Cam type selection: When a follower's motion lies in a plane parallel to the camshaft axis (i.e., the follower translates parallel to the shaft), a cylindrical/barrel cam—not merely any “irregular cam”—is typically employed. Evaluate whether the statement “An irregular cam must be used” is correct.

Introduction / Context:
Cams come in several forms: disk (plate) cams with radial followers, cylindrical or barrel cams for followers moving parallel to the shaft, and end cams, among others. The prompt asserts that an “irregular cam” must be used when the follower moves in a plane parallel to the camshaft. We clarify the specific cam type required.

Given Data / Assumptions:

• Follower motion direction is parallel to the camshaft axis.
• Design seeks repeatable displacement per revolution.
• Standard cam taxonomy applies (disk vs cylindrical/barrel).

Concept / Approach:
For axial (parallel) follower motion, the canonical solution is a cylindrical or barrel cam with a helical groove/profile controlling the follower. Calling it simply “irregular” is imprecise; many cams are “irregular” in profile but differ in geometry and follower direction. The correct classification matters for drafting and manufacturing.

Step-by-Step Solution:
1) Identify follower direction relative to cam axis (parallel).2) Select cylindrical/barrel cam geometry to guide axial motion with a groove.3) Synthesize the groove from the displacement diagram.4) Dimension groove path and follower guidance features accordingly.

Verification / Alternative check:
Mechanism handbooks list barrel cams for axial followers; disk cams serve radial/offset followers primarily.

Why Other Options Are Wrong:
“Correct”: Too vague; does not specify the proper cam type.“Disk cams only”: Disk cams are not suited to followers moving parallel to the shaft without additional linkages.“Only gears”: Gears transmit rotation; cams generate programmed displacement.

Common Pitfalls:
Mislabeling cam types; under-dimensioning groove width and follower diameter; ignoring wear from high contact stresses in barrel cams.

Final Answer:
Incorrect