Three common knife compensation methods in CNC machining
There are three compensation in CNC machining: these three compensation can basically solve trajectory problems due to tool shapes in the process. The following is the application of three compensation in general machining programming.
1. Tool length compensation
1. The length of the tool length is a very important concept. We first specify the partial programming center of the part before you program, and then you can establish a workpiece programming coordinate system, and this coordinate system is just a workpiece coordinate system, and the zero point is generally on the workpiece. Length compensation is only related to the Z coordinate, it is not like the zero point in the X, Y plane, because the tool is positioned by the spindle tapered hole without changing, and the zero point of the Z coordinate is different. The length of each knife is different.
For example, we have to drill a hole with a 50mm hole, then the tapping is 45mm, with a drill bit with a length of 250 mm and a tap of a length of 350mm. First, take the drill bit 50mm, at this time, the machine has set the workpiece zero, when switching the silk cone, if the two knives start processing from the set zero, the tap is too long because the drill is too long, damaging the tool And workpiece. At this time, if the tool compensation is set, the length of the tap and the drill bit is compensated. After the machine is set, even if the length of the tap and the length of the drill bit are different, the zero Z coordinate is automatically to Z + (Or z) compensate for the length of the tap and guarantee the correctness of the machining zero.
2. Working tool length compensation uses tool length compensation to be implemented by performing G43 (G44) and H command, and we give a Z coordinate value so that tool moves to off work after compensation The surface distance is a place in z. Another command G49 is to cancel the G43 (G44) instruction, in fact, we do not have to use this instruction, because each tool has its own length compensation, when changing the knife, use the G43 (G44) h command to give your own knife long compensation The length compensation of the previous tool is automatically canceled.
3. Two ways of tool length compensation
1) use the actual length of the tool as a compensation of the knife length (recommended to use this method). Using the knife long as compensation is to use the length of the tool measurement tool, then input this value into the tool length compensation register as the knife length compensation. The reason why the tool length is used as the knife length is as follows:
First, the tool length is used as the knife long compensation, and it is possible Precision CNC Machining to avoid constantly modify the knife long bias in different workpieces. Such a tool is used in different workpieces without modifying the knife long bias. In this case, it can be filed according to a certain tool number rule, and each tool is filed, and the relevant parameters of each tool are written in a small sign, including the length, radius of the cutter, and the radius, in factMany large mechanical machining companies use this method for tool management of CNC machining equipment. This is used to tell the tools to tell the tool with the design of the tool management department, and even if the tool is reinstalled, even if the tool is reinstalled by the cutter capacity. The knife long value on the signage is compensated as a tool length without repeated measurement.
Second, the tool length is used as the knife length compensation, and the machine tool can be operated while machining, while the length measurement of other tools on the knife is not necessarily due to the tool operation time due to the knife on the machine. This makes it possible to give full play to the efficiency of the machining center. When the spindle moves to the programming Z coordinate point, it is the z coordinate value after the spindle coordinates plus (or subtract) the Tool length compensation.
2) Use the knife tip to the distance value of the program zero in the Z direction (positive and negative) as the compensation value. This method is suitable for use in only one person to operate without having enough time to use the length of the knife to measure the length of the tool. Doing so when you use a knife to process additional workpieces to re-perform the settings of the knife long compensation. When using this method, the compensation value is that the spindle moves from the machine Z coordinate zero to the tool tip moving distance when the workpiece program is zero, so this compensation value is always negative and large.
The concept of tool radius compensation is as used as the tool length compensation is substantially the same as the length of the tool is not considered. With tool radius compensation, we can do not consider too much diameter of too many tools when programming. The knife long compensation is suitable for all tools, while the tool radius compensation is generally only used for milling cutters. When the cutter is machined outside or inner contour, the tool radius is used to compensate, and only the tool length compensation is required when machining the workpiece with the end face milling cutter. Because tool radius compensation is a more difficult to understand and use an instruction, many people do not want to use it in programming. But once we understand and master it, use it to make our programming and processing will bring great convenience.
When the programmer is prepared to prepare a procedure for processing a workpiece with a milling cutter, the program is first to clarify the route taken by the tool center based on the shape of the workpiece and the radius of the tool. The cutter radius used at this time is just the radius value of the milling cutter. When the completion of the process, it is found that this milling cutter is not suitable for tools for other diameters. The programmer will re-calculate the tool center. The coordinate value of the route walking. This is not too big for a simple workpiece problem, and it is too difficult to re-calculate the complex mold. A workpiece processed processed and finishing, so that the coarse processing program is completed after completion of roughing. Because after roughing, the outer dimensions of the workpiece have changed, and then the finished tool center will be calculated.Coordinate values, the workload is bigger. At this time, if the tool radius compensation is used, these troubles are solved. We can ignore the tool radius and program it according to the workpiece, and then put the tool radius as a radius to the radius compensation register. Temporary replacement milling cutters, and crude processing, we only need to change the tool radius compensation value, you can control the size of the workpiece shape, and the program is not used as a little modification.
2. Use tool radius compensation using tool radius is performed by instructions G41, G42. There are two directions, that is, it is compensated along the left and right side of the blade in the vertical direction, which is in line with the left and right manual; G41 is left compensation; the left hand is fixed; G42 is right compensation, in line with the right hand, as shown in Figure 3 Indicated. Figure 3 Tool radius compensation uses the left and right ways to use G41 and G42 radius compensation, special attention should be taken particularly to make the tool movement direction and coordinates of the compensated effective tool. The tool radius compensation is important. If the path processed by improper tool is easy to make an error
Positive image tool length compensation and Like the radius compensation, the programmer can use the clamp bias without considering the length and size of the tool, the jig bias allows the programmer to use the clamp bias without considering the position of the workpiece clamp. When a machining center is a small workpiece, the tool is applied once, and the programmer does not need to consider the coordinate zero point when each workpiece is programmed, and only according to their respective programming zero points. Program, then use the clamp bias to the programming zero point on each of the machines. The jig offset is performed using the clamp bias commands G54 to G59. Another way is to set the coordinate system using the G92 command.
When a workpiece is completed, the next workpiece is processed using G92 to reset the new workpiece coordinate system. The above is three kinds of compensation commonly used in CNC machining. It gives us a great convenience, which can greatly improve work efficiency.