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Design and development MPS
Digital Labs, India
( This article appeared in the print edition of Litos in September,98).
Not so long ago it used to be a straightforward choice when deciding on the cutting system for one´s factory, but with rapid and constant technological advances today one cannot use the cost and other assumptions of before to decide which one is the most cost effective or recommendable. LITOS, in trying to clear the debate somewhat, asked three manufacturers / representatives of different cutting systems to answer the following question -
IN CHOOSING BETWEEN THE GANGSAW, THE BLOCKCUTTER AND THE MULTI-WIRE MACHINE IN WHAT CONDITIONS AND WHY YOU WOULD RECOMMEND YOUR SYSTEM?
And we gave the three complete liberty to respond the way they wanted. Below we publish the replies. Hopefully you are better informed.
The company PEDRINI answers this question.
"The proper technology for each range of products " should be the winning philosophy in the present stage of the world market, where the margin for mistakes is very limited. The era in which anybody had the possibility to invest in a single technology to produce everything is now over. Any investor, newcomer or not, in the natural granite products has to know that an appropriate technology must be used in each type of products he decides to manufacture. Otherwise, if a wrong and uneconomical technology is used, he will be out of the market unless he decides to subsidise this production thus loosing the money earned elsewhere.
Another consideration to be made by the investor, newcomer or not, is that his investment return is assured only in case a consolidated technology is utilised. As of now we must acknowledge that for mass production only two granite technologies are consolidated : block cutters and gangsaws. The diamond wire cutting technology today is still confined to auxiliary utilisation or to small quantities of very special products.
The multi-disk block cutting system is recommended in all those cases where a serial massive production is needed and the products to be manufactured have one of the dimensions not exceeding 650 mm.
The following elements for the building industry are included within this range :
Why in such cases is the multi-disk block technology to be recommended ?
The answer is very simple: "Because it is the most economical technology!"
The most important cost parameters to consider for the calculation of the cutting costs are:
If the realistic and actual values are taken into account for each one of the above indicated cost parameters, we will find that for the smaller products in some cases the multi-disk cutting costs are up to 60% lower than the gangsaw cutting costs and only in the cases of the biggest products for block cutters ( 600 and 650 mm wide products) the multi-disk and the gangsaw cutting costs are similar.
Furthermore, the multi-disks block cutting technology produces strips where two dimensions (thickness and width) are defined, whereas the gang sawing technology delivers slabs where only the thickness is merely defined. This makes the elements coming from multi-disks blocks to require lower costs for the eventual subsequent finishing operations.
In several European markets such as Spain, Germany, Italy there is a considerable demand for thick tiles for the paving of roads and squares. Due to economical factors this kind of production is more and more assigned to multi-disk block cutters.
Today, thanks to the already consolidated Pedrini Modular Cutting Center it is possible to obtain a very high productivity and remarkable cost reduction when working very thick products, not only the classic Modulgranite.
In fact the Pedrini Cutting Center covers around 1450 mm block width for each cutting cycle and permits to mount up to 80 vertical disks when cutting 11 mm thick strips and, on the opposite limit, up to 25 vertical disks when cutting 50 mm thick strips.
As a conclusion, since the very large sized products, the cut to size and the big slabs cannot be obtained by the block cutters, a modern granite processing factory should reasonably be equipped with both the technologies: multi-disk block cutting and gang sawing. However such modern granite processing factory should wisely address to the block cutters every product that can be cut by such machine.
The motto should be "Use the multi-disk block cutters as much as you can ".
The company COFIPLAST answers this question.
Initially the answer might seem difficult but in reality it is not, at least for us, since we belong to Wires Engineering and we produce the multi-wire machine Falcon 600.
Some advantages to be had from the new technology applied to the multi-wire machine are evident, others are not so clear but equally important. We will now examine them.
The multi-wire machine can cut marble, granite, serpentine and any other type of rock. Therefore, one type of machine can do the same work where the gangsaws and block cutters need at least two distinct machines. Let us begin with the gangsaws.
The traditional gangsaws for the cutting of granite, even if are increasingly wider and with more applied technology, still work with a quite primitive system, i.e. with a steel blade that with the help of grit cuts slabs with a speed of 3,4 or 5 cm per hour. This when the blades are inside the block and the machine can "push" them. Moreover, the blocks should necessarily be of big dimensions if the productive capacity of the gangsaw is not to be drastically reduced. The multi-wire machine cuts with a medium velocity of 30 to 40 cm per hour with an average hourly production of 10-12 square metres of slabs. The dimensions of the blocks and their form are not restrictions when referring to the productive capacity of the machine. The traditional gangsaws should, because of how they are conceived, cut the whole block obliging the user to "guess" the thickness of the slabs of which there is yet no order and which should be stored in open air with the hope that the next order is of adequate thickness. The multi-wire machine can, without any problems of reduced production, can cut a block only partially, i.e. it allows cutting the slabs for which there is already an order, thus avoiding the above mentioned risks.
The traditional gangsaws create a volume of special waste ( calcium, grit, rest of blades) that can be quantified in at least 6 kg per square meter of cut. This means that for 50000 square metres cut, the special wastes will be more than 300,000 kilograms. The multi-wire machine only has wear out of diamond wire which is of the order of 0,010 kg per square meter. Let us leave to others the calculation of the cost of eliminating the special wastes.
The traditional gangsaw requires several hours of preparation work of the blades holder and, moreover, several hours for the washing of machines and of the slabs themselves.
In the multi-wire machine the change of thickness is done in a few minutes. If the cutting thickness have not changed, the machine is immediately ready to begin a new cut. The substitution of a change of diamond wire is estimated every 3 to 4 months with work cycles of 24 hours a day. The slabs do not need to be cleaned at high pressure and being cut with diamond have a smoother surface that makes the polishing easier in terms of time and money.
The cementing and other work of the multi-wire machine are less as compared to a slab which, with its alternative movement, produces strong forces. In practice one can affirm that the costs of cementing a multi-wire machine are less than one fifth of the cost of cementing a gangsaw. Moreover, take into account that the multi-wire does not need a shed and can even be installed in the quarry.
We think a modern gangsaw can produce in a month 3000 to 4000 square metres of slabs of 2 cm thickness. The multi-wire can produce 5000 to 6000 square metres of slabs cut at any thickness between 1 to 5 cm.
Here some might think : " This is where I want to see you ! " But no, our wire of 8 mm working on the Falcon 600 gives an output that is such that the costs are competitive without any doubt. Everyone does his own numbers, therefore, we will not speak of the costs of sawing of a slab. Now, the gangsaw has fixed costs that affect the cutting costs whether the blocks are small or irregular and if the slabs have thickness greater than 2 cm. The multi-wire machine maintains the cutting costs constant independently of whether the thickness is of 1,2,3,4 or 5 cm and this is so because the fixed costs are minimum and approximately 80% of the cutting costs are determined by the diamond wire. Therefore, the change of thickness does not increase the cost of production. We can say that our cutting costs are more or less similar to that of the gangsaw for slabs of 1 to 2 cm thickness while in the multi-wire machine the cutting costs are less for thickness of 3,4 or 5 cm.
Who would we recommend the use of the multi-wire machine ? To all those who desire to produce slabs and thick pieces at competitive costs without limitations of the type of material or the dimension of the blocks. A traditional sawing installation can use the multi-wire machine to satisfy all the demands related to the speed of delivery which is increasingly a fundamental requisite in production. The cutting of thick pieces with the multi-wire, apart from being economical allows the gangsaws to work with small thickness without reducing production capacity.
The comparison of the multi-wire with the block cutter is difficult for a simple reason : the first produces slabs while the block cutter produces strips. Therefore it is trying to compare two different products. It is obvious that the slab allows all kind of elaboration and successive production while the block cutter allows for the production of small formats. We think that the substantial difference is in favour of the multi-wire machine. In practice, the block cutters can cut up to a maximum of 40 cm and it is known that the market is increasingly requiring bigger formats. We think the production costs with the block cutter are less for formats of 30 x 30 cm but with the 40 x 40 cm the multi-wire is competitive. Moreover, the multi-wire machine can produce the much in demand 60 x 60 cm apart from all bigger sizes.
The cutting of 1 cm is not a problem for the multi-wire which, let us not forget, maintains all its production capacity and versatility. Who do we recommend the multi-wire machine ? To all those who desire to produce slabs and panels of big format and have the possibility of also producing slabs of any size and thickness with any material
The company VIME S.L. answers this question.
When LITOS asked me to present the arguments for buying a gang saw using steel blades and not a block cutter or a multi -wire machine for producing semi- elaborated granite, I first began to look for economic and technical data of the different machines so as to present a numerical comparison which, undoubtedly, would have led to contrasting data that surely would not clarify the question.
On the other hand, it would not be ethical to recommend to anyone to use pliers to take out a thorn from a finger, or surgical pincers to hold tight a nut or a knife for tightening a screw, since each tool or machine has been thought out, designed and contained for a series of specific tasks; each type of production should be realised with the adequate machine and there will always be area limits where the advantages and inconvenience of use of one or the other tool become diffuse making the choice difficult, the simple use of common sense ( which, on the other hand is the least common of the senses ) will indicate to us the machine to choose for each kind of job.
Three examples can highlight what has been said above:
Let us imagine that the production to be obtained are tiles of 30 x 30 cm and 1 cm thickness, if we use for this the steel blades gang saw or a wire machine the first problem we come across will be the manipulation and polishing of the granite slabs of 1 cm of thickness achieved with these two machines with dimensions greater than 2.5 m length and 1 m height.
Therefore, if the differences in quantity and production costs of these machines as against a multi-disk are not relevant factors it is evident that it would be the most appropriate machine for achieving 30 cm strips with 2 to 3 metres length of which we can later obtain our calibrated tiles of 30 x 30 cm and 1 cm thickness.
In the second case our objective is a piece of 2 m by 1 m with a thickness of 10 to 12 cm which in some cases will have a curved surface, in summary, a piece for use in funerary art.
If we wish to produce this piece with a gang saw and this were to have a 350 cm width we would get approximately 30 of them per sawing with electric consumption and depreciation similar to that when the machine produces 120 slabs of 2 cm thickness apart from taking more or less the same time, so it is logical to think that the gang saw is not the most appropriate for this end.
To produce the same piece with disk we would need to have a cutter with disk of 3 m diameter cutting in phases. These machines are single disks so as to make its refrigeration easier and normally its production capacity is not big except in granites of low hardness, on the other hand the big diameter of the disk makes necessary having high segments and this is reflected in the consumption of diamond and at the same time in losses in the relation square metre / cubic metre.
On the other hand with a wire machine the width of the cut does not change with its height and the high cost of diamond per square metre is diluted by the high value of raw material due to the big thickness of the piece. The production capacity is acceptable and the versatility of the machine allows for changing the thickness in each piece and this way disguising within the high thickness the lack of plurality in the cost of this type of machinery which, of course, would be impossible to hide in a 2 or 3 cm thick slab.
Moreover, with a wire one can cut curves that eliminate work later in these types of production.
Last, our objective is to obtain granite pieces with variable sizes ranging from 40 cm to 2 metre maximum and with thickness of 2 to 8 cm for floors, slabs, interior decoration, bathrooms and kitchen tops.
We have already seen that in increasing the size of cutting depth the disk does not create problems of refrigeration and obliges us to increase the thickness with which the cost of diamond and the relation m2 / m3 is hurt , maintaining the same thickness also being a problem and , logically, this is more evident when producing slabs of 2 to 3 cm thickness.
In the case of wire the lack of flatness of cut in these sizes means greater problems than in the previous cases since a deviation of 2 mm every 10 cm is not comparable to a deviation of 2 mm of 2 mm every 2 cm, around 2% can be admitted but in no case a deviation of 10%.
Moreover the cost per square metre of cut begins to be relevant when the raw material is reduced.
The gang saw in this case is very much at home.
A machine of this type of the latest generation can obtain in less than two days 150 slabs of 2 cm thickness of more than 2 m height and more than 3 m length for less than 800,000 pesetas ( approximately US$ 5300). This includes steel blades, grit, electric energy, calcium, water, maintenance, labour, depreciation of machine, etc. so that evidently for big production runs of materials with variable sizes and medium thickness, as of today, the gang saw for cutting granite is the unquestionable machine.
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