The durability of a cutting tool in metalworking refers to the time of continuous operation of the tool before failure, for various reasons.
When cutting with a ribbon cloth, its durability is determined based on the total number of sawn materials.
The measurement is indicated in m2, but more often you can see other indications.
This is the volume of sawn materials based on the length of the saw (m2/m in length).
Sometimes the durability of a tool is measured by the number of cuts it can make (pcs).
Most often, the following factors are the cause of a band saw failure:
- the unusability of the teeth over a length of 100 mm or more;
- damage to the ribbon web, which has led or may lead to its rupture;
- the location of the saw relative to the saw is not at right angles ("moving" it to the side) — this is due to tooth wear;
- the back of the canvas is dented or damaged.
The factors that can most affect the wear of the saw are the following:
Correct setting of cutting parameters: saw speed (m/min) and its productivity (cm2/min).
It should be taken into account that different ribbon webs have different types of settings based on the type of cloth being cut.
They are specified in the range from the minimum values of cutting speed and productivity, to the maximum allowable.
If you set lower values, the durability of the canvas increases, but the productivity decreases.
Also in the opposite direction: the higher the performance indicator, the greater the wear of the saw — therefore, the durability decreases.
As for the Nordex bimetallic saws used for sawing steel blanks 45 with a diameter of 100 mm, it is recommended to choose the modes for them:
- cutting speed V = 65-75 m/min;
- productivity Q = 41-67 cm2/min.
To increase the durability of the canvas, it is recommended to set the minimum parameters:
- V = 65 m/min;
- Q = 41 cm2/min.
At the same time, 1.9 minutes of time will be spent on the slice.
To increase efficiency, indicators will be required:
-V = 75 m/min;
-Q = 67 cm2/min.
Time costs 1.2 min.
The correct choice of the web, the corresponding parameters of the teeth, the material of the workpiece.The canvas should be selected based on the size and material of the workpiece.
An important requirement applies to the teeth of the web.
The pitch should correspond to the dimensions of the workpiece, and the shape should correspond to the brand of the material from which the workpiece is made.
With metals, during processing of which short chips appear, with brittle high-carbon, tool steels or cast iron, webs with a standard tooth having an angle of 0 degrees can be used.
As for viscous materials that produce longer chips, iron-containing materials, and their alloys, in this case it is allowed to use a cloth with a positive front angle of 8-11 degrees.
This is due to the fact that the processed materials are subject to the appearance of a riveting effect.
In the case of hard-to-process materials such as titanium, stainless steel, nickel alloys, it is recommended to install band saws with soldered carbide plates.
At the same time, the wear resistance and efficiency of the web increases by 3 to 5 times.
The shape, quality of the material and the shape of the workpieces to be processed.
In the process of processing hard-to-process metals with bimetallic saws, the wear of the web can increase several times.
It is possible that the tool may be damaged at the very beginning of processing.
To avoid such situations, it is recommended to use saws with carbide solders.
Workpieces in which there is a content of sand, shells, various kinds of seals and surface scale also reduce the wear resistance of the web.
If it is necessary to process a package of blanks, it is necessary to carefully check the reliability of their fixation in the machine.
In case of displacement of at least one element, the teeth will be discolored, which will inevitably lead to a decrease in the durability of the web to 60%.
Band saw equipment and its technical features.
High-performance machines with a rigid column structure are used in mass production.
On the scale of auxiliary or small production facilities, the use of double-column structures is allowed.
When band sawing, the width of the web is an important factor.
This has a positive effect on the efficiency of the sawing process, increasing the cutting capacity of the tool.
Technical condition of band sawing machines and their components.
The main nodes of the belt equipment are:
- Tension mechanism;
- Pulleys and bearings;
- A mechanism that ensures smooth lowering of the frame.
A tensiometer is used to measure the tension force of the web.
Depending on the width, the web tension will be 180-300 N/mm2.
This indicator helps to reduce the wear of the cutting tool.
The arrangement of the pulleys must exactly correspond to the plane of their location and there must be no runout.
It is necessary to prevent chips from entering the mechanism, and to clean it from contamination as far as possible.
The gap between the plates and the web must be adjusted strictly according to the data from the technical documentation of the machine.
It is necessary to ensure the rigidity of the saw frame attachment to the frame.
The frame should move smoothly.
Features of the use of coolant (coolant)
The coolant concentration must fully comply with the recommendations for processing a particular brand of material.
The coolant must be in the form of a water-soluble synthetic or semi-synthetic emulsion made on an oil basis.
At least twice a year, it is necessary to replace it and flush the supply system.
The supply of the emulsion to the treatment area should be abundant.
In the case of using low-quality coolant, the wear resistance of the web is reduced by 15-20%.
We recommend the use of a coolant in the form of a water-soluble semi-synthetic emulsion Nordex 1M in a container of 20 liters or a barrel of 185 kg.
>The quality of running-in of new ribbon webs
New saws are characterized by rapid failure due to chipping of the edges of the teeth, the top of which has a minimum radius.
To extend the service life, the saw is subjected to a so-called run-in.
This is a sawing process using understated modes.
The feed rate is reduced by 50%, the saw speed is up to 30%.
Calculations are made based on the recommended values for the workpiece used.
If the saw is bimetallic, then the running-in mode for it should be a cut-off volume within 300-500 cm2.
For saws with carbide solders, respectively 1 500 - 3 000 cm2.
After that, you can gradually increase the load to the recommended one.
As a result of multiple tests conducted by our specialists, it was revealed that, subject to all the above factors, the wear resistance of Nordex bimetallic saws with a width from 27 to 41 mm (the size is the most common) when used on rigid column–type machines for processing low-alloy and carbon steels, it is possible to count on the following indicators: 1.5-2.5 m2 the processed material per linear meter of the used canvas.
As an example, the following calculation can be performed:
It is based on the durability of the Nordex Hunter M51 canvas, which has the following dimensions 5140 x 34 x 1.1 – 2/3 tpi.
It is necessary to make an incision of a round billet with a diameter of 150-250 mm.
The theoretical billet is made of 35, 45, 40X steels.
Based on the data obtained, the durability of the web is calculated as follows:
(1.5–2.5) x 4.4 = 6.6 – 11.0 m2.
But that's all in theory.
The following formula is used to calculate the actual resistance:
C = (S x n) / 10000, (m2),
S is the cross–sectional area of the workpiece, cm2;
n is the number of blanks processed with a saw, pcs.
In the case of work using blanks made of tool, stainless or alloy steel, data on the theoretical wear resistance of the canvases is estimated at 0.5–1.0 m2 of the processed material per 1 linear meter of the canvas.
In the operation of non-rigid or cheap machines, all the parameters specified above should be underestimated by 25-50%.
When alloyed and carbonaceous materials are cut using carbide sheets, not only their wear resistance, but also their productivity increase 2-3 times.
This is important because the cost of carbide sheets is 3-4 times higher than bimetallic ones.
In the process of processing nickel and titanium, corrosion-resistant and heat-resistant alloys, the theoretical wear resistance is determined by 0.2-0.5 m2 of the processed material per one meter of the linear web.
03 Martha 2021
