This set of Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) focuses on “Pattern Fillets”.
1. In pattern making, the term used for rounding out of external edges of the pattern is called as a fillet.
a) True
b) False
View Answer
Explanation: The term used for rounding-out of external edges of the pattern is basically known as radii, and the rounding-out of internal corners of the pattern is known as the fillets on the pattern. Fillets are mainly provided to make uniform heating and cooling of the casting material and also for the less stress concentration.
2. Draft is generally provided to make a clearance between the pattern and the mould during pattern extraction.
a) True
b) False
View Answer
Explanation: Draft angles are normally included into the pattern design to make easy extraction of a pattern from the mould cavity. Draft angles are used in most of the pro¬cesses in which a pattern is withdrawn from the mould prior to pouring. Draft is very necessary to provide a clearance between the pattern and the mould during pattern extraction.
3. It is not necessary to avoid any sharp internal corners from casting design, as it causes very negligible problems.
a) True
b) False
View Answer
Explanation: Sharp internal corners on a casting design must be avoided whenever pos¬sible. The small volume of melt located in a casting’s internal corner quickly becomes superheated and transfer of heat becomes very difficult at this location, this further results in the formation of defects in the casting.
4. Lack of filleting of sharp corners in the casting design can cause hot spots in the casting.
a) True
b) False
View Answer
Explanation: When filleting of sharp corners is not done properly, then it causes an interruption in cooling of casting that basically creates localized areas that solidify very slowly than the rest of the part, this result into the formation of hot spots in the casting, which causes various defects in the casting.
5. Sharp corners in casting design may cause defects in the casting but it helps in strengthening of pattern material.
a) True
b) False
View Answer
Explanation: Sharp corners in casting design produce various defects in the castings and instead of strengthening, it makes the breaking of pattern material. Proper filleting reduces hot spots in the casting and eliminates defect from the casting. Fillets aid in the removal of the pattern from the mould and also strengthen the pattern.
6. Sharp corners in the casting design also produce the problem of sand inclusion in the castings.
a) True
b) False
View Answer
Explanation: Sharp corners in the casting design causes hot spots which produce many casting defects, such as hot tears, metal penetration, shrinkage, cracking and gas-related defects. And the sharp edges on the metal are also prone to breaking off and may cause sand inclu¬sions in the casting.
7. In horizontally parted moulds, a draft is required for vertical as well as for horizontal surfaces of a pattern.
a) True
b) False
View Answer
Explanation: The draft angle required on the pat¬tern mainly depends on the moulding process and the depth of pattern in the mould. Especially in horizontally parted moulds, only the vertical surfaces require a draft. Horizontal surfaces separate the pattern from the mould automatically during pattern removal.
8. In casting design, concave junctions are generally added to avoid the effect of sharp corners in the casting.
a) True
b) False
View Answer
Explanation: To avoid the problem of sharp corners, usually concave junction or fillet is added, where the two casting surfaces meet. This fillet mixes the two intersecting surfaces and modifies internal corner into a rounded corner. This ef¬fectively avoids the small volume of sand in the corner that reduces hot spots in the casting.
9. In pattern fillets, the size of a fillet is usually determined by its width.
a) True
b) False
View Answer
Explanation: In pattern fillets, the size of a fillet is generally determined by its radius, it is not measured by its width. Fillet sizes may vary, but it can be possible for a fillet to be too large. Proper filleting in the pattern makes the casting strong and more reliable that reduces the further cost of machining.
10. A very large fillet in casting design also may cause shrinkage defects in the casting.
a) True
b) False
View Answer
Explanation: In pattern fillets, a large fillet adds extra metal to the junction, which also may cause shrinkage problems due to the variations in the volume of casting. So the best design is to main¬tain uniform section thickness whenever possible in the casting design to keep the casting stable and strong.
11. Sharp internal corner of the casting also causes the misrun defect in the casting.
a) True
b) False
View Answer
Explanation: Sharp external corners can also produce casting defects. A misrun defect is basically caused by sharp external corners of the casting. External corners abruptly lose heat to the surrounding mould material and as a result, the corner might not fill completely that result into a misrun defect.
12. To avoid sharp external corners in casting design, rounding of external edges is done in pattern making that termed as radii.
a) True
b) False
View Answer
Explanation: A radius is provided that termed as radii for rounding of external edges of a pattern to aid in removing the pattern from the mould and eliminating the sharp external edges from the casting. It also makes the casting more aesthetically pleasing than casting with sharper corners.
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