Specifications Standards For Shafts Alignment
Coupled shaft alignment is the positioning
of two or more machines so that the rotational centerlines
of their shafts are co-linear at the coupling center under
operating conditions.
LASER SHAFT ALIGNMENT SYSTEM
REQUIREMENTS
The Laser Alignment System used for Coupled Shafts Alignment
shall use either a combined laser emitter and laser target
detector unit or separate units for its laser emitter and
laser target detector.
SHAFT ALIGNMENT TOLERANCES
All shaft-to-shaft centerline alignments shall be within
the tolerances specified unless more precise tolerances
are specified by the machine manufacturer or by the purchasing
engineer for special applications.
COUPLED SHAFT ALIGNMENT TOLERANCE
VALUES
JACKSHAFTS
Below “critical speed” of Jackshaft Short coupling
tolerances apply to each coupling of the jackshaft.
Above “critical speed” of Jackshaft Short coupling
tolerances apply relative to the centerlines of the two
machines.
*References: “The Optalign Training Book, “
1990, Ludeca Inc., Miami, FL.
The Tolerances specified are the maximum allowable deviations
from Zero-Zero Specifications or ALIGNMENT TARGET SPECIFICATIONS
(i.e. an intention targeted offset and/or angularity).
Acknowledging that machines often move after start-up due
to THERMAL GROWTH, dynamic load shifts, etc., the alignment
parameters shall be measured and adjusted for operating
conditions.
COUPLED SHAFTS ALIGNMENT
VERIFICATION
Laser alignment will be performed on the machine tool builder’s
floor on all shaft coupled machines.
When verifying the alignment of coupled shafts the machine
tool builder must document and provide the following data
for each set of coupled shafts:
a. Alignment tolerances used.
b. SOFTFOOT
c. Vertical ANGULARITY (Pitch) at the COUPLING POINT
d. Vertical OFFSET at the coupling point.
e. Horizontal angularity (Yaw) at the coupling point.
f. Horizontal offset at the coupling point.
This information shall be provided to the purchaser at
the time of functional check out.
Verification of alignment and re-alignment will be conducted
at the purchaser’s facility during installation of
the equipment.
MACHINE BASES
MACHINE BASE CONSTRUCTION
A solid and rigid machine base is required to achieve and
maintain shaft alignment.
Where bases are constructed using concrete or grouts final
shaft alignment shall not be conducted until ample curing
time has taken place. (A minimum of Thirty days is recommended)
Where the machine foundation installation specification
does not require a concrete or grout base or the installation
schedule does not permit the proper cure time for the concrete/grout
Where corrosion is or may be a problem the base must be
fabricated of corrosive resistant materials. Where the machine
base is constructed from commercially available steel or
castings:
Use H, M, I, square, tube, and bar shapes with a minimum
0.5 inch (1.27 cm) thickness.
For machine bases consisting of a single steel plate, plate
thickness must equal or exceed the thickness of the machine
foot, but be no less than 1.0 inch (2.54 cm). The plate
surface that the driver and driven machines will bolted
to must be machine ground and of sufficient size to accommodate
the machine components, push/pull blocks and/or jack screws.
Jackscrews must not rest on any rounded edges.
Use of channel or angle stock is not recommended. Where
use is necessary, the channel or angle stock must be reinforced
using square bar or plate meeting the preceding thickness
requirements.
After all welding and machining is completed, stress relieve
the entire base.
FOOT CENTER LINES
The stiffness of the machine base shall be sufficient that
no foot centerline shall deform or deflect more that .001”
(.0254 mm) over the operating range from alignment conditions
to full load conditions.
JOINING SHAPES TOGETHER
When joining shapes together they shall conform to the
appropriate applicable A.S.M.E. and/or C.W.B. standard(s)
for welding.
REQUIREMENTS FOR MACHINE
PADS OR FLATS
After all welding and machining has been completed and
the base has been stress relieved, the surface of all pads
or flats for each machine to be installed on the base must
be co-planar, within .001 inch (0.0254 mm).
MACHINE BASE SUPPORT
The feet of the driver and driven machines must not overhang
the machine base.
JACKBOLTS
Jackbolts shall be located at the front and rear feet of
the movable machine for horizontal alignment positioning.
(This requirement also applies to vertically mounted units
and vertically mounted flanged units). Jackbolts shall be
parallel to the flat/pad surface and align on the center
line formed by the hold down bolts in the cross machine
direction. Ample room shall be left for removal and insertion
of shims used in the vertical alignment of the coupled machines.
HOLD-DOWN BOLTS
The use of hold down bolts is the preferred method of fastening
components to the base. Hold-down bolts shall meet the following
specifications:
a. Hold-down bolts for both the driver and the driven machine(s)
(in pairs or in trains) shall be positioned (spotted) after
the machine’s shafts have been aligned.
b. Hold-down bolts shall be centered in the hole of the
machine foot.
c. Hold-down bolts shall be the preferred method of fastening
machines to the base.
d. Hold-down bolts shall not be undercut (“Chicagoed”)
to achieve HORIZONTAL adjustment.
PIPING
Piping must be fitted, supported, and sufficiently flexible
such that softfoot due to movement caused by tightening
pipe flanges doesn’t exceed .002” (.051 mm).
Piping must not restrict the minimum 180 degree rotation
requirement of the laser alignment system.
SHIMS
Shims shall meet the following specifications:
a. Commercially die-cut.
b. Made of corrosion and crush resistant stainless steel,
which is dimensionally stable when subjected to high compression
over long periods of time.
c. Consistent over the whole shim area, without seams or
folds from bending.
d. Clean, free from burrs, bumps, nicks and dents of any
kind.
e. Size numbers or trademarks etched into the shim, not
printed or stamped.
f. The smallest commercial shim that will fit around the
hold down bolts without binding shall be used.
g. The overall shim pack shall not exceed a total of three
(3) shims.
h. Shims must rest on bare metal, not paint or other coatings.
MACHINE VERTICAL MOBILITY
All machines shall be installed with a minimum of .125
inch (3.0 mm) dimensionally stable shims under each surface
mounting point for vertical mobility.
COUPLING PLAY/BACKLASH
OEM’s must use only the couplings specified unless
otherwise agreed upon by the purchaser. During the alignment
process coupling play or backlash must be eliminated to
accomplish a precision shaft alignment.
AXIAL SHAFT PLAY
Axial shaft play or end play must be no greater than .125
inch (3.175 mm). Accommodation of end movement must be done
without inducing abnormal loads in the connecting equipment.
MACHINE TOOL SPINDLE LASER
ALIGNMENT
MACHINE TOOL SPINDLE ALIGNMENT
GEOMETRY
Machine Tool Spindle Alignment addresses the geometric
relationship between the spindle axis of rotation and a
rotation and a reference datum (e.g. a Master Part)
LASER SPINDLE ALIGNMENT SYSTEM
REQUIREMENTS
The Laser Alignment System used for Machine Spindle Laser
Alignment shall use separate units for its laser emitter
and laser target detector so that Tracking Error and Angular
Error can be distinguished.
MACHINE SPINDLE ALIGNMENT
TOLERANCES
The machine spindle alignment tolerance is MACHINE DEPENDENT
and shall be developed by the purchaser and the machine
tool builder based on the machining operation and tolerance
requirements of the part being machined.
The machine spindle shall be checked relative to a master
part/pallet or suitable reference and be within alignment
TOLERANCE specifications for:
a. TRACKING ERROR
b. ANGULAR ERROR
c. POSITION ERROR
The torque applied to the spindle hold down bolts shall
comply with the spindle manufacturer’s specification.
For features that require more than one machining operation
on the same feature, the alignment tolerance for Tracking
and Angular errors for all spindles in the process is the
final pass tolerance.
MACHINE BASE AND MACHINE SPINDLE
VERIFICATION
The following information shall be provided to the purchaser
at the time of runoff.
MACHINE BASE VERIFICATION
When verifying the MACHINE BASE, the machine tool builder
shall document and provide the following data:
a. The FLATNESS of the surface to which the slide assembly
will be bolted.
b. The flatness of the QUALIFIED LEVELING POINTS, when the
base is mounted in a STRESS FREE CONDITION.
c. The COPLANAR condition of the Qualified Leveling Points.
d. The Parallelism of the Qualified Leveling Points to the
slide assembly mounting surface.
e. A Graphic showing the integrity of Flatness and Coplanar
conditions.
MACHINE SPINDLE ALIGNMENT
VERIFICATION
Laser alignment will be performed at the machine tool vendors
location for all Multi-spindle heads, and all box and motorized
spindle applications.
When verifying the machine spindle alignment the machine
tool builder must document and provide to the purchaser
the following data for each spindle:
a. Alignment tolerances
b. Spindle manufacturers recommend torque and sequence of
hold down bolts.
c. Tracking error (Alignment readings)
d. Angular error (Alignment readings)
e. Position error (Alignment readings)
f. Torque (actual) and torque sequence of hold down bolts.
Verification of alignment and re-alignment will be conducted
at the purchasers facility during installation of the equipment.
MACHINE BASE
MACHINE BASE CONSTRUCTION
A solid and rigid machine base is required to achieve and
maintain spindle alignment.
Proper Civil engineering and Soil base Sampling should
take place prior to pouring the machine base foundation.
Where bases/foundations are constructed using concrete
or grouts, final spindle alignment shall not be conducted
until ample curing time has taken place. (A minimum of Thirty
days is recommended)
The machine base shall meet Level, Flat, and Coplanar requirements
in a stress free condition.
The base shall have qualified leveling points. the qualified
leveling points allow the machine’s flatness and LEVEL
to be checked quickly and easily.
a. The qualified leveling points shall be ACCESSIBLE and
outside the projected area occupied by the machine components.
(Motors, Pumps, Spindle, Slide, Guards, etc.)
b. The qualified leveling points shall be located above
each machine mounting point.
After all welding and machining is completed, stress relieve
the entire base.
MACHINE BASE TOLERANCES:
a. Those portions of the machine base surface that support
the slide assembly and the qualified leveling points shall
be flat within .0002 in per foot (0.0167 mm/meter).
b. The accumulative error in Flatness Surface Integrity
over the entire machine base surface shall not exceed the
value agreed upon by purchaser and builder.
c. Qualified leveling points shall be coplanar within .0005
inch (0.0127 mm).
d. The qualified leveling points shall be parallel to the
slide assembly mounting surface with .0005 inch (0.0127
mm).
MACHINE BASE FLOOR MOUNTING
a. The machine base floor mounting technique shall be approved
by the purchaser.
b. Machine base mounting points shall be accessible, adjustable
and induce no unnecessary strains on the machine base.
MACHINE WAYS
MACHINE WAYS BOLTED TO MACHINE
BASE
Where the individual machine ways are bolted directly to
the machine base, shims and/or grinding may be used to achieve
vertical angular alignment and a vertical position alignment
as dictated by the process and part tolerance. Alignment
methodology and tolerances to be determined and agreed upon
by the purchaser and the machine builder.
MACHINE WAYS ASSEMBLY
The machine way assembly load bearing areas shall be mounted
on individual FULL BEARING FITTING SPACER BLOCKS. The SPACER
BLOCKS shall be used to adjust the way assembly VERTICAL
angular alignment (PITCH) and vertical position alignment.
The blocks shall have slotted holes for easy removal, have
a nominal thickness of .250 inch (6.350 mm) and mounting
surfaces (top and bottom) shall be parallel with .0005 inch.
(0.0127 mm).
Individual spacer blocks at each bolt may be used where
a full bearing fitting spacer block is not practical.
JACKBOLTS
shall be used to move the way assembly vertically and be
located adjacent to each shim/hold down bolt support point.
PUSH/PULL BLOCKS shall be used to adjust the way assembly’s
HORIZONTAL angular alignment (YAW) and horizontal position
alignment. The push/pull blocks shall be accessible.
The machine way assembly shall not be doweled to the machine
base.
MACHINE SPINDLE ADJUSTMENT
DESIGN
The design of an align-able machine spindle assembly shall
incorporate the following:
SINGLE AXIS BOX SPINDLES
AND BOX SPINDLE CLUSTERS
Push/pull blocks shall be used for tracking and position
alignment in the horizontal plane.
Full bearing fitting spacer blocks located under the front,
rear, and all other support points of the spindle shall
be used for tracking and position alignment in the vertical
plane. The blocks shall have slotted holes for easy removal,
have a nominal thickness of .250 inch (6.350 mm) and mounting
surfaces (top and bottom) shall be parallel within .0005
inch (0.0127 mm).
Flange mounted box spindles are not recommend.
MULTIPLE SPINDLES
Provide push/pull blocks for tracking and position alignment
in the horizontal and vertical plane.
A reference spindle shall be designated by the purchaser.
All other spindle axes shall be parallel to the reference
spindle axis within .0005 inch per foot (0.0417 mm/meter).
FLANGE MOUNTED SPINDLES
Push/pull blocks shall be used for position alignment in
a plane parallel to the flange mounting.
Jackbolts shall be used for tracking error alignment.
BUSHING PLATES
Machine spindle and tooling shall be designed whenever
possible to eliminate the need for Bushing Plates.
Where Bushing Plates are necessary:
Bushing liners shall not extend past or above the surface
of the bushing plate. Bushing liner ID centerline shall
be perpendicular to the bushing plate mounting surface within
.0010 inch per foot (0.0833 mm. per meter).
Bushing plate liner position tolerances shall not exceed
5% of total part tolerance.
All bushing plate locating and mounting surfaces shall be
ground to a known datum, square and parallel to .0010 inch
per foot.(0.0833 mm. per meter).
LASER ALIGNMENT SUPPORT SYSTEMS
NOTE: Nominal English/Metric dimensioning is used for Laser/Target
Holding Adapter I.D. and Bushings I.D.., therefore English
to Metric I.D. conversions will not be exact, however the
tolerance integrity must be maintained.
LASER/TARGET HOLDING ADAPTERS shall be:
a. Practical to install and use while machine is in a production
environment.
b. Shall mount to represent the spindle’s axis of
rotation.
c. Provided by machine tool builder.
d. Standard inside diameter of each Laser holding adapter
shall be ground to .7500 inch +.0010/-.0000 inch I.D. (20
mm +.0250/-.0000 mm I.D.). If spacing or center distance
constraints do not allow for a .7500 inch (20 mm) inside
diameter, then the inside diameter may be reduced to the
next appropriate nominal size +.0010/-.0000 inch (+.0250/-.0000
mm). Laser holding adapters shall be of a length that is
as long as is practical and conditions allow, and runout
of the inside diameter to the mounting journal shall not
exceed .001 inch (0.0254 mm).
e. Standard inside diameter of each Target holding adapter
shall be ground to .7500 inch +.0002/-.0000 inch I.D. (20
mm +.0051/-0000 mm I.D.) If spacing or center distance constraints
do not allow for a .7500 inch (20 mm) inside diameter, then
the inside diameter shall be reduced to the next appropriate
nominal size +.0002/-.0000 inch (+.0051/-.0000 mm).
f. Laser and Target post sizes should be common within
one machine.
Adapters are required for each line-up application to secure
the laser or target.
Each adapter shall be black oxide coated and have the following
information clearly stamped and filled with yellow paint
on the body of the adapter.
a. Inside bore diameter.
b. Tooling number and detail number.
All adapter designs requiring tool numbers shall be approved
prior to build.
TOOLING MASTERS/PALLETS AND
FIXTURES SUPPORT SYSTEMS
The tooling masters/pallets shall be:
a. Practical to install and use while machine is in the
production environment.
b. Accurately represent the part characteristic centerline
and made to gage tolerances.
c. Traceable to N.I.S.T.(National Institute of Standards
and Technology).
d. Provided by machine tool builder.
e. All Adapters and Masters are to be housed in an environmental
proof permanent packaging suitable for gage storage.
Details with the master pallet/part shall duplicate the
production pallet/part such as: pallet feet, clamp pads,
registry system, transfer mechanism, etc.
All of the above details and the master pallet/part that
may effect the REPEATABILITY of the master shall be inspected
and documented.
The Master pallet base shall be Meehanite cast iron for
stability. (Variance allowable subject to prior approval
by purchaser).
The master part shall be Meehanite cast iron or metallurgical
stable hardened steel as appropriate based on part size.
Bushings required to mount the target receiver to the master
pallet shall be ground and lapped to .7500 inch + .0001/
- .0000 inch I.D. (20 mm +.0025/25/-0000 mm I.D.) If spacing
or center distance constraints do not allow for a .7500
inch (20 mm) I.D. bushing, then the inside bushing diameter
shall be reduced to the next appropriate size +.0001/-.0000
inch (+.0025/-.0000 mm). Where Bushings are not used, I.D.
sizes may change due to size constraints, however I.D. +
tolerances remain unchanged.
The head of the bushing shall be ground square to the bushing
I.D. within .001 inch per foot (.0833 mm. per meter). Where
there are multiple bushings, the total accumulative error
must not exceed .001 inch per foot (.0833 mm per meter).
All bushings shall be a minimum of 1.5 inch (40 mm) in
length and no blind bushing holes are acceptable with in
the master unless approved by the purchaser.
Nominal cordial distances between all bushings or holes
shall be within 5% of part tolerance maximum error, non-accumulative.
Each transfer leg shall be reviewed to identify if common
bushing/hole positions are required on both sides of the
upright for lining up both left and right machining stations.
All bushings/holes with the master upright assembly shall
be tagged with appropriate hole number and station number,
which provides exact control in positioning the machine.
The indexing direction of the pallet shall be clearly marked
to eliminate incorrect loading by the operator.
The ability to index the master through each station with
the transfer shall be considered during the initial design.
The master will be used to periodically master the pallet
checking gauge and shall incorporate all design features
for this inspection requirement.
All design concepts shall be approved by the purchaser
prior to equipment build.
GUARDS & UTILITY CONNECTIONS
Guards shall have access covers and or be designed for
easy removal ensuring that all alignments points, shims
and adjustment bolts are accessible.
All hard lines will be routed such that all alignment points,
shims and adjustment bolts are accessible.
GLOSSARY
1) ACCESSIBLE: The ability to reach and adjust the aligning
feature. Consideration should be given to confined space
restrictions, removing guards, bushing plates, hydraulic
lines, lubrication lines, electric lines etc.
2) ALIGNMENT TARGET SPECIFICATIONS: Desired intentional
offset and angularity at coupling center to compensate for
thermal growth and/or dynamic loads. Most properly specified
as an OFFSET, and an angle in two perpendicular planes,
horizontal and vertical.
3) ANGULAR ERROR: A misalignment condition characterized
by the angular error between the desired centerline and
the actual centerline. This misalignment condition may exist
in planes both horizontal and vertical to the axis of rotation.
4) ANGULARITY: The angle between the rotational centerlines
of two shafts. Angularity is a “slope”expressed
in terms of a rise (millimeters or thousandths of an inch)
over a run (meter or inches).
5) A.S.M.E.:
American Society of Mechanical engineers
345 East 47th Street
New York, NY 1017
212-705-7722
6) AXIAL PLAY, AXIAL FLOAT, END FLOAT: Shaft axial movement
along its centerline caused by axial forces, thermal expansion
or contraction, and permitted by journal bearings, sleeve
bearings and/or looseness.
7) BASE PLATE: The surface , often made of steel plate
or cast iron, to which the feet of a machine are attached.
8) CO-LINEAR: Co-linear means two lines that are positioned
as if they were one line. Co-linear as used in alignment
means two or more centerlines of rotation with no offset
or angularity between them. Two or more lines are co-linear
when there is no offset or angularity between them (i.e.
they follow the same path).
9) COPLANAR: The condition of two or more surfaces having
all elements in one plane. (per ANSI Y14.5)
10) COUPLING POINT: The phrase “COUPLING POINT”
in the definition of SHAFT ALIGNMENT is an acknowledgment
that vibration due to misalignment originates at a the point
of power transmission, the coupling. The shafts are being
aligned and the coupling center is just the measuring point.
11) C.W.B.: Canadian Welding Bureau:
7250 West Credit Avenue
Mississauga, Ontario
L5N5N1
416-542-1312
12) FULL BEARING FITTING SPACER BLOCK: A single spacer block
used for aligning the machine tool in the vertical plane.
13) FLATNESS: The condition of a surface having all elements
in one plane. (Per ANSI Y 14.5.)
Note: As used in this specifications, a flat is a small
surface flush with or cut into a BASE PLATE, machined flat,
and co-planar with the other flats in the base plate. The
flats support the Shims and/or feet of the machine to be
installed. A pad is a small block of metal that serves to
elevate the feet of the machine above the surface of the
base plate. Pads are commonly used compensate for differences
in machine center line heights, and for increased corrosion
resistance by raising the machine feet out of any possible
standing fluids. Pads and flats have holes drilled and tapped
in their centers to accept hold down bolts.
14) HORIZONTAL: Parallel to the mounting surface.
15) JACKBOLTS, JACKSCREWS , PUSH/PULL BLOCKS: Positioning
bolts on the machine base which are located at, each foot
of the machine and are used to adjust the position of the
machines. Bolts mounted on the machine base or foundation,
optimally at the machine foot locations, which provides
exact control in positioning the machine.
16) LASER/TARGET ADAPTER: A laser/target adapter is an
adapter which allows the laser/target to be mounted into
the spindle or master part.
17) LEVEL: Parallel to a reference plane or a reference
line established by a laser.
18) MACHINE: The total entity made up of individual machine
components such as motors, pumps, spindles, fixtures, etc.
Also reference MACHINE COMPONENT.
19) MACHINE BASE: The structure that supports the machine
or machine components under consideration.
20) MACHINE COMPONENT: An individual unit such as a motor,
pump, spindle, fixture, etc. often referred to as a machine
in its own context.
21) MACHINE DEPENDENT: A condition which is dependent on
the machining operation and the design requirement of the
part being machined.
22) OFFSET: The distance (in thousands of an inch or in
millimeters) between two reference centerlines such as a
spindle center line and a part characteristic centerline
or the rotational centerlines of two parallel shafts.
23) PITCH: An angular misalignment in the vertical plane.
(ANSI/ASME b5.54-1991)
24) POSITION ERROR (CENTERLINE/OFFSET MISALIGNMENT): A
misalignment condition that exist when the spindle/shaft
centerline is parallel but not in line with (not coincidental)
with the desired alignment centerline.
25) PUSH-PULL BLOCKS: Side push-pull adjustment blocks
used for aligning machine tool in the horizontal plane.
26) QUALIFYING LEVEL POINTS: Qualified leveling points
are locations which have their heights defined and must
be in same plane. That plane must be parallel to the mounting
surfaces of the slide assembly.
27) REPEATABILITY: The consistency of readings and results
between consecutive sets of measurements.
28) SHAFT ALIGNMENT: Positioning two or more machines (e.g.
a motor driving a hydraulic pump(s), etc.) so that the rotational
centerlines of their shafts are collinear at the coupling
center under operating conditions.
29) SPINDLE ALIGNMENT: The geometric relationship between
the spindle axis or rotation and a
reference datum.
30) SOFT FOOT: A condition that exists when the bottom of
all of the feet of the machinery components are not on the
same plane (can be compared to a chair with one short leg).
Soft foot is present if the machine frame distorts when
a foot bolt is loosened or tightened. It must be corrected
before the machine is actually aligned.
PARALLEL SOFT FOOT: A parallel gap between the machine
foot and its support surface.
ANGULAR SOFT FOOT: An angled gap between the machine foot
and its support surface.
INDUCED SOFT FOOT: A type of soft foot that is caused
by external forces, ( pipe strain,
coupling strain, etc.,) acting on a machine independent
of the foot to base plate connection.
“SQUISHY” SOFT FOOT: A type of soft foot characterized
by material, (could be Shims, paint, rust, grease, oil,
dirt, etc.) acting, like a spring between the underside
of the machine foot and the base plate contact area.
31) SPACER BLOCKS: See FULL BEARING FITTING SPACER BLOCK.
32) STRESS FREE CONDITION: The condition that exists when
there are no forces acting on the structure of a machine,
machine component, or machine base that would cause distortion
in the structure such as bending, twist, etc.
33) THERMAL EFFECTS (GROWTH OR SHRINKAGE): This term is
used to describe displacement of shaft axes due to machinery
temperature changes (or dynamic loading effects) during
start-up.
34) TOLERANCE, DEADBAND, WINDOW, OR ENVELOPE: An area where
all misalignment forces sum to a negligible amount and no
further improvement in alignment will reduce significantly
the vibration of the machine or improve efficiency.
35) TOLERANCE VALUES: Maximum allowable deviation from
the desired values, whether such values are zero or non-zero.
36) TRACKING/TRACKING ERROR: An angular MISALIGNMENT condition
between spindle centerline and the machine way centerline.
This condition may be present in both parallel and perpendicular
to the way centerline
37) VERTICAL: Perpendicular to the horizontal plane.
38) YAW MISALIGNMENT: An angular misalignment in the horizontal
plane.
39) N.I.S.T.
National Institute of Standards and Technology
Building 304, Room 139
Gaithersburg, MD 20899
301-975-3503
