DFM & DFA interview questions

1. 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
2. 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
3. C.putting the mould or die split on a flat plane away from cosmetic and sealing surfaces to limit flash and simplify tooling
4. 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

Answer + AI explanation with Pro

1. A.Parting line placement
2. B.Boothroyd-Dewhurst DFA index
3. C.Draft angle
4. D.Uniform wall thickness

Answer + AI explanation with Pro

1. 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
2. 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
3. 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
4. D.Draft angle — keeping cast and moulded sections even so thick-thin junctions do not cause shrinkage porosity, sink marks or warpage

Answer + AI explanation with Pro

1. A.keeping cast and moulded sections even so thick-thin junctions do not cause shrinkage porosity, sink marks or warpage
2. 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
3. C.using standard drill sizes, avoiding full-depth threads in blind holes, keeping tool access and putting tight tolerances only on functional features
4. 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

Answer + AI explanation with Pro

1. A.Uniform wall thickness
2. B.Draft angle
3. C.Parting line placement
4. D.K-factor

Answer + AI explanation with Pro

1. 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
2. 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
3. C.Uniform wall thickness — keeping cast and moulded sections even so thick-thin junctions do not cause shrinkage porosity, sink marks or warpage
4. 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

Answer + AI explanation with Pro

1. A.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
2. B.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
3. C.using standard drill sizes, avoiding full-depth threads in blind holes, keeping tool access and putting tight tolerances only on functional features
4. D.arc length of the neutral axis through a bend, added to the flat lengths of the legs to obtain the flat blank size

Answer + AI explanation with Pro

1. A.Boothroyd-Dewhurst DFA index
2. B.Bend allowance
3. C.Draft angle
4. D.K-factor

Answer + AI explanation with Pro

1. 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
2. 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
3. C.Bend allowance — inside radius below which the outer fibre cracks, about one thickness for mild steel and larger for aluminium and hard tempers
4. 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

Answer + AI explanation with Pro

1. 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
2. B.keeping cast and moulded sections even so thick-thin junctions do not cause shrinkage porosity, sink marks or warpage
3. C.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
4. D.theoretical minimum part count times three seconds divided by the actual assembly time, a benchmark for assembly efficiency

Answer + AI explanation with Pro

1. A.Uniform wall thickness
2. B.Parting line placement
3. C.Boothroyd-Dewhurst DFA index
4. D.K-factor

Answer + AI explanation with Pro

1. 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
2. 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
3. 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
4. D.K-factor — theoretical minimum part count times three seconds divided by the actual assembly time, a benchmark for assembly efficiency

Answer + AI explanation with Pro

1. A.inside radius below which the outer fibre cracks, about one thickness for mild steel and larger for aluminium and hard tempers
2. B.keeping cast and moulded sections even so thick-thin junctions do not cause shrinkage porosity, sink marks or warpage
3. C.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
4. D.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

Answer + AI explanation with Pro

1. A.Minimum bend radius
2. B.Rib design in plastics
3. C.Boothroyd-Dewhurst DFA index
4. D.K-factor

Answer + AI explanation with Pro

1. 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
2. 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
3. C.Minimum bend radius — keeping cast and moulded sections even so thick-thin junctions do not cause shrinkage porosity, sink marks or warpage
4. 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

Answer + AI explanation with Pro

1. A.keeping cast and moulded sections even so thick-thin junctions do not cause shrinkage porosity, sink marks or warpage
2. 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
3. C.putting the mould or die split on a flat plane away from cosmetic and sealing surfaces to limit flash and simplify tooling
4. D.inside radius below which the outer fibre cracks, about one thickness for mild steel and larger for aluminium and hard tempers

Answer + AI explanation with Pro

1. A.Parting line placement
2. B.Design for machining
3. C.Uniform wall thickness
4. D.Draft angle

Answer + AI explanation with Pro

1. 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
2. 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
3. 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
4. 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

Answer + AI explanation with Pro

1. A.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. B.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
3. C.inside radius below which the outer fibre cracks, about one thickness for mild steel and larger for aluminium and hard tempers
4. D.using standard drill sizes, avoiding full-depth threads in blind holes, keeping tool access and putting tight tolerances only on functional features

Answer + AI explanation with Pro

1. A.Boothroyd-Dewhurst DFA index
2. B.Parting line placement
3. C.Rib design in plastics
4. D.Draft angle

Answer + AI explanation with Pro

1. 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
2. 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
3. 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
4. D.Rib design in plastics — keeping cast and moulded sections even so thick-thin junctions do not cause shrinkage porosity, sink marks or warpage

Answer + AI explanation with Pro

1. A.putting the mould or die split on a flat plane away from cosmetic and sealing surfaces to limit flash and simplify tooling
2. B.using standard drill sizes, avoiding full-depth threads in blind holes, keeping tool access and putting tight tolerances only on functional features
3. C.inside radius below which the outer fibre cracks, about one thickness for mild steel and larger for aluminium and hard tempers
4. D.theoretical minimum part count times three seconds divided by the actual assembly time, a benchmark for assembly efficiency

Answer + AI explanation with Pro

1. A.Boothroyd-Dewhurst DFA index
2. B.Bend allowance
3. C.Design for machining
4. D.Draft angle

Answer + AI explanation with Pro

1. 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
2. B.Design for machining — theoretical minimum part count times three seconds divided by the actual assembly time, a benchmark for assembly efficiency
3. 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
4. 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

Answer + AI explanation with Pro

1. A.theoretical minimum part count times three seconds divided by the actual assembly time, a benchmark for assembly efficiency
2. B.arc length of the neutral axis through a bend, added to the flat lengths of the legs to obtain the flat blank size
3. C.using standard drill sizes, avoiding full-depth threads in blind holes, keeping tool access and putting tight tolerances only on functional features
4. 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

Answer + AI explanation with Pro

1. A.Parting line placement
2. B.K-factor
3. C.Design for machining
4. D.Boothroyd-Dewhurst DFA index

Answer + AI explanation with Pro

1. 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
2. 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
3. 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
4. D.Boothroyd-Dewhurst DFA index — theoretical minimum part count times three seconds divided by the actual assembly time, a benchmark for assembly efficiency

Answer + AI explanation with Pro