Ultra-High Vacuum Environments
MACOR machinable Glass Ceramic is used as an insulator or coil support and for vacuum feed-throughs. In these applications, the conductive materials are supported by the MACOR MGC part and a compatible sealing glass is used to produce a vacuum-tight, hermetic seal.
Constant Vacuum Applications
MACOR MGC parts are found in spacers, headers and windows for microwave tube devices and as sample holders in field ion microscopes.
Over 200 distintly shaped MACOR MGC parts can be found on America's reusable Space Shuttle Orbiter. Retaining rings of MACOR MGC are used at all hinge points, windows and doors.
Also, large pieces of MACOR glass ceramic are used in a NASA spaceborne gamma radiation detector. For this application, frame corners are joined by a combination of machined (butt-lap) mechanical joints and a sealing glass.
Since MACOR MGC is not dimensionallt affected by irradiation, small cubes of the material are machined to a tolerance of one micron and used as a reference piece to measure dimensional change in other materials.
Welding equipment manufacturers are using MACOR MGC as a nozzle on the tips of oxyacetylene torches. The material's nonwetting characteristic means molten particles won't adhere to and decrease the effectiveness of the nozzle.
MACOR MGC is used as an electrode support and burner block in several industrial high heat, electrical cutting operations due to its low thermal conductivity and excellent electrical properties.
Producers of medical components are intrigued by MACOR MGC's inertness, precise machinability and dimensional stability.
The point is this: when you need the performance of a technical ceramic (high use temperature, electrical resistivity, zero porosity) and your application demands the ready fabrication of a complicated shape (quickly, precisely, privately), look at MACOR MGC. Il will lower costs and substantially reduce the time between design and actual use.
MACOR Machinable Glass Ceramic is a white, odorless, porcelain-like (in appearance) material composed of aproximately 55% fluorophlogopite mica and 45% borosilicate glass. It has no known toxic effects; however, the dust created in machining can be an irritant. This irritation can be avoided by good housekeeping and appropriate machining techniques. The material contains the folloing compounds:
||Approximate Weight %|
|Silicon - SiO2||46%|
|Magnesium - MgO||17%|
|Aluminium - Al2O3||
|Potassium - K2O||10%|
|Boron - B2O3||7%|
|Fluorine - F||4%|
Randomly oriented mica flakes in the microstructure of MACOR MGC are the key to its machinability.
Microstructure of MACOR MGC5000X magnification.
Key factors for successful machining are proper machining speeds and coolant.
MACOR Machinable Glass Ceramic can be machined with high speed steel tools, but carbide tools are recommended for longer wear.
Achieve the best results by using a water-soluble coolant, such as Cimstar 40 - Pink, especially formulated for cutting and grinding glass or ceramics.
No post firing is required after machining.
Diamond, silicon-carbide or aluminium-oxide grinding wheels can be used.
Start with loose 400-grift silicon carbide on a steel wheel. For the final polish, use cerium oxide or alumina on a polishing pad for glass or ceramics. A 0.5 µin.-AA finish can be achieved.
Use a carbide grit blade at a band speed of 100 fpm. An alternative is silicon carbide or diamond cut-off wheel.
|Cutting speed||30-50 sfm|
|Feed rate||.002-.005 ipr|
|Depth of cut||.150-.250 in.|
|Cutting speed||20-35 sfm|
|Chip load||.002 ipt|
|Depth of cut||.150-.200 in.|
|Drill size||Spindle Speed||Feed Rate|
|1/4 in.||300 rpm||.005 ipr|
Allow at least .050'' of extra material on the back side for breakout. This excess can be removed after drilling.
Make clearance holes one size larger than those recommended for metals. Chamfer both ends of the hole to reduce chipping. Run the cap in one direction only. (Turning the tap back and forth can cause chipping.) Continously flush with water or coolant to clear chips and dust from the tap.