METHOD OF MAKING ABRASIVE ARTICLES WITH METALLIZED BACKING FABRIC AND ARTICLES MADE THEREBY

METHODE DE FABRICATION D'ARTICLES ABRASIFS SUR SUPPORT METALLISE ET ARTICLES AINSI OBTENUS

English Abstract

ABSTRACT
A method is disclosed for making abrasive articles
having abrasive particles embedded in elecrodeposits of metal
provided at a multitude of discrete locations on a backing
fabric. The backing fabric is first coated with a vaporized
metal such that the vaporized metal becomes firmly attached to
the fabric to provide a conductive coating. The coating is
masked at the discrete locations. Then metal is deposited
elctrolytically at the discrete locations in the presence of the
abrasive particles so that the abrasive particles become embedded
in the metal. The method permits the manufacture of an abrasive
strip that is ready for use, without the need to bond it unto a
backing material.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of making an flexible abrasive article having
abrasive particles embedded in electrodeposits of metal provided
at a multitude of discrete locations, comprising coating a
backing fabric with a vaporized metal such that the vaporized
metal becomes firmly attached to the fabric to provide a
conductive coating, masking said conductive coating and to expose
only said discrete locations, and electrodepositing said metal
and said coating at said discrete location, using said coating as
an electrode, in the presence of said abrasive particles such
that said particles become embedded therein.
2. A method as claimed in claim 1 wherein said
vaporized metal is sprayed onto said fabric.
3. A method as claimed in claim 2 wherein said
vaporized metal is sprayed with an arc spray gun.
4. A method as claimed in claim 2 wherein said
vaporized metal is sprayed with a plasma spray gun.
5. A method as claimed in any one of claims 2, 3, or 4
wherein said electrodeposited metal is nickel and said vaporized
metal is copper.
6. A method as claimed in Claim 1 wherein said fabric
is made of a scoured polyaramic yarn.
7. A method as claimed in Claim 6 wherein the yarn is
made of p-poly(pheneylene) terephthalamide fibre.
8. A method as claimed in Claim 7 wherein the fabric is
about 1500 denier.
9. A method as claimed in Claim 1 wherein the mask is a

plastisol mask applied by a silk screen process.
10. An flexible abrasive article comprising a backing fabric, a
coating of vaporized metal deposited on said fabric and firmly
attached thereto, and a multitude of metal deposits having
abrasive particles embedded therein provided at discrete
locations on said metal coating.
11. An abrasive article as claimed in Claim 10, wherein
said metal coating is copper and said metal deposits are nickel.
12. An abrasive article as claimed in Claim 10 or 11,
wherein said abrasive particles are diamond grit.
13. An abrasive article as claimed in Claim 10, wherein
said abrasive article comprises a strip of said fabric formed
into a belt.

Description

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This invention relates to a method of making abrasive
articles having abrasive particles embedded in electrodeposits of
metal at discrete locations, and to an article made thereby.
Various proposals have been made relatlng to the
manufacture of abrasive articles employing diamond particles
embedded in electrodeposits of nickel on a conductive substrate.
For example, our copending application Serial No. 518,201, filed
September 15, 1986, discloses a technique whereby a mask is
formed on a conductive mesh and nickel bearing diamond particles
i8 deposited on the mesh at discrete locations defined by the
mask. For use in industrial applications, the mesh generally
needs to be bonded onto a backing material, which may, for
example, be a supporting disk or a fabric belt, the latter being
an important application for the abrasive material. The problem
with bonding the conductive mesh onto a backing fabric is that a
two-stage process is involved. The abrasive material is
manufactured in an electrolytic tank, and it must then be cut to
~ize and laminated onto the backing fabric with a suitable
material. This process is labour intensive and furthermore the
requirements on the adhesive to withstand heat and water, used
for cooling purposes, are stringent.
An ob~ect of the invention is to provide a improved
manufacturing technique.
According to the present invention there is provided a
method of making an abrasive article having abrasive particles
embedded in electrodeposits of metal provided at a multitude of
discrete locations, comprising coating a backing fabric with a
vaporized metal such that the vaporized metal becomes firmly
attached to the fabric to provide a conductive coating, masking
said conductive coating to expose only said discrete locations,
and electrodepositing said metal and said coating at said
discrete locations, using said coating as an electrode, in the
presence of abrasive particles such that said particles become

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embedded therein.
The above described method permits the complete
elimination of the lamination stage and the fabrication of an
abrasive belt directly onto the backing fabric. The backing
fabric is preferably made of polyaramid yarn, such as p-
poly(phenylene) trephthalamide and sold by Dupont under the
trademark Kevlar.
The fabric is preferably made of scoured 1500 denier
yarn having a balanced weave.
The invention also provides an abrasive article
comprising a backing fabric, a coating of vaporized metal
deposited in said fabric and firmly attached thereto, and a
multitude of metal deposits having abrasive particles embedded
therein provided at discrete locations on said metal coating.
The abrasive particles are preferably diamond grit.
The coating metal can be copper and the electrodeposition metal
nickel.
The invention will now be described in more detail, by
way of example only in which:-
Figure 1 is a plan view of a section of fabric bearingnickel deposits;
Figure 2 is a cross section of a small length of the
fabric shown in Figure l; and
Figure 3 is a perspective view of an abrasive belt made
according to the invention.
In the accompanying drawings, Figure 1 shows a strip of
Kevlar fabric (Kevlar is a trademark of Dupont for P poly
(phenylene terephthalmide) yarn having deposited thereon, at
discrete locations and in a uniform pattern, roughly circular
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deposits 2 of nickel, the deposits bearing abrasive particles
formed of diamond grit. The deposits 2 can be seen more clearly
in Figure 2, which shows in enlarged cross section, a small
length of the fabric shown in Figure 1. The diamond particles
are referenced 3.
The nickel deposits 2 are formed on a vaporized copper
coating 4 firmly attached to the Kevlar fabric.
As shown in Figure 3, the strip of Kevlar fabric is
folded over to form a belt 5, with the two ends being lap jointed
along a wav-y line 6 and held together by means of an overlying
adhesive strip 7.
Unlike the previous proposals, the nickel deposits 3
are formed, by means of the copper coating 4, directly onto the
Kevlar backing fabric.
The abrasive belt is made from a Barrday F-2160/175
Kevlar 29-1500 denier scoured fabric. The fabric is then coated
with a layer of vaporized copper, which has maximum compatability
with nickel in an electrodeposition process. The copper should
be fir~ly attached to the fibers making up the Kevlar fabric.
This is achieved by Tpraying the vaporized copper onto the Kevlar
fabric with a Metco~type 12 E 4-arc all purpose metalizing spray
gun. The arc spray gun forms an arc between a pair of copper
electrodes and blows the vaporized copper onto the fabric by
means of an air jet.
With this technique, approximately one square foot of
fabric can be coated to a thickness of 2 mils in 10 seconds. To
ensure good penetration, the fabric should be stretched out on a
flat surface and the arc spray gun uniformly moved over the
fabric.
Other techniques for coating the fabric have also been
successful. A less coarse deposit can be achieved with the Metco
nova advanced plasma gun, and it is also possible to use a copper
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wire vaporized by means of an oxy-acetalyne flame. The latter
technique, however, leads to a coarser deposit, which in turn can
render the subsequent masking step, to be described, more
difficult. Other techniques, such a vacuum deposition,
electroless deposition, spraying, and painting can be employed to
coat the fabric with a conductive surface, but the preferred
technique for adhesion, fineness, and uniformity of attachment is
the arc spray gun.
When a suitable copper coating has been built up on thè
Kevlar fabric, with good penetration of the copper into the
fabric fibres, a mask, such as a polyvinyl coride mask, having
symmetrically disposed therein a very large number of holes
(approximately 90 per square inch) of about 1/16 inch in
diameter, and the mask being of a thickness of about 3/4 of
thousand of an inch, is applied to the copper coating. The mask
can be laminated to the mesh from a silicone release paper,
undera heat and pressure at 350 degrees F and 85 PSI. Tthe mask
is first formed on the silicone release paper by a silk screen or
other suitable process. The mask is preferably applied to the
silicone release paper in the form of a plastisol.
Once the mask has been applied to the copper coated
Kevlar fabric, the laminate is then placed in an electrolytic
tank, for example the commercial nickel sulfamate bath supplied
under the trademark SNRT24 by Hansing operated at 170 amps and 9
volts DC and at a temperature of 140 degrees F. The bath has a
nickel anode, and the copper coating is made the cathode. As a
result, nickel deposits build up on the portions of the copper
coating exposed through the holes in the mask. During the build
up of nickel, abrasive diamond particles are distributed over the
fabric 80 as to become firmly embedded in the nickel deposits.
The electrodeposition process can be carried in a
manner similar to the described in our copending application
Serial NQ. 518,201, with the coated Kevlar fabric in effect

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taking the place of the conductive mesh.
It is because the ma8k hag to be applied to the copper
coating that the coarseness of the coating is important. As
mentioned above, the arc spray gives a reasonably uniform
coating, in which the mask can be attached. If the coating is
too coarse, the coarse particles Will tend to penetrate the mask
causing nickel to be deposited on them at unwanted locations
during the deposition process.
The treated fabric, when it emerges from the bath, can
be cut to size and is ready for use as an abrasive without the
need to have it laminated onto a backing material. The Kevlar
fabric is extremely strong and well suited to most industrial
applications.
The fabric is pr~ferably coated on the back with an
A adhesive, such as Bostik 7070 adhesive, to reduce fraying at the
edges. The two ends are preferably joined together in a wavy lap
joint, as illustrated in Figure 1, and overlayed on the inside
with a strip of fabric. The same Bostik~7070 adhesive can be
employed.
In order to increase the strength of the belt further,
the strip can be stitched to the fabric with Kevlar thread.

Representative Drawing