Orbitec 20 valve body production center creates a unique
workholding solution for large awkward-to-turn workpieces
and any others that exhibit similar physical characteristics.
Energy Workholding
Oil
Field
Goods
Workpieces may be slippery,
odd-shaped, and large or
long turbular pipe and bar
Jim Lorincz
Senior Editor
O
il prices are widely
expected to remain
above $100 a barrel throughout the
year well above the
rule-of-thumb level
of $60–70-a-barrel that makes economic
sense to aggressively pursue domestic
drilling. In combination with extensive
activity for the natural gas extraction
method of hydrofracking (a.k.a. fracking),
there’s enough drilling activity to ensure
that shops will have a ready market for
their machining capacity for oil field
goods. The increased activity, especially
as it expands the geographic activity to
the north and northeast to the naturalgas bearing shale formation states, is
offering increased business opportunity
for machine shops located nearby and
Photo courtesy Mazak
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Energy Workholding
for machine builders and distributors and their third-party
suppliers of tooling and workholding.
Automated machining of couplings, which can be
produced by both vertical and horizontal turning centers,
Workholding solutions for the oil and gas industry con-
requires careful attention to chip control. “Materials used for
stantly are challenged by materials, the size and shape of
oil and gas drilling must operate under difficult conditions
workpieces, and the processes being performed, which
deep underground or undersea,” says Jeff Estes, director of
include but are not limited to turning, milling, grinding, and
Partners In THINC (Charlotte, NC). “When machined, they
honing. Oil field goods include products ranging from tubular
typically produce chips that tend to become long and stringy.
goods for casings and the drill string, wellhead valves, and
The challenge is to break chips into manageable sizes so
accessories like chokes and mandrels that are needed to drill
that chip flow is controlled thus making it easy to evacu-
and complete wells. Workpieces range from unwieldy tubular
ate them without stopping the machine. Without good chip
pipe in varying sizes, typically in 30' (9-m) lengths, to solid
breakage, the stringy chips tend to gather on tooling and
slippery bar that must be held securely without interfering
workholding making it virtually impossible to automate this
clamping. Pipe wall thicknesses can range to 1" (25 mm)
machining process .”
required to withstand higher pressures in deep wells or be
thin-walled and difficult to hold.
Large, awkward-to-handle, odd-shaped workpieces are
common in the oil and gas industry. Just picture the Christmas tree valves and manifolds that start out as forgings,
castings, or large blocks of steel and you’ll get a feel for the
diversity of such workholding challenges. Turning these parts
due to their unbalanced odd shapes was a specific development objective for Mazak Corp.’s (Florence, KY) Orbitec 20
valve body production center. In creating a machine that
generates turned feature by moving only the cutting tool while
the workpiece remains stationary, Mazak has also created a
unique workholding solution for this category of workpiece,
and any others that exhibit similar physical characteristics.
The customized Okuma oil coupling cell was developed
specifically for LB pipe.
Avoiding Out-of-Balance Conditions
When these types of large odd-shaped parts rotate around
“We have automated both processes in the Okuma Oil
a stationary tool, out-of-balance conditions can arise due to
Coupling Cell to keep spindle utilization high. With an auto-
their masses and often lopsided shapes. The ideal way to
mated system, there isn’t an operator needed to remove the
generate turned features on big cumbersome parts, Mazak
chips. Robots can handle couplings that weigh as much as
reasoned, is to do so while the parts remain clamped and
70–120 lb (32–55 kg) and be from 3 to 19" (76–482 mm) in
stationary, moving only the cutting tool. The Orbitec 20 is
diameter with sufficient wall thickness to withstand the weight
able to complete most valve and other large-part machining
of pipe and pressures of oil,” says Estes. One version of the
in one clamping, with the ability to generate phonographic
Okuma Oil Coupling Cell combines two CNC machines, a
finishes on flange surfaces, tapered bores, and perform
VTL and an horizontal turning center. The coupling cells are
feed-out grooving operations. In addition, other processes,
complete packages that can be customized with a variety of
including trepanning, internal grooving, and concave machin-
machine configurations to meet specific customer needs.
ing, are possible. The Orbitec 20 features a dual 630-mm
Each is set up and ready to run with special workholding, chip
pallet changer that matches the pallet size of the HCN 6800
evacuation, cutting tools, and programming. Special attention
machining center and is compatible with Mazak’s Palletech
has been paid to chip evacuation, because of the potential
system so that a complete automated valve production ma-
volume of long stringy chips that are produced in turning and
chining system can be configured.
especially threading.
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Energy Workholding
Many Ways to Hold Workpieces
rigidity. “When machines are sitting idle, they’re losing money.
Oil field workholding products available from Schunk
Vero S is designed for milling, grinding, broaching, finishing,
Inc. (Morrisville, NC) include lathe chucks and chuck jaws,
and turning. It establishes the zero point for the machine. The
stationary workholding, and magnetic workholding. “We
entire unit is made out of hardened stainless steel and fully
focus on getting more parts to the spindle that will allow
sealed. These two improvements have virtually eliminated the
the users to get as much production as possible out of their
possibility of corrosion, and binding”.
machines,” explains Brad Evans, product manager-work-
“For larger applications, we can monitor the clamping slides.
holding. “In addition to workholding for rotating solutions
You can imagine that you have a machine with a 20' [6-m] bed
we offer workholding for turning nonround parts like pump
and a fixture up there weighing several tons, if you had a pin that
housings with special chucks or the Vero-S quick-change
was stuck in the older version, you didn’t know that, and you
palleting systems for horizontal turning on VTLs. Stationary
tried to pull this 5-t fixture off, that’s a problem. The new system
workholding includes complete stationary workholding such
monitors the slides through air switching and an alert. With stain-
as pneumatic, hydraulic, and manual products, and a com-
less construction, it’s almost unnecessary, but it does represent
plete line of magnetic workholding.”
peace of mind for the machine operator,” Evans says.
Schunk’s magnetic workholding includes permanent electro
milling magnets, grinding magnets, and radial turning magnets
from 8" (203-mm) to 4-m diam. “Magnetic workholding has
proven to be especially effective in large prismatic parts or
round parts,” says Evans. “With magnetics, for example, we
can hold bar stock 10” (254 mm) in diam up to 7-m long (or
longer) or fixture prismatic workpieces like housings or blout
preventers on five-axis mills so that five faces can be accessed
for machining. This reduces setups and improves accuracy.”
Constant State of Improvement
“Workholding solutions for the oil and gas industry are in
a constant state of improvement,” says Larry Robbins, vice
Workpiece block held rigidly for roughing operation using
only four Schunk Vero-S NSE+138 modules on risers and four
standard clamping pins.
president-sales, SMW Autoblok Corp. (Wheeling, IL). “It’s getting more and more competitive to pull oil out of the ground
in North America, and we’ve developed the technologies that
allow it to be done at a lower cost and allow us to do more
Schunk’s Vero-S quick-change zero-point pallet system
onshore production of oil and gas.” SMW Autoblok’s Oil Coun-
is designed to allow change out of a machine in a matter of
try Tubular Goods guide includes everything from its simple
minutes and increase the capacity of the table, because the
standard trademarked Big Bore through hole front-mounted
fixture clamps are on the bottom of a pallet or workpiece.
pneumatic chuck to the latest self-centering, compensating
“With the clamping pin inserted into the bottom of a pallet or a
chucks. “Putting pneumatic chucks on both the front and rear
workpiece, we achieve 5µm repeatability in moving from ma-
of the machine spindle, replacing a manual chuck, over-
chine to machine, as long as both are set up with the Vero-S,”
came the problem of the pipe whipping around wildly,” says
says Evans. “All that has to be changed over are tools and
Robbins. Extended stroke versions of chucks allowed pipe
program. This also works for a CMM. A part can be cut on a
with flanges to clear the jaws of the chuck as it was pushed
machine, left on a fixture, taken to the CMM on the fixture, in-
through as processes are changed or new pipe is loaded.
spected, and returned to the machine for rework if necessary
in minutes without a time consuming locating process.”
The Vero-S concept allows the user to set up a machine
quickly, reduce spindle downtime, and maintain accuracy and
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“We can produce about 20-30 times more pipe than 20
years ago. It’s amazing. Ninety-nine percent of the time they
want the pneumatic self-contained chucks, because it allows
them to use the full bore of the spindle.”
Pipe is presented in one of several different ways to the ma-
threading a piece of pipe, it centralizes the pipe with three
chine. It comes in straight or bent due to out-of-round condition
jaws, once the chuck sends feedback through its PLC to the
of the pipe or due to natural sag of long pipe. Using a standard
CNC control, it allows you to centralize to the bore of the pipe
air chuck requires shimming the jaws to accommodate the
with the center along the spindle of the machine. The com-
out-of-round condition. To address these
conditions, SMW Autoblok introduced its
BIG Bore BB-AZ three-jaw chuck which
allows operating the chuck in either the
self-centering or compensating mode.
“The BB-AZ chucks can do one or the
other, but can’t do both at the same time.
They do save an operation by centering
the pipe or clamping it in a compensating mode and doing away with the need
to shim the jaws.”
“Workholding solutions
for the oil and gas industry
are in a constant state
of improvement.”
To speed clamping, SMW introduced
the BB-SC three-jaw chuck clamping
with spring packs, which also allows
partial opening and closing (jogging)
for shimming. With spring close and air
open, the chuck reduces standard air
chuck opening from 12-15 sec to 3 sec
and offers constant and consistent grip
force, saving time and power needed for
shop air. “The Spring Pack Chuck does
away with the need for air to close so
you’ve cut your consumption at least in
half and you’ve cut the time way back
because the spring to close only takes
milliseconds to actuate to close on the
pipe” says Robbins.
“Our newest technology is the BBFZA self-centering and compensating
chuck--all built into one. With it you
don’t need a centering chuck to centralize the part, and basically it allows you
to grab a piece of pipe whether it’s bent,
out-of-round, or deformed. If you’re
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Energy Workholding
ing jaws sense that the compensating jaws are clamped in a
position, they retract. You’ve cut a whole operation out of what
used to take to centralize a piece of material with a centering
chuck, shim the jaws, clamp the part, and every time you reclamped your piece you had to go through all these operations
over and over again. “We’ve cut, depending on the application, up to 50% out of the processing of each piece of pipe.”
Good Times in the Oil Patch
These are good times for the oil industry, says BJ Lillibridge, Pratt Burnerd America/Atlas Workholding (Kalamazoo, MI). “Business is at a high level and the principal challenge is capacity, keeping up with the growth of the industry.
"For large workpieces, flip the tool not the part using an
angle head toolholder," says BIG Kaiser's Gerard Vacio.
We’ve seen oil industry cycle many times over. It’ll go from not
being able to keep enough product in supply to having inventory nobody wants. Our oil country chucks, the King Bore Oil
pensating jaws come in and clamp on the OD of the part and
Country three-jaw universal manual chucks come in sizes
adjust to the part with swivel or roller jaws. Once the center-
from 20" up to 48" [500 mm up to 1200-mm] diameter and
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February 2012
larger if needed. But the most popular sizes in the industry
to flip it can be extensive. Flipping the tool with an angle head
are 24 and 32" [600 and 800-mm] diameter.”
might be more cost-effective. Form and positional tolerances
Two different styles of chuck are available. “One is the fourjaw independent chuck with each jaw moving independently so
can also improve when multiple faces of a large workpiece are
machined in one setup. The workholding task might be to design
you have full adjustment for concentricity. They are used on the front and on the
back of the machine. The other style is
a three-jaw chuck with universal design.
All three jaws go in and out simultaneously so there is no special concentricity adjustment. Four jaw chucks which
is the oldest technology outsells three
jaw chucks by four to one. For big bore
lathes, manual chucks feature through
holes from 6.5 to 21" [165–533 mm].
“Our chucks swallow the pipe and hold
it securely with special diamond-shaped
gripping serrations, because when the
threading is being done, the pipe is slippery and takes a lot of jaw force to grip
it,” says BJ Lillibridge. “One thing we
have noticed recently is that some of the
machine builders have decreased the
through hole on the machine to increase
the rpms, but that doesn’t pose any
special problem.”
”Sometimes, a large
workholding problem
can be solved with a little
out-of-the-box thinking.”
Sometimes, a large workholding problem can be solved with a little out-of-thebox thinking. Gerard Vacio, product manager-workholding, BIG Kaiser Precision
Tooling Inc. (Hoffman Estates, IL) offers
this solution to just such a problem about
holding very large workpieces. “Whenever
I am asked to offer workholding solutions
for very large work, I consider flipping the
tool and not the work. The time required
to unclamp a large part and use a crane
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Energy Workholding
a methodology to hold large parts without obstructing access to
Vacio continues, “BIG Kaiser can address the five-sided
features on multiple faces. Five-sided access would be best so
access issue with Unilock, our zero-point clamping system,
you have the option of either flipping the entire workpiece on a
which uses ground retention knobs on the back side of
zero-point fixture plate, or using an angle head.”
the fixture plate or workpiece to pull it down onto the top
of the table equipped with Unilock
pneumatic clamping chucks and lock
it into an accurate location. The entire
assembly can then be flipped into new
orientations for subsequent operations, or an angle head can be used
on as many operations as possible in
the original setup.
“Also, pulling a part down is better than squeezing it. The squeezing
process puts stress on the raw material and the material removal process
can compound the negative effects of
this stress. Pulling the workpiece down
from one side allows the material to sit
in a free state for machining. However,
walls may need to be supported to
control harmonics that would normally
be damped by the squeezing process,”
Vacio concludes. ME
Want More Information?
BIG Kaiser Precision Tooling
Ph: 847-228-7660
Web site: www.bigkaiser.com
Mazak Corp.
Ph: 859-342-1700
Web site: www.mazakusa.com
Okuma America Corp.
Ph: 704-588-7000
Web site: www.okuma.com
Pratt Burnerd/Atlas Workholding
Ph: 269-384-2225
Web site: www.prattburnerd.com
Schunk Inc.
Ph: 800-772-4865
Web site: www.schunk.com
SMW Autoblok
Ph: 847-215-0591
Web site: www.smwautoblok.com
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