3Q MACHINING is a top-quality CNC machining manufacturer in DONGGUAN, GUANGDONG, CHINA. We are working our best work for your custom plastic & metal machining parts from design drawing or sample to final shipment with fast delivery and low MOQ. We are using advanced technology and equipment to offer high precision for producing metal and plastic machining parts. In this article, we focus on some CNC machining skills and troubleshooting measures.
Three common faults and solutions in CNC machining
CNC machining is a very detailed and difficult job. Many front-line CNC machining workers will encounter some problems in their actual work. Based on years of experience in the CNC machining industry, 3QMACHINING has summarized three common faults and correct countermeasures in the CNC machining process for your reference.
CNC machining handwheel failure
- The handwheel shaft selector switch is in poor contact. This problem needs to enter the system self-check to observe the specific conditions of the matching contacts of the axis selection switch (that is, the specific conditions of the connection line) and replace the switch if it is damaged.
- The handwheel multiple selector switch is in poor contact. The correct step to deal with the poor contact of the CNC machining handwheel multiple selector switch is to enter the system self-check to observe the specific conditions of the multiple switch matching contacts (ie the specific conditions of the connection line), and replace the switch if it is damaged.
- For the damage of the handwheel pulse disc, you need to remove the pulse disc to measure the switching power supply to see if everything is normal, and if the resistance between + and A, + and B is normal, replace it if it is damaged.
- The connection line of the CNC machining handwheel is broken. The staff enters the system self-check to observe the specific conditions of the matching contacts of each switch, and then measure whether the contacts of the connecting line between the axis selection switch, the multiple switches, and the pulse plate are on or off with the corresponding point of the terminal in the system, if it is broken, replace it That’s it.
CNC machining center cannot return to zero
- The CNC machining origin switch contact is stuck and cannot be moved. Professional staffers are required to clean the stuck position to make it move smoothly, or replace the travel switch.
- The CNC machiningorigin stop can’t press the origin switch to the switch action position. Adjust the installation position of the travel switch so that the zero switch contact can be smoothly pressed to the switch action position by the stopper.
- Water in the origin switch causes poor contact of the switch contacts. Replace the travel switch and take waterproof measures.
- The origin switch circuit of the CNC machiningcenter is disconnected or the input signal source is faulty. Check whether the switch circuit is open or short-circuited and whether there is a signal source.
The problem with the CNC machining tool magazine
- The tool suddenly stopped during CNC machiningand the tool change could not be continued. It is necessary to check whether the air pressure is sufficient. If the air pressure does not reach the ideal air pressure, the tool change will fail.
- The hat-style tool magazine cannot come out. Check whether the CNC machiningtool magazine retreat data signal is in place, whether the tool magazine’s solenoid valve circuit and the PLC areoutput.
- The tool cannot be released during CNC machining. Adjust the amount of punching on the lathe, and check whether there is water in the punching cylinder, and deal with it in time.
- The CNC machiningcutter head suddenly rotates in the reverse direction and the time difference is half a tool position. This is because the brake mechanism of the tool magazine motor is loose and cannot brake normally.
- When the tool is changed, the error alarm of tool loosening and tool tightening occurs. Check the air pressure of the CNC machining center, whether the cylinder is fully operated (whetherthereis water), and whether the knife release switch is pressed in place, and it cannot be pressed too much.
Countermeasures for vibration during CNC machining
In the CNC machining process, there will be more or less vibration. In order to maintain better precision machining accuracy, we must effectively control and avoid vibration.
- Use sharp blades to reduce the cutting force of the CNC milling machine. Machine clamp blades are divided into coated and non-coated blades. Non-coated blades are usually sharper than coated blades because if the blade is to be coated, the cutting edge must be passivated (ER treatment). Because the sharp cutting edge will affect the bonding strength of the coating at the cutting edge.
- When the depth of cut is constant, the use of a small corner radius can undoubtedly reduce the cutting force, especially the radial cutting force, and the radial cutting force is the main reason for the vibration of the slender rod tool or workpiece, whether it is ram or milling. The greater the corner radius, the greater the tendency for slender tool holders to vibrate at the same cutting depth.
- When the depth of cut can be selected. Avoid cutting depth equal to the corner radius.
- For cutting of a sharp knife with a slender tool bar or external turning of a slender shaft, the use of a tool with an entering angle of 90° is beneficial to damping vibration. Whether it is turning a slender shaft with an external turning tool or a tool hole of a slender tool bar, the tool with a 90° entering angle always produces the smallest radial cutting force. At the same time, the axial force generated by the blade edge is the largest.
- For milling cutters with slender rods, round blade milling cutters are most conducive to damping vibration. The milling cutter is opposite to the stirring cutter. The closer the entering angle is to 90°, the greater the radial cutting force, and the greater the vibration of the cutter bar. Therefore, in the face milling of the deep hole cavity of the mold, the CNC milling machine usually uses a 45° entering angle milling cutter. If the cutting depth is less than 1mm, a round blade milling cutter or a ball cutter is often used.
- When the CNC milling machine uses a slender rod end mill to mill a deep cavity, plunge milling is often used. Plunge milling is the axial feed of the tool like a drill. When milling deep cavities, the overhang of the long rod is usually greater than 3 times the diameter of the tool rod. We recommend plunge milling with axial feed. However, the edge of the end mill insert has a radial cutting edge with a certain width.
- In the milling of thin-walled workpieces, the cause of vibration is entirely from the workpiece, which is called a box-type or bowl-type part. Since the vibration comes from the workpiece itself, when processing this type of part milling, it is mainly to improve the clamping of the workpiece.
- When boring the inner hole, the smaller the blade edge angle, the better. In this way, the secondary main deflection angle is large, and the vibration contact area between the secondary cutting edge and the processed surface is small, and the vibration is difficult to turn into vibration. The chance of chip squeezing by the secondary cutting edge is also small.
- If the face milling cutter adopts sparse tooth unequal pitch milling cutter, milling vibration can be reduced. Here “tooth” refers to the blade. Face milling cutter of the same diameter (for example, 100mm). If their three cutting elements are equal, then the cutter head with 5 blades must produce 50% less milling force than the cutter head with 10 blades.
- Use a blade with a positive rake angle and a large relief angle. And with a brisk chip breaker. Such inserts have the smallest cutting wedge angle in filing or milling, and of course, the cutting is faster.
- Adjust cutting parameters. Adjusting the cutting parameters may be effective only when the cutting vibration is not serious. The general adjustment method is as follows: reduce the rotation speed of the tool or workpiece, reduce the depth of cut and increase the amount of cutting per revolution of the tool or milling cutter. If vibration occurs during the internal thread turning, the feed steps to complete the thread turning can be reduced by 1 to 2 cuts.
- Reasonably arrange the process path of the tool. Arranging the process path of the tool reasonably is very important for milling processing. Milling can be divided into down milling and up milling. According to the traditional milling theory, the use of up-milling is beneficial to reduce milling vibration, but it actually means to help suppress the vibration generated by the gap of the lead screw. Most of today’s milling equipment is equipped with ball or roller screws. Therefore, up-milling is of little significance to reduce vibration. Whether it is down milling or up milling, as long as the direction of the milling force is consistent with the clamping direction of the workpiece, it will help eliminate the vibration of the bent plate parts.
Some skills of CNC machining
CNC machining is a very superb and complex technology. If we want to master such a technology, we need to know a lot of familiar things. In order to better processing operations, we must master some skills and common sense.
- When the appearance needs to be finely finished, first rough, then polish. When the workpiece is too high, polish the edges first, then polish the bottom.
- where the slope is an integer, use a slope tool to process, such as pipe position.
- When walking WCUT, if you can go FINISH, don’t go ROUGH.
- When the workpiece is too high, use different length cutters to cut the thickness.
- Take simple tool paths as much as possible, such as appearance, grooving, one-sided, and less surrounding height.
- The plane is processed with flat-bottomed tools, and ball tools are used less to reduce the processing time.
- Do more procedures to reduce the empty tool time. Do more thinking to reduce the chance of error. Do more auxiliary lines and auxiliary surfaces to improve processing conditions.
- When clearing the corners of copper, first check the size of the R on the corner, and then confirm the size of the ball tool.
- Create a sense of responsibility, carefully check each parameter to prevent rework.