In machining, cutting tools are the basic technological equipment for cutting. They are in direct contact with the parts to be machined. Different tools can process different parts' structures and surfaces, which play a vital role in machining. They can be called "industrial teeth". As consumables, the tool itself has a certain life span. Different materials and specifications of tools have different life spans; For mass production, tool consumption also accounts for an important part of the processing cost. Therefore, it is a common problem for the manufacturing industry to improve tool life, control tool consumption, reduce processing costs and improve production efficiency.
Existing technology
Tool dressing is a way to improve tool life. However, the traditional manual equipment (such as manual grinder Fig. 1) can not meet the user's requirements in terms of precision, efficiency, reliability and safety. At the same time, enterprises also need to train professional tool grinding personnel, which increases part of the human cost.
technological development
Aiming at the above problems and combining the existing resources of the enterprise, we have developed a set of technical solutions that use CNC machining centers to achieve tool grinding automation:
First of all, because the tool materials are generally hard, only grinding can be used to change its shape. Grinding wheel abrasive grains of different materials are suitable for grinding tools of different materials, and the size of abrasive grains required for different parts of the tool is also different, to ensure the best combination of edge protection and machining efficiency. Therefore, the first problem to be solved by using CNC machining center for tool dressing is the type and clamping mode of grinding wheel; Considering the low price of alumina grinding wheel, and easy to repair into different shapes for grinding complex tools, however, the tools that can be grinded are too simple (can be used to repair HSS (high speed steel) tools), and it is difficult to clamp and replace them frequently, so diamond grinding wheels that can repair more tools (HSS (high speed steel), PM-HSS (metallurgical powder high speed steel) and HM (cemented carbide steel) tools) are used. Lock the diamond grinding wheel onto the handle of the milling cutter with a special nut, so that the diamond grinding wheel can be clamped onto the cutter head of the CNC machining center and the spindle of the machine table
In addition, it is necessary to consider the clamping and positioning method of the grinding tool: use the telescopic cylinder to cooperate with the self-made elastic rigid jacket to clamp the tool, and fix the tool clamp on the four axis platform (as shown in Figure 2), so as to ensure the parallelism and straightness of the four axes erected, which can ensure the parallelism and straightness of the grinding tool, and at the same time, enable the grinding tool to move in the X axis, Y axis and a axis directions. With the movement of the machine table spindle in the Z axis direction, the tool edge can be grinded at different angles.
Moreover, the most critical technology of using CNC machining center to repair mold tools lies in the use of probes. Using high-precision probes with the detection program input by the machining center can confirm the tool grinding zero point, the tool grinding position, and the number of tool edges, and feed back the measurement results of these variables to the CNC machining center's numerical control system to input the tool grinding program prepared in advance for tool grinding.
Of course, in order to realize the automation of tool grinding, we also need to add an automated assembly line (Figure 6): through self design, we can get the material tray for placing the tool (Figure 4), so that the manipulator can accurately position the tool, thus realizing the loading and unloading of the tool. With the CNC processing center, as well as the assembly line device and the final high-precision detection device (Figure 5), we can achieve the complete automation of tool grinding.
The specific machining process of CNC machining center tool grinding can take the grinding of end milling cutter as an example: for the worn end milling cutter, the worn blade must be cut off and reground to obtain the required blade. Of course, this needs to ensure the effective blade length of the cutter. If it cannot be guaranteed, the end milling cutter cannot be reground. For CNC machining centers, we can preset the maximum cutting length and the cutting amount each time. Each time the probe is cut out, it will be detected once, and the cutting amount will be accumulated once; If it is detected that the blade part is still missing, it shall be cut again, and other parts of the tool can be further grinded until the blade is complete; If the cutting amount exceeds the maximum cutting length, the tool cannot be reground. The next step is to grind the chip breaking groove, then grind out the back angle of the tool, and finally grind out the bottom edge of the tool. These can be achieved by using the matching movement between X axis, Y axis, Z axis and a axis through program design in advance.