 6
Springs

7. Wire-Wound
Springs
© 2014 Helical Products Co, Inc. 7
Machined Springs
Springs

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. Wire Wound
Springs
Machined
Springs
Precision
10% yes yes
1% maybe yes
0.1% no maybe
© 2014 Helical Products Co, Inc. 9

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. © 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. Some of the many
Machined Spring
Attachments
available for
Compression and
Extension Springs
© 2014 Helical Products Co, Inc. 11

13. Some of the many
Machined Spring
Attachments
available for Torsion
Springs
© 2014 Helical Products Co, Inc. 13

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. © 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. 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. 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. 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. 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. 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. 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. © 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. © 2014 Helical Products Co, Inc. 23
Single Start Multiple Start

24. © 2014 Helical Products Co, Inc. 24

25. Some of the many
Machined Spring
Attachments
available for Torsion
Springs
© 2014 Helical Products Co, Inc. 25

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. 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. © 2014 Helical Products Co, Inc.
28
www.heli-cal.com

29. Thank you for sharing your time with us…
And now…
Does anyone have a question?
© 2014 Helical Products Co, Inc. 29

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. Thank You
This webinar will be available at designworldonline.com
& email
Tweet with hashtag #DWwebinar
Connect with Design World
Discuss this on EngineeringExchange.com