10/24/2011. Chapter 3

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Mabel Craig
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1 Chapter 3 Exact alignment Availability to compensate wear Minimum friction Ease of assembly and economy of manufacture Freedom from restrain Prevention of chip and dirt accumulation Effective lubrication 1

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Advantage Simple to manufacture Self adjusting in case of wear Saddle is well supported Disadvantages Tendency to accumulate dirt and chips Need adjustment for clearance Poor in lubricant retention

3 Advantage Simple to manufacture Self adjusting in case of wear Saddle is well supported Disadvantages Tendency to accumulate dirt and chips Need adjustment for clearance Poor in lubricant retention Use High supporting force on long slideway Bigger m/c tool with high force Two types surrounding and surrounded Symmetrical if load is evenly distributed Usually combined with flat slideway for better guidance and load bearing 3

small lathe Planer machine Advantages Require small space Simple clearance adjustment Can stand vertical upward force

4 Advantages Self adjusting capability Surrounded vee prevents dirt accumulation Easy traverse and accurate guiding Disadvantages Surrounded type cannot retain lubricant Surrounded type weakens the saddle Wears rapidly Use Medium and small lathe Planer machine Advantages Require small space Simple clearance adjustment Can stand vertical upward force Disadvantage Relatively costly to manufacture Poor retention of lubricant Use Cross slides in lathe Milling machine tables Saddles and knees 4

to adjust Use Column drilling machine Over-arm of milling machine

5 Theoretically fully constrained slideway Easy to manufacture Disadvantages Low rigidity as fixed at two ends Clearance is difficult to adjust Use Column drilling machine Over-arm of milling machine Tailstock sleeve Flat slideways Adjustable stripe Laterally arranged screws Taper stripe 5

6 Vee slideways Dovetail Slideways Adjustable screws 6

7 Taper stripe Wedge stripe 7

Cylindrical slideways Selection of Materials depends on: wear resistance strength, specially bearing and bending strength, damping capacity heat capacity

8 Cylindrical slideways Selection of Materials depends on: wear resistance strength, specially bearing and bending strength, damping capacity heat capacity (It should not build up much heat.), environmentally neutral (It must stand hostile environment like new coolant, lubricant etc.) the cost of production 8

9 Gray cast iron is the most commonly used material for slideways. Nickel and chromium is added to increase the wear resistance and the bending strength The surface hardness can be increased by flame or induction hardening. Hardness attained is RC for ordinary gray cost iron and RC in nodular cast iron. Hardness upto RC can be attained by Hardened steel Laminated plastics strips backed by cost iron or steel pieces can be used. Advantages : uniform pressure less seizure reduced friction reduction of wear easy to fabricate lower cost 9

10 Disadvantages: lower strength and hardness, usually designed for pressure l0 kg/cm2 tendency to-swell when they absorb oil. poor thermal conductivity, resulting in thermal distortion. low speed range, v< 40m/min for satisfactory running. Wear is caused by factors such as: the properties of the material of the mating parts the surface roughness of the mating parts the pressure on the slideways the sliding velocity the total working life the dirt and chip accumulation on the slideways. 10

11 Any shape of slideways can be hydrostatically lubricated. 11

12 High load capacity and high rigidity are independent of the sliding velocity. There is no stick slip, because there is no metal to metal contact. Little wear of the sliding elements and thus longer life. Oil forces dust and chips out of the bearing area. Oil leakage also facilitates heat dissipation. Compressed air is passed through a filter and a pressure regulating valve. It then enters the pocket at a pressure of 3-4 kg/cm2 The aperture diameter varies from 0.2 to 0.5 mm humidity in air is to be reduced to a minimum value 12

13 ADVANTAGES: low friction, coefficient of friction is approximately for ground steel slideways and for scrapped cast iron slideways. Less stick slip effect. highly accurate movement. Uniform slow motion is possible less wear and considerably long service life operation without external lubrication. 13

14 DRAWBACKS : The cost of a such slideway system is high, because it is highly finished and hardened. Because the contact is at a point or along a line, the waviness of the surface impairs accuracy of motion. The rolling elements (balls, rollers etc.) lags behind the sliding member (Fig.3.28). Hence recirculation of the rolling elements is a must, if the travelling distance is long 14

BEARING AND TYPES OF BEARING

BEARING AND TYPES OF BEARING In this article, you will learn about bearing and types of bearing. Generally, all types of machinery are provided with supports for rotating shafts, the supporting device