CNC Technology – Page 19 – CNC Machining & Turning, Milling, Metal parts

Introduction of CNC milling machine

The biggest difference between CNC milling machine and machining center is that the machining center has the ability to exchange machining tools automatically. By installing different tools on the tool magazine, the machining tools on the spindle can be changed through the automatic tool changing device in one clamping, and a variety of machining functions can be realized.

CNC machining center is composed of mechanical equipment and CNC system, which is suitable for processing complex parts. CNC machining center is one of the most widely used CNC machine tools with the highest output in the world. Its comprehensive processing ability is strong, the workpiece can complete more processing content after clamping at one time, and the processing accuracy is high. For the batch workpiece with medium processing difficulty, its efficiency is 5-10 times higher than that of ordinary equipment, especially it can complete the processing that many ordinary equipment can’t complete, and it is more suitable for single piece processing with complex shape and high precision requirements or small and medium batch multi variety production. It concentrates the functions of milling, boring, drilling, tapping and cutting threads on one equipment, so that it has a variety of technological means. Machining centers are classified into horizontal and vertical machining centers according to the spatial position of the spindle. According to the classification of process uses: boring and milling machining center, composite machining center. According to the special functions, there are single table, double table and multi table machining centers. Machining center of single axle, double axle, three axle and changeable headstock.

CNC computer gong debugging method

CNC computer gong processing machine precision and function debugging method:

Using precision level instrument and other testing tools, the main bed level of the computer gong processing machine tool is precisely adjusted by adjusting the pad iron, so that the geometric accuracy of the machine tool can reach the allowable tolerance range;
For the automatic tool changing device, adjust the position of tool magazine, manipulator, stroke parameters, etc., and then check the action with instructions to ensure accuracy;
For the machine tool with APC automatic exchange table, after adjusting the relative position, carry out automatic exchange;
After the adjustment of the machine tool, carefully check whether the parameter setting values in the numerical control system and the programmable controller conform to the data specified in the random index, and then test the main operation functions, safety measures, and the execution of common instructions.
Check the auxiliary functions and accessories of the machine. CNC computer gong NC machining is the basis of modern manufacturing technology, this invention for the manufacturing industry, has epoch-making significance and far-reaching influence.

CNC machining center milling cutter

CNC machining center used on the milling cutter, should choose all cemented carbide, general milling machine used on the selection of white steel material. The hardness of white steel milling cutter is softer than that of cemented carbide milling cutter. Cemented carbide milling cutter has good thermal hardness, wear resistance, but poor impact resistance. The carbide is made by powder metallurgy. Its hardness can reach about 90hra and its thermal property can reach about 900-1000 degrees.

Number of milling cutter teeth

When selecting a milling cutter, the number of teeth should be considered. For example, the coarse tooth milling cutter with a diameter of 100 mm only needs 6 teeth, while the dense tooth milling cutter with a diameter of 100 mm can have 8 teeth. The size of pitch will determine the number of cutter teeth to be cut together in milling, which affects the smoothness of cutting and the requirement of cutting rate.

Chip holding tank

Coarse tooth milling cutter is mostly used for rough machining, because it has a large chip holding groove. Assuming that the chip holding groove is not large enough, it will make it difficult to roll the chip or the conflict between the chip and the tool body or workpiece aggravate. At the same feed rate, the cutting load of coarse tooth milling cutter is larger than that of dense tooth milling cutter.

Cutting depth

In finish milling, the cutting depth is shallow, generally 0.25-0.64mm. The cutting load of each tooth is small (about 0.05-0.15mm), and the power required is small. It is able to select dense tooth milling cutter, and it is able to select larger feed rate.

Application of rough milling

In heavy load rough milling, excessive cutting force can make the machine tool with poor rigidity vibrate. This kind of chatter will lead to the edge collapse of cemented carbide blade, and then shorten the tool life. Selecting coarse tooth milling cutter can reduce the requirement of machine power.

CNC machining center workpiece processing process is no longer like the traditional processing equipment, the need for uninterrupted control of the machine tool to end, control the function parts of the machine tool for messy and precise action, and then high-precision, efficient end of the processing process. The programming of workpiece processing is the key of workpiece processing in machining center. However, if the programming is not reasonable or the parameters are not set properly, the machining accuracy and power of the workpiece will be seriously affected, such as overcutting. Overcutting is a serious problem in workpiece processing, which can lead to the invalidation of workpiece. For some reason, the front-line processing personnel have worked out the processing program which is sure to be overcut. If the system can announce the alarm signal in advance in the working process, the overcut can be avoided.

CNC machining center cutting oil

It often causes oil leakage in CNC machining center. There are three main problems in oil change. First, for the parts with high viscosity lubricating oil, it will affect the sealing performance of the corresponding box, shaft hole and other parts, and sometimes greatly reduce the sealing performance of these parts. Second, if the oil tank is not cleaned when changing oil, the dirt in the oil tank may enter into the lubrication system, block the oil circuit and wear the seals, causing oil leakage. Third, when changing the oil, the amount of oil is too much, especially in the parts with rotating parts, because of the stirring effect of rotating parts, it is more prone to oil spill.

Improper selection and adjustment of lubrication system parts cause oil leakage.

For example, when CNC machining and maintenance personnel select the oil pump with too high pressure or too large oil output, or when adjusting the system pressure, the pressure of relief valve, safety valve and pressure reducing valve is too high, and the flow of CNC machine tool lubrication system is too large, which does not match with the oil return system and sealing system, it will cause oil leakage.

In fact, it is not just the above points that cause the oil leakage of CNC machining center. If we encounter similar problems in operation, we must do a good job in checking and find out the reasons in time to avoid unnecessary losses. After the purchase of the machining center, do a comprehensive inspection to see if there are casting defects or parts damage, if any, contact the manufacturer in time. When operators use CNC machining center to process workpieces, they should also pay attention to the following points:

(1) For the first trial cutting process of CNC machining, the single-stage operation mode should be adopted.

(2) When the CNC milling machine starts to run automatically, the fast rate and feed rate s are in the lowest gear, and then the efficiency is improved after cutting into the workpiece.

(3) In the operation of NC milling machine, we need to pay attention to the coordinate display of CNC system.

CNC thread milling method

To be proficient in the operation of CNC machine tools, we should learn: system operation mode, fixture installation, part benchmark alignment, tool setting, zero offset setting, tool length compensation, radius compensation, tool and handle loading and unloading, tool grinding, part measurement (proficient in using vernier caliper, micrometer, dial indicator, dial indicator, inner diameter lever), etc .

Can reflect the level of an operator is: horizontal processing, and large gantry (moving beam, top beam) processing. Must have good fixture foundation and measurement technology level. The difficulty of fixture analysis is that it can only be qualitative, but it is difficult to be quantitative.

In the process of CNC machining, there is a method called thread milling. What is it? CNC thread milling is a milling method which uses thread milling cutter, machining center three-axis linkage, namely x, Y axis arc interpolation, Z axis linear feed.

Thread milling is mainly used for large hole thread and difficult to machine material thread hole. It has the following characteristics:

(1) high processing speed, high efficiency and high processing precision. The cutting tool is made of cemented carbide, and the cutting speed is fast. Therefore, the precision of thread milling tool is high.

(2) milling tools are widely used. As long as the pitch is the same, whether it is * * thread or right-hand thread, a tool can be used, which is conducive to reducing the cost of the tool.

(3) milling is easy to remove chips and cool, and the cutting condition is better than tap. It is especially suitable for thread machining of difficult to machine materials such as aluminum, copper and stainless steel,

Especially suitable for large parts and valuable material parts of the thread processing, to ensure the quality of thread processing and workpiece safety.

(4) because there is no tool front-end guide, it is suitable for processing blind holes with short thread bottom holes and holes without undercut.

CNC machining center fault inspection

The spindle is the power auxiliary device of CNC machining center. The spindle drives the workpiece to rotate to process the workpiece of the rotating body. Spindle is an important guarantee for high-speed and high-precision machining of CNC machining center, so the maintenance methods and skills of spindle fault are the basic knowledge that operators and maintenance personnel of CNC machining center must master. In the operation of CNC machining center, the spindle will inevitably have some faults. What is the specific reason?

Different types of CNC machining centers adopt different types of spindles. According to the different transmission systems, the spindle system can be divided into the main transmission spindle with variable speed gear, the main transmission spindle with belt transmission, the dual motor drive spindle and the motor spindle integrated spindle. No matter what type of spindle application, the common faults in use are as follows:

Overload.

Fault causes: excessive cutting amount, frequent forward and reverse rotation, spindle motor fault, spindle drive device fault.

The spindle does not rotate

Fault causes: spindle drive failure, CNC device can not output speed signal, spindle motor failure, spindle drive failure, drive belt fracture.

The spindle speed deviates from the command value

Fault causes: motor overload, CNC system output spindle speed command output problem, speed measuring device failure or speed feedback signal disconnection.

CNC machine tool debugging

Before the debugging of CNC computer gong processing machine tool, the debugging methods for the precision and function of CNC computer gong processing machine tool are as follows:

Using precision level instrument and other testing tools, the main bed level of the computer gong processing machine tool is precisely adjusted by adjusting the pad iron, so that the geometric accuracy of the machine tool can reach the allowable tolerance range;
For the automatic tool changing device, adjust the position of tool magazine, manipulator, stroke parameters, etc., and then check the action with instructions to ensure accuracy;
For the machine tool with APC automatic exchange table, after adjusting the relative position, carry out automatic exchange;
After the adjustment of the machine tool, carefully check whether the parameter setting values in the numerical control system and the programmable controller conform to the data specified in the random index, and then test the main operation functions, safety measures, and the execution of common instructions.
Check the auxiliary functions and accessories of the machine. CNC machining is the basis of modern manufacturing technology. This invention has epoch-making significance and far-reaching influence for the manufacturing industry. CNC machining centers are usually classified by the relative position of the spindle and the workbench, which are divided into vertical, horizontal and multi axis linkage machining centers.

1、 Vertical machining center: it refers to the machining center with the spindle axis perpendicular to the worktable. It is mainly suitable for processing plate, plate, mold and small shell complex parts.

2、 Horizontal machining center: it refers to the machining center with the spindle axis parallel to the workbench, which is mainly suitable for machining box parts.

3、 Multi axis linkage machining center: it refers to the machining center that can control the linkage change by processing the angle between the spindle axis and the rotary axis of the worktable, and complete the machining of complex spatial surface. It is suitable for the machining of impeller rotor, mold, cutting tool and other workpieces with complex spatial surface.

How to improve the efficiency of CNC machining

(1) The size and structure of all kinds of parts are very different, and the universality of machine tools and other process equipment is not high.

(2) Many companies are usually faced with the production task of multi variety, small batch and short production cycle, so the process system is required to have a higher response speed.

(3) The structure of product parts is complex and the processing is difficult.

(4) Thin wall, easy to produce processing deformation. There are a lot of thin-walled and deep cavity structures, which are typical weak rigid structures.

(5) It is difficult to select cutting tools and cutting parameters. Because the development of tool industry can’t catch up with the development and application of new materials, and lack of the support of machining database.

So how to improve the efficiency of CNC machining? Generally speaking, the methods to improve the machining efficiency of CNC machine tools are as follows:

1、 Change the understanding of numerical control technology.

Numerical control technology is a comprehensive technology, in addition to the numerical control machine tool, there must be corresponding supporting technology and personnel support, especially in the numerical control processing process, people play a decisive role, the technical ability of management personnel, engineering and technical personnel, engineering maintenance personnel and operators will affect the production efficiency of numerical control machine tool.

2、 Develop effective tool management measures.

For example, the tool is pre adjusted to reduce the installation and adjustment time of the tool on the machine tool, and the tool is managed through the management system to reduce the errors caused by manual management.

3、 Fixture management.

Because the selection of fixture is directly related to the installation time and measurement time of workpiece, the management of fixture should be realized.

Computer gong processing tool setting point

When the machining accuracy is not high, some surfaces on the workpiece or fixture can be directly used as the tool face; when the machining accuracy is high, the tool setting point should be selected on the design basis or process basis of the part as far as possible, for example, for the part with hole positioning, it is more appropriate to take the axis of the hole as the tool setting point. The tool setting point must have a certain coordinate relationship with the positioning datum of the workpiece. In this way, the relationship between the machine tool coordinate system and the workpiece coordinate system can be determined. The selection of tool setting point should be convenient for coordinate value calculation and tool setting. During tool setting, the tool setting point should coincide with the tool position. The so-called cutter site refers to the intersection of the tool axis and the bottom surface of the tool for the flat end end milling cutter; for ball end milling cutter, it refers to the ball center of the ball head part; for turning tool, it refers to the tool tip; for the drill bit, it refers to the drill point; for the linear electrode cutting machine, it refers to the focus of the axis of the wire electrode and the part surface.

Stress and warpage analysis based on two-sided flow technique

According to the analysis results of gate solidification effect and packing pressure and temperature distribution, the stress and warpage analysis module calculates the stress changes with time in the wall thickness and plane direction of the product, and the shrinkage of the product along the wall thickness direction at the time of demoulding. Based on the double-sided flow technique, a special double-layer shell element is used to predict the warpage of the product at the time of demoulding.

Troubleshooting of CNC machining center

Overload.

Fault causes: excessive cutting amount, frequent forward and reverse rotation, spindle motor fault, spindle drive device fault.

The spindle does not rotate

Fault causes: spindle drive failure, CNC device can not output speed signal, spindle motor failure, spindle drive failure, drive belt fracture.

The spindle speed deviates from the command value

Fault causes: motor overload, CNC system output spindle speed command output problem, speed measuring device failure or speed feedback signal disconnection.