Manufacturing Processes Multiple Choice Questions on “Roll Forming – 3”.
1. During roll forming, a flat strip is passed number of times through the rollers.
a) True
b) False
Answer: a
Clarification: In roll forming, a flat strip is gradually formed to the finished shape. The forming is almost exclusively accomplished by rotating contoured rolls while the material passes through the mill.
2. Which of following is necessary in order to have a good set of rolls?
a) Short horizontal distances
b) Small lead-in flanges
c) A smooth flow of material
d) Less number of forming passes
Answer: c
Clarification: The probability of having a good set of rolls is to follow few rules:
(1) Envision a smooth flow of material,
(2) Do not be skimpy with the number of forming passes,
(3) Avoid too short horizontal distances and too small lead-in flanges.
3. Which of the following is true in case of “too quick” forming (too few passes)?
a) It makes the tooling and the process uneconomical
b) It makes process easier
c) It distorts the product
d) Eliminate the need of a skilled operator
Answer: c
Clarification: “Too quick” forming (too few passes) will distort the product because of the unacceptable level of stresses generated in the metal. On the other hand, too many passes will make the tooling and the process uneconomical.
4. What is “leg length” or “leg ”?
a) The maximum vertical dimension of the profile
b) Total length of the product
c) Excess length of the product
d) Maximum of the section
Answer: a
Clarification: The depth of the section, also called as “leg length” or “leg ”, is the maximum vertical dimension of the profile as it exits from the last pass. Sometimes it called as “depth of corrugation”.
5. In case of “U” channel/ section, the length of travel of the edge of the strip (effective length of the strip) ‘s’, travelling in a helical pattern having initial length ‘l’ is given by_____
a) l2 = s2 + c2
b) c2 = l2 + s2
c) s2 = l2 + c2
d) s = l2 + c2
Answer: c
Clarification: As we know, edge of the strip to be bend travels in a helical path, the length of the strip after bending is given by formula:
s2 = l2 + c2, where, s = final length &
l = initial length.
6. What will be the elongation if a 1in high section is formed in four passes in a mill having a horizontal distance (between passes) of 14in?
a) 0.04%
b) 0.16%
c) 0.63%
d) 0.50%
Answer: a
Clarification: Here, h = 1in; number of passes = 4 and each of length = 14in
Therefore, l = 4 * 14 = 56.
Therefore,
Elongation, e = (56.022 – 56)/ 56
= 0.0004 = 0.04%.