An accurately wound coil is the key component to eliminate transformer failures in the field. Therefore choosing correct mandrel is the first important step in coil winding process. The mandrel design is dependent on shape of the composite part to be produced and removal of the mandrel after curing. In the present paper an empirical study was conducted to study mandrel design and its mechanism. It also includes a thorough investigation of various US patents on expandable and collapsible winding mandrel.

1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 2, February (2014), pp. 143-148, © IAEME
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EXPANDABLE AND COLLAPSIBLE WINDING MANDREL: A
LITERATURE REVIEW
Parth N.Ravala
, Pinank A.Patelb
a
P.G. Student, Mechanical Engineering (CAD/CAM), MEFGI, Rajkot-360003, India.
b
Associate Professor & HOD,Mechanical Engg. Dept., MEFGI, Rajkot-360003, India.
ABSTRACT
An accurately wound coil is the key component to eliminate transformer failures in the field.
Therefore choosing correct mandrel is the first important step in coil winding process. The mandrel
design is dependent on shape of the composite part to be produced and removal of the mandrel after
curing. In the present paper an empirical study was conducted to study mandrel design and its
mechanism. It also includes a thorough investigation of various US patents on expandable and
collapsible winding mandrel. Total 14 US patents were examined to furnish this review paper. This
literature review will be used to change the design of the winding mandrel for better finishing of
winding process.
Keywords: Winding Mandrel; Expandable Mandrel; Collapsible Mandrel.
1. INTRODUCTION
A mandrel is the original from which a replica is electroformed. Mandrels can be machined
out of metals such as steel, copper and aluminium or produced out of non-conductors such as plastics
or silicon. Mandrel type and material selection are crucial in such a case with respect to ease of
mandrel removal. A mandrel must not deflect during winding due to its own weight and fibre
tension. It should also be able to withstand the elevated temperatures during the curing process.
Today the demand for adjustable mandrel has surpassed the demand for fixed type winding mandrel.
The fixed type mandrels make coil removal difficult and often cause damage to coils during removal.
In the simplest form of winding, the mandrel rotates on a spindle around a horizontal axis, while a
carriage moves backward and forward horizontally, lying down fibres in the desired pattern. Once
the mandrel is completely covered to the desired thickness, the mandrel might be placed in an oven
to solidify (cure) the resin. Once the resin is cured, the mandrel is often removed, leaving a hollow
final product.
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There are mainly two types of winding mandrel for the transformer manufacturing process; i.
Expandable type mandrel and ii. Collapsible type mandrel. The expandable winding mandrels are
those which are expanded before the winding process to get the required diameter of the winding.
Once the winding is completed, the winding diameter is reduced and the finished coil is taken out of
the mandrel. Thus connecting rods are used inside the body of the mandrel to expand it. On the other
end, the collapsible winding mandrels are those on which the winding process is done and on
completion of the winding process, the diameter of the mandrel is reduced (Collapsed). This makes
ease to the finished coil to be taken out from the mandrel. Various winding mandrels are designed as
per their application/ requirement but the basic composition consist of the following parts:
1. Lower dividing plate — guiding for the supporting bar and transmit the load. The horizontal
lifting hole is on it and guide screw transmission mechanism used for drive the expansion and
contraction of the mandrel is inside it.
2. Winding baffle — base plane for making the windings.
3. Supporting bar — for load the winding.
4. Upper dividing plate — guiding for the supporting bar and transmit the load. The horizontal
lifting hole is on it.
5. Lifting shaft — welded to the upper dividing plate and used for turn-over & vertical lifting of the
mandrel.
6. Base for vertical winding machine — connected to the lower dividing plate, used to connect to
the vertical winding machine or for conveniently storage.
2. LITERATURE REVIEW
The literature review is a general method to analyze different aspects of the topic. This paper
follows the following steps:
Step 1: Literature review of Winding Mandrel (Expandable and Collapsible type)
Step 2: Develop a classification framework to summarize the review
Step 3: Analyze the review and Conclusion
Step 1: Literature review of Winding Mandrel (Expandable type and Collapsible type)
In past, there was less research and articles available on winding mandrel as the industries or
small companies have manufactured the mandrels as per their requirement and there is no standard
for it; Mandrels were designed as per the requirement. To accomplish this review, the consultation of
a number of patents on expandable and collapsible mandrels used for winding purpose. Patents are
used because they are the most authentic resources which can be used to acquire information and
report new findings. Literature is searched from 14 patents of United States Patent Office.

3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
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Mandrels are either expandable or re-usable. Expandable mandrels are destroyed during
separation of the winding. This approach is commonly used when the mandrel has features
preventing it from being mechanically separated from the winding.
Van Cole et al., 1953) suggested an expandable mandrel comprising a cylindrical body
having spaced apertures therein and a central longitudinal bore, a shaft having spaced annular
grooves and rotatably located in said bore. The said shaft being threaded at one end and in threaded
engagement with a threaded portion of said cylindrical body, a plurality of pins with inlarged head
portions at the extremities thereof and extending through axially aligned counter-bored keyhole slots
in said body. The head portions of the pins resting in said annular grooves in one axial position of the
shaft to provide a mandrel of reduced diameter and, on said shaft being moved by screw means into
another axial position, being forced radially outwards by inclined surfaces on the ends of the grooves
to provide a mandrel of enlarged diameter.
(Mehlum C., 1914) formulated that in a mandrel, a collapsible cylinder and a shaft whose
axis is concentric with said cylinder, bearings for same shaft in which the shaft is movable
longitudinally, link connections between shaft and cylinder, and means for causing a longitudinal
movement of the shaft with relation to the cylinder whereby through the said link connections the
cylinder is collapsed.
(Gerstein D. et al., 1966) stated that a feature of his invention resides in the provision that
the mandrel can be readily expanded and contracted in a radial direction relative to the axis of the
shaft in a uniform manner along the entire length thereof so as to accommodate a variety of
differentially sized tubular stock material and it also provides a positive means for limiting the
maximum expanded position of the mandrel.
(Plach E., 1978) suggested an expandable chuck which can be used singly with a dummy
support at the other end of a core where only low torques are required or, alternatively, a pair of such
expandable chucks may be provided, one at each end of the core, where greater torque capability is
required. While the chuck disclosed in intended for use with hollow cores for web winding it will be
apparent that it may have additional applications. It can be used to rotate pipe or other hollow tubular
members and conceivably could be employed as part of a power train arrangement for transmitting
rotary motion.
(Hausner G, 1988) showed that according o his invention each of the gripping members is
pivotally mounted on a respective pivot axis supported in a bearing member of the expandable
winding mandrel running transverse to the longitudinal axis of the expandable winding mandrel
which has advantage that the winding supports are gripped by the gripping members correctly even
when the winding supports or yarn holders are not entirely cylindrical and even when they do not
have a stable shape.
(Williams L, 1989) concluded that the expandable mandrel is directed towards providing an
improved apparatus for being inserted between a mandrel and the eye of a coil of strip material to act
as a spacer between the mandrel and the eye of the coil. This concept is to provide a plurality of
elongated, rigid beam members, each of the beam members having at least one transverse aperture
therethrough; and elastic means extending through the transverse apertures of the beam members for
joining the beam members to one another to form an expandable sleeve for being inserted over the
outer circumference of the mandrel and for being inserted into the eye of the coil of strip material.
(Lockwood E., 1915) described that in a device, an arbor having a polygonal shaped portion,
a pair of links for each side of links for each side of said portion and pivoted thereto, bars pivoted
respectively to each pair of links, a head secured to said arbor at one end and forming an abutment to
limit the movement of said bars in one direction, said head having an aperture portion to receive a
centering device and also having a polygonal shape adapted to fit a socket of corresponding shape in
a driving member, a collar slidingly mounted on the opposite end of said arbor and adapted to engage
the adjacent ends of said bars, and means to lock said collar in a position said collar maintains said

4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
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bars properly positioned to form a winding mandrel, and in another position releases said bars to
form a collapsed mandrel.
(Nystrand E., 1966) described a mandrel body having a plurality of longitudinally extending
recesses. Each recess receives a locking bar which is connected to the mandrel body by links and
which is adapted for upward longitudinal pivotal movement with respect to the mandrel body to
engage a core ensleeved on the mandrel body. The locking bars are maintained in the down or
unlocked position by springs and may be urged upwardly by a screw threadedly received in one end
of the mandrel body. The links are pivotally secured to the mandrel body by pins which are received
in bores extending through the mandrel body.
(Bessems et al., 2006) concluded a winding core capable of being made in relatively thick-
walled configurations and yet capable of being readily collapsed into a flattened configuration for
shipping or storage prior to use comprises a plurality of fibrous plies helically wound one atop
another and adhered together to form a tube. The plies are arranged in two or more groups of two or
more plies each. The plies of each group are adhered to one another over at least a substantial
majority of their facing surfaces, but the adjacent groups are non-adhered to each other over at least a
substantial majority of their facing surfaces.
(Zajac et al., 1983) showed both method and apparatus for compressing the ends of universal
type windings and more particularly to such method and apparatus in which the ends of the winding
may be compresses on a specially adapted spindle having endforms adapted to receive the
application of pressure on the ends of the windings which also results in a commensurate collapse of
the mandrel upon application of the compression force.
Step 2: Develop a classification framework to summarize the review
Table1 illustrates the classification scheme for the literature on winding mandrel. The search
process was focused on research papers, books, journals and patents from reliable sources. The total
number of patents found is 14. Table1 illustrates the division of literature as found in various patents.
Table 1. Classification of Winding mandrel literature
Title of the Patent & Year Expandable type Collapsible type
Expandable mandrel for use on winding machine,
1955
Yes
Expandable mandrel, 1962 Yes
Collapsible mandrel, 1914
Expandable mandrel, 1966
Expandable chuck for winding web material on a
core, 1978
Collapsible mandrel, 1915
Expandable mandrel, 1994
Two way collapsible mandrel with winding
compression, 1983
Expandable winding mandrel for retaining a
substantially cylindrical yarn holder of a spinning
or twisting machine, 1988
Collapsible winding core and method of making
same, 2006
Apparatus for being positioned on an expandable
mandrel, 1989
Expandable mandrel core, 2000
Implant delivery assembly with expandable
coupling/ decoupling mechanism, 2001
Web winding mandrel, 1967
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes

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Step 3: Analyze the review and Conclusion
On analyzing the whole review it is clear that a lot of work already has been done on winding
mandrel and its improvements. Winding mandrel design if improved properly can help in both
mechanically as well as electrically and a drastic savings can be achieved.
3. CONCLUSION
The literature review of patents on winding mandrel reveals that winding mandrels should be
firm enough to liberate the finished coils without damaging it. Simple gear mechanism or any other
suitable mechanism is used to expand and collapse the mandrels. This paper also draws an attention
towards conceptual design of the winding mandrel and its variation of design. As a part of the future
work, authors are interested in changing the design of the circular type expandable mandrel into
elliptical type expandable mandrel which will reduce 15% outer tank size of the transformer. It has
its other electrical advantages also which add more value to this project. The relative advantages of
design change is summarized in the table below:
Change
Parameter
Cylindrical Mandrel Elliptical Mandrel Change Effect
Diameter of
mandrel
Major-Minor axis same Major-Minor axis
different
Reduced transformer
size
Mechanism of
mandrel
Gear Mechanism Gear Mechanism No change
Mechanism
design
Mounted on circular type
shaft
Mounted on elliptical
type shaft
Speed change
Wooden frame Same dimension for all
wooden frames
Different dimensions for
each wooden frame
Need to design it as
per requirement
Angle between
wooden frames
Same angle (30) between
all wooden frames
Different angle between
all wooden frames
Need to design
carefully (More
calculation needed)
Overall change Existing design Proposed design 15% reduction in tank
size,
Reduced transformer
size,
Less winding work
needed,
Other electrical
advantages
ACKNOWLEDGEMENTS
I would like to express my deep gratitude to Prof. Pinank A. Patel, Associate Professor &
Head of Department, Marwadi Education Foundation Group of Institutions, Rajkot who provide his
valuable time and support me to conclude this review paper.
REFERENCES
[1] Victor George Van Colle, Hale, and Thomas Fishwick, 1955. “Expandable Mandrel for use
on winding machines” United States Patent Office 2727700, filed March 18, 1953 and issued
Dec. 20, 1955 (Patent).
[2] Ingham S. Roberts, Ridley Park, 1962 “Expandable Mandrel” United States Patent Office
3052420, filed Mar. 9, 1961 and issued Sept.4, 1962 (Patent).

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[3] David E. Gerstein, Leonard Krautheim, Haledon, William Orr, Hohokus, John D. Alexander,
Hawthorne, 1966 “Expandable Mandrel” United States Patent Office 3248976, filed Nov. 13,
1963 and issued May 3, 1966 (Patent).
[4] Edward F. Plach, 1978 “Expandable chuck for winding web material on a core” United
States Patent Office 4079896, filed Nov. 18, 1976 and issued Mar. 21, 1978 (Patent).
[5] Albert W. Forest, Jr., Mark R. Jones, 1994 “Expandable mandrel” United States Patent
Office 5314135, filed Aug. 12, 1991 and issued May 24, 1994 (Patent).
[6] Gerhard Hausner, 1988 “Expandable winding mandrel for retaining a substantially
cylindrical yarn holder of a spinning or twisting machine” United States Patent Office
4763850, filed Jun. 4, 1987 and issued Aug. 16, 1988 (Patent).
[7] Logan D. Williams, 1989 “Apparatus for being positioned on an expandable mandrel”
United States Patent Office 4802637, filed Apr. 22, 1988 and issued Feb. 7, 1989 (Patent).
[8] Thomas J. Wente, Andrew J. Prenger, 2000 “Expandable mandrel core” United States Patent
Office 6119974, filed Aug. 12, 1998 and issued Sep. 19, 2000 (Patent).
[9] Ivan Sepetka, U. Hiram Chee, 2001 “Implant delivery assembly with expandable coupling/
decoupling mechanism” United States Patent Office US 6238415 B1, filed Mar. 3, 1998 and
issued May 29, 2001 (Patent).
[10] Casper Mehlum, 1914 “Collapsible mandrel” United States Patent Office 1093284, filed
March 3, 1913 and issued Apr. 14, 1914 (Patent).
[11] Edward M. Lockwood, Assignor, 1915 “Collapsible mandrel” United States Patent Office
1138675, filed July 17, 1914 and issued May 11, 1915 (Patent).
[12] Ronald E. Zajac, 1983 “Two way collapsible mandrel with winding compression” United
States Patent Office 4377262, filed Mar. 9, 1981 and issued Mar. 22, 1983 (Patent).
[13] Ernst Daniel Nystrand, 1967 “Web winding mandrel” United States Patent Office 3341147,
filed Apr. 25, 1966 and issued Sep. 12, 1967 (Patent).
[14] Nico J.C. Bessems, Emile Henricus Lutgens, Ed Spronk, Johannes W. van de Camp, John
Whitehead, 2006 “Collapsible winding core and method of making same” United States
Patent Office US 2006/0151663 A1, filed Aug. 23, 2004 and issued Jul. 13, 2006 (Patent).
[15] Prof. Pinank A. Patel, Vivek G. Patel and Dr. Shashikant S. Khandare, “Comparative Study
of Sae 1045 (Carbon Steel) and Aluminium Alloy 7075-T6 for Lower Suspension Arm of a
Sedan Car”, International Journal of Mechanical Engineering & Technology (IJMET),
Volume 4, Issue 2, 2013, pp. 119 - 124, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.