Manufacturing Practices (BT-106) - Important Questions

Define "jig" and "fixture". Explain in detail the differences between a jig and a fixture with suitable examples. Describe the essential functions and advantages of fixtures in production. List and explain the primary design considerations for a drilling fixture.

A press shop is to blank out a flat component from a sheet. Explain the procedure to calculate the required blanking (shearing) force. Use the standard shearing force relation and clearly define each term. Calculate the blanking force for a component having a total cutting/perimeter length of $l$, sheet thickness $t$, and the shear strength of the material $\tau$. Present the formula and describe how to include a safety factor and press capacity selection.

What is the clearance in blanking and piercing operations? Explain its significance and describe the effects of under clearance and over clearance on tool wear, burr formation and dimensional accuracy. Provide recommended clearance ranges for ductile and brittle sheet materials (qualitatively).

Describe the various press tool operations used in sheet metal working: blanking, piercing, trimming, shaving, forming, bending, drawing and coining. For each operation state its purpose, typical tool features and key differences from the others.

Explain the deep drawing process for producing a cylindrical cup. Describe the stages of deep drawing, factors affecting drawability, limitations (like wrinkling and tearing), and methods to improve drawability. Define the term "limiting drawing ratio" and explain its practical significance (no numeric derivation required).

Explain the concept and working of a progressive die. Draw a schematic showing the sequence of stations in a progressive die and explain operations commonly carried out at each station. List advantages and application areas of progressive dies compared to single-stroke dies.

Discuss the factors to be considered while selecting a suitable press machine for a given blanking/piercing job. Using the shearing force relation $$F = \tau\, t\, l$$ explain how to calculate the required tonnage. Explain how stroke length and number of strokes per minute influence press selection.

Discuss the commonly used materials for press tool components and their heat treatments. Explain why tool steels like D2 and H13 are preferred for dies and punches. Mention the properties required for tool materials used in blanking and forming operations.

List and explain important safety precautions to be followed while operating presses and press tools. Also describe routine maintenance practices for press tools and dies to ensure long life and consistent part quality.

Describe the detailed design procedure for a drilling fixture for locating, supporting and clamping a workpiece for multi-hole drilling. Include the selection and layout of locating elements, clamp types, drill bushings (purpose and material), and considerations for repeatability and interchangeability. Explain with a labeled sketch of a typical drilling fixture.

What is springback in sheet metal bending? Explain the factors influencing springback and describe methods used in tool design and process planning to compensate for springback to achieve desired bend angles and dimensions.