Part i - spindle facts

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The values are valid for spring-loaded lips which are well lubricated by a mineral oil, where adequate lubricant supply ensures that heat does not build up and where the pressure is the same on both sides of the seal (pressure differential = 0). If in doubt, e.g. when the circumferential speed of the sealing lip is relatively high and there is no experience available in house, it is advisable to consult the manufacturer. The values obtained from Figure 29 should be reduced if: - Radial shaft seals with a secondary rubbing lip are used - Lubrication is poor or grease lubrication is used, i.e. when there is little cooling of the sealing lip and poor heat transfer - The counterface does not meet the demands in respect of surface finish or running accuracy - There is a pressure differential across the seal To obtain higher circumferen-tial speeds, it is possible to use Waveseals lip instead of standard straight type edge. The differential between those two types is shown in Figure 30. The Waveseal design from CR represents one of the most important developments in radial shaft seals during the past 25 years. The sealing lip is pressed and its special form produces a relative movement of the sealing lip on the counterface, imparting hydrodynamic properties. CR Waveseals are suitable for both directions of rotation; they pump the lubricant back into the bearing arrangement and expel contaminants. The sinusoidal form of the sealing lip considerably extends the path on the counterface and at the same time reduces the specific surface pressure in the sealing lip/counterface contact. As a consequence, CR Waveseals produce up to 20% less friction and up to 30% lower temperatures than conventional seals. These advantages prevent the formation of deep tracks in the counterface and provide much longer service lives. Figure 29. Permissible speeds for spring-loaded seal lips where no pressure differential exists across seal in operation Conventional Waveseal Figure 30. - 29 -
Table 4. Comparison of Contact Seals to Non-Contact Seals The table below shows the most important advantages of Non-Contact Seals compared with lip seals. Criteria Lip seal Non-Contact Seal Wear by friction none Power loss by friction none --> savings of energy --> may lead to smaller driving units Temperature increase yes none Speed limit depending on material none Live limited by wear unlimited Lubrication required at the sealing location no lubrication required for the seal Mating parts Hardening and grinding required for the shaft at higher speeds to reduce wear Temperature range Space requirement Field of applications limited due to material (plastic or rubber) Hardening and grinding not necessary from very low to very high - 40° C - 140° C (plastic material) - 40° F - 340° F (metallic material steel + aluminium) small formerly large - customer designed labyrinth seals; Grease lubrication Grease lubrication Oil lubrication Oil lubrication if oil level below sealing diameter Oil mist lubrication water - limited, as water may increase the friction at sealing location fine and coarse granular contamination not possible, as this environment causes rapid wear of the lips water - with the use of rust proof materials and level below sealing diameter fine and coarse granular contamination can be sealed reliably if applied to horizontal shaft. Because of the friction, contacting seals will raise the temperature of the system and therefore cannot be considered for the majority of machine tool <strong>spindle</strong>s. Thus, in general, contacting seals are used only where low speeds are involved dN value below 200.000 - 30 -
Page 2 and 3: PART I - SPINDLE FACTS 1. Introduct
Page 4 and 5: 2. Precision Spindle Design 2.1 Lis
Page 6 and 7: otate up to the maximum speed, and
Page 8 and 9: Bearing Contact Angle Angular conta
Page 10 and 11: Back to Back Configuration The most
Page 12 and 13: Motor-Spindle with Tandem Bearing P
Page 14 and 15: Bearing Lubrication Methods Angular
Page 16 and 17: There are many oils available on th
Page 18 and 19: 2.5 Spindles with Integral Motors S
Page 20 and 21: Synchronous Spindle Motor : AC asyn
Page 22 and 23: The synchronous motor built in spin
Page 24 and 25: Torque: This is the most critical a
Page 26 and 27: 2.7 Spindle Cooling Systems Heat is
Page 28 and 29: 2.8 Seal Types High precision beari
Page 32 and 33: and the influence of higher tempera
Page 34 and 35: 2.9 Tool Retention System A high sp
Page 36 and 37: Assuming that equivalent force is a
Page 38 and 39: of tooling. This means that users m
Page 40 and 41: HSK-Clamping Unit / Design B • A
Page 42: 3. Conclusion and Future trends A h
Page 45 and 46: Dynomax’s dedication to new spind

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