Pengertian mesin CNC
CNC singkatan dari Computer Numerically Controlled, merupakan mesin perkakas yang dilengkapi dengan sistem mekanik dan kontrol berbasis komputer yang mampu membaca instruksi kode N, G, F, T, dan lain-lain, dimana kode-kode tersebut akan menginstruksikan ke mesin CNC agar bekerja sesuai dengan program benda kerja yang akan dibuat. Secara umum cara kerja mesin perkakas CNC tidak berbeda dengan mesin perkakas konvensional. Fungsi CNC dalam hal ini lebih banyak menggantikan pekerjaan operator dalam mesin perkakas konvensional. Misalnya pekerjaan setting tool atau mengatur gerakan pahat sampai pada posisi siap memotong, gerakan pemotongan dan gerakan kembali keposisi awal, dan lain-lain. Demikian pula dengan pengaturan kondisi pemotongan (kecepatan potong, kecepatan makan dan kedalaman pemotongan) serta fungsi pengaturan yang lain seperti penggantian pahat, pengubahan transmisi daya (jumlah putaran poros utama), dan arah putaran poros utama, pengekleman, pengaturan cairan pendingin dan sebagainya. Mesin perkakas CNC dilengkapi dengan berbagai alat potong yang dapat membuat benda kerja secara presisi dan dapat melakukan interpolasi yang diarahkan secara numerik (berdasarkan angka). Parameter sistem operasi CNC dapat diubah melalui program perangkat lunak (software load program) yang sesuai. Tingkat ketelitian mesin CNC lebih akurat hingga ketelitian seperseribu millimeter, karena penggunaan ballscrew pada setiap poros transportiernya. Ballscrew bekerja seperti lager yang tidak memiliki kelonggaran/spelling namun dapat bergerak dengan lancar. Pada awalnya mesin CNC masih menggunakan memori berupa kertas berlubang sebagai media untuk mentransfer kode G dan M ke sistem kontrol. Setelah tahun 1950, ditemukan metode baru mentransfer data dengan menggunakan kabel RS232, floppy disks, dan terakhir oleh Komputer Jaringan Kabel

(Computer Network Cables) bahkan bisa dikendalikan melalui internet. Akhir-akhir ini mesin-mesin CNC telah berkembang secara menakjubkan sehingga telah mengubah industri pabrik yang selama ini menggunakan tenaga manusia menjadi mesin-mesom otomatik. Dengan telah berkembangnya Mesin CNC, maka benda kerja yang rumit sekalipun dapat dibuat secara mudah dalam jumlah yang banyak. Selama ini pembuatan komponen/suku cadang suatu mesin yang presisi dengan mesin perkakas manual tidaklah mudah, meskipun dilakukan oleh seorang operator mesin perkakas yang mahir sekalipun. Penyelesaiannya memerlukan waktu lama. Bila ada permintaan konsumen untuk membuat komponen dalam jumlah banyak dengan waktu singkat, dengan kualitas sama baiknya, tentu akan sulit dipenuhi bila menggunakan perkakas manual. Apalagi bila bentuk benda kerja yang dipesan lebih rumit, tidak dapat diselesaikan dalam waktu singkat. Secara ekonomis biaya produknya akan menjadi mahal, hingga sulit bersaing dengan harga di pasaran. Tuntutan konsumen yang menghendaki kualitas benda kerja yang presisi, berkualitas sama baiknya, dalam waktu singkat dan dalam jumlah yang banyak, akan lebih mudah dikerjakan dengan mesin perkakas CNC (Computer Numerlcally Controlled), yaitu mesin yang dapat bekerja melalui pemogramman yang dilakukan dan dikendalikan melalui komputer. Mesin CNC dapat bekerja secara otomatis atau semiotomatis setelah diprogram terlebih dahulu melalui komputer yang ada. Program yang dimaksud merupakan program membuat benda kerja yang telah direncanakan atau dirancang sebelumnya. Sebelum benda kerja tersebut dieksikusi atau dikerjakan oleh mesin CNC, sebaikanya program tersebut di cek berulang-ualang agar program benarbenar telah sesuai dengan bentuk benda kerja yang diinginkan, serta benar-benar dapat dikerjakan oleh mesin CNC. Pengecekan tersebut dapat melalui layar monitor yang terdapat pada mesin atau bila tidak ada fasilitas cheking melalui monitor (seperti pada CNC TU EMCO 2A/3A) dapat pula melalui plotter yang dipasang pada tempat dudukan pahat/palsu frais. Setelah program benar-benar telah berjalan seperti rencana, baru kemudian dilaksanakan/dieksekusi oleh mesin CNC. Dari segi pemanfaatannya, mesin perkakas CNC dapat dibagi menjadi dua, antara lain: (a) mesin CNC Training unit (TU), yaitu mesin yang digunakan sarana pendidikan, dosen dan training. (b) mesin CNC produktion unit (PU), yaitu mesin CNC yang digunakan untuk membuat benda kerja/komponen yang dapat digunakan sebagai mana mestinya. Dari segi jenisnya, mesin perkakas CNC dapat dibagi menjadi tiga jenis, antara lain: (a) mesin CNC 2A yaitu mesin CNC 2 aksis, karena gerak pahatnya hanya pada arah dua sumbu koordinat (aksis) yaitu koordinat X, dan koordinat Z, atau dikenal dengan mesin bubut CNC, (b) mesin CNC 3A, yaitu mesin CNC 3 aksis atau mesin yang memiliki gerakan sumbu utama kearah sumbu koordinat X, Y, dan Z, atau dikenal dengan mesin frsais CNC. (c) mesin CNC kombinasi, yaitu mesin CNC yang mampu mengerjakan pekerjaan bubut dan freis sekaligus, dapat pula dilengkapi dengan peralatan pengukuran sehingga dapat melakukan pengontrolan kualitas pembubutan/pengefraisan pada benda kerja yang dihasilkan. Pada umumnya mesin CNC yang sering dijumpai adalah mesin CNC 2A (bubut) dan mesin CNC 3A (frais).


Even as a high school student, Dave Goldberg was urging female classmates to speak up. As a young dot-com executive, he had one girlfriend after another, but fell hard for a driven friend named Sheryl Sandberg, pining after her for years. After they wed, Mr. Goldberg pushed her to negotiate hard for high compensation and arranged his schedule so that he could be home with their children when she was traveling for work.

Mr. Goldberg, who died unexpectedly on Friday, was a genial, 47-year-old Silicon Valley entrepreneur who built his latest company, SurveyMonkey, from a modest enterprise to one recently valued by investors at $2 billion. But he was also perhaps the signature male feminist of his era: the first major chief executive in memory to spur his wife to become as successful in business as he was, and an essential figure in “Lean In,” Ms. Sandberg’s blockbuster guide to female achievement.

Over the weekend, even strangers were shocked at his death, both because of his relatively young age and because they knew of him as the living, breathing, car-pooling center of a new philosophy of two-career marriage.

“They were very much the role models for what this next generation wants to grapple with,” said Debora L. Spar, the president of Barnard College. In a 2011 commencement speech there, Ms. Sandberg told the graduates that whom they married would be their most important career decision.

In the play “The Heidi Chronicles,” revived on Broadway this spring, a male character who is the founder of a media company says that “I don’t want to come home to an A-plus,” explaining that his ambitions require him to marry an unthreatening helpmeet. Mr. Goldberg grew up to hold the opposite view, starting with his upbringing in progressive Minneapolis circles where “there was woman power in every aspect of our lives,” Jeffrey Dachis, a childhood friend, said in an interview.

The Goldberg parents read “The Feminine Mystique” together — in fact, Mr. Goldberg’s father introduced it to his wife, according to Ms. Sandberg’s book. In 1976, Paula Goldberg helped found a nonprofit to aid children with disabilities. Her husband, Mel, a law professor who taught at night, made the family breakfast at home.

Later, when Dave Goldberg was in high school and his prom date, Jill Chessen, stayed silent in a politics class, he chastised her afterward. He said, “You need to speak up,” Ms. Chessen recalled in an interview. “They need to hear your voice.”

Years later, when Karin Gilford, an early employee at Launch Media, Mr. Goldberg’s digital music company, became a mother, he knew exactly what to do. He kept giving her challenging assignments, she recalled, but also let her work from home one day a week. After Yahoo acquired Launch, Mr. Goldberg became known for distributing roses to all the women in the office on Valentine’s Day.

Ms. Sandberg, who often describes herself as bossy-in-a-good-way, enchanted him when they became friendly in the mid-1990s. He “was smitten with her,” Ms. Chessen remembered. Ms. Sandberg was dating someone else, but Mr. Goldberg still hung around, even helping her and her then-boyfriend move, recalled Bob Roback, a friend and co-founder of Launch. When they finally married in 2004, friends remember thinking how similar the two were, and that the qualities that might have made Ms. Sandberg intimidating to some men drew Mr. Goldberg to her even more.

Over the next decade, Mr. Goldberg and Ms. Sandberg pioneered new ways of capturing information online, had a son and then a daughter, became immensely wealthy, and hashed out their who-does-what-in-this-marriage issues. Mr. Goldberg’s commute from the Bay Area to Los Angeles became a strain, so he relocated, later joking that he “lost the coin flip” of where they would live. He paid the bills, she planned the birthday parties, and both often left their offices at 5:30 so they could eat dinner with their children before resuming work afterward.

Friends in Silicon Valley say they were careful to conduct their careers separately, politely refusing when outsiders would ask one about the other’s work: Ms. Sandberg’s role building Facebook into an information and advertising powerhouse, and Mr. Goldberg at SurveyMonkey, which made polling faster and cheaper. But privately, their work was intertwined. He often began statements to his team with the phrase “Well, Sheryl said” sharing her business advice. He counseled her, too, starting with her salary negotiations with Mark Zuckerberg.

“I wanted Mark to really feel he stretched to get Sheryl, because she was worth it,” Mr. Goldberg explained in a 2013 “60 Minutes” interview, his Minnesota accent and his smile intact as he offered a rare peek of the intersection of marriage and money at the top of corporate life.



While his wife grew increasingly outspoken about women’s advancement, Mr. Goldberg quietly advised the men in the office on family and partnership matters, an associate said. Six out of 16 members of SurveyMonkey’s management team are female, an almost unheard-of ratio among Silicon Valley “unicorns,” or companies valued at over $1 billion.

When Mellody Hobson, a friend and finance executive, wrote a chapter of “Lean In” about women of color for the college edition of the book, Mr. Goldberg gave her feedback on the draft, a clue to his deep involvement. He joked with Ms. Hobson that she was too long-winded, like Ms. Sandberg, but aside from that, he said he loved the chapter, she said in an interview.

By then, Mr. Goldberg was a figure of fascination who inspired a “where can I get one of those?” reaction among many of the women who had read the best seller “Lean In.” Some lamented that Ms. Sandberg’s advice hinged too much on marrying a Dave Goldberg, who was humble enough to plan around his wife, attentive enough to worry about which shoes his young daughter would wear, and rich enough to help pay for the help that made the family’s balancing act manageable.

Now that he is gone, and Ms. Sandberg goes from being half of a celebrated partnership to perhaps the business world’s most prominent single mother, the pages of “Lean In” carry a new sting of loss.

“We are never at 50-50 at any given moment — perfect equality is hard to define or sustain — but we allow the pendulum to swing back and forth between us,” she wrote in 2013, adding that they were looking forward to raising teenagers together.

“Fortunately, I have Dave to figure it out with me,” she wrote.

Dave Goldberg Was Lifelong Women’s Advocate

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