HIGH FEED RATES
A
CNC with look-ahead capability will try to protect the tool, work, and machine
from the effects of sharp changes in direction at high feed rates by slowing
the feed in advance of the turn, Fig. 2-1-30. This slowing down sacrifices
efficiency and may visibly affect the surface of the part. To keep the tool
path fast and effective, avoid slow-downs by making direction changes more
gradual. There are a variety of ways to machine with smoother motion such
as rounding corners, smoothing reversals, and machining in circles.
Another
approach to keeping the feed rate high does not involve direction changes, but
instead changes in the feed rate. Feed rate optimization may allow the
program to keep a higher average feed rate where the profile of the cut changes
often.
Fig. 2-1-30
In high-speed machining, the
feed rate should be kept as fast as possible. (Modern Machine Shop)
SUMMARY
·
HSM uses high spindle speeds, high
feed rates, and light depths of cut to increase productivity, reduce lead time,
reduce warping, increase part accuracy, and improve surface quality.
·
High-speed machining begins at
12,000 surface feet per minute (sf/min.) and may be as high as 18,000 sf/min.
and feed rates of 600 in/min. when machining aluminum.
·
The key factors that affect the
efficiency of a HSM system are the machine tool, the controller, spindle,
toolholder, cutting tool, and programming.
·
The CNC control, cutting tool,
machining center and other components must be designed with the goal of using
the higher spindle speed productivity.
·
In a toolholding system consisting
of the spindle, toolholder, and cutting tool, the toolholder is the most
important link because it has the greatest effect on the overall concentricity
and balance.
·
A balanced toolholder is critical
for producing high-quality surface finishes, extending spindle life, and
reducing or eliminating vibration that can affect the metal-removal process.
Copyright
2004, Industrial Press, Inc., New York, NY