2. AC machining originated out of research in
early 1960 sponsored by U.S Air Force.
Initial adaptive system are based on analog
type devices.
3. DEFINITION
The term ac denotes a control system that
measures certain o/p variables and uses
these to control speed and/or feed.
The typical measures of performance in
machining have been metal removal rate
and cost per volume of metal removal.
4. Adaptive control systems
It is a logical extension of the NC AND CNC.
Improvement of the cutting process by automatic online
determination of the feed and cutting speed.
Basically a feedback system in which the cutting speed and feed
automatically adopt themselves to the actual conditions of the
process.
The cutting speed and feed have to be varied in such a way as to
improve the performance level.
5. AC hardware components
Sensor mounted on the spindle to measure force.
Sensor to measure spindle motor current which is
used to provide indication of power consumption.
Control unit and display panel to operate the
system.
Interface hardware to connect AC system to existing
NC or CNC control unit .
10. ACO SYSTEM
Most of them are of the laboratory type used for
research and development(R&D).
Very costly.
Difficulties in developing comprehensive induces
or performance.
Sensor to measure that optimizes performance
index subject to various constraints..
Basically a sophisticated closed-loop control
system.
12. ACC SYSTEM
ACC system do not utilizes PI.
Objective of ACC is to increase MRR.
ACC are systems in which machining conditions such as spindle
speed or feed rate are maximized within the prescribed limits.
Most commonly used constraints in ACC systems are the cutting
force ,the machining power and the cutting torque.
13. ACC SYSTEM
-Simpler and lower cost
-Retrofitted with relative ease to existing machines
The most useful constraints in practical ACC Systems are-
1.The cutting force F
2.the cutting power P
3.The torque T
Principle of ACC-
-sense the constraints variables F,T & P
-adjust the cutting feeds and speed
14. X,Y,Z X,Y,Z
servo drive Machine Tool Spindle
speedNC
system
Tape
reader
Adaptive
control
Constr
aint
limit
Position&
Rate
commands
Torque
vibration
Rate feedback
Position feedback
Spindle speed command
Constraint
Limits tape
entry
ACC SYSTEM
Spindle load
Feedrate
modificati
on
15. WHERE TO USE AC
One of the principle reasons for using nc is that it
reduces the nonproductive time in a machining
operation.
Ac determines the proper speeds and feeds during
machining as a function of variables in such factors
as work material hardness, width or depth of cut,
air gaps in the part geometry and so on
16. The following characteristics can be used to identify
situations where ac can be beneficially applied
IN-PROCESS TIME
CONSUMES A
SIGNIFICANT
PORTION OF THE
MACHINING
CYCLE TIME
THERE ARE
SIGNIFICANT
SOURCES OF
VARIABILITY IN
JOB FOR WHICH
AC CAN
COMPENSATE
COST OF
OPERATING
MACHINING
TOOL IS HIGH
THE TYPICAL JOB
INVOLVES STEEL
& HIGH
STRENGTH
ALLOYS
17. SOURCES OF VARIABILITY
Variable geometry of cut
Variable work piece hardness
& variable machinability
Variable work piece rigidity
Tool wear
Air gaps during cutting
18. ADVANTAGES OF AC
Increased production rates
Increased tool life
Greater part protection
Less operator intervention
Easier part programming
20. CONCLUSION
For a machining operation ac is the best
method for controlling the process
It has been established that it was possible
to increase the metal removing rate by 35%
to 45% by using ac techniques
