Man Pro exam 2

1. Why is surface finish of rolled products better in Cold rolling than in Hot rolling?

Cold rolling has little oxidation or scale, giving a smoother surface and better dimensional accuracy than hot rolling.

2. What is the difference between Blooms, Slabs and Billets?

Blooms are large square or rectangular sections, slabs are wide and flat sections, and billets are smaller square or round sections.

3. What is Forward Slip? Why it is important?

Forward slip is when metal exits the rolls faster than the roll surface speed. It is important for determining final material speed and production rate.

4. Define Neutral Point and Draft in Rolling!

The neutral point is where strip velocity equals roll surface velocity. Draft is the reduction in thickness, d = h0 - hf.

5. Calculate number of rolling passes to deform a plate thickness of 8 mm to 5 mm. Coefficient of friction is 0.15 and roller diameter 500 mm.

Maximum draft = mu^2 R = (0.15)^2(250) = 5.625 mm. Required reduction is 3 mm, so 1 pass is required.

6. How does Rolling differs from Extrusion process!

Rolling reduces thickness by passing material between rotating rolls. Extrusion pushes material through a die to make a constant cross section.

7. Explain the difference between Extrusion and Wire Drawing processes!

Extrusion pushes material through a die using compressive force. Wire drawing pulls material through a die using tensile force.

8. What is the purpose of dummy blocks in Extrusion process?

A dummy block separates the ram from the hot billet. It protects the ram and helps keep contaminated billet material out of the product.

9. What is Impact Extrusion? What are applications?

Impact extrusion uses a high-speed punch to force metal through or around a die. It is used for cans, tubes, containers, and collapsible metal tubes.

10. In an extrusion process Aluminium round billet of 150 mm diameter and 500 mm long is deformed into a channel shape product of 1500 mm long. What is the cross section of the channel produced?

Using volume conservation, A1L1 = A2L2. The channel cross-sectional area is about 5890.5 mm^2.

11. Compare the processes Sizing and Coining!

Sizing makes small dimensional corrections to improve accuracy. Coining uses high pressure to create precise shapes or surface details.

12. Compare the processes Coining and Embossing!

Coining uses high compressive force to form detailed features. Embossing creates raised or recessed patterns with little change in thickness.

13. What is the difference between Cold, Worm and Hot forging?

Cold forging is below recrystallization temperature, warm forging is at an intermediate temperature, and hot forging is above recrystallization temperature.

14. What are the defects in flat rolling?

Common defects are wavy edges, edge cracks, center cracks, and alligatoring. They are often caused by uneven deformation or improper rolling conditions.

15. How Seamless tubes produced?

A solid round billet is heated and pierced through its center. The hollow billet is then rolled and stretched to the required diameter and wall thickness.

16. What are the factors affecting Rolling Forces?

Rolling force depends on material strength, thickness reduction, friction, roll diameter, and strip width. Temperature, speed, and lubrication also affect it.

17. What are the advantages and disadvantages of Isothermal forging?

It improves material flow, reduces force, and allows complex shapes. It is slower and more expensive because the dies must be heated and controlled.

18. What is Upset forging? What are applications?

Upset forging compresses the length of a workpiece to increase its cross-sectional area. It is used for bolt heads, screws, nails, and valve heads.

19. How to differentiate whether a part is produced by Forging or Casting?

Forged parts usually show directional grain flow and high strength. Cast parts may show porosity, casting marks, and a more random grain structure.

20. What is the difference between Punching and Blanking?

In punching, the removed piece is scrap and the hole is desired. In blanking, the removed piece is the desired part.

21. What is Spring Back and how to take care of it in Bending process?

Spring back is elastic recovery after the bending force is removed. It can be reduced by overbending, bottoming, or coining.

22. Differentiate Compound Dies and Progressive Dies!

A compound die performs multiple cutting operations at one station in one stroke. A progressive die performs different operations at several stations.

23. What are the factors on which Recrystallization temperatures depend?

Recrystallization temperature depends on cold work, material composition, grain size, impurities, and heating time. More cold work generally lowers it.

24. What are the various applications of Metal Spinning?

Metal spinning is used for bowls, cones, funnels, cookware, reflectors, pressure vessels, and nose cones. It is mainly used for axisymmetric hollow parts.

25. What are typical stages of a Deep Drawing process?

A blank is held by a blank holder and pushed into a die by a punch. Redrawing, ironing, and trimming may follow to reach the final shape.

26. What are the defects in Deep Drawing?

Common defects are wrinkling, tearing, earing, excessive thinning, and surface scratches. They depend on force, friction, material, and die design.

27. Compare V-bending and Edge bending!

V-bending pushes the sheet into a V-shaped die. Edge bending holds the sheet and bends its edge around a die, often for flanges or 90-degree bends.

28. What are Trimming and Shaving in sheet metal cutting ?

Trimming removes unwanted material from the edge of a formed part. Shaving removes a thin layer from a cut edge to improve accuracy and finish.

29. What are methods of reducing cutting forces in press cutting operations? Explain!

Use a shear angle or stagger punches so cutting happens progressively. Proper clearance and sharp tools also reduce peak cutting force.

30. Explain Scrap-Strip layout in Blanking and it’s advantages!

A scrap-strip layout arranges blanks on a strip and controls the remaining scrap. A good layout reduces waste, lowers cost, and improves feeding.