September 2020 – Page 41 – CNC Machining & Turning, Milling, Metal parts

Causes of abnormal noise of spindle in CNC machining center

The spindle is the power auxiliary device of CNC machining center. The spindle drives the workpiece to rotate, which is used to process the workpiece of revolving 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 failure are the basic knowledge that operators and maintenance personnel of CNC machining center must master. When operating CNC machining center, the spindle will inevitably have some faults. What are the specific reasons?

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 drive spindle with variable speed gear, the main transmission spindle through belt drive, the spindle driven by dual motors and the spindle integrated by motor and spindle. No matter what type of spindle application, the common faults in use are as follows:

1. Overload.

Fault causes: excessive cutting amount, frequent positive and negative rotation, spindle motor failure, spindle drive device failure.

2. The spindle does not rotate

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

3. Spindle speed deviates from the command value

Fault causes: motor overload, problems with spindle speed command output from CNC system, fault of speed measuring device or disconnection of speed feedback signal.

4. Abnormal noise and vibration of spindle

CNC machining parts

Fault cause: it usually occurs in the process of deceleration, and the spindle drive device has problems, such as the regeneration circuit fault in AC drive.

CNC machining center spindle abnormal noise is the most operators will encounter things, to understand the cause of the failure, what measures should we take?

When the machining center is in use, customers often find that the main shaft is transmitted by belt. After a long time of use, there will be abnormal noise. When the forward transmission and reverse rotation are switched, there will be noise. According to years of assembly experience, most of the problems are belt, The belt tension at the connection between the servo motor and the spindle is too tight, which causes the belt to slip, and the spindle will make abnormal noise.

There is also a case that the tension of the belt connecting the servo motor is not enough, so the belt of the motor is too loose, which can be seen intuitively. When using the machining center to re chip, there will be slip and abnormal noise. The belt will be worn after the machining center is used for a long time, which is part of the cause of abnormal noise.

After CNC machining center spindle abnormal noise, some economical customers will choose to replace the transmission wallet. After the replacement, the belt drive gear does not match with the tooth type of the motor and the spindle, which can also make do with it. However, there will be a great abnormal noise during the use, which will seriously cause the wear and damage of the gear between the servo motor and the spindle. It is recommended to observe whether the model of the belt purchased and replaced is the same

How to deal with over cutting problem of CNC machining center

Milling cutter is used for machining plane, step, groove, forming surface and blocking workpiece on CNC machining center milling machine, which has a great influence on the quality of machined parts, so how to choose the appropriate milling cutter? What are the principles?

The milling cutter used in CNC machining center should be made of all cemented carbide, and the one used in general milling machine should be made of white steel. The hardness of white steel milling cutter and carbide milling cutter is relatively soft. Cemented carbide milling cutter has good thermal hardness, wear resistance, but poor impact resistance. If you drop the blade at will, it will be broken. Cemented carbide is made by powder metallurgy. Its hardness can reach about 90hra and its thermal property can reach 900-1000 degrees.

1. Number of teeth of milling cutter

When selecting a milling cutter, the number of teeth should be considered. For example, a thick tooth milling cutter with a diameter of 100 mm only needs 6 teeth, while a close tooth milling cutter with a diameter of 100 mm can have 8 teeth. The size of tooth pitch will determine the number of cutter teeth participating in cutting together during milling, and affect the stability of cutting and the requirement of cutting rate of machine tool.

2. Chip holding tank

Rough tooth milling cutter is often used for rough machining because it has a large chip groove. If the chip holding groove is not large enough, it will cause chip rolling difficulty or chip conflict with cutter body and workpiece. Under the same feed rate, the cutting load of coarse tooth milling cutter is larger than that of dense tooth milling cutter.

CNC machining of aluminum shell

3. 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 required power is not large. It can select the dense tooth milling cutter and select a larger feed rate.

4. Application of rough milling

In heavy load rough milling, excessive cutting force can make the machine tool with poor rigidity vibrate. This kind of vibration will cause the carbide blade to break and then shorten the tool life. The use of coarse tooth milling cutter can reduce the requirement of machine power.

The price of milling cutter used in CNC machining center is relatively expensive. The price of a face milling cutter with a diameter of 100 mm may cost 3000 yuan, so it should be selected steadily. Many people who have operated CNC machining center have encountered over cutting problem. How to deal with this situation?

The workpiece processing process of CNC machining center is no longer like the traditional processing equipment. It needs to continuously control the machine tool to finish, and control the functional parts of the machine tool to carry out messy and precise actions, and then finish the processing process with high precision and high efficiency. The programming of workpiece processing is the key of 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 over cutting. 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 machining program which is sure to occur overcutting. The system can announce the alarm signal in advance in the working process, so as to avoid the occurrence of over cutting. How to judge the cause of over cutting in CNC machining center?

CNC machining of aluminum parts

1. Overcutting in arc machining of machining center

In machining center, if the tool radius RD is too large and exceeds the required arc radius r r, it is likely to cause over cutting. The NC machining program is compiled according to the practical summary track of workpiece, without considering the motion track of tool in the process of practical machining. Because of the existence of tool radius, the tool practice track becomes thick and does not coincide with the programming track. In order to get the correct summary of the workpiece surface, it is necessary to set the tool radius compensation command between the tool path and the programming track. Otherwise, over cutting of workpiece will be inevitable.

2. The discrimination of cutting straight line

In CNC machining center, if the tool radius is too large, it is very likely to cause overcutting and then void the workpiece. It can distinguish the positive and negative of the scalar product of the programming vector and its corresponding correction vector.

What should be paid attention to when CNC machining workpiece

Contact with CNC machining center friends know that CNC machining process will appear oil leakage phenomenon, in fact, the location of oil leakage in the machining center is easy to see. Mainly because it is caused by accessories, or the CNC lathe cylinder oil leakage. If it’s accessories, maintenance is very simple. If it is a cylinder and then it is very troublesome, serious will lead to machine tool scrapping. Now let’s study the causes of oil leakage in CNC machining center?

CNC machining of aluminum shell

1. The oil change did not meet the requirements.

It often causes oil leakage in CNC machining center. There are three main problems in oil change. Firstly, for parts with high viscosity lubricating oil, if low viscosity lubricating oil is used randomly when changing oil, the sealing performance of corresponding box and shaft hole will be affected to some extent, and sometimes the sealing performance of these parts will be greatly reduced. Secondly, if the oil tank is not cleaned when changing the oil, the dirt in the oil tank may enter into the lubrication system, blocking the oil path and wearing the sealing parts, resulting in oil leakage. Third, when changing oil, the amount of oil is too much, especially in the parts with rotating parts, because of the agitation of rotating parts, it is more likely to cause oil spillage.

2. Improper selection and adjustment of lubricating system parts may cause oil leakage.

For example, CNC machining and maintenance personnel choose 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, 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, which will cause oil leakage.

In fact, it is not only the above points that cause oil leakage in CNC machining center. If we encounter similar problems in operation, we must do a good job of inspection and find out the causes in time to avoid unnecessary losses. After purchasing in the machining center, do a comprehensive inspection to see whether there are casting defects or parts damage. If so, 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, it is necessary to pay attention to the coordinate display of CNC system.

(4) Do not touch tools and chips of CNC milling machine by hand. The chip must be cleaned with a brush.

CNC processing route follows the following principles

CNC Lathe Feed processing route refers to the path through which the turning tool starts to move from the tool setting point (or the fixed origin of the machine tool), computer gong processing, Dongguan computer gong processing, high-speed CNC machining, mechanical parts processing, CNC processing, and then returns to the point and ends the processing program, including the path of cutting processing and the path of non cutting empty stroke such as tool cutting in and cutting out.

The feed path of finish machining is basically carried out along the contour sequence of the parts. Therefore, the key to determine the feed path is to determine the feed path of rough machining and idle stroke.

In CNC lathe processing, the determination of processing route generally follows the following principles.

① The accuracy and surface roughness of the workpiece to be processed shall be guaranteed.

② It can shorten the processing route, reduce the idle travel time and improve the processing efficiency.

③ Simplify the workload of numerical calculation and simplify the processing program.

④ For some reusable programs, subroutines should be used.

Advantages and disadvantages CNC machining has the following advantages:

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 The machining quality is stable, the machining precision is high, and the repetition precision is high, which can meet the processing requirements of aircraft.

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. The disadvantage of machining is the high cost of machine tools.

How to guarantee the stability of machining quality in CNC machining

Firstly, the number of tooling is greatly reduced, and complex tooling is not needed to process parts with complex shape. 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 The machining quality is stable, the machining precision is high, and the repetition precision is high, which can meet the processing requirements of aircraft.

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

The disadvantage of NC machining is the high cost of machine tools, which requires maintenance personnel to have a high level. Computer gong processing Dongguan computer gong processing high speed CNC machining CNC machining CNC machining CNC machining or CNC machine tool is actually a kind of name in Hong Kong. Later, it was introduced into the Pearl River Delta of mainland China. It is a kind of mechanical processing technology called “CNC machining center” in Guangzhou, Jiangsu, Zhejiang and Shanghai. It is a new type of processing technology. The main work is to compile processing programs, that is to say, the original From manual work to computer programming. Of course, manual processing experience is required.

brief introduction

In fact, it is CNC milling machine tool. In Guangzhou, Jiangsu, Zhejiang and Shanghai, there is a person called “CNC machining center”, which is an automatic machine tool equipped with program control system. CNC machine tool is the abbreviation of computer numerical control. It is an automatic machine tool controlled by program. The control system can logically process the program with control code or other symbol instructions, and decode it by computer, so that the machine tool can move and process parts. The blank is processed into semi-finished products by cutting tool.

CNC machining (CNC machining) refers to the processing with CNC machining tools. CNC machining CNC index controlled machine tool is programmed and controlled by NC machining language, usually G code. NC machining G code language tells CNC machine tool which Cartesian position coordinates, and controls the tool feed speed and spindle speed, as well as tool converter, coolant and other functions. Compared with manual machining, CNC machining has great advantages, such as the parts produced by CNC machining are very accurate and repeatable; CNC machining can produce parts with complex shapes that cannot be completed by manual processing. CNC machining technology has been widely promoted, most of the machining workshops have the ability of NC machining. The most common NC machining methods in typical machining workshops are CNC milling, CNC lathe and CNC EDM wire cutting (WEDM). The tool for NC milling is called CNC milling machine or CNC machining center. Computer gong processing, Dongguan computer gong processing, high-speed computer gong processing, mechanical parts processing, computer gong processing, CNC turning lathe is called CNC lathe center. NC machining G code can be manually programmed, but usually the machining workshop uses CAM software to automatically read CAD file and generate G code program to control NC machine tool.

Operation rules of CNC machining center

1. Before machining in each program, it is necessary to strictly confirm whether the tool is consistent with the program;

2. When installing the tool, it is necessary to confirm whether the length of the tool and the selected tool holder are suitable;

3. It is forbidden to open the door when the machine tool is running, so as to avoid flying knife or workpiece;

4. In case of tool collision during processing, the operator must stop the machine immediately, such as pressing the “emergency stop” button or “reset key” button or setting the “feed rate” to zero;

5. In the same workpiece, each tool setting should be kept in the same area to ensure the accuracy of cutting tool when connecting. CNC machining center operation rules;

6. If too much machining allowance is found in the process of processing, computer gong processing, Dongguan computer gong processing, high-speed computer gong processing, mechanical parts processing, computer gong processing shop must use “single section” or “pause” to clear x, y, Z values, and then manually mill them off, and then swing back to “zero” to let them run on their own;

7. During self operation, the operator shall not leave the machine tool or regularly check the operation status of the machine tool. If it is necessary to leave midway, relevant personnel must be designated for inspection;

8. The aluminum slag in the machine tool should be cleaned before the smooth knife oil injection to prevent the aluminum slag from absorbing oil;

9. Air blowing should be used in the roughening procedure and oil injection should be applied in the light knife program;

10. After the workpiece is off the machine, the burr must be removed in time;

11. When off duty, operators must make timely and accurate handover to ensure normal follow-up processing;

12. Before shutdown, ensure that the tool magazine is in the original position and the XYZ axis is in the middle position. Turn off the power supply and the general power supply on the machine tool operation panel in turn;

13. In case of thunderstorm, the power supply must be cut off immediately.

In addition to the above points, there are many things that we need to pay attention to from time to time. The system should pay attention to, and the machine should also pay attention to maintenance. In fact, most of the time, the machine will break down, to a large extent, and the user’s operation is improper. We do not pay attention to check the machine and do not warm up before starting up. Some companies have to process computer gongs in Dongguan due to the bad environment Processing | high speed computer gong processing | mechanical parts processing | computer gong processing shop | the machine has been in the dark and humid for a long time, with dust all over the sky, oil and other chemical liquid corrosion, as well as the production personnel moving the machine without authorization, it is easy to cause machine problems. In fact, if we deal with these problems in a timely manner, then our machine service life will definitely be much longer The machining accuracy and performance will be as good as new for a long time, the loss will be greatly reduced, the replacement frequency of parts will be reduced, and a lot of time and cost will be saved.

Basic process of CNC machining parts

1. High speed CNC processing product analysis, through product analysis, we should obtain certain composition information and some specific processing requirements. 2. Graphic design the graphic design should be based on the detailed analysis of the product. For example, for the processing of the seal, we should determine the font, text size, seal type by analyzing the processing requirements. Computer gong processing | Dongguan high-speed computer gong processing | Dongguan mold processing | Dongguan Mechanical parts processing | CNC processing 3. High speed CNC processing process planning through the analysis of the appearance and processing requirements of the workpiece products in the early stage, each processing step is reasonably established from the overall processing situation. 4. In fact, the process of path generation is to realize the process planning through software, and optimize the tool path by setting parameters. 5. After the path simulation path is generated, we generally have no intuitive sense of its final performance on the machine tool. Here we can check the possible problems through path simulation, thus reducing the actual processing scrap rate. The general inspection focuses on the effect of workpiece appearance, whether it is overcut or undercut, and whether the process planning of the path is reasonable. 6. High speed CNC machining path output path output is a necessary step of software design and programming on the machine tool. Through the path output, the relationship between the two can be established by the intermediate reference. The main components of high-speed CNC computer gongs mould show that 1. Synthetic resin of high-speed computer gongs is the main component of plastics, and its content in plastics is generally 40% – 100%. Because of its high content, and the nature of resin often determines the nature of plastic, so people often regard resin as a synonym for plastic. Computer gong processing | Dongguan high speed computer gong processing | Dongguan mold processing | Dongguan machine parts processing | CNC processing. For example, PVC resin and PVC plastic, phenolic resin and phenolic plastic are confused. In fact, resin and plastic are two different concepts. Resin is a kind of raw polymer, which is not only used in the manufacture of plastics, but also the raw material of coatings, adhesives and synthetic fibers. In addition to a small part of plastics containing 100% resin, most plastics, in addition to the main component resin, also need to add other. 2. The function of lubricant is to prevent the plastic from sticking to the metal mold during molding, and to make the surface of plastic smooth and beautiful. Commonly used lubricants are stearic acid and its calcium magnesium salt. In addition to the additives mentioned above, flame retardant, foaming agent and antistatic agent can also be added into the plastics. Substance. 3. High speed computer gongs mold filler also known as filler, it can improve the strength and heat resistance of plastics, and reduce the cost. Numerical control machine tool processing, such as adding wood powder into phenolic resin, can greatly reduce the cost, making phenolic plastics one of the cheapest plastics, while significantly improving mechanical strength. The fillers can be divided into organic fillers and inorganic fillers, the former such as wood flour, rags, paper and various fabric fibers, and the latter such as glass fiber, diatomite, asbestos, carbon black, etc. 4. Colorants colorants can make plastics have a variety of bright and beautiful colors. Organic dyes and inorganic pigments are commonly used as colorants in Dongguan high-speed computer gongs processing. 5. Plasticizers plasticizers can increase the plasticity and softness of plastics, reduce brittleness, and make plastics easy to process. Plasticizers are usually organic compounds with high boiling point, which are miscible with resin, nontoxic, odorless, light and heat stable, and phthalate esters are the most commonly used. For example, in the production of PVC plastic, computer gong processing, Dongguan high-speed computer gong processing, Dongguan mold processing, Dongguan Mechanical parts processing, CNC processing, if more plasticizer is added, soft PVC plastic can be obtained; if the plasticizer is not added or less (the dosage is less than 10%), the rigid PVC plastic is obtained. 6. In order to prevent the synthetic resin from being decomposed and damaged by light and heat in the process of processing and using, and prolong the service life, the stabilizer CNC should be added into the plastic

Machining process specification

Machining process specification generally includes the following contents: process route of workpiece processing, specific content of each process and equipment and process equipment used, inspection items and inspection methods of workpiece, cutting amount, time quota, etc.

So in the process of machining, what are the steps to formulate the process specification? Let’s take a look at it

1) Calculate the annual production program and determine the type of production.

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

3) Select the blank.

4) Draw up the process route.

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.

8) Determine the technical requirements and inspection methods of each main process.

9) Fill in process documents.

In the process of working out the process, it is often necessary to adjust the contents that have been initially determined before in order to improve the economic benefits. Computer gong processing, Dongguan high-speed computer gong processing, Dongguan mold processing, Dongguan Mechanical parts processing, CNC processing, in the process of implementing the process specification, there may be unexpected situations, such as the change of production conditions, the introduction of new technology and new technology, the application of new materials and advanced equipment, which require timely revision and improvement of the process specification.

The technological process of machining includes, generally speaking, the process of changing the overall dimension and performance of the workpiece through a kind of mechanical equipment.

The working principle of machining process regulation is high quality, high yield and low cost, that is, under the premise of ensuring product quality, labor productivity can be improved and cost can be reduced as much as possible. What problems should be paid attention to in the process planning? Let’s take a look at it

1., the advanced technology.

In the formulation of machining process procedures, computer gong processing, Dongguan high-speed computer gong processing, Dongguan mold processing, Dongguan Mechanical parts processing, CNC processing should make full use of the existing production conditions of the enterprise, as far as possible, use domestic and foreign advanced technology and experience, and ensure good working conditions.

2. Economic rationality

Under the specified production program and production batch, there may be several process schemes that can meet the technical requirements of parts. At this time, the process cost is generally required to be the lowest through accounting or comparison with each other. Make full use of the existing production conditions, spend less and do more.

3. Good working conditions

报错笔记

Advantages of CNC machine tools over ordinary machine tools

The advantages of CNC machine tools are as follows:

1. Processing efficiency, saving processing time.

2. Work intensity. After the workers have finished programming, they can go to drink tea after the first piece is qualified.

3. Reduce the number of waste products. As long as the first piece is qualified, the processed parts will generally be qualified.

4. High safety, the farther the workers are from the processing equipment, the lower the probability of accidents.

For effective metal cutting, machining materials, cutting tools and cutting conditions are the three main factors. These determine the processing time, tool life and machining quality. Cutting conditions must be selected reasonably for economical and efficient processing methods.

The three elements of cutting conditions: cutting speed, feed and cutting depth directly cause damage. With the increase of cutting speed, the point temperature will rise, resulting in mechanical, chemical and thermal wear. If the cutting speed is increased by 20%, the tool life will be reduced by 1 / 2.

Back feed conditions and tool wear are kept to a minimum. But feeding behind, cutting temperature rise, wear. It is less than the effect of cutting speed. Cutting depth has no effect on cutting speed and feed, small cutting depth, but cutting material in hardened layer will also affect tool life.

According to the user’s processing material, hardness, cutting conditions, material selection, feed and cutting depth, the cutting speed is used.

Based on the selection of the most suitable process conditions, these factors are selected. Regular life and stable wear are the most ideal conditions.

However, in practice, the selection of tool life and tool wear, through machining size, surface quality, noise reduction, heat and so on. Under certain processing conditions, it is necessary to study according to the actual situation. Difficult to machine materials such as stainless steel, heat-resistant alloy, can use coolant or choose a good rigid blade.

Reasonable selection of cutting tools

1。 Rough rotation, should choose high strength, good durability knife, in order to meet the large car turning, feedback.

2。 The essence of automobile is to select high precision, durable and good cutting tools to ensure the machining accuracy.

3。 Reduce the conversion time and knife convenience, should try to use machine knife and machine clip blade.

Select fixture

1。 General fixture should be selected to clamp workpiece as much as possible, and special fixture should be avoided;

2。 Positioning error is reduced by coincidence.

Determine the processing route

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

1。 It should be able to meet the requirements of machining accuracy and surface roughness;

2。 Shorten the processing route as far as possible and reduce the idle travel time of the tool.

Machining route and allowance

Introduction of CNC machining power input unit and power control part

There are two lights on the power supply of the computer gongs processing center unit. One is the power indicator light, which is green; the other is the power alarm light, which is red. The power supply unit here includes power input unit and power control part.

First of all, we should know that when the power supply of Dongguan mold machining center cannot be connected, if the power indicator (green) is not on. The fuses F1 and F2 of the power supply unit have been blown. This is due to high input voltage, or the components of the power supply unit itself have been damaged.

The input voltage is low. Please check the voltage entering the power supply unit. The allowable voltage value is ac200v + 10%, 50Hz ± 1Hz. The power supply unit is not good, there is element damage in it. The power indicator light is on, and the alarm light is also gone, but the power supply cannot be connected. Dongguan machine parts processing at this time because the power on (on) conditions are not satisfied. By the following switching circuit, the power supply conditions are as follows:

There are three conditions for the power supply of Dongguan large CNC machining center: first, the source on button is closed. Second, the power off button is closed. Third, the external alarm contact is opened.

The alarm light of power supply unit of Dongguan large CNC machining center is on: the fuse of 24 V output voltage is fused, and + 24 V voltage is used on 1.9 “display screen, as shown in the figure below. Check whether + 24 V is short circuited to the ground.