Category Archive CNC Technology

Matters needing attention before CNC machining

① Cutter path sequence: large cutter curved surface grooving cutter path opening, small cutter contour contour cutter opening rough, large cutter (ball cutter) parallel milling cutter path smooth cutter, small cutter parallel milling cutter path smooth cutter. When the front die is manufactured, there is usually a matching copper male, mainly with a rough cutting path, supplemented by a local curved surface smooth knife.

② With parting surface and pillow surface, it is necessary to add time together. The parting surface pillow surface shall be machined in place without allowance, and the allowance of 0.2-0.5 shall be reserved at the cavity for spark. If only the young male is needed, a margin of 0.3 can be left. The allowance is 0.5. The allowance of 0.1 can be reserved at the position of collision and wear of front die, which is used for front and rear die matching.

③ When the diameter is too small, it is easy to break and snap the knife. It should also be selected as far as possible.

CNC machining

④ The tool path size in curved surface machining is calculated according to the moving track of the tool center axis, that is, the actual machining area is one more tool radius value than the one side of the selected tool path size constraint box, so the parameters of tool path size constraint frame should be set reasonably. To prevent the processing scale beyond the practical processing needs.

⑤ The data of the front die is hard. Check carefully before processing to reduce mistakes and not easy to weld!

Precautions after CNC machining

① Sequence of tool path of back die: large tool surface grooving, cutter path opening, small tool constraint scale, curved surface grooving and opening, angle cleaning, large cutter (ball cutter) parallel milling path smooth surface, small cutter (ball cutter) parallel milling path constraint scale, angle cleaning, smooth cutter, flat cutter and other high profile tool path angle cleaning.

② The data of the back die is the same as that of the front die, and the round nose knife (handle) should be used as far as possible.

Some skills in NC machining

How to prepare NC programming

After determining the processing technology, the following should be understood before programming:

1、 Workpiece clamping method;

2、 Workpiece rough blank size – determine the processing range or whether multiple clamping is required;

3、 Workpiece material: select the tool for processing;

4、 What are the tools in stock? Avoid modifying the program due to the lack of this tool during processing. If you have to use this tool, you can prepare it in advance.

What are the programming principles for safe height setting?

Precision machining

Safety height setting principle: generally higher than the highest height on the island. Or set the programming zero point to the highest plane to avoid the risk of knife collision as much as possible.

Why do tool paths need post-processing?

Since different machine tools can identify different address codes and NC program formats, it is necessary to select the correct post-processing format for the machine tools to ensure that the program can run.

Reasonable selection of cutting parameters

For high efficiency metal cutting, the material to be processed, cutting tools and cutting conditions are the three major elements. They determine the processing time, tool life and machining quality. The economical and effective machining method must be the reasonable choice of cutting conditions.

The three elements of cutting conditions: cutting speed, feed rate and cutting depth directly lead to tool damage. With the increase of cutting speed, the tool tip temperature increases, resulting in mechanical wear, chemical wear and thermal wear. If the cutting speed is shortened by 2%, the tool life will be increased.

The relationship between feed condition and tool wear is very small. However, when the feed rate is large, the cutting temperature increases and the wear is large. It has less effect on cutting tool than on cutting speed. Although the influence of cutting depth on the tool is not as great as the cutting speed and feed speed, when the cutting depth is small, the hardened layer of the material to be cut will also affect the tool life. The user should select the cutting speed according to the processing material, hardness, cutting state, material type, feed rate, cutting depth, etc.

On this basis, the most suitable process conditions were selected. Regular and stable wear is the ideal condition for service life. Don’t want to work at the bottom, want to get rid of the status quo.

But in practice, the choice of tool life is related to tool wear, change of machining size, surface quality, cutting noise, processing heat and other factors. When determining the processing conditions, it is necessary to study according to the actual situation. For difficult to machine materials, such as stainless steel and heat resistant alloy, coolant or rigid blade can be used.

Universal threading method for CNC machining

There are generally four ways to process thread on CNC lathe. There are four cutting methods: direct cutting, oblique cutting, left and right cutting and rough cutting.

1. Direct development method; as shown in Fig. 1 (the depth of thread turning tool intermittently feeding to the teeth), when the trapezoidal thread is processed (all three parties are involved in cutting), the chip removal is difficult (increasing the cutting force and cutting heat), the tool tip of severe wear (too much feed), and the possible phenomenon of thorn. Obviously, machining large pitch trapezoidal thread and worm is not advisable.
2. Oblique method; as shown in Figure 2 (thread turning tool is the phenomenon that the Federal Reserve uses the depth of helical teeth and intermittent way along the direction of tooth angle) (when trapezoidal thread processing is in this way (thread turning tool always has only one edge to participate in cutting (so the chip discharge is relatively smooth) (the skill of force and thermal conditions is improved (not easy to cause tool turning).
3. Left and right cutting mode; as shown in Fig. 3 (the thread turning tool enters the tooth depth through the staggered gap in the direction of tooth profile angle).

CNC machining

1. Groove cutter rough groove cutting method: as shown in Fig. 4, (this method first uses slotting cutter to rough groove (then uses trapezoidal thread turning tool to process both sides of thread).

Characteristics and processing method of worm and trapezoidal thread with large pitch

The cutting resistance of turning worm and large guide wire (either oblique or left-right cutting mode) is very high (previously only high-speed steel turning tool is used for low-speed turning (production efficiency is very low). In order to be able to use carbide tools, I had to find a way to reduce the cutting depth of the blade.

The groove of thread or worm is divided into several layers (converted into several shallow trapezoidal grooves) for cutting.

Since the depth of the left cutting groove remains unchanged (the tool only needs to do left direction!) and feed along the guide rail direction (thus organically combining the left and right cutting methods with the oblique cutting method), the cutting edge can be cut once (and the cutting margin can be effectively controlled), which can guarantee the surface quality and tool life

The processing technology of CNC lathe is similar to that of ordinary lathe. However, as CNC is a kind of clamping, continuous automatic processing completes all turning process, so attention should be paid to the following aspects.

1. Reasonable selection of cutting parameters

For efficient metal cutting, machining materials, cutting tools and cutting conditions are the three main factors. These factors determine the processing time, tool life and machining quality. An economical and effective machining method must be a reasonable choice of cutting conditions.

Three factors of cutting conditions: cutting speed, feed and cutting depth directly lead to tool damage. With the increase of cutting speed, the tool tip temperature increases, resulting in mechanical, chemical and thermal wear. Increasing the cutting speed will reduce the tool life by half.

The relationship between feed condition and tool wear is very small. However, when feeding, the cutting temperature increases and the wear occurs. It has less effect on the tool than on the cutting speed. Although the influence of cutting depth on cutting speed and feed rate is not as great as that of cutting speed and feed rate, the hardened layer produced by cutting material will also affect the tool life when cutting at small cutting depth.

The user should select the cutting speed according to the material, hardness, cutting state, material type, feed rate and cutting depth. The following table:

According to these factors, select the most suitable processing conditions. The ideal state is to wear regularly and stably to reach the service life.

But in practice, the choice of tool life is related to tool wear, size change, surface quality, cutting noise, processing heat and so on. When determining the processing conditions, it is necessary to study according to the actual situation. For refractory materials such as stainless steel and heat resistant alloy, coolant or hard blade can be used.

1. Select a tool

1) The cutter with high strength and good durability shall be selected to meet the requirements of thick tooth turning, large back cutting and large feed.

2) Precision turning, select high precision, good durability tool, to ensure the machining accuracy requirements.

3) In order to reduce the tool change time and facilitate tool alignment, the machine clamping tool and the machine clamping tool should be used as far as possible.

CNC machining

1. Reasonable selection of fixture

1) Try to use general fixture to clamp workpiece and avoid using special fixture;

2) Parts positioning datum coincide to reduce positioning error.

1. Determine the processing route

Machining path is the exponential control of the tool path and direction relative to the part in the machining process.

1) Ensure machining accuracy and surface roughness;

2) The processing route should be shortened as much as possible to reduce the tool idle travel time.

1. Relationship between machining route and machining allowance

At present, it is not widely used in CNC lathe. Generally, the blank should be put on the surplus allowance, especially the allowance with forging and casting hard skin should be processed on the common lathe. If you must use CNC lathe processing, then you must pay attention to the flexible arrangement of the program.

1. Key points of fixture installation

At present, the connection between hydraulic chuck and hydraulic clamping cylinder is realized by pull rod. The critical point chuck of the hydraulic chuck is as follows: first, remove the lifting hand of the nut on the hydraulic cylinder, pull out the tube, and extract from the rear end of the shaft, and then put the chuck fixing screw on the raised hand, chuck can be removed.

The polished edge on the tool refers to a small part of the blade, which is worn along the side deviation direction behind the blade and parallel to the tool tip. The blade is mainly used for the second cutting after cutting edge cutting, which is equivalent to removing burrs and scars in the process of finishing. Its purpose is to improve the surface roughness of the workpiece, which is mainly used for the finishing of cutting tools.

Thread machining is one of the important applications of CNC machining center. The quality and efficiency of thread processing directly affect the quality of parts and the production efficiency of machining center.

With the improvement of CNC machining center performance and tool performance, the thread processing method is also constantly improved, and the accuracy and efficiency of thread processing are also gradually improved. In order to make the technical personnel reasonably choose the thread processing mode in the processing process, improve the production efficiency and avoid quality accidents, several thread processing methods commonly used in the CNC machining center are summarized as follows:

1. Tap processing method
2. Classification and characteristics of tap processing

Tapping is the most commonly used method for machining threaded holes, which is mainly applicable to the threaded holes with smaller diameter (d < 30) and lower hole position accuracy.

In the 1980s, the flexible development method was adopted for all threaded holes. That is to say, the tap was equipped with a flexible tapping chuck. The clamping and tapping chuck could compensate for the errors caused by the uneven rotation speed of the spindle due to the axial propulsion of the machine tool, so as to ensure the correct pitch.

Flexible tapping chuck has complex structure, high cost, easy damage and low processing efficiency. In recent years, the performance of CNC machining center has gradually improved, and the rigid tapping function has become the basic configuration of CNC machining center.

Therefore, rigid tapping becomes the main method of thread processing.

CNC machining

The rigid spring chuck is used to clamp the tap, so that the spindle enters the spindle, and the rotation speed is controlled by the machine tool to keep consistency.

Compared with the flexible tapping chuck, the spring chuck has the advantages of simple structure, low price and wide application. In addition to clamping taps, it can also clamp end mills, drills and other tools, which can reduce the cost of cutting tools. At the same time, the use of rigid tapping can carry out high-speed cutting, improve the efficiency of the machining center and reduce the manufacturing cost.

1. Determine the bottom hole of thread before tapping

The processing of thread bottom hole has a great influence on the service life of tap and thread processing quality. In general, the diameter of bottom hole drill is close to the upper limit of tolerance.

For example, if the diameter of the bottom hole of M8 threaded hole is Ф 6.7 + 0.27 mm, select some diameter of Ф 6.9 mm. In this way, the machining allowance of the tap can be reduced, the load of the tap can be reduced, and the service life of the tap can be improved.

1. Click Select

When selecting taps, the corresponding taps should be selected according to the different processing materials. Tool companies should produce different types of taps according to the different processing materials. Special attention should be paid to the selection.

Because the tap is very sensitive to the processed material relative to milling cutter and boring cutter. For example, using cast iron taps to process aluminum parts is easy to cause thread teeth, random thread and even broken tap, resulting in workpiece scrapping. Secondly, pay attention to the difference between through tap and blind tap. The guide rail at the front end of the through-hole tap is longer, and the chip removal is the front-end chip removal.

The front guide plate of the blind hole is short, and the chip removal is the rear guide plate. It is impossible to ensure the depth of thread processing by using through-hole tap to process blind hole. In addition, if a flexible tapping chuck is used, the diameter and width square of the tapping handle should be the same as that of the tapping chuck; the diameter of the rigid tapping tap handle should be the same as that of the spring sleeve. In short, only reasonable selection of taps can ensure the smooth processing.

Computer digital control technology, is what we call numerical control technology, for a variety of fields for different technical support and technical changes, but in the specified operation process, it will also ensure the development of modern technology and the realization of technology, but in the operation trend of specified functions, it will control different computer capabilities The process, especially the application of numerical control technology in CNC machining field, will carry out different development and technology utilization process, in which for the development trend of CNC machining industry, will carry out different function realization and technical support, to maintain different technical processing products.

In the process of the development of numerical control technology, before is the traditional type of mechanical processing, there is not too much technical support process. With more technological changes and innovation process, there are different processing and processing trends for technology, which will ensure the realization of different capabilities. Therefore, in the process of more operation and technology utilization, C can be used NC machining to carry out the specified process to achieve better processing technology utilization and control process, which in the process of using more technology, will be in accordance with different processes to carry out simple ability utilization and realization.

Then in the process of different technical support, the processing trend will get new capabilities. However, in the control process of different functions, different technologies and process changes will be obtained. Therefore, it will also get new CNC machining applied to different projects, to get more capacity changes and technology operation trend. So in the development of different numerical control technology, will be the designated process, to carry out a simple ability change process. For CNC machining

With the change of the times, our very products need to be processed to get the corresponding effect, and the processing method is also very good, not only to get that effect, CNC processing is one of them, so where are the advantages of CNC processing reflected?

① A large number of tooling is reduced, and complex tooling is not needed to process parts with complex shapes. If you want to change the shape and size of parts, you only need to modify the part processing program, which is suitable for the development and modification of new products.

② CNC machining has the advantages of stable machining quality, high machining precision and high repetition accuracy, which can meet the processing requirements of aircraft.

CNC machining

③ In the case of multi variety and small batch production, the production efficiency is higher, the time of production preparation, machine tool adjustment and process inspection can be reduced, and the cutting time is reduced due to the use of the best cutting amount.

④ It can machine complex surface which is difficult to process by conventional method, and even can process some parts which cannot be observed.

In the process of processing, there will be a variety of problems, these problems are often occurred, may be because we do not operate well in the process of operation, caused by CNC machining is the same, so what are the causes of CNC machining tool imbalance?

The main reason for CNC machining is that the tool design is asymmetric, there are defects in the tool body, and all the adjustment of the tool. The correct balance of the tool can significantly reduce noise and vibration, which increases the tool life and improves the accuracy consistency of parts.

The centrifugal force of CNC machining center is proportional to the square of velocity to amplify the vibration caused by unbalance. The vibration increase of CNC machining center caused by the machining center minimizes the service life of bearing bush, bearing, shaft, spindle and gear.

Before balancing the tool in CNC machining center, it is necessary to measure the unbalance and the angle position of each selected correction plane. These variables are measured on two general types of balancing machines: non rotating or gravity machines are used to measure single plane unbalance, while rotary or centrifuge is used to measure single plane or two plane unbalance.

After measuring the magnitude and angle of the unbalance in the correct plane, you can correct it by adding or removing material from the workpiece. For the components which are not tools, the most widely used material adding method of drilling center is welding counterweight on the components.

CNC (numerical control machine tool) is the abbreviation of computer numerical control machine tool. It is an automatic machine tool equipped with program control system. The control system can process and decode the program with control code or other symbol instructions logically, so that the machine tool can move and process parts. Today we’ll take a look at its characteristics.

The operation and monitoring of CNC machine tools are all completed in this CNC unit, which is the brain of CNC machine tools. Compared with ordinary machine tools, CNC machine tools have the following characteristics:

1、 High machining precision and stable machining quality;

2、 It can carry out multi coordinate linkage and process complex shape parts;

3、 When the machining parts are changed, only the NC program needs to be changed, which can save the production preparation time;

CNC is also called computer gong, cncch or CNC machine tool. In fact, it is a kind of name in Hong Kong. Later, it was introduced into the Pearl River Delta of the mainland. It is actually a CNC milling machine. In Guangzhou, Jiangsu, Zhejiang and Shanghai, there are people called “CNC machining center”. General CNC machining usually refers to precision machining, CNC machining lathe, CNC milling machine, CNC boring milling machine, etc. Today we will talk about the prospect of CNC processing industry.

As an industry widely used in the market for mold processing and production, with the development of market economy, the decline of demand and the increase of peer competition pressure, technological breakthrough or price war is urgent.

1、 From the technical reform, the future development center must make a breakthrough from the most basic technology, realize the multi-directional upgrading from the mechanical and operational aspects, and achieve the technical update of the industry. Only with unique technology can we better cope with the future competition.

2、 In terms of service improvement, the competition in the industry is not only in technology, but also in service. Service is the relationship. If the service is done well, customers will continue to choose cooperation. Therefore, in the limited time, we should improve the service in essence.