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Shorter blade life than usual - Download the PDF (24kb)
Diamond saw blades rely upon many interactions for effective self sharpening
action.
Some basics for successful diamond blade use are having a mechanically sound
saw of adequate power and appropriate blade shaft speed, diamond blades
with adequate clearances between the side of the diamond section and the
steel blade core, correct coolant flow, correctly chosen diamond blade
specification for the material and cutting objectives. Unexpected reduction
in blade life could be caused by:
Blade
When a blade has been specified for and found efficient in maximum depth
sawing, the bond may act too soft for the same application when sawing at
shallower depths. For example sawing asphalt at maximum depth of 125mm
(350mm blade) will probably affect specification choice compared with
sawing at 25mm. In effect the more rapid progress of the blade will result
in more cuttings abrading the bond resulting in early release of sound
diamond, hence shorter life. Keep an eye on changing conditions.
Coolant
Water volume can affect blade life, it can either lengthen life or shorten
it. High volumes of water efficiently flush abrasive cuttings away and
reduce the wear rate of the bond. Low volumes of water allow greater
abrasion and wear of the bond to take place. Rapid bond wear exposes diamond
more quickly than slow bond wear. If the diamond is is good condition slower
bond wear will increase blade life. Damage to blade coolant pipes, plumbing
or water supply inadequacies can shorten blade life through increased
abrasion and premature loss of good condition diamond.
Saw mechanical condition
The most likely cause of unexpected short blade life due to mechanical
problems is collapse of the diamond blade shaft bearings causing the blade
to hammer and vibrate out of round. This hammering smashes diamond crystals
and causes loss of diamond teeth. Fifty % of blade life can be lost in this
way.
Change in concrete or asphalt being cut
Change in sand or aggregate type and size can alter bond and diamond wear, a
lot.
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Clay Paver Cutting Instructions by Diamond Blademan
Clay paver blades perform best when used in a step cutting fashion. This is
a series of shallow cuts made to achieve the required depth of cut.A treadle
helps with this process.
Clay* paver blades often become blunt when plunge cutting the full paver
depth in one pass, with a small h.p. brick saw, also when too much water is
used. Use just enough water flow on both sides of the blade to ensure that
the water ejected from the cut is luke warm. Not cold or hot! This is
correct watering for this type of product.
*Use the step cutting method at about 80% of the saws power.
If the blade gets blunt or cuts slower than you are used to, you will need
to cut some hard aggregate concrete cobblestones with low water flow (almost
a slurry). Probably 30 cuts will be needed right through the cobblestone.
The blade will gradually free up and better speed will result. Just have a
little patience for 5 to 10 minutes, then follow the water rule and step
cutting (multi pass) principal to keep the blade sharper.
Clay paver blades require special bonds, especially for the very hard Monier
and NuBrik Paver types and cobblestone blades are unsuitable for more than a
few cuts.
Getting more life from your segmented diamond blade on slab saws.
Many small to medium sized contracting companies consider diamond blade
life to be a critical part of their daily operation and are keenly
interested in the total life of the diamond blade. Few however keep
accurate records, or have the luxury of large flat or near flat jobs
with consistent parameters and it is against this back ground that this
article is written.
Greater diamond blade life can result in higher profits provided
productivity is not compromised but wages are such a high percentage of
total costs that this side of the equation must be remembered. It may,
for example , be more profitable to accept shorter blade life for an
increase in cutting rates, especially if the contractor is busy. Some
would argue that if the contractor is less than busy he could better
spend his time
finding new customers, maintaining machinery etc. than worrying about
maximum blade life.
There are many variables that affect blade life and about which nothing
can be done.
These include the type and specification of the material to be cut, the
presence of steel and it's type, the location of the job, the length of
cuts, the flatness of the job.
There are also many variables that can be controlled and which
inevitably lead to considerable diamond blade cost savings. We will
examine some of the more important ones:
The most important variable to attend to is measurement of the actual
cuts made. A 1000 metre cut at an actual 30mm of depth (1181m at 25.4)is
a little different to a sloppy estimate of 950 metres at 25.4 mm. The
difference is that the blade has cut 231 metres at 25mm more than the
recorded cut. Sure there is only 4.6mm in it but it's nearly 20% more
material cut. The length underestimation is another 50 metres at 30mm.
All up 23.1% extra cutting or put it another way the blade appears to
have cut about 19% less than it actually cut. The message is clear.
Accurate measurement and invoicing can make a significant difference to
profit and it may well prevent wasted effort looking for other reasons
for shorter than expected life.
Blade shaft bearing wear and poor blade shaft diameter/blade bore
tolerance can radically reduce blade life through hammering diamond
teeth into an early demise.
Keeping diamond teeth in good cutting condition for as long as possible
is vital to longer tool life. This is easily accomplished by replacing
shaft bearings at regular intervals worn or not, and ensuring the blade
fit on the shaft is snug. Keeping the business end in good condition is
one thing but how that business end is presented to the material is
another. Concrete slab saws operate in hostile conditions where
abrasive slurry attack is the norm.
Usually the blade shaft bearings go first accompanied by front wheel
bearings transmission chain and sprocket wear and pointer pivot
innaccuracy. All these saw imperfections need to be attended to if
maximum blade life is to be obtained. A straight, hopefully long
pointer, with accurately aligned axles, identical sized paired wheel
diameters running on smooth bearings guided by an accurate and long
pointer will cut straighter and thence shorter and help to keep the
blade segment square and wearing evenly. At the stone factory large
bridge saws run on precision tracks with computer controls to achieve
consistent diamond tool costs.Out on the job we need to be thinking how
can we make the operation smooth and accurate.
Now that we have the machine largely sorted out it’s necessary to
consider the effects of blade shaft speed and water control.
Higher blade r.p.m. tends to make a blade act harder, and often last
longer, and when coupled with consistent correct blade speed from a well
tuned engine and driven by a smooth hydraulic drive system miracles can
be achieved. Water on the other hand is hard to make consistent with
supply problems on may sites. High water volume protects blades in
abrasive conditions such as cutting in the under coarse, whereas low
volumes increase heat, result in greater abrasion of the diamond
segments and steel blade core. Ideally the water plumbing system should
be able to supply at least 5 gallons(22.5 litres) of water a minute for
asphalt and green concrete cutting and be able to be adjusted for lower
volume for harder less abrasive materials. Blade saver switches and on
board pumps are often used to help with water supplies. Longer blade
life usually occurs when the right amount of water is used. A rule of
thumb is; The water ejected from the cut should be tepid not cold and
it should high volume for asphalt cutting and abrasive green concretes
with the caution that the blade needs some abrasion of the bond to
sharpen. It is a mistake to just put maximum water on the blade and hope
for the best because it may well result in a dull blade which is
difficult to use and unproductive. Water volume is an important
contributor to blade life. It can be surprising to find out how much
water gets nowhere near the cut. Often poor plumbing design effectively
sprays the water into high blade speed areas where it is blown off. A
good place to put water on the blade is at about 11 o clock. Plumbed
with large bore pipes and fittings and a good tap, water control can be
improved on many saws.
Mounting the blade to turn in the correct direction from new and
maintaining this direction at every blade mount, means that the tiny
bond supports for diamond teeth generated during cutting, will remain
intact and maximise potential blade life. Blade flanges too need to be
remembered because kept in a clean equal diameter condition they
contribute to keeping the blade vibrations to a minimum and thereby
increase potential blade life. Being held snugly on an accurate shaft by
A1 flanges ensures a happier blade but only if the steel core is flat
and tensioned correctly for the speed it will be cutting at. The better
the core the straighter the cut and the squarer the segment and the
longer the life.
Having talked a lot about the machine we need to look at the operator
and how it can effect blade life. In a perfect, world the saw will be
operated by an experienced operator keenly interested in achieving
longer blade life when it is appropriate. The operator needs to know
that blade life will be improved by cutting well within the saws
capabilities. Perhaps 75-80% of maximum possible rate of cut. On 4
cylinder engined saws a vacuum gauge is helpful in this regard because
it clearly shows when the blade is cutting freely and not being stressed
or pushed too hard. An operator who marks the job accurately with a
string line or other means and cuts to an accurate depth can make a
significant contribution to blade life.
In a nutshell keep the saw in first class mechanical order, operate it
with a skilled person, choose the right blade and use it only in the
right materials, paying attention to water control depth of cut and
measurement and follow the helpful hints the blade supplier has offered.
Remember any maintenance costs will soon be covered by greater diamond
blade life, happier customers, better image, higher morale, and
improved relations with your diamond blade supplier.
Blade wearing very fast
(see our article "Getting more life from your segmented diamond blade
on slab saws" above)
Are you cutting a very hard demanding material?
If so it will consume
diamond segments faster through greater diamond wear. Price or charge
the work accordingly.
Are you cutting a heavily reinforced concrete?
Steel increases diamond
blade wear.
Have you got a water supply problem?
Check the water volume to the
blade.It needs to be high for asphalt and luke warm on exit from the
cut when cutting for cured concretes.
Are the water pipes in good condition on both sides of the blade? are
they adequate in bore size? 1/2î (10mm approx.) is best , with a tap
for water control.
Are the blade shaft, blade shaft bearings, flanges all in A1 condition?
Check to see if the blade is absolutely round. Worn bearings can reduce
blade life by 50%!!
Blade will not cut very well
Is the blade the recommended specification for the material and saw
machine?
Every material and saw combination requires a closely matched blade for
good cost effective performance. An asphalt blade will not cut well in
cured concrete because the diamond segment sharpening action is retarded
with a hard asphalt bond. The diamonds donít protrude very well and so
the blade feels blunt. A softer bond is needed.
Are you using too much water? Self sharpening is created by abrasion in
the cutting action. If the water volume is too great this action is
slowed down and blades can get blunt. Aim for tepid water on exit of the
cut for harder materials.
Do you have enough power? A blade designed for high powered saws will
usually cut slowly on a low powered saw because it can have a harder
bond and more diamond to work into the material.
Segment loss
Is the steel core gold where the segment has come off? Poor joint
manufacture may have resulted in segment loss. If the blade got really
hot the brazed joints could have been melted is this possible? Look for
blued steel around the outer core area. If itís shiny steel in good
condition it could be a warranty claim situation check with us. It
happens on rare occasions.
Is the break jagged and characterised by lumps of matrix clinging to the
joint area? Thereís a good chance it was caused by something other than
a faulty joint. Perhaps the blade was jammed during cutting?
Is the steel core tapered underneath the remaining segments? If so the
abrasion in the cutting process has prematurely worn the core. Use a
higher volume of water and stay out of base course material. Charge more
if thatís what the customer wants you to do and call us about special
undercutting resistant designs.
Is the blade too hard for the material?
The diamond segment joints may have been fatigued by friction and duress
in a poor cutting situation caused by pounding, impact or twisting
especially with a blunt blade.
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