September 2020 – Page 25 – CNC Machining & Turning, Milling, Metal parts

Machining concept

Machining process is the process of manufacturing workpieces or parts. The process of changing the shape, size and surface quality of blank directly by mechanical processing method is called machining process. For example, the processing process of an ordinary part is rough machining – finishing – assembly – Inspection – packaging, which is a general process of processing.

Mechanical processing technology is to change the shape, size, relative position and nature of the production object on the basis of the process to make it a finished product or semi-finished product. It is a detailed description of each process. For example, as mentioned above, rough machining may include blank manufacturing, grinding, etc. finishing may be divided into turning, fitter, milling machine, etc., and each step should be detailed Fine data, such as how much roughness to achieve, how much tolerance.

According to the quantity of products, equipment conditions and the quality of workers, technicians determine the technological process to be adopted, and write the relevant contents into process documents, which are called process procedures. This is more targeted. Every factory may be different, because the actual situation is different.

Advantages of CNC machining compared with NC machining

The so-called five axis machining here means that there are at least five coordinate axes (three linear coordinates and two rotation coordinates) on a machine tool, and the machining can be carried out simultaneously under the control of computer numerical control (CNC) system. Compared with the general three axis NC machining, this kind of five axis CNC machining has the following advantages:

1、 It can process continuous and smooth free-form surface which can not be machined by general three-axis or it is difficult to finish machining by clamping at one time. For example, the blades of aeroengine and steam turbine, the screw propeller used in naval ships, and many shells and moulds with special curved surfaces, complex cavities and holes, etc. for example, with the ordinary three-axis numerical control, because the pose angle of the cutter relative to the workpiece cannot be changed in the process of machining, there may be interference or under machining (that is, the machining can not be achieved) when machining some complex free-form surfaces. When machining with five axis linkage machine tool, the tool / workpiece pose angle can be adjusted at any time in the process of processing, so that the interference of tool and workpiece can be avoided and all machining can be completed at one time;

2、 It can improve the machining accuracy, quality and efficiency of free-form surface. For example, ball end milling cutter is often used when machining complex curved surface by three-axis machine tool. Ball end milling cutter is formed by point contact, and the cutting efficiency is low. Moreover, the pose angle of cutter / workpiece cannot be adjusted in the process of machining. Generally, it is difficult to ensure that the best cutting point on the ball end milling cutter (i.e. the highest linear speed point on the ball head) is used for cutting, and it is possible that the cutting point falls on the ball end cutter, and the line speed of the ball end cutter is equal to The situation on the center line of rotation of zero. However, if the five axis machine tool is used, because the position and attitude angle of the tool / workpiece can be adjusted at any time, this situation can not only be avoided, but also the best cutting point of the tool can be made full use of at all times, or the ball end milling cutter formed by point contact can be replaced by the spiral end milling cutter formed by point contact, and even milling can be carried out by further optimizing the pose angle of the cutter / workpiece In order to obtain higher cutting speed and line width, higher cutting efficiency and better surface quality can be obtained.

3、 Advantages of mold processing. In the traditional mold processing, the vertical machining center is generally used to complete the milling of the workpiece. With the continuous development of mold manufacturing technology, some weaknesses of the vertical machining center become more and more obvious. Ball end milling cutter is widely used in modern mold processing. The advantages of ball end milling cutter in mold processing are obvious. However, if the vertical machining center is used, the linear speed of the bottom surface is zero, so the bottom surface finish is very poor. If the four or five axis linkage machine tool processing technology is used to process the mold, the above shortcomings can be overcome. The use of five axis machine tool processing mold can quickly complete the mold processing, fast delivery, better guarantee the mold processing quality, make the mold processing easier, and make the mold modification easier

How to store CNC machining parts

In order to process the surface that meets the technical requirements of the regulations on a certain part of the CNC machining parts, before machining, make sure that the CNC machining parts occupy a certain precise position on the machine tool related to the equipment. This process is usually called “positioning” of CNC machining parts. After CNC machining parts are positioned, due to the effect of cutting force and gravity in the machining process, the positive organization should be selected to “clamp” the workpiece to keep its positive position fixed. The whole process of workpiece from “positioning” to “clamping” is called “installation”. How to store CNC machining parts

The installation of CNC machining parts is an important issue in mold processing. It not only directly affects the machining accuracy, the speed and stability of workpiece installation, but also affects the production rate. In order to ensure the relative position accuracy between the machined surface and its design datum, the design datum of the machined surface should occupy an accurate position relative to the machine tool when installing CNC machined parts. When the workpiece is installed, its design datum must coincide with the axis line of the machine tool spindle.

When machining parts on different machine tools, there are different installation methods. The installation methods can be summarized as direct alignment method, marking alignment method and fixture installation method.

The reason of hardware processing precision variation

In the process of processing, there will be many factors affecting our processing effect, but with the development of our science and technology, now there are many problems can be easily solved. In the industrial industry, our hardware processing application is very extensive, at the same time, there are many fault problems, but if we want to solve the problem, we must first find the cause of the problem What is the reason, so let’s understand what causes the precision of precision hardware processing to become worse?

The machining accuracy of parts is poor. Generally speaking, if the dynamic error between shafts is not adjusted properly or the shaft drive chain changes due to wear, the accuracy of parts will be affected. Generally speaking, the accuracy caused by the error of this type can be adjusted again. And if the error is too large to alarm, it is necessary to check the servo motor to see if its speed is too high.
When the machine tool is running, the overshoot will also affect the processing accuracy, which may be due to the short acceleration and deceleration time, and appropriately extending the change time. Of course, it is also very likely that the link between the lead screw and the servo motor is loose.
Due to the roundness out of tolerance caused by the linkage of two shafts, the axial deformation of the circle formed by mechanical adjustment, the gap compensation of the shaft lead screw is not correct, or the shaft positioning occurs offset, which may affect the precision of fine parts.

Prevention of gnawing die in stamping process

In the processing engineering, we will encounter a variety of problems, which must be solved as soon as possible, otherwise it will affect our work, so it is not good, some problems will also affect the quality of processing, not hit the mold damage and so on, so we will understand how to prevent the phenomenon of gnawing die in the stamping process?

(1) In terms of design and equipment, if the punch is not fixed properly, such as fixing the punch by chiseling, the punch may become loose. If the low melting point alloy is used for pouring, the punch may become loose. If the blanking force is large and the root of punch is not hardened and the punch is subjected to excessive lateral force, the punch may become loose.

(2) Mold manufacturing

Vertical or no punch mounting.
The assembly of upper and lower templates, fixed plates, convex and concave dies are not parallel to each other.
The blanking clearance is not uniform.
The punch fixation did not meet the design requirements.

(3) Mold use

Repeated blanking or overlapping blanking, that is, one blank is punched twice or several blanks are stacked together for blanking.
The scraps or blanking parts left on the mould are not cleaned in time.

(4) Mold maintenance

The parts of the die have great wear, such as the guide parts wear, resulting in excessive fit clearance and not timely repair.
The mold is loose in maintenance and assembly.

The above points are how to prevent the phenomenon of gnawing die in the process of stamping. When dealing with the problems, we must pay attention to some details to avoid causing greater hidden dangers. Let’s talk about it today. If you want to know more information, please visit Dongguan machining website for details.

Machining to prevent deformation

No matter what kind of work, there will be some problems in the process. These problems are not big, but they will affect our work efficiency and product quality. So we not only need to solve the problems in time, but also learn how to prevent the occurrence of faults. Next, we will learn how to prevent the deformation of workpiece in the machining process of Dongguan?

The deformation is directly proportional to the shape complexity, length width ratio and wall thickness, and is directly proportional to the rigidity and stability of the material. Therefore, the influence of these factors on workpiece deformation should be reduced as much as possible when designing parts. Especially in the structure of large parts, the structure should be reasonable. Before processing, the hardness and porosity of the blank should be strictly controlled to ensure the quality of the blank and reduce the deformation of the workpiece.

When the workpiece is clamped, the correct clamping point should be selected first, and then the appropriate clamping force should be selected according to the position of the clamping point. Therefore, the clamping point should be consistent with the support point as much as possible, so that the clamping force acts on the support. The clamping point should be as close to the machining surface as possible, and the position where the force is not easy to cause clamping deformation is selected.

Dongguan machining

When there are several directions of clamping force acting on the workpiece, the order of clamping force should be considered. For contacting the workpiece with the support, the clamping force should act first, and it is not easy to be too large. For the main clamping force balancing the cutting force, the stress acts on the last. Secondly, the contact area between workpiece and fixture should be increased or axial clamping force should be used. Increasing the rigidity of parts is an effective way to solve the problem of clamping deformation. However, due to the shape and structure characteristics of thin-walled parts, it has low rigidity. In this way, under the action of clamping force, deformation will occur.

Increasing the contact area between workpiece and fixture can effectively reduce the deformation of workpiece during clamping. For example, when milling thin-walled parts, a large number of elastic pressing plates are used to increase the stress area of the contact parts; when turning the inner diameter and outer circle of the thin-walled sleeve, whether using simple opening transition ring, or using elastic mandrel, whole arc claw, etc., the contact area of workpiece clamping is increased. This method is beneficial to carrying the clamping force and avoiding the deformation of parts. The use of axial clamping force is also widely used in production. The design and manufacture of special fixture can make the clamping force act on the end face, which can solve the bending deformation of workpiece caused by thin wall and poor rigidity.

Five axis CNC machining becomes simple

CNC processing is a relatively complex work, which requires professionals to operate. It is not allowed to work without professional training. So many teachers said that because the processing steps are too complex, sometimes a lot of time will be wasted, so they studied some time-saving skills. Now we will learn how to make five Axis CNC machining become a simple way!

(1) Area to be processed and processing sequence. This step is based on the complexity of the component shape, and is often the most easily inspired by skilled mechanics.

(2) What shape should the tool path have in the machining area? Should the tool be allowed to cut in front of back or up and down according to the parameterized lines of the surface, and the surface boundary should be used as a guide?

(3) How to guide the tool axis to match the tool path is very important for the quality of surface finish and the use of short hard tools in narrow spaces. Mold manufacturers need to have adequate control of the tool, including the rake angle when the tool is tilted. In addition, many turrets must be considered when turning the turret. For example, there is a limit to the degree of rotation of milling / turning machines.

(4) How to change the cutting path of the tool? How to control the displacement of the tool due to reset or generated at the starting point of the tool path and the displacement that the tool must produce between the processing areas? The displacement generated during the conversion process is very important in the mold production, which can eliminate the evidence line and the trace generated by the tool (it can be removed by manual polishing afterwards)

报错笔记

Installation environment requirements of CNC machining center

In fact, no matter what the equipment is, the installation environment is very important. It’s not to say that the environment is particularly good, but it can’t be too bad. For example, the floor can’t be uneven. So let’s learn about the requirements of CNC machining center on the installation environment?

Location requirements

It should be far away from the vibration source and direct sunlight. If there is a seismic source nearby, an earthquake proof trench should be set up.

Temperature and humidity

The optimal processing temperature of CNC machining center is below 30 ℃. If the ambient temperature and humidity are too high, the service life of the control system components may be reduced. If the ambient humidity is too high, it may lead to the short circuit and fault of the integrated circuit board.

Voltage and current control

There are many processing equipment in the workshop, which will cause excessive fluctuation of the power grid. We need to control the voltage and current within the allowable range of the machining center and keep it stable, otherwise the work of the system may be affected. The power supply shall be 380V ± 10%, three-phase AC.

As we all know, after the installation of CNC machining center, the acceptance still needs to be done, because the acceptance of CNC machining center directly affects the equipment put into use of the manufacturer. The general factory acceptance standard is to directly carry out the workpiece processing test. In fact, after the workpiece processing test, it can be basically determined that the key parts of the machining center meet the standards, and in the case of normal use There is no problem. About CNC machining center spindle performance inspection is what?

Select low, medium and high speed. The main shaft starts 5 times in a row, then stops the operation to check the flexibility and reliability of its action. At the same time, check whether the power display on the load meter meets the requirements.
It can input data manually, so that the spindle gradually increases from low speed to the maximum allowable speed. Check whether the speed is normal, the general allowable error should not exceed ± 10%. While checking the spindle speed. Observe whether the noise, vibration and temperature rise of the spindle are normal. The temperature rise of the spindle is 15 “C after running at high speed for 2 h.
In order to check the flexibility and reliability of the spindle action, the spindle can be stopped accurately and operated continuously for more than 5 times.

Advantages of CNC machining

CNC machining refers to NC machining, which is a method of controlling mechanical movement and machining process by using digital information.

The traditional mechanical processing is operated by hand with ordinary machine tools. When machining, the metal is cut by hand shaking the mechanical cutter, and the accuracy of products is measured with caliper and other tools by eyes. However, the traditional manual processing is far from meeting the production requirements.

Therefore, the emergence of CNC machining provides the possibility for the standardization, accuracy and efficiency of machining, and CNC machining is also brilliant in the radiator industry.

In order to obtain high-quality products, ordinary processing technology must have complex processes, such as the selection of cutting route, shape and size of radiator panel, and the force used for processing on different materials is not the same, so in order to reduce the error in the specific operation, the efficiency must not be high.

However, with CNC processing, all processes are first arranged and designed, incorporated into the processing program, simplify the process and carry out each step orderly, without affecting the efficiency of human factors, greatly improving the production efficiency of manufacturers.

Nowadays, many businesses not only have high requirements for the heat dissipation performance of the radiator, but also have the pursuit on the beauty of the appearance, and the application of CNC processing can achieve compatibility between the two.

CNC machining quality is stable, the finished product surface texture is clear, metal texture is strong, smooth, no scratch, no missing angle, and the heat dissipation coefficient strength of raw materials will not be changed under precision processing.

Manufacturers can adjust the specific process in the process to enhance its heat dissipation performance, such as Zhigao’s oxidation, wire drawing, paint baking, sand blasting and other processes can be carried out under the CNC operation.

It is believed that friends who have been in contact with radiators are not unfamiliar with fin shaped radiators and sunflower radiators. In fact, CNC processing is indispensable to the production of radiators with special requirements on the appearance.

Traditional processing technology for special, complex parts can not achieve high-efficiency and fine production, and with the help of numerical control processing, you only need to set the programming to process the desired surface, and the finished product is firm and durable, accurate and tight.

Processing standard of non standard parts

With the development of our country, now people’s living conditions are more and more superior, people’s requirements for more quality of life have also been improving, of course, with the improvement of our work standards, in fact, no matter what industry, in this society, is always in progress, if the world of the jungle, if not progress, it will certainly be eliminated, so below Let’s learn about the standard of non-standard parts processing?

The first is to take the cylinder as an example: for example, the cylinder diameter has strict requirements, and the positive and negative errors are within the required qualified parts range, otherwise, they are all unqualified parts; if the diameter of the embedded cylinder is too large and exceeds the allowable error range, the actual diameter will be too small and exceed the lower limit of allowable negative error value, which will lead to too loose insertion. There are problems of instability.

Second, these are not qualified products, or the cylinder length is too long or too short, exceeding the allowable error, are all unqualified products, which will inevitably lead to increased costs.

The third and second is the advanced non-standard precision parts processing equipment and testing equipment, advanced processing equipment makes the precision parts processing easier, higher precision and better effect.