3) Built-in metering scales
The machine utilizes standard linear scales built into
the cross-slides plus projection screens for viewing the standard scale
graduation at high magnification. The associated micrometer drum makes
it possible to read positions to 0. 001 mm. directly. In addition, thereare
external auxiliary scales for coarse reference.
4) Large thermal inertia
The large mass of the machine will serve to minimize
the effects of ambient temperature variations and operator proximity.
5) The last and perhaps the most important features, such
as structural design, optimum stabilization of critical components, and
long service life, have been developed and proven over many years.
It is estimated that the total error from 1, 2, and 3 above
will not exceed 0. 01 mm. With a maximum allowable total error of 0.05
mm. in the measurement, the operator can make and record measure-
ments at optimum speed.
Drive System
1. Mechanical Requirements
The major requirements for the table drive system are a peak
travel rate of at least 2. 5 inches per second; a fine positioning control
that will enable the operator to position the photographic plate to better
than 0.05 mm. (backlash must be a minimum); and means to prevent ex-
cessive acceleration, excessive velocity, and possible damage.
Since simplicity, speed, and precision are so important to the
overall operation of the plate previewer, hand drives, even though adequate,
are not desirable. Simple control of power drives should be incorporated.
2. Mechanical Specifications and Description
Both the x and y table motions will be power driven by variable
speed motors. The operator table drive control will be of the "joy-stick"
type with table motion, speed and direction being coordinated with "joy-
Stick" displacement. With the "joy-stick" in the neutral or hands off pos-
tion, both tables will be clamped with respect to their guide ways. Un-
clamping of each table will be automatically accomplished when the "joy-
stick" is displaced with a component in a direction parallel to the desired
table motion axis. "Joy-stick" displacement at 45° to the table axes will
