Setting CNC lathe tools is an important skill in processing. The accuracy of tool setting determines the accuracy of workpiece processing. The efficiency of tool setting directly affects the efficiency of workpiece processing.
After the CNC lathe is turned on, it must perform a return-to-zero (reference point) operation. The aim is to establish a unified benchmark for position measurement, control and display of the CNC lathe. origin of the machine tool. The origin of the machine tool is generally at the maximum positive stroke of the tool, its position is determined by the position sensor of the machine tool.
After the machine tool returns to zero, the distance between the tool position (tool tip) and the origin of the machine tool is fixed. Therefore, in order to facilitate the adjustment and processing of the tool, the position of the tool tip after the machine tool returns. to zero can be regarded as the origin of the machine tool. Tool setting is the operational process of establishing the workpiece coordinate system in the machine tool coordinate system of the CNC machine tool and matching the origin of the workpiece coordinate system with the origin of the programming.
Use trial cutting or non-contact methods to measure the distance between the tool tip programming point in the machine tool coordinate system and the processing origin point in the X and Z, and set the values in the machine tool parameters. Through program calls, the workpiece coordinate system is established. The base point in the program is The absolute value of the coordinates is based on the origin of the workpiece coordinate system established to process the workpiece contour.
1. Principle of knife adjustment
The purpose of tool setting is to establish the workpiece coordinate system. Intuitively, tool setting involves establishing the position of the workpiece in the machine tool bench. coordinate system.
For CNC lathes, the tool set point must first be selected before processing. Tool set point refers to the starting point of tool movement relative to the workpiece when the CNC machine tool is used to process the workpiece. The tool set point can be set on the part (such as design reference or positioning reference on the part), or it can be set on the fixture or machine tool if set to a certain point of the device or machine tool. , the point must be consistent with the positioning data of the workpiece. Maintain dimensional relationships with a certain degree of precision.
When adjusting the tool, the tool position point must coincide with the tool setting point. The tool position point refers to the tool positioning reference point. For turning tools, the tool position point is the tool tip. The purpose of tool setting is to determine the absolute value of the coordinates of the tool setting point (or workpiece origin) in the machine tool coordinate system and measure the value d tool position deviation. The accuracy of tool point alignment directly affects machining accuracy.
In the actual processing of the workpiece, the use of a single tool generally cannot meet the processing requirements of the workpiece, and multiple tools are generally used for processing. When using multiple turning tools for machining, when the tool change position remains unchanged, the geometric position of the tool tip will be different after tool change, requiring different tools can process at different starting positions when starting processing. the program works normally.
In order to solve this problem, the CNC system of the machine tool is equipped with a tool geometric position compensation function. With the tool’s geometric position compensation function, you simply measure the position deviation of each tool from a pre-selected reference tool. Go ahead and input it into the CNC system. Specify the group number in the tool parameter offset 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 the tool position deviation must also be carried out by tool adjustment operations.
2. Knife adjustment method
In CNC machining, the basic tool setting methods 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. Knife cutting and adjustment test method
This method is simple and convenient, but it will leave cutting marks on the workpiece surface and the tool setting accuracy is low. 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) Adjust the tool in the x and y directions.
① Install the workpiece on the workbench through the clamp when clamping, there should be space for tool adjustment on all four sides of the workpiece.
② Start the spindle to rotate at medium speed, quickly move the worktable and spindle, let the tool move quickly to a position with a certain safety distance close to the left side of the workpiece, and then reduce the speed and move closer to the left. side of the workpiece.
③ When approaching the workpiece, use a 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 step back 0, 01mm. Note the coordinate value displayed in the machine tool’s coordinate system at that time, for example -240.500.
④Retract the tool in the positive z direction above the surface of the workpiece. Use the same method to approach the right side of the workpiece. Note the coordinate value displayed in the machine tool’s coordinate system at that time, for example -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 adjustment in Z direction.
① Quickly move the tool over the workpiece.
② Start the spindle to rotate at medium speed, move the worktable and spindle quickly, let the tool move quickly to a position close to the top surface of the workpiece at a certain safe distance, and then reduce the speed to move the end face of the tool. near the top surface of the part.
③ When approaching the workpiece, use fine-tuning operation (generally 0.01mm) to get closer, so that the end face of the tool slowly approaches the workpiece surface (note that When the tool, especially the end mill, is best cut at the edge of the workpiece, the area where the end face of the milling cutter contacts the surface of the workpiece Smaller than a half. circle, try not to use the end mill Cut the center hole on the surface of the workpiece), so that the end face of the tool just touches the top surface of the workpiece, then raise the axis, record the z value in the coordinate system of the machine tool at this time, – 140.400, then the origin W of the workpiece coordinate system is on the machine tool. The coordinate value in the coordinate system is -140.400.
(3) Input the measured x, y, z values into the G5* machine tool workpiece coordinate system storage address (generally use G54~G59 codes to store tool setting parameters ).
(4) Enter panel input mode (MDI), enter “G5*”, press Start key (in automatic mode) and execute G5* to take effect.
(5) Check if the tool setting is correct.
2. Feeler gauge, standard chuck, 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 chuck or block gauge) is added between the tool and the workpiece. Pay attention to the calculations. When using coordinates, the thickness of the feeler gauge must be subtracted. Since the spindle does not need to rotate to cut, this method will not leave marks on the workpiece surface, but the accuracy of tool setting is not high enough.
3. Use tools such as edge finders, eccentric rods and axle adjusters to adjust the tool.
The operation steps are similar to the trial cutting tool adjustment 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 guarantee the accuracy of tool adjustment. When using the edge finder, care must be taken to ensure that the spherical steel part is lightly in contact with the workpiece. At the same time, the workpiece must be a good conductor, and the positioning reference surface must have good surface roughness. . The z-axis adjuster is generally used for transfer (indirect) tool setting methods.
4. Transfer (indirect) knife adjustment method
Processing a part often requires the use of several knives. The length of the second knife is different from the length of the first knife. However, sometimes the zero point is machined. cannot be recovered directly, or the zero point cannot be recovered directly. It is allowed to damage the treated surface, and there are certain tools or situations in which it is difficult to directly adjust the tool. In this case, the indirect change method can be used. used.
(1) For the first knife
① For the first knife, always use the trial cutting method, feeler gauge method, etc. At this time, note the machine tool coordinate z1 of the origin of the part. Once the first tool has been processed, stop the spindle.
② Place the tool setting device on the flat surface of the machine tool bench (such as the large surface of a vice).
③In handwheel mode, use hand to move the workbench to a suitable position, move the spindle down, press the top of the tool adjuster with the lower end of the knife, and the dial pointer will rotate , preferably in a circle. Noticed. down the axis at this time. Set the display value of the adjuster and clear the coordinate axis relative to zero.
④ Lift the pin and remove the first knife.
(2) For the second knife.
①Install the second knife.
② In handwheel mode, move the spindle down, press the top of the tool adjuster with the lower end of the knife, the dial pointer will rotate, and the pointer will point to the same A indication position as the first knife.
③Record the z0 value corresponding to the relative axis coordinate at this time (with positive and negative signs).
④ Lift the spindle and remove the tool adjuster.
⑤Add z0 (with positive and negative 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 part origin of the second tool. Enter it in the G5* work coordinate of the second tool. In this way the zero point of the second tool is defined. The remaining knives are adjusted in the same way as the second knife.
Note: If multiple tools use the same G5*, steps ⑤ and ⑥ are changed to store z0 in the length parameter of tool #2. When using the second tool to process, simply call the length offset d tool G43H02.
5. Upper knife adjustment method
(1) Adjust the tool in the x and y directions.
① Install the workpiece on the machine tool worktable through the fixture and replace it from the center.
② Quickly move the worktable and spindle to bring the tip closer to the workpiece, find the center point of the workpiece drawing line, and reduce the speed to bring the tip closer to the workpiece.
③ Rather use fine-tuning operation, let the tip slowly approach the center point of the workpiece drawing line, until the tip of the tip is aligned with the center point of the workpiece drawing line. the part, save the x, y coordinate values in the machine. coordinate system of the tool at that time.
(2) Remove the center, install the cutter, and use other tool setting methods such as trial cutting method, feeler gauge method, etc. to get the z axis coordinate value.
6. Dial Indicator (or Dial Indicator) Tool Setting Method
Dial (or dial indicator) tool setting method (usually used for tool setting of round workpieces)
(1) Adjust the tool in the x and y directions.
Install the dial indicator mounting post to the tool handle or attach the dial indicator magnetic seat to the spindle sleeve. Move the workbench so that the centerline of the spindle (i.e. the center of the tool) moves approximately to. the center of the room 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 approximately 0.1 mm.) Slowly turn the spindle. by hand so that the dial indicator contacts the circumferential surface of the workpiece. Rotate the contact along the circumferential surface of the workpiece, observe the movement of the dial indicator pointer, and slowly move the axis and axis of the workbench. After many repetitions, the dial indicator pointer is basically in the same position as the spindle rotates. (indicator When the head rotates once, the jump amount of its pointer is within the allowable tool setting error, such as 0.02mm. At this time, 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 cutter, and use other tool setting methods such as trial cutting method, feeler gauge method, etc. to get the z axis coordinate value.
7. Tool adjustment method with a special tool adjuster
The traditional tool setting method has disadvantages such as poor safety (such as feeler gauge tool setting, the tool tip is easily damaged by hard contact), consuming a lot of machine time (such as a trial cut which requires repeated cutting several times), and large random errors caused by humans. It cannot adapt to the pace of CNC machining and is not conducive to fully exploiting the functions of CNC machine tools. Using a special tool adjuster to adjust tools has the advantages of high tool setting accuracy, high efficiency and good safety. This simplifies the tedious tool setting work guaranteed by experience and ensures the high efficiency and high precision of CNC machine tools. An essential special tool for tool adjustment on CNC machining machines.
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