Monthly Archive September 27, 2020

With the continuous development of the processing industry, the things we use need to be processed to complete, and the processing needs to be used to the machine to reduce the defects of products. CNC parts processing is one of them. So what kind of consequences will be caused to the parts if the CNC machining is particularly rough?

1. Influence on wear resistance: the rougher the machining surface of CNC products is, the smaller the effective contact area between matching surfaces is, the greater the pressure is, and the greater the friction resistance is, the faster the wear is.
2. Affect the stability of the fit: for the clearance fit, the rougher the surface is, the easier it is to wear, making the intermediate gap gradually increase during the working process; for the interference fit, due to the micro convex peak being flattened during assembly, the practical effective interference is reduced and the connection strength is reduced.
3. Influence on fatigue strength: there are large wave troughs on the surface of rough parts, which are sensitive to stress concentration like sharp corner notches and cracks, thus affecting the fatigue strength of parts.
4. Affect the corrosion resistance: rough surface of parts, easy to make corrosive gas or liquid penetrate into the inner layer of metal through the micro Valley on the surface, forming external corrosion.

CNC parts processing in Dongguan

1. Affect the sealing: rough surfaces can not fit tightly, and gas or liquid leak through the gap between contact surfaces.
2. Influence on contact stiffness: contact stiffness is the ability of part separation surface to resist contact deformation under the action of external force. The stiffness of a machine depends largely on the contact stiffness between the parts.
3. Affect the measurement accuracy: the surface roughness of the measured surface of the part and the measuring surface of the measuring tool will directly affect the measurement accuracy, especially in the fine measurement.

With the rapid development of industry, there are many CNC parts processing around us, which is enough to prove that the development prospect of this industry is still OK, otherwise there will not be so many in use. So in the process of operation, many steps are very important. What are the effective methods of CNC machining tool setting operation?

1. Jog the tool setting hair

Press the zero point (z) of the initial tool, and then press the zero point and Z key on the surface of the designed tool to clear the initial position of the workpiece, and then press the zero point and Z key to get the initial position of the tool. Determine the initial position of each cutter in turn, and then adjust to the accurate design position (starting point) after trial processing. This method can be operated easily without any auxiliary tools, but it takes a long time. Especially, the tool must be readjusted once every grinding.

1. Tool setting instrument

Now many lathes are equipped with tool setting instrument. The error caused by measurement can be avoided by using the tool setting instrument, which greatly improves the accuracy of tool setting. Because the tool setting instrument can automatically calculate the difference between the length and width of each knife, and store it in the system. When processing other parts, only the standard tool is needed, which greatly saves time. It should be noted that there is no standard tool for tool setting with the tool setting instrument. When setting the tool, first set the standard tool. Its disadvantage is that the tool setting instrument needs to be equipped with auxiliary equipment for tool setting instrument, which has high cost and laborious loading and unloading.

1. Use CNC tools

After the initial positioning of CNC machining tools, wear occurs after cutting for a period of time and needs to be sharpened. After grinding, the position of the re installed tip of the common tool has changed, and it needs to be re aligned. The characteristic of CNC tool is that the manufacturing accuracy of the tool is high, and the repeated positioning accuracy after the blade is rotated is about 0.02mm, which greatly reduces the tool setting time. At the same time, the blade is coated with metal layer (SiC, tic, etc.) greatly improves its durability, but the cost is also a little high.

1. Use the tool setting block to set the tool, and use the self-made tool setting method

The simple tool block made of plastic and plexiglass can easily realize the repeated positioning after tool grinding, but the positioning accuracy is poor, which is usually 0.2 ~ 0.5mm. Single tool is a fast positioning method, and then it can be adjusted quickly and conveniently.

With the improvement of the performance of CNC machining center and the improvement of cutting tools, the method of thread processing is constantly improved, and the accuracy and efficiency of thread processing are also gradually improved. Thread processing is one of the most important applications of CNC machining. The quality and efficiency of thread processing will directly affect the machining quality of parts and the production efficiency of machining center. In order to enable the process personnel to reasonably choose the thread processing method in the processing, improve the production efficiency and avoid the quality accident, several thread processing methods commonly used in CNC machining are summarized as follows:

1. Tap processing method

1.1 classification and characteristics of tap processing

The tap is the most commonly used processing method for threaded hole, which is mainly applicable to the small diameter (d < 30) and low accuracy requirement of hole position.

In the 1980s, the flexible tapping method was adopted for the threaded hole, that is, the flexible tapping chuck was used to clamp the tap, and the tapping chuck could be used to compensate the feed error caused by the machine tool’s axial feed and spindle speed, 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 has gradually improved, and the rigid tapping function has become the basic configuration of CNC machining.

Therefore, rigid tapping has become the main method of thread processing.

In other words, the rigid spring chuck is used to hold the tap, and the spindle feed and spindle speed are controlled by the machine tool.

Compared with the flexible tapping chuck, the spring chuck has the advantages of simple structure, low price and wide application. In addition to the tap, it can also clamp the end mill, drill and other tools, which can reduce the cost of the tool. At the same time, the use of rigid tapping can make high-speed cutting, improve machining efficiency and reduce manufacturing costs.

1.2 the bottom hole of thread before tapping

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

For example, the diameter of the bottom hole of the M8 thread hole is Ф 6.7 + 0.27mm, and the diameter of the drill bit is selected to be Ф 6.9mm. 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.

1.3 selection of taps

When selecting taps, first of all, the corresponding taps must be selected according to the processed materials. The tool company produces different types of taps according to the different processing materials, and 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 taps for processing cast iron to process aluminum parts is easy to cause thread missing, thread disorderly and even tap breaking, resulting in workpiece scrapping. Secondly, we should pay attention to the difference between the through-hole tap and the blind hole tap. The front-end guide of the through-hole tap is longer, and the chip removal is the front row chip. The leading edge of the blind hole is short, and the chip removal is the back row chip. The processing depth of thread can not be guaranteed when the blind hole is machined with through-hole tap. Furthermore, if flexible tapping chuck is used, the diameter of tap shank and the width of four sides should be the same as that of tapping chuck; the diameter of shank of rigid tapping should be the same as that of spring jacket. In short, only reasonable selection of taps can ensure the smooth processing.

1.4 NC programming of tap machining

The programming of tap machining is simple. Now the machining center generally solidifies the tapping subroutine, which only needs to assign the parameters. However, it should be noted that the meaning of some parameters is different due to different NC systems and different formats of subroutines.

For example, Siemens 840C control system, its programming format is: g84x_ Y_ R2_ R3_ R4_ R5_ R6_ R7_ R8_ R9_ R10_ R13_。 In programming, only these 12 parameters need to be assigned.

1. CNC thread milling method

2.1 features of thread milling

Thread milling is to use thread milling tool, machining center three axis linkage, namely x, Y axis arc interpolation, Z axis linear feed milling method.

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

(1) high speed, high efficiency and high precision. The cutting tool material is generally cemented carbide material, and the cutting speed is fast. The manufacturing precision of cutting tool is high, so the precision of thread milling is high.

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

(3) milling is easy to chip removal and cooling. Compared with the tap, the cutting condition is better, especially suitable for the screw thread processing of difficult to machine materials such as aluminum, copper, stainless steel, etc,

It is especially suitable for thread processing of large parts and components of valuable materials, which can ensure the quality of thread processing and the safety of workpiece.

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

2.2 classification of thread milling tools

Thread milling tools can be divided into two types, one is the machine clip type carbide blade milling cutter, the other is the integral cemented carbide milling cutter. It can be used for machining holes with thread depth less than blade length and holes with thread depth greater than blade length. Integral cemented carbide milling cutter is generally used for machining holes with thread depth less than tool length.

2.3 NC programming of thread milling

The programming of thread milling tool is different from that of other tools

With the improvement of the performance of CNC machining center and the improvement of cutting tools, the method of thread processing is constantly improved, and the accuracy and efficiency of thread processing are also gradually improved. Thread processing is one of the most important applications of CNC machining. The quality and efficiency of thread processing will directly affect the machining quality of parts and the production efficiency of machining center. In order to enable the process personnel to reasonably choose the thread processing method in the processing, improve the production efficiency and avoid the quality accident, several thread processing methods commonly used in CNC machining are summarized as follows:

1. Tap processing method

1.1 classification and characteristics of tap processing

The tap is the most commonly used processing method for threaded hole, which is mainly applicable to the small diameter (d < 30) and low accuracy requirement of hole position.

In the 1980s, the flexible tapping method was adopted for the threaded hole, that is, the flexible tapping chuck was used to clamp the tap, and the tapping chuck could be used to compensate the feed error caused by the machine tool’s axial feed and spindle speed, 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 has gradually improved, and the rigid tapping function has become the basic configuration of CNC machining.

Therefore, rigid tapping has become the main method of thread processing.

In other words, the rigid spring chuck is used to hold the tap, and the spindle feed and spindle speed are controlled by the machine tool.

Compared with the flexible tapping chuck, the spring chuck has the advantages of simple structure, low price and wide application. In addition to the tap, it can also clamp the end mill, drill and other tools, which can reduce the cost of the tool. At the same time, the use of rigid tapping can make high-speed cutting, improve machining efficiency and reduce manufacturing costs.

1.2 the bottom hole of thread before tapping

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

For example, the diameter of the bottom hole of the M8 thread hole is Ф 6.7 + 0.27mm, and the diameter of the drill bit is selected to be Ф 6.9mm. 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.

1.3 selection of taps

When selecting taps, first of all, the corresponding taps must be selected according to the processed materials. The tool company produces different types of taps according to the different processing materials, and 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 taps for processing cast iron to process aluminum parts is easy to cause thread missing, thread disorderly and even tap breaking, resulting in workpiece scrapping. Secondly, we should pay attention to the difference between the through-hole tap and the blind hole tap. The front-end guide of the through-hole tap is longer, and the chip removal is the front row chip. The leading edge of the blind hole is short, and the chip removal is the back row chip. The processing depth of thread can not be guaranteed when the blind hole is machined with through-hole tap. Furthermore, if flexible tapping chuck is used, the diameter of tap shank and the width of four sides should be the same as that of tapping chuck; the diameter of shank of rigid tapping should be the same as that of spring jacket. In short, only reasonable selection of taps can ensure the smooth processing.

1.4 NC programming of tap machining

The programming of tap machining is simple. Now the machining center generally solidifies the tapping subroutine, which only needs to assign the parameters. However, it should be noted that the meaning of some parameters is different due to different NC systems and different formats of subroutines.

For example, Siemens 840C control system, its programming format is: g84x_ Y_ R2_ R3_ R4_ R5_ R6_ R7_ R8_ R9_ R10_ R13_。 When programming, only these 12 parameters need to be assigned

There are several common technologies for making hand board model: CNC hand board processing, 3D printing hand board, silicone compound mold hand board, sheet metal hand board, low pressure perfusion hand board, etc. Today, we will briefly describe the steps and advantages of CNC processing.

Hand model, many people also known as the first board model. Generally speaking, after the design of an industrial product is completed, it is not immediately put into production. Instead, a small number of models should be made according to the drawings. The purpose is to see the sample of the finished product in advance. If it is not satisfied, modify the drawing, and then start batch manufacturing after there is no objection. This small number of models is the hand model in the mouth.

The steps of CNC hand board processing are as follows:

1) Discuss CNC processing price and delivery time, sign processing contract.

2) Analyze the part drawing and product assembly drawing, and analyze the process of parts.

3) Select the blank.

4) CNC programming.

5) Determine the machining allowance of each process, calculate the process size and tolerance.

6) Determine the equipment and tools, fixtures, measuring tools and auxiliary tools used in each process.

7) Determine cutting parameters and man hour quota

The following machining center for you to introduce the machining center disordered tool solution (solve).

1. This situation may be caused by the upper and lower machining ports of the machining center. The operator will use the reset button to change the calculation method or simply press the emergency stop button.
2. At the same time, the typical PLC program of machining center (PLC programming is an electronic system of digital operation, specially designed for application in industrial environment) refreshes the tool list after the modification. Your program should be like this, but after you have a problem with the tool cover, you just need to put the knife down. After repairing, I think there should be no problem on the original tool holder, and there will be a confused knife.
3. Communicate with the manufacturer you purchased. If the manufacturer has after-sales service or after-sales maintenance, you can ask their technicians to check the security. In addition, do not operate the keyboard on the operation panel of the machining center after the tool is out of order. If you do not know PLC, please try to use external force to help the tool sleeve complete the action. Pay attention to safety during operation. Try to get the machining center tool library itself to complete the entire M6 cycle, so it certainly won’t be messy.
4. During normal tool change, the tool change process is stuck due to insufficient air pressure. After manual tool magazine reset (reset), the tool magazine may be disordered.
5. When the manipulator of machining center changes tool, the operator presses the reset key or emergency stop key. As a result, the tool change is terminated unexpectedly and the tool magazine may be disordered.
6. Due to the damage of the mechanical structure of the machine tool (damage), or the loss of the parameters of the CNC system, disordered failure caused by the phenomenon of tool disorder.

Processing method for disordered tools in tool magazine of machining center:

1) Check whether the switch of the counter is loose and whether there is knife jamming. If there is, it is easy to mess the knife.

2) Check your clamping loose tool signal, tool sleeve up and down signal, spindle position signal.

3) If there is a shift function between high and low gears, check the low and high gear signals. When an alarm appears, see which signal does not arrive or is caused by a flicker. Another possibility is that the authorized t diagram is not strict.

4) If the machining center is used by others, ask them if they have adjusted the phase sequence of the forward and reverse motors of the magazine. If they do, the magazine can only rotate in one direction, so the tool magazine can not be found nearby and the magazine will be in disorder.

The so-called CNC machining is also known as CNC machining, which refers to a kind of processing which is operated by CNC machining operators after the programmer uses the computer to program the work order to be processed. There are three kinds of guide rails for CNC machining center. The differences between these three kinds of guides are quite big. Therefore, if you need to select the guide rails of CNC machining centers, it is better to have a detailed understanding of these three kinds of guides in advance, so that we can better select the guide rails for our CNC machining centers. The following is an introduction to the guide rails of CNC machining centers:

According to the motion track, the guide rail can be divided into linear motion guide rail and circular motion guide rail; according to the working nature, it can be divided into main motion guide rail, feed motion guide rail and adjustment guide rail; according to the friction property of contact surface, it can be divided into sliding guide rail, rolling guide rail and hydrostatic guide rail.

Slide guide

The sliding guide has the advantages of simple structure, convenient manufacturing, good stiffness and high vibration resistance. The traditional cast iron cast iron and cast iron quenched steel guide rail has the disadvantages of large static friction coefficient, dynamic friction coefficient changes with the speed, and the friction loss is large. It is easy to crawl at low speed / (1-60mm / min /), which reduces the positioning accuracy of moving parts. Therefore, it is not used in other CNC machine tools except economical CNC machine tools.

At present, most CNC machine tools use plastic guide, that is, a layer of plastic film soft belt composed of plastic and other chemical materials is pasted on the friction surface of moving guide rail.

There are two kinds of guide rail Plastics: PTFE soft belt and epoxy wear-resistant rail coating. The characteristics of plastic sliding guide are good friction characteristics, good wear resistance, smooth movement, good vibration damping and good technology.

Rolling guide

Rolling guide is to place ball, roller, needle and other rolling elements between the guide surfaces, so that the sliding friction between the guide surfaces becomes rolling friction. Compared with sliding guide rail, rolling guide has the advantages of high sensitivity and little difference between dynamic friction coefficient and static friction coefficient, so it can move stably, and it is not easy to crawl when moving at low speed; (high positioning accuracy, repeated positioning accuracy can reach 02um; low friction resistance, light movement, small wear, good accuracy retention and long service life. However, the anti vibration performance of rolling guide is poor, which requires high protection.

The rolling guide rail is especially suitable for the working parts of machine tools requiring uniform movement, sensitive motion and high positioning accuracy. This is the reason why rolling guide is widely used in CNC machine tools.

Hydrostatic guideway

There is an oil cavity between the two working faces of the hydrostatic guideway. After the lubricating oil with certain pressure is injected, the hydrostatic oil film can be formed, so that the working surface of the guide rail is in pure liquid friction, without wear, and has good accuracy retention; at the same time, the friction coefficient is also very low, which greatly reduces the driving power; at low speed, there is no creeping, the bearing capacity is large, and the rigidity is good; In addition, the oil has the function of vibration absorption and good vibration resistance. Hydrostatic guideway can be divided into hydrostatic guideway and aerostatic guideway.

Its disadvantage is that the structure is complex, there must be an oil supply system, and the cleanliness of the oil is required to be high. Hydrostatic guideway is widely used in machine tools. The hydrostatic guideway of CNC turret punch press can be divided into open type and closed type