跟读练习: How Things Are Made | An Animated Introduction to Manufacturing Processes - 通过视频学习英语口语
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Do you ever wonder how amorphous lumps of material are turned into the everyday products which surround us?
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Let's find out.
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In this video, we're going to talk about manufacturing processes.
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There are six main categories of manufacturing processes, which are forming, casting, molding,
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joining, machining, and additive manufacturing.
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Each one of these categories contains a large number of different manufacturing techniques.
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There are a lot of different factors which need to be considered when selecting the right manufacturing process.
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This includes the material you are working with, the geometry of the object, the number of parts you are producing,
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tool and material costs, and required levels of automation to name just a few.
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Let's look through each of the six categories in detail.
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Forming involves applying forces or pressure and plastically deforming the material to produce the desired shape.
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It is typically used for metals.
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Most forming processes can be done when the metal is either above or below its recrystallization temperature.
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This is known as hot or cold working.
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Hot working makes it easier to plastically deform the metal, but cold working causes strain hardening, which increases the strength of the material.
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Three common forming processes are forging, rolling, and extrusion.
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Modern forging is done using machines.
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In closed die, or impression forging, the metal is placed between top and bottom closed dies.
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Repeated strokes from the hammer are used to cause the metal to flow into the shape of the dies.
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Objects produced using forging can have improved mechanical properties compared to objects which are cast,
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but it can be difficult to achieve tight tolerances using forging, and the required equipment can be expensive.
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Extrusion is a continuous process which involves placing hot metal in a chamber
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and using a ram to force it through a die, producing a long object with a constant cross -section.
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Extrusion provides an excellent surface finish and can achieve very tight tolerances, but it is only suitable for producing two -dimensional shapes.
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Rolling is probably the most commonly used forming process.
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Plus, it involves passing metal between two or more rollers, which apply pressure and reduce thickness.
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More complex products like I -beams can also be manufactured by rolling.
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Rolling can result in improved mechanical properties and can be automated, which makes it good for large -scale production
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but tooling costs tend to be high
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and it can't be used to produce very complex shapes let's move on to the next category of manufacturing processes casting
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casting involves pouring molten metal into a mold
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and allowing it to solidify it is what we call a
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primary shaping process a secondary process such as machining is typically needed to achieve the desired surface finish.
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Like forming, casting is most commonly used for metals.
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Three common types of casting are die casting, sand casting, and investment casting.
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In die casting, molten metal is forced into reusable metal dies at high pressure.
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Once the molten metal has solidified, it is removed from the mold.
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die casting is mostly used for non -ferrous metals like aluminum
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and zinc which have low melting temperatures it provides an excellent surface finish
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and can achieve very tight tolerances but startup costs tend to be high
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so it is only really suitable for large production runs
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in sand casting a pattern is used to create a single -use mold from damp sand
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the sand is typically contained in two mold boxes called the cope and the drag
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molten metal is poured into the mold through a channel formed in the sand When the metal has solidified, the cast object can be removed from the sand.
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Sand casting can be used for a wide range of metals, including those with high melting temperatures.
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It can produce large and complex parts, and initial costs are very low, making it good for small production runs.
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However, it provides a poor surface finish and is not as accurate as other casting processes.
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The last casting process we will look at is investment casting.
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Several wax patterns of the same object are created and attached to a sprue.
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The wax tree is dipped into a slurry to create a ceramic mold.
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Heat is applied to melt out the wax.
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Molten metal is then poured into the ceramic mold.
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once the casting has cooled the mold is broken off.
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Investment casting is good for parts with complex geometry and can achieve tight tolerances, but it is an expensive and time -consuming process.
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Molding is very similar to casting.
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It involves shaping a liquid or pliable material using a mold.
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Most of the time molding is used for forming plastics.
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Typical molding processes are injection molding, compression molding, and blow molding.
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Let's look at the first two.
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Injection molding is the most commonly used manufacturing method for plastics.
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Polymer granules are fed into the hopper
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and a screw is used to pass the material through a heated cylinder before it is forced at pressure into the mold.
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Injection molding is mostly used for thermoplastics, which are polymers which soften when they are heated and harden when they are cooled.
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It is a very fast process and can be fully automated, meaning labor costs are low.
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But startup costs are very high due to the expensive molds, so it is really only cost effective for large production runs.
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Compression molding involves placing a precise amount of material into a mold.
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The mold is closed and pressure and temperature are applied.
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Compression molding is mostly used for thermosets, which are polymers which irreversibly harden
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when heated tooling costs are relatively cheap making it good for small production runs
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but it is quite a slow process
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and is not well suited for complex designs
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so far we have only looked at material deformation processes machining
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is a material removal process where a tool is used to
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remove material from a larger object it is often used for secondary shaping
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when the part has already been formed using a primary process like casting.
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Machining can be used for a wide range of materials, including metals, plastics, and wood.
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Examples of machining include drilling, turning, and reaming.
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Drilling is the cutting of a normal circular hole by pressing a rotating drill bit through a solid object.
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and turning is the use of a cutting tool to shape a rotating workpiece.
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Let's move on to the next category.
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Joining involves combining multiple separate components into a larger assembly.
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Like machining, joining is a secondary process.
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Welding, riveting, brazing, soldering, and fastening are all different types of joining processes.
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Welding uses extremely high heat to fuse distinct metal parts together.
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Unlike soldering and brazing, the base metal melts during welding.
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The final category is additive manufacturing, which involves adding material to build up the desired object, typically one layer at a time.
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3D printing, selective laser sintering, and VAT polymerization are examples of additive manufacturing techniques.
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For 3D printing, a computer is used to successfully build up an object layer by layer.
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3D printing is a slow process, and the range of materials which can be used is limited.
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As a result, it tends to be used for prototyping rather than for mass production.
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That's it for this introduction to manufacturing processes.
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Please leave a comment to let me know what you think, and don't forget to subscribe if you haven't already.
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本课的词汇与口语要点
这节 C1 级别的口语课以视频“How Things Are Made”为素材。 视频中反复出现的词有：metal, casting, material, mold, process。 这段视频共有 92 个句子、1229 个单词可供跟读。 讲话部分时长为 10:17。 说话人语速平稳，每分钟约 120 个词，很适合跟读。 只有 73% 的单词属于英语最常用的 3,000 词，词汇难度较高。
视频中的重点词汇
视频中最难的 15 个单词，附发音和释义：
| 单词 | 发音 | 释义 |
|---|---|---|
| mold 名词 | /moʊld/ | 霉菌, 霉 |
| melt 动词 | /mɛlt/ | 融化, 熔化 |
| forge 名词 | /fɔɹd͡ʒ/ | 鐵匠鋪 /铁匠铺 |
| tolerance 名词 | /ˈtɑ.lə.ɹəns/ | 寬容 /宽容 |
| additive 名词 | /ˈæd.ɪ.tɪv/ | 添加劑 /添加剂 |
| weld 动词 | /wɛld/ | 焊接 |
| harden 动词 | /ˈhɑɹdn̩/ | 硬化 |
| polymer 名词 | /ˈpɑ.lɪ.mɚ/ | 聚合體 /聚合体 |
| injection 名词 | /ɪnˈd͡ʒɛk.ʃən/ | 注射 |
| drill 名词 | /dɹɪl/ | 鑽 /钻 |
| automate 动词 | /ˈɔ.təˌmeɪt/ | 自動化 /自动化 |
| solder 名词 | /ˈsɒl.də(ɹ)/ | 焊料 |
| rotate 动词 | /ˈɹoʊ.teɪt/ | 旋转, 转动 |
| ceramic 名词 | /səˈɹæmɪk/ | 陶瓷 |
| startup 名词 | /ˈstɑɹtˌʌp/ | 初創公司 /初创公司, 新創企業 /新创企业 |
视频中出现的短语动词
| 单词 | 释义 |
|---|---|
| find out 动词 | 找出, 查明 |
视频中的语法
说话人最常用的结构，并附上视频中的原话：
| 结构 | 视频中的用法 |
|---|---|
| 被动语态 be + 过去分词 — 强调发生了什么，而不是谁做的 | are turned · be considered · can be done |
| 定语从句 who / which + 从句 — 补充说明人或事物 | processes, which are · objects which are · automated, which makes |
| 现在完成时 have/has + 过去分词 — 过去发生但与现在仍有关联的事 | have improved · has solidified · has cooled |
需要注意的发音
说话人用了 4 次缩略和弱读形式，例如 can't, don't, haven't。请按听到的简短形式来说。
- “sh” 和 “zh” 音: compression /kəmˈpɹɛʃ.ən/, injection /ɪnˈd͡ʒɛk.ʃən/, deformation /ˌdɛfəˈmeɪʃən/, polymerization /ˌpɒl.ɪ.məɹ.aɪˈzeɪ.ʃən/, automation /ˌɔ.təˈmeɪ.ʃən/
- 长单词——注意重音位置: solidify /səˈlɪdɪˌfaɪ/, geometry /d͡ʒiˈɑ.mə.tɹi/, deformation /ˌdɛfəˈmeɪʃən/, polymerization /ˌpɒl.ɪ.məɹ.aɪˈzeɪ.ʃən/, automation /ˌɔ.təˈmeɪ.ʃən/
中文母语者容易读错的音：
- /v/ — 不要读成 /w/，上齿轻触下唇: additive /ˈæd.ɪ.tɪv/, selective /səˈlɛktɪv/
- 词尾辅音 — 要读清楚，后面不要加元音: mold /moʊld/, melt /mɛlt/, forge /fɔɹd͡ʒ/, tolerance /ˈtɑ.lə.ɹəns/, additive /ˈæd.ɪ.tɪv/
- /r/ 和 /l/ 的区别: tolerance /ˈtɑ.lə.ɹəns/, drill /dɹɪl/, solder /ˈsɒl.də(ɹ)/, granule /ˈɡɹæn.jul/, polymerization /ˌpɒl.ɪ.məɹ.aɪˈzeɪ.ʃən/
如何用这段视频练习
- 先完整听一遍视频，不要开口，记下不认识的单词。
- 用正常速度逐句跟读，每句重复到你的节奏与说话人一致为止。
- 录下自己的声音并与原声对比，特别注意 mold, melt, forge 这类单词。
什么是跟读法？
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。