U.S. patent number 4,262,186 [Application Number 05/846,211] was granted by the patent office on 1981-04-14 for laser chem-milling method, apparatus and structure resulting therefrom.
This patent grant is currently assigned to Rohr Industries, Inc.. Invention is credited to Donald A. Provancher.
United States Patent |
4,262,186 |
Provancher |
April 14, 1981 |
Laser chem-milling method, apparatus and structure resulting
therefrom
Abstract
The materials to be chem-milled are coated with a maskant
material, a template having a specific hole pattern is then placed
over the masked surface of the material. A laser beam is then
directed towards the template and is scanned either manually or by
numerical control means along the hole pattern. The laser is
maintained at each hole for a sufficient length of time to enable
the maskant to be burned from the material. The material is then
chem-milled by any conventional means thereby forming holes through
the material at the maskant free areas. The remaining maskant is
then removed from the surface of the material.
Inventors: |
Provancher; Donald A.
(ChulaVista, CA) |
Assignee: |
Rohr Industries, Inc. (Chula
Vista, CA)
|
Family
ID: |
25297265 |
Appl.
No.: |
05/846,211 |
Filed: |
October 27, 1977 |
Current U.S.
Class: |
219/121.68;
216/54; 216/65; 219/121.7; 219/121.73; 219/121.84; 347/225 |
Current CPC
Class: |
B23K
26/0661 (20130101); B23K 26/009 (20130101); B23K
26/18 (20130101) |
Current International
Class: |
B23K
26/18 (20060101); B23K 009/00 () |
Field of
Search: |
;219/121L,121LM,121EB,121EM ;346/76L ;29/423,424 ;156/272,643 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rubinson; Gene Z.
Assistant Examiner: Paschall; M.
Attorney, Agent or Firm: Schlesinger; Patrick J. Gilliam;
Frank D.
Claims
What is claimed to be covered by United States Letters Patent
is:
1. A method for producing sheet material from imperforated sheet
material comprising the steps of:
coating all the exposed surfaces of said imperforate sheet material
with a chem-mill resistant maskant;
securing a removable first template having openings therethrough to
said imperforate sheet material for communicating with one coated
surface thereof;
directing a laser beam through said openings in said first template
for a sufficient time to remove said maskant from said imperforate
sheet material within said openings;
removing said first template;
chem-milling the maskant free surface of said imperforate sheet
material; and
removing the remaining maskant from the now perforated material
after said chem-milling.
2. The method as defined in claim 1, additionally comprising the
step of:
securing a second removable template having openings therethrough
for communicating with the side of the coated material opposite the
side adjacent the first template after coating the surface of said
material and prior to the step of directing said laser beam through
said openings and removing said second template prior to the
chem-milling step.
3. The method as defined in claim 2, including the step of aligning
the aperture in said first and second templates prior to the step
of directing said laser beam through said openings.
4. The method as defined in claim 1, including the step of cooling
said template while directing said laser beam through said
openings.
5. Apparatus for removing maskant from selected areas of a sheet of
imperforate material having all surfaces coated with a maskant
material for the purpose of chem-milling those selected areas to
form perforations therethrough comprising:
a first template means having openings therethrough corresponding
to said selected areas positioned on one surface of said
imperforate sheet material;
a laser beam for removing the maskant material positioned beneth
the openings through said first template; and
a second identical template is positioned on the opposite side of
said material from said template, the openings in said templates
being aligned and said laser is utilized to remove the maskant
material positioned beneath the pattern of openings through said
second template.
6. The invention as defined in claim 5, wherein said first and
second templates further include cooling means.
7. Apparatus for removing maskant from selected areas of a sheet of
imperforate material for the purpose of chem-milling those selected
areas to form perforations therethrough comprising:
a maskant material for coating all the exposed surfaces of said
imperforate sheet material;
a first template means having the desired pattern of openings
therethrough for chem-milling said selected areas positioned on one
surface of said material;
a second identical template positioned on the opposite side of said
material from said first template, the openings in said templates
being aligned;
a laser beam for removing the maskant material positioned beneath
said pattern of opening through said templates; and
said first and templates include cooling means, said cooling means
is a conduit around the periphery of said template for circulation
of a cooling fluid therethrough.
8. Apparatus for removing maskant from selected areas of a sheet of
imperforate material for the purpose of chem-milling those selected
areas to form perforations therethrough comprising:
a maskant material for coating all exposed surfaces of said
imperforate sheet material;
a first template means having openings therethrough corresponding
to said selected areas positioned on one surface of said
imperforate sheet material;
a second identical template positioned on the opposite side of said
material from said first template, the openings in said second
template being aligned;
a laser beam for removing the maskant material positioned beneath
said pattern of openings through said template; and
said first and second templates including cooling means,
said first and second templates further include cooling means,
said templates are hollow intermediate their outer surfaces with
sealed tubes providing openings therethrough, said hollow portion
of said templates having means for circulating a cooling fluid
therethrough.
9. The invention as defined in claim 5, wherein said templates have
highly reflective outer surfaces.
Description
BACKGROUND OF THE INVENTION
The inventiion relates to chem-milling and, more specifically, to
preparing the surface of material coated with chem-mill resistant
maskant in the areas desired to be chem-milled.
The conventional method of preparing material to be chem-milled in
those specific areas is to coat the surface of the material with a
chem-mill resistant maskant material and then mechanically punching
or drilling holes of a smaller diameter than the desired resultant
diameter hole through the maskant and/or maskant and the material.
This method, although highly successful for certain utilization of
perforated finished material, has been found to cause an increase
in the occurrence of material fatigue and to highly stress the
material adjacent the hole which causes warpage of the material
requiring the additional operation of flattening the material prior
to use.
The problems existing in the current phase of the art have not been
successfully overcome until the emergence of the instant
invention.
SUMMARY OF THE INVENTION
The invention provides a convenient method for producing a
perforated sheet of material that has uniform hole size, good
fatigue properties and does not require the additional operation of
flattening prior to ultimate use.
The main object of this invention is to produce a sheet of
perforated material with reduced fatigue properties and stress
reduction around the perforations to prevent warpage of the
material.
Another object of this invention is to produce a sheet of uniformly
perforated material with a reduction of manufacturing steps in such
materials as titanium, inconel, aluminum and other types of
material subject to chem-milling.
Another object of the invention is to produce an acoustic panel
containing perforations of selected and uniform size.
Other objects, features and advantages of the present invention
will become apparent from the following description taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a showing of a cross-section of material maskant applied
prior to the chem-milling operation.
FIG. 2 is an exploded perspective view of the material, maskant,
templates and cooling tube.
FIG. 3 is a perspective showing of the material, maskant and
template in place for the laser drilling of the maskant.
FIG. 4 is a partial cutaway perspective view of a second type
template having additional cooling means.
FIG. 5 is a showing of a finished flat piece of material with
chem-milled apertures.
FIG. 6 is a showing of material to be scribed in the form of
conical section.
The same numeral reference will be used to denote the identical
part or element throughout the drawings and specifications.
DESCRIPTION OF THE FIRST PREFERRED EMBODIMENT
Referring now to FIG. 1, a piece of material 10 of the type
normally subjected to a chem-milling process is coated with a
maskant 12 resistant to the chemicals encountered in the
chem-milling process. This maskant can be applied by any known
means, such as, but not limited to, dipping, spraying, brushing,
etc. A maskant found suitable for conventional chem-milling
precesses is that product having the trade name Dap Coat 1001. It
should be understood that various other maskants are available that
will work equally as well in practicing the instant invention. The
material 10 to be chem-milled could be of any thickness suitable
for any type of chem-mill process, as for example, 1/1000ths of an
inch and up within practical limits.
Referring now to FIGS. 2 and 3, after the material 10 has been
coated with the maskant 12, a template 14 is placed over at least
one side of the material and secured thereto by any convenient
means, so as to prevent any relative movement between the template
14 and the material 10. The template has been predrilled, or
apertures have been formed by various other methods, to provide the
plurality of selectively sized and positioned apertures 16. These
apertures 16 can take many shapes, forms and patterns depending on
the shape of the required finished openings in the material 10.
These apertures 16 will be sized slightly smaller than the finished
aperture size desired, so that sufficient material for finishing
but not an excess of material may be removed during the
chem-milling process without exceeding the required size. It should
be understood that for thin material 10 to be chem-milled, only one
template 14 may be required, and with thicker material it may be
desirable to have a second template 14 positioned on the opposite
maskant coated surface of the material. Thus, the material coated
with the maskant would be sandwiched between two identical pattern
templates 14. Although thick materials may be chem-milled by use of
a single template, it has been found that the resulting apertures
will be tapered away from the template side of the material. When
material of a given thickness is sandwiched between two templates
and chem-milled from both sides, the end product will have holes of
improved uniformity over those chem-milled from one side only.
The template 14 should be constructed of a metal which has a very
high reflectivity and low laser energy absorptivity, such as
aluminum or an equivalent thereto. Templates constructed of
nonreflecting or low reflecting material may be plated on their
outer surface with gold, copper or an equivalent material to obtain
the required highly reflective surface desired. In some instances,
the template may be thick in cross-section (see FIG. 4) and contain
walls around the perforations with their surfaces 15 forming
passageways therethrough, these passageways are interconnected to
supply and return conduits 17, 19 provided for a fluid flow, for
the purpose of cooling the template. The fluid could be tap water
or any other fluid medium generally considered for heat absorption.
Other means, such as a conduit 21 positioned around the periphery
of the template with the template forming the inner surface of the
conduit (see FIG. 2), may be used to cool a template having minimum
thickness and, therefore, is not suitable for passages as
hereinbefore described. The fluid may be circulated by pump 23 and
cooled by a convenient series heat sink 25.
The chosen template 14 or templates 14, as the case may be, are
firmly secured to the material 10 so that relative movement between
the template or templates and material 10 does not exist and, in
the instance where two templates are utilized, the holes of the
templates must be properly indexed or aligned. A laser beam 18 is
then scanned across the hole or pattern of the template, both
templates when two are utilized pausing at each opening
sufficiently long to burn away the maskant beneath. The laser can
be pulsed so that the beam is only present when a hole is
positioned beneath it. The template and material either being moved
with respect to the laser beam or the laser beam being moved with
respect to the template and material. The movable unit may be moved
manually, by suitable mechanical means or by numerical control
means. Any convenient type laser may be utilized to practice the
invention that is capable of performing its required functions,
namely, burning away the maskants beneath the hole of the template.
Any commonly known laser, such as a CO2 laser, provides
satisfactory results.
It has been found that for energy conservation, the laser beam
cross-section should be no larger than the aperture 16 in the
template which it is directed through and that, to a degree, the
thicker the template, the more efficient the operation. It has been
found that a laser beam of greater diameter of the apertures of the
template, must pass through, may be used to satisfactorily burn
away the maskant but uses an excessive amount of energy and that
portion of the laser beam striking the surface of the template
adjacent to the aperture 16 is wasted and dissipated into the
template as heat energy.
Referring now specifically to FIG. 5, the chem-milled material 10
is shown with apertures 23 therethrough positioned where the
maskant 12 had been removed by the laser beam 18.
Referring now to FIG. 6, types of structures such as the one shown
in this Figure and identified as material 20 are generally not
compatible to the use of a template as hereinbefore described. In
the instances where the use of a template is impractical for
various reasons, the laser beam 18 may be applied directly on the
maskant coated structure and scanned by any convenient means, such
as by numerical control, for removing the maskant from a designated
area. This feature is also very important where the area 22 to be
etched away is of considerable size requiring continuous scanning
of the laser.
It will be apparent to those skiled in the art that many
modifications and variations may be effected without departing from
the spirit and scope of the novel concept of the present
invention.
* * * * *