Common Tool Setting Methods of CNC Milling Machine Center

Tool setting is the most important operation content in CNC machining, and its accuracy will directly affect the machining accuracy of parts. The tool setting method must be compatible with the machining accuracy requirements of the parts. This article systematically describes the use of common tool setting methods for CNC milling machines (machining centers) and their advantages and disadvantages, which has certain practical value. The purpose of tool setting is to determine the position of the workpiece coordinate system origin (program origin) in the machine tool coordinate system through the tool or the tool setting tool, and input the tool setting data to the corresponding storage location or set it through the G92 command. It is the most important operation content in CNC machining, and its accuracy will directly affect the machining accuracy of parts.
First, the positioning and clamping of the workpiece (preparation before tool setting)
The commonly used fixtures on CNC milling machines include vise, dividing head, Three-jaw self-centering chucks and platform fixtures, etc., generally use flat pliers to clamp workpieces when clamping economical CNC milling machines. Install the flat-nose pliers on the center of the worktable of the milling machine, align and fix the
flat-nose pliers, and according to the height of the workpiece, put a pad iron with a suitable shape and good surface quality in the jaws of the flat-nose pliers, and then Put in the workpiece, generally with the reference surface of the workpiece facing down, close to the surface of the pad iron, and then tighten the flat pliers.
Second, the determination of the tool setting point and the tool changing point
(1)The determination of the tool setting point
The tool setting point It is the reference point used to determine the position of the workpiece coordinate system in the machine tool coordinate system after the workpiece is positioned and clamped on the machine tool. The tool setting point can be selected on the workpiece or on the clamping and positioning components, but the tool setting point and the workpiece coordinate point must have an accurate, reasonable and simple position correspondence, which is convenient for calculating the position of the origin of the workpiece coordinate system on the machine tool. Generally speaking, it is best for the tool setting point to coincide with the origin of the workpiece coordinate system.
(2)Determination of the tool change point
On the milling machine or machining center that uses a variety of tools, the tool needs to be changed frequently during workpiece processing, and the tool change point should be based on the It depends on the principle that the tool does not touch the workpiece, fixture and machine tool when cutting.
Third. Common tool setting methods for CNC milling machines
The tool setting operation is divided into X, Y direction tool setting and Z To the knife. The accuracy of tool setting will directly affect the machining accuracy. The tool setting method must be compatible with the machining accuracy requirements of the parts.
According to the different tool setting tools used, the commonly used tool setting methods are divided into the following types: (1) trial cutting tool setting method; (2) feeler gauge, standard mandrel and block gauge tool setting method; (3) tool setting method using tools such as edge finder, eccentric rod and Z axis setter; (4) top tool setting method; (5) dial indicator (or dial gauge) tool setting method; (6) special tool setting device tool setting method.
In addition, according to the position of the selected tool setting point and the different data calculation methods, it can be divided into single-side tool setting, double-sided tool setting, transfer (indirect) tool setting method and “central zero” tool setting method (requires that the machine tool must be There are relative coordinates and clearing function), etc.
1.Try cutting tool setting method
This method is simple and convenient, but it will leave cutting marks on the surface of the workpiece, and the tool setting accuracy is low.
As shown in Figure 1, take the tool setting point (here coincident with the origin of the workpiece coordinate system) at the center of the workpiece surface as an example (using the bilateral tool setting method).

(1)X , Y direction tool setting
◎ Install the workpiece on the workbench through the fixture. When clamping, the four sides of the workpiece should reserve the position for tool setting.
◎Start the spindle to rotate at a medium speed, move the table and the spindle quickly, let the tool quickly move to a position close to the left side of the workpiece with a certain safety distance, and then reduce the speed to move close to the left side of the workpiece.
◎When approaching the workpiece, use fine-tuning operation (generally use 0.01mm to approach), let the tool slowly approach the left side of the workpiece, so that the tool just touches the left surface of the workpiece (observe and listen to the cutting sound , Look at the cut marks, look at the chips, as long as one of them occurs, it means that the tool touches the workpiece), and then retract 0.01mm. Write down the X coordinate value displayed in the machine tool coordinate system at this time, such as -240.500, etc.
◎Retract the tool in the positive direction of Z, reach above the workpiece surface, approach the right side of the workpiece in the same way, and record the X coordinate value displayed in the machine tool coordinate system at this time, such as -340.500 etc.
◎According to this, it can be obtained that the origin of the workpiece coordinate system is in the machine tool coordinate system. .
◎Similarly, the Y coordinate value of the workpiece coordinate system origin W in the machine tool coordinate system can be measured.
(2)ZTo tool setting
◎Move the tool quickly above the workpiece. From
◎The moving spindle rotates at a medium speed, and the worktable and the spindle are moved quickly, so that the tool moves quickly to a position close to the upper surface of the workpiece with a certain safety distance, and then moves at a reduced speed so that the end surface of the tool is close to the upper surface of the workpiece.
◎When approaching the workpiece, use fine-tuning operation (generally use 0.01mm to approach), let the end face of the tool slowly approach the surface of the workpiece (note that it is best to cut the tool, especially the end mill, at the edge of the workpiece , the area where the end face of the tool touches the surface of the workpiece is less than a semicircle, try not to make the center hole of the end mill under the surface of the workpiece), so that the end face of the tool just touches the upper surface of the workpiece, and then raise the Z axis by 0.01mm , write down the Z value in the machine tool coordinate system at this time, such as -140.400, etc., then the Z coordinate value of the workpiece coordinate system origin W in the machine tool coordinate system is – 140.400.
(3)Data storage
Input the measured X, Y, Z values ​​to the storage address of the machine workpiece coordinate system G5* (generally use G54~G59 codes to store tool setting parameters).
(4)Starting takes effect
Enter the panel input mode (MDI), input “G5*”, press the start key (in “automatic” mode ), run G5* to make it take effect.
(5)Check
Check whether the tool setting is correct, this step is very critical.
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, and the tool and Add a feeler gauge (or standard mandrel, block gauge) between the workpieces, as long as the feeler gauge just cannot twitch freely. Note that the thickness of the feeler gauge should be subtracted when calculating the coordinates. Because the spindle does not need to rotate for cutting, this method will not leave marks on the surface of the workpiece, but the accuracy of tool setting is not high enough.
3.The tool setting method using tools such as edge finder, eccentric rod and Zaxis setter
The operation steps are similar to the trial cutting method, except that Change the cutter to an edge finder or eccentric rod.
This is the most commonly used method with high efficiency and can ensure the accuracy of tool setting. Care must be taken when using the edge finder, so 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 plane has a good surface roughness. The Z axis setter is generally used for transferring (indirect) tool setting.
More than one tool is often required to machine a workpiece. The length of the second knife is different from the length of the first knife, and it needs to be zeroed again, but sometimes the zero point is processed, and the zero point cannot be directly retrieved, or it is not allowed to damage the processed surface, and some tools Or if the occasion is not good, directly to the knife. At this time, you can use indirectzero method.
(1)For the first knife
◎For Z of the first knife, still use the trial cutting method, feeler gauge method, etc. first. Write down the machine tool coordinates Z1 of the workpiece origin at this time. After the first tool is processed, stop the spindle.
◎Put the tool setter on the flat surface of the machine tool table (such as the large surface of the vise).
◎In the handwheel mode, use the hand crank to move the worktable to a suitable position, move the spindle down, press the top of the tool setting device with the bottom of the knife, and the pointer on the dial will rotate, preferably within one circle , record the indication A of the Z axis setter at this time and clear the relative coordinate Z axis to zero.
◎Raise the spindle and remove the first knife.
(2)For the second knife
◎Install the second knife.
◎In the handwheel mode, move the main shaft downward, press the top of the tool setting device with the bottom end of the knife, the pointer on the dial turns, and the pointer points to the same display A position as the first knife .
◎Record the value Z0 (with sign) corresponding to the relative coordinate of the Z axis at this time.
◎Raise the spindle and remove the tool setter.
◎ Add Z0 (with plus or minus sign) to the Z1 coordinate data in G5* of the original first tool to get a new Z coordinate
◎The new Z coordinate is the actual coordinate of the machine tool corresponding to the workpiece origin of the second tool we are looking for, input it into the G5* working coordinate of the second tool, In this way, the zero point of the second knife is set. The other knives are set in the same way as the second knife.
Note: If several knives use the same G5*, the procedure should be changed to store Z0 in the length parameter of the second tool and use the second tool Just call tool length compensation G43H02 during processing.
4.Top tool setting method
(1)X, YToward tool setting
◎Put the workpiece through the fixture Install it on the machine table and replace it with the top.
◎Move the table and spindle quickly, let the top move to the top of the workpiece, find the center point of the workpiece line, and move at a lower speed to make the top close to it.
◎Use the fine-tuning operation instead, let the tip slowly approach the center point of the workpiece line until the tip point is aligned with the center point of the workpiece line, and record the X in the machine tool coordinate system at this time , Y coordinate value.
(2)ZRemove the top to the tool setting
, install the milling cutter, and use other tool setting methods such as trial cutting method, feeler gauge method, etc. to get Z Axis coordinate value.
5.Dial indicator (or dial indicator) tool setting method
This method is generally used for tool setting of circular workpieces.
(1) X, Y for tool setting
As shown in Figure 2, install the dial indicator rod on the tool handle, or Attract the magnetic base of the dial indicator on the spindle sleeve, move the worktable so that the center line of the spindle (that is, the center of the tool) is approximately moved to the center of the workpiece, adjust the length and angle of the telescopic rod on the magnetic base, and make the contact of the dial indicator Touch the peripheral surface of the workpiece, (the pointer rotates about 0.1mm) slowly rotate the main shaft by hand, so that the contact of the dial indicator rotates along the peripheral surface of the workpiece, observe the movement of the pointer of the dial indicator, and slowly Move the X axis and Y axis of the worktable. After repeated repetitions, the pointer of the dial indicator is basically at the same position when the main shaft is turned (when the head of the meter rotates one circle, the jump of the pointer is within the allowable Tool error, such as 0.02mm), then the center of the spindle can be considered as the origin of the X axis and the Y axis.
(2)ZTo the tool setting
, 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 get Z Axis coordinate value.
Figure 2 Dial gauge (or dial gauge) knife setting method

6.Special tool setting tool setting method
The traditional tool setting method has poor safety (such as Feeler gauge against the knife, head-to-head collision with the tip of the knife is easy to damage) , it takes up a lot of machine time (#p#page title#e#If you try to cut, you need to cut and measure several times) and the randomness brought by man However, due to the shortcomings such as large sexual error, it can no longer adapt to the rhythm of CNC machining, which is very unfavorable for the function of CNC machine tools. Using a special tool setting device for tool setting 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 A special tool that is indispensable for tool setting on CNC machining machines. Due to different processing tasks, special tool setting devices are also very different, so I will not expand here. Readers can design different tool setting devices according to different needs in specific work to meet their own processing needs..