Production Engineering (Manufacturing) MCQ Quiz - Objective Question with Answer for Production Engineering (Manufacturing) - Download Free PDF

Explanation:

Gear Hobbing

• Gear hobbing is a machining process used for cutting gears, splines, and sprockets. It is one of the most widely used methods in gear manufacturing and is especially suitable for producing high-quality gears with precision. The process involves the use of a specialized cutting tool called a hob, which is a cylindrical cutting tool with helical teeth. The hob and the workpiece (gear blank) rotate in a synchronized manner, allowing the hob to cut teeth into the blank progressively. The process is efficient, versatile, and suitable for mass production of gears.

Working Principle:

• In gear hobbing, the hob rotates at a high speed while the gear blank is mounted on a spindle and rotates at a specific speed ratio relative to the hob. The hob's teeth cut into the blank as the two rotate together, shaping the gear teeth. The synchronization between the hob and the blank ensures the correct tooth profile and spacing.
• The cutting operation in gear hobbing is continuous, which makes it faster and more economical compared to other gear manufacturing processes, such as gear shaping. The hob's design and rotational speed determine the gear's characteristics, such as the number of teeth, module, and pressure angle.

Applications of Gear Hobbing:

• Manufacturing spur gears, helical gears, and worm gears.
• Production of splines and sprockets.
• Used in the automotive, aerospace, and industrial machinery sectors for producing precision gears.
• Ideal for high-volume production due to its efficiency and speed.

Explanation:

Tool Maker’s Microscope:

• A Tool Maker’s Microscope is a precision instrument widely used in manufacturing and engineering industries for accurate measurements of small components, intricate profiles, and machined parts. This device is particularly valuable in quality control and design verification processes, ensuring that critical dimensions meet specified tolerances.
• The supporting column in a Tool Maker’s Microscope plays a vital role in its overall functionality. It is a structural component that contributes significantly to the stability and usability of the device.

Function of the Supporting Column:

• The supporting column in a Tool Maker’s Microscope is designed to provide a rigid and stable platform for securing the specimen or workpiece during measurement or inspection. By holding the specimen in place, the column ensures that the object remains stationary and aligned correctly relative to the microscope’s optical system. This stability is crucial for achieving high measurement accuracy and repeatability.
• Without a stable supporting column, even the slightest movement of the specimen could introduce errors in measurement or distort the observed image. The supporting column, therefore, directly contributes to the precision and reliability of the Tool Maker’s Microscope, making it an indispensable part of the instrument.

Key Features of the Supporting Column:

• It is made of robust and durable materials to withstand mechanical stresses and provide long-term stability.
• The column is designed to accommodate various specimen sizes and shapes, often featuring adjustable clamps or holders.
• It integrates seamlessly with other components of the microscope, such as the stage and optical system, ensuring proper alignment and functionality.

Explanation:

Lack of Penetration in Welding Defects

• Lack of penetration is a welding defect that occurs when the filler metal fails to completely penetrate into the root of the joint during the welding process. This defect is commonly encountered in welding operations and can significantly compromise the strength and integrity of the welded joint. It is critical to understand the causes, consequences, and preventive measures associated with this defect to ensure high-quality welds.
• Lack of penetration refers to the incomplete fusion or inadequate penetration of the filler metal into the root area of the joint. The root of the joint is the narrowest and deepest part of the weld, where the two pieces of base metal meet. Proper penetration ensures the welded joint is strong and can withstand mechanical stresses.

Causes of Lack of Penetration:

• Improper Welding Parameters: Using incorrect welding current, voltage, or travel speed can lead to insufficient heat generation, causing the filler metal to fail to penetrate into the root of the joint.
• Incorrect Joint Design: A poorly designed joint, such as an excessively narrow or deep root, can make it challenging for the filler metal to reach the root area.
• Insufficient Heat Input: Low heat input during welding can result in inadequate melting of the base metal, preventing the filler metal from penetrating properly.
• Improper Electrode Angle: Incorrect positioning or angling of the welding electrode can lead to incomplete penetration in the weld joint.
• Contaminated or Dirty Base Metal: Presence of impurities, grease, oil, or rust on the base metal can hinder the penetration of the filler metal into the root area.
• Inadequate Root Opening: A root opening that is too narrow prevents the filler metal from flowing into the joint effectively.

Consequences of Lack of Penetration:

• Reduced Joint Strength: The absence of adequate penetration results in weaker welds that are more prone to failure under mechanical stress.
• Structural Instability: Welded components with lack of penetration defects may compromise the structural integrity of the assembly, especially in critical applications.
• Crack Formation: Stress concentration at the root area can lead to the formation of cracks, further reducing the durability of the welded joint.
• Potential for Failure: Components with lack of penetration defects are at a higher risk of sudden failure, especially under dynamic or cyclic loading conditions.

Prevention of Lack of Penetration:

• Optimize Welding Parameters: Ensure proper selection of welding current, voltage, and travel speed to achieve sufficient heat input for complete penetration.
• Improve Joint Design: Design the joint with an appropriate root opening and bevel angles to facilitate effective penetration.
• Use Correct Electrode Angle: Position the welding electrode at the correct angle and maintain a consistent travel speed during welding.
• Clean the Base Metal: Thoroughly clean the base metal to remove any contaminants, rust, grease, or oil before welding.
• Perform Root Pass Welding: For thick joints, perform a root pass to ensure the filler metal penetrates deeply into the root area.
• Conduct Visual and Non-Destructive Testing: Inspect the welded joint using visual inspection or non-destructive testing techniques to identify lack of penetration defects.

Concept:

The angle formed by a sine bar is calculated using the formula:

\( \sin(\theta) = \frac{h}{L} \), where:

h = height difference between rollers, L = distance between centers of rollers

Given:

h = 30 mm, L = 60 mm

Calculation:

\( \sin(\theta) = \frac{30}{60} = 0.5 \Rightarrow \theta = \sin^{-1}(0.5) = 30^\circ \)

Hence, the angle formed is: 30°

Explanation:

Broaching Process:

• Broaching is a machining process that involves the use of a multi-toothed cutting tool called a broach to remove material from a workpiece. The process is designed to perform precision machining operations, such as shaping, sizing, or finishing, in a single pass. Broaching is particularly well-suited for applications where high accuracy, good surface finish, and complex profiles are required.
• The broaching process is performed by moving the broach either linearly (linear broaching) or rotationally (rotary broaching) relative to the workpiece. The broach consists of a series of cutting teeth arranged in a specific sequence, with each tooth progressively increasing in size. This arrangement allows the broach to remove material gradually, resulting in a smooth and accurate cut.

Key Features of Broaching:

• High Precision: Broaching provides excellent dimensional accuracy and surface finish, making it ideal for applications where tight tolerances are required.
• Complex Shapes: The process can produce intricate and non-circular shapes, such as splines, keyways, and gears, that are difficult to achieve with other machining methods.
• Efficiency: Broaching is a fast and efficient process, as it completes the machining operation in a single pass.
• Versatility: It can be used on various materials, including metals, plastics, and composites.
• Tool Design: The broach is designed with a gradual increase in tooth height, which minimizes cutting forces and reduces the risk of tool wear and breakage.

Types of Broaching:

• Internal Broaching: Used to create internal features, such as holes, keyways, and splines, within a workpiece.
• External Broaching: Used to machine external surfaces, such as flat, contoured, or cylindrical features.
• Linear Broaching: The broach moves linearly relative to the workpiece.
• Rotary Broaching: The broach rotates relative to the workpiece, often used for machining hexagonal or other non-circular holes.

Applications of Broaching:

• Manufacturing of gears, splines, and keyways.
• Creating complex profiles in automotive, aerospace, and industrial components.
• Producing high-precision parts for medical devices and other specialized industries.

Explanation:

Electrochemical Machining: 

In electrochemical machining, the metal is removed due to electrochemical action i.e. Ion displacement where the workpiece is made anode and the tool is made the cathode. A high current is passed between the tool and workpiece through the electrolyte. Metal is removed by the anodic dissolution and is carried away by the electrolyte.

The tool material used in ECM should have the following property

• It should have high electrical conductivity
• It should be easily machinable and it should have high stiffness
• Its corrosion resistance should be high.

The advantages of ECM include

• Complex shapes can be made accurately
• The surface finish is good due to atomic level dissolution
• Tool wear practically absent
• Its material removal rate is the highest.

The limitation of the Electro-Chemical Machining (ECM) process is the use of corrosive media as electrolytes makes it difficult to handle.

Concept:

• The Vernier principle states that two different scales are constructed on a single known length of line and the difference between them is taken for fine measurements.

Determining the least count of Vernier callipers:

In the Vernier calliper shown in Fig 

Calculation:

Given:

One main scale division (MSD) = 0.5 mm

24 divisions of main scale = 24 × 0.5 = 12 

One Vernier scale division (VSD) = 12/25 mm 

Least count = 1 MSD - 1 VSD

Concept:

Table speed in mm/minute = ft × Z × N

where, N = RPM, Z = no. of teeth, ft = Feed per tooth

Calculation:

Given:

Z = 10, N = 150 rpm, ft = ?, f_m = 400 mm/min

Table speed in mm/minute, 400 = 150 × 10 × ft

Explanation:

A casting defect is an irregularity in the metal casting process that is undesired.

Classification of casting defects is given as:

Explanation:

Nomenclature of butt and fillet weld:

Throat thickness: The distance between the junction of metals and the midpoint on the line joining the two toes.

Leg length: The distance between the junction of the metals and the point where the weld metal touches the base metal ‘toe’.

The length of the leg is the distance from the root of the weld to the toe of the weld.

The theoretical throat is the perpendicular distance between the root of the weld and the hypotenuse joining the two ends of the length. It is the shortest distance from the root to the face.

Root: The parts to be joined that are nearest together.

Root gap: It is the distance between the parts to be joined.

Root face: The surface formed by squaring off the root edge of the fusion face to avoid a sharp edge at the root.

Reinforcement: Metal deposited on the surface of the parent metal or the excess metal over the line joining the two toes.

The toe of weld: The point where the weld face joins the parent metal.

Weld face: The surface of a weld seen from the side from which the weld was made.

Root penetration: It is the projection of the root run at the bottom of the joint.

Explanation:

PROPERTIES OF MOULDING SAND:

Explanation:

Section:

• Sectional views are drawn to show the internal details of an object.
• The object is assumed to be cut on a plane.
• The surface produced by cutting an object at this plane is called a section.
• The surface which cuts the object at the section plane is shown hatched (a regular pattern) according to standard conventions.
• Sections are of many types:
  1. Full section
  2. Offset section
  3. Half section
  4. Revolved section
  5. Removed section
  6. Partial section, or broken section
  7. Auxillary section
  8. Aligned section. 
• The type of section to be adopted depends upon the shape of the object.

Half section:

• This is generally used for symmetrical objects.
• Two cutting planes at right angles to each other pass halfway through the view up to the centerline.
• Thus only one quarter is assumed to be removed.

Additional Information

Revolved section:

• It is used to show the cross-section shape of ribs, arms, spoke, etc. The section line is drawn by passing a cutting plane at right angles to the axis.
• This section is then revolved and drawn at the cutting plane axis on the main view. If the cross-section changes along the length, many revolved sections can be drawn.  
• ​​When the sectional view is shown within the object it is known as a Revolved section.

​

Removed section:

• It is similar to Revolved section, but instead of drawing the section on the view, it is drawn in a free space near the object along the centerline of the section.

Partial section:

• A section consisting of less than half a section is called a partial section. Note that here we use a broken line to indicate the division between the sectioned and unsectioned part. For this reason, a partial section is often called a Broken section.

​

Aligned section:

• An aligned section view/cut is a view created from a cutting profile defined from non-parallel planes. In order to include in a section a certain angled element, the cutting plane may be bent so as to pass through those features. The plane and feature are then imagined to be revolved into the original plane.

Full section:

• The cutting plane passes entirely through the object in a straight line. Thin objects like ribs, etc. are not hatched even if they are cut by the cutting plane along the axis.
• To see the internal features of an object that are not in a straight line, the cutting plane can be offset. Such a section is called the Offset section. The cutting plane can be inclined also.

Explanation:

Glazing: When a surface of the wheel develops a smooth and shining appearance, it is said to be glazed. This indicates that the wheel is blunt, i.e. the abrasive grains are not sharp.

• Glazing is caused by grinding hard materials on a wheel that has too hard a grade of bond. The abrasive particles become dull owing to cutting the hard material. The bond is too firm to allow them to break out. The wheel loses its cutting efficiency.
• Glazing of grinding wheel is more predominant in hard wheels with higher speeds. With softer wheels and relatively lower speeds, this effect is less prominent.

Explanation:

The soldering process is carried out generally in the temperature range of 180 – 250° C which is sufficient to melt the solder material. Most solders are alloys of lead and tin. Three commonly used alloys contain 60, 50, and 40% tin and all melt below 240°C.

In soldering, Solder Flux is used. Most commonly used soldering flux is as followed

• Ammonium chloride or rosin for soldering tin
• Hydrochloric acid and zinc chloride for soldering galvanized iron

Lancing - Creating a partial cut in the sheet, so that no material is removed. The material is left attached to be bent and form a shape, such as a tab, vent, or louver.

Parting - Separating a part from the remaining sheet, by punching away the material between parts.

Slitting - Cutting straight lines in the sheet. No scrap material is produced.

Notching - Punching the edge of a sheet, forming a notch in the shape of a portion of the punch.