FIELD OF APPLICATION
The present invention relates to an automatic notch milling machine for carrying
out notch grooving on rolls. In particular the invention relates to a computer
numerical controller (CNC) based automatic notch milling machine with hardware
and software to achieve continuous notch or notch skipping in the roll passes,
These rolls are used in the rolling mill to produce thermo mechanically treatec
(TMT)bars.
BACKGROUND OF THE INVENTION
In the roll shop of rolling mills notch grooving operation is carried out on rolls
which are used to produce thermo mechanically treated bars. Conventiona
notch milling machines are being used for this purpose. The rolls, after notching
operation, are used in the finishing stands of the rolling mill to produce thermo
mechanically treated bars. For branding on the thermo mechanically treatec
bars, it is essential to skip notches on the roll passes. The space achievec
through notch skipping operation will be used to engrave the brand name on roll
passes through electrical discharge machining (EDM) technology.
The conventional notch milling machine used for notching operation is a manual
lathe. The known machine is similar to a lathe in which the work piece is held
between headstock faceplate and the tail stock center. There is a milling saddle
holding the tool parallel to the groove. It consists of a single induction motor to
control both spindle and tool axes through gear train arrangement. The feed
and saddle axes are manually controlled through lead screws and hand wheel.
Only continuous notching operation can be carried out on roll passes and
skipping or omitting notches is not possible. This is because of the design of the
machine as both the tool motion and roll motion are mechanically coupled and
are working on a mechanical transmission principle. The speed ratio for having
the desired pitch and angle are controlled by a set of change gear wheels. In
such a machine, the machine set up for every rib type or size is a long time
demanding operation in particular for gear handling and installation. Also the
known machine is limited by gear train arrangement and cannot machine ail
types of ribs.
SUMMARY OF THE INVENTION
The present invention overcomes the above-mentioned problems in a
conventional notch milling machine.
The main object of the present invention therefore, is to provide a computer
numerical controller based automatic notch milling machine which is capable of
producing continuous notches as well as for skipping notches as required.
Another object of the present invention is to achieve computer numerical
controller accuracy in the notch milling operation.
These and other objects are achieved by controlling all the four axes, spindle
axis, tool axis, feed axis and saddle axis through AC servo motors connected to a
computer numerical controller (CNC).
In the computer numerical controller based notch milling machine of the present
invention the gear train between the spindle and tool axes of the known machine
is dispensed with and these spindles are made independent. The feed and
saddle axes have been provided with ball screws for precise automatic operation.
Each of the four axes are fitted with FAGOR AC servo motors and drives by
which all the four axes can be controlled in a closed loop. FAGOR computer
numerical controller unit is provided to control the four axes. The computer
numerical controller allows continuous or automatic notch skipping operation
using the hardware and software configuration. The software can be through
universal 'G' code for precisely controlling the spindle, tool and feed axes.
The variation in the number of principles and notch angle can also be achieved
through the computer numerical controller and its software.
Thus the present invention provides an automatic notch milling machine for
carrying out notch grooving on rolls, characterized in that said machine
comprises: servo drives for controlling all four axes - spindle axis, tool axis, feed
axis, and saddle axis; and a computer numerical controller (CNC) is provided
connected to said servo drives for achieving closed loop control for performing
notch cutting on roll passes.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The present invention can now be described with the help of the attached
drawings in which:
Figure 1 is a block diagram of conventional notch milling machine.
Figure 2 shows a notching operation.
Figure 3 is a diagram of computer numerical controller based notch
milling machine of the present invention.
Figure 4 is a block diagram of hardware configuration
of the present invention.
DETAILED DESCRIPTION
Figure 1 shows in block diagram form a conventional notch milling machine. The
machine is having four axes, axis A represents the spindle axis, axis B represents
the tool axis, axis X represents the feed axis and axis Z represents the saddle
axis. The spindle and tool axis A, B are interconnected through gear train
arrangement. The tool axis B rotates at a proportion to spindle axis A
determined by the gear ratio selected by the operator. The X and Z axes are
both manually controlled by hand wheels.
Figure 2 diagrammatically shows the notch milling operation. The spindle axis A
and tool axis B both are rotary axes. The angle which the tool axis B makes with
the spindle axis A is determined by the gear ratio selected between them. As
both roll and tool are rotating at a fixed ratio, notches are formed on the roll
surface.
Figure 3 shows the computer numerical controller based notch milling machine of
the present invention. Here all the four axes (spindle axis A, tool axis B, feed
axis X and saddle axis Z) are controlled through ac servo motors connected to a
computer numerical controller. The fixed gear ratio between spindle and tool of
the known machine has been dispensed with and can be controlled through the
computer numerical controller using its software. In the present invention the
lead screws connected to the feed axis X and saddle axis Z of the manual
machine have been replaced by ball screws. The machine is controlled using the
computer numerical controller and the software used for programming the
computer numerical controller is through universal G-code.
Figure 4 shows in block diagram form the hardware configuration used in this
invention. The servo drives are connected to axes motors and computer
numerical controller is getting feedback from them. The spindle drive is having
external encoder and is directly connected to the spindle shaft to get direct
feedback to computer numerical controller. The computer numerical controller is
also connected to field devices such as limit switches, proximity sensor etc. The
system is controlled in a closed loop and performs automatic notching operation.
The notch milling operation of the present invention is suitable for rebar
production to machine straight and oblique notches, suitable nominal groove
diameter from 6 to 60 mm,
-8-
WE CLAIM
1. An automatic notch milling machine for carrying out notch grooving on
rolls, characterized in that said machine comprises:
- servo drives for controlling all four axes - spindle axis, tool axis,
feed axis, and saddle axis; and
- a computer numerical controller (CNC) is provided connected to
said servo drives for achieving closed loop control for performing
notch cutting on roll passes.
2. The machine as claimed in claim 1, wherein said computer numerical
controller comprises a FAGOR CNC unit and said four axes are fitted with
FAGOR AC servo motors.
3. The machine as claimed in claims 1 or 2, wherein said computer
numerical controller (CNC) unit is programmable for carrying out notch
milling operation for producing straight and oblique notches with nominal
groove diameter from 6 to 60 mm.
4. The machine as claimed in claim 1, wherein said computer numerical
controller (CNC) unit is programmable for carrying out skipped or
continuous notching operation automatically.
-9-
5. The machine as claimed in claim 4, wherein said computer numerical
controller (CNC) unit is programmable to achieve variation in the number
and notch angle.
6. The machine as claimed in claim 1, wherein said computer numerical
controller (CNC) unit is connected to field devices like limit switches and
proximity sensor, etc, for performing automatic notching operation with
a closed loop control.
7. Thermo-mechanically treated bars produced in a rolling mill wherein the
roll passes have grooves cut by an automatic notch milling machine as
claimed in claims 1 to 5.
8. An automatic notch milling machine for carrying out notch grooving on
rolls, said machine, substantially as herein described and illustrated in
the accompanying drawings.

An automatic notch milling machine for carrying out notch grooving on rolls, said
machine comprising:
-servo drives for controlling all four axes-spindle axis, total axis, feed axis, and
saddle axis; and
-a computer numerical controller (CNC) connected to said servo drives for
achieving closed loop control for performing notch cutting on roll passes.