Machine tool slides as shown in the picture below have metal to metal bearing su
ID: 1843628 • Letter: M
Question
Machine tool slides as shown in the picture below have metal to metal bearing surfaces with oil film lubricant. When machine operation requires frictionless movement, hydrostatic bearings are often used instead. Hydrostatic bearings are simply pads fed with pressurized fludi that ride along the precision surfaces of the slide. The pads are designed to provide the greatest stiffness to loads applied. The pads are placed so that they oppose each other so slide clearances remain stable. Use fluid mechanics to determine which of the two designs in the picture is most effective in supporting the normal load.
Bearing Design 1 feeds the fluid to the center of the bearing pad. Bearing Design 2 feeds the fluid to the grooves along the edges of the bearing pad. Assume the depth of the pads is large to the problem can be treated as 2 dimensional. The bearing supports a normal load of 5000-N/25mm of length with the following dimensions: h=W/5000 <-- Clearance between pad and rail w1=W/20 W=100mm Fluid is Oil (Mobil DTE light) T=40C Find:
1) an expression of the fluid pressure required to support the load.
2) calculate the pressure required for each design to support the load.
3) Find the flow rate of fluid required for each bearing design.
Stiffness= d(normal load)/dh
Bearing Pad Precision Bearing Pod Precision Rail Bearing Design Bearing Design 2Explanation / Answer
Design 2 is more effective because more uniform lubricant film distribution and stiffness is generated in design2 than design 1
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