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Posted on Aug 27, 2020
CNC grinders are machine tools that use a rotating grinding wheel to remove material from a metal workpiece by cutting. Grinding machines are most often used for heavy-precision machining of details (parts). The surface quality that can be achieved is very high and grinding machines are almost always used as a finishing process in modern industry. In addition, thanks to the increased performance of grinding tools, grinding machines can now be used to achieve high material removal rates in production grinding.
From the very beginning of grinding, the researchers sought to perform this machining process in ever shorter time frames and at a satisfactory quality level. The most technologically advanced type of grinders today are ultramodern CNC grinders. CNC stands for "Computerized Numerical Control". This enables fully automatic part machining. Even with the most complex part geometries, such as crankshafts, camshafts, valves, ball bearings or drive shafts, reliable, fast and automated CNC machining is now standard.
In addition to the high machining capacity possible with today's CNC grinding machines during the actual grinding process, the loading and unloading of workpieces is often also fully automatic using automated loading devices. This is called an "unmanned operation" where occasional inspection of the CNC grinder or the grinding process is sufficient. For the processing process itself, the constant presence of an employee at the CNC grinder is no longer necessary.
Read More: CNC Grinders - Trends and Developments
Various mechanical and electronic systems are used in CNC grinding machines. Accordingly, these machines are complex in terms of configuration and control. Some components of CNC grinders are described in more detail in the following paragraphs.
The drive of a CNC grinding machine has to withstand various loads and operate efficiently. To maintain the required feed per revolution of the tool, as well as a constant grinding wheel speed - and therefore a constant cutting speed - especially when in contact with the workpiece (part), the drive must provide the necessary drive torque continuously and reliably. The required high drive torque and the speed of the grinding wheel require a high drive efficiency. This is mainly provided by electric motors and sometimes hydraulic or pneumatic drives. Despite the significant drop in performance, the drive motors or spindles on CNC grinding machines must be almost play-free to prevent axial and radial displacement of the drive shaft and thus the grinding wheel. If there is too much play in the drive, machining precision will deteriorate.
The grinding wheel is the actual tool of a CNC grinding machine. Grinding wheels are rotationally symmetrical tools whose abrasive grains are held together by a bond. The sharp edges of the abrasive grains remove the material with a cut when they come into contact with the part to be ground. Grinding wheels are very complex tools. Choosing the right grinding wheel is a key factor in the success of your grinding operation.
The control of all movements and machining processes in the CNC grinder is computer aided and fully automatic by two independent control systems, which are as follows:
• Computer numerical control (CNC)
The CNC system takes over all control tasks related to the machining of parts. These tasks include a sequence of machining steps or the dimensions of the finished part that must be achieved. Thanks to the use of CAM tools (Computer-Aided Manufacturing), The CNC can be delivered immediately with the design data needed to complete the machining of the part. Another possibility is to manually enter this data using an input mask directly on the CNC grinding machine. During grinding, the CNC system of the CNC grinding machine takes control of up to six different axes simultaneously.
• Programmable logic control (PLC)
The PLC system of the CNC grinding machine is responsible for all tasks related to peripheral control and monitoring. These include, for example, monitoring of coolant delivery and drive control. The PLC controller works in the background and is adapted to the machine by the manufacturer of CNC grinders.
The machine bed forms the lower end of the CNC machining area. Both driving and auxiliary devices are mounted here. In addition, this is where the chips and coolant are drained from the machine. The evacuation of chips and machining residues is important for the trouble-free operation of the CNC grinder. Bed flush nozzles are typically used to flush the residue along with the cooling lubricant from the machine.
Due to the nature of the grinding process, a lot of heat is generated. This damages the part. Grinding burn occurs when too much process energy is directed to the part. A reliable process cooling in the CNC grinder is therefore essential. This is achieved through the use of lubricating coolant nozzles which direct the coolant directly into the treatment zone. The cooling lubricant nozzles are fed with cooling lubricant through the feeding system from the central connection on the CNC grinding machine.
Automatic loading is necessary for the unmanned operation of the CNC grinder. This places the workpiece in the CNC grinder and removes it again after machining. As a gripper system, the load units can access the machining area of the CNC grinder from above. It is also possible to use industrial robots. Automated delivery of parts to the CNC grinder significantly reduces parts replacement time.
As grinding wheels are subject to abrasive wear during operation, it is necessary to restore the wheel geometry and cutting ability without replacing the grinding wheel. The bands are used for this. Dressers in these holders are generally harder than the grinding wheel, which enables them to remove material from the grinding wheel until the desired geometry and cutting properties are restored. The dressing equipment may be equipped with stationary dressing tools, such as dressing plates or rotating plates, such as profile or forming rolls. Dressing operations interrupt the grinding process and therefore take place in non-production time.
First of all, those parts are ground that have high requirements in terms of dimensional and geometric accuracy and surface quality.
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