perm filename KIT1.S[1,VDS] blob
sn#157529 filedate 1975-05-03 generic text, type C, neo UTF8
COMMENT ā VALID 00002 PAGES
C REC PAGE DESCRIPTION
C00001 00001
C00002 00002 NOTES FOR ASSEMBLY OF STANFORD ARM KIT COMPONENTS
C00023 ENDMK
Cā;
NOTES FOR ASSEMBLY OF STANFORD ARM KIT COMPONENTS
by VICTOR SCHEINMAN- VICARM
May 1, 1975
The Stanford arm kit of components consists of all the parts
mentioned in the purchased parts list plus all the custom
manufactured parts denoted with an "S" in the set of arm drawings
supplied with the kit. In addition, all modifications to the
purchased parts, if necessary, are completed by Vicarm.
The kit is shipped in three or four separate shipments. The
first shipment is the bearing shipment. Not all bearings are
shipped, as some are used in the subassemblies supplied later. The
bearing shipment should allow the user to assemble most of the basic
arm components. Joints 1,2,3,4,5, and 6 can all be connected
together for fitting purposes.
Notes on the installation of bearings.
Joint 1: First slip the clamp ring (9-9a) onto the drive tube(9-5)
. (The drive tube should have the screw access holes already
drilled, as noted in the latest drawing set. Then the upper bearing
- KB-040-XP0 is slipped on the drive tube. Then the retaining ring
(9- ) is slipped on. Using machinists clamps, clamp the retaining
ring-bearing -drive tube flange together tightly and dowel pin the
retaining ring in place. Mark the ring and tube so it can be removed
and replaced in the same spot in the future. The lower bearing (
KA-040-XP0 )is tipped sideways and dropped into the main tube. It
should be a light slip fit on both the main column and the drive
tube. Seat the bearing at the bottom of its seating diameter. Then
drop the main tube into the column. The clamp ring is screwed down
with socket head screws inserted thru the access holes in the top of
the drive tube. If the arm is going to be used in an upright
position, it is probably not necessary to retain the bottom bearing,
but this can easily be done by slipping on another retaining ring
before putting on the bottom bearing and dowel pinning it in place.
The exact position can be determined by squashing the ring a bit so
it sticks the the drive tube. Then when the tube is inserted, the
bearing will push the retaining ring up to the right point.
Carefully removing the tube will keep the ring at the right point
until it can be dowel pinned in place. Some bearing preload can be
added by putting an O-ring between the retaining ring and the bearing
with about .015 O-ring squash to act as a spring. Don't put any more
preload than
.015 with this method. If in doubt- just forget the O-ring and leave
at least .005 clearance between retainer and bearing. The bearings
are of the type which require little or no preload anyhow.
The second joint is assembled in a similar manner. In this
case, the rear (motor end) bearing acts as a pilot for the motor
mount plate. The flange end bearing is retained with a retaining
ring as in joint 1, while the other bearing floats on the tubular
shaft. The rear bearing is retained on it's O.D. by the housing and
the motor mount plate.
Joint #3-
The square tube boom rides on 16 rollers. Only about 6
rollers are actually needed to guide the tube, so dont worry if all
dont contact at the same time. The rollers are made up from the 34KDD
bearings and phenolic rings. Epoxy the rings to the bearings with
two bands of cement - one on each side. The rollers are sttached to
the shafts with Locktite adhesive. Use Locktite #35 or #40 adhesive
(available from bearing supply firms),and place one of the roller
clamps with the extra center hole in the center of the rod before
cementing on the second bearing. The spacing of the rollers should
be about 2.30 outside to outside. This will insure that there is no
interference with other rollers. The boom should fit tight enough so
that it springs the rollers out a bit. If it fits very loosly, shim
the roller blocks with shim stock.
Joints 4, 5 and 6. The installation of the main shaft bearings is
self explainatory. It is advisable to make some simple plugs to
install and remove these bearings, as acrewdriver blades and knives
are not good for the bearings or the parts. DO NOT hammer bearings
into place- press them in, on a drill press if an arbor press is not
available. Also, plan on having tooling for removal before ressing
in the bearing.
Installation of the small shaft bearings on the #6 joint and hand
will be discussed later in the section on main assembly. For the
present, its good enough to check that all the main drive shafts fit
together, and the arm structure assembles properly.
Shipment #2.
This consists of most of the purchased components and
critical assemblies. The only mechanical parts not included are
those with an electrical function. (Such as the drive gear on the #6
joint, and the #3 encoder or pot.]
You will probably want to assemble joint #1 first. Test fit
the motor assembly in the column. It should drop into place. It
should also slip into the drive tube. You will note that because of
the coaxial nature of the assembly, it is not possible to just fit
everything together and bolt it into place later. You must screw
things together while assembling arm.
The addition of an access hole in the side of the main column
allows for easier assembly because with it, you can assemble the #1
joint by dropping the motor assembly in place and putting in its
radial mounting screws. Then put in the bottom bearing. Now slide
in the drive tube assembly with the upper bearing and clamp ring
already installed . Tighten the clamp ring screws, and then put in
the drive tube screws thru the access hole in the side. At this
point you should decide on the orientation of the encoder zero
reference mark with respect to the socket cutout on the main tube.
To change it in the future, just unscrew the drive tube screws and
turn the head assembly until the proper orientation is reached.
Joint #2 is assembled in a manner similar to joint #1. Note
that the rear (motor end) bearing serves to center the motor mounting
plate also. The #2 motor assembly is not complete as the motor mount
plate is not part of the kit. You must first mount this plate to the
motor, and then bolt on the harmonic drive. It may be easier to get
the harmonic drive screws in place if you remove the three small
phillips head screws which hold on the diaphram assembly. The motor
drive system has a slip clutch on the hollow drive shaft. The slip
torque has been preset, so dont adjust the two locking nuts on the
drive shaft. The shaft thru the center of the motor comes from the
encoder. It is connected to the output thru the thin diaphram to
allow for some axial play during assembly and due to motor heating.
When assembling the unit, make sure that the diaphram is not
bottomed, but has free travel in both directions when the encoder
shaft set screw is tightened. Also remember that to remove the
encoder or get access to the motor brake( under the black motor end
bell at the encoder end), you must first loosen the encoder shaft set
screw. Only after doing this is it safe to remove the brake cover
screws and slip off the encoder and brake assembly. Mount the motor
assembly with the wires towards the base of the arm. Also shorten the
encoder shaft so that it doesnt protrude more than .1 inches past the
diaphram hub. Just grind or hacksaw offthe extra piece with
everything in place, as the encoder shaft is fragile and will snap
off easily if bent. The hollow motor shaft restricts the maximum
amount of bending to a safe level.
Joint #3
The motor is first mounted on the square tube (9-20). The
front motor bearing acts as the centering device too. Now wire up
the motor, brake and tach and slide the motor into the head assembly.
If it doesnt go all the way in, the encoder shaft on joint #2 sticks
out too far, so cut it off flush with the diaphram hub. The mounting
screws are socket head and the use of a stubby wrench is recommended
for easily working in the confined inside of the square tube. The
wires for the motor come out the notch in the flage on the #2 joint
tube. The boom is slipped in from the front (short end of the square
tube with rollers). The rack is mounted either on the top or bottom
side of the tube. Top side mounting is preferred because it keeps
the rack free of dirt. The backlash between the drive gear and rack
is adjusted by tightening the rack screws while pushing the rack
against the drive gear. Later, you will install the #3 joint encoder
in the hole in the rear of the guide tube. The encoder has its own
backlash adjustment. Glue a small strip of 1/4 inch thick rubber
onto the rear boom stop [L shaped piece], and slip an O ring onto the
front boom stop for a cushion.
Joint #4
In this assembly, the improtant thing to keep in mind is that
te motor armature is supported at the rear by a bearing and at the
front by the wave generator of the harmonic drive. The wave
generator is pre-mounted by Vicarm, but is not supported on its
outside diameter until the harmonic drive is completely assembled.
Thus it is not possible to test the motor separately. Also keep in
mind that the motor comes with a magnet keeper. This keeper must
never be removed, even for and instant without either the motor
armature fully in place, or an equivalent piece of magnetic steel
with a diameter equal to or greater than that of the armature in its
place. Otherwise the magnets will become demagnetized (it takes but
.0001 seconds to do this) and will have be recharged to regain full
performance. The rear motor bearing is held in place by the brake
disk and the center retainer on the ID. and by the rear housing and
outside retainer on the o.d. Some shimming may be necessary, in
addition to the spacer, to reduce end play to under .010 inches.
Install the brake field. The motor brush ring is slipped on by
tipping it and springing apart the brushes a bit so they clear the
tach drive gear. The motor is held together with six 4-40 screws.
Two short ones hold the magnet ring in place. Two medium length ones
hold the brush ring in place. Two long ones hold the rear case piece
in place. These last two should be flat head and countersunk so the
bearing retainer can slip fully into place. The harmonic drive
circular spline is screwed onto the front of the motor assy. with
socket head or fillister head screws. The flexspline is screwed to
the output shaft and the wire guide tube pressed into the hole in the
center of the output shaf. This tube guides the wire bundle through
the center of the motor. Test the assembly by pushing the flexspline
into the gap between the wave generator and the circular spline. It
should slip in easily. If it goes in hard it means that its not
correctly centered. Try it again. The harmonic drive works on the
principle that there are 2 more teeth on the circular spline (outer
ring) than on the flexspline (thin tubular piece). The flexspline is
deformed to the shape of an ellipse gy the wave generator (bearing
like thing). The ellipse contacts the circular spline at two points
and walks around slowly advancing as it does. The wave motion
proceeds at 72 times the actual motion, thus giving a gear reduction
of 72/1. It is possible to install the harmonic drive with the two
tooth difference on one side and no difference on the other. This
lopsided installation will cause the drive to be very rough and
require more power. This error can be prevented by trying the fit
several times. If it assembles easily, its right, if its hard to
push together, its wrong. Some wiggling and a bit of initial pushing
is the normal method of installation. The spacing between the motor
and the harmonic drive flexspline is not to critical,and is
determined by the design dimensions. There should be no interference
of screw heads when the output shaft is fully in place. To get the
output shaft fully in place pull it through the #4 joint housing with
some long screws in the output plate.
The tachometer is installed by slipping the unit with its
gear in thru the hole in the rear motor housing and applying a dab of
epoxy to hold it in place. The potentiometer mounting details will
be discussed later.