The present invention relates to apparatus for positioning and clamping of
multiple number of work piece on CNC milling machine bed in shortest possible
10 time and more particularly to fixtures used to provide multiple positioning and
holding point on work piece during machining. It is a signal feature of the
invention that positioning and holding of work piece should be completed in
shortest possible time to reduce setup time and elimination of dialling operation
of work piece during setup. Dialling of work piece refer to making an edge of
15 work piece parallel to any one axis of CNC milling centre.
BACKGROUND OF THE INVENTION
20
The present invention relates to a fixture plate known as sub plate that is
attachable to the machine bed of conventional CNC milling equipment. The
present invention allows users of the CNC milling equipment to machine
multiple work pieces in a single setup. When machining a work piece on
25 conventional computer numerically controlled machines the work piece is
typically held in place by means of mechanical fastening methods with a
clamping member or vise. It is desirable to have the ability to mount as many
work pieces at a single time to reduce the amount of machine set-up and toolchange
time.
30
The present invention solves the problem of mounting multiple work
pieces on a CNC machine by providing a Sub plate which is easily secured to
the CNC machine bed with the Allen head bolt and T- Nut. The Sub plate is
designed to hold multiple work pieces for the machining operation, thus
35 significantly reducing set-up and tool-change time. One most time consuming
and significant operation during setup is, to make dialling face of milling fixture or
component, parallel to one of the axis of milling centre as reference axis. Sub
plate has the feature that eliminates this operation, thus reduces setup time
significantly.
40
Annexure‐II
SUMMARY OF PRESENT INVENTION
In 5 accordance with one aspect of present invention is to provide a
Sub plate that facilitates effective positioning of the work piece with respect to
one of the axis of CNC milling centre.
In accordance with second aspect of present invention is to provide a Sub
plate that facilitates effective and uniform holding pressure on work piece to be
10 fastened on CNC milling centre.
In accordance with another aspect of present invention is to provide a
lighter Sub plate.
In accordance with yet another aspect of present invention is to provide a
more rigid Sub plate for the holding of work piece.
15 In accordance with yet another aspect of present invention is to provide a
Sub plate that permits the positioning and holding of multiple work pieces at a
time.
In accordance with yet another aspect of present invention is to provide a
Sub plate that can be properly and effectively utilized to hold and firmly fixed the
20 work piece on CNC milling centre by lesser skilled individuals.
In accordance with yet another aspect of present invention is to provide a
Sub plate that can be properly and effectively fastened to the CNC milling centre
bed and should not demand any change in milling machine.
Briefly, the present invention is a sub plate for positioning, supporting and
25 holding the multiple work pieces undergoes machining operation on the CNC
milling centre. The basic objective for designing the sub plate is to eliminate the
operation of dialling of milling fixture. The size of the sub plate should be such
that it can easily accommodate the largest part and smallest part without need of
any extra tooling.
30
Material of the sub plate is selected based on some important attribute
such as bearing capacity of material, strength of material, hardness of material,
cost of material, and easy availability of material. Taking the entire factor into
consideration we have selected EN8 for the design of sub plate.
35
Annexure‐II
BRIEF DESCRIPTION OF THE DRAWINGS
The features and advantages of the present invention 5 n will become more apparent
and descriptive in the description when considered together with figures/flow
charts presented:
Fig. 1 is a top view of a Sub plate according to the present invention
10 Fig. 2 is an elevational view of the Sub plate
Fig. 3 is a Left side view of the Sub plate
15 DETAILED DESCRIPTION
Referring now to FIGS. 1, 2, 3, 4 & 5 the present invention is a Sub plate 7
adapted for use with a conventional CNC milling centre. The sub plate 7 is
mounted on the bed 8 of conventional CNC milling centre. The sub plate 7 is
20 constructed of a generally rectangular block 9 which in a preferred embodiment
is constructed of EN8. Material of the sub plate is selected based on some
important attribute such as bearing capacity of material, strength of material,
hardness of material, cost of material, and easy availability of material. The block
has a top surface 10 which is provided with a number of reamed 2 and threaded
25 3 through holes as shown in FIG. 1.
Sub plate is having a dialling face with the help of which it can be dialled
with respect to machine axis. Therefore we have incorporated a dialling face 5
with in the tolerance of 1μm for the entire length of sub plate. Such a high
30 tolerance is required due to the close tolerance of the component to be
manufactured on the machine. Overall size of the sub plate depends on the bed
size of the machine. Due to the difference in bed of various milling centre size of
the sub plate can be changed without departing form original sprit or scope of the
invention.
35
Sub plate is having the feature with the help of which milling fixture or
work piece can be clamped on sub plate without requiring any adjustment.
Sub plate also have feature with the help of which dialling of the milling fixture
40 during setup changeover can be eliminated. On the machine bed T-slots are
made at a certain distance. These T-slots are used to clamp the milling fixture on
the machine bed. Due to the fixed distance of T-slot, some time it becomes very
difficult to clamp small fixture on machine bed as clamping of such type of fixture
requires big clamp that lacks the rigidity and sometimes big clamps are not
Annexure‐II
available. To overcome this problem we have incorporate several M6 threaded
holes 3 at a pitch of 12 mm. availability of large no of such threaded hole makes
the sub plate as a continuous system of clamping. This enables the sub plate to
clamp 5 various size of fixture and eliminate the requirement of different size of
clamps as no. of clamps can be increase to hold the large fixture.
Sub plate has the feature that overcomes the problem of eliminating the dialling
10 operation. To overcome this problem we have incorporate several reamed
through hole 2 of 6H7 at a pitch of 36 mm. The positional tolerance of these
holes with respect to dialling face is 1μm. During the clamping of fixture, dowel
pins are used in these holes to position the fixture and eliminate dialling
operation.
15
For the clamping of sub plate on the machine bed 10 through holes 4 of
diameter 12.5 mm, counter bore to diameter 22 and 15 mm deep is provided on
sub plate. Standard M12 Allen head screws and T-nuts are used to clamp the
sub plate with machine bed. Since the whole sub plate is resting on the machine
20 bed therefore for easy cleaning of chips there should be some gap between
working area of sub plate and machine bed. In order to provide sufficient gap
between sub plate threaded and reamed hole area and machine bed, an milled
step 6 of 10 mm deep is created on the bottom side of sub plate to facilitate easy
removal of chips from the holes.
25
The clamping of sub plate with machine bed is a onetime operation.
Once the sub plate is fixed with the machine bed and dialled with the accuracy
of 1μm, no more dialling of milling fixture or work piece clamped on sub plate is
required. This is achieved because the dowel pins in reamed holes are used for
30 the positioning of dialling face of milling fixture or work piece clamped on sub
plate. With the present invention, multiple Working pieces may be secured to the
sub plate 7 for machining.

WE CLIAMS:-
Accordingly, the description of the present invention is to be considered as illustrative only and is for the purpose of teaching those skilled in the art of the best mode of carrying out the invention. The details may be varied substantially without departing from the spirit of the invention, and exclusive use of all modifications which are within the scope of the appended claims is reserved. We Claim

1. A sub plate for holding multiple work pieces in combination With a CNC milling centre having a bed with a support surface and having multiple T-slots at a certain fixed used to fix sub plate on the milling machine bed with Allen head bolt and T- Nut for positioning and holding of work piece on milling centre. The Sub plate comprising:

- A generally rectangular block having a top surface, a bottom surface, a forward Dialling edge

- The bottom surface of the sub plate resting on the top surface of the CNC milling centre bed with the forward edge parallel to the one of the axis of CNC milling centre

- The bottom surface of the sub plate having a milled step, reducing the contact area of the sub plate with the machine bed to enables the transfer the parallelism of bed to the top surface of the sub plate. This milled step serves another purpose of easy removal of chips after machining trapped in the holes of sub plate.

- The top surface of the sub plate provided with multiple threaded and reamed hole to facilitate positioning and holding of multiple work piece at a time.

2. The sub plate according to claim 1 further including multiple counter bore hole for fixing the sub plate on machine bed.

3. The sub plate of claim 1 wherein the top surface is the work piece holding surface and said surface are both substantially flat and disposed substantially parallel to the bottom surface. ,TagSPECI:As per Annexure-II