鋁材可以說是汽車“輕量化”的代名詞了，但事實(shí)上，除了少數(shù)幾款車型大量采用了鋁材之外（其中最著名的是福特 F 系列皮卡），這種輕質(zhì)材料通常僅用于在不影響性能的前提下，少量替代一些容易替代、尺寸較小的鋼材料結(jié)構(gòu)，從而達(dá)到減輕重量或簡化工藝流程的目的。
但是，特斯拉（Tesla）已經(jīng)準(zhǔn)備好將鋁材在汽車上的應(yīng)用推上一個新的臺階。Tesla將在新款 Model Y 上采用了一塊巨大的一件式壓鑄鋁質(zhì)后車身底部結(jié)構(gòu)。根據(jù)Tesla CEO Elon Musk 的說法，這樣使用鋁材將是我們在設(shè)計和制造上優(yōu)勢的一種體現(xiàn)，也反映了鋁材在車輛減重方面的巨大潛力。
Musk素來都是以“滿嘴跑火車”而著名，但這次 Model Y 壓鑄后車身結(jié)構(gòu)的情況與以往有些不同，他對進(jìn)一步拓展鋁材應(yīng)用的熱情得到了相關(guān)制造專家的響應(yīng)。這些專家們認(rèn)為，Tesla使用和房子一樣大的“Giga Press”系列鑄造機(jī)來生產(chǎn)Model Y, Musk或?qū)⒃俅纬蔀?“改變游戲規(guī)則的人”。Harbour Results 制造咨詢公司總裁 Laurie Harbour 表示，“這絕對是一種全新的生產(chǎn)方式，這或許就是Elon Musk一直要求他的工程師們要有創(chuàng)造力的價值體現(xiàn)。”
哪兒都能“減”
在今年 4 月份的博客節(jié)目“Third Row Tesla”中，Musk 詳細(xì)介紹了這種全新鑄造工藝。今年 5 月初的Tesla 2020 年第一季度財務(wù)報告中，Musk 也專門提到了這一點(diǎn)。“當(dāng)前版本的 Model Y 主要采用了 2 個大型高壓壓鑄鋁材結(jié)構(gòu)，它們彼此相互連接，并還有多處與其他部件相連。”他在播客中說，“今年晚些時候，我們將采用一種一件式壓鑄后車身底部結(jié)構(gòu)，且該結(jié)構(gòu)還將直接集成后保險桿。”
他繼續(xù)說道，“我們還將對工藝進(jìn)行不斷優(yōu)化，目前的壓鑄件必須借助CNC精密數(shù)控加工對許多不同的零部件進(jìn)行處理，并將他們結(jié)合起來等一大堆繁瑣的工作。但是一件式壓鑄件將不需要CNC精密數(shù)控加工,甚至不需要基準(zhǔn)。順便說一下，我們也是迭代了很多次才達(dá)到目前的效果。”
Sandy Munro是 Munro &Associates 公司的CEO,該公司是以經(jīng)常“拆解”市面上的熱門車型并進(jìn)行非常專業(yè)的技術(shù)分析而聞名的基準(zhǔn)與競爭分析公司，最近他們完成了對TeslaModel Y 的拆解工作。相關(guān)視頻上傳剛剛一個月就累計達(dá)到了3,600多萬次的瀏覽。Munro 對 Model Y 采用的兩件式鋁制車身底部結(jié)構(gòu)印象特別深刻，并在接受SAE《汽車工程》雜志采訪時對此大加贊賞。
Munro 表示，目前Tesla ModelY具有“我們在汽車中見過最大的兩個壓鑄件。我們從未在汽車中見過如此大尺寸壓鑄件的應(yīng)用。凱迪拉克、寶馬、奧迪也有很多創(chuàng)新的鋁材應(yīng)用，他們也用了壓鑄件，但尺寸絕對沒有Tesla這么大。”Munro 還參加了 Musk 談到即將到來的一件式壓鑄件的那期播客。他斷言，這種“超大型壓鑄件”肯定能拿獎，并且在很長一段時間內(nèi)都將是最大的壓鑄件，這方面還沒有人能夠競爭。”
這臺“龐然大物”來自IDRA 集團(tuán)，他是意大利老牌高壓力壓鑄設(shè)備供應(yīng)商成立于1946 年。事實(shí)上，Tesla是 IDRA 集團(tuán) OL6100CS 超大型壓鑄機(jī)的第一個客戶，并根據(jù)Tesla的特殊要求，對鎖模力進(jìn)行了特別的升級。未來Tesla會將他們裝配在位于加州弗里蒙特工廠和上海工廠。IDRA 集團(tuán)的 Giga Press系列超大型高壓力壓鑄機(jī)長 64 英尺（19.5 米），高 17 英尺（5.3 米）。除了鎖模力得到升級外，每次最大可“射出”的鋁合金材料重量也達(dá)到驚人的104.6公斤（231 磅）。OL6100 出產(chǎn)的產(chǎn)品可能很輕，但它本身卻跟“輕”字一點(diǎn)不相關(guān)，自重超過 410 噸。
未來，Model Y 將采用的一件式壓鑄件將直接替代 Model 3 中為實(shí)現(xiàn)同樣功能而采用的大約 70 個沖壓件、擠壓件和鑄件（這也是Model Y 一件式壓鑄件的設(shè)計基礎(chǔ)）。Musk 將 Model 3 的后車身結(jié)構(gòu)描述為“一床東拼西湊的被子，這不怎么樣，而且這些‘縫縫補(bǔ)補(bǔ)’工作量大的不得了。”
Harbour 也贊同 Musk 的觀點(diǎn)。有了這樣一個超大型高壓力壓鑄機(jī)，“雖然生產(chǎn)循環(huán)周期變長，但你可以在組裝零部件方面節(jié)省大量勞動力，”她觀察到，“你可以在自動化單元、節(jié)省勞動力得到節(jié)省。盡管在這上面需要大量的投資，但考慮到目前Tesla需要從多家制造供應(yīng)商采購大量不同沖壓件的情況下，可以節(jié)省大概20％ 的勞動力成本。更重要的是節(jié)省空間。我認(rèn)為，整體算下來Tesla還是賺的。”
Musk 表示，新的一件式鑄造結(jié)構(gòu)件設(shè)計，將可以節(jié)省 30 % 車身工廠的占地面積。他補(bǔ)充說，這種工藝日后可能也會應(yīng)用至Model 3 等其他車型，“這也是我們未來想應(yīng)用至 Model 3 的工藝。”
潛在的注意事項
Munro 表示，Tesla正在考慮為 Model Y 的前車身結(jié)構(gòu)采用相同的策略。在新策略下，一體式大型壓鑄件可以讓未來對前車身結(jié)構(gòu)的改進(jìn)更加容易、也更便宜，而不需要“嘗試改變一大堆沖壓模具。”他說，這種架構(gòu)很容易支持軸距變化等改動。但 Munro 堅持認(rèn)為，但這并不適合小批量生產(chǎn)。他補(bǔ)充說，“壓鑄件的修理效果通常不好，如果車子受傷太嚴(yán)重，整輛車都必須報廢了。”當(dāng)然，除了Tesla，目前很多車輛設(shè)計都面臨同樣的情況。
Munro 表示，Tesla計劃每年生產(chǎn)100 萬輛 Model Y，因此購買這個超大型高壓力壓鑄機(jī)應(yīng)該是一筆劃算的投資。Munro 和 Harbour 都認(rèn)同：這個超大型高壓力壓鑄機(jī)再次體現(xiàn)了Tesla就是Tesla的獨(dú)特之處。他說，“Tesla總是堅定不移地改進(jìn)、改進(jìn)、再改進(jìn)，”而大多數(shù)汽車公司通?？赡懿粫@么做。
作者：Bill Visnic
本文原發(fā)表于SAE《汽車工程》雜志
Aluminum is synonymous with “weight-saving” in most contemporary automotive-engineering reference points. But apart from a few applications – most notably Ford’s F-Series pickups – aluminum largely is deployed where steel can be readily displaced without performance loss or for comparatively small components that deliver comparatively small weight or process savings.
Electric-vehicle maker Tesla is readying the next step in aluminum use, however – one that effectively matches Ford’s “big gain” approach by specifying a massive piece of structural die-cast aluminum for the rear underbody of the recently launched Model Y crossover. According to Tesla CEO Elon Musk, this new aluminum application represents a radical step for its design and manufacturing advantages and its lightweighting potential.
Musk is renowned for outsized promises, but in the case of the Model Y’s die-cast rear underbody, his enthusiasm for this advanced use of aluminum – cast by a house-sized “giga press” – is supported by manufacturing experts who call it a game-changer. “It’s definitely an all-new look at how to do things,” asserted Laurie Harbour, president at Harbour Results Inc. manufacturing consultancy. “Elon Musk has always pressed his engineers to be creative.”
Reductions in – pretty much everything
Musk spoke in detail about the new casting process in an episode of the “Third Row Tesla Podcast” in April and made more than a passing mention of it in Tesla’s 1Q2020 financial results call in early May. “The current version of Model Y has basically two big high-pressure diecast [HPDC] aluminum castings that are joined and there’s still a bunch of other bits that are attached. Later this year,” he said on the podcast, “we’ll transition to the rear underbody being a single-piece casting that also integrates the rear crash rails.
“It gets better,” he continued. “The current castings, because you’ve got to interface with so many different things, we have to CNC-machine the interfaces and there’s a bunch of things that have to be joined; they have datums on them and that kind of thing. The single-piece casting has no CNC machining – it doesn’t even have datums. It took us a lot of iterations, by the way, to get there.”
Sandy Munro, CEO at Munro & Associates, the benchmarking and competitive analysis firm renowned for its highly analytic “teardowns” of popular and innovative vehicles, recently completed a teardown of a Model Y. A series of internet videos covering Munro’s assessment garnered more than 36 million impressions in little more than a month. Munro was particularly impressed by the current two-piece aluminum underbody structure – and openly offered admiration in an interview with SAE’s Automotive Engineering.
He said the current Tesla Model Y has “two of the biggest castings we’ve ever seen in a car. We’ve never seen them used in an automobile before of that size. There’s lots [of innovative aluminum applications] at Cadillac, BMW, Audi – they’ve all used castings. But nothing quite the size of this thing.” Munro also participated in the podcast in which Musk spoke of the coming single-piece casting. Moving to the “megacasting,” as Munro dubbed it, “definitely wins the prize,” he asserted. “That’s going to be the biggest casting for quite a while. Nobody’s exploring that.”
The mammoth machine is being supplied by IDRA Group, an Italian leader in HPDC equipment founded in 1946. Tesla is the first customer for IDRA’s hulking OL6100 CS (with upgraded locking force to handle the special Tesla casting), destined for installation in the company’s Fremont, California and Shanghai, China, plants. IDRA’s “Giga Press” measures some 64 feet (19.5 m) long and 17 feet (5.3 m) tall. Along with the higher clamping force is a maximum aluminum-alloy “shot” weight of 104.6 kg (231 lb). The OL6100’s output may be lightweight castings, but the machine itself is anything but light, weighing in excess of 410 tons.
The single-piece casting for Model Y will replace around 70 stampings, extrusions and castings that currently make up the same fabricated assembly in the Model 3, on which much of the Model Y is based. Musk described the Model 3’s rear structure as “a patchwork quilt – it’s not great. The complexity in the body shop is insane,” he said.
Harbour agreed. With such a large and inclusive casting, “Even with a big cycle time, you eliminate all the labor to assemble pieces and subcomponents,” she observed. “You’re saving on automation cells, you’re saving on people. It would be tough to put dollars to it, but think of multiple suppliers doing stampings, you could save maybe 20% on labor cost. And reduction in footprint is major. My guess is that it’s a net-net efficiency gain.”
Musk claimed the new single-piece casting design, and the goliath machine that will produce it, will deliver a 30% reduction in the size of the body shop. He added that the process probably will transfer to Model 3 production as well. “That’s the thing we want to bring to bear on the Model 3 over time,” he said.
Munro said Tesla is pondering a similar strategy for the front of the Model Y. And a large casting probably makes changes to the affected structure a less-expensive proposition than “trying to change a bunch of stamping dies.” Alterations such as wheelbase changes also could easily be accommodated by such an architecture, he said. But it wouldn’t be the approach for low-volume production, Munro maintained. And “castings don’t repair very well,” he added. “If an impact was severe enough, the car’s a write-off,” he said. Of course, such is the case with many contemporary vehicle designs.
Munro said Tesla plans to assemble up to 1 million vehicles annually off the Model Y architecture, so the company’s Giga Press investment likely is a sound one. He and Harbour agree that the mega-casting approach is an example of Tesla being Tesla. “They do continuous improvement in design,” a practice most auto companies typically don’t embrace, Munro said.
By Bill Visnic
SAE Automotive Engineering
Tesla Model Y 的車身結(jié)構(gòu)采用了一件式壓鑄件。（圖片來源：Tesla)
現(xiàn)行版 Model Y 兩件式鋁鑄后車底結(jié)構(gòu)。（圖片來源：Tesla）
Munro and Associates 工程公司的首席執(zhí)行官 Sandy Munro。（圖片來源：Munro and Associates 工程公司）
IDRA 集團(tuán)新款Giga Press系列 OL 5500CS型壓鑄機(jī)可用于生產(chǎn)大型鋁材壓鑄件。(照片來源：IDRA)
Model Y 中的持續(xù)創(chuàng)新有望在其他Tesla車型上得到應(yīng)用。（圖片來源：Tesla)