Abrading – Precision device or process - or with condition responsive... – Condition responsive control for sandblasting
Reexamination Certificate
2002-09-09
2004-03-16
Hail, III, Joseph J. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
Condition responsive control for sandblasting
C451S005000, C451S008000, C451S009000, C451S075000, C451S086000, C451S091000, C451S102000, C408S180000, C408S187000
Reexamination Certificate
active
06705921
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and apparatuses for orienting a cutting tool. More particularly, the present invention relates to methods and apparatuses for controlling, reducing or eliminating the tapered edge that results when a workpiece is cut with a cutting tool.
BACKGROUND OF THE INVENTION
Cutting tools for cutting workpieces are generally known, with examples including drills and the like. One particular genre of cutting tools is non-contact cutting tools. Typically these tools emit a high energy stream towards a workpiece to cut the workpiece. Examples of such non-contact cutting tools include laser tools, torches such as an acetylene torch, plasma cutting tools, and high pressure waterjets.
Taking waterjet systems as exemplary of non-contact cutting tools, a typical waterjet system includes a waterjet head that is supplied with liquid at an ultra high pressure (UHP), for example 10,000 to 60,000 pounds per square inch (psi). The UHP liquid is discharged in an axial direction from the head in a high velocity stream against the workpiece. The liquid stream is used to cut through materials such as wood, metal, paper and foam. An abrasive particulate material can be added to the stream, and the liquid/abrasive stream can be used to cut through composites, metals and other dense materials. The cutting stream typically is concentrated in a small area that may be for example about 0.05 inch diameter, and has a high flow rate of for example about one to three gallons per minute (gpm). With commonly available equipment, the waterjet head and the cutting stream are maintained perpendicular to the top surface of the workpiece and are moved by a computer numerically controlled (CNC) system in order to cut through the workpiece along a cut line.
Although non-contact cutting tools such as waterjet systems have many advantages, an unfortunate result of making a cut with such a tool can be the taper of the cut edge. In most instances it would be desirable for the finished edge to have no taper and to be in a plane perpendicular to the workpiece top surface. However, the non-contact cutting stream, such as the water stream, may produce an edge that is inclined or tapered. The cutting stream may remove more material at the top than at the bottom of the cut, and in this case the resulting cut edge has what can be termed a positive taper. Referring particularly to waterjet systems by way of example, the amount of the taper is dependent on many variables including the speed at which the waterjet head is moved along the workpiece surface. At very slow speeds a relatively taper-free or a negatively tapered edge can be formed. Slower cutting speeds, however, increase production times and are disadvantageous.
A prior art waterjet cutting system designated as a whole as
10
is shown in FIG.
1
. The system
10
is used to form a cut
12
in a workpiece
14
, and includes a waterjet head assembly
16
. The waterjet head
16
includes a valve body
18
operated to open or closed positions by an actuator
20
controlled remotely by the presence or absence of pressurized air supplied to the actuator
20
through an air control conduit
22
. Ultra high pressure (UHP) liquid is supplied to the waterjet head
16
from a suitable UHP pump system
21
at pressures of between about 10,000 and 60,000 PSIG through a UHP liquid supply conduit
23
normally formed of stainless steel and having sufficient flexibility to permit movement of the waterjet head
16
around the surface of the workpiece
14
.
A valve nut
24
attaches a tube
26
to the bottom of the valve body
18
. When the valve in the valve body
18
is opened by the application of pressurized air within the actuator
20
, UHP liquid flows downward through the valve body
18
and the tube
26
to an outlet nozzle assembly
28
including a mixing chamber housing
30
and a nozzle
32
. The nozzle
32
is aligned with the longitudinal axis of the waterjet head
16
, and includes an axial discharge passage through which a concentrated UHP liquid stream is discharged at high pressure and high velocity.
For many applications, fine particles of an abrasive material such as garnet are added to the liquid stream. The mixing chamber member
30
receives particulate abrasive through a flexible rubber or neoprene abrasive supply line
34
. When UHP liquid flows through the mixing chamber member
30
, abrasive material is entranced in the liquid stream and a liquid/abrasive stream having increased cutting capability is discharged from the nozzle
32
.
The waterjet head
16
is supported, typically with its axis vertical and perpendicular to the top surface
38
of the workpiece
14
, by a clamp
36
or similar fixture. The clamp
36
is carried by a support arm
40
extending from a clamp plate
42
attached to a front plate
44
of a support member or lift
46
. The lift
46
is moved in three orthogonal directions by a three axis X-Y-Z drive
48
. Typically the drive
48
can move the waterjet head
16
in an X direction from side to side over the workpiece
14
and, separately or simultaneously, in a Y direction forward and rearward over the workpiece
14
. The drive
48
can also move the head
16
in a Z direction, vertically with respect to the workpiece. A computer numerical control (CNC) system
50
controls the drive
48
to perform a cutting operation upon the workpiece
14
. The head is moved in the Z direction to place the outlet of the nozzle
32
near the top workpiece surface
38
. Then the control system moves the head
16
in the X and/or Y directions to form the cut
12
. Typically the control system
50
is programmed to cut the workpiece in selected straight and/or curved lines and/or corners to fabricate finished parts having a desired shape.
Prior art waterjet systems of the type seen in
FIG. 1
are commercially available from sources including EASE Cutting Systems, 411 Ebenezer Road, Florence, S.C. 29501-0504. A further description of the prior art system
10
can be found at the title pages and pages 2-4, 2-5, 2-7, 2-8, 2-12, 4-29, 4-30 and 2-24 through 6-26 of ESAB Cutting Systems manual No. F14-135 dated May, 1999, filed herewith and incorporated herein by reference. A further description of a prior art waterjet head can also be found in U.S. Pat. No. 6,126,524 incorporated herein by reference.
When the cut
12
is formed in the workpiece
14
by the vertically disposed head
16
, the sides of the cut
12
are defined by inclined, sloped walls
12
A and
12
B. These sloped walls form a tapered cut
12
. The slope of the sides
12
A and
12
B of the tapered cut
12
can be as large as a several degrees. This taper can be undesirable, and in most operations a sidewall of the finished part that is perpendicular to the top surface
38
would be preferred. In some operations, a taper different from that of sides
12
A and
12
B would be preferred, for example to provide a beveled edge.
It would be desirable to control the taper of the cut edge so that taper could be reduced or eliminated or, alternatively, so that a controlled beveled edge of a desired angle could be produced. It has been recognized that positive taper can be reduced by slowing the cutting speed of the waterjet head. This practice, however, adds to manufacturing time and cost. In addition, expensive five-axis tilt control assembly systems are available for providing tilt and rotation in addition to X-Y-and Z movement that may offer some degree of taper control. Known five axis systems, however, are costly, complex, and bulky. These and other factors are deterrents to their use.
A proposed solution for cut edge bevel control is shown in U.S. Pat. No. 5,199,342 to Hediger (“the '342 patent”). The system disclosed in the '342 patent generally discloses a waterjet nozzle movably held by an X-Y drive system at a first point, and with the nozzle end pivotably held. X-Y movement at the first point causes the nozzle to be oriented at an angle to a workpiece. The X-Y drive system moves the first connection point in a first frame, wh
Greer Burns & Crain Ltd.
Hail III Joseph J.
Kolehmainen Philip M.
McDonald Shantese
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