To measure surface finish, the two types of stylus instruments used are:

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RRB JE CBT 2 (Mechanical Engineering) ReExam Official Paper (Held On: 04 Jun, 2025)

Answer 1

Explanation:

Stylus Instruments

Surface finish is an essential attribute in manufacturing processes, as it directly influences the functionality, aesthetics, and performance of components. To measure surface finish accurately, stylus instruments are widely used. These instruments are classified into two main types: contact and non-contact instruments. Let us delve into the details of these types and understand why they are the correct choice for measuring surface finish.

Contact Stylus Instruments:

Contact stylus instruments work by physically touching the surface being measured. A stylus, usually made of a hard material like diamond, is drawn across the surface of the component. As the stylus moves, it traces the surface profile and records the variations in height and texture. These variations are then converted into electrical signals, which are processed to produce a graphical representation of the surface finish.

The key features of contact stylus instruments include:

High Accuracy: Contact stylus instruments provide highly accurate measurements, making them ideal for applications requiring precise surface finish characterization.
Wide Applicability: They are suitable for measuring various types of surfaces, including flat, curved, and intricate geometries.
Detailed Analysis: Contact instruments can measure parameters such as roughness, waviness, and form, providing a comprehensive surface profile.
Limitations: Despite their accuracy, contact stylus instruments may not be suitable for delicate or soft surfaces, as the physical contact can alter or damage the surface.

Non-contact Stylus Instruments:

Non-contact stylus instruments measure surface finish without physically touching the surface. These instruments use optical or laser-based technologies to scan the surface and capture its profile.

The key features of non-contact stylus instruments include:

No Physical Contact: Since there is no physical contact, non-contact instruments are ideal for measuring delicate, soft, or sensitive surfaces.
High Speed: Non-contact instruments can measure surface finish quickly, making them suitable for high-throughput manufacturing environments.
Versatility: They can measure surfaces with complex geometries, including hard-to-reach areas.
Limitations: Non-contact instruments may struggle with highly reflective or transparent surfaces, as optical interference can affect measurement accuracy.