(SEM VII) THEORY EXAMINATION 2024-25 ADDITIVE MANUFACTURING

SECTION A

(2 × 10 = 20 Marks)

a) Define additive manufacturing

Additive manufacturing is a manufacturing process in which a three-dimensional object is created by adding material layer by layer based on a digital model. Unlike conventional subtractive manufacturing, material is deposited only where required, resulting in reduced material waste and greater design flexibility.

b) Differences between additive manufacturing and CNC machining

Additive manufacturing builds components by depositing material layer by layer, whereas CNC machining removes material from a solid block to achieve the desired shape. Additive manufacturing allows complex geometries and internal features, while CNC machining offers higher surface finish and dimensional accuracy for simple geometries.

c) Significance of prototyping in additive manufacturing

Prototyping in additive manufacturing allows rapid creation of physical models directly from CAD data. It helps designers evaluate form, fit, and function at an early stage, reduces development time, lowers cost, and enables quick design iterations before mass production.

d) Processes used in vat photo-polymerization

Vat photo-polymerization involves curing liquid photopolymer resin using light. Common processes include stereolithography (SLA) and digital light processing (DLP), where ultraviolet light selectively solidifies the resin layer by layer.

e) Powder fusion mechanisms

Powder fusion mechanisms involve selectively fusing powder particles using a heat source such as a laser or electron beam. The energy source melts or sinters the powder to form solid layers, as seen in selective laser sintering and electron beam melting processes.

f) Importance of CAD in additive manufacturing

Computer-Aided Design plays a crucial role in additive manufacturing by enabling the creation of accurate digital models that guide the printing process. CAD models define geometry, tolerances, and features, ensuring precise control over the final product.

g) Small batch production in additive manufacturing

Additive manufacturing supports small batch production by eliminating the need for expensive tooling. It allows economical production of limited quantities with customization, making it ideal for prototypes, spare parts, and specialized components.

h) Applications of aerosol printing

Aerosol printing is used in applications such as printed electronics, sensors, antennas, and biomedical devices. It enables precise deposition of functional materials on various substrates with high resolution.

i) Challenges associated with STL file formats

STL file formats present challenges such as loss of geometric accuracy, inability to represent color or material properties, and errors like gaps or non-manifold edges that require repair before printing.

j) Future trends in additive manufacturing

Future trends in additive manufacturing include multi-material printing, large-scale manufacturing, integration with artificial intelligence, hybrid manufacturing systems, and wider adoption in industrial production.

SECTION B

(Attempt any three – answers provided for all)

2(a) Types of additive manufacturing technologies

Additive manufacturing technologies include material extrusion, vat photo-polymerization, powder bed fusion, material jetting, binder jetting, and directed energy deposition. Each technology differs in material usage, energy source, accuracy, and applications, ranging from plastic prototypes to metal aerospace components.

2(b) Generalized additive manufacturing process chain

The additive manufacturing process chain begins with CAD model creation, followed by file conversion, slicing, and process planning. The actual printing process builds the part layer by layer, after which post-processing steps such as cleaning, curing, and finishing are performed to achieve desired properties.

2(c) Significance of powder handling in powder bed fusion

Proper powder handling is essential in powder bed fusion processes to ensure uniform layer deposition, consistent material properties, and defect-free parts. Poor powder quality can lead to porosity, contamination, and reduced mechanical performance.

2(d) Working of material jetting systems

Material jetting systems work by depositing droplets of build material through inkjet-like nozzles onto a build platform. The deposited material is cured using ultraviolet light, allowing high accuracy and multi-material printing, commonly used in PolyJet technology.

2(e) Quality assurance challenges and solutions in additive manufacturing

Quality assurance in additive manufacturing faces challenges such as process variability, material inconsistencies, and lack of standardization. Solutions include in-situ monitoring, process control systems, standardized testing methods, and post-process inspection techniques.

 SECTION C

3(a) Working principle of stereolithography

Stereolithography operates by curing a liquid photopolymer resin using a focused ultraviolet laser. The laser traces the cross-section of the part on the resin surface, solidifying it layer by layer. After each layer, the platform moves, allowing the next layer to be formed until the complete object is built.

3(b) Extrusion-based additive manufacturing and path control

Extrusion-based additive manufacturing involves pushing molten material through a nozzle and depositing it layer by layer. Path control mechanisms determine nozzle movement, extrusion rate, and layer thickness, ensuring dimensional accuracy and structural integrity.

4(a) Significance of engineering design rules in additive manufacturing

Engineering design rules in additive manufacturing guide designers in creating printable and functional parts. These rules address factors such as wall thickness, support structures, overhangs, and orientation, helping to minimize defects and improve performance.

4(b) Role of intellectual property in additive manufacturing

Intellectual property plays a vital role in protecting designs, processes, and innovations in additive manufacturing. It ensures fair competition, encourages innovation, and addresses challenges related to digital design sharing and unauthorized replication.

5(a) Directed Energy Deposition processes and applications

Directed Energy Deposition involves feeding metal powder or wire into a melt pool created by a focused energy source. It is widely used for repair, cladding, and fabrication of large components in aerospace, automotive, and defense industries.

5(b) Hybrid systems in additive manufacturing

Hybrid additive manufacturing systems combine additive and subtractive processes in a single machine. These systems improve surface finish, accuracy, and functionality but face challenges related to system complexity and cost.

6(a) Applications of additive manufacturing in aerospace and biomedical industries

In aerospace, additive manufacturing is used for lightweight components, complex structures, and rapid prototyping. In biomedical fields, it enables patient-specific implants, prosthetics, and tissue scaffolds with high customization.

6(b) Customized mass production in additive manufacturing

Customized mass production combines personalization with scalable manufacturing. Additive manufacturing supports this concept by enabling flexible production without tooling changes, making it suitable for consumer products and healthcare applications.

7(a) Software issues beyond STL file manipulation

Beyond STL manipulation, software challenges include build preparation, process simulation, error detection, data security, and integration with manufacturing systems. Advanced software tools are required for efficient workflow management.

7(b) Eight steps in additive manufacturing

The additive manufacturing process involves conceptual design, CAD modeling, file conversion, slicing, machine setup, printing, post-processing, and inspection. These steps may vary depending on the machine type and material used.