September 22, 2011
A Penton Media Publication
Tune in to EngineeringTV.com
High-tech
Zeppelins
page 42
CONVERTING GLASS
BOTTLES TO PET,
page 23
WHEN SOLAR ARRAYS
CATCH FIRE,
page 50
HOW TO SELECT
PNEUMATIC
CYLINDERS,
page 56
AIR CUSHIONS THAT
SELF-ADJUST,
page 64
Stop Your Fretting
BaldorDodge® Grip Tight® Adapter ball bearings are
the solution for damage-free shafting, reduced vibration
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• Unmatched Quality
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costs and stop your fretting once and for all.
• Lower Total Cost of Ownership
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©2011 Baldor Electric Company
RS# 101
• Superior Reliability
Ultra Lights
8000 psid
.125" Dia. Lee Chek
0.75 Grams
With today's high cost of fuel, it's never been
more important to shed aircraft weight. Fortunately,
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The Lee Company
2 Pettipaug Road
Westbrook, CT 06498 USA
860-399-6281
www.theleeco.com
Westbrook
•
London
•
Paris
•
Frankfurt
RS# 102
•
Milan
•
Stockholm
VOLUME 83
ISSUE 16
SEPTEMBER 22, 2011
pneumatics technology guide
cylinder
cushions
adapt
on the
fly
FEATURES
Self-adjusting cushion
self-adjusting air cushions
let machines run smoother and faster.
Authored by:
Michael Guelker
Product Manager, Pneumatic Actuators
Festo USA
Hauppauge, N. Y.
Edited by Kenneth J. Korane
[email protected]
Key points:
42
Adjustable air cushion
Adjustable air cushions control
piston speed by throttling exhaust
air (red) through a needle valve.
• High machine speeds can lead to
damaging vibration and impact loads.
• Conventional pneumatic-cylinder
cushions prevent end-of-stroke
impacts, but require painstaking
adjustment.
• New self-adjusting air cushions adapt
to changing loads and operating
conditions.
Bye-bye blimps.
Willkommen Zeppelins
Goodyear Tire & Rubber Co. is
upgrading its fleet of blimps, turning
them in for larger, more-advanced
Zeppelins.
Resources:
Festo USA, www.festo.com/cms/en-us_
us/index.htm
RS# 622
ion via our
Request free informat
Web site at
Reader Service
esign.com/rsc
www.machined
64
mACHINe Design.com
Self-adjusting air cushions exhaust
compressed air through slots in the
cushion spud.
A common goal throughout the industrial world is to boost productivity
while reducing costs. Increasingly, this means cutting machine cycle times.
For pneumatic devices, this often requires running actuators as fast as possible without introducing excessive shock and vibration to products and
equipment.
To reduce an actuator‘s impact energy, engineers rely on two common types
of integrated cushioning — bumpers and air cushions. Flexible bumpers are
generally made of an elastomer incorporated into the piston or end cap. They
effectively reduce impact noise; however, they only absorb small amounts of
energy, limiting them to slow-speed, small-load, or short-stroke applications.
Operating with higher loads and speeds demands additional cushioning to
avoid damaging the cylinder and machine. Engineers generally use air cushions for end-of-stroke damping in these cases.
Unfortunately, these are not plug-and-play devices. Experienced maintenance technicians must adjust the air-cushion valves, and that depends on the
cylinder’s operating pressure, speed, and load. Subsequent changes to these
parameters means the air cushions need to be reset. Otherwise, the machine
may run slower or face unacceptable impact loads.
A new type of air cushion automatically adapts to changing conditions,
eliminating the headache of manual adjustments. It offers the potential to increase productivity and reduce maintenance costs.
Cushion basics
Air cushions are variable-orifice air dashpots. As the cylinder cycles, a spud
on either side of the piston closes a passage to the main piston chamber. This
traps air in the cylinder end cap and bleeds it off through a small port conSeptember 22, 2011
trolled by a needle valve. The cylinder traps a fixed volume
of air each cycle. But because air is compressible, the load,
velocity, and pressure in the cylinder all affect air-cushion
performance.
For any given set of conditions, there is generally only
a small window of needle-valve adjustments that provide
acceptable cushioning. Closing the needle valve too far results in high initial reaction forces, which slow the load too
quickly. It can also cause end-of-stroke bounce: the piston
oscillates as it decelerates, causing vibration and extending
cycle time.
Open the needle valve too far, however, and the trapped
air does not generate sufficient back pressure. The load
reaches the end of stroke too quickly and the piston hits the
end cap. And as mentioned above, once the needle valve
is properly set, any change in weight, pressure, or velocity affects cushion reaction and means the valve must be
readjusted.
Self-adjusting cushions
Recently developed self-adjusting cushions eliminate
the need for manual adjustment. In principle, they work
the same way as conventional cushions, except the cushioning air exhausts through notches in the cushioning piston, not past an adjustable needle valve.
The geometry of these notches is critical. LongitudiSeptember 22, 2011
64
off accidental fires
50 Heading
in solar arrays
Fighting a PV panel fire is hazardous
enough without having to stand in
water next to a 600-Vdc power source
that can’t be turned off.
56
pneumatics technology guide
guidelines for
SeleCting
CylindeRS
pneumatic cylinders come in thousands
of versions. here are some tips for
choosing the best one for the job.
Guidelines for
selecting cylinders
Pneumatic cylinders come in thousands
of versions. Here are some tips for
choosing the best one for the job.
Authored by:
Sheila Campbell
Product Manager - Actuators
Norgren Inc.
Littleton, Colo.
Edited by Kenneth J. Korane
[email protected]
Key points:
• Pneumatic cylinders come in many
basic versions.
• All cylinders can be tweaked to
better fit an application.
• Custom designs can perform better
and save money when standard
cylinders don’t fit the job.
64
Cylinder cushions
adapt on the fly
Resources:
Norgren Inc., www.norgren.com
RS# 621
Clean, compact,
durable, and fast-acting
air cylinders are workhorses on
packaging machinery.
56
Self-adjusting air cushions let machines
run smoother and faster.
mACHINe Design.com
ion via our
Request free informat
Web site at
Reader Service
esign.com/rsc
www.machined
September 22, 2011
56
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MACHINE Design.com
SEPTEMBER 22, 2011
mACHINe Design.com
65
Directional
Control
• Solenoid valves
• Manifolds
Air Preparation
•
•
•
•
•
Filters
Regulators
Lubricators
Filter/regulator combos
Relief valves
Check around! You’ll see we’ve
got great prices on ALL the components
you need to complete a pneumatic
control system.
Stainless Steel
Pneumatic
Cylinders
CHECK OUT OUR PRICES ON VALVES and FRL
• Non-repairable
cylinders
• Position switches
• Compact round body
cylinders
AutomationDirect
Product Description
NITRA
MSC
McMaster-Carr
Grainger
Directional Solenoid Valve
5-port, 4-way, 2-position, 1/4” NPT,
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$84.81
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1/4” NPT, gauge, mounting bracket
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$115.47
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AFR-3233
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42007401
6124K513
7390K17
4ZK92
All prices are U.S. published prices. Many other part numbers are available from all vendors. Items are closest equivalents; some minor differences may exist. Automationdirect prices are
from March 2011 Price List. MSC prices are from www.mscdirect.com 2/22/11. McMaster-Carr prices are from www.mcmaster.com 2/22/11. Grainger prices are from www.grainger.com 2/22/11.
Prices subject to change without notice.
Tubing and Hose
• Polyurethane or Nylon
12 tubing in popular colors
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• Polyurethane straight
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fittings
CHECK OUT OUR PRICES ON CYLINDERS
AutomationDirect
Part Description
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MSC
McMaster-Carr
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Stainless Steel Air Cylinder
2 inch bore, 4 inch stroke, double acting,
pivot/double end mount
$53.25
$99.37
$73.93
$70.97
Stainless Steel Air Cylinder
3/4 inch bore, 1 inch stroke, single acting
spring return, nose mount
$11.25
$19.18
$15.35
$15.02
Stainless Steel Air Cylinder
1-1/16 inch bore, 6 inch stroke, double
acting, pivot/double end mount
$24.50
A17060DP
$48.20
36696847
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6498K658
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6W130
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6W070
All prices are U.S. published prices. Many other part numbers are available from all vendors. Automationdirect prices are from March 2011 Price List. MSC prices are from www.mscdirect.com 2/22/11.
McMaster-Carr prices are from www.mcmaster.com 2/22/11. Grainger prices are from www.grainger.com 2/22/11. Prices subject to change without notice.
www.automationdirect.com/pneumatic-parts
Fittings
• Bulkhead, straight, tee,
elbow, Y, cross and
triple branch unions
Flow Control
www.automationdirect.com
• Manual hand valves,
Go online or call to get complete information,
request your free catalog, or place an order.
stop, check, meter-in,
meter-out and inline
RS# 103
1-800-633-0405
DEPARTMENTS
ON THE COVER
An LZ N07-101 Zepplin
8 EDITORIAL
Food for thought: The distance
between a field and your plate
10 EDITORIAL STAFF
12 LETTERS
18 SCANNING FOR IDEAS
Hybrid sweeper-scrubber goes green
Gas springs provide just the right force
22
32
38
40
REPORTER’S NOTEBOOK
LOOKING BACK
ADVANCED MANUFACTURING
BERKE ON SAFETY
Beware of unsafe guards
68 PNEUMATIC PRODUCTS
72 SOFTWARE PRODUCTS
74 PRODUCT SPOTLIGHT
Bearings & guides
76
88
90
93
94
94
PRODUCTS
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BACKTALK
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More than 200 packaging
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Product and supplier database
MACHINE DESIGN’s OEM Supplier Directory is the place to find manufacturers and
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than 2,500 types of components and systems — everything from engineering
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Information is grouped by technology: CAD/CAM, electrical/electronic, fastening/
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Micro vehicle is tough as nails
At AUVSI Unmanned Systems 2011, QinetiQ debuted their latest micro
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New bearings catalog
EDITOR’S WEB PICKS
A new catalog from igus covers
plastic bushings, spherical bearings,
and linear bearings and guides. It
helps users select products by industry, application, or criteria such
as load, temperature, friction, and
wear. It also includes drawings and
a number of new products. Get it at
www.igus.com/quickorder.
RS# 105
6
MACHINE Design.com
SEPTEMBER 22, 2011
Enclosures en español
tion, electrical conductivity, thermal
management, EMC/EMI shielding,
and packaging for cushioning and
protection. View it at www.fabrico.
com/markets-applications-batteries.
htm.
Pumps and compressors
The new Thomas Global Catalog
has updated specs and performance data on hundreds of articulated piston, diaphragm, rotary,
and linear oilless air compressors/
vacuum pumps; and peristaltic, linear, and diaphragm liquid pumps.
Selection guides help users quickly
find the right product by technology and model. View or download a
copy at www.gd-thomas.com.
Pentair Technical Products,
Hoffman has a new Web site
(http://hoffmanonline.com/espanol)
offering a wide range of Spanishlanguage literature on engineered
enclosures. It includes a specifier’s
guide, product catalog, a white paper on global standards, renewable- Guide to inspection
energy brochure, and an interactive software
selection tool to calculate cooling
Delcam has an online guide relatrequirements based on thermal
ing new developments in its inspecload and enclosure size.
tion software. The site includes a
series of videos on capabilities, enVideo demystifies
hancements to GD&T functions, and
battery insulation
Fabrico’s new video looks at materi- how to speed analysis, efficiently
reuse measured data, and handle
als issues with lithium-ion, nickelcadmium, and other advanced bat- point-cloud data. View the site at
teries. It delves into electrical insula- www.delcam.tv/pi2011/lz.
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RS# 106
EDITORIAL
Food for thought:
The distance between a
field and your plate
The Pack Expo trade show is about to kick off and is notable because it caters to the
packaging industry. The packaging industry, in turn, largely revolves around the
packaging of food. So it might be appropriate to examine the recent trend toward
hand-wringing over “food miles.” The idea is that the longer food travels before it
hits your plate, the more energy dissipated and greenhouse gases generated.
At least according to popular mythology. The truth of the matter is that most
energy and greenhouse gases associated with food go into its production, not
its transportation. And that goes equally for food bought at the local farmers’
market as well as for that picked from grocery-store shelves.
The issue of food miles has been thoroughly investigated by two environmental engineers at Carnegie Mellon University in the U. S. and by the Dept. for
Environment, Food and Rural Affairs in the U. K. CMU researchers Christopher
Weber and H. Scott Matthews found that the food-production phase contributed
83% of the average U. S. household’s annual carbon footprint for food consumption. Transportation as a whole accounted for only 11% of greenhouse-gas emissions associated with food. And final delivery from producer to retail contributes
only 4% of that 11%.
It also emerges that transport by ship, rail, and air freight over long distances
is efficient compared with trucking food a comparatively short distance to its
final destination. The trucking phase is responsible for 71% of the total greenhouse gases generated while transporting food. Wholesaling and retailing operations accounted for just 5% of overall emissions.
CMU researchers as well found that globalization has increased the distance
food travels by around 25% since 1997. But this has boosted greenhouse-gas
emissions associated with transport by a mere 5%, simply because ocean shipping is far less energy intensive than overland trucking.
In the U. K., DEFRA examined the “food miles” question partly to see
whether a “buy-local” movement in that country made any sense. DEFRA uncovered percentages similar to those of the CMU research, and also discovered
that “buying local” could lead to more greenhouse-gas emissions rather than
less. The reason is that a lot of produce in the U. K. must be grown in greenhouses rather than in open fields. The energy debt of a greenhouse is a dealkiller, greenhouse gas-wise.
The situation isn’t much better for produce grown in U. K. fields that must
be put in cold storage until it is eventually consumed. U. K. residents generate
fewer greenhouse gases shipping fresh apples in from New Zealand than putting
British apples in a cooler. And when it comes to milk, U. K. dairy farmers use
twice as much energy to produce a metric ton of milk solids than New Zealand
farmers, says DEFRA.
The lesson from all this is that food should be grown where it is most economically virtuous to do so. And the packaging industry needn’t worry about
“buy-local” movements cutting into the need for its products.
— Leland Teschler, Editor
Congratulations to Don Schimizzi, J. Harboy, Rich Werth, Sasa
Pudar, and Bradley Miller. They each won a $100 American
Express gift card as top scorers for August in our World’s
Smartest Design Engineer contest. Challenge yourself
now at www.smartestdesignengineer.com and see if you
can top the scoreboard next month!
RS# 107
SEPTEMBER 22, 2011
Keep Your Machine Running!
Festo’s VTUB pneumatic manifold is not only
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Simply mount valves with one single screw.
Designed for corrosion resistance, your machine
will be running longer and faster with the VTUB.
RS# 108
Global manufacturer of process control and factory automation solutions
For more information:
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OUR ANGLE IS…YOUR GEAR
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[email protected]
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Stephen J. Mraz,
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We have the motion solutions.™
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Looking for more? Scan with your
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RS# 111
Aerospace Products:
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LETTERS
Details, details, details
The recent article on hardness
testing was interesting and useful (“Getting Help from Hardness Testing,” July 7). It provides
technical information on various
types of hardness, one of the important mechanical properties of
materials in general, especially
for metal cutting.
But there are a few discrepancies:
• The definition of “ANSI” 4130
steel is incorrect. ANSI is an
acronym for the American National Standards Institute. Correct definition of this grade of
steel is AISI/ASTM 4130 (AISI
stands for American Iron and
Steel Institute, and ASTM stands
for American Society for Testing
and Materials).
• The description of the steel heat
treatment that increases hardness left out the critical fact that
for annealing, the rate of furnace
cooling (so many degrees per
hour) and the final cooled temperature should be provided.
Otherwise, the tensile and yield
strengths of a given grade of
steel cannot be verified.
• The information on Brinell hardness did not mention the standard ball and standard loads for
a Brinell hardness tester. The balls
should be 10.0 mm in diameter
and made of hardened steel and
tungsten carbide. Balls that aren’t
10 mm should meet ASTM E 10 requirements. The test uses loads of
500, 1,000, 1,500, 2,000, 2,500, and
3,000 kgf. And the 500-kgf load is
for testing relatively soft metals
such as copper and aluminum alloys. The 3,000-kgf load is mainly
used to test steels and cast irons.
• The article left out the range of
the most accurate readings (the
minimum and the maximum values) for Brinell and Rockwell (HRB
RS# 112
Produce smart phones faster
with high speed bearings
Ever wonder how producers of extremely advanced
consumer electronics, like smart phones, manage to
keep launching new generations of these products
at such a ferocious tempo with consistently high
quality?
SKF product manager Satyen Bohidar and SKF’s
sales team have part of the answer – SKF-SNFA
high-speed super precision bearings. They allow
the machine tools used for manufacturing key
components of these products to run flawlessly
and precisely at up to 60.000 rpm 365 days
a year.
The result? Smart products are brought to
the market even faster. It’s another great example
of knowledge engineering at work. Find out more
at www.skf.com/poke
The Power of Knowledge Engineering
Milling spindle running
at 40.000 rpm
SKF-SNFA high-speed
bearings
Satyen Bohidar,
SKF Product Manager
RS# 113
LETTERS
and HRC) hardness numbers.
• The information in the table
“Sample hardness ranges for
metals” is inaccurate. A tungstencarbide ball indenter lets you
measure the hardness of heattreated steels up to a maximum
of 627 HB. If the Rockwell hardness is 105 HRB, scale C should
be used because numbers higher
than 100 are inaccurate. If hardness is less than 20 HRC, scale B
should be used for the same reason, i.e., hardness numbers of 19
HRC and lower are inaccurate.
Edmund Isakov
Nail remover update
The Sept. 23 issue from last year featured a nail-pulling gun in the Inventor’s Corner column. It asked readers
to suggest names for the soon-to-bepatented invention. Here are some of
the letters we received, as well as an
update from the inventor.
Nailout, or Nail-out?
Trevor Rowe
How about the “Nail Biter.”
LeRoy Henkel
My son and I read the article about
the pneumatic nail remover. My
13-year-old son, Wyatt, suggests
“NailOut.” He enjoys building with
wood but he says removing nails is
too much work.
H. Hopkins
The name “Nail Ripper” would
make the tool sound robust, which
I think is what you need to encourage sales.
Ted Brydges
I’m partial to the Anti Nail Gun name.
Dan Brenton
Name it the DeNailer, or simply
Pneumatic Nail Puller.
Gary Partsman
I recently filed the patent to cover
this invention in the U. S. and Canada. And we chose a name from the
several hundred suggestions we received mostly due to the magazine
article, the “Nail Shark.”
The response I got from the article was really inspiring. I had e-mail
from a great number of companies
ready to buy several right away. It
turns out there is a whole industry
that does nothing but take apart old
buildings to recycle the wood. They
do it mostly by hand. A gentleman I
corresponded with from Habitat for
Humanity said that they routinely
buy and tear down old houses, and
if they could more economically take
them apart, it would save them millions every year.
The first-round prototype built
over this past year pulled out big and
small nails and even a few dry wall
screws. The second version is just
about ready to be prototyped.
I have estimated that there may
Cable entries made easy
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RS# 114
MACHINE Design.com
SEPTEMBER 22, 2011
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14
Sealed to UL/NEMA and IP ratings
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RS# 115
SENSORS | NET WORKS/FIELDBUS | RFID | CONNECTIVITY | INTRINSIC SAFETY
©2011 TURCK Inc. NFPA is a trademark of the National Fire Protection Agency.
LETTERS
be a demand for 250,000 or more in
the first few years. There are between
1 and 2 million carpenters in the U. S.
and Canada, and nearly every one
I have spoken with said they would
buy one of these the first chance they
get.— Jake Kittell
A better way to learn FEA
I wholeheartedly concur with the
thrust of the recent FE Update column (“Surface Contact 101: Block
and Ramp with Friction,” July 7).
However, I think the example chosen was way too difficult for novice FEA users. During the 1980s,
I was a structural loads engineer
working on the Space Shuttle at
Rockwell. The company developed a course for training new users on FEA that contained a series
of problems, each progressively
more difficult than the previous
one, that could be solved by hand.
You could then model and solve
them using FEA.
Zero backlash
In place of the example shown
in this article, I would suggest a
two-step approach. First, solve a
truss that is statically determinate
by hand. Then solve it by FEA. Then
solve a truss that is not statically
determinate (i.e., something that
involves additional relationships
like Castigliano) before you solve
it by FEA. After modeling and solving several simple problems such
as this, you can progress to something more difficult such as modeling nonlinear behavior in FEA.
Warren Merriman
350 psi of vacuum?
In an article on vacuum forming
(“Vacuum-Formed Plastics Fool
Filmgoers,” July 7), it said the technicians “apply about 350 psi of
vacuum.“ This doesn’t really make
sense. Maybe someone meant
pressure?
John Matthews
Good catch. There’s about 350 lb of air
pressure over the area of the sheet. The
process applies a vacuum of about 25
in.-Hg. — Jessica Shapiro
Some serious sarcasm
I have been carefully reading all the
articles associated with electric vehicles (EVs). There is a way to extend
the range of EVs that is so obvious
I do not understand how everyone
is missing it. All EVs should be designed with motors for propulsion on
two wheels and alternators on two
wheels to generate electricity. Ergo,
we will greatly extend the range of
EVs and save a lot of ergs.
I feel sure that when this proposal
is turned into law by our Congress,
sales of EVs will soar. Having solved
this problem, Congress can then address major other issues such as repealing some of those annoying laws
of physics and letting us buy incandescent bulbs.
Jeff Scanlon
Put some teeth
in your motion control
Accuracy to ±30 μm
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Learn more at www.nexengroup.com
Call 800.843.7445
RS# 116
IT’S MOTION
CONTROL VERSUS
MOTHER NATURE
ON CENTRE COURT.
©2010 Moog. All rights reserved.
WHEN IT COMES TO HIGH PERFORMANCE MOTION CONTROL, MOOG EXPERTS ARE THERE.
When design engineers sought the best way to control the new retractable roof at Wimbledon’s famed Centre Court, they turned
to Moog. The result was an innovative all-electric installation that provides 148 axes of control via high performance electric
actuators, servo motors, servo drives, closed-loop controls and software. Now, more than 1,100 metric tons (1,212 tons) of steel
and 5,200 square meters (17,060 square feet) of fabric move swiftly and safely to prevent rain delays.
Moog’s combination of motion control expertise and world-class solutions
can make the difference for you too—no matter what industry you’re in.
For more information call 866-580-7610.
How can we improve your machine design?
View our Wimbledon video at http://info.moog.com/wimbledon/1
WHAT MOVES YOUR WORLD
RS# 117
moog.com/industrial
SCANNING FOR IDEAS
Edited by Stephen J. Mraz
Hybrid sweeper-scrubber goes green
The CS7000 sweeper-scrubber from Nilfisk-Advance, Plymouth, Minn. (www.
advance-us.com), can use a variety of hybrid drives — LP gas/electric or diesel/
electric — for power. There’s also an all-electric version. And it uses electric motors
to eliminate most of the hydraulics commonly used on traditional ride-on cleaning
equipment.
The hybrid version uses liquid propane or a diesel engine to drive a high-capacity
ac-brushless alternator which is hooked to a 36-V battery pack. The batteries’
primary purposes are to provide supplemental peak load sharing
and to keep the machine working for a short time in case
the engine fails. The 36-V power drives the ac motors for steering and propulsion, while
dc motors propel the sweepers and scrubbers. All
Polymer body
the motors
panels won’t
dent or corrode,
or damage
surroundings
Three-stage
vacuum motor
Filter with
variablefrequency
shaker
Heavygauge steel
unibody
frame
75-gallon
corrosionproof
recovery tank
7-cu-ft drysweeper debris
hopper
Dust suppression
(optional)
r
are IP55 wash-down rated. Engine speed adjusts to deliver all the power needed to
formation via ou
Request free in Web site at
support various machine operating modes. The hybrid machines use 50% less fuel
Reader Service
c
design.com/rs
and emit fewer CO2 emissions.
ww w.machine
The all-electric version, dubbed 3Power, uses the same electric drives and delivers
5.4 hr of run time on a single charge, which is about 65% more run time than competing electric cleaners. It relies on conventional lead-acid batteries.
The vehicles use a cylindrical sweeper with a separate disc scrubber. This lets the
cleaner sweep and scrub in one pass without putting cleaning soluWANT MORE?
tion into the debris hopper, keeping swept up debris dry. An optional
Focus on this code image
dust-suppression feature reduces airborne dust by 85% compared to
using your smartphone and
motorized side brooms. And a nanofiber filter resists clogging.
free software from www.
neoreader.com, and you will be
The cleaner-scrubber can be used for industrial buildings such as
connected to related content
warehouses, factories, and shipping facilities, and in outside areas such
on machinedesign.com.
as park grounds and parking lots.
http://tinyurl.com/4yrjq9t
RS# 401
18
MACHINE Design.com
SEPTEMBER 22, 2011
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