Granitt er en type magmatisk bergart som utvinnes for sin ekstreme styrke, tetthet, holdbarhet og korrosjonsmotstand. Men granitt er også svært allsidig – den er ikke bare for firkanter og rektangler! Faktisk jobber vi jevnlig med granittkomponenter konstruert i former, vinkler og kurver i alle varianter – med utmerkede resultater.
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:
■ maskinbearbeidbar
■ helt flatt når det er kuttet og ferdig
■ rustbestandig
■ slitesterk
■ langvarig
Granittkomponenter er også enkle å rengjøre. Når du lager spesialtilpassede design, sørg for å velge granitt på grunn av dens overlegne fordeler.

STANDARDER / BRUKSOMRÅDER MED HØY SLITASJE
Granitten som ZHHIMG bruker til våre standard overflateplateprodukter har et høyt kvartsinnhold, noe som gir større motstand mot slitasje og skader. Våre Superior Black-farger har lav vannabsorpsjon, noe som minimerer muligheten for at presisjonsmålerne ruster når de festes på platene. Granittfargene som ZHHIMG tilbyr, resulterer i mindre gjenskinn, noe som betyr mindre øyebelastning for personer som bruker platene. Vi har valgt granitttypene våre med tanke på termisk ekspansjon for å holde dette aspektet minimalt.

CUSTOM APPLICATIONS
Når applikasjonen din krever en plate med tilpassede former, gjengede innlegg, spor eller annen maskinering, bør du velge et materiale som Black Jinan Black. Dette naturlige materialet gir overlegen stivhet, utmerket vibrasjonsdemping og forbedret maskinbearbeidbarhet.

Det er viktig å merke seg at farge alene ikke er en indikasjon på steinens fysiske egenskaper. Generelt sett er granittens farge direkte relatert til tilstedeværelsen eller fraværet av mineraler, som kanskje ikke har noen betydning for egenskapene som gjør et godt overflateplatemateriale. Det finnes rosa, grå og svarte granitter som er utmerkede for overflateplater, samt svarte, grå og rosa granitter som er fullstendig uegnet for presisjonsapplikasjoner. De kritiske egenskapene til granitt, når det gjelder bruken som overflateplatemateriale, har ingenting med farge å gjøre, og er som følger:
■ Stivhet (nedbøyning under belastning - indikert av elastisitetsmodul)
■ Hardhet
■ Tetthet
■ Slitasjemotstand
■ Stabilitet
■ Porøsitet

Vi har testet mange granittmaterialer og sammenlignet dem. Endelig har vi kommet frem til at Jinan svart granitt er det beste materialet vi noen gang har kjent til. Indisk svart granitt og sørafrikansk granitt ligner på Jinan svart granitt, men de fysiske egenskapene deres er dårligere enn Jinan svart granitt. ZHHIMG vil fortsette å lete etter flere granittmaterialer i verden og sammenligne deres fysiske egenskaper.

For å snakke mer om granitten som passer for prosjektet ditt, ta kontakt med ossinfo@zhhimg.com.

Ulike produsenter bruker forskjellige standarder. Det finnes mange standarder i verden.
DIN-standarden, ASME B89.3.7-2013 eller føderal spesifikasjon GGG-P-463c (granittoverflateplater) og så videre som grunnlag for spesifikasjonene deres.

Og vi kan produsere presisjonsinspeksjonsplater i granitt i henhold til dine krav. Ta gjerne kontakt med oss ​​hvis du vil vite mer informasjon om flere standarder.

Planhet kan betraktes som at alle punkter på overflaten befinner seg innenfor to parallelle plan, grunnplanet og takplanet. Målingen av avstanden mellom planene er overflatens totale planhet. Denne planhetsmålingen har vanligvis en toleranse og kan inkludere en karakterbetegnelse.

For eksempel er flathetstoleransene for tre standardkvaliteter definert i den føderale spesifikasjonen som bestemt av følgende formel:
■ Laboratoriekvalitet AA = (40 + diagonal i kvadrat/25) x 0,000001" (ensidig)
■ Inspeksjonsgrad A = Laboratoriegrad AA x 2
■ Verktøyrom karakter B = Laboratoriekarakter AA x 4.

For overflateplater i standard størrelse garanterer vi planhetstoleranser som overgår kravene i denne spesifikasjonen. I tillegg til planhet tar ASME B89.3.7-2013 og føderal spesifikasjon GGG-P-463c opp emner som: nøyaktighet av gjentatt måling, materialegenskaper til overflateplategranitter, overflatefinish, plassering av støttepunkter, stivhet, akseptable inspeksjonsmetoder, installasjon av gjengede innsatser osv.

ZHHIMG-overflateplater og inspeksjonsplater i granitt oppfyller eller overgår alle kravene som er angitt i denne spesifikasjonen. For øyeblikket finnes det ingen definerende spesifikasjon for vinkelplater, paralleller eller masterkvadrater i granitt.

Og du finner formlene for andre standarder iLAST NED.

For det første er det viktig å holde platen ren. Luftbårent slipemiddel er vanligvis den største kilden til slitasje på en plate, da det har en tendens til å feste seg i arbeidsstykker og kontaktflatene på måleinstrumenter. For det andre, dekk til platen for å beskytte den mot støv og skader. Levetiden kan forlenges ved å dekke til platen når den ikke er i bruk, ved å rotere platen med jevne mellomrom slik at et enkelt område ikke blir overdreven brukt, og ved å erstatte stålkontaktputer på måleinstrumenter med karbidputer. Unngå også å sette mat eller brus på platen. Merk at mange brus inneholder enten kullsyre eller fosforsyre, som kan løse opp de mykere mineralene og etterlate små groper i overflaten.

Dette avhenger av hvordan tallerkenen brukes. Hvis mulig anbefaler vi å rengjøre tallerkenen i begynnelsen av dagen (eller arbeidsskiftet) og igjen på slutten. Hvis tallerkenen blir skitten, spesielt med oljete eller klissete væsker, bør den sannsynligvis rengjøres umiddelbart.

Rengjør platen regelmessig med flytende eller vannfri ZHHIMG overflaterens. Valg av rengjøringsmidler er viktig. Hvis det brukes et flyktig løsemiddel (aceton, lakkfortynner, alkohol osv.), vil fordampningen avkjøle overflaten og forvrenge den. I dette tilfellet er det nødvendig å la platen normalisere seg før bruk, ellers vil det oppstå målefeil.

Hvor lang tid det tar for at platen skal normalisere seg, vil variere med størrelsen på platen og hvor mye den kjøles ned. En time bør være tilstrekkelig for mindre tallerkener. To timer kan være nødvendig for større tallerkener. Hvis det brukes et vannbasert rengjøringsmiddel, vil det også bli noe fordampningskjøling.

Platen vil også holde på vannet, og dette kan føre til rust på metalldeler som er i kontakt med overflaten. Noen rengjøringsmidler vil også etterlate et klebrig reststoff etter at de tørker, noe som vil tiltrekke seg svevet støv og faktisk øke slitasjen, snarere enn å redusere den.

Dette avhenger av platens bruk og miljø. Vi anbefaler at en ny plate eller presisjonstilbehør til granitt gjennomgår en fullstendig rekalibrering innen ett år etter kjøp. Hvis granittoverflateplaten vil bli utsatt for mye bruk, kan det være lurt å forkorte dette intervallet til seks måneder. Månedlig inspeksjon for gjentatte målefeil ved hjelp av et elektronisk vater eller lignende enhet vil vise eventuelle utviklende slitasjepunkter og tar bare noen få minutter å utføre. Etter at resultatene av den første rekalibreringen er bestemt, kan kalibreringsintervallet forlenges eller forkortes etter hva som er tillatt eller påkrevd av ditt interne kvalitetssystem.

Vi kan tilby tjenester som hjelper deg med å inspisere og kalibrere granittoverflateplaten din.

Det er flere mulige årsaker til variasjoner mellom kalibreringer:

• Overflaten ble vasket med en varm eller kald løsning før kalibrering, og fikk ikke tilstrekkelig tid til å normalisere seg
• Platen er feil støttet
• Temperaturendring
• Utkast
• Direkte sollys eller annen strålevarme på overflaten av platen. Sørg for at takbelysning ikke varmer opp overflaten.
• Variasjoner i den vertikale temperaturgradienten mellom vinter og sommer (Hvis det er mulig, kjenn den vertikale gradienttemperaturen når kalibreringen utføres.)
• Platen fikk ikke tilstrekkelig tid til å normalisere seg etter forsendelse
• Feil bruk av inspeksjonsutstyr eller bruk av ikke-kalibrert utstyr
• Overflateforandring som følge av slitasje

Hvor mange typer hull på presisjonsgranitt?

Spor på presisjonsgranittkomponenter

For mange fabrikker, inspeksjonsrom og laboratorier brukes presisjonsgranittoverflateplater som grunnlag for nøyaktig måling. Fordi hver lineær måling avhenger av en nøyaktig referanseflate som de endelige dimensjonene tas fra, gir overflateplater det beste referanseplanet for arbeidsinspeksjon og layout før maskinering. De er også ideelle grunnlag for å foreta høydemålinger og måle overflater. Videre gjør en høy grad av flathet, stabilitet, generell kvalitet og utførelse dem til et godt valg for montering av sofistikerte mekaniske, elektroniske og optiske målesystemer. For alle disse måleprosessene er det viktig å holde overflateplatene kalibrert.

Repeat Measurements and Flatness

Både planhet og gjentatte målinger er avgjørende for å sikre en presisjonsoverflate. Planhet kan betraktes som at alle punkter på overflaten er innenfor to parallelle plan, basisplanet og takplanet. Målingen av avstanden mellom planene er overflatens totale planhet. Denne planhetsmålingen har vanligvis en toleranse og kan inkludere en karakterbetegnelse.

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

DIN-standard, GB-standard, ASME-standard, JJS-standard ... forskjellige land med forskjellige standpunkter ...

Mer informasjon om standarden.

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.

For å sikre at en overflateplate oppfyller både spesifikasjonene for flathet og gjentatte målinger, bør produsenter av granittoverflateplater bruke den føderale spesifikasjonen GGG-P-463c som grunnlag for sine spesifikasjoner. Denne standarden omhandler nøyaktighet for gjentatte målinger, materialegenskaper til granittoverflateplater, overflatefinish, plassering av støttepunkter, stivhet, akseptable inspeksjonsmetoder og installasjon av gjengede innsatser.

Checking Plate Accuracy

Ved å følge noen få enkle retningslinjer, bør en investering i en granittoverflateplate vare i mange år. Avhengig av platenes bruk, verkstedmiljø og nødvendig nøyaktighet, varierer hyppigheten av kontroll av overflateplatens nøyaktighet. En generell tommelfingerregel er at en ny plate skal gjennomgå en fullstendig rekalibrering innen ett år etter kjøp. Hvis platen brukes ofte, anbefales det å forkorte dette intervallet til seks måneder.

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

I noen tilfeller er det variasjoner mellom kalibreringene av overflateplatene. Noen ganger kan faktorer som overflateforandringer som følge av slitasje, feil bruk av inspeksjonsutstyr eller bruk av ukalibrert utstyr forklare disse variasjonene. De to vanligste faktorene er imidlertid temperatur og støtte.

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

Å følge noen få retningslinjer vil redusere slitasje på en granittoverflateplate og til slutt forlenge levetiden.

Først er det viktig å holde platen ren. Luftbårent slipemiddel er vanligvis den største kilden til slitasje på en plate, ettersom det har en tendens til å sette seg fast i arbeidsstykker og kontaktflatene til målere.

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.

Roter platen med jevne mellomrom, slik at et enkelt område ikke blir overbelastet. Det anbefales også å bytte ut stålkontaktputer på måleinstrumenter med hardmetallputer.

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

Når en granittplate trenger ny overflatebehandling, bør du vurdere om du skal få denne tjenesten utført på stedet eller på kalibreringsanlegget. Det er alltid å foretrekke å få platen slipt på nytt på fabrikken eller et dedikert anlegg. Hvis platen imidlertid ikke er for slitt, vanligvis innenfor 0,001 tommer av den nødvendige toleransen, kan den bli slipt på nytt på stedet. Hvis en plate er slitt til det punktet at den er mer enn 0,001 tommer utenfor toleransen, eller hvis den er sterkt gropt eller hakket, bør den sendes til fabrikken for sliping før ny sliping.

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

Det bør utvises stor forsiktighet ved valg av en tekniker for kalibrering og overflatebehandling på stedet. Be om akkreditering og bekreft at utstyret teknikeren skal bruke har en sporbar kalibrering. Erfaring er også en viktig faktor, da det tar mange år å lære å slipe presisjonsgranitt riktig.

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. Overflaten ble vasket med en varm eller kald løsning før kalibrering og fikk ikke tilstrekkelig tid til å normalisere seg.

2. Platen er ikke støttet riktig.

3. Temperaturendring.

4. Utkast.

5. Direkte sollys eller annen strålevarme på overflaten av platen. Sørg for at takbelysning ikke varmer opp overflaten.

6. Variasjoner i den vertikale temperaturgradienten mellom vinter og sommer. Hvis det er mulig, kjenn den vertikale gradienttemperaturen når kalibreringen utføres.

7. Platen fikk ikke tilstrekkelig tid til å normalisere seg etter forsendelse.

8. Feil bruk av inspeksjonsutstyr eller bruk av ikke-kalibrert utstyr.

9. Overflateforandring som følge av slitasje.

Tech Tips

• Fordi hver lineær måling avhenger av en nøyaktig referanseflate som de endelige dimensjonene tas fra, gir overflateplater det beste referanseplanet for arbeidsinspeksjon og layout før maskinering.
• Controlling local area flatness to a tighter tolerance than overall flatness guarantees a gradual change in surface flatness profile, thereby minimizing local errors.
• Et effektivt inspeksjonsprogram bør inkludere regelmessige kontroller med en autokollimator, som gir faktisk kalibrering av den generelle flatheten som kan spores til nasjonal inspeksjonsmyndighet.

Blant mineralpartiklene som granitt består av, er mer enn 90 % feltspat og kvarts, hvorav feltspat er mest brukt. Feltspat er ofte hvit, grå og kjøttrød, og kvarts er for det meste fargeløs eller gråhvit, som utgjør granittens grunnfarge. Feltspat og kvarts er harde mineraler, og det er vanskelig å bevege dem med en stålkniv. Når det gjelder de mørke flekkene i granitten, hovedsakelig svart glimmer, finnes det også noen andre mineraler. Selv om biotitt er relativt myk, er dens evne til å motstå stress ikke svak, og samtidig finnes det en liten mengde av dem i granitt, ofte mindre enn 10 %. Dette er materialtilstanden der granitt er spesielt sterk.

En annen grunn til at granitt er sterk, er at mineralpartiklene er tett bundet til hverandre og innebygd i hverandre. Porene utgjør ofte mindre enn 1 % av bergartens totale volum. Dette gir granitten evnen til å motstå sterkt trykk og fukt trenger ikke lett inn.

Granittkomponenter er laget av stein uten rust, syre og alkalibestandighet, god slitestyrke og lang levetid, uten spesielt vedlikehold. Presisjonskomponenter av granitt brukes hovedsakelig i verktøyindustrien. Derfor kalles de presisjonskomponenter av granitt eller granittkomponenter. Egenskapene til presisjonskomponenter av granitt er i utgangspunktet de samme som for granittplattformer. Introduksjon til verktøy og måling av presisjonskomponenter av granitt: Presisjonsmaskinering og mikromaskineringsteknologi er viktige utviklingsretninger for maskinindustrien, og de har blitt en viktig indikator for å måle et høyteknologisk nivå. Utviklingen av banebrytende teknologi og forsvarsindustrien er uatskillelig fra presisjonsmaskinering og mikromaskineringsteknologi. Granittkomponenter kan skyves jevnt i målingen uten å stagnere. Ved måling av arbeidsflate påvirker ikke generelle riper målenøyaktigheten. Granittkomponenter må designes og produseres i henhold til kravene fra etterspørselssiden.

Søknadsfelt:

Som vi alle vet, velger flere og flere maskiner og utstyr presisjonskomponenter i granitt.

Granittkomponenter brukes til dynamisk bevegelse, lineære motorer, CMM, CNC, lasermaskiner...

Velkommen til å kontakte oss for mer informasjon.

Granittmåleinstrumenter og mekaniske komponenter i granitt er laget av Jinan Black-granitt av høy kvalitet. På grunn av høy presisjon, lang levetid, god stabilitet og korrosjonsmotstand, har de blitt mer og mer brukt i produktinspeksjon i moderne industri og vitenskapelige områder som mekanisk, luftfart og vitenskapelig forskning.

Fordeler

----Dobbelt så hardt som støpejern;

----Minimale dimensjonsendringer skyldes temperaturendringer;

----Fri for vridning, så det er ingen avbrudd i arbeidet;

----Fri for grader eller fremspring på grunn av den fine kornstrukturen og ubetydelig klebrighet, noe som sikrer høy grad av flathet over lang levetid og ikke forårsaker skade på andre deler eller instrumenter;

----Problemfri drift for bruk med magnetiske materialer;

----Lang levetid og rustfri, noe som resulterer i lave vedlikeholdskostnader.

Presisjonsgranittoverflateplatene er presisjonssleppet til høy standard for flathet for å oppnå nøyaktighet, og brukes som base for montering av sofistikerte mekaniske, elektroniske og optiske målesystemer.

Noen av de unike egenskapene til granittoverflateplaten:

Jevnhet i hardhet;

Nøyaktige forhold under belastning;

Vibrasjonsabsorberende;

Lett å rengjøre;

Innpakningsbestandig;

Lav porøsitet;

Ikke-slipende;

Ikke-magnetisk

Fordeler med granitt overflateplate

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.