About Macor Machinable Glass Ceramic

Macor machinable glass ceramic has the versatility of a high performance polymer, the machinability of a metal, and the performance of an advanced technical ceramic. It is a hybrid glass-ceramic and offers a unique combination of properties from both families of materials. Macor is an excellent electrical and thermal insulator, and offers good performance in high temperature, vacuum, and corrosive environments.
One of the main advantages of Macor is that it can be machined with conventional metalworking tools. This allows for significantly faster turnarounds and substantially lower production costs when compared with other technical ceramics, making it an excellent material for both prototyping and medium-volume production runs.

Once cast into slab form, it is cut into smaller blocks and machined into into bars, tubes, disks or other custom designs with very tight tolerances. We can supply Macor slabs, blocks, bars, rods, plates, etc. or custom machined components from our facility that has been optimized for processing ceramics with very tight tolerances.

Maximum Macor Size: Macor is produced exclusively by Corning and is cast into large slabs approximately 12.5″ x 12.5″ x 2.125″ (317 x 317 x 54mm) unground.

Macor Info Sheet (PDF)

Macor Applications

Macor machinable glass ceramic was originally designed for NASA’s space shuttle to prevent thermal transfer from the exterior to the inside of the vehicle.  It was used in the window frames of the space shuttle because of its electrical and heat insulating qualities; because of its radiation resistance and non-porosity (it has a porosity of zero); and because it emits no vapors (toxic or otherwise) of any kind, especially at the lower pressures that were found in spacecraft. Macor is an excelent material for high vacuum applications, such as electron microscopy, because when properly baked out, it cannot outgas at any achievable vacuum level.

  • Electronics/Semiconductors
    • Precision coil formers (high precision and dimensionally stable)
    • High voltage insulators (smooth surface finish and unaffected by arcing)
  • Laser Applications
    • Spacers, cavities and reflectors in laser assemblies (precision finish and heat resistant)
  • High Vacuum Applications
    • Thermal breaks in high temperature processing equipment.
    • Coil supports and vacuum feed-throughs (vacuum stable and hermetically sealable)
  • Aerospace/Space Industry
    • Retaining rings on hinges, windows and doors of NASA’s Space Shuttle
    • Supports and components in several satellite borne systems (thermally and electronically insulating)
  • Nuclear Industry
    • Fixtures and reference blocks in power generation units (dimensionally unaffected by irradiation)

Macor Machinable Glass Ceramic Properties

Macor possesses excellent compressive strength, high thermal insulating value, radiation immunity, and excellent dielectrical strength. Unlike plastics, whose temperature resistance and rigidity starts to fall off at as little at 150°C, Macor is non-ductile and is deformation resistant to 800°C (up to 1,000°C with no load or weight-bearing).  Macor is so thermally stable that it is cut into small blocks against which are measured deformations in materials in high temperature, radioactive conditions.

  • Very tight machining tolerances of up to 0.0005in (0.013mm).
  • Can be machined with normal metalworking tools
  • Macor can be thick or thin film metallized, brazed, epoxy and frit bonded
  • Won’t outgas in vacuum environment
  • Does not require firing after machining

Macor Mechanical Properties

  • Strong and rigid; unlike high temperature plastics, Macor will not creep or deform
  • Zero porosity
  • Can be polished to a smoothness of 0.5µin

Macor Thermal Properties

  • Unlike high temperature plastics, Macor will not creep or deform
  • Low thermal conductivity; useful high temperature insulator
  • Excellent dimensional stability in a variety of environments (heat, radiation, etc.)
  • Coefficient of thermal expansion readily matches most metals and sealing glasses.

Macor Electrical Properties

  • Electric insulator, especially at high temperatures
  • Excellent with high voltages and a broad spectrum of frequencies
  • Radiation resistant

Macor vs Alumina

Alumina is a very commonly used technical ceramic due to its versatile properties, however, because it is such a hard material extensive diamond grinding is often required making it costly to produce in small quantities. Macor Machinable Glass Ceramic is often a viable alternative that can allows for significantly reduced production costs. Factors to consider when choosing between Macor and Alumina:

  • Thermal Cycle
    • Macor is vulnerable to thermal shock – if you have rapid heat up and cool down cycles Macor may not be appropriate. Shapal may be a viable alternative.
  • Maximum Temperature:
    • Macor has a maximum use temperature of 1000C (unstressed) and 800C (stressed); Alumina does offer higher temperature capabilities.
  • Wear Resistance
    • The same feature that makes Macor machinable means that it has relatively poor wear resistance when compared with Alumina.
  • Cost
    • For smaller quantities Macor often offers significant price reductions than Alumina components.

Macor vs Shapal Hi-M Soft

Macor glass ceramic and Shapal Hi-M Soft (Aluminum Nitride) are often compared because they both are machinable ceramics. Factors to consider when choosing between Macor and Shapal:

  • Thermal Conductivity
    • Shapal Hi-M is a thermal conductor at 90 W/(m K), Macor is a thermal insulator with a thermal conductivity of 1.46 W/(m K)
  • Thermal Cycle
    • Macor is vulnerable to thermal shock – if the part has rapid heat up and cool down cycles Shapal may be a better alternative alternative.
  • Maximum Temperature
    • Shapal has a much higher maximum use temperature of 1900C (in an inert atmosphere); in air it can withstand 1000C while stressed.
  • Costs
    • Macor is a cheaper material that Shapal Hi-M Soft, if it can be used instead of Shapal the user will typically see significant cost reductions.

Macor Composition

Macor is a composite material made of fluorophlogopite (a type of Mica) in a borosilicate glass matrix (such as used in test tubes and Pyrex®) in a ratio of 45/55 respectively.  The randomized microcrystalline structure allows tools to excavate micron-sized portions without cracking and fracture, leading to very exacting tolerances.

  • 46% silica (SiO2)
  • 17% magnesium oxide (MgO)
  • 16% aluminium oxide (Al2O3)
  • 10% potassium (K2O)
  • 7% boron (B2O3)
  • 4% fluorine (F)

Factors using Macor

Macor is vulnerable to halogen acids such as HCl (hydrochloric acid), although not a flash failure or sudden deterioration.  Tests show a 2.52 gram sample (1cc) of Macor exposed to Hydrochloric Acid at a pH of 0.1 experienced a 100 mg loss, or 3.96% over 24 hours.  Exposed to Sodium Hydroxide at a pH of 13.2 it experienced a loss of 0.396% in six hours.  It is stable to 1000°C in air, and to 600°C in vacuum.  Beyond 600°C (in vacuum) fluorine evolution will occur manifesting as boron trifluoride or hydrofluoric acid.

The most commonly available size of Macor is 12.5″ x 12.5″ x 2.125″ (317 x 317 x 54mm).

Joining Macor

Macor can be connected and joined with a variety of methods.  If it is metalized (metal inks or sputtering) it can be soldered, or brazed to other pieces, or bound to metal pieces such as titanium in the image to the right. Epoxy provides a strong joint and sealing glass provides a hermetic seal.  Macor can even be lapped and bound with a convention mechanical connection. With its remarkably tight machining tolerances of up to 0.0005in (0.013mm), joining is a simple and straightforward task.  Its coefficient of thermal expansion readily matches most metals and sealing glasses.  With appropriate polishing it can have a surface finish of less than 20 μinches, or 0.5 μmeters.

Prototyping with Macor

Macor machinable glass ceramic is an incredibly versatile material that can quickly be made into very complex geometries.  Because of it’s excellent machinability, Macor allows for rapid ceramic prototyping with many different iterations able to me made in a short period of time.

Macor Machining Guide

Macor is one of the few ceramics that can be machines using regular metal working tools. While there is a learning curve to machining Macor, it is certainly achievable for someone with the correct skills and patience. The machining characteristics of Macor are very different from metals and plastics so we recommend you take some time to practice drilling, turning, and milling the Macor before you try to make your own component to understand how it behaves. Unlike plastics and metals, ceramics never plastically deform; this means that when machining Macor you must be very conscious of chipping. For more information on Machining Macor Glass Ceramic, please visit our Macor Machining Guide.

Custom Macor Machining

Precision Ceramics USA is your Macor machinable glass ceramic specialist for your technical ceramic prototyping & manufacturing needs; we are always happy to use our many years of advanced ceramics experience to provide advice on materials, design, and application. If you would like to buy Macor plates, rods, bars, tubes, or custom machined Macor components please contact us and one of our experts will be happy to assist you.