27 real DFM & DFA questions from the Mechanical Design bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is Draft angle?
Junior
A.rib thickness of 50–60% of the nominal wall and height under three times the wall so ribs stiffen without sink marks on the outer face
B.taper on faces parallel to the pull direction, about 1–3° for die casting and 0.5–2° for injection moulding, so the part releases from the tool
C.putting the mould or die split on a flat plane away from cosmetic and sealing surfaces to limit flash and simplify tooling
D.ratio of the neutral axis distance from the inside face to the sheet thickness, typically 0.33–0.5, which CAD uses to compute the flat pattern
2. Which term means: "taper on faces parallel to the pull direction, about 1–3° for die casting and 0.5–2° for injection moulding, so the part releases from the tool"?
A.Draft angle — rib thickness of 50–60% of the nominal wall and height under three times the wall so ribs stiffen without sink marks on the outer face
B.Draft angle — taper on faces parallel to the pull direction, about 1–3° for die casting and 0.5–2° for injection moulding, so the part releases from the tool
C.Draft angle — arc length of the neutral axis through a bend, added to the flat lengths of the legs to obtain the flat blank size
D.Draft angle — keeping cast and moulded sections even so thick-thin junctions do not cause shrinkage porosity, sink marks or warpage
A.Uniform wall thickness — ratio of the neutral axis distance from the inside face to the sheet thickness, typically 0.33–0.5, which CAD uses to compute the flat pattern
B.Uniform wall thickness — rib thickness of 50–60% of the nominal wall and height under three times the wall so ribs stiffen without sink marks on the outer face
C.Uniform wall thickness — keeping cast and moulded sections even so thick-thin junctions do not cause shrinkage porosity, sink marks or warpage
D.Uniform wall thickness — putting the mould or die split on a flat plane away from cosmetic and sealing surfaces to limit flash and simplify tooling
A.Bend allowance — arc length of the neutral axis through a bend, added to the flat lengths of the legs to obtain the flat blank size
B.Bend allowance — putting the mould or die split on a flat plane away from cosmetic and sealing surfaces to limit flash and simplify tooling
C.Bend allowance — inside radius below which the outer fibre cracks, about one thickness for mild steel and larger for aluminium and hard tempers
D.Bend allowance — taper on faces parallel to the pull direction, about 1–3° for die casting and 0.5–2° for injection moulding, so the part releases from the tool
11. Which term means: "ratio of the neutral axis distance from the inside face to the sheet thickness, typically 0.33–0.5, which CAD uses to compute the flat pattern"?
A.K-factor — ratio of the neutral axis distance from the inside face to the sheet thickness, typically 0.33–0.5, which CAD uses to compute the flat pattern
B.K-factor — using standard drill sizes, avoiding full-depth threads in blind holes, keeping tool access and putting tight tolerances only on functional features
C.K-factor — arc length of the neutral axis through a bend, added to the flat lengths of the legs to obtain the flat blank size
D.K-factor — theoretical minimum part count times three seconds divided by the actual assembly time, a benchmark for assembly efficiency
14. Which term means: "inside radius below which the outer fibre cracks, about one thickness for mild steel and larger for aluminium and hard tempers"?
A.Minimum bend radius — arc length of the neutral axis through a bend, added to the flat lengths of the legs to obtain the flat blank size
B.Minimum bend radius — using standard drill sizes, avoiding full-depth threads in blind holes, keeping tool access and putting tight tolerances only on functional features
C.Minimum bend radius — keeping cast and moulded sections even so thick-thin junctions do not cause shrinkage porosity, sink marks or warpage
D.Minimum bend radius — inside radius below which the outer fibre cracks, about one thickness for mild steel and larger for aluminium and hard tempers
A.Parting line placement — ratio of the neutral axis distance from the inside face to the sheet thickness, typically 0.33–0.5, which CAD uses to compute the flat pattern
B.Parting line placement — arc length of the neutral axis through a bend, added to the flat lengths of the legs to obtain the flat blank size
C.Parting line placement — putting the mould or die split on a flat plane away from cosmetic and sealing surfaces to limit flash and simplify tooling
D.Parting line placement — using standard drill sizes, avoiding full-depth threads in blind holes, keeping tool access and putting tight tolerances only on functional features
20. Which term means: "rib thickness of 50–60% of the nominal wall and height under three times the wall so ribs stiffen without sink marks on the outer face"?
A.Rib design in plastics — arc length of the neutral axis through a bend, added to the flat lengths of the legs to obtain the flat blank size
B.Rib design in plastics — rib thickness of 50–60% of the nominal wall and height under three times the wall so ribs stiffen without sink marks on the outer face
C.Rib design in plastics — inside radius below which the outer fibre cracks, about one thickness for mild steel and larger for aluminium and hard tempers
D.Rib design in plastics — keeping cast and moulded sections even so thick-thin junctions do not cause shrinkage porosity, sink marks or warpage
23. Which term means: "using standard drill sizes, avoiding full-depth threads in blind holes, keeping tool access and putting tight tolerances only on functional features"?
A.Design for machining — using standard drill sizes, avoiding full-depth threads in blind holes, keeping tool access and putting tight tolerances only on functional features
B.Design for machining — theoretical minimum part count times three seconds divided by the actual assembly time, a benchmark for assembly efficiency
C.Design for machining — taper on faces parallel to the pull direction, about 1–3° for die casting and 0.5–2° for injection moulding, so the part releases from the tool
D.Design for machining — rib thickness of 50–60% of the nominal wall and height under three times the wall so ribs stiffen without sink marks on the outer face
A.Boothroyd-Dewhurst DFA index — using standard drill sizes, avoiding full-depth threads in blind holes, keeping tool access and putting tight tolerances only on functional features
B.Boothroyd-Dewhurst DFA index — taper on faces parallel to the pull direction, about 1–3° for die casting and 0.5–2° for injection moulding, so the part releases from the tool
C.Boothroyd-Dewhurst DFA index — inside radius below which the outer fibre cracks, about one thickness for mild steel and larger for aluminium and hard tempers
D.Boothroyd-Dewhurst DFA index — theoretical minimum part count times three seconds divided by the actual assembly time, a benchmark for assembly efficiency
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