Tech view edge polishing

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ABRASIVE TECHNOLOGY, INC. 8400 Green Meadows Dr. Westerville, OH 43081 USA (614) 548-4100 Fax: (614) 548-7617 1-800-964-TECH (8324)
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June 24, 1994 •
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Presented at ITSE, Anaheim, CA.
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VP Engineering and Quality
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Robert W. Evans, Jr. • • • •
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THE ONLY WAY TO GO
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TOOLS:
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POLISHING WITH DIAMOND
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GRANITE & MARBLE EDGE • • • • • •
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TECHVIEW
abrasive technology, inc.

Granite & Marble Edge Polishing

Conclusions
Robert W. Evans, Jr., VP Engineering and • Following the optimum operating parameters can result in over
Quality, Abrasive Technology, Inc.
B.S.M.E., Ohio State University.
a 70 % increase in productivity above current field practices (1.7
times current).
Mr. Evans has been with Abrasive Tech-
nology for four years. His prior positions • Annual sales revenue increases from a single operator can
include Director of Engineering and Quality exceed $600,000 in over half the cases when switching from typical
at TRW and Sr. Project Engineer at Gen-
current practices to more optimum levels.
eral Motors Engineering Staff.
• Following the optimum operating parameters can result in an
Abstract improved finish and minimize reworks.
Conventional polishing of granite and marble edges has • Following the optimum operating parameters can result in less
been done by hand. While this has changed somewhat with the operator fatigue and thereby improve output.
advent of automatic finishing machines, it is still very much a hand
finishing technology. The addition of power tools to aid the finisher • Both granite and marble can be effectively polished with dia-
has made the job less fatiguing but still very much a hands-on art mond tools.
form like process. Further, the control of the operating parameters • Polishing marble with diamonds and water reduces respiratory
varies widely between technicians. Surface finish quality also dust concerns for both the polisher and those in the work area..
varies considerably between individuals and their selected tools.
Today, craftsmanship continues to reign supreme in the area of • Shops doing 3/4" and thicker edges on a regular basis would do
edge polishing. well to select 3 inch diameter tools. They need to maintain their
current force level on 3/4 inch edges and press harder on 1 1/2 inch
The relatively recent addition of diamond pads for power edges (from 7.7 pounds up to near 15 pounds).
hand tools has made the job easier, particularly for granite edge
polishing. However, finish quality, while easier to achieve, still • Current hand polishing practices can be easily modified to
varies a lot because of inconsistency in operator techniques. Also achieve the optimum levels.
there is a general lack of working at the optimum levels of feeds and
• Following the optimum parameters can result in significantly
speeds for the diamond-granite polishing interface.
faster delivery times without additional work hours.
This paper presents the results of two years of work focused
upon the diamond-stone polishing system with a particular focus
upon power edge polishing by hand. The data was collected across
a wide variety of stone fabrication shops and their operators. This
FAST FORWARD? »»
was a field based study that was quite revealing. Practical If you are in a hurry, you can skip the next sections
suggestions are given to assist the practitioner in producing a and get right to the recommendations starting with
higher quality finish in less time. This is done by focusing upon the paragraph labeled "Traverse Speed" on p.6.
operating more closely to the optimum parameters for diamond
tools.


2

Discussion
Abrasive Technology, Inc. is a major manufacturer of supera-
brasive tools for a wide range of industries. In an effort to assist
its customers and the stone fabrication industry, it has con-
ducted a product development program focused upon the pol-
ishing of stone using diamond tools. An earlier paper entitled,
“Granite and Marble Polishing With Diamond Tools - The Ulti-
mate In Efficiency and Finish”, was presented at Stone Expo in
March 1994. It discussed the use of diamond tools to polish large
flat surfaces. The, then current, industry practices were exam-
ined and the test results from both laboratory testing and field
validation runs were presented. It was shown that more detailed
attention to operating parameters can result in an outstanding
finish in less time and with more productivity than had been
possible before. Practical field guides were presented for setting
up the polishing system to achieve the correct contact pres- Photo B
sures, surface speeds, water flow rates, traversing velocities and The special platform and data acquisition system were trans-
head overlaps. This paper expands upon the previous work and ported to a number of stone shops. Each available operator was
addresses the issue of correct application of diamond tools asked to polish a granite edge and a marble edge using his
when performing edge polishing of granite and marble stones. normal tools and techniques (ref photo C).
The approach taken was to design and build a special polishing
platform. This platform would need to measure and record the
forces and times being used by an operator for each grit, over a
variety of stone types. This platform had to be portable since all
the data was to be collected from polishing professionals in their
own shops, on their own stones, and using their own tools. A
three axis Kistler dynamometer was procured. Its high fre-
quency capability made it especially suitable for this work. The
dynamometer was attached to two square plates (one above the
dyno and one below). In this way, the bottom plate could be
fastened easily to a bench top. The stone could then be placed
on the top plate and clamped in place (ref photo A). Any forces
applied to the stone would then have to be transmitted through
the dynamometer, thereby producing an electrical signal pro-
portional to the actual force being applied to the edge of the
stone.
Photo C
No attempt was made to influence each person’s style and
technique. Each stone was their selection from their own yard.
The stones polished are shown in Table 1.

STONE TYPES EVALUATED

GRANITES:
• BLUE PEARL
• BLACK ABSOLUTE
MARBLES:
• WHITE CARERRA
• VERDI ALPI
• BOTTICINO
Photo A
The electrical signals were sent to amplifiers and then into a two Table 1
pen strip chart recorder (ref. Photo B). The entire system was The power tool was their own choice and from their own
quite portable and the strip chart records provided adequate equipment inventory. A list of the power tools used in shown in
resolution over the anticipated operating range (approximately Table 2.
0.5 pounds resolution).


3

EDGE POLISHING TOOLS
USED DURING EVALUATIONS

TOOL SPINDLE TYPE STONE POWER
BRAND TYPE
DIAMETER (in.) SPEED USED ON SOURCE

1 BOSCH BELT SANDER N/A 2,700 FPM MARBLE ELECTRIC

2 PORTER CABLE BELT SANDER N/A 1,550 FPM MARBLE ELECTRIC

3 MAKITA 9218-PB 4 2,000 RPM ANY, BUFF ELECTRIC

4 FLEX ORIGINAL LW1503 4 3,700 RPM GRANITE ELECTRIC

5 NIKKEN WS-5 3 2,000 RPM GRANITE AIR

6 NAT.DETROIT DSQ 5 10,000 RPM MARBLE AIR

7 NIKKEN WS-7 4 4,000 RPM GRANITE AIR
ADJUSTABLE

8 MALTABO 4 4,000 RPM MARBLE ELECTRIC
ADJUSTABLE

9 ALPHA 4 2,000 RPM GRANITE ELECTRIC

Table 2
The abrasive tools they used were theirs to choose, and again,
from their own inventory. All machine settings such as RPM and
water flow rate were their choice. Consequently, there should
not have been any issues regarding lack of familiarity with how
to perform the work successfully. Photo E
nies were quite open and willing to give of their time with their
Most operators chose to have the stone laying horizontal and to best people. Due to the production focus and the art or craft
polish the vertically oriented edge by pushing in lightly. This orientation toward edge polishing, there has been a general lack
orientation is shown in photo # A, above. One shop chose to of data collection and virtually no systematic testing for better
place the slab vertically and to polish the horizontally oriented methods and a more complete understanding of the polishing
edge with a slight downward pressure (ref. Photo D and E). This process. This is in spite of the fact that most of the companies
seemed to provide some advantage to the operator in consis- visited could benefit in a significant financial way from a more
tency of loading and minimization of fatigue. Further, he avoided optimized and consistent approach to edge polishing.
water in the face with this setup.
Data format
The forces from the dynamometer were output as lines on a
moving strip chart. A typical sample of the strip chart record is
shown in Figure 1. The upper line, labeled “grinding contact
force”, is the force being applied to press the tool into the stone.
The lower line, labeled “tangential force”, is the force being
produced from dragging the tool across the stone. It is in the
same plane as the edge being polished.
SINGLE GRIT
BLACK ABSOLUTE GRANITE
AND DIAMOND TOOLS

OPERATOR TECHNIQUE
AS OBSERVED

Photo D
General observaions GRINDING
CONTACT
The average operator had 3.9 years of experience in edge FORCE
(INTO STONE)
polishing and nearly half had over 5 years of experience. One (LBS.)

operator evaluated had 16 years of experience. There were wide
differences in technique, choice of operating parameters and
finished product appearance. There were also large differences
in the time to perform a polishing sequence. The majority of the
granite edges had to be redone because of cosmetic appearance
TANGENTAL
issues. This has to be very costly in both time and materials. FORCE
(ALONG EDGE)
There was a surprisingly strong reliance upon post polish finish- (LBS.)
ing techniques other than buffing. Chemical “coatings” of many
types are in use. Levels of commercial acceptability varied
widely. Some operators were much more skilled with one stone
than another. Years of experience did not seem to completely
predict polishing skill. It seems that training efforts could be STONE
strengthened with a focus on consistency of technique and TANGENTAL
FORCE Figure 1
selection of more optimum operating parameters. Most compa- CONTACT FORCE


4

A graphical analysis of the data is shown in Figure 2. The average titled “Granite & Marble Polishing With Diamond Tools - The
value was taken from an "eyeballed" best fit line drawn over the Ultimate in Efficiency and Finish” and is also available from
data. The max and min values were similarly taken for each trace. Abrasive Technology, Inc.
The values were recorded in tabular form across each operator,
For White Cherokee marble and both Charcoal Black and Ma-
on each stone, and for each grit used.
hogany granites, a test plan was developed using statistically
SINGLE GRIT based Designed Experiments. Variables evaluated included abra-
AND DIAMOND TOOLS sive types, bond systems and associated characteristics, and
OPERATOR TECHNIQUE
AS OBSERVED
operating parameters. The output characteristics were stone
reflectance, depth of color, overall appearance, and tool wear.
17.0 Tests were conducted almost continuously over a 24 month
period. The tooling formulations were developed in response to
GRINDING
CONTACT AVG. = 11.0 lbs.
the output characteristics initially measured. Progressive im-
FORCE
(INTO STONE)
provement was incorporated into each succeeding level of tool
0
(LBS.)
RANGE = 13.5 or + 6.75 lbs.
design and testing. The various stones’ finish sensitivities to
3.5
both small and large changes in the operating parameters were
also quantified.

3.0 Each of the variables, surface speed (SFPM), load (LB), water
SIDEWAYS AVG. = 2.0 lbs. flow rate (GPM), traverse speed (FPM), pass overlap and the
FORCE
(ALONG EDGE) 0 number of passes required were varied over a considerable
(LBS.) RANGE = 2.6 or + 1.3 lbs. range during the test program. A table of optimum values was
0.4
published which, when used, produced significantly better re-
sults than any other levels tested. We recognize that field condi-
tions are often less than optimal. Also, production equipment
STONE often lacks the adjustment and control features necessary to
SIDEWAYS
FORCE obtain the table values exactly. However, three things can be
CONTACT FORCE Figure 2 stated definitely. First, deviation from the table values detracted
Field testing summary from the optimum finish and productivity numbers we achieved
during testing on the specific pieces of White Cherokee marble,
Table 3 below shows some summary statistics from the field work Charcoal Black and Mahogany granites that we used. Second, no
we conducted on granite. The values shown are brought into one is using THE exact pieces of stone that we used. Conse-
practical focus in the section “Implications For Edge Polishing”. quently, some changes in operating parameters may be useful.
Previous work key relationships However, the table values represent a well tested and proven set
of parameters for a starting point when polishing stones in this
It is important to compare this current round of field data with
range. Third, care must be taken when changing parameters. We
the previous work. This comparison will assist in achieving a
found interactions between parameters that significantly af-
more complete understanding of where the current practice of
fected finish. An interaction between load and water flow rate,
edge polishing resides and where it needs to go in order to be at
for example, would mean that at light loads, water flow should be
a more optimum level.
low for optimum finish, but that at heavier load water flow
To that end, this section is a series of brief excerpts from the should be high to maximize reflectance, a reversal or interaction.
previous work by the same author on the use of diamonds in the The reflectance values obtained during testing are shown in
polishing of both marbles and granites. This excerpted paper is Figures 3 and 4.

FIELD TESTING - GRANITE DATA - 3/4" THICK, 12" EDGES

AVERAGE TOTAL AVERAGE
TOOL PERIPHERY LOAD POLISH TIME NUM.
OPER YEARS TOOL DIAMETER SPEED APPLIED MAX MIN LOAD TIME PERGRIT GRIT EDGE
. EXP. GRANITE TYPE (in.) RP (sfpm) (lbs) LOAD LOAD RANGE (sec) (sec) STEPS STYLE
ID
1 A 6 BLACK ABSOLUTE DIAMOND 4 2,000 2,094 6.4 10.0 2.0 8.0 574 82 7 FLAT
2 B 5 BLACK ABSOLUTE DIAMOND 4 2,000 2,094 4.9 8.0 3.0 5.0 289 41.5 7 FLAT
3 C 2 BLACK ABSOLUTE DIAMOND 4 2,0002,000 2,094 2.8 4.5 0.5 4.0 424 60.6 7 FLAT
4 D 0.5 BLACK ABSOLUTE DIAMOND 4 10,000/4,000 2,094 10.5 22.5 0.5 22.0 981 140.2 7 FLAT
5 E 0.5 BLACK ABSOLUTE MIXED 5/3 10,000/2,000 13,090/2094 1.5 4.0 0.5 3.5 534 76.2 7 FLAT
6 F 6 BLACK ABSOLUTE MIXED 5/3 2,000 13,090/1571 5.9 18.0 1.0 17.0 548 49.8 11 DEMI BULL
7 G 0.5 BLACK ABSOLUTE DIAMOND 3 3,700 1,571 8.0 15.0 3.0 12.0 232 29 8 FLAT
8 H 2 BLUE PEARL DIAMOND 4 3,700 3,875 13.4 20.0 7.0 13.0 285 40.7 7 FLAT
9 I 16 BLUE PEARL DIAMOND 4 3,700 3,875 9.9 15.0 5.0 10.0 261 37.3 7 FLAT
10 J 0.3 BLUE PEARL DIAMOND 4 3,875 13.6 17.0 8.0 9.0 386 55.1 7 FLAT
AVG: 3.9 7.7 13.4 3.1 10.4 451.4 61.2
MAX: 13.6 22.5 8 22 981 140.2
16 0.5
MIN: 0.3 1.5 4 3.5 232 29
TOP HALF AVG. 82.8

Table 3

5

WHITE CHEROKEE MARBLE
TECH SHINE™ PADS & DIAGLO M™ COMPOUND operational parameters. However, after several shop visits, we
just could not resist trying to help improve their practices. After
100 the operator had polished an edge in Black Absolute granite, we
90
showed him the strip chart graphs of his work (ref. Figures 1 &
80
70
2).We explained that a smoother, more steady motion would
REFLECTANCE

60 help eliminate the somewhat wavy appearance he had produced.
50 While it was not severe enough to reject the stone from a
40 commercial standpoint, it was noticeable under a reasonable
30 examination. Also, the edge had some lightness (lack of depth of
20
color) in a streak running over a good portion of the length of the
10

0
edge. We suggested that a closer examination of the stone after
30m 50 120 220 400 800 Buff the 120 grit would help prevent this problem in the end. He
GRIT SIZE
agreed to use an air gun to dry the stone after the 120 grit and to
Figure 3 not advance to the next grit until all of the 50 grit scratch pattern
CHARCOAL BLACK & MAHOGANY GRANITE
with TECH SHINE™ PADS & DIAGLO X™ COMPOUND had been removed. Finally, we suggested that he was spending
too much time and not getting the higher quality results possible
90
from spending less time at more optimum levels. Specifically, an
80
increase in contact pressure and a decrease in traverse speed
70
across the stone with fewer passes should help achieve the
60
REFLECTANCE

optimum finish in the minimum time. He agreed to try this
50
approach on the adjacent side of the same stone he had just
40
polished. The change in method is shown for the same operator,
30

20
grit and stone in Figure 5.
10

0 SINGLE GRIT
30m 50 220 600 800 1800 Buff Amb.Temp.
GRIT SIZE AND DIAMOND TOOLS

Figure 4 OPERATOR TECHNIQUE
AFTER TRAINING
We have found that the two most significant variables for con-
trolling polishing results are the contact pressure on the stone
and the tool rotational velocity. Water flow is important. Further,
it is clear that the number of passes the tool makes over a single GRINDING
CONTACT
spot on the stone is important. Of course, the proper values will FORCE
(INTO STONE)
be different for different tools from different sources. Also, we (LBS.)

know that stone varies widely. However, for a given stone, the
two key variables that the producer can control are the load on
the stone and its resultant contact pressure and the surface feet
per minute being produced by the motor RPM and the diameter
of the tools. The optimum contact pressure for both marble and
granite was found to be 9.5 psi. The optimum surface speed for
marble was found to be 850 SFPM and for granite it was 1400
SFPM. The optimum water flow rate was found to be 0.5 GPM. The
optimum traverse speed was found to be 5 FPM. The optimum
number of passes for marble was found to be 2 passes while for TANGENTAL
FORCE
granite the optimum was 4 passes. The diamond grit sequence (ALONG EDGE)
(LBS.)
commonly used in the field for granite is 50, 120, 220, 600, 800,
1800, and 3500. For marble, the sequence is 50, 120, 220, and 400.
Implications for edge polishing
The differences in technique and associated times to polish,
along with the high frequency of reworks greatly reduces pro-
ductivity. We estimate that in half the cases, over a 70 % increase Figure 5
in output per operator can be achieved if techniques are opti- The analysis of the data is shown in Figure 6.
mized for first time acceptance and standardized for consistency
between operators. This 70 % increase number initially came The dramatic change in technique was achieved after a brief five
about when we decided to attempt to train a polishing technician minute discussion. The quality of the final finish was signifi-
to more closely duplicate the practices that had worked so well cantly improved to a level well above “just commercial”. This
in the large flat surface work we had previously conducted. Our shows that a little training can be quite effective when properly
original plan was just to observe current practices and quantify focused and delivered.


6

SINGLE GRIT produce 75 lineal feet of polished granite edges per shift using
AND DIAMOND TOOLS the “after training” optimized method. For estimating purposes,
OPERATOR TECHNIQUE
AFTER TRAINING
we used a six foot counter, 0.75 inches thick, of granite, with a flat
polished edge being sold for $500. Using the productivity num-
bers above, the improved method would yield 5 additional
17.0 counters out the door per person per shift. That translates into
GRINDING $2500 per day in increased sales revenue or $600,000 per year per
CONTACT
FORCE AVG. = 14.5 lbs. person! The benefits from this change in productivity are in
(INTO STONE)
(LBS.)
RANGE = 4.0 or + 2.0 lbs. three areas. First, more sales mean more profits. Second, in-
13.0
0
creased output per labor hour means a more competitive shop,
getting more jobs and winning the jobs it really wants to win.
Finally, and perhaps most importantly today, an optimized
operation can promise quicker delivery times and meet its
commitments more easily. Of course, each stone is different, and
each operator’s current practices are different. These numbers
do not include the additional operator setup times that go with
2.0
this increased output. Also, the favorable impact of reduced or
SIDEWAYS AVG. = 1.8 lbs.
FORCE
0
eliminated reworks has not been included in the estimates. Our
(ALONG EDGE)
(LBS.)
RANGE = 1.0 or + 0.5 lbs.
data suggests that elimination of reworks may yield another 33%
0.4
improvement! In any case, savings per operator will vary. How-
ever, the data and field experience clearly show that a tremen-
dous gain in productivity is possible when using diamond tools
properly.
Figure 6 Traverse speed:
A comparison of the “as found” method and the “after training” The optimum traverse speed is 5 feet per minute (FPM). For
method is shown in Figure 7. practical purposes, an operator should be moving the power
tool across the stone edge in a smooth motion that covers 1 foot
CYCLE TIME COMPARISON
TWO METHODS - ONE GRIT
every 12 seconds. It may be helpful to mark off 1 foot sections
AS FOUND with masking tape and counting “one thousand and one, one
thousand and two,....one thousand and twelve” for a while to
help get the correct idea of an appropriate traverse rate.
Number of passes:
Granite requires four passes and marble only two passes. A pass
is defined as moving from one end to the other. The operator
would then move at the same speed back to the starting point.
15.0 cm This would be the completion of two passes. When polishing
= 112.5 sec granite this sequence would be repeated again (a total of 4
START FINISH passes).
Surface speed:
AFTER TRAINING
• Smoother motions This parameter is somewhat more difficult to manage. Each
• More consistant pressure
• Less total time operator seems to have his/her own power tool preference and
each manufacturer’s power tools operate at different speeds.
Some tools are speed selectable while others are of a fixed RPM
10.9 cm
design. The other variable that effects surface speed is the
= 81.8 sec
START FINISH diameter of the polishing disk. Most shops are operating with
either 3 or 4 inch disks. Considering the importance of surface
speed, it will pay big dividends to the operator that takes a little
Figure 7 time to optimize this parameter. From the previous work, the
The charts were run at the same speed during the tests. There- optimum value for granite is 1400 sfpm while that of marble is 850
fore the difference in lengths of the two lines represents the time sfpm. The nomograph below (Figure 8) shows the interplay
saved per grit when converting to the more optimal method. between the diameter and the spindle speed and their effect
This saving represents a 37% increase in finished edge footage upon surface speed. While it may not be possible to hit the
for this one operator! This operator was still using too much time optimum values exactly, the closer you get to the optimum the
to achieve the optimum polish. We found that half of the better the results. Knowing the tool diameter and the handpiece
operators tested can produce an average of 43.3 lineal feet of RPM, draw a straight line connecting the two values. Where the
polished granite edges per shift using their current methods line crosses the surface speed line is the speed this set up will
when excluding setup times. The same operators can each produce. An operator can either adjust the RPM via the manufac-


7

turer provided dial or select another power tool with a more
favorable RPM in order to achieve a more optimal surface speed. 4 INCH DIAMETER TOOLS
CONTACT AREA ANALYSIS
Of course, changing the tool diameter selection can also be an
effective way to optimize surface speed. In some cases, changes CENTERED ON STONE

in selection of both the hand tool and the disk diameter may be
required to obtain optimum levels.

NOMOGRAPH FOR OPTIMIZATION OF
SURFACE SPEED (SFPM)
HAND EDGE POLISHING 3/4" 1 1/2"

5000
4500
4000

3500
OFFSET ON STONE
7000 3000
6000
3/4"
5000 2500 1 1/2"
4000
OPTIMUM 2000
3000
FOR GRANITE 1900

5 2000
1500
4
1500
• 1400

1000

3
900
800
700
• OPTIMUM
FOR MARBLE
1000
1100
Figure 9
TOOL SURFACE HAND TOOL becomes polished. If the stresses are too high, the excess
DIAMETER SPEED SPEED pressure helps to break the diamond tool’s bond prematurely
(IN) (SFPM) (RPM)
and tool life suffers. Table 4 summarizes the contact area and
Figure 8 force considerations for three tool sizes.
Contact pressure:
CONTACT PRESSURES AND APPLIED
FORCES
The issue of contact pressure relates to four variables. The first FOR SELECTED TECHNIQUES

variable is how hard the tool is pressed onto the stone. This is EDGE CONTACT AREA
FORCE
REQUIRED
FORCE
REQUIRED
TOOL CONTACT AREA
expressed in pounds of force. The second variable is the gross TOOL
FORMULA
DIAMETER
(in.)
THICKNESS
(in.)
CENTERED
(sq.in.)
FOR 9.5 PSI
CENTERED
OFFSET
(sq.in.)
FOR 9.5 PSI
OFFSET
contact area over which the load is distributed. This is measured (lbs.) (lbs.)
SUPER-DIASHINE™:
in square inches. The third is the percentage of the contact area 3 3/4 0.763 7.2 0.983 9.3
3 1 1/2 1.712 6.3 1.768 16.8
that is actually resin and diamond touching the stone. Finally, 4
4
3/4
1 1/2
1.039
2.200
9.9
20.9
1.169
2.412
11.1
22.9
because the edge is a narrow line and the polishing disk has a PRO-DIASHINE™:
3 3/4 0.812 7.7 0.680 6.5
larger diameter than the edge width, the geometry of the pad 3 1 1/2 1.646 15.6 1.519 14.4
4 3/4 1.232 1.7 0.961 9.1
orientation to the edge must also be considered. Figures 9 shows 4
5
1 1/2
3/4
2.575
1.405
24.5
13.3
2.237
1.039
21.3
9.9
some of these considerations graphically. 5 1 1/2 2.620 24.9 2.468 23.4

Stone is polished by the contact pressure between it and the Table 4
diamond tool. Imagine a 10 pound weight 1 inch square resting Figures 10 and 11 show this data graphically for the two most
upon your hand. The weight does not cause you pain because the common edge thicknesses and for the two styles of tool position-
contact area is relatively broad (1 square inch) and the load is ing (centered and offset). Based upon the field data, 7.7 pounds
relatively light (10 pounds). This translates into 10 pounds per of load on the stone is commonly achieved. In Figure 10, we see
square inch or 10 psi. If however, you then turn the weight up on that tool to stone centering and offset techniques on 3/4 inch
edge so that the entire weight is pressing onto your hand over a edges produce little difference for the 3 inch Pro-Diashine™ (3p)
0.1 square inch area, your level of comfort just deteriorated and 4 inch Super-Diashine™ (4s) (around a 10-15% change).
significantly. It is still the same 10 pounds but the contact area However, the 5 inch Pro-Diashine™ (5p) and 4 inch Pro-Diashine™
through which it is pressing on your hand is now just 10% of what (4p) produce a substantial difference in contact load require-
is was previously. This new arrangement translates into 100 ments depending upon technique (up to a 30% change). This
pounds per square inch (100 psi). It is the high contact pressures seems to suggest that an operator should select one approach or
that break down the stone piece by piece. If the stresses are not the other and stay with it to enhance his/her consistency of load
high enough, the stone does not become scratched and it never and resultant contact pressure. The 3 inch tools seem to be


8

With loading being so important, the efficient shops need a
OPTIMUM LOAD FOR 3/4 INCH EDGE POLISHING
6/94 rwe method to assist the polishing technician in periodic calibration
14
of his/her feel for the correct loading. One simple and inexpen-
12 sive way to accomplish this would be to obtain a bathroom scale.
X
10
X
X This scale could be placed in the shop in a standard and
X
8 convenient location for a painless check on a scheduled basis.
COMMONLY ACHIEVED LOAD The human memory for correct feel is somewhat weak and in
LOAD (lbs)

X
6
cent 3/4
offset 3/4
4
X
need of frequent reinforcement. A "start of shift" habit could be
2
just enough to emphasize the importance of correct loading and
0
frequent enough to become ingrained.
3-S 3-P 4-S 4-P 5-P
Water flow rate:
TOOL DIAMETER AND TYPE

Water flow rates are generally uncontrolled beyond “full on” and
Figure 10 “full off” flow levels. Because the water tends to run off an edge
much more so than off a slab, more water is needed in edge
close to optimum contact pressures at the commonly achieved
polishing. Too little water translates into shortened tool life and
load. The 5 inch tools need an increase in contact load for either
unwanted scratches from the stone swarf as a secondary abra-
tool orientation, centered or offset (between 2 and 6 pounds
sive. Too much water can cause tool hydroplaning and poor
increase). In Figure 11, the tool to stone centering and offset
surface finish or at least require a longer time to achieve a good
techniques on 1 1/2 inch edges produced little differences for
polish. We did not conduct a full investigation into the optimum
any of the tools surveyed.
water flow rate required when edge polishing. However, it seems
apparent that some level would be more optimum than others.
OPTIMUM LOAD FOR 1 1/2 INCH EDGE POLISHING
6/94 rwe Further, it is nearly impossible to determine what level is opti-
25

X X mum if there is no way to repeatedly obtain a given flow rate.
X
20
cent 1-1/2
Also, there is a need to identify relative flow rates in order to be
X X offset 1-1/2 able to arrive at statements such as “higher is better”. For these
15
X
reasons and to assist all operators in setting up to the same
LOAD (lbs)

10
COMMONLY USED LOAD
levels, we recommend that the water flow rate be set by a control
valve and gage placed before the hand tool. The valve on the
5
hand tool should only be used for full on and full off switching.
0 We have had good success with a relatively inexpensive flow
3-S 3-P 4-S 4-P 5-P

TOOL DIAMETER AND TYPE meter and control valve assembly that is easy to set, gives
numerical flow values and is consistent. The cost of the system
Figure 11
is around $140 and it would be well worth the investment.
However, the optimum contact loads required are well above
what is typically used by skilled operators. Further, as the tool
Summary
diameter gets larger the required forces increase significantly. There are several key lessons to be learned from this work.
For 1 1/2 inch edges, the case for 3 inch tools seems clear. The 1. Major productivity improvements (over 70 %) can be achieved
operators need to increase their contact force by nearly 100% to from a more disciplined and informed approach to edge polishing.
get to optimum productivity levels. They need to nearly triple 2. Annual sales revenue increases from a single operator can
their current load when using the 5" Pro-Diashine™ (5p). For exceed $600,000 per year in over half the cases we observed
these reasons, a shop doing both thicknesses of edges on a when switching from typical practices to more optimum levels.
regular basis would do well to select 3 inch diameter tools. They
3. Rework can be greatly reduced by following a more consistent
should maintain their current 7.7 lb. load on 3/4 inch edges and
and optimum approach. A 33% increase in productivity is pos-
press harder on the 1 1/2 inch edges (from 7.7 pounds up to 15
sible in over half the cases we observed.
pounds). Figure 12 shows this for the centered technique for
both edge thicknesses across the family of tool sizes and types. 4. Current hand polishing techniques can be easily modified to
achieve optimum levels.
OPTIMUM LOAD FOR CENTERED TOOL AT 3/4 & 1 1/2 INCH EDGE THICKNESSES
6/94 rwe
5. Shops doing 3/4" and thicker edges on a regular basis would do
25
X X
well to select 3 inch diameter tools. They should maintain their
X
current 7.7 pounds of force on the 3/4" edges and press harder on
20
cent 3/4
X cent 1-1/2
the 1 1/2 inch edges (from 7.7 pounds up to 15 pounds).
X
15
X
6. Following the optimum parameters can result in significantly
LOAD (lbs)

10 faster delivery times because of the large increases in productivity.
5
CURRENTLY ACHIEVED LOAD Special thanks
I want to extend my heartfelt appreciation to all those who so
0

3-S 3-P 4-S 4-P 5-P willingly helped to make this project a success. None of this
TOOL DIAMETER AND TYPE
would have been possible without the enthusiastic support of all
Figure 12 who participated. Thanks team!


9

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