Category Archive CNC Technology

In the process of NC machining, it is easy to appear over cutting, undercutting and other phenomena. At the same time, the damage of cutting tools, or the processing of waste products, the interference and collision between parts and tools, tools and fixtures, tools and worktables, will cause a certain cost waste. The NC machining simulation system can simulate the related program well and reduce the loss to the greatest extent.

Before the actual machining, the programmer can confirm whether the finished cutting product is consistent with the original design drawing through the simulation system, and can make better detailed analysis.

collision detection

In the actual processing, five axis CNC machining has more advantages than three axis CNC machining, can achieve a wider range, has faster material and efficiency, can reduce processing time and improve surface accuracy. However, due to the high degree of freedom of the two additional rotating axes, it is easy to cause collision and damage to the machine tool.

Therefore, before the actual processing, it is necessary to detect the collision with the help of NC machining simulation system. The main detection algorithms are as follows:

The machine tool includes many parts, but the collision detection algorithm between different parts is similar. The computer gong machining simulation system takes the cutter, workpiece and fixture as the main research object to detect the possible global collision.

1. According to the tool location, the grid voxel model of the tool head scanning body and the grid voxel model of the tool holder scanning body are solved respectively. The tool holder scanning body is used to detect whether there is a global collision between the tool, workpiece and fixture, and the tool head scanning body is used to calculate the intersection between the tool and the workpiece.
2. A feature attribute of voxel model is cuboid envelope box. The envelope box is used to make rough judgment. If the envelope box does not intersect, the objects enclosed in the envelope box will not intersect. At this time, the position data of the object envelope box will be updated, and other information will not change. It will prepare for the generation of the next tool point scanner and collision detection. Rough judgment can speed up the detection Speed.
3. Once a collision occurs, the system stops reading data and reports the error message and the precise location of the collision. If there is no collision, the system continues to carry out the teaching operation between the tool head and the workpiece.

A circle passing through the same point

When I and K are zero, they can be omitted; regardless of G90 or G91 mode, I, J, K are programmed according to relative coordinates; when circular interpolation, tool compensation instruction G41 / G42 cannot be used.

1. Advantages and disadvantages between G92 and G54-G59

G54-G59 is the coordinate system set before machining, while G92 is the coordinate system set in the program. If G54-G59 is used, there is no need to use G92 again, otherwise G54-G59 will be replaced and should be avoided, as shown in Table 1.

Table 1 difference between G92 and working coordinate system`

Note: (1) once G92 is used to set the coordinate system, G54-G59 will not work unless the system is restarted after power failure or G92 is used to set the required new workpiece coordinate system. (2) After using G92 program, if the machine tool does not return to the original point set by G92, the program will be started again, and the current position of the machine tool will become the new workpiece coordinate origin, which is prone to accidents. Therefore, we hope that readers will use it carefully.

1. Compile tool changing program.

In the machining center, tool change is inevitable. However, there is a fixed tool change point when the machine tool leaves the factory. If it is not in the position of tool change, it is impossible to change the tool. Moreover, before changing the tool, the tool compensation and circulation must be cancelled, the spindle is stopped and the coolant is turned off. There are many conditions. It is not only easy to make mistakes but also inefficient to ensure these conditions before each manual tool change. Therefore, we can compile a tool change program to save the memory and MDI status

Under the call of M98, the tool change action can be completed at one time.

Taking pmc-10v20 machining center as an example, the program is as follows:

O2002; (program name)

G80g40g49; (cancel fixed cycle, cutter compensation)

M05; (spindle stop)

M09; (coolant off)

G91g30z0; (Z axis returns to the second origin, i.e. tool change point)

M06; (tool change)

M99; (end of subroutine)

When the tool needs to be changed, just type “t5m98p2002” in MDI state to replace the required tool T5, thus avoiding many unnecessary mistakes. According to the characteristics of their own machine tools, the majority of readers can work out the corresponding tool change program.

1. Others

The sequence number of the program segment is represented by address n. Generally, the memory space of NC device itself is limited (64K). In order to save storage space, the sequence number of program segment is omitted. N only means the segment label, which is convenient to find and edit the program, and has no effect on the processing process. The sequence number can be increased or decreased, and the continuity of the value is not required. However, some loop instructions, jump instructions, calling subroutines and mirror instructions can not be omitted.

1. In the same program segment, the later occurrence of the same instruction (the same address symbol) or the same set of instructions takes effect.

For example, tool change procedure, t2m06t3; instead of T2, T3 is replaced;

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:

High machining precision and stable machining quality;

It can carry out multi coordinate linkage and process parts with complex shapes;

When the processing parts are changed, the computer gong processing only needs to change the NC program, which can save the production preparation time;

The machine tool itself has high precision and rigidity. It can choose favorable processing amount and high productivity (generally 3 ~ 5 times of ordinary machine tool);

High degree of automation of machine tools can reduce labor intensity;

The requirements for the quality of operators are higher, and the technical requirements for maintenance personnel are higher.

CNC machine tools are generally composed of the following parts:

The main engine is the theme of CNC machine tools, including machine body, column, spindle, feed mechanism and other mechanical components. It is a mechanical part used to complete various cutting processes.

CNC device is the core of CNC machine tool, including hardware (printed circuit board, CRT display, key box, paper tape reader, etc.) and corresponding software, which is used to input digital part program, computer gong processing and complete input information storage, data transformation, interpolation calculation and Realization of various control functions.

The machine tool is composed of a CNC drive unit, a main shaft drive unit and a motor drive unit. Under the control of the numerical control device, he realizes the spindle and feed drive through the electric or electro-hydraulic servo system. When several feed linkage, positioning, straight line, plane curve and space curve processing can be completed.

Auxiliary device, some necessary matching parts of index control machine tool, to ensure the operation of CNC machine tool, such as cooling, chip removal, lubrication, lighting, monitoring, etc. It includes hydraulic and pneumatic devices, chip removal device, exchange table, CNC turntable and CNC dividing head, as well as cutting tools and monitoring and detecting devices.

Programming and other auxiliary equipment can be used to program and store parts outside the machine.

Since the first CNC machine tool was developed by Massachusetts Institute of technology in 1952, numerical control machine tool has been widely used in manufacturing industry, especially in automobile, aerospace and military industry. Numerical control technology has developed rapidly both in hardware and software.

In order to improve the accuracy of the groove width and reduce the number of tool changes, the milling cutter with a diameter of 7 than the groove width can be used to mill the middle part of the groove first, and then use the tool radius compensation function to mill the two sides of the groove.

Ball end milling cutter, ring milling cutter, drum milling cutter, cone milling cutter and disc milling cutter are often used in machining solid curved surface or variable bevel profile.

When the machining allowance is small and the requirement of surface roughness is high, the face milling cutter with cubic boron nitride blade or ceramic insert blade can be selected for high-speed cutting.

According to the principle of NC machining, the overall consideration is made according to the requirements of workpiece processing drawings, the format specified by the CNC milling machine is used for editing, and the processing program input is carried out according to the action sequence. Thus, it is necessary to know the precision machining technology of CNC lathe while compiling the NC program.

1. Determine the process flow. The processing technology of CNC milling machine is very similar to that of ordinary machine tool. Through analyzing the workpiece, specify the processing route, select the processing procedure, select the machine tool, fixture and cutter. Determine the equipment baseline position and cutting amount. The difference is that CNC machine tools need to program the operation process.
2. Calculate the tool coordinate value. In order to facilitate the programming and calculation of tool path coordinates. The workpiece coordinate, part size and shape must be calculated before machining, so as to determine the whole machining path of the tool.
3. Write processing program, for simple workpiece can be written manually, but for complex processing workpiece, automatic programming is needed.
4. There are many ways to input programs into CNC system, which are mainly accomplished by the operation panel of CNC control system. In addition, the interface between computer and CNC system can be connected to input program by computer.
5. Comprehensive inspection of procedures. Through the function of graph magic shadow display or NC milling machine equipment running without load, the machine tool running track is checked, and whether the tool movement meets the requirements of capping.

It is characterized by:

1. The vertical milling head is equipped with tx400 heavy gantry milling head and double rectangular guide rail with strong rigidity;
2. The milling head is equipped with ball screw, pneumatic broach device and driven by servo motor;
3. The side milling head is equipped with V5 type gantry milling head, Dongguan high-speed computer gong processing is equipped with independent lubrication device, and the lifting is driven by ordinary reducer and frequency conversion speed regulation;
4. The three-axis CNC system with one key conversion from general milling to CNC milling can be programmed and operated manually by using the extended panel, which is highly realizable in the actual machining process;
5. The machine bed forward and backward, beam up and down, vertical milling head up and down are equipped with Taiwan ball screw, driven by servo motor;
6. Equipped with synchronous belt and synchronous wheel;
7. Hand held electronic hand wheel unit, convenient for three axis tool setting;
8. The unique safety interlock device for lifting the crossbeam is used for machining mechanical parts, and CNC machining ensures the repeated positioning accuracy of the machine tool;
9. The cycloid pump set is lubricated continuously with low failure rate.

With the same cutting tool and cutting parameters, semi finishing and finishing can correct various geometric errors of cutting tools and elastic deformation of parts, It is easy to ensure the size and finish machining the important bottom surface. Don’t think that high-precision parts processing is a common processing without paying attention to it. If we ignore some details, it may have a great impact on the processing of parts, so what are the matters needing attention in the processing of high-precision parts?

1. For high-precision parts, the processing is very strict, and the processing procedures include feed in and out. CNC machining has specific requirements for size and accuracy, such as 1 mm plus or minus how many microns. If the size is wrong too much, it will become a waste product. At this time, it is equivalent to re processing, which is time-consuming and laborious. Sometimes, the whole processing material will be scrapped, which leads to the increase of cost. At the same time, the parts are definitely unusable.
2. For high-precision parts processing, it is mainly the size requirements, such as the cylinder diameter, there are strict requirements, and the positive and negative errors within the specified range are qualified parts, otherwise, they are all unqualified parts; There are strict requirements for length, width and height, as well as positive and negative errors. For example, for an embedded cylinder (take the simplest basic parts as an example), if the diameter is too large and exceeds the allowable range of error, it will cause the situation that it can not be inserted. If the actual diameter is too small and exceeds the lower limit of allowable negative error value, it will cause the problem of too loose insertion and not firm. These are all unqualified products, or the cylinder length is too long or too short, beyond the allowable range of error, are unqualified products, are to be scrapped, or reprocessing, which will inevitably cause the increase of cost.
3. In fact, the processing requirements of high-precision parts are the most important dimension problems. We must process them in strict accordance with the additional drawings. The actual sizes processed by CNC will not be the same as the theoretical dimensions of drawings. However, as long as the machining dimensions are within the allowable range of error, they are all qualified parts. Therefore, the requirements of precision parts processing are strictly in accordance with the theory Dimension processing.
4. The second is the advanced precision parts processing equipment and testing equipment, advanced processing equipment makes the processing of precision parts more simple, higher precision and better effect. CNC processing and testing equipment can detect parts that do not meet the requirements, so that all products sent to customers really meet the requirements.

The molds used in the production line must pass the inspection before being put into storage. Inspection procedures: ① the last part of the production line is sent for inspection, and the qualified parts are put into the warehouse with the certificate. ② The mold maintenance personnel shall check whether the tool edge of the mold is sharp, whether the guide parts are lubricated, whether the positioning is reliable, whether the spring top is powerful, and carry out maintenance if necessary. After the mold is qualified, the certificate and sample shall be put into the warehouse. ③ If there is no need for maintenance, the certificate and samples should be put into the warehouse.

1. The dispatcher puts forward the requirement of backup mould according to the production needs and mould wear. Report to the competent department and project leader. Ensure the normal production.

4、 Die scrapping system mold scrap system is to ensure that the mold can not normally produce qualified products, and there is no mold repair or mold change necessary to protect the company’s assets.

1. The scrapped molds must be returned to the mold warehouse, so the scrapped molds must be provided with a scrap certificate, which must be signed by the mold administrator and the mold inspector, and the reasons for scrapping must be written.
2. After the die is scrapped, the relevant mould data must be filed to the document control center for inspection.

5、 Responsibilities and rights of mold warehouse management personnel

1. The mould should be put on the shelf according to the production order 1 ᦇ, 2 ᦇ and 3 ා. The returned mould should be placed in the original position.
2. The storekeeper shall be responsible for the balance of account, card and material phase. The general ledger, mold certificate, test card, sample parts, production files should be kept well, and the inventory, collection, maintenance and other molds should be well known. Supervise and urge the mold maintenance personnel to put the repaired mold into storage in time.
3. The storekeeper should find the mould quickly according to the production order number.
4. The storekeeper shall be responsible for the intactness of the molds in storage, receiving and returning. No confusion, loss or damage is allowed. The mould management system should be strictly followed. Make sure that the molds from the warehouse are qualified for mass production.
5. The storekeeper has the right to refuse to go through the warehousing and receiving procedures for the personnel who fail to perform the provisions.
6. The storekeeper should actively cooperate with the workshop production, communicate with the dispatcher in time, understand the production task, and do a good job in serving the front line.

【2】 Management of mold field use

1. Dispatchers should handle the relevant procedures according to the corresponding management system when they receive and return the molds. They should be responsible for the whole process of the molds from receiving to returning to the warehouse.
2. The die should be processed by punching machine of corresponding tonnage according to stamping process. The mold should be adjusted and installed by the mold adjuster, and ensure that the leakage is unobstructed, the spring top is normal, the feeding is convenient, and the stroke is reasonable. Only after the qualified samples are tested can the production be started.
3. Punch workers in the work in strict accordance with the operating procedures. Any abnormal phenomenon found in the production process shall be reported in time, and the production shall be carried out after troubleshooting. In case of mold damage caused by rough operation, the responsible person shall fill in the mold accident responsibility sheet and give certain punishment.
4. In case of any damage to the die and punch caused by the fracture of the die scrap, the deformation of the guide plate guide part and the blocking of the press bending die, the responsibility of the straightener shall be investigated.
5. The usage of the mould should be made clear in the day shift and night shift. The successor shall be responsible for the responsible accident after the handover.
6. After the completion of the production task, the dispatcher shall be informed to handle the warehouse returning procedures in time. The production site should not keep the mold without production order or completing the batch task. In case of mold loss, the responsibility of the final recipient will be traced. Dongguan machine parts processing

Purpose of mold maintenance system

1. Master the history of the mold 2. Maintain the mold timely after the mold production 3. Improve the mold life 4. Ensure the mold quality and smooth production

Mold maintenance mode mold maintenance is divided into four modes. 1. Preventive inspection: every 15 days as a cycle cycle, directly check the mold status on the production machine, and record the results in the “mold preventive inspection record form”. This part of the inspection is in the charge of the mold group with the assistance of the injection molding department. 2. General maintenance (A-level maintenance): it refers to the general maintenance items of the mold during the daily mold test and trial production, and the production department is responsible for and records. 3. Regular quantitative maintenance (Level B maintenance): when the molds have not been used for more than one year or accumulated more than 50000 beers each time, detailed inspection shall be conducted, and the inspection results shall be recorded in the “mold maintenance inspection record form”. The production department is responsible for and does

In addition, the CNC tool position and tool position control are also discussed.

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. 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. Leading CNC machine tool brands include Hass, DMG (Deckel MAHO GILDEMEISTER), Mazak, Mori Seiki, fadal and wasino.

There are two steps in the formulation of machining process specification. First of all, it is to draw up the process route of parts processing, and then determine the process size of each process, the equipment and process equipment used, as well as the cutting specifications, man hour quota, etc. These two steps are interrelated and should be analyzed comprehensively.

The number of each working procedure, the total processing route, and the selection of the overall surface processing process are determined. The general principles of the process route are as follows:

1. Machining datum plane first

In the process of machining parts, the surface as positioning reference should be machined first, so as to provide precise reference for subsequent processing as soon as possible. It is called “benchmark first”.

1. Dividing processing stages

The surface with high machining quality is divided into three stages: rough machining, semi finishing and finishing. It is mainly to ensure the processing quality, to use the equipment reasonably, to arrange the heat treatment process, and to find the blank defects easily. machining

CNC machining center is locked by software. When the automatic operation button is pressed during simulation processing, it is not possible to directly see whether the machine tool has been locked in the simulation interface. Computer gong processing | Dongguan computer gong processing | Shenzhen computer gong processing | mechanical parts processing | Guangzhou computer gong processing | often there is no tool setting during the simulation. If the machine tool is not locked and running, it is very easy to hit the tool. Therefore, before the simulation processing, you should go to the operation interface to confirm whether the machine tool is locked. Forget to turn off the idle switch during processing. In order to save time, the idle switch is often turned on when the program is simulated. Idle running means that all moving axes of the machine tool run at the speed of G00. If the running switch is not turned off during machining, the machine tool will ignore the given feed speed and run at G00 speed, which will cause the accident of cutting and hitting the machine tool. There is no return to the reference point after running the simulation without load. When checking the program, the machine tool is locked, and the tool relative to the workpiece processing is in simulated operation (absolute coordinates and relative coordinates are changing). At this time, the coordinates are inconsistent with the actual position. It is necessary to use the method of returning to the reference point to ensure that the zero point coordinate of the machine is consistent with the absolute and relative coordinates. If there is no problem found after the calibration program, the machining operation will cause tool collision. The direction of override release is wrong.

When the machine tool overtravel, press and hold the overtravel release button and move in the opposite direction with manual or manual mode, which can be eliminated. However, if the direction of release is reversed, it will cause damage to the machine tool. Because when pressing the override release, the over travel protection of the machine tool will not work, and the travel switch of the over travel protection is already at the end of the stroke. At this time, the table may continue to move towards the overtravel direction, and eventually the screw will be broken, causing damage to the machine tool. Computer gong processing | mechanical parts processing | Dongguan CNC machining center | Dongguan high-speed computer gong processing designated line running time mark is improper. When the specified line is running, it is usually executed from the cursor position down. For the lathe, it is necessary to call the tool offset value of the tool used. If the tool is not called, the tool in the running program section may not be the required tool, which is very likely to cause a tool collision accident due to different tools. Of course, in the machining center, CNC milling machine must first call the coordinate system such as g54 and the length compensation value of the cutter. Because the length compensation value of each knife is different, it may cause knife collision if it is not called.

CNC machining center CNC machine tool as a high-precision machine tool, anti-collision is very necessary, require the operator to develop a careful habit, according to the correct method to operate the machine tool, reduce the occurrence of tool collision. With the development of technology, there are some advanced technologies, such as tool damage detection, anti-collision detection and adaptive machining, which can better protect CNC machine tools. After the industrial revolution, the pace of production can be said to be faster and faster. Nowadays, CNC machine tools seem to be used in many fields, because of the precise control and high-end technology, the product specifications produced by them are also more standardized. All of this, thanks to CNC complex parts processing technology is becoming more and more high-end, because of this, so modern we can enjoy the production mode and efficiency that we did not dare to think of before.

Since the advent of CNC machine tools, more and more manufacturers have begun to introduce such good machinery into their respective industries. Businesses hope to pursue high output, but also require products to meet production standards. This is a very strict requirement for the machine tool. It not only requires the working efficiency of the whole machine tool to maintain high efficiency, but also has many fine requirements for each internal part. CNC complex parts processing can be said to be the basis for ensuring the overall quality of CNC machine tools. Only by ensuring that the processing technology of CNC complex parts remains at a high level, can many manufacturers be assured of using it Create more and better products.

Measurement datum and positioning datum.

(1) Assembly datum: the datum used to determine the position of parts in parts or products during assembly, which is called assembly datum.

(2) Measurement datum: the datum used to check the size and position of machined surface, which is called measuring datum.

(3) Positioning datum: the datum used for workpiece positioning during machining, which is called positioning datum. The surface (or line or point) processed by computer gong as the positioning reference can only select the rough surface in the first process. This positioning surface is called rough datum. The machined surface can be used as the positioning reference in the following processes, and the positioning surface is called the precise reference.

In the process of turning a blank into a finished product, the total thickness of the metal layer cut off on a machining surface is called the total machining allowance of the surface. The thickness of the metal layer cut by each process is called the machining allowance between processes. For the rotating surface such as outer circle and hole, the machining allowance is considered from the diameter, so it is called symmetrical allowance (i.e. bilateral allowance), that is, the actual thickness of the metal layer cut off is half of the machining allowance on the diameter. The machining allowance of the plane is the unilateral allowance, which is equal to the actual thickness of the metal layer removed. The purpose of leaving machining allowance on the workpiece is to remove the machining errors and surface defects left by the previous process, such as the surface cold and hard layer, air hole and sand inclusion layer on the casting surface, oxide scale, decarburization layer and surface crack on the forging surface, internal stress layer and surface roughness after cutting. The precision and surface roughness of the workpiece are improved. The size of machining allowance has great influence on machining quality and production efficiency. If the machining allowance is too large, it not only increases the labor of machining, reduces the productivity, but also increases the consumption of materials, tools and power, and increases the processing cost. If the machining allowance is too small, it can not eliminate all kinds of defects and errors in the previous process, and can not compensate for the clamping error in this process, resulting in waste products. The selection principle is to make the allowance as small as possible on the premise of ensuring the quality. Generally speaking, the more finish machining, the smaller the process allowance.

Applicability:

In the process of turning a blank into a finished product, the total thickness of the metal layer cut off by the computer gongs on a machining surface is called the total machining allowance of the surface. The thickness of the metal layer cut by each process is called the machining allowance between processes. For the rotating surface such as outer circle and hole, the machining allowance is considered from the diameter, so it is called symmetrical allowance (i.e. bilateral allowance), that is, the actual thickness of the metal layer cut off is half of the machining allowance on the diameter. The machining allowance of the plane is the unilateral allowance, which is equal to the actual thickness of the metal layer removed. The purpose of leaving machining allowance on the workpiece is to remove the machining errors and surface defects left by the previous process, such as the surface cold and hard layer, air hole and sand inclusion layer on the casting surface, oxide scale, decarburization layer and surface crack on the forging surface, internal stress layer and surface roughness after cutting. The precision and surface roughness of the workpiece can be improved by computer gonging. The size of machining allowance has great influence on machining quality and production efficiency