Tool setting is the main operation and important skill in CNC machining. Under certain conditions, the accuracy of tool setting can determine the machining accuracy of parts. At the same time, tool setting efficiency also directly affects CNC machining efficiency. It is not enough to just know the tool setting methods. You must also know the various tool setting methods of the CNC system and how to call these methods in the processing program. At the same time, you must know the advantages, disadvantages, and usage conditions of various tool setting methods.
1. Principle of knife setting
The purpose of tool setting is to establish the workpiece coordinate system. Intuitively speaking, tool setting is to establish the position of the workpiece in the machine tool workbench. In fact, it is to find the coordinates of the tool setting point in the machine tool coordinate system.
For CNC lathes, the tool setting point must first be selected before processing. The tool setting point refers to the starting point of the tool movement relative to the workpiece when the CNC machine tool is used to process the workpiece. The tool setting point can be set on the workpiece (such as the design datum or positioning datum on the workpiece), or it can be set on the fixture or machine tool. If it is set on a certain point on the fixture or machine tool, the point must be consistent with the positioning datum of the workpiece. Maintain dimensional relationships with a certain degree of accuracy.
When setting the tool, the tool position point should coincide with the tool setting point. The so-called tool position point refers to the positioning reference point of the tool. For turning tools, the tool position point is the tool tip. The purpose of tool setting is to determine the absolute coordinate value of the tool setting point (or workpiece origin) in the machine tool coordinate system and measure the tool position deviation value of the tool. The accuracy of tool point alignment directly affects the machining accuracy.
When actually processing the workpiece, using one tool generally cannot meet the processing requirements of the workpiece, and multiple tools are usually used for processing. When using multiple turning tools for processing, when the tool change position remains unchanged, the geometric position of the tool tip point will be different after tool change, which requires different tools to be able to process at different starting positions when starting processing. Ensure that the program runs normally.
Xinfa CNC tools have the characteristics of good quality and low price. For details, please visit:
CNC Tools Manufacturers – China CNC Tools Factory & Suppliers (xinfatools.com)
In order to solve this problem, the machine tool CNC system is equipped with a tool geometric position compensation function. Using the tool geometric position compensation function, you only need to measure the position deviation of each tool relative to a pre-selected reference tool in advance and input it into the CNC system. Specify the group number in the tool parameter correction column and use the T command in the machining program to automatically compensate for the tool position deviation in the tool path. The measurement of tool position deviation also needs to be achieved through tool setting operations.
2. Knife setting method
In CNC machining, the basic methods of tool setting include trial cutting method, tool setting instrument setting and automatic tool setting. This article takes CNC milling machines as an example to introduce several commonly used tool setting methods.
1. Trial cutting and knife setting method
This method is simple and convenient, but it will leave cutting marks on the surface of the workpiece and has low tool setting accuracy. Taking the tool setting point (which coincides with the origin of the workpiece coordinate system) at the center of the workpiece surface as an example, the bilateral tool setting method is used.
(1) Tool setting in x and y direction.
① Install the workpiece on the workbench through the clamp. When clamping, there should be space for tool setting on the four sides of the workpiece.
② Start the spindle to rotate at medium speed, quickly move the worktable and spindle, let the tool quickly move to a position with a certain safe distance close to the left side of the workpiece, and then reduce the speed and move close to the left side of the workpiece.
③ When approaching the workpiece, use fine-tuning operation (usually 0.01mm) to get closer, and let the tool slowly approach the left side of the workpiece so that the tool just touches the left side surface of the workpiece (observe, listen to the cutting sound, look at the cutting marks, and look at the chips, as long as If a situation occurs, which means the tool contacts the workpiece), then retreat 0.01mm. Write down the coordinate value displayed in the machine tool coordinate system at this time, such as -240.500.
④Retract the tool in the positive z direction to above the surface of the workpiece. Use the same method to approach the right side of the workpiece. Note down the coordinate value displayed in the machine tool coordinate system at this time, such as -340.500.
⑤According to this, the coordinate value of the origin of the workpiece coordinate system in the machine tool coordinate system is {-240.500+(-340.500)}/2=-290.500.
⑥Similarly, the coordinate value of the origin of the workpiece coordinate system in the machine tool coordinate system can be measured.
(2) Tool setting in z direction.
① Quickly move the tool over the workpiece.
② Start the spindle to rotate at medium speed, quickly move the worktable and spindle, let the tool quickly move to a position close to the upper surface of the workpiece at a certain safe distance, and then reduce the speed to move the tool end face close to the upper surface of the workpiece.
③ When approaching the workpiece, use fine-tuning operation (usually 0.01mm) to get closer, so that the end face of the tool slowly approaches the surface of the workpiece (note that when the tool, especially the end mill, is best to cut at the edge of the workpiece, the area where the end face of the cutter contacts the surface of the workpiece Less than a semicircle, try not to make the center hole of the end mill cut under the surface of the workpiece), make the end face of the tool just touch the upper surface of the workpiece, then raise the axis again, record the z value in the machine tool coordinate system at this time, -140.400 , then the coordinate value of the origin W of the workpiece coordinate system in the machine tool coordinate system is -140.400.
(3) Input the measured x, y, z values into the machine tool workpiece coordinate system storage address G5* (generally use G54~G59 codes to store tool setting parameters).
(4) Enter the panel input mode (MDI), enter “G5*”, press the start key (in automatic mode), and run G5* to take effect.
(5) Check whether the tool setting is correct.
2. Feeler gauge, standard mandrel, block gauge tool setting method
This method is similar to the trial cutting tool setting method, except that the spindle does not rotate during tool setting. A feeler gauge (or standard mandrel or block gauge) is added between the tool and the workpiece. The feeler gauge cannot move freely. Pay attention to calculations. When using coordinates, the thickness of the feeler gauge should be subtracted. Because the spindle does not need to rotate for cutting, this method will not leave marks on the surface of the workpiece, but the tool setting accuracy is not high enough.
3. Use tools such as edge finders, eccentric rods, and axis setters to set the tool.
The operation steps are similar to the trial cutting tool setting method, except that the tool is replaced with an edge finder or eccentric rod. This is the most common method. It has high efficiency and can ensure the accuracy of tool setting. When using the edge finder, care must be taken to ensure that the steel ball part is in slight contact with the workpiece. At the same time, the workpiece to be processed must be a good conductor and the positioning reference surface must have good surface roughness. The z-axis setter is generally used for transfer (indirect) tool setting methods.
4. Transfer (indirect) knife setting method
Processing a workpiece often requires the use of more than one knife. The length of the second knife is different from the length of the first knife. It needs to be re-zeroed. However, sometimes the zero point is machined away and the zero point cannot be directly retrieved, or the zero point cannot be retrieved directly. It is allowed to damage the processed surface, and there are some tools or situations where it is difficult to directly set the tool. In this case, the indirect change method can be used.
(1) For the first knife
① For the first knife, still use the trial cutting method, feeler gauge method, etc. Write down the machine tool coordinate z1 of the workpiece origin at this time. After the first tool is processed, stop the spindle.
② Place the tool setter on the flat surface of the machine tool workbench (such as the large surface of a vise).
③In the handwheel mode, use the hand to move the workbench to the appropriate position, move the spindle downward, press the top of the tool setter with the bottom end of the knife, and the dial pointer will rotate, preferably within one circle. Note down the axis at this time. Set the display value of the setter and clear the relative coordinate axis to zero.
④ Lift the spindle and remove the first knife.
(2) For the second knife.
①Install the second knife.
② In the handwheel mode, move the spindle downward, press the top of the tool setter with the bottom end of the knife, the dial pointer will rotate, and the pointer will point to the same indication A position as the first knife.
③Record the value z0 corresponding to the relative coordinate of the axis at this time (with positive and negative signs).
④ Raise the spindle and remove the tool setter.
⑤Add z0 (with plus or minus sign) to the original z1 coordinate data in G5* of the first tool to obtain a new coordinate.
⑥This new coordinate is the actual coordinate of the machine tool corresponding to the workpiece origin of the second tool. Enter it into the G5* working coordinate of the second tool. In this way, the zero point of the second tool is set. . The remaining knives are set in the same way as the second knife.
Note: If several tools use the same G5*, steps ⑤ and ⑥ are changed to store z0 in the length parameter of the No. 2 tool, and call the tool length correction G43H02 when using the second tool for machining.
5. Top knife setting method
(1) Tool setting in x and y direction.
① Install the workpiece on the machine tool worktable through the fixture and replace it with the center.
② Move the worktable and spindle quickly to move the tip close to the workpiece, find the center point of the workpiece drawing line, and reduce the speed to move the tip close to it.
③ Use fine-tuning operation instead, so that the tip slowly approaches the center point of the workpiece drawing line until the tip tip is aligned with the center point of the workpiece drawing line. Note down the x and y coordinate values in the machine tool coordinate system at this time.
(2) Remove the center, install the milling cutter, and use other tool setting methods such as trial cutting method, feeler gauge method, etc. to obtain the z-axis coordinate value.
6. Dial indicator (or dial indicator) tool setting method
Dial indicator (or dial indicator) tool setting method (generally used for tool setting of round workpieces)
(1) Tool setting in x and y direction.
Install the mounting rod of the dial indicator on the tool handle, or attach the magnetic seat of the dial indicator to the spindle sleeve. Move the workbench so that the center line of the spindle (i.e., the center of the tool) moves approximately to the center of the workpiece, and adjust the magnetic seat. The length and angle of the telescopic rod are such that the contacts of the dial indicator contact the circumferential surface of the workpiece. (The pointer rotates about 0.1mm.) Slowly turn the spindle by hand to make the contacts of the dial indicator rotate along the circumferential surface of the workpiece. Observe To check the movement of the dial indicator pointer, slowly move the axis of the workbench and repeat it several times. When the spindle is turned, the dial indicator pointer is basically at the same position (when the meter head rotates once, the jump amount of the pointer is Within the allowable tool setting error, such as 0.02mm), it can be considered that the center of the spindle is the axis and the origin of the axis.
(2) Remove the dial indicator and install the milling cutter, and use other tool setting methods such as trial cutting method, feeler gauge method, etc. to obtain the z-axis coordinate value.
7. Tool setting method with special tool setter
The traditional tool setting method has shortcomings such as poor safety (such as feeler gauge tool setting, the tool tip is easily damaged by a hard collision), taking up a lot of machine time (such as trial cutting, which requires repeated cutting several times), and large random errors caused by humans. It has been adapted to Without the rhythm of CNC machining, it is not conducive to giving full play to the functions of CNC machine tools.
Using a special tool setter to set tools has the advantages of high tool setting accuracy, high efficiency, and good safety. It simplifies the tedious tool setting work guaranteed by experience and ensures the high efficiency and high precision of CNC machine tools. It has become A special tool that is indispensable for tool setting on CNC processing machines.
Post time: Nov-01-2023
