Granit adalah jenis batuan beku yang ditambang karena kekuatan, kepadatan, daya tahan, dan ketahanannya terhadap korosi yang sangat tinggi. Namun, granit juga sangat serbaguna—bukan hanya untuk bentuk persegi dan persegi panjang! Bahkan, kami dengan percaya diri mengerjakan komponen granit yang dirancang dalam berbagai bentuk, sudut, dan lengkungan—dengan hasil yang sangat baik.
Through our state of the art processing, cut surfaces can be exceptionally flat. These qualities make granite the ideal material to create custom-size and custom-design machine bases and metrology components. Granite is:
■ dapat dikerjakan dengan mesin
■ benar-benar rata saat dipotong dan diselesaikan
■ tahan karat
■ tahan lama
■ tahan lama
Komponen granit juga mudah dibersihkan. Saat membuat desain khusus, pastikan untuk memilih granit karena keunggulannya.

STANDAR / APLIKASI DENGAN TEKANAN AUS TINGGI
Granit yang digunakan oleh ZHHIMG untuk produk pelat permukaan standar kami memiliki kandungan kuarsa yang tinggi, yang memberikan ketahanan lebih besar terhadap keausan dan kerusakan. Warna Superior Black kami memiliki tingkat penyerapan air yang rendah, meminimalkan kemungkinan alat ukur presisi Anda berkarat saat diletakkan di atas pelat. Warna granit yang ditawarkan oleh ZHHIMG menghasilkan lebih sedikit silau, yang berarti mengurangi ketegangan mata bagi individu yang menggunakan pelat tersebut. Kami telah memilih jenis granit kami dengan mempertimbangkan ekspansi termal dalam upaya untuk meminimalkan aspek ini.

CUSTOM APPLICATIONS
Ketika aplikasi Anda membutuhkan pelat dengan bentuk khusus, sisipan berulir, alur, atau pengerjaan mesin lainnya, Anda perlu memilih material seperti Black Jinan Black. Material alami ini menawarkan kekakuan yang unggul, peredaman getaran yang sangat baik, dan kemampuan pengerjaan mesin yang lebih baik.

Penting untuk dicatat bahwa warna saja bukanlah indikasi kualitas fisik batu tersebut. Secara umum, warna granit berhubungan langsung dengan ada atau tidaknya mineral, yang mungkin tidak berpengaruh pada kualitas yang menjadikannya material pelat permukaan yang baik. Ada granit merah muda, abu-abu, dan hitam yang sangat baik untuk pelat permukaan, serta granit hitam, abu-abu, dan merah muda yang sama sekali tidak cocok untuk aplikasi presisi. Karakteristik penting granit, yang berkaitan dengan penggunaannya sebagai material pelat permukaan, tidak ada hubungannya dengan warna, dan adalah sebagai berikut:
■ Kekakuan (lendutan di bawah beban - ditunjukkan oleh Modulus Elastisitas)
■ Kekerasan
■ Kepadatan
■ Ketahanan terhadap keausan
■ Stabilitas
■ Porositas

Kami telah menguji banyak material granit dan membandingkannya. Akhirnya kami mendapatkan hasil, granit hitam Jinan adalah material terbaik yang pernah kami ketahui. Granit hitam India dan granit Afrika Selatan mirip dengan granit hitam Jinan, tetapi sifat fisiknya lebih rendah daripada granit hitam Jinan. ZHHIMG akan terus mencari lebih banyak material granit di dunia dan membandingkan sifat fisiknya.

Untuk membahas lebih lanjut tentang jenis granit yang tepat untuk proyek Anda, silakan hubungi kami.info@zhhimg.com.

Produsen yang berbeda menggunakan standar yang berbeda. Ada banyak standar di dunia ini.
Standar DIN, ASME B89.3.7-2013 atau Spesifikasi Federal GGG-P-463c (Pelat Permukaan Granit) dan sebagainya sebagai dasar spesifikasi mereka.

Dan kami dapat memproduksi pelat inspeksi presisi granit sesuai dengan kebutuhan Anda. Silakan hubungi kami jika Anda ingin mengetahui informasi lebih lanjut tentang standar lainnya.

Kerataan dapat dianggap sebagai kondisi di mana semua titik pada permukaan berada di antara dua bidang sejajar, yaitu bidang dasar dan bidang atap. Pengukuran jarak antara kedua bidang tersebut merupakan kerataan keseluruhan permukaan. Pengukuran kerataan ini umumnya memiliki toleransi dan mungkin mencakup penunjukan tingkat kerataan.

Sebagai contoh, toleransi kerataan untuk tiga tingkatan standar didefinisikan dalam spesifikasi federal sebagaimana ditentukan oleh rumus berikut:
■ Kelas Laboratorium AA = (40 + diagonal kuadrat/25) x 0,000001" (satu sisi)
■ Tingkat Inspeksi A = Tingkat Laboratorium AA x 2
■ Kelas Ruang Perkakas B = Kelas Laboratorium AA x 4.

Untuk pelat permukaan ukuran standar, kami menjamin toleransi kerataan yang melebihi persyaratan spesifikasi ini. Selain kerataan, ASME B89.3.7-2013 & Spesifikasi Federal GGG-P-463c membahas topik-topik termasuk: akurasi pengukuran berulang, sifat material granit pelat permukaan, penyelesaian permukaan, lokasi titik tumpuan, kekakuan, metode inspeksi yang dapat diterima, pemasangan sisipan berulir, dll.

Pelat permukaan granit ZHHIMG dan pelat inspeksi granit memenuhi atau melampaui semua persyaratan yang ditetapkan dalam spesifikasi ini. Saat ini, belum ada spesifikasi yang mendefinisikan pelat sudut granit, pelat paralel, atau pelat persegi utama.

Dan Anda dapat menemukan rumus untuk standar lainnya diUNDUH.

Pertama, penting untuk menjaga kebersihan pelat. Debu abrasif yang beterbangan biasanya merupakan sumber keausan terbesar pada pelat, karena cenderung menempel pada benda kerja dan permukaan kontak alat ukur. Kedua, tutupi pelat Anda untuk melindunginya dari debu dan kerusakan. Masa pakai dapat diperpanjang dengan menutupi pelat saat tidak digunakan, dengan memutar pelat secara berkala sehingga satu area tidak menerima penggunaan yang berlebihan, dan dengan mengganti bantalan kontak baja pada alat ukur dengan bantalan karbida. Selain itu, hindari meletakkan makanan atau minuman ringan di atas pelat. Perhatikan bahwa banyak minuman ringan mengandung asam karbonat atau asam fosfat, yang dapat melarutkan mineral yang lebih lunak dan meninggalkan lubang kecil di permukaan.

Hal ini bergantung pada bagaimana piring tersebut digunakan. Jika memungkinkan, kami sarankan untuk membersihkan piring di awal hari (atau shift kerja) dan sekali lagi di akhir hari. Jika piring menjadi kotor, terutama dengan cairan berminyak atau lengket, sebaiknya segera dibersihkan.

Bersihkan pelat secara teratur dengan cairan atau pembersih pelat permukaan tanpa air ZHHIMG. Pemilihan larutan pembersih sangat penting. Jika pelarut yang mudah menguap digunakan (aseton, pengencer cat, alkohol, dll.), penguapan akan mendinginkan permukaan dan mendistorsinya. Dalam hal ini, perlu untuk membiarkan pelat kembali normal sebelum digunakan, atau akan terjadi kesalahan pengukuran.

Waktu yang dibutuhkan agar pelat kembali normal akan bervariasi tergantung pada ukuran pelat dan jumlah pendinginan. Satu jam seharusnya cukup untuk pelat yang lebih kecil. Dua jam mungkin diperlukan untuk pelat yang lebih besar. Jika pembersih berbahan dasar air digunakan, akan terjadi juga pendinginan akibat penguapan.

Pelat tersebut juga akan menahan air, dan ini dapat menyebabkan karat pada bagian logam yang bersentuhan dengan permukaan. Beberapa pembersih juga akan meninggalkan residu lengket setelah mengering, yang akan menarik debu di udara, dan justru meningkatkan keausan, alih-alih menurunkannya.

Hal ini bergantung pada penggunaan dan lingkungan pelat. Kami merekomendasikan agar pelat baru atau aksesori granit presisi dikalibrasi ulang sepenuhnya dalam waktu satu tahun setelah pembelian. Jika pelat permukaan granit akan sering digunakan, sebaiknya interval ini dipersingkat menjadi enam bulan. Inspeksi bulanan untuk kesalahan pengukuran berulang menggunakan level elektronik, atau perangkat serupa, akan menunjukkan adanya titik keausan yang berkembang dan hanya membutuhkan beberapa menit untuk dilakukan. Setelah hasil kalibrasi ulang pertama ditentukan, interval kalibrasi dapat diperpanjang atau dipersingkat sesuai dengan yang diizinkan atau dipersyaratkan oleh sistem mutu internal Anda.

Kami dapat menawarkan layanan untuk membantu Anda memeriksa dan mengkalibrasi pelat permukaan granit Anda.

Ada beberapa kemungkinan penyebab variasi antar kalibrasi:

• Permukaan tersebut dicuci dengan larutan panas atau dingin sebelum kalibrasi, dan tidak diberi waktu yang cukup untuk normalisasi.
• Pelat tersebut tidak ditopang dengan benar.
• Perubahan suhu
• Draf
• Hindari paparan langsung sinar matahari atau panas radiasi lainnya pada permukaan piring. Pastikan pencahayaan di atas tidak memanaskan permukaan.
• Variasi gradien suhu vertikal antara musim dingin dan musim panas (Jika memungkinkan, ketahui gradien suhu vertikal pada saat kalibrasi dilakukan.)
• Pelat tidak diberi waktu yang cukup untuk kembali normal setelah pengiriman.
• Penggunaan peralatan inspeksi yang tidak tepat atau penggunaan peralatan yang tidak terkalibrasi.
• Perubahan permukaan akibat keausan

Ada berapa jenis lubang pada granit presisi?

Slot pada Komponen Granit Presisi

Bagi banyak pabrik, ruang inspeksi, dan laboratorium, pelat permukaan granit presisi diandalkan sebagai dasar untuk pengukuran yang akurat. Karena setiap pengukuran linier bergantung pada permukaan referensi yang akurat dari mana dimensi akhir diambil, pelat permukaan menyediakan bidang referensi terbaik untuk inspeksi dan tata letak pekerjaan sebelum pemesinan. Pelat ini juga merupakan alas yang ideal untuk melakukan pengukuran ketinggian dan mengukur permukaan. Lebih lanjut, tingkat kerataan, stabilitas, kualitas keseluruhan, dan pengerjaan yang tinggi menjadikannya pilihan yang baik untuk memasang sistem pengukuran mekanis, elektronik, dan optik yang canggih. Untuk setiap proses pengukuran ini, sangat penting untuk menjaga agar pelat permukaan tetap terkalibrasi.

Repeat Measurements and Flatness

Baik kerataan maupun pengukuran berulang sangat penting untuk memastikan permukaan yang presisi. Kerataan dapat dianggap sebagai semua titik pada permukaan yang berada di dalam dua bidang paralel, yaitu bidang dasar dan bidang atap. Pengukuran jarak antara bidang-bidang tersebut adalah kerataan keseluruhan permukaan. Pengukuran kerataan ini umumnya memiliki toleransi dan mungkin mencakup penunjukan tingkatan.

The flatness tolerances for three standard grades are defined in the federal specification as determined by the following formula:

Standar DIN, Standar GB, Standar ASME, Standar JJS... setiap negara memiliki standar yang berbeda...

Detail selengkapnya tentang standar.

In addition to flatness, repeatability must be ensured. A repeat measurement is a measurement of local flatness areas. It is a measurement taken anywhere on the surface of a plate that will repeat within the stated tolerance. Controlling local area flatness to a tighter tolerance than overall flatness guarantees a gradual change in surface flatness profile, thereby minimizing local errors.

Untuk memastikan pelat permukaan memenuhi spesifikasi kerataan dan pengukuran berulang, produsen pelat permukaan granit harus menggunakan Spesifikasi Federal GGG-P-463c sebagai dasar spesifikasi mereka. Standar ini membahas akurasi pengukuran berulang, sifat material granit pelat permukaan, penyelesaian permukaan, lokasi titik tumpuan, kekakuan, metode inspeksi yang dapat diterima, dan pemasangan sisipan berulir.

Checking Plate Accuracy

Dengan mengikuti beberapa panduan sederhana, investasi pada pelat permukaan granit seharusnya dapat bertahan selama bertahun-tahun. Tergantung pada penggunaan pelat, lingkungan bengkel, dan akurasi yang dibutuhkan, frekuensi pengecekan akurasi pelat permukaan bervariasi. Aturan umum yang berlaku adalah pelat baru harus dikalibrasi ulang sepenuhnya dalam waktu satu tahun setelah pembelian. Jika pelat sering digunakan, disarankan untuk memperpendek interval ini menjadi enam bulan.

Before a surface plate has worn beyond specification for overall flatness, it will show worn or wavy posts. Monthly inspection for repeat measurement errors using a repeat reading gage will identify wear spots. A repeat reading gage is a high-precision instrument that detects local error and can be displayed on a high magnification electronic amplifier.

An effective inspection program should include regular checks with an autocollimator, providing actual calibration of overall flatness traceable to National Institute of Standards and Technology (NIST). Comprehensive calibration by the manufacturer or an independent company is necessary from time to time.

Variations Between Calibrations

Dalam beberapa kasus, terdapat variasi antara kalibrasi pelat permukaan. Terkadang faktor-faktor seperti perubahan permukaan akibat keausan, penggunaan peralatan inspeksi yang tidak tepat, atau penggunaan peralatan yang tidak terkalibrasi dapat menyebabkan variasi ini. Namun, dua faktor yang paling umum adalah suhu dan penyangga.

One of the most important variables is temperature. For instance, the surface might have been washed with a hot or cold solution prior to calibration and not allowed sufficient time to normalize. Other causes of temperature change include drafts of cold or hot air, direct sunlight, overhead lighting or other sources of radiant heat on the surface of the plate.

There also can be variations in the vertical temperature gradient between winter and summer. In some cases, the plate is not allowed sufficient time to normalize after shipment. It is a good idea to record the vertical gradient temperature at the time the calibration is performed.

Another common cause for calibration variation is a plate that is improperly supported. A surface plate should be supported at three points, ideally located 20% of the length in from the ends of the plate. Two supports should be located 20% of the width in from the long sides, and the remaining support should be centered.

Only three points can rest solidly on anything but a precision surface. Attempting to support the plate at more than three points will cause the plate to receive its support from various combinations of three points, which will not be the same three points on which it was supported during production. This will introduce errors as the plate deflects to conform to the new support arrangement. Consider using steel stands with support beams designed to line up with the proper support points. Stands for this purpose are generally available from the surface plate manufacturer.

If the plate is properly supported, precise leveling is only necessary if an application specifies it. Leveling is not necessary to maintain the accuracy of a properly supported plate.

Extend Plate Life

Dengan mengikuti beberapa panduan, keausan pada permukaan pelat granit dapat dikurangi dan pada akhirnya, masa pakainya akan diperpanjang.

Pertama, penting untuk menjaga kebersihan pelat. Debu abrasif yang beterbangan di udara biasanya merupakan sumber keausan terbesar pada pelat, karena cenderung menempel pada benda kerja dan permukaan kontak alat ukur.

It also is important to cover plates to protect it from dust and damage. Wear life can be extended by covering the plate when not in use.

Putar pelat secara berkala agar satu area tidak mengalami penggunaan berlebihan. Selain itu, disarankan untuk mengganti bantalan kontak baja pada alat ukur dengan bantalan karbida.

Avoid setting food or soft drinks on the plate. Many soft drinks contain either carbonic or phosphoric acid, which can dissolve the softer minerals and leave small pits in the surface.

Where to Relap

Ketika pelat permukaan granit perlu dipoles ulang, pertimbangkan apakah layanan ini akan dilakukan di lokasi atau di fasilitas kalibrasi. Selalu lebih baik jika pelat dipoles ulang di pabrik atau fasilitas khusus. Namun, jika pelat tidak terlalu aus, umumnya dalam batas toleransi 0,001 inci, maka dapat dipoles ulang di lokasi. Jika pelat aus hingga melebihi 0,001 inci dari toleransi, atau jika berlubang atau tergores parah, maka harus dikirim ke pabrik untuk digerinda sebelum dipoles ulang.

A calibration facility has the equipment and factory setting providing the optimum conditions for proper plate calibration and rework if necessary.

Penting untuk sangat berhati-hati dalam memilih teknisi kalibrasi dan pemolesan di lokasi. Mintalah akreditasi dan pastikan peralatan yang akan digunakan teknisi memiliki kalibrasi yang dapat dilacak. Pengalaman juga merupakan faktor penting, karena dibutuhkan bertahun-tahun untuk mempelajari cara memoles granit presisi dengan benar.

Critical measurements start with a precision granite surface plate as a baseline. By ensuring a reliable reference by using a properly calibrated surface plate, manufacturers have one of the essential tools for reliable measurements and better quality parts.Q

Checklist for Calibration Variations

1. Permukaan dicuci dengan larutan panas atau dingin sebelum kalibrasi dan tidak diberi waktu yang cukup untuk normalisasi.

2. Pelat tersebut tidak ditopang dengan benar.

3. Perubahan suhu.

4. Draf.

5. Sinar matahari langsung atau panas radiasi lainnya pada permukaan pelat. Pastikan pencahayaan di atas tidak memanaskan permukaan.

6. Variasi gradien suhu vertikal antara musim dingin dan musim panas. Jika memungkinkan, ketahui gradien suhu vertikal pada saat kalibrasi dilakukan.

7. Pelat tidak diberi waktu yang cukup untuk kembali normal setelah pengiriman.

8. Penggunaan peralatan inspeksi yang tidak tepat atau penggunaan peralatan yang tidak terkalibrasi.

9. Perubahan permukaan akibat keausan.

Tech Tips

• Karena setiap pengukuran linier bergantung pada permukaan referensi yang akurat dari mana dimensi akhir diambil, pelat permukaan menyediakan bidang referensi terbaik untuk inspeksi dan tata letak pekerjaan sebelum pemesinan.
• Controlling local area flatness to a tighter tolerance than overall flatness guarantees a gradual change in surface flatness profile, thereby minimizing local errors.
• Program inspeksi yang efektif harus mencakup pemeriksaan rutin dengan autokollimator, yang memberikan kalibrasi aktual terhadap kerataan keseluruhan yang dapat ditelusuri ke Otoritas Inspeksi Nasional.

Di antara partikel mineral yang membentuk granit, lebih dari 90% adalah feldspar dan kuarsa, di mana feldspar merupakan yang terbanyak. Feldspar sering berwarna putih, abu-abu, dan merah muda, sedangkan kuarsa sebagian besar tidak berwarna atau putih keabu-abuan, yang membentuk warna dasar granit. Feldspar dan kuarsa adalah mineral keras, dan sulit untuk dipindahkan dengan pisau baja. Adapun bintik-bintik gelap pada granit, terutama mika hitam, terdapat beberapa mineral lain. Meskipun biotit relatif lunak, kemampuannya untuk menahan tekanan tidak lemah, dan pada saat yang sama jumlahnya sedikit dalam granit, seringkali kurang dari 10%. Inilah kondisi material yang membuat granit sangat kuat.

Alasan lain mengapa granit kuat adalah karena partikel mineralnya terikat erat satu sama lain dan tertanam di dalam satu sama lain. Pori-porinya seringkali kurang dari 1% dari total volume batuan. Hal ini memberi granit kemampuan untuk menahan tekanan yang kuat dan tidak mudah ditembus oleh kelembapan.

Komponen granit terbuat dari batu yang tidak berkarat, tahan asam dan basa, memiliki ketahanan aus yang baik dan umur pakai yang panjang, tanpa perawatan khusus. Komponen presisi granit sebagian besar digunakan dalam perkakas industri permesinan. Oleh karena itu, komponen ini disebut komponen presisi granit atau komponen granit. Karakteristik komponen presisi granit pada dasarnya sama dengan karakteristik platform granit. Pengenalan perkakas dan pengukuran komponen presisi granit: Teknologi permesinan presisi dan permesinan mikro merupakan arah pengembangan penting industri manufaktur permesinan, dan telah menjadi indikator penting untuk mengukur tingkat teknologi tinggi. Pengembangan teknologi mutakhir dan industri pertahanan tidak terlepas dari teknologi permesinan presisi dan permesinan mikro. Komponen granit dapat digeser dengan lancar dalam pengukuran, tanpa hambatan. Pengukuran permukaan kerja, goresan umum tidak memengaruhi akurasi pengukuran. Komponen granit perlu dirancang dan diproduksi sesuai dengan persyaratan dari pihak permintaan.

Bidang aplikasi:

Seperti yang kita ketahui, semakin banyak mesin dan peralatan yang memilih komponen granit presisi.

Komponen granit digunakan untuk gerakan dinamis, motor linier, CMM, CNC, mesin laser...

Silakan hubungi kami untuk informasi lebih lanjut.

Perangkat pengukuran dan komponen mekanik dari granit terbuat dari granit hitam Jinan berkualitas tinggi. Karena presisinya yang tinggi, daya tahan yang lama, stabilitas yang baik, dan ketahanan terhadap korosi, perangkat ini semakin banyak digunakan dalam inspeksi produk di industri modern dan bidang ilmiah seperti mekanik, kedirgantaraan, dan penelitian ilmiah.

Keuntungan

----Dua kali lebih keras dari besi cor;

----Perubahan dimensi minimal disebabkan oleh perubahan suhu;

----Bebas dari perasan, sehingga tidak ada gangguan dalam pekerjaan;

----Bebas dari gerigi atau tonjolan karena struktur butiran yang halus dan daya rekat yang minimal, yang memastikan tingkat kerataan yang tinggi selama masa pakai yang lama dan tidak menyebabkan kerusakan pada bagian atau instrumen lain;

Pengoperasian tanpa masalah untuk penggunaan dengan bahan magnetik;

----Umur pakai panjang dan anti karat, sehingga biaya perawatan rendah.

Pelat permukaan granit presisi dipoles dengan presisi hingga mencapai standar kerataan tinggi untuk mendapatkan akurasi dan digunakan sebagai dasar untuk memasang sistem pengukuran mekanis, elektronik, dan optik yang canggih.

Beberapa fitur unik dari permukaan lempengan granit:

Keseragaman Kekerasan;

Akurat dalam kondisi beban;

Peredam Getaran;

Mudah dibersihkan;

Tahan terhadap lilitan;

Porositas Rendah;

Tidak abrasif;

Non-Magnetik

Keunggulan Pelat Permukaan Granit

First, the rock after a long period of natural aging, uniform structure, coefficient minimum, the internal stress completely disappear, not deformed, so the precision is high.

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Precision Granite Base Can Improve Machine Tool Performances

Requirements are constantly increasing in mechanical engineering in general and in machine tool construction in particular. Achieving maximum precision and performance values without increasing costs are constant challenges to being competitive. The machine tool bed is a decisive factor here. Therefore, more and more machine tool manufacturers are relying on granite. Due to its physical parameters, it offers clear advantages that cannot be achieved with steel or polymer concrete.

Granite is a so-called volcanic deep rock and has a very dense and homogeneous structure with an extremely low coefficient of expansion, low thermal conductivity and high vibration damping.

Below you will discover why the common opinion that granite is mainly only suitable as machine base for high-end coordinate measuring machines is long outdated and why this natural material as a machine tool base is a very advantageous alternative to steel or cast iron even for high-precision machine tools.

We can manufacture granite components for dynamic motion, granite components for linear motors, granite components for ndt, granite components for xray, granite components for cmm, granite components for cnc, granite precision for laser, granite components for aerospace, granite components for precision stages...

High Added Value Without Additional Costs
The increasing use of granite in mechanical engineering is not so much due to the massive increase in the price of steel. Rather, it is because the added value for the machine tool achieved with a machine bed made of granite is possible at very little or no extra cost. This is proven by cost comparisons of well-known machine tool manufacturers in Germany and Europe.

The considerable gain in thermodynamic stability, vibration damping and long-term precision made possible by granite cannot be achieved with a cast iron or steel bed, or only at relatively high cost. For example, thermal errors can account for up to 75% of the total error of a machine, with compensation often attempted for by software – with moderate success. Due to its low thermal conductivity, granite is the better foundation for long-term precision.

With a tolerance of 1 μm, granite easily meets the flatness requirements according to DIN 876 for the degree of accuracy 00. With a value of 6 on the hardness scale 1 to 10, it is extremely hard, and with its specific weight of 2.8g/cm³ it almost reaches the value of aluminium. This also results in additional advantages such as higher feed rates, higher axis accelerations and an extension of the tool life for cutting machine tools. Thus, the change from a cast bed to a granite machine bed moves the machine tool in question into the high-end class in terms of precision and performance – at no extra cost.

Granite’s Improved Ecological Footprint
In contrast to materials such as steel or cast iron, natural stone does not have to be produced with a great deal of energy and using additives. Only relatively small amounts of energy are required for quarrying and surface treatment. This results in a superior ecological footprint, which even at the end of a machine’s life surpasses that of steel as a material. The granite bed can be the basis for a new machine or be used for completely different purposes such as shredding for road construction.

Nor are there any shortages of resources for granite. It is a deep rock formed from magma within the earth’s crust. It has ‘matured’ for millions of years and is available in very large quantities as a natural resource on almost all continents, including all of Europe.

Conclusion: The numerous demonstrable advantages of granite compared to steel or cast iron justify the increasing willingness of mechanical engineers to use this natural material as a foundation for high-precision, high-performance machine tools. Detailed information about granite properties, which are advantageous for machine tools and mechanical engineering, can be found in this further article.

A repeat measurement is a measurement of local flatness areas. The Repeat Measurement specification states that a measurement taken anywhere on the surface of a plate will repeat within the stated tolerance. Controlling local area flatness tighter than overall flatness guarantees a gradual change in surface flatness profile thereby minimizing local errors.

Most manufacturers, including imported brands, adhere to the Federal Specification of overall flatness tolerances but many overlook the repeat measurements. Many of the low value or budget plates available in the market today will not guarantee repeat measurements. A manufacturer who does not guarantee repeat measurements is NOT producing plates that meet the requirements of ASME B89.3.7-2013 or Federal Specification GGG-P-463c, or DIN 876, GB, JJS...

Both are critical to ensure a precision surface for accurate measurements. Flatness specification alone is not sufficient to guarantee measurement accuracy. Take as an example, a 36 X 48 Inspection Grade A surface plate, which meets ONLY the flatness specification of .000300". If the piece being checked bridges several peaks, and the gage being used is in a low spot, the measurement error could be the full tolerance in one area, 000300"! Actually, it can be much higher if the gage is resting on the slope of an incline.

Errors of .000600"-.000800" are possible, depending upon the severity of the slope, and the arm length of the gage being used. If this plate had a Repeat Measurement specification of .000050"F.I.R. then the measurement error would be less than .000050" regardless of where the measurement is taken on the plate. Another problem, which usually arises when an untrained technician attempts to resurface a plate on-site, is the use of Repeat Measurements alone to certify a plate.

The instruments that are used to verify repeatability are NOT designed to check overall flatness. When set to zero on a perfectly curved surface, they will continue to read zero, whether that surface is perfectly flat or perfectly concave or convex 1/2"! They simply verify the uniformity of the surface, not the flatness. Only a plate that meets both the flatness specification AND the repeat measurement specification truly meets the requirements of ASME B89.3.7-2013  or Federal Specification GGG-P-463c.

Ask us about or flatness specification and repeat measurement promise by calling +86 19969991659 or emailing INFO@ZHHIMG.COM

Yes, but they can only be guaranteed for a specific vertical temperature gradient. The effects of thermal expansion on the plate could easily cause a change in accuracy greater than the tolerance if there is a change in the gradient. In some cases, if the tolerance is tight enough, the heat absorbed from overhead lighting can cause enough of a gradient change over several hours.

Granite has a coefficient of thermal expansion of approximately .0000035 inches per inch per 1°F. As an example: A 36" x 48" x 8" surface plate has an accuracy of .000075" (1/2 of Grade AA) at a gradient of 0°F, the top and bottom are the same temperature. If the top of the plate warms up to the point where it is 1°F warmer than the bottom, the accuracy would change to .000275" convex ! Therefore, ordering a plate with a tolerance tighter than Laboratory Grade AA should only be considered if there is adequate climate control.

A surface plate should be supported at 3 points, ideally located 20% of the length in from the ends of the plate. Two supports should be located 20% of the width in from the long sides, and the remaining support should be centered. Only 3 points can rest solidly on anything but a precision surface.

The plate should be supported at these points during production, and it should be supported only at these three points while in use. Attempting to support the plate at more than three points will cause the plate to receive its support from various combinations of three points, which will not be the same 3 points on which it was supported during production. This will introduce errors as the plate deflects to conform to the new support arrangement. All zhhimg steel stands have support beams designed to line up with the proper support points.

If the plate is properly supported, precise leveling is only necessary if your application calls for it. Leveling is not necessary to maintain the accuracy of a properly supported plate.

Why Choose Granite for Machine Bases and Metrology Components?

The answer is 'yes' for almost every application. The advantages of granite include: No rust or corrosion, almost immune to warping, no compensating hump when nicked, longer wear life, smoother action, greater precision, virtually non-magnetic, low co-efficient of thermal expansion, and low maintenance cost.

Granite is a type of igneous rock quarried for its extreme strength, density, durability, and resistance to corrosion. But granite is also very versatile– it’s not just for squares and rectangles! In fact, Starrett Tru-Stone confidently works with granite components engineered in shapes, angles, and curves of all variations on a regular basis—with excellent outcomes.

Through our state of the art processing, cut surfaces can be exceptionally flat. These qualities make granite the ideal material to create custom-size and custom-design machine bases and metrology components. Granite is:

machineable
precisely flat when cut and finished
rust resistant
durable
long lasting
Granite components are also easy to clean. When creating custom designs, be sure to choose granite for its superior benefits.

STANDARDS / HIGH WEAR APPLICATIONS
The granite utilized by ZhongHui for our standard surface plate products has high quartz content, which provides greater resistance to wear and damage. Our Superior Black and Crystal Pink colors have low water absorption rates, minimizing the possibility of your precision gages rusting while setting on the plates. The colors of granite offered by ZhongHui result in less glare, which means less eyestrain for individuals using the plates. We have chosen our granite types while considering thermal expansion in an effort to keep this aspect minimal.

CUSTOM APPLICATIONS
When your application calls for a plate with custom shapes, threaded inserts, slots or other machining, you’ll want to select a material like Black Diabase. This natural material offers superior stiffness, excellent vibration dampening, and improved machinability.

Yes, if they are not too badly worn. Our factory setting and equipment allow the optimum conditions for proper plate calibration and rework if necessary. Generally, if a plate is within .001" of the required tolerance, it can be resurfaced on-site. If a plate is worn to the point where it is more than .001" out of tolerance, or if it is badly pitted or nicked, then it will need to be sent to the factory for grinding prior to relapping.

Great care should be exercised in selecting an on-site calibration and resurfacing technician. We urge you to use caution in selecting your calibration service. Ask for accreditation and verify the equipment that the technician will use has a National Inspection Institution traceable calibration. It takes many years to learn how to properly lap precision granite.

ZhongHui provides quick turn-around on calibrations performed in our factory. Send your plates in for calibration if possible. Your quality and reputation depend on the accuracy of your measurement instruments including surface plates!

Our black surface plates have a significantly higher density and are up to three times as stiff. Therefore, a plate made of the black does not need to be as thick as a granite plate of the same size to have equal or greater resistance to deflection. Reduced thickness means less weight and lower shipping costs.

Beware of others who use lower quality black granite in the same thickness. As stated above, properties of granite, like wood or metal, vary by material and color, and is not an accurate predictor of stiffness, hardness, or wear resistance. In fact, many types of black granite and diabase are very soft and not suitable for surface plate applications.

No. The specialized equipment and training necessary to rework these items requires that they be returned to the factory for calibration and rework.

Yes. Ceramic and granite have similar characteristics, and the methods used to calibrate and lap granite can be used with ceramic items as well. Ceramics are more difficult to lap than granite resulting in a higher cost.

Yes, provided that the inserts are recessed below the surface. If steel inserts are flush with, or above the surface plane, they must be spot-faced down before the plate can be lapped. If required, we can provide that service.

Yes. Steel inserts with the desired thread (English or metric) can be epoxy bonded into the plate at the desired locations. ZhongHui uses CNC machines to provide the tightest insert locations within +/- 0.005”. For less critical inserts, our locational tolerance for threaded inserts is ±.060". Other options include steel T-Bars and dovetail slots machined directly into the granite.

Inserts that are properly bonded using high strength epoxy and good workmanship will withstand a great deal of torsional and shear force. In a recent test, using 3/8"-16 threaded inserts, an independent testing laboratory measured the force required to pull an epoxy-bonded insert from a surface plate. Ten plates were tested. Out of these ten, in nine cases, the granite fractured first. The average load at the point of failure was 10,020 lbs. for gray granite and 12,310 lbs. for black. In the single case where an insert pulled free of the plate, the load at the point of failure was 12,990 lbs.! If a work piece forms a bridge across the insert and extreme torque is applied, it is possible to generate enough force to fracture the granite. Partially for this reason, ZhongHui gives guidelines for the maximum safe torque that can be applied the epoxy bonded inserts: https://www.zhhimg.com/standard-thread-inserts-product/

Yes, but only at our factory. At our plant, we can restore almost any plate to 'like-new' condition, usually for less than half the cost of replacing it. Damaged edges can be cosmetically patched, deep grooves, nicks, and pits can be ground out, and the attached supports can be replaced. In addition, we can modify your plate to increase its versatility by adding solid or threaded steel inserts and cutting slots or clamping lips, per your specifications.

Why Choose Granite?
Granite is a type of igneous rock formed in the Earth millions of years ago. The composition of igneous rock contained many minerals such as quartz that is extremely hard and wear-resistant. In addition to hardness and wear resistance granite has approximately half the coefficient of expansion as cast iron. As its volumetric weight is approximately one third that of cast iron, granite is easier to manoeuvre.

For machine bases and metrology components, black granite is the colour most used. Black granite has a higher percentage of quartz than other colours and is, therefore, the hardest wearing.

Granite is cost-effective, and cut surfaces can be exceptionally flat. Not only can it be hand lapped to achieve extremes of accuracy, but re-conditioning can be performed without moving the plate or table off-site. It is entirely a hand lapping operation and generally costs much less than re-conditioning a cast iron alternative.

These qualities make granite the ideal material to create custom-size and custom-design machine bases and metrology components such as the granite surface plate.

ZhongHui produces bespoke granite products that are created to support specific measurement requirements. These bespoke items vary from straight edges to tri squares. Due to the versatile nature of granite, the components can be produced to any size required; they are hard wearing and long-lasting.

Advantages of Granite Surface Plates
The importance of measuring on an even surface was established by British inventor Henry Maudsley in the 1800s. As a machine tool innovator, he determined that consistent production of parts required a solid surface for reliable measurements.

The industrial revolution created a demand for measuring surfaces, so engineering company Crown Windley created manufacturing standards. The standards for surface plates were first set by Crown in 1904 using metal. As the demand and cost for metal increased, alternative materials for the measuring surface were investigated.

In America, monument creator Wallace Herman established that black granite was an excellent surface plate material alternative to metal. As granite is non-magnetic and doesn’t rust, it soon became the preferred measuring surface.

A granite surface plate is an essential investment for laboratories and test facilities. A granite surface plate of 600 x 600 mm can be mounted on a support stand. The stands provide a working height of 34” (0.86m) with five adjustable points for levelling.

For reliable and consistent measurement results, a granite surface plate is crucial. As the surface is a smooth and stable plane, it enables instruments to be carefully manipulated.

The main advantages of granite surface plates are:

• Non-reflective
• Resistant to chemicals and corrosion
• Low coefficient of expansion compared with cart iron so less affected by temperature change
• Naturally rigid and hard-wearing
• The plane of the surface is unaffected if scratched
• Will not rust
• Non-magnetic
• Easy to clean and maintain
• Calibration and resurfacing can be done onsite
• Suitable for drilling for threaded support inserts
• High vibration damping

For many shops, inspection rooms and laboratories, precision granite surface plates are relied on as the basis for accurate measurement. Because every linear measurement depends on an accurate reference surface from which final dimensions are taken, surface plates provide the best reference plane for work inspection and layout prior to machining. They also are ideal bases for making height measurements and gaging surfaces. Further, a high degree of flatness, stability, overall quality and workmanship make them a good choice for mounting sophisticated mechanical, electronic and optical gaging systems. For any of these measurement processes, it is imperative to keep surface plates calibrated.

Repeat Measurements and Flatness
Both flatness and repeat measurements are critical to ensure a precision surface. Flatness can be considered as all points on the surface being contained within two parallel planes, the base plane and the roof plane. The measurement of distance between the planes is the overall flatness of the surface. This flatness measurement commonly carries a tolerance and may include a grade designation.

The flatness tolerances for three standard grades are defined in the federal specification as determined by the following formula:
Laboratory Grade AA = (40 + diagonal² / 25) x 0.000001 inch (unilateral)
Inspection Grade A = Laboratory Grade AA x 2
Tool Room Grade B = Laboratory Grade AA x 4

In addition to flatness, repeatability must be ensured. A repeat measurement is a measurement of local flatness areas. It is a measurement taken anywhere on the surface of a plate that will repeat within the stated tolerance. Controlling local area flatness to a tighter tolerance than overall flatness guarantees a gradual change in surface flatness profile, thereby minimizing local errors.

To ensure a surface plate meets both the flatness and repeat measurement specifications, manufacturers of granite surface plates should use Federal Specification GGG-P-463c as a basis for their specifications. This standard addresses repeat measurement accuracy, material properties of surface plate granites, surface finish, support point location, stiffness, acceptable methods of inspection and installation of threaded inserts.

Before a surface plate has worn beyond specification for overall flatness, it will show worn or wavy posts. Monthly inspection for repeat measurement errors using a repeat reading gage will identify wear spots. A repeat reading gage is a high-precision instrument that detects local error and can be displayed on a high magnification electronic amplifier.

Checking Plate Accuracy
By following a few simple guidelines, an investment in a granite surface plate should last for many years. Depending on plate usage, shop environment and required accuracy, frequency of checking the surface plate accuracy varies. A general rule of thumb is for a new plate to receive a full recalibration within one year of purchase. If the plate is used frequently, it is advisable to shorten this interval to six months.

Before a surface plate has worn beyond specification for overall flatness, it will show worn or wavy posts. Monthly inspection for repeat measurement errors using a repeat reading gage will identify wear spots. A repeat reading gage is a high-precision instrument that detects local error and can be displayed on a high magnification electronic amplifier.

An effective inspection program should include regular checks with an autocollimator, providing actual calibration of overall flatness traceable to National Institute of Standards and Technology (NIST). Comprehensive calibration by the manufacturer or an independent company is necessary from time to time.

Variations Between Calibrations
In some cases, there are variations between surface plate calibrations. Sometimes factors such as surface change resulting from wear, incorrect use of inspection equipment or use of noncalibrated equipment can account for these variations. The two most common factors, however, are temperature and support.

One of the most important variables is temperature. For instance, the surface might have been washed with a hot or cold solution prior to calibration and not allowed sufficient time to normalize. Other causes of temperature change include drafts of cold or hot air, direct sunlight, overhead lighting or other sources of radiant heat on the surface of the plate.

There also can be variations in the vertical temperature gradient between winter and summer. In some cases, the plate is not allowed sufficient time to normalize after shipment. It is a good idea to record the vertical gradient temperature at the time the calibration is performed.

Another common cause for calibration variation is a plate that is improperly supported. A surface plate should be supported at three points, ideally located 20% of the length in from the ends of the plate. Two supports should be located 20% of the width in from the long sides, and the remaining support should be centered.

Only three points can rest solidly on anything but a precision surface. Attempting to support the plate at more than three points will cause the plate to receive its support from various combinations of three points, which will not be the same three points on which it was supported during production. This will introduce errors as the plate deflects to conform to the new support arrangement. Consider using steel stands with support beams designed to line up with the proper support points. Stands for this purpose are generally available from the surface plate manufacturer.

If the plate is properly supported, precise leveling is only necessary if an application specifies it. Leveling is not necessary to maintain the accuracy of a properly supported plate.

It is important to keep the plate clean. Airborne abrasive dust is usually the greatest source of wear and tear on a plate, as it tends to embed in workpieces and the contact surfaces of gages. Cover plates to protect them from dust and damage. Wear life can be extended by covering the plate when not in use.

Extend Plate Life
Following a few guidelines will reduce wear on a granite surface plate and ultimately, extend its life.

First, it is important to keep the plate clean. Airborne abrasive dust is usually the greatest source of wear and tear on a plate, as it tends to embed in workpieces and the contact surfaces of gages.

It also is important to cover plates to protect it from dust and damage. Wear life can be extended by covering the plate when not in use.

Rotate the plate periodically so that a single area does not receive excessive use. Also, it is recommended to replace steel contact pads on gaging with carbide pads.

Avoid setting food or soft drinks on the plate. Many soft drinks contain either carbonic or phosphoric acid, which can dissolve the softer minerals and leave small pits in the surface.

Where to Relap
When a granite surface plate needs re-surfacing, consider whether to have this service performed on-site or at the calibration facility. It is always preferable to have the plate relapped at the factory or a dedicated facility. If, however, the plate is not too badly worn, generally within 0.001 inch of the required tolerance, it can be resurfaced on-site. If a plate is worn to the point where it is more than 0.001 inch out of tolerance, or if it is badly pitted or nicked, then it should be sent to the factory for grinding prior to relapping.

A calibration facility has the equipment and factory setting providing the optimum conditions for proper plate calibration and rework if necessary.

Great care should be exercised in selecting an on-site calibration and resurfacing technician. Ask for accreditation and verify the equipment that the technician will use has a NIST-traceable calibration. Experience also is an important factor, as it takes many years to learn how to correctly lap precision granite.

Critical measurements start with a precision granite surface plate as a baseline. By ensuring a reliable reference by using a properly calibrated surface plate, manufacturers have one of the essential tools for reliable measurements and better quality parts.

Checklist for Calibration Variations

1. The surface was washed with a hot or cold solution prior to calibration and was not allowed sufficient time to normalize.
2. The plate is improperly supported.
3. Temperature change.
4. Drafts.
5. Direct sunlight or other radiant heat on the surface of the plate. Be sure that overhead lighting is not heating the surface.
6. Variations in the vertical temperature gradient between winter and summer. If at all possible, know the vertical gradient temperature at the time the calibration is performed.
7. Plate not allowed sufficient time to normalize after shipment.
8. Improper use of inspection equipment or use of noncalibrated equipment.
9. Surface change resulting from wear.

Tech Tips
Because every linear measurement depends on an accurate reference surface from which final dimensions are taken, surface plates provide the best reference plane for work inspection and layout prior to machining.

Controlling local area flatness to a tighter tolerance than overall flatness guarantees a gradual change in surface flatness profile, thereby minimizing local errors.