Here you can find some information of our cutting training knowledge.
Do you need a company training? Write us to email@example.com
A103 (Aluminium Oxide / Corundum) or SC (Silicon Carbide)
It’s a set of abrasive (several granulometries), bakelitic resin, different charges, and air.
The abrasive must be hard but friable at the same time to brake during the cut highlighting the edges which allow the constant sharpening of the wheel.
Resin must incorporate all components leaving in the meantime the abrasive breaking (creating the wire) without completing breaking away.
The additional charges must ensure the resin catalyzation and the color homogeneity keeping temperature stable while cutting.
The wheel shape is the so-called “41” (flat).
From the outer crown, towards the center, the thickness tends to decrease.
This solution enables the wheel (which is elastic), to penetrate the material and, once inside, to leave more water enter, making cooling easier.
Moreover, more space inside the cut, reduces the normal vibrations. In this way the sample is protected from the risk of micro cracks and the crankshaft of the machine from the usual “redundancy effect” which would stress the bearings.
All wheels must have an identification encoding.
According to the Safety European Regulations, the wheel must be identifiable even when quite totally consumed.
Beyond the dimensions, the symbology, the producer, decoding the specifics of the wheel enable the operator to have a lot of information about the composition of the wheel.
An example of encoding could be AB80L5BF. Let’s decoding it:
AB identifies the typology of abrasive (A= white corundum, B= brown corundum)
80 identifies the prevailing granulometry of the abrasive (higher is the number, thinner is the abrasive)
L identifies the hardness of the wheel (on a scale from A to Z)
5 identifies the grade of “opening” of the wheel structure (porosity)
B identifies the kind of binder (Bakelite)
F identifies the possible presence of reinforcement inside the wheel (glass fiber)
Another information which is shown by the marking or labeling is the lot number of the production or the expiry date. It’s well-known that the expiry date of a wheel is 2 years (more or less).
To be honest, the operator must know that using the wheel after the expiry is not dangerous (if the wheel is used like regulated by the safety standards. Its life could just be shorter. The consumption will be higher because of to the aging of the resin inside due to the humidity or to the light. Resin gradually loses its capacity to incorporate all components.
Parameters set up
Most of times (and specially for cuts which require wheels with a diameter up to 350), the right electronic set up of t machine’s parameters, is crucial to optimize the cut.
An adequate parameter setting allows the operator to make a good cut with a satisfactory consumption of the wheel.
Another important point to take into consideration is the sample clamping.
To best way to obtain a good finishing avoiding possible micro-fractures, is creating as much as possible a “single unique body” between sample and working table.
That’s important because otherwise vibrations which propagate during the cut, if not absorbed by the system, could affect the final outcome.
The clamping way must take into account the geometry of the sample but also its inside tensions.
The cooling system is determinant to obtain a cool sample which can be handled right after the cut.
While cutting the right quantity of water must be administered in the intersection between sample and wheel. Right quantity, not only high pressure.
According to our experience the use of a multidirectional arms system of the water jets with two or more nozzles is preferable. This assures the presence of the coolant where necessary.
The coolant used is an emulsion of H2O and mineral oil. Considering that for a good cooling water would be enough, we suggest the addition of the lowest percentage possible of mineral oil because the Ph grade of the oil comes into conflict with the Ph of the resin bond, reducing its cohesive strength.
Unlike the common thought, the flange has an important role to obtain the best cutting performance.
We must clarify that he European Safety Legislation provides that the relation between the diameter of the flange and the one of the wheel must be 1:3 (wheel diam. 250 = flange about diam. 85).
Flange must be contoured to assure an effective fastening of the wheel.
Of course, using the flange, the useful cutting surface of the wheel is a little be reduced; but it makes possible the transfer of a higher tractive force to better and easily counteract the resistance of the material during the cut.
Moreover, using a flange 1:3 we give to the wheel more rigidity to better maintain the perpendicularity of the cut surface.
How to choose a wheel
First of all we have to start from the fact that the cutting wheel must be considered a “cutting device”, like a cutter for a machine tool or a drill bit (just think that it uses emulsified water to better remove without burnings). For this reason the operator must find the best solution to cut removing less material possible but keeping a right wear and tear according to the kind of samples to be cut.
What to check for the right choice:
- Kind of material to be cut:
Non-ferrous (Aluminium, brass, copper, composite materials)
- Dimensions and shape of the sample to be cut
- Hardening surface treatments, yes or not? If yes, what’s the thickness of the treated part and of the rest of the material?
- Hardness (in HRC or HV) of the sample. In case of surface treatment, what’s the hardness of the treated part and the one of the remaining material?
- Reason and typology of the check to be done after the cut
Reading during the several cut phases
While cutting, the machine and the wheel give us some information which can help the operator in understanding if he’s using an appropriate wheel and if the machine is working in the right way.
One of these is the “effort” of the machine while cutting. This data is not always easy to individuate. It’s expressed in Ampere and corresponds to the absorption of electric current of the engine during the cut (higher is the absorption, higher is the effort).
Another information which can be obtained looking the machine and the wheel working, is the vibration which can be felt also just laying the hand slightly on the machine cover. A lot of vibrations mean that the wheel is too hard, or that the clamping is not solid (the operator must always try to create one body between sample and working table).
A further signal is due to the kind of sparks that develop while cutting. They not only tell the operator which kind of material he’s cutting, but their intensity and color indicate if the wheel is removing the material in the right way or if the supply and direction of the water are correct.
Reading of the cut surface
After the cut, the aspect of the cut surface can give us a lot information about how the cutting system worked. In particular:
The color. The “white” surface highlights the absence of burnings.
The roughness of the surface. According to the final check to be done, it doesn’t have to be necessarily a mirror finishing (a mirror finishing is usually required only for a following analysis of the metallographic structure).
Burnings. If the surface shows burnings, the reading of their distribution on the sample will be important to understand how the binomial “machine / operator” worked.
Reading of the wheel after the cut
An aspect which is rarely kept into consideration (but which is important because gives further information about the quality of the cut), is the observation of the state of the wheel after the cut. In particular:
- The wear
- The outer ring
- The ridge profile of the wheel
- The grade of water impregnation