Spindle
Accessories
Factors affecting the performance of spindle: Common Spindle Problems
The major factors affecting the performance of the spindle are as follows:
- Heat & Temperature: A factor that leads to spindle
problem is the temperature. All spindles are made of metal. Metals like
steel expands when heated and as such there is every chance of the
non-performance of a spindle when it is operated for a long time and
heat is generated. Under such circumstances, manufacturers should
explain what measures have been taken to protect the spindle from head
growth-which usually leads to Y and Z axis changes.
- Contaminants: The contaminants usually get inside the spindle
because of the easy opening or loosening of the the spindle seal. Under
such circumstances, the buyer must find out what design features are
taken by the machine tool manufacturer to keep the seal tight.
- Bearing failure: It is necessary to find out the design
features that protect the spindle. It has been found out that the most
common factor causing the failure of spindle is the bearing failure. The
bearing failure is due to contamination from chip damage, coolant
ingress, condensation etc.
- Tooling used: Another factor contributing to spindle
performance is the tooling used. Using worn tools, unbalanced tools or
long tools can affect the longevity of your spindle.
- Wrong Spindle for the Job: It so happens at times that a
spindle is used in an application for which it was never intended by the
manufacturer.
- RPM: All spindles are manufactured with a rated maximum
operating speed stamped on the spindle body. It is essential to know
that when rebuilding a spindle, if there is a deviation from that RPM,
there should be proper bearing preloads optimum to the application.
Running a spindle very slow or very fast will always result in poor
performance.
- Outside Influences: In many cases, the spindle is usually the
first component of a machine or machine tool to be blamed when things go
wrong. But it so happens that the actual cause of the trouble is
elsewhere.
- Drive Motors and Idlers: Bad bearings or out-of-balance will
transmit through the spindle into the machining process and in turn will
eventually damage the spindle.
- Tool holding equipment: All tool holding attachments to the
spindle should perfectly fit to the pilot surfaces of the spindle face.
Various problems like bad taper, bent or out-of-round, rusted, holding
devices can result in severe vibration or misalignment of the tool or
wheel to the work piece.
- Belt Tension: One of the severe cause of spindle failure is due to loosening of belts. The belt for the belt driven spindle should be just tight enough to avoid slippage. Excessive tightening creates problems of shaft deflection and makes the rear bearings out of alignment, thereby leading to poor performance, friction and vibration problems, heat and early failure.
Example of a spindle to remove contamination and control temperature
Spindle with coolant ring having adjustable nozzles
To remove the problem of contamination and to control the fluctuating temperature, some spindles are manufactured with a coolant ring having adjustable nozzles. This following picture shows a coolant ring having eight adjustable nozzles to remove chips and keep the temperature of the machine tool and the workpiece cool.
Coolant Through the Spindle (CTS)
This is important to give protection to expensive and custom tools. This type of spindle is recommended when machining at 12,000 rpm or more.
Conclusion
For any machining center, the spindle is the workhorse. It is very essential for all buyers to find out whether the manufacturer has taken spindle design seriously and given importance to quality components that will help increase the longevity and performance of your machining center's spindle.
