There are limits to the dimensions and tolerances that can be
machined along the plane of the metal sheet, since etchants used
in the photochemical machining process concurrently etch metals
laterally and vertically through the thickness (T) of the sheet.
Because the metal at the surface of a sheet is exposed to
etchant longer than the metal at the center of the sheet, the
surface of a part etches laterally more than metal at the
center. The following planar dimensions are related directly to
the thickness of that sheet. Hole Size/ Slot Width The smallest
hole diameter (D) or slot width that can be produced by the
Fotofab process, as a general rule, is 1 times the metal
thickness. The minimum practical diameter or slot width that can
be machined is .004 inch ( 0.102 mm). Spacing of metal between
the holes and/or slots in a design is not an issue using
photochemical machining. However, when a part contains holes
and/or slots that are spaced closely together, such as with a
fine resolution screen or encoder dis