Diamond tipped saws | Carbide tipped saws | rock saws/rock saw attachments
grinders/twin-head grinders | stump grinders
Diamond tipped saws | Carbide tipped saws | rock saws/rock saw attachments
grinders/twin-head grinders | stump grinders
Knowledge Corner is where we discuss anything to do with cutting rocks. Have a look at our existing articles to see if there is something of interest to you.
If we haven't told you what you need to know, contact us with your question and we will do our best to answer it.
The very basics of cutting rocks
How do I choose between carbide and diamond saw?
Do you have a saw that is optimised for use on excavators sizes from 2 to 16 tonnes?
Diamond saws often seem to stall easily, they seem to have insufficient torque, why?
the teeth in my saw are wearing really quickly, why?
How do I tell if a problem is due to abrasiveness or due to the hardness of the rock?
In most cases, unfortunately, there isn't. There is a broad selection guide presented in the Products section, but it is no more than just a guide. While it is safe to say that carbide saws are unsuitable for materials above 40 MPa and diamond saws are unsuitable for compressive strengths below 15 MPa, it is the region in between, which is encountered the most, where it is the hardest to decide. The best strategy is to insist on trialing both before you commit to anything.
No, nobody has and those who claim they do are misleading you.
There are people who claim their saw (an equivalent to our D3) is suitable for excavators ranging from 2-16 t. Our D3 saw can also be made to work with all excavators in this range, but it does not work at its full potential across this whole range. Just like there is not one hammer size that fits all, or just like there is not one excavator size suited for all jobs (!), various size saws are only optimised to work with a limited excavator sizes.
This why we do not subcribe to this overstated advertising and have rather invested heavily into the development of wide product range
See our Rough Guide to Diamond Saw selection
The brief answer is: because diamond "cutting" is grinding and not cutting. Speed is more important than torque. Push lightly and maintain speed is the trick.
The more detailed answer: Too long to list here, but we'll give it anyway :-)
What removes material is the work the cutting tool puts in it. The productivity, or cutting rate, is the measure of material removed per unit of time, i.e. work per unit of time, i.e. power.
In theory, you could calculate the rate of work (power) delivered to the rock by multiplying the blade speed by the force with which the blade rubs against the rock times the energy transfer efficiency.
So much for a nice and simple theory!
In reality, the situation is more complicated than such a simple minded formula.
Firstly, the there is no simple way to evaluate the energy transfer efficiency. That varies wildly with the cutting method, i.e. carbide or diamond, with the mechanical properties of the rock, i.e. hardness, coherence, mineral composition etc.
Secondly, the saw does not generate power, it merely utilises the power supplied by the excavator hydraulic system and there are some very practical limitations on the actual make-up of that power.
For example let's take a 25kW pump of a typical 8 tonner. This pump will deliver the ideal 25kW with a combination of 100 L/min and 150 bar. Now, the flow determines the blade speed and the pressure governs the rubbing force or torque. If the operator pushes harder on the rock, the blade speed may rapidly drop to half of its value, but to maintain the same power, or productivity, the torque, or pressure, would need to double to compensate. The relief valve in the excavator will not allow that though. Moreover, there is another complicating factor coming to play: the energy transfer efficiency. This efficiency increases with the speed of blade. It is like sharpening a knife on a grinding wheel: one can push very hard on the blade, but if the wheel does not spin fast enough, nothing much will happen.
Is lowering the pressure to a very low value the answer to great productivity then? Unfortunately not. In our example, if we loosen the pressure on the blade to require only 50 bar, ie. one third we would need 3x higher flow to keep the power constant. Alas, the excavator pump will not give us 300 L/min. And a good thing too as we would blow the motor to pieces if it did!
The secret is knowing the right pressure-flow combination which gives the highest productivity. This combination vary from one excavator to another and for larger machines is really difficult to maintain manually.
Echidna's Cutting Optimiser is a real solution that offers productivities more than a double of a manual operation.
For morerRefer to an article: "speed or torque" in the Knowledge Corner section.
| Your supplier either has no idea how those segments are made or knows very well that this is a nonsense, but hasn't got the know-how to achieve dual direction cutting or both. Just ask him to repair a blade for you, to braze a new segment on and watch him how he pulls a carefully marked segment out of a box so that he places it in the right direction. Does he? :-) Of course not! The segments are not made in any such way. He will pull them out from a box, where they float freely and even though you will find some arrow markings on the segments you will find there is no way of knowing which way they should be attached. Because there is no need to know. The picture below is a photograph of a segment |  |
| The arrows you see are at both sides of the segment, which way do they go? either way, the orientation does not matter! | |
| The truth of the matter is that after a prolonged period of cutting the diamond grains and the bonding matrix between them wear and shape themselves into a micro texture suited for a particular direction of cutting. All you need is to reverse the direction and after a very short while they will rearrange themselves into the new direction. | |
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This problem is relevant to both carbide tipped and diamond tipped blades.
The answer to the question varies from case to case and dependents on the mechanical properties of the rock, the saw tooth material and often also on the operator's skill and common sense. Taking operator out of the equation for the time being, it is important to first decide if the wear is due to abrasiveness or hardness of the rock. In carbide saws, the problem is very often in wrong placement of the cutting picks, if those are placed correctly and you still experience excessive wear, try another teeth material. Remember, hardness of the rock and hardness of the minerals which make up the rock are two different things! Eg, 25 Mpa rock, is not very hard, but if it is made up from coarse grains of predominantly quartz, it will wear out your cutting tool really quickly. Try different grades of carbide, in diamond blades try different grade of diamond composite. |
If the cutting tool gets gradually and uniformly smaller, with no pronounced scratches on the surface it is the case of abrasive wear. If the tool surface shows deep scratches, or chips and dents, then the problem is the rock hard for the tool. In both cases the solution lies the choice of suitable tool material.
As soon as the steel body of the tool gets in contact with the rock, the tool should be changed. On diamond blades, this is simple, the wear is usually uniform and all teeth wear at the same rate. On carbide blades this may not necessarily be the case. Always inspect all picks and as soon as the body of any pick is beginning to wear, change the pick. It is a good idea to keep track of what picks get changed so that any picks that have the tendency to wear faster can possibly be repositioned into a better cutting angle.
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Each solid material is held together by a combination of many different forces and it takes energy to overcome those forces. Energy is measured in Joules ("jools") and rock mass (weight) in kilograms. A kilogram of each material needs certain number of Joules to break it apart. In general, the harder the material, the more energy one needs to break it up. But that is not enough. One can deliver certain amount of energy to the rock in millions of tiny taps, or he can deliver the same amount of energy in one split-of-a-second mighty blow. And he has more chances in the second instance. Sothe speed or the rate at which the energy is delivered is important. The rate of energy delivered per unit of time is power. Thus the rate at which rock (or other material) is broken up during cutting or grinding is proportional to the power delivered by the cutting tool. The more power the machine transfers to the material, the faster it will be broken up. |
We've touched upon the next important point: it doesn't matter much how much power the machine has, rather it is important how much of its power it transfers to the rock.
That transfer is done via the cutting tool. If the cutting tool were an ice disc, it would just slip happily along the surface, gradually melt away and very little energy or power would be transferred to the rock. The tool must be such that it doesn't just slip, it engages with the material it cuts. It can do it by many different ways. It may just run along the surface and heat it by friction so that the material melts away. It may dig into the material and rip it apart. If it is impossible to get between the grains, it may remove material by continuously scratching the surface and removing material in millions of tiny scratches, like it is the case of grinding (in metal grinding it is the combination of this scratching and surface melting). To remove the material efficiently this way, it is obvious one needs speed. |
In conclusion it is important to realise that to design a good rock saw, grinder or crusher one needs to first understand what is happening on the microscopic level, how to break the various bonding forces in the material, which one to attack, to understand and design the interaction between the cutting tool and the rock. Only after this comes the design of the machine, which the operator sees.
Understanding these minute details and having decades of experience in building reliable machinery in many fields is the key to the success of Echidna rock tools. |
| For cutting relatively soft materials, the carbide saw is the best choice. For harder materials, perhaps a diamond saw is the way to go. Here's why.....
It is necessary to start with basic principles here. Firstly, the commonly used nomenclature is not exactly correct. While the carbide really is a saw, the diamond is rather a grinder. The tips of the carbide picks, or tusks, penetrate between the grains of the cut material and rip whole grains or little chunks of material out. .The "tips" of the diamond blade have no sharp tips to speak of. They are made of flat diamond filled abrasive segments, that grind away the material under attack. |
The carbide needs brute force or torque and limited speed, the diamond needs speed and not too much pressure. If the material is sufficiently soft compared to the carbide tipped pick, the energy transfer is more efficiently accomplished by ripping it by the carbide tusks even when a lot of energy is wasted on excessively wide cut. |
If the material is so hard that point of the carbide tip cannot engage and rip the grains out, then the best way is to grind away the grains instead of plucking them out. For this grinding action, diamond based abrasive tips of a "diamond saw" are the way to go.
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| They say, there are horses for courses. What if the course is unknown? Get an unknown horse?
Some get an excavator, others opt for a tractor with a digging attachment. It depends on the proportion of jobs the tool is meant for. |
There are machines on the market that, according to their manufacturers, can be fitted with diamond blade or carbide blade or, as per one manufacturer, even a twin head grinder!
While we do not dispute the fact that they may be able to be fitted with all these cutting tools, there is little doubt that the performance of at least the majority of them is severely compromised. |
We understand that there is a place for universal machines, but at Echidna, we put emphasis on productivity and hence on dedicated machines for a job.
The speed requirements on the blade of a carbide saw and on the drum of a twin head cutter are so different that it makes no sense to us to make them interchangeable. The time and effort one needs for the change after a few months of use makes such "versatility" even less attractive. |
| As we saw above, the most important parameter in diamond cutting is speed of the blade. Ideally, the speed of the tool as it scrapes the rock should be 40-50m/s for efficient cutting.
The maximum power that is available is, theoretically, the power of the diesel engine in the excavator. In reality, it is much less, depending of the efficiency of the power transfer system all the way from the engine to the rock. A 24t excavator typically has about 140KW engine and let's assume we have a 2.5m blade on our saw. If the efficiency of the system right up to the blade is 80% (a very optimistic scenario!), than the blade power is ca 120kW. This power is the product of speed and torque. This means that the torque we end up with for a properly designed system is: T = P x D / 100 = 3 KNm |
In all truth, when all the real world constraints are taken in consideration, we are unlikely to get more than some 2.4 KNm. This torque, however, is very difficult to maintain on the edge of a 2.5m wheel from a 24t excavator. Excavators are not made for fine control. And so they keep stalling the blade - an apparent lack of torque.
The only way most manufacturers see to improve the situation is to increase the torque and that is only possible by sacrificing cutting speed, i.e. cutting productivity. At Echidna, we attack this problem in three different ways: 1. The simplest and cheapest: decrease the depth of cut. If you need to cut 1m deep do it in 10 incremental cuts instead of trying to cut the full depth. Just like they do in professional factory outlets.
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The blade will not stall and your productivity will go up dramatically. On top of that you will get a better quality cut and less wear on your blade.
2. Install a pressure gauge connected to the motor feed line in the operators cabin so that he can maintain constant pressure on the motor. 3. Install Echidna saw driver. An automated driver unit that takes over from the operator and controls the movement of the dipper arm, letting the operator only to adjust the position of the boom during cutting. The cutting productivity with this unit goes up tremendously - as much as 2 to 3 times! Contact us for price and availability. |
