گرينائيٽ هڪ قسم جو آتشي پٿر آهي جيڪو ان جي انتهائي طاقت، کثافت، استحڪام، ۽ سنکنرن جي مزاحمت لاءِ کوٽيو ويندو آهي. پر گرينائيٽ پڻ تمام ورسٽائل آهي - اهو صرف چورس ۽ مستطيل لاءِ ناهي! حقيقت ۾، اسان اعتماد سان گرينائيٽ حصن سان باقاعده بنيادن تي سڀني تبديلين جي شڪلن، زاوين ۽ وکر ۾ انجنيئر ٿيل ڪم ڪريون ٿا - بهترين نتيجن سان.
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:
■ مشيني
■ ڪٽڻ ۽ ختم ٿيڻ تي بلڪل سڌو
■ زنگ جي مزاحمتي
■ پائيدار
■ ڊگهي عرصي وارو
گرينائيٽ جا حصا صاف ڪرڻ ۾ پڻ آسان آهن. ڪسٽم ڊيزائن ٺاهڻ وقت، پڪ ڪريو ته گرينائيٽ کي ان جي بهترين فائدن لاءِ چونڊيو.

معيار / هاءِ ويئر ايپليڪيشنون
ZHHIMG پاران اسان جي معياري مٿاڇري واري پليٽ جي شين لاءِ استعمال ٿيندڙ گرينائيٽ ۾ ڪوارٽز جو مقدار وڌيڪ آهي، جيڪو پائڻ ۽ نقصان جي مزاحمت کي وڌيڪ فراهم ڪري ٿو. اسان جي اعليٰ ڪاري رنگن ۾ پاڻي جذب ڪرڻ جي شرح گهٽ آهي، جيڪا پليٽن تي سيٽنگ دوران توهان جي درست گيجز جي زنگ لڳڻ جي امڪان کي گهٽ ڪري ٿي. ZHHIMG پاران پيش ڪيل گرينائيٽ جا رنگ گهٽ چمڪ جو نتيجو ڏين ٿا، جنهن جو مطلب آهي پليٽون استعمال ڪندڙ ماڻهن لاءِ اکين جي تڪليف گهٽ. اسان هن پهلو کي گهٽ ۾ گهٽ رکڻ جي ڪوشش ۾ حرارتي توسيع تي غور ڪندي پنهنجي گرينائيٽ جي قسمن کي چونڊيو آهي.

CUSTOM APPLICATIONS
جڏهن توهان جي ايپليڪيشن ۾ ڪسٽم شڪلن، ٿريڊ انسرٽس، سلاٽس يا ٻي مشيننگ سان پليٽ جي ضرورت هجي، ته توهان کي بليڪ جنان بليڪ جهڙو مواد چونڊڻ گهرجي. هي قدرتي مواد بهترين سختي، بهترين وائبريشن ڊمپننگ، ۽ بهتر مشيني صلاحيت پيش ڪري ٿو.

اهو نوٽ ڪرڻ ضروري آهي ته صرف رنگ پٿر جي جسماني خوبين جو اشارو نه آهي. عام طور تي، گرينائيٽ جو رنگ سڌو سنئون معدنيات جي موجودگي يا غير موجودگي سان لاڳاپيل آهي، جنهن جو شايد انهن خوبين تي ڪو به اثر نه هجي جيڪي سٺي مٿاڇري جي پليٽ مواد ٺاهين ٿيون. گلابي، گرين، ۽ ڪارا گرينائيٽ آهن جيڪي مٿاڇري جي پليٽن لاءِ بهترين آهن، انهي سان گڏ ڪارا، گرين، ۽ گلابي گرينائيٽ آهن جيڪي درست ايپليڪيشنن لاءِ مڪمل طور تي نا مناسب آهن. گرينائيٽ جون اهم خاصيتون، جيئن اهي مٿاڇري جي پليٽ مواد جي طور تي ان جي استعمال سان لاڳاپيل آهن، انهن جو رنگ سان ڪو به تعلق ناهي، ۽ هيٺ ڏنل آهن:
■ سختي (لوڊ هيٺ انحراف - لچڪ جي ماڊيولس پاران ظاهر ڪيل)
■ سختي
■ کثافت
■ لباس جي مزاحمت
■ استحڪام
■ پورسيٽي

اسان ڪيترن ئي گرينائيٽ مواد کي آزمايو آهي ۽ انهن مواد جو مقابلو ڪيو آهي. آخرڪار اسان کي نتيجو ملي ٿو، جنان ڪارو گرينائيٽ بهترين مواد آهي جيڪو اسان ڪڏهن به ڄاڻون ٿا. انڊين ڪارو گرينائيٽ ۽ ڏکڻ آفريقي گرينائيٽ جنان ڪارو گرينائيٽ سان ملندڙ جلندڙ آهن، پر انهن جون جسماني خاصيتون جنان ڪارو گرينائيٽ کان گهٽ آهن. ZHHIMG دنيا ۾ وڌيڪ گرينائيٽ مواد جي ڳولا ڪندو رهندو ۽ انهن جي جسماني ملڪيتن جو مقابلو ڪندو.

توهان جي منصوبي لاءِ صحيح گرينائيٽ بابت وڌيڪ ڳالهائڻ لاءِ، مهرباني ڪري اسان سان رابطو ڪريو.info@zhhimg.com.

مختلف ٺاهيندڙ مختلف معيار استعمال ڪندا آهن. دنيا ۾ ڪيترائي معيار آهن.
DIN معيار، ASME B89.3.7-2013 يا وفاقي وضاحت GGG-P-463c (گرينائيٽ مٿاڇري پليٽون) ۽ انهي جي بنياد تي انهن جي وضاحتن جي بنياد تي.

۽ اسان توهان جي گهرجن مطابق گرينائيٽ جي درستگي جي چڪاس واري پليٽ تيار ڪري سگهون ٿا. جيڪڏهن توهان وڌيڪ معيارن بابت وڌيڪ معلومات ڄاڻڻ چاهيو ٿا ته اسان سان رابطو ڪرڻ ۾ ڀليڪار.

هموار هجڻ کي مٿاڇري تي سڀني نقطن کي ٻن متوازي جهازن، بنيادي جهاز ۽ ڇت جي جهاز اندر شامل سمجهي سگهجي ٿو. جهازن جي وچ ۾ فاصلي جي ماپ مٿاڇري جي مجموعي هموار هجڻ آهي. هي هموار هجڻ جي ماپ عام طور تي هڪ برداشت رکي ٿي ۽ ان ۾ گريڊ جو عهدو شامل ٿي سگهي ٿو.

مثال طور، ٽن معياري گريڊن لاءِ فليٽنس رواداري وفاقي وضاحت ۾ بيان ڪئي وئي آهي جيئن هيٺ ڏنل فارمولا ذريعي طئي ڪئي وئي آهي:
■ ليبارٽري گريڊ AA = (40 + ڊاگونل اسڪوائر/25) x .000001" (هڪ طرفو)
■ انسپيڪشن گريڊ A = ليبارٽري گريڊ AA x 2
■ ٽول روم گريڊ B = ليبارٽري گريڊ AA x 4.

معياري سائيز جي مٿاڇري جي پليٽن لاءِ، اسان فليٽنس رواداري جي ضمانت ڏيون ٿا جيڪي هن وضاحت جي گهرجن کان وڌيڪ آهن. فليٽنس کان علاوه، ASME B89.3.7-2013 ۽ وفاقي وضاحت GGG-P-463c موضوعن کي خطاب ڪن ٿا جن ۾ شامل آهن: بار بار ماپ جي درستگي، مٿاڇري پليٽ گرينائيٽ جي مادي خاصيتون، مٿاڇري ختم، سپورٽ پوائنٽ جي جڳهه، سختي، معائني جا قابل قبول طريقا، ٿريڊ انسرٽس جي انسٽاليشن، وغيره.

ZHHIMG گرينائيٽ مٿاڇري جون پليٽون ۽ گرينائيٽ انسپيڪشن پليٽون هن وضاحت ۾ بيان ڪيل سڀني گهرجن کي پورو ڪن ٿيون يا انهن کان وڌيڪ آهن. في الحال، گرينائيٽ اينگل پليٽس، متوازي، يا ماسٽر اسڪوائر لاءِ ڪا به وضاحتي وضاحت موجود ناهي.

۽ توهان ٻين معيارن لاءِ فارمولا ڳولي سگهو ٿاڊائون لوڊ.

پهرين، پليٽ کي صاف رکڻ ضروري آهي. هوا ۾ اُڀرندڙ مٽي عام طور تي پليٽ تي ٽٽڻ ۽ ڦاٽڻ جو سڀ کان وڏو ذريعو آهي، ڇاڪاڻ ته اهو ڪم جي ٽڪرن ۽ گيجز جي رابطي جي سطحن ۾ داخل ٿئي ٿو. ٻيو، پنهنجي پليٽ کي مٽي ۽ نقصان کان بچائڻ لاءِ ان کي ڍڪيو. استعمال ۾ نه هجڻ تي پليٽ کي ڍڪڻ سان، پليٽ کي وقت بوقت گھمائي، ۽ گيجنگ تي اسٽيل ڪانٽيڪٽ پيڊ کي ڪاربائيڊ پيڊ سان تبديل ڪرڻ سان لباس جي زندگي وڌائي سگهجي ٿي. ان کان علاوه، پليٽ تي کاڌو يا نرم مشروبات رکڻ کان پاسو ڪريو. نوٽ ڪريو ته ڪيترن ئي نرم مشروبات ۾ ڪاربونڪ يا فاسفورڪ ايسڊ هوندو آهي، جيڪو نرم معدنيات کي ڦهلائي سگهي ٿو ۽ مٿاڇري ۾ ننڍا کڏا ڇڏي سگهي ٿو.

اهو ان تي منحصر آهي ته پليٽ ڪيئن استعمال ٿي رهي آهي. جيڪڏهن ممڪن هجي ته، اسان سفارش ڪريون ٿا ته پليٽ کي ڏينهن جي شروعات ۾ (يا ڪم جي شفٽ ۾) ۽ ٻيهر آخر ۾ صاف ڪيو وڃي. جيڪڏهن پليٽ مٽي ٿي وڃي، خاص طور تي تيل يا چپچپا سيال سان، ته ان کي فوري طور تي صاف ڪرڻ گهرجي.

پليٽ کي باقاعدي طور تي مائع يا ZHHIMG پاڻي کان سواءِ مٿاڇري واري پليٽ ڪلينر سان صاف ڪريو. صفائي جي حلن جو انتخاب اهم آهي. جيڪڏهن ڪو غير مستحڪم محلول استعمال ڪيو وڃي (ايسيٽون، لکير ٿنڀو، الڪوحل، وغيره) ته بخارات مٿاڇري کي ٿڌو ڪري ڇڏيندو، ۽ ان کي بگاڙي ڇڏيندو. هن صورت ۾، پليٽ کي استعمال ڪرڻ کان اڳ ان کي معمول تي آڻڻ ضروري آهي، نه ته ماپ جون غلطيون ٿينديون.

پليٽ کي نارمل ڪرڻ لاءِ گهربل وقت پليٽ جي سائيز ۽ ٿڌي ٿيڻ جي مقدار سان مختلف هوندو. ننڍين پليٽن لاءِ هڪ ڪلاڪ ڪافي هجڻ گهرجي. وڏين پليٽن لاءِ ٻه ڪلاڪ گهربل ٿي سگهن ٿا. جيڪڏهن پاڻي تي ٻڌل ڪلينر استعمال ڪيو وڃي ته ڪجهه بخاراتي ٿڌي ٿيڻ پڻ ٿيندو.

پليٽ پاڻي کي به برقرار رکندي، ۽ ان جي ڪري مٿاڇري سان رابطي ۾ ڌاتو جي حصن تي زنگ لڳي سگهي ٿو. ڪجهه صاف ڪندڙ سڪي وڃڻ کان پوءِ هڪ چپچپا رهجي ويندا آهن، جيڪو هوا ۾ موجود مٽي کي راغب ڪندو، ۽ اصل ۾ ان کي گهٽائڻ بدران ان کي وڌائيندو.

هي پليٽ جي استعمال ۽ ماحول تي منحصر آهي. اسان سفارش ڪريون ٿا ته هڪ نئين پليٽ يا درست گرينائيٽ لوازمات کي خريداري جي هڪ سال اندر مڪمل ريڪيليبريشن ملي. جيڪڏهن گرينائيٽ جي مٿاڇري واري پليٽ کي تمام گهڻو استعمال ٿيندو، ته اهو صلاح ڏني وڃي ته هن وقفي کي ڇهن مهينن تائين گهٽايو وڃي. اليڪٽرانڪ ليول، يا ساڳي ڊوائيس استعمال ڪندي بار بار ماپ جي غلطين لاءِ مهيني معائنو ڪنهن به ترقي پذير لباس جي جڳهن کي ڏيکاريندو ۽ انجام ڏيڻ ۾ صرف ڪجهه منٽ لڳندا آهن. پهرين ريڪيليبريشن جا نتيجا طئي ٿيڻ کان پوءِ، ڪيليبريشن وقفو توهان جي اندروني معيار جي نظام جي اجازت يا ضرورت مطابق وڌايو يا ننڍو ڪري سگهجي ٿو.

اسان توهان جي گرينائيٽ مٿاڇري جي پليٽ جو معائنو ۽ حساب ڪرڻ ۾ مدد لاءِ خدمت پيش ڪري سگهون ٿا.

ڪيليبريشن جي وچ ۾ فرق جا ڪيترائي ممڪن سبب آهن:

• ڪيليبريشن کان اڳ مٿاڇري کي گرم يا ٿڌي محلول سان ڌوتو ويو، ۽ ان کي نارمل ڪرڻ لاءِ ڪافي وقت نه ڏنو ويو.
• پليٽ کي غلط طريقي سان سپورٽ ڪيو ويو آهي.
• گرمي پد ۾ تبديلي
• ڊرافٽس
• پليٽ جي مٿاڇري تي سڌي سج جي روشني يا ٻي چمڪندڙ گرمي. پڪ ڪريو ته مٿي جي روشني مٿاڇري کي گرم نه ڪري رهي آهي.
• سياري ۽ اونهاري جي وچ ۾ عمودي گرمي پد جي درجي ۾ تبديليون (جيڪڏهن ممڪن هجي ته، ڪيليبريشن جي وقت عمودي درجه حرارت جي درجه حرارت کي ڄاڻو.)
• شپمينٽ کان پوءِ پليٽ کي معمول تي اچڻ لاءِ ڪافي وقت نه ڏنو ويو.
• معائني جي سامان جو غلط استعمال يا غير ڪيليبريٽ ٿيل سامان جو استعمال
• پائڻ جي نتيجي ۾ مٿاڇري ۾ تبديلي

درست گرينائيٽ تي ڪيترا قسم جا سوراخ آهن؟

پريسيشن گرينائيٽ حصن تي سلاٽ

ڪيترين ئي ڪارخانن، انسپيڪشن رومن ۽ ليبارٽرين لاءِ، درست ماپ لاءِ بنياد طور درست گرينائيٽ مٿاڇري جي پليٽن تي ڀروسو ڪيو ويندو آهي. ڇاڪاڻ ته هر لڪير جي ماپ هڪ صحيح حوالي واري مٿاڇري تي منحصر آهي جنهن مان آخري طول و عرض ورتو ويندو آهي، مٿاڇري پليٽون مشيننگ کان اڳ ڪم جي چڪاس ۽ ترتيب لاءِ بهترين حوالو جهاز فراهم ڪن ٿيون. اهي اوچائي جي ماپ ۽ گيجنگ مٿاڇريون ٺاهڻ لاءِ مثالي بنياد پڻ آهن. وڌيڪ، هڪ اعليٰ درجي جي برابري، استحڪام، مجموعي معيار ۽ ڪاريگري انهن کي جديد ميڪيڪل، اليڪٽرانڪ ۽ آپٽيڪل گيجنگ سسٽم لڳائڻ لاءِ هڪ سٺو انتخاب بڻائي ٿي. انهن مان ڪنهن به ماپ جي عمل لاءِ، مٿاڇري پليٽن کي ڪيليبريٽ رکڻ ضروري آهي.

Repeat Measurements and Flatness

درست مٿاڇري کي يقيني بڻائڻ لاءِ برابري ۽ ورجائي ماپ ٻئي اهم آهن. برابري کي سمجهي سگهجي ٿو ته مٿاڇري تي سڀئي نقطا ٻن متوازي جهازن، بنيادي جهاز ۽ ڇت جي جهاز ۾ شامل آهن. جهازن جي وچ ۾ فاصلي جي ماپ مٿاڇري جي مجموعي برابري آهي. هي برابري جي ماپ عام طور تي هڪ برداشت رکي ٿي ۽ ان ۾ گريڊ جو عهدو شامل ٿي سگهي ٿو.

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

ڊين معيار، جي بي معيار، اي ايس ايم اي معيار، جي جي ايس معيار... مختلف ملڪ مختلف موقف سان...

معيار بابت وڌيڪ تفصيل.

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.

انهي ڳالهه کي يقيني بڻائڻ لاءِ ته هڪ مٿاڇري پليٽ فليٽنس ۽ ورجائي ماپ جي وضاحتن کي پورو ڪري ٿي، گرينائيٽ مٿاڇري پليٽن جي ٺاهيندڙن کي پنهنجي وضاحتن جي بنياد طور فيڊرل اسپيسيفڪيشن GGG-P-463c استعمال ڪرڻ گهرجي. هي معيار بار بار ماپ جي درستگي، مٿاڇري پليٽ گرينائيٽ جي مادي خاصيتن، مٿاڇري جي ختم ٿيڻ، سپورٽ پوائنٽ جي جڳهه، سختي، معائني جا قابل قبول طريقا ۽ ٿريڊ انسرٽس جي انسٽاليشن کي خطاب ڪري ٿو.

Checking Plate Accuracy

ڪجھ سادي هدايتن تي عمل ڪندي، گرينائيٽ جي مٿاڇري واري پليٽ ۾ سيڙپڪاري ڪيترن سالن تائين رهڻ گهرجي. پليٽ جي استعمال، دڪان جي ماحول ۽ گهربل درستگي تي منحصر ڪري، مٿاڇري واري پليٽ جي درستگي جي جانچ جي تعدد مختلف هوندي آهي. هڪ عام اصول اهو آهي ته نئين پليٽ کي خريداري جي هڪ سال اندر مڪمل ريڪيليبريشن ملي وڃي. جيڪڏهن پليٽ کي بار بار استعمال ڪيو وڃي ٿو، ته اهو وقفو گهٽائي ڇهن مهينن تائين ڪرڻ جي صلاح ڏني ويندي آهي.

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

ڪجهه حالتن ۾، مٿاڇري جي پليٽ ڪيليبريشن جي وچ ۾ فرق هوندو آهي. ڪڏهن ڪڏهن عنصر جهڙوڪ مٿاڇري جي تبديلي جيڪا لباس جي نتيجي ۾ ٿيندي آهي، معائني جي سامان جو غلط استعمال يا غير ڪيليبريشن ٿيل سامان جو استعمال انهن فرقن جو سبب بڻجي سگهي ٿو. بهرحال، ٻه سڀ کان عام عنصر گرمي پد ۽ سپورٽ آهن.

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

ڪجھ هدايتن تي عمل ڪرڻ سان گرينائيٽ جي مٿاڇري واري پليٽ تي لباس گهٽجي ويندو ۽ آخرڪار، ان جي زندگي وڌندي.

پهرين، پليٽ کي صاف رکڻ ضروري آهي. هوا ۾ گھڙڻ واري مٽي عام طور تي پليٽ تي ٽٽڻ ۽ ڳوڙها جو سڀ کان وڏو ذريعو آهي، ڇاڪاڻ ته اهو ڪم جي ٽڪرن ۽ گيجز جي رابطي واري سطحن ۾ شامل ٿيڻ جو رجحان رکي ٿو.

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.

پليٽ کي وقت بوقت گھمايو ته جيئن هڪ حصي کي گهڻو استعمال نه ٿئي. ان سان گڏ، گيجنگ تي اسٽيل ڪانٽيڪٽ پيڊ کي ڪاربائيڊ پيڊ سان تبديل ڪرڻ جي سفارش ڪئي وئي آهي.

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

جڏهن گرينائيٽ جي مٿاڇري واري پليٽ کي ٻيهر مٿاڇري ڪرڻ جي ضرورت هجي، ته غور ڪريو ته ڇا هي خدمت سائيٽ تي ڪئي وڃي يا ڪيليبريشن سهولت تي. اهو هميشه بهتر آهي ته پليٽ کي ڪارخاني يا وقف ٿيل سهولت تي ٻيهر ليپ ڪيو وڃي. بهرحال، جيڪڏهن پليٽ تمام گهڻي خراب نه آهي، عام طور تي گهربل برداشت جي 0.001 انچ اندر، ان کي سائيٽ تي ٻيهر ليپ ڪري سگهجي ٿو. جيڪڏهن هڪ پليٽ ان نقطي تي پائي وئي آهي جتي اها برداشت کان 0.001 انچ کان وڌيڪ آهي، يا جيڪڏهن اها خراب طور تي پٽي يا نڪ ٿيل آهي، ته پوءِ ان کي ري ليپ ڪرڻ کان اڳ پيسڻ لاءِ ڪارخاني ڏانهن موڪليو وڃي.

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

سائيٽ تي ڪيليبريشن ۽ ري سرفيسنگ ٽيڪنيشن جي چونڊ ۾ تمام گهڻي احتياط ڪرڻ گهرجي. تصديق لاءِ پڇو ۽ تصديق ڪريو ته ٽيڪنيشن جيڪو سامان استعمال ڪندو ان ۾ ٽريس ايبل ڪيليبريشن آهي. تجربو پڻ هڪ اهم عنصر آهي، ڇاڪاڻ ته گرينائيٽ کي صحيح طريقي سان ليپ ڪرڻ سکڻ ۾ ڪيترائي سال لڳن ٿا.

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. ڪيليبريشن کان اڳ مٿاڇري کي گرم يا ٿڌي محلول سان ڌوتو ويو ۽ ان کي نارمل ٿيڻ لاءِ ڪافي وقت نه ڏنو ويو.

2. پليٽ کي غلط طريقي سان سهارو ڏنو ويو آهي.

3. گرمي پد ۾ تبديلي.

4. مسودا.

5. پليٽ جي مٿاڇري تي سڌي سج جي روشني يا ٻي چمڪندڙ گرمي. پڪ ڪريو ته مٿي جي روشني مٿاڇري کي گرم نه ڪري رهي آهي.

6. سياري ۽ اونهاري جي وچ ۾ عمودي گرمي پد جي درجي ۾ تبديليون. جيڪڏهن ممڪن هجي ته، ڪيليبريشن جي وقت عمودي درجه حرارت جي درجه حرارت کي ڄاڻو.

7. پليٽ کي ترسيل کان پوءِ معمول تي اچڻ لاءِ ڪافي وقت نه ڏنو ويو.

8. معائني جي سامان جو غلط استعمال يا غير ڪيليبريٽ ٿيل سامان جو استعمال.

9. پائڻ جي نتيجي ۾ مٿاڇري ۾ تبديلي.

Tech Tips

• ڇاڪاڻ ته هر لڪير جي ماپ هڪ صحيح ريفرنس مٿاڇري تي منحصر آهي جنهن مان آخري طول و عرض ورتا ويندا آهن، مٿاڇري جون پليٽون مشيننگ کان اڳ ڪم جي چڪاس ۽ ترتيب لاءِ بهترين ريفرنس جهاز فراهم ڪن ٿيون.
• Controlling local area flatness to a tighter tolerance than overall flatness guarantees a gradual change in surface flatness profile, thereby minimizing local errors.
• هڪ مؤثر معائنو پروگرام ۾ آٽو ڪوليميٽر سان باقاعده چڪاس شامل هجڻ گهرجي، جيڪا نيشنل انسپيڪشن اٿارٽي کي ٽريڪ ڪرڻ جي قابل مجموعي فليٽنس جي حقيقي ڪيليبريشن فراهم ڪري ٿي.

گرينائيٽ ٺاهڻ وارن معدني ذرڙن ۾، 90 سيڪڙو کان وڌيڪ فيلڊ اسپار ۽ ڪوارٽز آهن، جن مان فيلڊ اسپار سڀ کان وڌيڪ آهي. فيلڊ اسپار اڪثر ڪري اڇو، ڀورو، ۽ گوشت جهڙو ڳاڙهو هوندو آهي، ۽ ڪوارٽز گهڻو ڪري بي رنگ يا ڀورو اڇو هوندو آهي، جيڪو گرينائيٽ جو بنيادي رنگ ٺاهيندو آهي. فيلڊ اسپار ۽ ڪوارٽز سخت معدنيات آهن، ۽ اسٽيل جي چاقو سان حرڪت ڪرڻ ڏکيو آهي. جيئن ته گرينائيٽ ۾ ڪارا داغ، خاص طور تي ڪارو ابرڪ، ڪجهه ٻيا معدنيات آهن. جيتوڻيڪ بايو ٽائٽ نسبتاً نرم آهي، پر دٻاءُ جي مزاحمت ڪرڻ جي صلاحيت ڪمزور ناهي، ۽ ساڳئي وقت انهن جي گرينائيٽ ۾ ٿوري مقدار هوندي آهي، اڪثر 10 سيڪڙو کان گهٽ. هي مادي حالت آهي جنهن ۾ گرينائيٽ خاص طور تي مضبوط هوندو آهي.

گرينائيٽ جي مضبوط هجڻ جو هڪ ٻيو سبب اهو آهي ته ان جا معدني ذرڙا هڪ ٻئي سان مضبوطيءَ سان ڳنڍيل آهن ۽ هڪ ٻئي ۾ جڙيل آهن. سوراخ اڪثر ڪري پٿر جي ڪل مقدار جو 1٪ کان گهٽ هوندا آهن. هي گرينائيٽ کي مضبوط دٻاءُ برداشت ڪرڻ جي صلاحيت ڏئي ٿو ۽ نمي آساني سان داخل نه ٿي ٿئي.

گرينائيٽ جا حصا پٿر مان ٺهيل آهن جن ۾ ڪو به زنگ، تيزاب ۽ الڪلي مزاحمت، سٺي لباس مزاحمت ۽ ڊگهي خدمت زندگي نه آهي، ڪو به خاص سار سنڀال ناهي. گرينائيٽ جي درستگي جا حصا گهڻو ڪري مشينري صنعت جي ٽولنگ ۾ استعمال ٿيندا آهن. تنهن ڪري، انهن کي گرينائيٽ جي درستگي جا حصا يا گرينائيٽ جا حصا سڏيو ويندو آهي. گرينائيٽ جي درستگي جا حصا بنيادي طور تي گرينائيٽ پليٽ فارمن وانگر آهن. گرينائيٽ جي درستگي جي حصن جي ٽولنگ ۽ ماپ جو تعارف: درستگي جي مشيننگ ۽ مائڪرو مشيننگ ٽيڪنالاجي مشينري جي پيداوار جي صنعت جي اهم ترقي جون هدايتون آهن، ۽ اهي هڪ اعليٰ ٽيڪنالاجي جي سطح کي ماپڻ لاءِ هڪ اهم اشاري بڻجي چڪا آهن. جديد ٽيڪنالاجي ۽ دفاعي صنعت جي ترقي درستگي جي مشيننگ ۽ مائڪرو مشيننگ ٽيڪنالاجي کان الڳ نه ٿي سگهي ٿي. گرينائيٽ جا حصا ماپ ۾ آساني سان سلائيڊ ٿي سگهن ٿا، بغير جمود جي. ڪم جي مٿاڇري جي ماپ، عام خرابي ماپ جي درستگي کي متاثر نه ڪندا آهن. گرينائيٽ جي حصن کي طلب جي پاسي جي گهرجن مطابق ڊزائين ۽ پيدا ڪرڻ جي ضرورت آهي.

درخواست جو ميدان:

جيئن ته اسان سڀ ڄاڻون ٿا ته وڌيڪ کان وڌيڪ مشينون ۽ سامان درست گرينائيٽ اجزاء چونڊي رهيا آهن.

گرينائيٽ جا جزا متحرڪ حرڪت، لڪير موٽر، سي ايم ايم، سي اين سي، ليزر مشين لاءِ استعمال ٿيندا آهن...

وڌيڪ معلومات لاءِ اسان سان رابطو ڪرڻ ۾ ڀليڪار.

گرينائيٽ ماپڻ وارا ڊوائيس ۽ گرينائيٽ ميڪيڪل حصا اعليٰ معيار جي جنان بليڪ گرينائيٽ مان ٺهيل آهن. انهن جي اعليٰ درستگي، ڊگهي مدت، سٺي استحڪام ۽ سنکنرن جي مزاحمت جي ڪري، اهي جديد صنعت ۽ ميڪيڪل ايرو اسپيس ۽ سائنسي تحقيق جهڙن سائنسي شعبن جي پيداوار جي معائني ۾ وڌيڪ ۽ وڌيڪ استعمال ڪيا ويا آهن.

فائدا

----ٻه ڀيرا لوهه جيترو سخت؛

----طول و عرض ۾ گھٽ ۾ گھٽ تبديليون گرمي پد جي تبديلين جي ڪري آهن؛

---- وڄڻ کان پاڪ، تنهنڪري ڪم ۾ خلل نه پوي؛

---- باریک اناج جي بناوت ۽ غير معمولي چپڪ جي ڪري، دڙن يا پروٽريشن کان پاڪ، جيڪو ڊگهي خدمت جي زندگي دوران اعليٰ درجي جي برابري کي يقيني بڻائي ٿو ۽ ٻين حصن يا اوزارن کي ڪو به نقصان نه پهچائيندو آهي؛

----مقناطيسي مواد سان استعمال لاءِ تڪليف کان پاڪ آپريشن؛

----ڊگھي زندگي ۽ زنگ کان پاڪ، نتيجي ۾ گهٽ سار سنڀال جي قيمت.

درستگي حاصل ڪرڻ لاءِ درستگي حاصل ڪرڻ لاءِ گرينائيٽ جي مٿاڇري واري پليٽن کي فليٽ جي اعليٰ معيار تي درستگي سان ليپ ڪيو ويندو آهي ۽ جديد ميڪيڪل، اليڪٽرانڪ ۽ آپٽيڪل گيجنگ سسٽم کي نصب ڪرڻ لاءِ بنياد طور استعمال ڪيو ويندو آهي.

گرينائيٽ جي مٿاڇري واري پليٽ جون ڪجھ منفرد خاصيتون:

سختي ۾ هڪجهڙائي؛

لوڊ حالتن ۾ صحيح؛

وائبريشن جاذب؛

صاف ڪرڻ ۾ آسان؛

لپيٽڻ جي مزاحمتي؛

گھٽ پورسيٽي؛

غير ڇڪڻ وارو؛

غير مقناطيسي

گرينائيٽ مٿاڇري پليٽ جا فائدا

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.

اي ميل موڪليو

واٽس ايپ

اسڪائپ

انگريزي

جرمني

فرانسي

پرتگالي

اندلسي

جاپاني

ڪورين

عربي

آئرستاني

يوناني

ترڪي

اطالوي

ڊينش ٻولي

رومانوي

انڊونيشي

چيڪ ٻولي

سويڊني

پالش

بسڪاني

قيطلوني

ايسپرانتو

هندي

لائو

الباني

امهاري

آرمينيائي

آذربائيجاني

بيلاروسي

Pبنگالي

بوسنيائي

بلغاريائي

سيبوانو

چيچيوا

ڪارسيڪائي

ڪروشيائي

ڊچ ٻولي

ايستونائي

فلپائني

فني

فريسيني

گاليشين ٻولي

جيارجي

گجراتي

هيٽيائي

هوسا ٻولي

هوائينعبرانيهمنگي

هنگريآئس لينڊياِگبو

جاوانيڪنادي

قازق

خمير

ڪردي

ڪرغيز

لاطيني

لاتوين ٻولي

ليٿونيائي

لڪسمبو..

مقدوني

ملاگاسي

مالائي

مالايالم

مالٽي

مائوري

مراٺي

منگولي

برمي

نيپالي

نارويجي

پشتو

فارسي

پنجابي

سربيائي

سيسوٿو

سنهالا

سلوويڪي

1. سلوويني

1. صومالي
2. ساموئين
3. اسڪاٽس گيلڪ
4. شونا
5. سنڌي
6. سُنڊاني
7. سواهلي
8. تاجڪ
9. تاملي
10. تيلوگو ٻولي

ٿائي ٻولي

يوڪرينيائي

اردوAازبڪ2ويٽناميLويلشAهوسا

يدش

يوروبا

زولو

ڪينياروانڊا

تاتار

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.