| Bases |
• The machine base is made of natural granite, which has dimensions of 991mm x 1206mm x 254mm (39" x 47.5" x 10") thick. The natural granite offers excellent thermal stability, while ensuring a high degree of vibration dampening.
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• On the granite base is a natural granite column, with dimensions of 736mm x 990mm x 305mm (29" x 39" x 12"). The column is used to support the vertical axis. Both the machine base granite and the column granite have mounting provisions for in process metrology equipment such as collimators or interferometers.
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• A fabricated steel frame supports the granite with a three point mounting arrangement for minimal influence on the machine accuracy.
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| • The granite and frame are supported by an active leveling isolation system, which is supported by a second, lower fabricated steel frame. This vibration isolation system consists of dual chamber air piston supports in four corners of the machine. Both corners at one end are tied together pneumatically to a single leveling valve, and the other two corners have individual valves. The dual chamber design allows vertical motins to be dampened by porting the air displacement between the chambers through a laminar flow restrictor device. |
| • A lower fabricated frame supports the vibration isolation system, upper machine tool enclosure, and the machine's NEMA-12 electrical and pneumatic cabinets. It also houses the hydrostatic oil supply system, and an air reserve tank. This tank acts as a buffer to suppress any fluctuations within the customer supplied air system. |
| • The machine sits on four leveling type rubber isolation supports. There is no need to mount the machine to the floor using bolts. |
| Slideways
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Horizontal Slide Assembly (Workholding Slide) |
• The X axis slide travel is 650mm (25.6"). |
• The slide is fitted with end of travel limit switches and linear glass scale encoder. |
• Driven with a brushless linear motor without contact to the moving carriage. |
• Slide speed is continuously variable up to a maximum of 1000mm/min. (40lpm). |
• Horizontal straightness: µm over the central 45 mm of travel. (40µ" over the central 18" of travel.) |
• Vertical straightness: 0.15µm per any 100mm zone over the central 457mm of travel. (6µ" per any 4" zone over its central 18" of travel.) |
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Vertical Slide Assembly (Spindle Slide) |
• The vertical slide, which supports the spindle, utilizes crossed roller bearings, providing smooth motion of te lisde and accurate positioning of the flycutting spindle. |
• The Z axis slide travel is 305mm (12"). The slide is fitted with limit switches at both ends of travel. |
• Fitted with a glass linear scale encoder, with feedback resolution of 100nm or less. |
• The slide is driven with a DC brushless servo motor through a planetary gearbox to a preloaded ball screw. |
• The drive system includes a rotary encoder and brake, for holding the axis steady. |
• The angular motion (pitch and yaw) of the slide is 12 arc seconds or less over the full travel. |
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| Spindles
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The machine utilizes Preciteh's SP151 air bearing spindle (all technical specifications specified at 5.44 bar (80 psig) supply pressure and measured at the spindle nose).
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| The spindle utlizes a hardened stainless steel shaft and bronze journal. A brushles DC drive motor integrally mounted to the spindle shaft allows the spindle to run up to 3,000 RPM. This motor design eliminates the need for a coupling between the spindle shaft and motor shaft. The spindle has an integral 1000 line decoder for closed loop velocity feedback. The spindle is provided with dynamic braking capability, which brings the spindle to a stop when required. |
| Axial stiffness |
210N/µm (1,200,000 lbs./") |
| Radial stiffness |
2140N/µm (800,000 lbs./") |
| Axial runout |
0.05µm (2µ") or less |
| Radial runout |
0.05µm (2µ") or less |
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| The spindle is mounted to a pivoting table, which provides easy adjustment of the heel angle. The heel angle adjustment provides up to 25 degree of tilt, for those special jobs where this is needed. The adjustment is simplified by only having to oosen two screws, and a handwheel with differential driving screw is provided for making the adjustment |
