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Room 3-470 77 Massachusetts Ave. Cambridge, MA 02139. Phone: (617) 253-1953 Fax: (617) 258-6427 http://pergatory.mit.edu/. The Mighty Spindle™. By: Roger Cortesi [email protected] http://pergatory.mit.edu/rcortesi/. Precision Engineering Research Group - PowerPoint PPT Presentation
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Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
The Mighty Spindle™
Precision Engineering Research GroupMassachusetts Institute of Technology, Mechanical Engineering Department
Phone: (617) 253-1953Fax: (617) 258-6427
http://pergatory.mit.edu/
Room 3-47077 Massachusetts Ave.Cambridge, MA 02139
By: Roger Cortesi [email protected] http://pergatory.mit.edu/rcortesi/
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
The Mighty Spindle™
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
Mighty Spindle™ Design Goals
• Low Cost• High Stiffness• 10,000 to 15,000 RPM• Automatic Tool Changer Option• New Features
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
Mighty Spindle™ Parameters
• 1.5 to 2.2 kW• Max Speed of 15,000 RPM• Radial Stiffness at Nose of 87 N/micron• Critical Speed of 23,000 RPM
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
Mighty Spindle™ Components
GE/Fanuc Motor
Porous GraphiteAir Bushing
Spindle Sensor
Duplex Nose BearingsNo. 30 TaperTool Holder
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
Why A Air Bushing in the Tail?
• Thermally Forgiving: Allows thermal expansion of spindle shaft.
• No Additional Seal Needed: The air flow provides a positive pressure air seal.
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
The Tail Support Assembly
• The Bushing is replicated in place to ensure good shaft alignment.
• The Tail Assembly is Kinematically aligned to housing. Allowing it to be removed for service and replaced WITHOUT messing up the alignment.
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
Assembly Steps
Core AssemblyHousing andStator Assembly
Tail SupportAssembly
Drawbar
End Cap Nose Cap
Tool Holder
After the Core is inserted an Nose Cap screwed in the Tail Assembly (w/ Bushing Loose) is mated. The Bushing is pressurized and replicated in place. Ensuring good shaft alignment.
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
Tail Support
End CapTail SupportAssembly
Air Bushing
KinematicGrooves
O-Ring
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
Front Air Seal
Labyrinth Seal is integral to the Nose Cap and Shaft
Seal Air In
Nose Bearing
Air ExitSpindle Shaft
Tool Holder
Nose Cap
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
The Hot Swappable SpindleSmall High Speed SpindleHeavy Duty Low Speed Spindle
KinematicAlignment
Grooves
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
The Hot Swappable Spindle
• No need to recalibrate machine after swap• Kinematic interface is repeatable to sub microns
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
Cooling the Mighty Spindle
Helical Cooling Groove
Cooling Water In
Cooling Water Out
AluminumHousing
Jacket
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
Cooling the Mighty Spindle
• Small Cross Section Groove = Better Heat Transfer
• Coolant enters at tail to pre-warm it before Nose Bearing Section
• Volume Flow Rate of 3 Gal per Hour• No Closed Loop Chiller Needed• Faucet to Drain
Property of Roger Cortesi, MIT Precision Engineering Research Group. DO NOT COPY or TRANSMIT without written permission.
The Thermal Model
The Dominant Thermal resistance is:•The contact resistance between the motor/bearings and the housing•The convection resistance between the groove walls and coolant
To Dissipate 200 Watts of Heat:•Tap Water at 10 C •3 Gallons per Hour
