2. If you are the kind of reader who
just homes in on one article, we’d
like to challenge you to read the
others as well. It may seem at first
glance that there is little relevance to
your project or industry. However,
what we continually find is that
some of the best products , as well as
the most apparently novel designs,
are a direct result of taking ideas
from one industry and transplanting
them into another, sometimes with
just a small tweak to make them fit perfectly. Inside DuPont
we call this “industrial cross-fertilization.” Each industry has
different ideas, needs and applications for the use of raw
materials, but those same ideas and solutions often have so
much broader potential which can often go unnoticed. Our
own engineers and development support team are doing just
this – working with customers in many different fields and
applying technologies or solutions from one industry to
bring advantages to another.
Take some of the stories in this issue of Engineering Design,
for example. The Onzo Smart Energy Kit and the Autopen 2
both use DuPont™ Delrin® acetal resin for small mechanisms –
the characteristics of Delrin® homopolymer give it significant
advantages over copolymer, or any other polymer for that
matter. When molded into small components, it provides
reliable mechanical performance – spring performance and
creep resistance, low wear and low friction, quiet operation,
precision and strength all in the smallest space possible. It’s
all the kind of stuff that the consumer expects performance-
wise, but equally doesn’t want to have to think about. Relia-
bility should be a given. Make the parts a bit bigger and they
have the same reliable, accurate, low friction performance in
the large molded bearings you will read about in the photo-
voltaic bearing article.
As for another example, take the use of DuPont™ Zytel®
HTN high performance polyamide in laptop covers. It
replaces PC/ABS blends where a step change in perform-
ance is required. Unsurprisingly, the underlying require-
ments are familiar to many different industries – higher
strength, higher stiffness, and lower weight to meet the
demands of the next generation of product.
So, in short, as you read through the magazine, we’d like to
challenge you to read the articles in a new light. How can
the solutions you see in these different industries be applied
to your own industry and design problem? We’d also be
very happy if we could work together with you on some of
your challenges – by “cross fertilizing” the solutions we see
from other industries to help solve your design and develop-
ment material requirements.
You can reach us on: plastics@dupont.com
WHERE ARE THE DESIGN ANSWERS?
BY MARK YOUNG, EUROPEAN MANAGER FOR INDUSTRIAL, CONSUMER AND
ENERGY APPLICATIONS
Many times we ask ourselves how you, our customers, industry engineers, designers and managers, read
Engineering Design magazine. Feedback we receive reassures us that it is appreciated, and read by a broad cross
section of the engineering and design community. Yet we suspect it is valued very differently at an individual
level – sometimes read in chunks during coffee breaks, sometimes from cover to cover, or sometimes it may just
be a specific article that grabs your attention with the hope of providing a solution to your real and current
design challenges.
Mark Young
• DuPont™ Delrin® in the Onzo Smart Energy Kit
(page 3)
• DuPont™ Delrin in the Autopen® insulin delivery
device (page 4)
• DuPont™ Zytel® HTN in handheld devices (page 6)
• DuPont™ Delrin® in drivetrain transmission systems
(page 8)
• DuPont™ Zytel® in the SonarBell® sonar responder
(page 9)
• DuPont™ Hytrel® and DuPont™ Crastin® in the Generation by
Knoll® work chair (page 10)
• DuPont™ Zytel® and DuPont™ Delrin® in photovoltaic
applications (page 11)
PAGE 2
THISISSUEATAGLANCE
3. The Onzo Smart Energy Kit is designed to put households
in control of their energy use. It gives consumers real-time
information about how much electricity they are using in
their home and how much it is costing. By delivering action-
able information that is easy to understand it helps them to
learn how to manage their consumption, saving both energy
and money.
It works in three simple steps: 1) the sensor clips onto the
live wire of the electricity meter, 2) it sends the amount of
electricity being used in the home wirelessly to the display,
3) the display is connected to a computer to upload data, via
USB, to a personalized website.
The display shows users how much energy their home is
using in real time, as well as contextualizing this informa-
tion with targets and tools that help consumers understand
their usage at a glance. The website allows users to dig
deeper into how they use electricity and learn how they can
reduce or change their consumption over time.
It’s as part of the sensor’s unique clamp design that compo-
nents molded from Delrin® acetal resin play an integral role
in its attachment to the electricity meter and its ability to
accurately read energy consumption. “The gray clip is fun-
damental to the simple and easy-to-use lock and release
mechanism, which we purposely designed for single-handed
use,” explains Jeremy Stimson, product design manager at
Onzo Ltd, “while the spring inner ensures the constant con-
tact between the two sections of the current transformer,
the component that senses electricity consumption and con-
verts it to a digital signal, which fits tightly around the elec-
tricity cable.” Indeed, it is the ability of the Delrin®
spring to generate a con-
sistently reliable force
on the current trans-
former over
time that is key
to the long-term
accuracy of the
sensor. “DuPont
produced a stress analysis of the spring mechanism which
showed that Delrin® acetal is able to outperform its competi-
tors in terms of resistance to creep and stress relaxation,
thereby extending the clamping force for this particular
application,” confirms Stimson.
A further quality of the Delrin® spring is its ability to cater
for variations in size of the current transformer (CT). “The
CT is a rough, metal component with wide tolerances. By
choosing Delrin® we could be sure that there was enough
flexural behavior in the springs to accommodate these dif-
ferences in sizes,” continues Stimson. The integration of
design features such as snap fits, hooks and catches in the
Delrin® components helped Onzo eliminate the use of metal
clips or hinges that would otherwise interfere with the wire-
less communication between the sensor and the display. The
exclusion of metal components also means that the sensor,
as well as the display, can be more easily recycled at the end
of their useful lives.
Launched in the UK in 2009 and a winner of the presti-
gious red dot award in the same year, the Onzo Smart
Energy Kit is available free of charge to Scottish & Southern
Energy (SSE) customers that sign up for its iplan energy
scheme, or can be bought from Amazon in the UK.
A SMART MATERIAL FOR A SMART
DEVICE
BY IAN WANDS AND MARK HAZEL, DUPONT PERFORMANCE POLYMERS UK
DuPont™ Delrin® acetal resin used for key components of the sensor included in the award-winning Onzo Smart
Energy Kit, ensuring high accuracy, reliability and consistent operation.
Onzo Ltd.
6 Great Newport Street, London WC2H 7JB
Tel.: +44 (0) 20 3051 3270
hello@onzo.com, www.onzo.com
CONTACT
PAGE 3
4. Introduced during 2010, the Autopen® 2 constitutes a new
generation of reusable pen injectors launched by Owen
Mumford (Oxfordshire, England) under the Autopen®
trademark that benefit from an automatic delivery system
providing greater patient comfort and control. Its principal
enhancement, beyond the ability to deliver a dose of up to
72 units of insulin in steps of one unit, is the integration of a
patented mechanism that allows the user to correct the dose
if it has been over dialed.
“The original Autopen® incorporated a dose metering
device, provided by a dose knob, that is rotatable to a posi-
tion related to the dose of medication to be injected,”
explains Mark Eaton, product designer at Owen Mumford.
“However once a dose had been set by the user, it could not
be reduced by winding the knob in the reverse direction and
the user had to expel the set dose and redial. The design of
the Autopen® 2 resolves this problem.”
“Essentially a torsion spring is arranged within the housing
to provide the drive force for ejecting medication from the
insulin cartridge,” continues Mark Eaton. “The dose setting
knob is coupled to both the spring and the housing in such
a way that rotation of the knob relative to the housing
results in compression of the spring. When the user applies
a downward force on the trigger at the side of the pen, it
releases the spring and a drive member is driven through the
housing, expelling the required dose of insulin from the car-
tridge. In the event that a user oversets a dose, the button at
the top of the dose setting knob, which is also coupled to
the torsion spring, is used to unwind the spring in discrete
steps with each press of the button.”
Delrin®
key to successful development
The principal components behind the sophisticated mecha-
nism used within the Autopen® 2 are molded from a range
of grades of Delrin®. Required properties of the DuPont
acetal resins include strength and stiffness, dimensional sta-
bility, fatigue resistance, low coefficient of friction and
resistance to wear when used in intricate, geometrically
advanced parts that, in many cases, move against each other
or are required to snap fit together.
For instance the locking bush, which is used to prevent the
rotational movement of the leadscrew until delivery of the
medication is triggered, is molded from a toughened grade
of Delrin® due to the high torsional forces it must withstand,
particularly during dose setting. It comprises a pair of fingers
that engage with a corresponding channel within the lead-
screw to prevent rotation during delivery. They are required
to be flexible enough to flex outwards over ramps on the
leadscrew when it is passed through the centre of the locking
bush before snapping back to engage with the channels.
EFFORTLESS DELIVERY
BY IAN WANDS, EUROPEAN HEALTH CARE SEGMENT LEADER
AT DUPONT PERFORMANCE POLYMERS
Specific grades of DuPont high performance polymers that meet demanding requirements for use in medical
equipment enable the design and manufacture of reliable and durable products. This is illustrated by the recent
launch of the Autopen® 2 insulin delivery device from Owen Mumford. It includes several functional
components made of DuPont™ Delrin® acetal resin that are fundamental to its use for the effortless and accurate
delivery of insulin to diabetes patients.
PAGE 4
5. EFFORTLESS DELIVERY
Alternatively, the dose knob is molded in a laser-markable
grade of Delrin® for incorporation of the insulin measure-
ments. It must also provide a robust surface for two sets of
gear teeth within the part which works with the clutch col-
let and rewind button to allow the spring to unwind (as part
of the dose correction procedure). A further five parts are
molded from Delrin®, including the drive gear, rewind but-
ton, dose knob cover, ratchet drive shaft and cartridge com-
pression cup.
“Of all the plastic parts used within the Autopen® 2, seven
are molded from Delrin® and they represent all of the
mechanical and robust components fundamental to its
operation,” confirms Mark Eaton. “We would not have been
able to produce the Autopen® 2 without DuPont materials,
the strength, dimensional stability and low wear/low fric-
tion of which are key to ensuring simple, reliable and accu-
rate dose delivery.” Rigorous and comprehensive testing
confirmed the compliance of Autopen® 2 with the interna-
tional standard ISO 11608 for pen-injectors.
The Delrin® products were supplied to Owen Mumford by
Distrupol, DuPont’s authorized distributor of its perform-
ance polymers in the UK. Both Distrupol and DuPont pro-
vided additional technical assistance with regard to reduc-
ing friction within the dose setting and delivery mechanism.
DuPont: the material supplier of choice to the
health care segment
DuPont offers one of the broadest portfolios of engineering
plastics and thermoplastic elastomers for medical devices,
surgical devices and for diagnostic or pharmaceutical manu-
facturing equipment. The DuPont health care product
offering provides food agency compliance (EMSA and
FDA), ISO 10993-5 and -11 compliance as well as USP
Class VI compliance. Specialty health care products are
manufactured following GMP.
The specialty health care grades with regulatory support are
available in two versions, each reflecting different levels of
manufacturing control and material testing. Customers
work with DuPont to identify the version that meets the
needs of their specific application. Sixteen of the products
are available as “special control” grades that meet very high
standards of manufacturing consistency important for a
wide range of non-implantable medical products. Twelve of
the grades are available in “premium control” versions meet-
ing requirements for even more demanding manufacturing
controls, broader regulatory support, more testing, DMF
access and the highest level of inspection.
http://healthcare.dupont.com
Autopen® is a registered trademark of Owen Mumford Ltd.
Owen Mumford Ltd.
Brook Hill, Woodstock, Oxfordshire, OX20 1TU,
United Kingdom
Tel.: +44 (0)1993 812021
info@owenmumford.co.uk
www.owenmumford.com
CONTACT
PAGE 5
Special Control grade of DuPont™
Zytel®
nylon for collagen implant
delivery device
The ChondroMimetic™ from
TiGenix NV is marketed as a
procedure pack with the collagen
implant preloaded in an accurate,
easy-to-use arthroscopic delivery
device. A Special Control (SC)
grade of DuPont™ Zytel® nylon
was adopted for two of its
component – the plunger and
compressor fingers – each of
which come into direct
contact with the implant and
are key to holding it in place
and inserting it smoothly and
accurately into the defect
site. The DuPont material
was specifically chosen for
the stiffness and low-
friction behaviour of the
plunger as well as
providing the precise
flexibility of the
compressor fingers.
ChondroMimetic™ is a trademark of TiGenix NV
6. With built-in shielding, excellent flow, dimensional stabil-
ity, toughness and strength, Zytel® HTN can reduce the
total system cost of thinner and lighter housings for laptop
computers, tablet PCs, cell phones and other devices. Zytel®
HTN also delivers the right property set for the many elec-
tronic connectors, relays, light-emitting diode components
and various other electrical and electronic parts contained
within these devices. It can withstand high-temperature cir-
cuit assembly methods, including those using lead-free sol-
der, has good strength, stiffness and toughness over a wide
temperature and humidity range, and is now also available
as a halogen-free grade providing conformity with recycling
programs for discarded electronic products.
A thinner, lighter laptop housing
A recent testimonial of the design flexibility afforded by
Zytel® HTN in handheld devices is provided by the
redesigned housing of the Lenovo IdeaPad U550. Weighing
in at just 5.3 lbs (2.4 kgs) and measuring just over one inch
(2.5 cm) in height, it is remarkably thin and light for a 15.6-
inch (40 cm) multimedia notebook. This is partly due to
the use of a non-halogen, flame retardant grade of Zytel®
HTN for the LCD rear cover assembly (the so-called A
cover) and the bottom cover assembly (the D cover). Both
covers had been previously produced using a polycarbonate
(PC)/ acrylonitrile butadiene styrene (ABS) blend, but by
changing to Zytel® HTN it has been possible to reduce their
wall thickness from 1.8 mm – the thinnest thickness possi-
ble with PC/ABS – to 1.3 mm, a reduction of more than 25
percent.
“Material stiffness is one of the critical requirements for the
mechanical stability of a laptop’s A cover, which has to pro-
tect the sensitive electrical components inside the laptop as
well as the LCD screen,” explains Aric Dai (Huafeng),
research and development director of the IdeaPad product
group at Lenovo. “The improved flexural modulus (approxi-
mately 17 GPa) and flexural strength (approximately
300 MPa) of Zytel® HTN makes it the material of choice
for the production of these thinner, lighter and more cost-
effective covers.”
Drop and pressure tests were used to confirm the protective
attributes of the laptop housing, including the placing of
loads of up to 25 kg (55 pounds) on the A cover. During
hands-on consumer reviews, the laptop chassis and lid are
described as exhibiting only mild flex when grabbed by the
corners and twisted, whilst pushing on the back of the lid
does not yield any ripples in the LCD screen – an impres-
sive performance considering its reduced thickness. As well
as improved strength, stiffness and impact resistance, the
specified Zytel HTN® grade also demonstrates excellent
flame retardancy. Whereas a UL-94 V0 rating at 0.8 mm
was specified by Lenovo for the application, the halogen-
free, flame retardant grade of Zytel® HTN achieves this at
just 0.4 mm.
The switch to Zytel® HTN also saw Lenovo adopt Rapid
Heat Cycle Molding (RHCM) technology for the produc-
tion of the highly visible covers. This process can be used to
maximize the surface appearance of injection molded parts
with a minimal effect on cycle time. Part costs can be
reduced using this technology by eliminating the need for
secondary operations to hide surface defects, whilst it can
ZYTEL®
HTN: A MATERIAL OF CHOICE
FOR HANDHELD DEVICES
BY JERRY TSAI AND RUI ZHANG, DUPONT PERFORMANCE POLYMERS ASIA
Engineering thermoplastics play an increasingly vital role in the production of electronic components and
devices. Rather than seeking a one-size-fits-all solution, polymer producers such as DuPont are tailoring materials
to the specific application with the goal of increasing performance and processing efficiency while lowering costs.
One such product group is the DuPont™ Zytel® HTN family of semi-aromatic polyamides, which offers a combi-
nation of properties that make them ideal materials for use in handheld devices.
PAGE 6
7. ZYTEL®
HTN: A MATERIAL OF CHOICE FOR HANDHELD DEVICES
also be used to obtain glossy surfaces even with glass-filled
materials. The adoption of RHCM technology was made
possible by the higher glass transition temperature (around
115 °C or 240 °F) of Zytel® HTN than that of the previ-
ously used PC/ABS blend.
Support in line with the customer's needs
Comprehensive technical support by DuPont assisted
Lenovo in its switch to the higher performance and more
cost effective material solution, as Aric Dai of Lenovo recalls:
“DuPont was able to offer a unique business package includ-
ing access to its CAE capability during the design phase, on-
site technical support, tool and customized gate design and
mold-flow simulation, as well as a decoration solution which
was in line with our design needs.” Indeed, patterns and tex-
ture are a defining element of the Lenovo IdeaPad aesthetic,
and the U550 is no exception. An extremely fine checker-
board pattern molded onto the A cover makes it feel almost
like the texture of knurled metal to the touch. The covers are
painted and subsequent adhesion and warpage tests ensure
conformity with production standards.
The Lenovo IdeaPad U550 with A and D covers molded
from Zytel® HTN was developed in Asia at the end of 2009
and went into commercial production in China during May
2010. Further laptops within the Lenovo range are pro-
duced with either an A or D cover made with Zytel® HTN
depending on design requirements. Members of the Design
& User Experience team for the IdeaPad Product Group at
Lenovo include Bulin Chen (designer), Zhensheng Wu
(designer) and Detao You (material designer).
Dr. Ning Hao
Designer, IdeaPad R&D, Lenovo
No. 6 Shang Di West Road,
Haidian District, Beijing, China
Tel.: +86-10-58862089
haoning@lenovo.com
CONTACT
As part of its technical assistance, DuPont provided recommendations on gate location in order to achieve lower filling pressure
and improved cover flatness
PAGE 7
8. The Ultra Light Urban Vehicle Project is the brainchild of
Martin Morris, professor of mechanical engineering at
Bradley University, Peoria, Illinois (US). The challenge to
design and manufacture a zero-emissions vehicle began in
2006 and has evolved into a 3-wheeled vehicle licensed as a
motorcycle that carries two people, baggage and weighs 430
lbs (195 kgs). It offers regenerative braking, a top speed of
45 mph (72 kmph) and a range of 40 miles (64 km) – the
Bradley design team claims it costs 0.6 cents per mile to
operate.
Several gears used within the vehicle’s drivetrain transmis-
sion have been intricately produced using Delrin® acetal
(POM) from DuPont Performance Polymers. Design and
manufacturing support for the project was provided by
Winzeler Gear, Harwood Heights, Illinois. The gears face
conditions that traditional engineers may have previously
considered off limits for standard acetal material, as Mike
Cassata, design engineer at Winzeler Gear confirms: “The
high-performance nature of a homopolymer acetal can man-
age the torque and load while delivering low friction and
reduced noise.” He added that the planetary transmission
gears of Delrin® POM must withstand the torque produced
by a 25 horsepower motor @ 6,000 rpm.
The gears can be machined from Delrin® bar or plate stock,
significantly cutting cost and time while delivering
mechanical properties comparable to the injection molded
gears. “We can proceed from design to machined models
in weeks, with a small tooling investment,” said Cassata.
The successful use of Delrin® for gears in the Ultra Light
Urban Vehicle goes some way to challenging the traditional
preconception that POM is unable to withstand the harsh
conditions associated with transmission applications. It is
not difficult to imagine such gears being used in small
engine transmissions such as those found in riding lawn
mowers and golf carts. Indeed this will be the focus of the
next generation of student design, where the young design-
ers will be challenged to take even more weight and noise
from the vehicle by using more Delrin® POM in the gears
and housings.
“As the world changes, we need to challenge many of our
preconceived notions. We also need more whole brain,
especially right brain, thinking to innovate,” concluded John
Winzeler, president of Winzeler Gears and a fervent sup-
porter of student challenges and art programs. “Student
design challenges, such as the one initiated by Martin Mor-
ris at Bradley University, are great ways to challenge our
prejudices and stimulate new ideas.”
DRIVE YOUR IMAGINATION
BY TIM BROGLA, PROGRAM DEVELOPER AT DUPONT PERFORMANCE POLYMERS
An Ultra Light Urban Vehicle project at Bradley University shows how acetal gears – specifically gears made of
DuPont™ Delrin® POM – offer strength, toughness and low-friction attributes needed to take the load, stress
generated in drivetrain transmission systems while significantly damping noise and reducing weight inherent in
metal gears.
The drivetrain transmission uses several intricately machined
gears that face conditions that traditional engineers may
consider off limits for standard acetal material
PAGE 8
9. To find equipment in anything but clear shallow water
requires the use of sonar. Even with sonar, visualising the
water column or sea bed is difficult and the industrial users
of the ocean use powered transponders to locate key equip-
ment. Such transponders are not only expensive but require
regular routine maintenance depending on use and battery
life.
It is against this background that Subsea Asset Location
Technologies (SALT) Ltd. of Salisbury (England) devised
the concept for the SonarBell®, a passive sonar reflector
which acts much as a ‘cats-eye’ does in the road. It takes in
external energy and provides a strong ‘reflection’ in return,
magnifying the original signal back to the searchers. This is
achieved without the SonarBell® requiring an internal power
source itself.
How it works is largely down to the elegant use of materials
technology for its construction. Looking very much like a
bowling ball with diameters up to 200 mm, the SonarBell®
has an outer shell made of DuPont™ Zytel® nylon and a core
made of very soft silicon-based gel. The different acoustic
qualities of the two materials used means that the sound
waves from the received sonar signal travel faster round the
Zytel® shell than through the silicon. This creates a construc-
tive interference that delivers a return signal significantly
higher than a hard reflecting sphere might otherwise deliver.
It is omni-directional and is detectable by sonar in excess of
2 kilometers (1.2 miles) away depending on frequency of
operation.
The shell consists of two hemispherical parts, molded from
Zytel®, that are currently joined by an adhesive, although
spin welding is being investigated. The specific grade of
material used was determined by the particularly demand-
ing requirements of the design. As well as being able to
withstand pressures of around 410 bars at depths of up to
4,100 meters (4,484 yards) the material also has to be
impervious to moisture and possess specific sonar frequency
properties. Providing ongoing support to SALT and its pro-
duction partners from its technical resources in the UK and
Geneva, DuPont accompanied the development of the
SonarBell® from its earliest prototype to the current produc-
tion design. This included the provision of test samples and
material data as well as guidance on mold and gate design.
DuPont experts also recommended suitable spin welding
designs and specific operating parameters to achieve opti-
mum weld quality with Zytel®.
The SonarBell® can be used in many market sectors: besides
military use, the units can also be used to provide navigation
lanes on the seabed or for keeping track of expensive subsea
equipment. They can also mean fewer dolphins get caught
in fishing nets, as Mr Tiltman, Chief Technical Office at
SALT explains: “We can make the SonarBell® respond at an
effective frequency that will allow the mammal to see the
net much better using its sonar.”
SonarBell® is a registered trademark of Subsea Asset Location
Technologies Ltd.
.Subsea Asset Location Technologies (SALT)Ltd.
Upper Courtyard 2, Renshaw Barns,
Upper Woodford, Salisbury, Wiltshire, SP4 6FA
Tel.: +44(0) 1722 782856
Fax: +44(0) 1722 782856
info@cesalt.co.uk, www.cesalt.co.uk
CONTACT
SONAR TRANSPONDER RELIES ON
DUPONT™ ZYTEL®
BY IAN WELSH, SENIOR DEVELOPMENT SPECIALIST AT
DUPONT PERFORMANCE POLYMERS UK
Theelegantuseofmaterials,includingDuPont™Zytel®nylon,hashelpedrevolutionizeunderwatersubseaassetlocationand
preventmarinemammalsgettingcaughtinnets.
PAGE 9
11. The inverter module is at the heart of a photovoltaic system:
it converts direct current produced by the solar modules into
alternating current, which is subsequently fed into the
national grid. Its housing is usually made of metal due to the
high requirements in terms of dielectric strength and fire
safety that apply to such an application. However, in the latest
generation of ‘Sunny Boy’ inverters from SMA Solar Tech-
nology AG, Niestetal (Germany), a Bluetooth interface is
used to enable wireless communication with the photovoltaic
system. Because metal is impenetrable for radio waves, the
company sought to develop a polymer cover for the lower sec-
tion of the housing where the switch disconnector, the elec-
tronic display unit and the radio module are located.
The material used to produce the cover (see image right,
black section of inverter module cover) is a special, flame-
retardant grade of DuPont™ Zytel® PA66/6 copolymer with
a 25 wt. % glass fiber reinforcement. With a CTI value
(CTI = Comparative Tracking Index) of 325 V, a GWFI
value (GWFI = Glow Wire Flammability Index) of 906 °C
and classified with the UL94 V-0 flammability standard, it
meets high dielectric strength and fire safety requirement.
The specified Zytel® grade also provides very high mechani-
cal strength and stiffness as well as high dimensional stabil-
ity. The material’s low tendency for warpage or shrinkage
during injection molding, combined with structural
enhancements such as reinforcing ribs, enable compliance
with even the tightest of manufacturing tolerances. This
ensures a high accuracy of fit with the other housing section
made of cast aluminum. Moreover, the use of Zytel® ensures
a high surface quality for the visible component.
Low friction and low maintenance polymer
bearings
In Majadas de Tiétar, Spain, bearings made from a particu-
larly low wear/low friction grade of DuPont™ Delrin® acetal
resin support a total of 192,000 parabolic mirrors at a solar
thermal power plant belonging to ACCIONA Energía S.A.
The material possesses a very low dynamic coefficient of fric-
tion of 0.13 (standard grade: 0.35), enabling the reliable,
smooth and millimetre-precise positioning of the hydrauli-
cally-operated mirrors in accordance with the sun’s move-
ment. Consequently, this helps further improve the plant’s
overall effectiveness. Thanks to the high wear resistance of
the material, maintenance costs over the entire lifetime of
the plant are reduced when compared to steel bearings. This
ultimately helps reduce total operating costs and thereby the
cost of energy production.
ACCIONA Energía is one of the global leaders in the pro-
duction of solar thermal power plants. The company cur-
rently operates three plants in Spain and one in Nevada/USA
with an overall capacity of 214 MW. The 50 MW solar
thermal power plant in Majadas de Tiétar supplies 32,000
households with environmentally-friendly power. When
compared to a traditional coal-fired power station, the solar
thermal power plant contributes to an annual saving of
approximately 100,000 t CO2.
http://photovoltaics.dupont.com
NEW DEVELOPMENTS FOR THE
PHOTOVOLTAIC INDUSTRY
BY ORVAR OTTERSTEDT, PV MARKET DEVELOPMENT MANAGER
AT DUPONT PERFORMANCE POLYMERS
DuPont materials have been used in the photovoltaic industry for more than 30 years. Amongst recent applica-
tions are the development of a cover for an inverter module, made from a special, flame-retardant grade of
DuPont™ Zytel® PA66/6 copolymer, and bearings used solar tracking systems, made from a particularly low
wear/low friction grade of DuPont™ Delrin® acetal resin.
PAGE 11
