Many spindles that are in use serve as high-precision components to your machine. Unfortunately, they are not always treated with the proper attention and care that they require. Spindles are often handled carelessly and sometimes forced to perform beyond the limitations of their design, abusing the equipment to the absolute breaking point. Properly caring for and maintaining your spindle will affect your machine’s longevity and service operation.
Spindles are highly complex systems that integrate dozens of pieces, all critical to your machine tool performance. Several of these parts require more care than others. For instance:
Rotating parts. Shafts, rotors, nuts, spacers, encoders, coolant unions, flingers, cutting tools, drawbars, chucks, and quills are all critical components. Tolerances for several of these rotating pieces are held within millionths of an inch, which suggests that even slight mishandling may cause a spindle to perform below the standards established when it was manufactured or repaired (and may even result in premature failure). Therefore, these parts should never be hammered, hit, pressed, pushed, pried, or dropped.
Even non-rotating parts should be inspected routinely and handled with care. These parts include the outside diameter of the spindle housing, housing faces, caps, flanges, and coolant ports. But, again, problems with any of these parts can cause problems down the road.
Main housing. Many other parts of the machine which the spindle serves are equally crucial in delivering optimum performance. For example, in a typical vertical machining center, the main housing is made to fit a spindle cartridge. This housing should be inspected regularly for signs of trouble. Another example, the inner diameter of the housing should be clean and show no signs of scoring or severe wear, and the faces should not exhibit any signs of damage, dings, or nicks. In addition, you should ensure that the main housing to the machine is appropriately aligned; otherwise, spindle problems attributed to misalignment could develop.
Once a spindle is up and running, proper maintenance can help achieve desired long-term usage and lengthen the time between failures.
Below are some tips for proper maintenance and care:
• Use only the correct and filtered oil for your particular spindle. Supplying the proper lubricant at the right time in the right amount is essential. Lubricants should always be high quality, properly specified and stored for the application, and kept clean and free from contaminants and moisture. Always ensure that neither too little nor too much lubricant is applied and that all lubricant transmission lines and containers are carefully inspected to rule out pre-existing contaminants.
• Always maintain the proper airflow with clean, dry air. (Ideally, desiccant drying systems for compressed air are best).
• Be sure to watch for any pressure drops or leaks in the air/oil lines.
• If the spindle has been idle for an extended period, you’ll want to break it in for a few minutes.
• Check for proper flow of the motor coolant and ensure it is clean.
• When using a chiller, never over-cool the coolant. Doing so may cause internal condensation within the spindle, contraction of internal materials that can change the preload on the spindle’s bearings and more than likely lead to premature failure of the spindle.
• The coolant for the cutting tool should be directed toward the cut as much as possible. This aids in reducing or eliminating potential backsplash to your spindle.
• Machined materials should be kept clean from building up around the spindle. Otherwise, over time, problems will follow.
• The working end of the spindle should be kept clean and dry. Sometimes machined material can get caught between the tool and the taper interface on the inner diameter of a typical milling spindle resulting in damage to the tool holder and spindle.
• Spare spindles should be stored in a clean, temperature-controlled environment.
• If you’re storing spindles for an extended period, you should rotate the spindles by hand every few weeks. In doing so, this aids in preventing grease & oil from sticking and possibly creating other problems.
Machine tool spindles perform as ideal solutions to rotate grinding wheels, cutting tools, or parts to be machined in applications ranging from grinding, milling, cutting, to drilling and boring to sawing. Proper care and maintenance will go a long way in preventing problems. As with any critical asset, proper care and maintenance can go a long way toward preventing problems and avoiding unscheduled downtime and lost productivity.