Granīts ir magmatiska ieža veids, ko iegūst tā ārkārtējās izturības, blīvuma, ilgmūžības un izturības pret koroziju dēļ. Taču granīts ir arī ļoti daudzpusīgs – tas nav paredzēts tikai kvadrātiem un taisnstūriem! Patiesībā mēs regulāri strādājam ar granīta komponentiem, kas tiek konstruēti dažādās formās, leņķos un līknēs, sasniedzot izcilus rezultātus.
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:
■ apstrādājams
■ precīzi plakana pēc griešanas un apdares
■ izturīgs pret rūsu
■ izturīgs
■ ilgstoša iedarbība
Granīta detaļas ir arī viegli tīrāmas. Veidojot individuālus dizainus, noteikti izvēlieties granītu tā izcilo priekšrocību dēļ.

STANDARTI / AUGSTAS NOLIETOŠANAS SLĀPES LIETOJUMI
ZHHIMG standarta virsmas plākšņu izstrādājumiem izmantotajam granītam ir augsts kvarca saturs, kas nodrošina lielāku izturību pret nodilumu un bojājumiem. Mūsu Superior Black krāsām ir zema ūdens absorbcijas spēja, samazinot precīzijas mērinstrumentu rūsēšanas iespējamību, tos uzklājot uz plāksnēm. ZHHIMG piedāvātās granīta krāsas rada mazāku atspīdumu, kas nozīmē mazāku acu nogurumu personām, kuras lieto plāksnes. Mēs esam izvēlējušies granīta veidus, ņemot vērā termisko izplešanos, cenšoties šo aspektu saglabāt minimālu.

CUSTOM APPLICATIONS
Ja jūsu pielietojumam ir nepieciešama plāksne ar pielāgotām formām, vītņotiem ieliktņiem, rievām vai citiem apstrādes veidiem, jums jāizvēlas tāds materiāls kā Black Jinan Black. Šis dabīgais materiāls piedāvā izcilu stingrību, lielisku vibrācijas slāpēšanu un uzlabotu apstrādājamību.

Ir svarīgi atzīmēt, ka krāsa vien neliecina par akmens fizikālajām īpašībām. Kopumā granīta krāsa ir tieši saistīta ar minerālu klātbūtni vai neesamību, kam var nebūt nekādas ietekmes uz īpašībām, kas veido labu virsmas plātņu materiālu. Ir rozā, pelēks un melns granīts, kas ir lieliski piemērots virsmas plātnēm, kā arī melns, pelēks un rozā granīts, kas ir pilnīgi nepiemērots precīziem pielietojumiem. Granīta kritiskajām īpašībām, kas attiecas uz tā izmantošanu kā virsmas plātņu materiālu, nav nekāda sakara ar krāsu, un tās ir šādas:
■ Stingrība (novirze slodzes ietekmē — norāda elastības modulis)
■ Cietība
■ Blīvums
■ Nodilumizturība
■ Stabilitāte
■ Porainība

Esam pārbaudījuši daudzus granīta materiālus un salīdzinājuši tos. Visbeidzot, mēs iegūstam rezultātu: Dzjinaņas melnais granīts ir labākais materiāls, ko jebkad esam zinājuši. Indijas melnais granīts un Dienvidāfrikas granīts ir līdzīgi Dzjinaņas melnajam granītam, taču to fizikālās īpašības ir sliktākas nekā Dzjinaņas melnajam granītam. ZHHIMG turpinās meklēt pasaulē vairāk granīta materiālu un salīdzināt to fizikālās īpašības.

Lai uzzinātu vairāk par jūsu projektam piemērotāko granītu, lūdzu, sazinieties ar mums.info@zhhimg.com.

Dažādi ražotāji izmanto dažādus standartus. Pasaulē ir daudz standartu.
DIN standarts, ASME B89.3.7-2013 vai federālā specifikācija GGG-P-463c (granīta virsmas plāksnes) un tā tālāk kā pamats to specifikācijām.

Un mēs varam izgatavot granīta precīzas pārbaudes plāksni atbilstoši jūsu prasībām. Laipni lūdzam sazināties ar mums, ja vēlaties uzzināt vairāk informācijas par citiem standartiem.

Līdzenumu var uzskatīt par visiem virsmas punktiem, kas atrodas divās paralēlās plaknēs — pamatplaknē un jumta plaknē. Attāluma mērījums starp plaknēm ir virsmas kopējais līdzenums. Šim līdzenuma mērījumam parasti ir pielaide un var būt ietverts pakāpes apzīmējums.

Piemēram, trīs standarta klašu plakanuma pielaides ir definētas federālajā specifikācijā, izmantojot šādu formulu:
■ Laboratorijas pakāpes AA = (40 + diagonāle kvadrātā/25) x 0,000001" (vienpusējs)
■ Pārbaudes pakāpe A = laboratorijas pakāpe AA x 2
■ Instrumentu telpas B klase = laboratorijas klase AA x 4.

Standarta izmēra virsmas plāksnēm mēs garantējam līdzenuma pielaides, kas pārsniedz šīs specifikācijas prasības. Papildus līdzenumam ASME B89.3.7-2013 un federālā specifikācija GGG-P-463c aplūko tādus tematus kā: atkārtotu mērījumu precizitāte, virsmas plākšņu granītu materiālu īpašības, virsmas apdare, atbalsta punktu atrašanās vieta, stingrība, pieņemamas pārbaudes metodes, vītņotu ieliktņu uzstādīšana utt.

ZHHIMG granīta virsmas plāksnes un granīta pārbaudes plāksnes atbilst vai pārsniedz visas šajā specifikācijā noteiktās prasības. Pašlaik nav noteiktas specifikācijas granīta leņķa plāksnēm, paralēlēm vai galvenajiem kvadrātiem.

Un citu standartu formulas varat atrast šeit.LEJUPIELĀDĒT.

Pirmkārt, ir svarīgi uzturēt plāksni tīru. Gaisā esošie abrazīvie putekļi parasti ir lielākais plāksnes nodiluma avots, jo tie mēdz iestrādāties sagatavēs un mērinstrumentu saskares virsmās. Otrkārt, pārklājiet plāksni, lai pasargātu to no putekļiem un bojājumiem. Nodiluma laiku var pagarināt, pārklājot plāksni, kad tā netiek lietota, periodiski pagriežot plāksni, lai viena zona netiktu pārmērīgi noslogota, un nomainot tērauda saskares paliktņus mērinstrumentos ar karbīda paliktņiem. Tāpat izvairieties likt uz plāksnes ēdienu vai bezalkoholiskos dzērienus. Ņemiet vērā, ka daudzi bezalkoholiskie dzērieni satur vai nu ogļskābi, vai fosforskābi, kas var izšķīdināt mīkstākos minerālus un atstāt nelielus iedobumus virsmā.

Tas ir atkarīgs no tā, kā šķīvis tiek izmantots. Ja iespējams, iesakām šķīvi notīrīt dienas (vai darba maiņas) sākumā un vēlreiz tās beigās. Ja šķīvis kļūst netīrs, īpaši ar eļļainiem vai lipīgiem šķidrumiem, tas, iespējams, ir jātīra nekavējoties.

Regulāri tīriet plāksni ar šķidru vai ZHHIMG bezūdens virsmas plākšņu tīrīšanas līdzekli. Tīrīšanas līdzekļu izvēle ir svarīga. Ja tiek izmantots gaistošs šķīdinātājs (acetons, lakas šķīdinātājs, spirts utt.), iztvaikošana atdzesēs virsmu un deformēs to. Šādā gadījumā pirms plāksnes lietošanas ir jāļauj tai normalizēties, pretējā gadījumā radīsies mērījumu kļūdas.

Laiks, kas nepieciešams šķīvja normalizēšanai, būs atkarīgs no šķīvja izmēra un atdzesēšanas daudzuma. Mazākiem šķīvjiem vajadzētu būt pietiekamai stundai. Lielākiem šķīvjiem var būt nepieciešamas divas stundas. Ja tiek izmantots tīrīšanas līdzeklis uz ūdens bāzes, notiks arī zināma iztvaikošanas atdzesēšana.

Plāksne arī saglabās ūdeni, un tas var izraisīt metāla detaļu rūsēšanu, nonākot saskarē ar virsmu. Daži tīrīšanas līdzekļi pēc nožūšanas atstāj lipīgas paliekas, kas piesaista gaisā esošos putekļus un faktiski palielina nodilumu, nevis to samazina.

Tas ir atkarīgs no plāksnes lietošanas un vides. Mēs iesakām jaunai plāksnei vai precīzai granīta piederumam veikt pilnīgu atkārtotu kalibrēšanu viena gada laikā pēc iegādes. Ja granīta virsmas plāksne tiks intensīvi lietota, ieteicams šo intervālu saīsināt līdz sešiem mēnešiem. Ikmēneša pārbaude, izmantojot elektronisko līmeņrādi vai līdzīgu ierīci, lai noteiktu atkārtotu mērījumu kļūdas, parādīs visus veidojošos nodiluma plankumus, un tā aizņem tikai dažas minūtes. Pēc pirmās atkārtotās kalibrēšanas rezultātu noteikšanas kalibrēšanas intervālu var pagarināt vai saīsināt, kā to atļauj vai pieprasa jūsu iekšējā kvalitātes sistēma.

Mēs varam piedāvāt pakalpojumus, kas palīdzēs jums pārbaudīt un kalibrēt jūsu granīta virsmas plāksni.

Kalibrēšanas atšķirībām ir vairāki iespējamie iemesli:

• Pirms kalibrēšanas virsma tika mazgāta ar karstu vai aukstu šķīdumu, un tai netika dots pietiekami daudz laika normalizēties.
• Plāksne nav pareizi atbalstīta
• Temperatūras izmaiņas
• Melnraksti
• Tieši saules stari vai cits starojošs siltums uz plāksnes virsmas. Pārliecinieties, ka virsmas nesilda apgaismojums.
• Vertikālā temperatūras gradienta svārstības starp ziemu un vasaru (ja iespējams, zināt vertikālā gradienta temperatūru kalibrēšanas laikā).
• Pēc piegādes plāksnei netika dots pietiekami daudz laika, lai normalizētos
• Nepareiza pārbaudes iekārtu lietošana vai nekalibrētu iekārtu lietošana
• Virsmas izmaiņas nodiluma rezultātā

Cik daudz veidu caurumu ir precīzā granītā?

Spraugas uz precīzijas granīta komponentiem

Daudzās rūpnīcās, pārbaudes telpās un laboratorijās precīzas mērīšanas veikšanai tiek izmantotas precīzas granīta virsmas plāksnes. Tā kā katrs lineārais mērījums ir atkarīgs no precīzas atskaites virsmas, no kuras tiek ņemti galīgie izmēri, virsmas plāksnes nodrošina labāko atskaites plakni darba pārbaudei un izkārtojumam pirms apstrādes. Tās ir arī ideāli piemērotas augstuma mērījumu veikšanai un mērvirsmu mērīšanai. Turklāt augsta līdzenuma pakāpe, stabilitāte, kopējā kvalitāte un meistarība padara tās par labu izvēli sarežģītu mehānisku, elektronisku un optisku mērīšanas sistēmu uzstādīšanai. Jebkuram no šiem mērīšanas procesiem ir obligāti jākalibrē virsmas plāksnes.

Repeat Measurements and Flatness

Gan līdzenums, gan atkārtoti mērījumi ir ļoti svarīgi, lai nodrošinātu precīzu virsmu. Līdzenumu var uzskatīt par visiem virsmas punktiem, kas atrodas divās paralēlās plaknēs — pamatplaknē un jumta plaknē. Attāluma starp plaknēm mērījums ir virsmas kopējais līdzenums. Šim līdzenuma mērījumam parasti ir pielaide un var būt ietverts pakāpes apzīmējums.

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

DIN standarts, GB standarts, ASME standarts, JJS standarts... dažādas valstis ar atšķirīgu statusu...

Sīkāka informācija par standartu.

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.

Lai nodrošinātu, ka virsmas plāksne atbilst gan līdzenuma, gan atkārtotu mērījumu specifikācijām, granīta virsmas plākšņu ražotājiem par pamatu to specifikācijām jāizmanto federālā specifikācija GGG-P-463c. Šis standarts attiecas uz atkārtotu mērījumu precizitāti, granīta virsmas plāksnes materiāla īpašībām, virsmas apdari, atbalsta punktu atrašanās vietu, stingrību, pieņemamām pārbaudes metodēm un vītņoto ieliktņu uzstādīšanu.

Checking Plate Accuracy

Ievērojot dažas vienkāršas vadlīnijas, ieguldījums granīta virsmas plāksnē kalpos daudzus gadus. Atkarībā no plāksnes lietošanas veida, darbnīcas vides un nepieciešamās precizitātes, virsmas plāksnes precizitātes pārbaudes biežums atšķiras. Vispārējs noteikums ir tāds, ka jauna plāksne ir pilnībā jāpārkalibrē viena gada laikā pēc iegādes. Ja plāksne tiek izmantota bieži, ieteicams šo intervālu saīsināt līdz sešiem mēnešiem.

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

Dažos gadījumos virsmas plākšņu kalibrēšanas atšķiras. Dažreiz šīs atšķirības var izraisīt tādi faktori kā virsmas izmaiņas nodiluma rezultātā, nepareiza pārbaudes iekārtu lietošana vai nekalibrēta aprīkojuma lietošana. Tomēr divi visizplatītākie faktori ir temperatūra un atbalsts.

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

Ievērojot dažas vadlīnijas, tiks samazināts granīta virsmas plāksnes nodilums un galu galā pagarināts tās kalpošanas laiks.

Pirmkārt, ir svarīgi uzturēt plāksni tīru. Gaisā esošie abrazīvie putekļi parasti ir lielākais plāksnes nodiluma avots, jo tie mēdz iestrādāties sagatavēs un mērinstrumentu saskares virsmās.

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.

Periodiski pagrieziet plāksni, lai viena zona netiktu pārmērīgi noslogota. Tāpat ieteicams mērierīcēs tērauda kontakta paliktņus nomainīt pret karbīda paliktņiem.

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

Ja granīta virsmas plāksnei nepieciešama virsmas atjaunošana, apsveriet, vai šo pakalpojumu veikt uz vietas vai kalibrēšanas iekārtā. Vienmēr ir vēlams, lai plāksnes pārklāšana tiktu veikta rūpnīcā vai specializētā iekārtā. Tomēr, ja plāksne nav pārāk stipri nodilusi, parasti 0,001 collas robežās no nepieciešamās pielaides, to var atjaunot uz vietas. Ja plāksne ir nodilusi līdz vietai, kur tā pārsniedz pielaidi vairāk nekā 0,001 collu, vai ja tā ir stipri bedraina vai robaina, tad pirms pārklāšanas tā jānosūta uz rūpnīcu slīpēšanai.

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

Izvēloties kalibrēšanas un virsmas atjaunošanas tehniķi uz vietas, jāievēro īpaša piesardzība. Pieprasiet akreditāciju un pārliecinieties, vai tehniķa izmantotajam aprīkojumam ir izsekojama kalibrēšana. Svarīgs faktors ir arī pieredze, jo precīzas granīta slīpēšanas apgūšana prasa daudzus gadus.

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. Pirms kalibrēšanas virsma tika mazgāta ar karstu vai aukstu šķīdumu, un tai netika dots pietiekami daudz laika normalizēties.

2. Plāksne nav pareizi atbalstīta.

3. Temperatūras maiņa.

4. Melnraksti.

5. Tieši saules stari vai cits starojošs siltums uz plāksnes virsmas. Pārliecinieties, ka apgaismojums nesilda virsmu.

6. Vertikālā temperatūras gradienta atšķirības starp ziemu un vasaru. Ja iespējams, zināt vertikālā gradienta temperatūru kalibrēšanas laikā.

7. Pēc piegādes plāksnei nav dots pietiekami daudz laika, lai normalizētos.

8. Nepareiza pārbaudes iekārtu lietošana vai nekalibrētu iekārtu lietošana.

9. Virsmas izmaiņas nodiluma rezultātā.

Tech Tips

• Tā kā katrs lineārais mērījums ir atkarīgs no precīzas atskaites virsmas, no kuras tiek ņemti galīgie izmēri, virsmas plāksnes nodrošina labāko atskaites plakni darba pārbaudei un izkārtojumam pirms apstrādes.
• Controlling local area flatness to a tighter tolerance than overall flatness guarantees a gradual change in surface flatness profile, thereby minimizing local errors.
• Efektīvai pārbaudes programmai jāietver regulāras pārbaudes ar autokolimatoru, nodrošinot faktisko kopējā līdzenuma kalibrēšanu, ko var izsekot līdz Valsts inspekcijas iestādei.

Starp minerālu daļiņām, kas veido granītu, vairāk nekā 90% ir laukšpats un kvarcs, no kuriem visvairāk ir laukšpata. Laukšpats bieži ir balts, pelēks un miesassarkans, bet kvarcs pārsvarā ir bezkrāsains vai pelēcīgi balts, kas veido granīta pamatkrāsu. Laukšpats un kvarcs ir cieti minerāli, un tos ir grūti pārvietot ar tērauda nazi. Runājot par tumšajiem plankumiem granītā, galvenokārt melno vizlu, ir arī citi minerāli. Lai gan biotīts ir relatīvi mīksts, tā spēja pretoties stresam nav vāja, un tajā pašā laikā granītā to ir neliels daudzums, bieži vien mazāk nekā 10%. Šis ir materiāla stāvoklis, kurā granīts ir īpaši izturīgs.

Vēl viens iemesls, kāpēc granīts ir izturīgs, ir tas, ka tā minerālu daļiņas ir cieši saistītas viena ar otru un ir iestrādātas viena otrā. Poras bieži vien veido mazāk nekā 1% no kopējā ieža tilpuma. Tas dod granītam spēju izturēt spēcīgu spiedienu un mitrums tajā viegli neiesūcas.

Granīta detaļas ir izgatavotas no akmens bez rūsas, skābju un sārmu izturības, ar labu nodilumizturību un ilgu kalpošanas laiku, bez īpašas apkopes. Granīta precīzijas detaļas galvenokārt tiek izmantotas mašīnbūves instrumentu ražošanā. Tāpēc tās sauc par granīta precīzijas detaļām vai granīta detaļām. Granīta precīzijas detaļu īpašības būtībā ir tādas pašas kā granīta platformām. Ievads granīta precīzijas detaļu instrumentēšanā un mērīšanā: Precīza apstrāde un mikroapstrādes tehnoloģija ir svarīgi mašīnbūves nozares attīstības virzieni, un tie ir kļuvuši par svarīgu rādītāju augstā tehnoloģiju līmeņa mērīšanai. Progresīvo tehnoloģiju un aizsardzības nozares attīstība ir neatdalāma no precīzās apstrādes un mikroapstrādes tehnoloģijas. Granīta detaļas mērījumos var slīdēt vienmērīgi, bez stagnācijas. Darba virsmas mērījumi, vispārīgas skrambas neietekmē mērījumu precizitāti. Granīta detaļas ir jāprojektē un jāražo atbilstoši pieprasījuma puses prasībām.

Pielietojuma joma:

Kā mēs visi zinām, arvien vairāk mašīnu un iekārtu izvēlas precīzus granīta komponentus.

Granīta komponentus izmanto dinamiskai kustībai, lineārajiem motoriem, CMM, CNC, lāzeriekārtām...

Laipni lūdzam sazināties ar mums, lai iegūtu vairāk informācijas.

Granīta mērierīces un granīta mehāniskās sastāvdaļas ir izgatavotas no augstas kvalitātes Jinan melnā granīta. Pateicoties to augstajai precizitātei, ilgam kalpošanas laikam, labai stabilitātei un izturībai pret koroziju, tās arvien vairāk tiek izmantotas mūsdienu rūpniecības produktu pārbaudē un tādās zinātnes jomās kā mehāniskā aerokosmosa un zinātniskie pētījumi.

Priekšrocības

----Divreiz cietāks par čugunu；

---- Minimālas izmēru izmaiņas rodas temperatūras izmaiņu dēļ；

----Brīva no izgriešanas, tāpēc darbs netiek pārtraukts;

---- Bez urbumiem vai izvirzījumiem smalkgraudainas struktūras un nenozīmīgas lipīguma dēļ, kas nodrošina augstu līdzenuma pakāpi ilgā kalpošanas laikā un nerada bojājumus citām detaļām vai instrumentiem;

---- Bezproblēmu darbība lietošanai ar magnētiskiem materiāliem;

---- Ilgs kalpošanas laiks un bez rūsas, kā rezultātā zemas uzturēšanas izmaksas.

Precīzās granīta virsmas plāksnes ir precīzi pārlapotas līdz augstam līdzenuma standartam, lai sasniegtu precizitāti, un tās tiek izmantotas kā pamats sarežģītu mehānisko, elektronisko un optisko mērīšanas sistēmu uzstādīšanai.

Dažas no granīta virsmas plāksnes unikālajām īpašībām:

Vienveidība cietībā;

Precīzs slodzes apstākļos;

Vibrāciju absorbējošs;

Viegli tīrāms;

Izturīgs pret aptinumu;

Zema porainība;

Neabrazīvs;

Nemagnētisks

Granīta virsmas plāksnes priekšrocības

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.