U.S. patent application number 11/620092 was filed with the patent office on 2007-07-12 for drill bit with cutter pockets formed by plunge edm.
This patent application is currently assigned to SMITH INTERNATIONAL, INC.. Invention is credited to Thomas W. Oldham.
Application Number | 20070157763 11/620092 |
Document ID | / |
Family ID | 38231505 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070157763 |
Kind Code |
A1 |
Oldham; Thomas W. |
July 12, 2007 |
DRILL BIT WITH CUTTER POCKETS FORMED BY PLUNGE EDM
Abstract
The disclosure provides an improved method for manufacturing a
drill bit. The method includes applying a hardfacing material to
the drill bit, forming a cutter pocket within the drill bit with
plunge EDM, and inserting a cutting element into the cutter
pocket.
Inventors: |
Oldham; Thomas W.; (The
Woodlands, TX) |
Correspondence
Address: |
OSHA, LIANG LLP / SMITH
1221 MCKINNEY STREET, SUITE 2800
HOUSTON
TX
77010
US
|
Assignee: |
SMITH INTERNATIONAL, INC.
Houston
TX
|
Family ID: |
38231505 |
Appl. No.: |
11/620092 |
Filed: |
January 5, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60757971 |
Jan 11, 2006 |
|
|
|
Current U.S.
Class: |
76/108.2 |
Current CPC
Class: |
E21B 10/567 20130101;
B23H 9/08 20130101; E21B 10/46 20130101; E21B 10/573 20130101; B23H
9/00 20130101 |
Class at
Publication: |
76/108.2 |
International
Class: |
B21K 5/04 20060101
B21K005/04 |
Claims
1. A method of manufacturing a drill bit, the method comprising:
applying a hardfacing to the drill bit having at least one blade;
forming a cutter pocket on the at least one blade with plunge EDM;
and inserting a cutting element into the cutter pocket.
2. The method of claim 1, further comprising machining the drill
bit from steel.
3. The method of claim 1, wherein the hardfacing is applied to the
drill bit by an automated system.
4. The method of claim 3, wherein the automated system is a CNC
machine.
5. The method of claim 1, wherein the plunge EDM is controlled by
an automated system.
6. The method of claim 5, wherein the automated system is a CNC
machine.
7. The method of claim 1, wherein the cutting element is comprised
of PDC.
8. The method of claim 1, wherein forming the cutter pocket with
plunge EDM comprises at least one plunge EDM pass.
9. The method of claim 1, wherein forming the cutter pocket with
plunge EDM comprises a plurality of plunge EDM passes.
10. The method of claim 1, wherein the plunge EDM comprises a
plurality of electrodes.
11. The method of claim 1, wherein the forming the cutter pocket
occurs after the applying the hardfacing.
12. A method of manufacturing a drill bit, the method comprising:
forming a bit body having at least one blade thereon; applying a
hardfacing to at least a portion of the bit body; forming a cutter
pocket on the at least one blade with plunge EDM; and inserting a
cutting element into the cutter pocket.
13. The method of claim 12, wherein forming the bit body comprises
at least one of machining, casting, and forging.
14. The method of claim 12, wherein the hardfacing is applied to
the drill bit by an automated system.
15. The method of claim 14, wherein the automated system is a CNC
machine.
16. The method of claim 13, wherein the plunge EDM is controlled by
an automated system.
17. The method of claim 16, wherein the automated system is a CNC
machine.
18. A drill bit manufactured with the method of claim 1.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority, pursuant to 35 U.S.C.
119(e), to U.S. Application Ser. No. 60/757,971 filed on Jan. 11,
2006, which is herein incorporated by reference in its
entirety.
BACKGROUND OF INVENTION
[0002] 1. Field of the Invention
[0003] The present disclosure generally relates to drill bits used
in the oil and gas industry. Specifically, the disclosure relates
to an improved method of manufacturing earth-boring bits for
drilling earth formations.
[0004] 2. Background Art
[0005] Drill bits are used in the oil and gas industry to drill
earth formations in the exploration for gas and oil. FIG. 1 shows a
drilling rig 107, which incorporates a drill bit 101. The drill bit
101 is connected to the bottom of a drill string 103 to drill a
wellbore 105. The drill string 103 is controlled by surface
equipment configured to rotate the drill string 103, apply downward
force to the drill bit 101 to penetrate the earth formation
(referred to as weight on bit ("WOB")), and supply drilling fluid
to the drill bit 101 by pumping the fluid through a bore of the
drill string 103. Because a variety of earth formations are
penetrated in the pursuit of oil and gas, several different types
and configurations of drill bits are used. These drill bits are
usually grouped into two different categories, shear bits and
roller cone bits.
[0006] Shear bits are drill bits that cut the earth's formation by
primarily scraping the earth formation when drilling. The shear bit
is fixed to the drill string, which is rotated so, as the drill
string rotates, the bit also rotates to cut into the earth
formation. The shear bit has a plurality of cutting elements
arranged on the body of the drill bit such that the cutting
elements scrape and shear the earth formation from the bottom and
sides of the wellbore as the drill bit is rotated. Shear bits do
not have any moving parts upon the bit itself, only the bit body
moves from the rotation of the drill string.
[0007] Roller cone bits, in contrast, are drill bits having cones
rotatably mounted onto journals. The roller cone bit typically has
a bit body with at least one journal, in which a cone is mounted
thereon and allowed to rotate. As the bit body is rotated by the
drill string, the cones rotatably contact the earth's formation. A
plurality of cutting elements are arranged on the roller cones to
crush and scrape the earth's formation as the bit is rotated. Even
though both types of drill bits are useful for drilling into earth
formations, only shear bits will be discussed from this point
forward.
[0008] Shear bits can be further grouped into two categories: steel
body bits and matrix body bits. Matrix body bits are constructed
using a powder metallurgy manufacturing process. A head mold of the
desired bit head shape is constructed and filled with matrix powder
and a binder. Next, the mold is placed in a furnace to allow the
binder to melt and infiltrate the matrix powder. As the binder
infiltrates the matrix powder, a solid metal casting is formed. The
two general types of matrix body bits consist of bits that
incorporate polycrystalline diamond compact ("PDC") cutting
elements, and bits that incorporate diamonds impregnated in the
matrix powder to shear the formation.
[0009] In contrast, steel body bits typically have their heads
machined from solid pieces of steel. Steel body bits are usually
machined with the entire outer geometry of the drill bit formed,
including the bit body, the bit blades, and even the cutter pockets
for cutting elements of the drill bit. Upon completion of the
machining, the remainder of the steel body bit is assembled with a
bit shank. Usually shear bits use PDC cutting elements or some
other type of wear resistant material disposed within the cutter
pockets to shear the earth formation. The focus of the remaining
discussion will be directed toward steel body bits.
[0010] FIG. 2 shows an example of a prior art steel body bit having
a plurality of cutting elements. The drill bit 200 includes a bit
body 201 and a plurality of blades 203 formed on the bit body 201.
The blades 203 are separated by channels or gaps 211 that enable
drilling fluid to flow between, both cleaning and cooling, the
blades 203 and cutting elements 205. Cutting elements 205 are held
in the blades 203 at predetermined angular orientations and radial
locations with a desired back rake angle against a formation to be
drilled. Nozzles 207 are typically formed in the drill bit body 201
and positioned in the gaps 211 so fluid can be pumped to discharge
drilling fluid in selected directions and at selected rates of flow
between the cutting blades 203 for lubricating and cooling the
drill bit 200, the blades 203, and the cutting elements 205. The
drilling fluid also cleans and removes the cuttings as the drill
bit rotates and penetrates the earth formation. The drill bit body
201 includes a plurality of cutter pockets 209 that are sized and
shaped to receive a corresponding plurality of cutting elements
205. The drill bit body 201 is machined with the cutter pockets 209
so the cutting elements 205 may be inserted and secured in the
pockets 209 using methods such as brazing, adhesive, or
interference fit.
[0011] When machining the steel body bit in the prior art, the
outer geometry is formed with the bit body, the bit blades, the
cutter pockets, and the gaps. Typically, a hardfacing material is
then manually applied, such as by arc or gas welding, to the
exterior surface of the steel body bit to protect the bit against
erosion and abrasion. The hardfacing material may be applied to the
entire outer geometry of the steel body bit, or may only be applied
to the parts of the drill bit that contact the earth formation
during drilling or that are impinged by the drilling fluid. The
hardfacing material is typically applied prior to the cutting
elements being inserted into the cutter pockets. Displacements or
coverings may be used to fill the cutter pockets as to protect the
cutter pockets during hardfacing. The hardfacing material usually
includes one or more metal carbides, which bond to the steel body
by a metal alloy ("binder alloy"). In effect, the carbide particles
are suspended in a matrix of metal, forming a layer on the surface
of the drill bit. The carbide particles give the hardfacing
material hardness and wear resistance, while the matrix metal
provides strength and fracture toughness to the hardfacing
material.
[0012] When the hardfacing the machined steel body bit, the
hardfacing material layer is typically applied with a small
diametrical clearance around the cutter pockets. The small
clearance is necessary to allow the cutting elements to be later
inserted and secured within the cutter pockets. The hardfacing
application process, though, is not very precise and the
diametrical clearance around the cutter pockets may result in a
significant gap between the cutting elements and the hardfacing
material. The gap is then large enough to allow erosion of the
braze material when securing the cutting element within the cutter
pockets and eventually allow erosion of the steel beneath the
hardfacing.
[0013] Further, close-fitting cutting elements usually only have
thin sections of steel therebetween. Hardfacing these thin sections
of steel is difficult because the sections may not have much
surface area for applying the hardfacing material. Hardfacing
large, simple geometry areas allows for the hardfacing material to
be uniformly applied with good quality bonding to the bit body. The
thin sections of steel have a more complicated geometry, which is
more difficult to apply a uniform hardfacing layer with good
quality bonding.
[0014] Furthermore, if displacements are used to protect the cutter
pockets when applying the hardfacing material, the displacements
may need to be broken out of the cutter pockets to then allow the
cutting elements to be inserted within the pockets. When removing
and breaking out the displacements, the hardfacing material may
actually chip and crack. Such chipping and cracking would lead to
further damage and reduced bit life when the steel body bit is used
for drilling earth formations.
[0015] Thus, it would be desirable to obtain a better method for
manufacturing drill bits to avoid such problems with current
methods.
SUMMARY OF INVENTION
[0016] In one aspect, embodiments of the present disclosure relate
to a method of manufacturing a drill bit that includes applying a
hardfacing to the drill bit, forming a cutter pocket on the at
least one blade with plunge EDM, and inserting a cutting element
into the cutter pocket.
[0017] In another aspect, embodiments of the present disclosure
relate to a method of manufacturing a drill bit that includes
forming a bit body having at least one blade thereon, applying a
hardfacing to at least a portion of the bit body, forming a cutter
pocket on the at least one blade with plunge EDM, and inserting a
cutting element into the cutter pocket
[0018] Other aspects and advantages of the invention will be
apparent from the following description and the appended
claims.
BRIEF DESCRIPTION OF DRAWINGS
[0019] FIG. 1 shows a prior art drilling rig.
[0020] FIG. 2 shows a prior art steel body bit.
[0021] FIG. 3 shows a prior art plunge electrical discharge
machining assembly.
[0022] FIG. 4 shows a flow chart illustrating a method of
manufacturing a drill bit in accordance with an embodiment of the
present disclosure.
DETAILED DESCRIPTION
[0023] In one aspect, the present disclosure provides an improved
method for manufacturing steel body bits. Specifically, the
embodiments of the present disclosure incorporate plunge electrical
discharge machining ("EDM") to form cutter pockets within a steel
body bit.
[0024] Plunge EDM, sometimes referred to as sinker EDM or ram EDM,
is a technique used to remove material from a workpiece, in which
the workpiece is made from an electrically conductive material,
such as metal. Plunge EDM removes material through erosive action
resulting from electrical discharges. The electrical discharges
occur when an electrical voltage is applied between the workpiece
and a cutting electrode, in which the two are submerged in a
dielectric fluid. The dielectric fluid is usually oil or de-ionized
water located in a work tank. The cutting electrode, usually formed
from graphite, is guided along a desired path very close to the
workpiece, but not touching the workpiece. When the cutting
electrode and the workpiece are in close proximity of each other
along the desired path, material is melted and vaporized from both
the workpiece and the electrode by the electrical discharges
occurring. This leaves a small amount of a resultant material on
the surfaces of the cutting electrode and the workpiece. The
resultant material may be removed by continuously washing the
dialectic fluid across the cutting electrode and the workpiece. The
final result from each electrical discharge is a small crater on
both the cutting electrode and the workpiece. Plunge EDM uses very
rapidly occurring electrical discharges to remove substantial
portions of material from the workpiece.
[0025] FIG. 3 shows an illustration of a basic plunge EDM assembly,
which includes an electrode 301 and a workpiece 303 submerged in
dielectric fluid 305. The electrode 301 is a blank-shape of a
cavity 309 to be formed in the workpiece 303. When the electrode
301 is in close proximity of the workpiece 303, electrical
discharges 307 occur, between the electrode 301 and the workpiece
303. The electrical discharges 307 remove material from the
workpiece 303 to form the cavity 309. The cavity 309 formed is a
negative shape of the electrode 301.
[0026] Generally, several electrodes may be used in conjunction
with one another to remove material from a workpiece during plunge
EDM to improve the process. A first electrode may be used in a
"rough pass" to form the general shape of the cavity. Then, further
electrodes may be used in subsequent passes to further define the
cavity. The subsequent passes may provide a better finish upon the
workpiece and/or may improve tolerances of the shaped surfaces
formed in the workpiece by removing additional material.
[0027] FIG. 4 shows a flow chart illustrating a method of
manufacturing a drill bit in accordance with an embodiment of the
present disclosure. As a first step 410, a drill bit is machined
from a solid piece of steel. The drill bit may be machined to
include an outer geometry of the drill bit, in addition to inner
hydraulic passageways of the drill bit. When machining the outer
geometry of the drill bit, the bit blades may be formed, but the
cutter pockets are not yet formed. In one embodiment, substantially
all of the outer geometry, excluding the cutter pockets, is formed
as a first step 410. After machining the drill bit, hardfacing
material is applied 420 to the drill bit. The hardfacing material
may be applied to the entire outer geometry of the drill bit, or
may be only applied to parts of the drill bit which may contact the
earth formation when drilling.
[0028] After applying the hardfacing material to the drill bit,
cutter pockets are formed 430 at selected locations on the drill
bit. The cutter pockets are formed 430 in the drill bit using
plunge EDM. In a plunge EDM process, an electrode in the presence
of a dielectric fluid and an electric voltage is used to form a
cutter pocket in the drill bit. Plunge EDM may be used to form
cutter pockets in a drill bit after hardfacing because plunge EDM
only requires the drill bit be electrically conductive. The
electrode may be graphite and may be machined in a desired shape of
the cutter pocket. Additionally, the plunge EDM process may be
controlled by an automated system, such as a computer numerical
control ("CNC") machine. Further, multiple passes may be used with
multiple electrodes to improve the plunge EDM process when forming
the cutter pockets. After the cutter pockets have been formed,
cutting elements may be inserted 440 into the cutter pockets of the
drill bit. Methods such as brazing, adhesion, or interference fit
may be used to secure the cutting elements within the cutter
pockets.
[0029] Alternatively, in another method of manufacturing a drill
bit in accordance with an embodiment of the present disclosure, as
a first step 410, at least a portion of a drill bit may be cast or
forged. For example, the drill bit may be cast in a mold with steel
such that the mold forms the outer geometry, including the bit
blades, of the drill bit. When forming the outer geometry of the
drill bit though, the cutter pockets are not yet formed. The cutter
pockets will be formed 430 with plunge EDM following applying
hardfacing material 420 to the drill bit. Those having ordinary
skill in the art will appreciate that combinations of these or
other methods of manufacturing a drill bit may be used without
departing from the scope of the present invention.
[0030] Those of ordinary skill in the art will appreciate that a
number of techniques may be used to apply the hardfacing material
upon a drill bit. For example, hardfacing material may be applied
manually to the drill bit by arc welding or gas welding. In such
instances, a skilled worker may be required to apply the hardfacing
material upon the drill bit.
[0031] In another technique, an automated system may be used to
apply the hardfacing material upon a drill bit. For example, a CNC
machine may use a laser to apply the hardfacing material upon the
drill bit. The outer geometry of the drill bit in the present
disclosure may be less complex as compared to prior art drill bits
because cutter pockets are not yet formed during hardfacing. The
use of an automated system could then be more feasible and enabled
with the present disclosure because not as many inputs may be
necessary for the automated system when used to apply hardfacing
material upon the less complex outer geometry drill bit. Though
certain techniques may be more advantageous than others for
applying the hardfacing material upon the drill bit, the specific
technique used to deposit the sealing metal is not a limitation on
the scope of the present invention. Also, those having ordinary
skill in the art will appreciate that combinations of these or
other hardfacing techniques may be used without departing from the
scope of the present invention.
[0032] Embodiments of the present disclosure may have one or more
of the following advantages. As mentioned above, when applying
hardfacing material to a drill bit in the present disclosure, the
drill bit will not yet have cutter pockets formed, allowing the
drill bit to have a less complex outer geometry during the
hardfacing process. A less complex outer geometry may allow for a
more consistent hardfacing layer be applied to the drill bit. For
example, a CNC machine may be used to apply hardfacing material to
the surface of the drill bit, allowing the depth of the hardfacing
material be controlled more precisely. If cutter pockets were
present, the machine may have to work around the cutter pockets,
which may add more factors and inputs to increase the difficulty of
hardfacing the drill bit. Similarly, a less complex outer geometry
of the drill bit may allow for a more time efficient hardfacing
layer be applied to the drill bit. The hardfacing process may not
have to work around the cutter pockets, which may decrease the time
necessary to apply hardfacing material to the drill bit.
[0033] Additionally, hardfacing of thin sections of steel between
close-fitting cutting elements is improved. Because the cutter
pockets are formed using plunge EDM after the hardfacing process,
this allows for a more even, uniform depth of hardfacing material
be applied to the drill bit. When the cutter pockets are then
formed into the drill bit, the thin sections of steel between the
close-fitting cutting elements on the drill bit will have the more
uniform hardfacing material applied. Otherwise, if the hardfacing
material was applied after the cutter pockets were formed,
hardfacing the thin sections of steel between the close-fitting
cutters may be more difficult because the sections may not have as
much area to apply the hardfacing material upon.
[0034] Further, the need for displacements to protect the cutter
pockets during hardfacing may be eliminated. Because the cutter
pockets are formed after hardfacing of the drill bit, no protection
may be needed for the cutter pockets when hardfacing. Therefore,
this may avoid chipping and cracking the hardfacing material of the
drill bit when the displacements are needed to be removed and
broken out from the cutter pockets.
[0035] Furthermore, the use of plunge EDM may improve the
tolerances of the cutter pockets formed. For example, plunge EDM
may be more precise for removing material and forming cutter
pockets than conventional methods, such as machining. This
precision is particularly enhanced with the use of multiple passes
of electrodes during the plunge EDM process. This improved
precision may allow the cutter pockets to have a more secure fit
with cutting elements.
[0036] In addition, heat is used when applying the hardfacing
material upon the drill bit. The use of heat may deform and warp
portions of the drill bit, including the cutter pockets on the
drill bit. Plunge EDM avoids using heat after the cutter pockets
are formed, and therefore allows the shape of the cutter pockets to
be better preserved. This also improves the ability of the cutter
pockets to have a secure fit with cutting elements.
[0037] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention
as disclosed herein. Accordingly, the scope of the invention should
be limited only by the attached claims.
* * * * *