 |
 |
Generating the necessary tolerance on any slideway system can be expensive and time consuming. The ways are either cast into the base and ground and/or are scraped, or the base is ground and ways bought “off-the-shelf” are bolted on. Grinding a base requires a significant investment in capital equipment
for a slideway grinder while scraping is particularly skilled and labor intensive and may still be necessary for preparing the base. Low friction coatings are added in many cases to the surface as insurance in case of a loss of hydrostatic pressure. The ways can still act as plain bearings to avoid damage.
Alloys such as Moglice have been developed that are low friction castable materials that require only a master to produce a finished surface. An example of its use is on the X — and Z-axes of the Bryant UL2 grinders [Bryant 1995] using roundway hydrostatic designs (Figure 15.15).
15.5.4 Round Hydrostatic Slideways
Round hydrostatic slideway designs have been available since the 1960s, but it was the use of replication methods to control film thickness that resulted in slides that could move accurately and smoothly at up to 46 m/min (1,800 in/min). Danobat [1991] has also used round hydrostatic bearings in the Z-axis internal grinding slideway of its 585 Universal grinder.