February 15, 2017 CNC machining
CNC machining, refers to the CNC machine tools for processing a part of the process, CNC machine tool processing and traditional machine tool processing procedures are generally the same, but also has undergone significant changes. Machining method for controlling the displacement of parts and tools with digital information. It is an effective way to solve the problems of variable variety, small batch, complex shape, high precision and high efficiency and automatic processing.
Table of content
CNC machining refers to the control system issued by the instructions to make the tool to meet the requirements of the various movements, in the form of numbers and letters that the shape and size of the workpiece and other technical requirements and processing requirements of the processing. It refers to the CNC machine tools for parts processing process.
CNC machine tools is a computer to control the machine, used to control the machine computer, whether it is a dedicated computer, or general-purpose computers are collectively referred to as CNC system. CNC machine tools and auxiliary movements are controlled by the NC system issued by the instructions. The NC system instructions are programmed by the programmer according to the material of the workpiece, the machining requirements, the characteristics of the machine and the instruction format (numerical control language or symbol) specified by the system. CNC system according to the program instructions to the servo device and other functional parts issued by the operation or termination information to control the various movements of the machine. When the machining process of the part is finished, the machine will automatically stop. Any kind of CNC machine tools, in its numerical control system if there is no input program instructions, CNC machine tools can not work. The control of the machine tool generally includes the start and stop of the machine; the start and stop of the spindle, the direction of rotation and the speed change; the direction, speed and mode of the feed movement; the selection of the tool, the compensation of the length and the radius; Liquid opening, closing and so on.
2. Development background
CNC technology originated in the aviation industry needs, the late 1940s, the United States a helicopter company put forward.
The initial idea of CNC machine tools, in 1952 the United States MIT developed a coordinate CNC milling machine. In the mid-1950s, this CNC milling machine was used to process aircraft parts. In the 1960s, CNC systems and programming were becoming more sophisticated and sophisticated, and CNC machines were used in various industrial sectors, but the aerospace industry was always the largest user of CNC machines. Some large aviation factories with hundreds of CNC machine tools, including cutting machine-based. CNC machining parts are aircraft and rocket of the overall wall panels, beams, skin, frame, propeller and aircraft engine casing, shaft, plate, blade mold cavity and liquid rocket engine combustor special cavity surface, etc. The CNC machine tool development is the beginning of a continuous track CNC machine tools, continuous trajectory control.
Continuous trajectory control, also known as contour control, requires the tool to move relative to the part according to the specified trajectory. And later vigorously develop point control CNC machine tools. Point control refers to the tool from a point to another point of movement, as long as the final can accurately reach the target regardless of how the mobile route.
3. Operation process
3.1 NC programming
CNC machining program preparation methods are manual (manual) programming and automatic programming of the points. Manual programming, the entire contents of the program is manually by the NC system specified by the instruction format written. Automatic programming is computer programming, can be divided into language and painting based on the automatic programming method. However, no matter what kind of automatic programming method, need to have the appropriate supporting hardware and software.
It can be seen that the realization of CNC machining programming is the key. But the programming is not enough light, CNC machining also includes programming must be done before a series of preparatory work and after the preparation of the aftermath of the work. In general, CNC machining process mainly includes the following:
(1) to select and determine the parts and contents for CNC machining;
⑵ the part of the drawings for CNC machining process analysis;
⑶ CNC machining process design;
⑷ mathematical processing of parts drawings;
⑸ preparation of processing procedures;
⑹ according to the program production control medium;
(7) Verification and modification of the program;
⑻ the first piece of test processing and on-site problem processing;
⑼ CNC machining process file stereotypes and archiving.
In order to improve the degree of production automation, shorten the programming time and reduce the cost of CNC machining, in the aerospace industry also developed and used a series of advanced CNC machining technology. Such as computer numerical control, that is, with a small or microcomputer instead of CNC controller in the system, and stored in the computer software to perform the calculation and control functions, this soft-connected computer numerical control system is gradually replacing the initial state of the numerical control system. Direct CNC is a computer directly control multiple CNC machine tools, it is suitable for small batch short-cycle production of the aircraft. The ideal control system is an adaptive control system that can continuously change the machining parameters. Although the system itself is complex and expensive, it can improve the processing efficiency and quality. The development of CNC In addition to the hardware aspects of the CNC system and machine improvement, there is another important aspect is the development of software. Computer-aided programming (also called automatic programming) is written by the programmer in a numerical language, it is input to the computer for translation, and finally by the computer automatically output perforation tape or tape. The more widely used CNC language is the APT language. It is roughly divided into main processing and post-processing. The former programmer to write the program to be translated, calculate the tool path; the latter tool path into the NC machine parts processing program. CNC machining, in the workpiece before processing in advance on the computer to prepare a good program, and then enter these procedures to the use of computer program control machine for instructional processing, or directly in the computer program control machine control panel to write instructions For processing. Processing process includes: knife, tool change, speed, change, parking, etc., are automatically completed. CNC machining is a modern mold manufacturing and processing of an advanced means. Of course, CNC machining means must not only for the mold parts processing, use a very wide range.
3.2 Process analysis
Machined parts of the NC machining process involves a wide range of the following combination of the possibility and convenience of programming some of the necessary analysis and review must be the main content.
1, size should be marked with the characteristics of CNC machining
In NC programming, all points, lines, faces of the size and location are based on programming origin as the base. So it is best to give the coordinates of the coordinates directly on the map, or try to use the same reference size.
2, geometric elements of the conditions should be complete and accurate
In the programming, the programmer must fully grasp the geometric elements of the contours of the components and the relationship between the geometric elements. Because all the geometric elements of the part contour are defined during automatic programming, the coordinates of each node are calculated manually, and no matter what is unclear or uncertain, programming can not be done. However, because the parts designers in the design process to consider ill-considered or ignored, often incomplete or incomplete parameters, such as arc and straight line, arc and arc is tangent or intersecting or separated. So in the review and analysis of drawings, be sure to carefully find the problem in time with the designer.
3, positioning benchmarks reliable
In CNC machining, the processing process is often more concentrated, with the same benchmark positioning is very important. So often need to set some auxiliary benchmarks, or add some process on the blank boss.
4, unified geometry type or size
The shape of the part, the cavity is best to use a unified geometric type or size, which can reduce the number of tool changes, but also may use control procedures or special procedures to shorten the program length. The shape of the parts is as symmetrical as possible, making it easy to program the mirror processing functions of the CNC machine to save programming time.
3.3 parts clamping
First, locate the basic principles of installation
In the CNC machine tools on the processing of parts, the basic principle of positioning and installation is a reasonable choice of positioning benchmarks and clamping program. In the choice should pay attention to the following:
1, to design, process and programming the basis of benchmarking.
2, try to reduce the number of clamping, as far as possible in a positioning after clamping, processing all the surface to be processed.
3, to avoid the use of machine-man-made adjustment of the program, in order to give full play to the effectiveness of CNC machine tools.
Second, choose the basic principles of fixture
The characteristics of NC machining on the fixture put forward two basic requirements: First, to ensure that the fixture coordinate direction and the direction of the coordinates of the machine is relatively fixed; the second is to coordinate the parts and machine coordinate system size relationship. In addition, consider the following:
1, when the parts processing batch is not large, should try to use combination fixture, adjustable fixture and other general fixture to shorten the production preparation time, save production costs.
2, in the batch production to consider the use of special fixtures, and strive to simple structure.
3, parts of the loading and unloading to be fast, convenient and reliable, to shorten the machine’s pause time.
4, the fixture on the parts should not interfere with the machine parts of the surface of the processing, that is, fixtures to be open, its positioning, clamping mechanism components can not affect the processing of the knife (such as collision, etc.)
3.4 Processing error
CNC machining error △ number plus programming error △ series, machine error △ machine, positioning error △, knife error △ knife and other errors formed.
That is: △ number plus = f (△ series + △ + + + + knife)
1, programming error △ by the approximation error δ, round error composition. The approximation error δ is generated by approximating the non-circular curve with a straight line or arc segment, as shown in Figure 1.43. Round error is the error that occurs when the coordinate values are rounded to the integer pulse equivalent. The pulse equivalent refers to the amount of displacement of each unit pulse corresponding to the axis. General precision level CNC machine tools, the general pulse equivalent value of 0.01mm; more precision CNC machine tool pulse equivalent value of 0.005mm or 0.001mm and so on.
2, machine error △ machine by the NC system error, feed system error and other reasons.
3, positioning error △ is when the workpiece in the fixture positioning, fixture in the machine when the positioning occurs.
4, the knife error △ knife is to determine the relative position of the tool and the workpiece generated.
4. Main features
CNC machine tools from the beginning to select a complex surface with the aircraft parts as a processing object, to solve the common processing methods difficult to solve the key. The biggest feature of CNC machining is the use of perforated belt (or tape) to control the machine for automatic processing. As the aircraft, rockets and engine parts have different characteristics: aircraft and rocket zero, component size, complex surface; engine zero, small size, high precision. So the aircraft, rocket manufacturing sector and the engine manufacturing sector selected CNC machine tools are different. In the manufacture of aircraft and rocket manufacturing to the use of continuous control of large CNC milling machine, and in the engine manufacturing both the use of continuous control of CNC machine tools, but also the use of point control CNC machine tools (such as CNC drilling machine, CNC boring machine, machining center, etc.)
4.1 process focus
CNC machine tools generally with a tool can automatically change the knife, knife, tool change process automatically by the program control, therefore, the process is more concentrated. Process brings huge economic benefits:
⑴ reduce the machine floor area, saving plant.
⑵ reduce or no intermediate links (such as semi-finished products in the middle of detection, temporary handling, etc.), both time and save manpower.
CNC machine tool processing, without manual control of the tool, a high degree of automation. The benefits are obvious.
(1) Reduced requirements for operating workers:
An ordinary machine tool of the senior workers, not a short period of time can be cultivated, and a programming without the need for NC workers very short (such as NC workers need a week can be, but also the preparation of simple processing procedures). Moreover, the NC workers in the CNC machine tools on the parts than ordinary workers in the traditional machine tool parts processing accuracy, time to save. ⑵ reduce the labor intensity of workers: NC workers in the processing process, most of the time excluded from the processing process, very labor-saving.
⑶ product quality and stability: CNC machine tool processing automation, eliminating the general machine workers on the fatigue, careless, estimated and other human error, improve product consistency.
⑷ high processing efficiency: CNC machine tools such as the automatic tool change so that the processing process is compact, improve labor productivity.
4.3 flexible highy
Traditional machine tools, although flexible, but inefficient; and the traditional plane, although the efficiency is high, but the adaptability of the parts is poor, rigid, poor flexibility, it is difficult to adapt to the fierce competition under the market economy Product frequently modified. As long as the program changes, you can in the CNC machine tools on the processing of new parts, but also automated operation, flexible and efficient, so CNC machine tools can be well adapted to market competition.
4.4 strong ability
The machine can accurately process all kinds of contours, and some contours can not be processed on ordinary machine tools. CNC machine tools are particularly suitable for the following occasions:
1, not scrapped parts.
2, the development of new products.
3, the urgent need for processing.
5. NC programming
5.1 Program structure
A block is a continuous block that can be processed as a unit, and it is actually a program in a CNC machining program. The main part of the part processing program consists of several blocks. Most blocks are used to instruct the machine to complete or perform an action. The block is made up of size words, non-size words, and block end instructions. When writing and printing, each block generally occupies one line, as is the case when the program is displayed on the screen.
5.2 Program format
The conventional machining program consists of a start character (a single column), a program name (a single column), a program body, and a program end instruction (typically a single column). At the end of the program there is a program end character. The program start character is the same character as the program end character:% in the ISO code, ER in the EIA code. The program end instruction can be used M02 (program concatenation) or M30 (tape end). CNC machine tools are generally run using a stored program, and M02 and M30 have in common that the spindle, coolant and feed are stopped and the control system is reset after completing all the other instructions in the block. M02 and M30 are fully equivalent when used on some machines (systems), and on other machines (systems), the following are used: the end of the program with M02, the cursor stops at the end of the program after the end of the automatic run End of the program with M3O running, automatic operation after the end of the cursor and the screen display can automatically return to the beginning of the program, press the start button to run the program again. Although M02 and M30 allow a program block to be used in conjunction with other program words, it is best to separate it or share only one block with the sequence number.
The program name is located before the program body, after the start of the program, it is generally exclusive. There are two forms of program name: one is the provisions of the English word (multi-use O) at the beginning, followed by a number of digits followed. The maximum number of digits allowed by the number of instructions, the common is two and four. This form of program name can also be called program number. Another form is that the program name by the English word, digital or English, digital mix, the middle can also join the “-” number. This form makes the user naming program more flexible, for example, in the LC30 CNC lathe processing part of the drawing number 215 of the third process of the process, can be named LC30-FIANGE-215-3, which give use, storage And retrieval to bring great convenience. Program name with which form is determined by the numerical control system.
N0 G92 X0 Y0 Z0
N5 G91 G00 X50 Y35 S500 MO3
N10 G43 Z-25 T01.01
N15 G01 G007 Z-12
N20 G00 Z12
N30 G01 Z-17
N35 G00 G44 Z42 M05
N40 G90 X0 Y0
5.3 segment format
The rules for the arrangement of words, characters, and data in a block are called block format. NC history has been used in fixed sequence format and delimiter (HT or TAB) block format. These two block formats are out of date, widely using word address variable block format, also known as word address format. In this format, the program word length is not fixed, the number of program words is variable, the vast majority of numerical control system allows the order of the program word is arbitrarily arranged, it is variable block format. However, in most cases, in order to write, input, check and proofreading convenience, program words in the program used in a certain order.
CNC machine tools in the programming manual in a detailed format to specify the details of the preparation of the program: the use of programming characters, the program block in the order of words and word length. E.g:
/ NO3 G02 X + 053 Y + 053 I0 J + 053 F031 S04 T04 M03 LF
X + 053, Y + 053 that the end of the processing of the coordinates of the arc; I0, J + 053 that the processing of the circle F03 is the machining speed; S04 is the spindle speed; T04 is the tool number of the tool used; M03 is the auxiliary function instruction; LF block end instruction; / is the skip selection instruction. The function of the skip selection instruction is that the operator can make a selection or non-execution of the program in the program with the step selection instruction. The method of selection is usually done by turning the skip selector switch on the operation panel to ON or OFF to implement the program block with “/” not executed or executed.
5.4 Execute the program
The processing program sometimes encounters a situation in which a set of blocks appears multiple times in a program, or it is used in several programs. We can extract this set of procedures, named after a separate storage, this group of programs is a subroutine. A subroutine is a processing program that can be called by an appropriate machine control instruction, which is generally of an independent meaning in processing. The program that calls the instruction of the first subroutine is called the main program. The instruction of the subroutine program is also a program block. It is usually composed of subroutine call instruction, subroutine name and invocation number. The specific rules and format are the same as the system. For example, it is also called “Call 55 subroutine once”, FANUC system uses ” M98 P55. “, While the United States AB system with” P55x “.
Subroutines can be nested, that is, a layer of layers. The relationship between the upper layer and the next layer is the same as the relationship between the main program and the first subroutine. Can be set up to the number of layers, determined by the specific numerical control system. Subprograms are in the same form and composition as the main program: the first line is the subroutine number (name), and the last line is the “subroutine end” instruction, which is the subroutine body. However, the main program end of the instruction is to end the main program, so that the NC system reset, the instruction has been standardized, the system uses M02 or M30; and subroutine end instruction is the end of the subroutine, return to the main program or a subroutine , The instructions of the system is not unified, such as FANUC system with M99, Siemens system with M17, the United States A-B company’s system with M02 and so on.
The user macro (program) can be used in the NC program. The so-called macro program is a subroutine with variables, in the program call the macro program called the user macro command, the system can use the user macro function called user macro function. Execute only need to write the user macro command, you can perform its user macro function.
The biggest feature of the user macro is:
● You can use variables in user macros;
● You can use calculators, steering statements, and multiple functions
● You can assign a variable with a user macro command.
CNC machine tools using group technology for parts processing, can expand the volume, reduce the amount of programming, improve economic efficiency. In the group processing, the parts will be classified, the preparation of such parts processing procedures, without the need for each part of a program. In the processing of the same type of parts is only the size of different, the main advantage of using the user macro can be used to replace the specific value of the variable, to the actual processing, only the actual size of this part of the value of the user macro command can be assigned to variables.
6. Processing principles
⑴ on the process of processing can not affect the next process positioning and clamping.
⑵ first inside and outside, that is, the first internal cavity (hole) of the processing, after the shape of the processing.
⑶ with the same installation or use of the same tool processing process, the best continuous to reduce the repositioning or tool change caused by mistaken.
⑷ in the same installation, should be carried out on the workpiece rigidity of the smaller process.
6.1 Machining routes
CNC lathe feed processing means that the turning tool from the knife point (or machine fixed origin) began to move until the return to the point and the end of the path through the processing procedures, including cutting the path and cutting tools cut, cut out non- Cutting the empty path.
The feed route for finishing is basically carried out along the contours of its parts, so the focus of the feed path is to determine the feed route for roughing and empty travel.
In the processing of CNC lathes, the processing route to determine the general to follow the following principles.
① should be able to ensure the accuracy of the workpiece and surface roughness.
② the shortest processing route, reduce the empty travel time, improve processing efficiency.
③ as far as possible to simplify the calculation of the workload, simplify the processing procedures.
④ For some reusable procedures, subroutines should be used.
So that the processing program has the shortest feed route, not only can save the entire process of the implementation of the time, but also to reduce the number of unnecessary tool consumption and machine tool feed sliding parts. The type and implementation of the shortest feed route are as follows.
⑴ the shortest cutting feed route. Cutting the shortest feed route, can effectively improve production efficiency and reduce tool wear. Arrange the shortest cutting feed route, but also to ensure that the workpiece rigidity and processing technology and other requirements.
⑵ the shortest flight route.
① clever use of knife point. A general case of roughing with a rectangular loop. The setting of the tool point A is to take into account the need to facilitate the process of grinding and other machining tools, it is set in the farther away from the blank position, at the same time, the knife point and its knife point coincides with
② clever set knife point. In order to consider the convenience and safety of the tool change, sometimes the tool change point is also set at a distance from the blank
Position, then, when the second knife, the car when the empty travel route must also be longer; if the second knife tool change point is also set at the point of the point, you can shorten the air Travel distance.
③ reasonable arrangements for “zero” route. In order to simplify the calculation process and facilitate the verification, the programmer sometimes returns the end of the tool after each tool is processed, and by returning the “return to zero” operation instruction, all of which are returned to the tool point Location, and then follow the follow-up procedure. This will increase the distance of the feed route and reduce the production efficiency. Therefore, in the reasonable arrangement of “return to zero” route, should make the end of the knife and the starting point of the distance between the knife as short as possible. Or zero, to meet the shortest requirements of the feed route. In addition, in the choice of return to the knife point instructions, without interference, as far as possible under the premise of using x, z axis two-way simultaneous “back to zero” instruction, the function “zero” route is the shortest.
⑶ large margin blank stepping cutting feed route. Lists the cutting of two kinds of excess margins
To the route. Is the wrong ladder cutting line, according to the order of 1 bucket 5 cutting, each cutting the remaining margin is equal, is the correct step cutting feed route. Because the same amount of knife in the back.
⑷ Continuous cutting feed route for part contour finishing. Finishing of the contours of the parts can be done by cutting a knife or a knife. The completion of the contours should be continuous processing from the last knife, this time, the tool into the retreat position to choose the appropriate, try not to arrange in a continuous contour cut and cut or tool change and pause, so as to avoid sudden changes in cutting force And undermine the balance of the process system. Resulting in scratches on the contours of the parts, mutations in shape, or stuck marks.
⑸ special feeding routes. In CNC turning, under normal circumstances. The longitudinal feed of the tool is fed in the negative direction of the coordinates, but it is not advisable to arrange the feed route in its conventional negative direction. May even damage the workpiece.
6.2 Advantages and Disadvantages
CNC machining has the following advantages: ① a large number of tooling to reduce the number of complex processing parts do not need complex tooling. If you want to change the shape and size of parts, only need to modify the parts processing procedures for new product development and modification. ② processing quality and stability, high precision, repeat the high precision, to meet the processing requirements of the aircraft. ③ more varieties, small batch production under the conditions of higher production efficiency, can reduce the preparation of production, machine adjustment and process inspection time, and because the use of the best cutting and reduce the cutting time. ④ can be processed conventional methods difficult to process the complex surface, and even processing some of the processing can not be observed parts. The drawback of CNC machining is that machine equipment is expensive and requires a high level of maintenance personnel.
7. Tool selection
7.1 Select the tool
1, select the principle of CNC tool
Tool life and cutting the amount of closely related. In the development of cutting the amount, should first select a reasonable tool life, and reasonable tool life should be based on the optimal target. Generally the highest productivity of the tool life and the lowest cost of the tool life of two, the former according to the minimum single-person work to determine the target, according to the lowest cost of the process to determine the target.
Select the tool life can be considered the following points according to the complexity of the tool, manufacturing and sharpening to choose the cost. Complex and high precision tool life should be selected higher than single blade tools. For the machine can be indexable tool, due to tool change time is short, in order to give full play to its cutting performance, improve production efficiency, tool life can be selected lower, generally take 15-30min. For the knife, tool change and adjust the knife more complex multi-knife machine tools, combined machine tools and automated processing tools, tool life should be selected higher, especially to ensure tool reliability. The productivity of a process in the workshop limits the productivity of the entire workshop, the tool life of the process to be selected lower When a process unit time to share the full cost of the plant, the tool life should also be selected Lower Large pieces of finishing, in order to ensure that at least one time to complete the knife, to avoid cutting the middle of the tool change, tool life should be part of the accuracy and surface roughness to determine. Compared with the ordinary machine tool processing methods, CNC machining on the tool put forward a higher demand, not only need good grass, high precision, and requires dimensional stability, high durability, broken and row of the altar at the same time require easy installation and adjustment, so to To meet the high efficiency of CNC machine tools. CNC tools used in the machine tool often used to adapt to high-speed cutting tool materials (such as high-speed steel, ultra-fine-grained carbide) and the use of indexable blade.
2, select the CNC turning tool
CNC turning tools commonly used in the general sub-forming turning tools, sharp turning tools, arc-shaped turning tools and three categories. Molded knives are also known as molds, and the contours of their machined parts are entirely determined by the size and size of the tool edge. CNC turning, the common molding tool has a small radius of circular turning tools, non-rectangular slot knife and thread knife and so on. In CNC machining, should be used with or without the use of turning tools. A sharp turning tool is a turning tool characterized by a linear cutting edge. The tip of this type of turning tool is made up of straight main and minor cutting edges, such as 900 internal and external circular turning tools, left and right end turning tools, grooving (cutting) Hole knife. The geometric parameters of the geometric tool (mainly geometric angle) are chosen in much the same way as ordinary turning, but should be taken into account in conjunction with the characteristics of CNC machining (eg, machining routes, machining interventions, etc.) and taking into account the tool tip itself strength.
Second, arc-shaped turning tool. An arc-shaped turning tool is a turning tool characterized by a circular arc-shaped cutting edge with a small roundness or a linear profile error. The arc of the turning edge of the arc is the tip of the arc-shaped turning tool, and the knife point is not on the arc, and on the center of the arc. The arc-shaped turning tool can be used to turn inside and outside the surface, especially suitable for turning a variety of smooth connection (concave) molding surface. Select the radius of the radius of the knife should be considered two arc cutting edge of the arc radius should be less than or equal to the concave surface of the smallest radius of curvature, in order to avoid the formation of dry and shallow The radius should not choose too small, otherwise not only difficult to manufacture, But also because the tip strength is too weak or the knife body cooling capacity caused by poor damage to the car.
3, select the CNC milling tool
In the CNC machining, the milling plane parts inside and outside the contour and milling plane commonly used flat end mill, the tool parameters of the empirical data are as follows: First, the milling radius RD should be less than the minimum radius of curvature of the parts Rmin, generally take RD = (0.8 to 0.9) Rmin. Second, the processing height of parts H <(1 / 4-1 / 6) RD, to ensure that the knife has enough rigidity. Third, with the flat end mill milling the bottom of the inner slot, due to the bottom of the groove at the end of the need to overlap, and the tool edge of the role of the radius of the Re = Rr, the diameter of d = 2Re = 2 (Rr) Take the tool radius as Re = 0.95 (Rr). For some of the three-dimensional and variable-angle profile contour processing, commonly used spherical cutter, ring cutter, drum cutter, tapered cutter and disk cutter.
Most of the CNC machine tools using serialization, standardization of the tool, on the indexable machine folder outside the turning tool, the end of the knife and so on the knife handle and the head has a national standard and serialized models for the processing center and a permanent tool Machine tools, tool holders have been serialized and standardized provisions, such as taper shank tool system standard code for the TSG-JT, straight handle tool system standard code for the DSG-JZ, in addition to the selected tool, in the Before use, the tool size must be rigorously measured to obtain accurate data, and the operator will enter the data into the data system, the program calls to complete the processing process, which processed a qualified workpiece.
7.2 Knife point
Therefore, at the beginning of the program execution, it is necessary to determine the position at which the tool starts to move in the workpiece coordinate system. This position is the starting point of the tool relative to the movement of the workpiece when the program is executed. In this case, So called the program starting point or knife point. This starting point is generally determined by the knife, so the point also known as the knife point. In the preparation of the program, to correctly select the location of the knife point. The principle of setting the tool point is: to facilitate numerical processing and simplify the programming. Easy to find and in the processing process to facilitate inspection; caused by the processing error is small. The tool point can be set on the machined part, or it can be set on the fixture or machine tool. In order to improve the machining precision of the part, the point should be set on the design basis or technology base of the part. When the machine is actually operated, the tool point of the tool can be placed on the tool point by manual tool setting, that is, the coincidence of “knife point” and “knife point”. The so-called “knife point” refers to the positioning of the tool reference point, turning tool point for the tool nose or tool nose arc center. Flat end mill is the intersection of the tool axis and the bottom of the tool; the ball end mill is the ball of the ball, the drill is the drill tip and so on. With manual knife operation, the knife is low, and low efficiency. And some factories using optical knife on the knife, knife, automatic knife set, etc., to reduce the knife time, improve the accuracy of the knife. During the machining process, the tool change point should be specified. The so-called “tool change point” refers to the position of the tool holder when the tool change, the tool change point should be set in the workpiece or fixture to the outside, to change the workpiece and other parts without reference.
7.3 Cutting amount
In NC programming, the programmer must determine the amount of cutting per process and write it in the form of an instruction. Cutting the amount of spindle speed, including the amount of knife and feed speed. For different processing methods, the need to use a different amount of cutting. The principle of cutting the amount of choice is: to ensure the accuracy of parts and surface roughness, give full play to the cutting tool performance to ensure a reasonable tool durability, and give full play to the performance of the machine to maximize productivity and reduce costs.
1, to determine the spindle speed
The spindle speed should be selected according to the permissible cutting speed and the workpiece (or tool) diameter. The formula is: n = 1000 v / 7 1D where: v? Cutting speed, the unit is m / m dynamic, determined by the durability of the tool; n one spindle speed, the unit r / min, D for the workpiece diameter Or tool diameter in mm. Calculate the spindle speed n, and finally to select the machine or some of the speed closer.
2, to determine the feed rate
Feeding speed is an important parameter in the cutting amount of CNC machine tools. It is mainly selected according to the machining precision and surface roughness requirements of the parts and the material properties of the tool and workpiece. The maximum feed rate is limited by the machine stiffness and feed system performance. The principle of determining the feed rate: When the quality requirements of the workpiece can be guaranteed, in order to improve production efficiency, you can choose a higher feed rate. Generally in the range of 100 to 200mm / min; in cutting, processing deep hole or high-speed steel cutting tool, it is appropriate to choose a lower feed rate, generally in the range of 20 to 50mm / min selected; when the processing accuracy, the surface Roughness requirements are high, the feed rate should be selected smaller, generally in the range of 20 – 50mm / min selected; tool empty trip, especially the long distance “back to zero”, you can set the machine CNC system settings The maximum feed speed.
3, to determine the amount of back to eat knife
The amount of kneading knife according to the machine, the workpiece and the stiffness of the tool to decide, in the rigidity of the conditions allowed, should be as much as possible to make the amount of knife back to the workpiece allowance, which can reduce the number of passes and improve production efficiency. In order to ensure the quality of the processing surface, a small amount of finishing allowance can be retained, generally 0.2 to 0.5 m m. In summary, the specific value of the cutting amount should be determined by analogy according to the machine performance, the relevant manual and the actual experience.
At the same time, the spindle speed, cutting depth and feed speed can be adapted to each other to form the best amount of cutting.
The cutting amount is not only an important parameter that must be determined before the machine is adjusted, but also its numerical value is very important to the processing quality, processing efficiency and production cost. The so-called “reasonable” cutting amount refers to the full use of tool cutting performance and machine power performance (power, torque), in ensuring the quality of the premise, to obtain high productivity and low processing costs of cutting costs.
8. Operational safety
8.1 civilized production
CNC machine tool is a high degree of automation, the structure of the more complex advanced processing equipment, in order to give full play to the advantages of machine tools, improve production efficiency, manage, use, repair CNC machine tools, technical staff quality and civilization production is particularly important The Operators in addition to familiar with the performance of CNC machine tools, so skilled operation, but also must develop a good civilized production habits and rigorous work style, with good professional quality, sense of responsibility and spirit of cooperation. Operation should do the following:
⑴ strict compliance with the safety of CNC machine operating procedures. Do not operate the machine without professional training.
⑵ strict compliance with commuting, shift system.
⑶ do with good, good machine tools, with a strong sense of responsibility.
⑷ to keep the environment around the CNC machine clean and tidy.
⑸ the operator should wear a uniform, work shoes, not wear, wear dangerous clothing accessories.
8.2 Operating procedures
In order to properly and rationally use CNC machine tools, reduce the incidence of failure, operation methods. The machine manager can agree to operate the machine.
⑴ before the start of the precautions
1) The operator must be familiar with the performance of the CNC machine tools, operating methods. The machine manager can agree to operate the machine.
2) Before the machine is energized, check whether the voltage, air pressure and oil pressure meet the working requirements.
3) Check whether the movable part of the machine is in normal working condition.
4) Check the table for offside, over limit status.
5) Check the electrical components are solid, whether the wiring off.
6) Check if the machine ground wire is connected to the ground of the workshop (it is especially important for the first power on).
7) has been completed before the start of the work before you can close the power switch.
⑵ start the process of attention
1) strictly in accordance with the machine manual in the boot sequence to operate.
2) Under normal circumstances must first start the machine back to the machine reference point operation, the establishment of machine tools to do the standard system.
3) after the machine to run the machine running more than 15min, so that the machine to achieve a balanced state.
4) after the shutdown must wait for more than 5min before they can start again, there is no special circumstances can not be arbitrary frequent boot or shutdown operation.
⑶ debugging process considerations
1) edit, modify, debug a good program. If the first test must be run empty, to ensure that the program is correct.
2) according to the process requirements to install, debug a good fixture, and remove the positioning surface of the iron and debris.
3) according to the positioning requirements of the workpiece, to ensure that the correct and reliable positioning. There must be no loosening of the workpiece during machining.
4) The tool to be used is installed. If the machining center is used, the tool number on the magazine must be exactly the same as the tool number in the program.
5) according to the workpiece on the programming origin of the knife, the establishment of the workpiece coordinate system. If more than the tool, then the rest of the tool were length compensation or tool nose position compensation.
9.3D analog CNC machining
3D technology can make CNC machining machine operation more accurate, to avoid damage to the instrument to ensure the accuracy and efficiency of product processing. Through a series of complex algorithms to calculate the working trajectory of the model, to achieve metal processing, metal cutting and other analog CNC machining.
11.List of CNC machining shops
|North Bay Machining Centre Inc||Canada||Contract Manufacturing, custom and production machine shop.|
|1343080 Alberta Ltd||Canada||custom sheet metal production, CNC MACHINING, PRECISION METAL FABRICATION & MACHINING, Precision Machining, CNC Laser and Plasma Cutting.|
|Rapid Parts Manufacturing Inc.||Canada||Precision CNC Lathe machining, CNC MILLING MACHINING, custom machined part.|
|PVC Industrial Products Limited||Canada||plastics manufacturing, custom plastic fabrication shop.|
|Harco Enterprises Ltd.||Canada||manufacturing plastic items mainly for the toy and advertising industries, Machine shop, Moulds and tooling, stainless steel machining, welding and polishing for the food industry.|
|Dun-Rite Plastics & Custom Fabrication Inc.||Canada||custom plastics fabrication, Full CNC machining.|
|Dutch Industries Ltd.||Canada||manufacturing agricultural openers and tips, Custom Fabrication.|
|Sanyo Canadian Machine Works Inc.||Canada||machining and fabrication.|
|Pydee Engineering Co. Ltd.||Canada||metal fabrication and machining.|
|Hagedorn Machinery Development & Engineering Inc.||Canada||precision machining, custom machine shop specializing in machining large fabricated steel and cast parts.|
|Ebco Industries Ltd.||Canada||custom manufacturing of metallic based products and components, machining, fabricating, and assembly of large and small components and equipment.|
|CNC-PRO||Canada||CNC ,steel fabricate and general machining, with high precision.|
|Atlantic Machining Inc.||Canada||machine shop, Producing engineered parts.|
|Sussex Engine Rebuilding Ltd.||Canada||full service machine shop that specializes in High Performance engines and Marine High Performance engines and parts.|
|RJB MACHINING Ltd||Canada||High Precision Custom Machine Shop, CCD Camera Component Manufacturing and Water Purification Parts Manufacturing.|
|Norwest Precision Limited||Canada||Precision-machined, manufacturing of small, medium and large size components.|
|Northern Steel Ltd.||Canada||Custom fabrication of steel and specialty alloy components and process equipment, CNC machining and robotic welding.|
|LaserNett - Metal Fabrication, Laser Cutting and Laser Engraving||Canada||sheet metal laser cutting, custom metal fabrication shop.|
|Hawboldt Industries (1989) Ltd.||Canada||machining and welding.|
|Goodman Steel Ltd.||Canada||Custom job shop fabrication and machining.|
|Duny Machine Ltd.||Canada||precision machined parts.|
|Dun-Rite Plastics & Custom Fabrication Inc.||Canada||custom plastics fabrication.|
|J.B.Tool and Gauge Inc.||Canada||general machining.|
|Marlo Precision Machining||Canada||Custom machine shop.|
|Windsor Broach & Tool||Canada||CNC machining and CNC turning, Machine Tool components.|
|Weber Manufacturing Technologies Inc.||Canada||precision components for the Aerospace industry, CNC machining centres.|
|Techniprodec Ltd||Canada||design and manufacture of toolings, mold manufacturing.|
|Société D'Outillage M.R. Ltée||Canada||MANUFACTURING SPECIAL TOOLING -PRECISION MACHINING, MACHINING AND ASSEMBLY AIRCRAFT PARTS AND GROUND SUPPORT EQUIPEMENT.|
|RJB MACHINING Ltd||Canada||High Precision Custom Machine Shop Very Specialized in CCD Camera Component Manufacturing and Water Purification Parts Manufacturing.|
|Ritch-Meyer Machine & Tool||Canada||custom and production cnc machining job shop.|
|Reko Manufacturing Group||Canada||custom machining, metal cutting services.|
|Quality Performance Tooling & Machining Inc.||Canada||CNC/Tool & Die Machine Shop, CNC Milling, Turning, Molds, Jigs, Fixtures, Stamping, Progessive, Transfer & Piercing Dies, Designing and building of custom machines.|
|Perth Precision Machining & Manufacturing||Canada||precision machining fabrication, precision machining fabrication.|
|Master Shop Inc.||Canada||Tool & die making and precision machining. Metal stamping. Production machining and metal stamping.|
|MARMEN Inc.||Canada||high-precision machining, fabrication and mechanical assembly for parts of all sizes.|
|ISOTOP Machineries||Canada||Machine shop equipments.|
|IN-TOL Tool & Die Ltd.||Canada||equipped tooling and machining shop, CNC machined parts.|
|Engrenages Spécialisés inc.||Canada||gear cutting and CNC machining.|
|E. T. M. Industries Inc.||Canada||CNC machining in one plant, plastic injection molding.|
|Croatia Machine Tool of Canada Ltd.||Canada||Precision Custom & Production Machine Shop, LARGE MACHINING.|
|Campli Metals Inc.||Canada||large jobbing shop, custom machining and mill roll turning and grinding.|
|BW Manufacturing||Canada||custom metal fabrication shop, shearing, forming, machining, milling and welding of mild steel and stainless steel.|
|BKW TECHNOLOGIES Inc.||Canada||machine shop that design and build custom machinery, on site services, CNC machining, precision machining, tool and die, all types of welding.|
|Axis Tool & Gauge Inc.||Canada||Full service machine shop servicing Areospace , Power generation & Nuclear industry.|
|A.J. Machine Works Inc.||Canada||Production CNC machine shop serving the manufacturing, Forestry, Oil Field, Marine, Automotive and Recreational sectors.|
|583622 Ontario Limited||Canada||CAD/CAM Design, Mould Shop, 3 and 5 Axis CNC Machining Wood Pattern shop, Wood Models Mould Assembley.|
|Wong's Machine & Tool Co. Ltd.||Canada||Contract Manufacturing.|
|Wolftek Industries Inc.||Canada||Contract Manufacturing.|
|Universe Machine Corporation||Canada||machining services offer large and specialized equipment. Equipment include Surface Grinding, CNC machining centers and lathes, horizontal and vertical boring mills, Milling machines, drill presses and shapers.|
|T H Relief Valve & Machining Ltd.||Canada||General machine shop.|
|Sturdell Industries Inc.||Canada||Custom Mold and Tool and Die makers, Six sided machining, Gundrilling, one-stop-shop for all Mold or Tool & Die material & processing requirements.|
|Speedox Custom Machining Inc||Canada||CNC Job Shop, CNC Milling & Turning components.|
|Scotia Machining Services Ltd.||Canada||Contract Manufacturing, Machine Shops.|
|RT Prime Industries Group Ltd.||Canada||manufacturing precision metal and custom plastic parts, components and assembled products in China. modern CNC machining, stamping, molding, extruding, and casting.|
|Revolve Industries Inc.||Canada||custom machining, Contract Manufacturing.|
|R.P. Hawboldt Machining (1998) Ltd.||Canada||Machine Shop C.W.B. Certified Recieved Michelin North America Award for Quality.|
|R & R Machine & Tool Inc.||Canada||Machine shop services include precision machining and grinding, prototyping, modify/manufacture equipment & die component parts, jigs & fixtures.|
|Quality Machining Services Ltd.||Canada||Machine Shops.|
|Precimax Ltd||Canada||machine shop specializing in custom built machinery, instruments & components. Manufacturing of instruments and components in production or per unit.|
|Perth Precision Machining & Manufacturing||Canada||calibre precision machining fabrication and assembly company located in Stratford Ontario Canada.|
|North Bay Machining Centre Inc||Canada||custom and production machine shop.|
|Nesbitt Engineering Limited||Canada||machine shop specializing in general machine shop & industrial repairs, sheet metal work, welding, metallizing and portable line boring.|
|Mountain Machining||Canada||Machine Shop. General machining, custom fabrication, welding, mechanical design, engineering consulting. Prototypes, one-offs, custom parts, general repair, low-volume production.|
|MNK Tool Inc.||Canada||machine shop with CNC turning centers and machining centers.|
|Milton Machine Shop Ltd||Canada||General Machine shop services. Custom machining.|
|Metric Machine (1998) Ltd.||Canada||Contract Manufacturing.|
|Metal Action Machining Ltd.||Canada||CNC Machine Shop offering one-stop manufacturing service, manufacturing of certified Aerospace Parts.|
|Mecachrome CANADA (2009) Inc.||Canada||design and manufacturing of value added parts, systems and structural assemblies.|
|McEwan Machining Ltd.||Canada||machining and manufacturing shop.|
|MacGregor's Custom Machining Ltd.||Canada||Machine Shops Industrial Sales.|
|Lumar Machining & Mfg. Ltd.||Canada||contract machining shop with a full range of machining services, customer and Production Machining, the Manufacturing of Jigs & Fixtures, Powder Metal related Tooling and high precision spindle components.|
|Levy's Machine Works Ltd.||Canada||Contract Manufacturing, custom and production machine shop.|
|Leemark Enterprises Inc||Canada||machined parts, CNC machining and manufacturing Wiper Dies and Forging Dies.|
|KK Technologies Inc.||Canada||milling and machining shop manufacuring components.|
|Keen Design and Machining Inc.||Canada||Contract Manufacturing.|
|Implant Mechanix Incorporated||Canada||micro machining services, offer complete prototyping and low volume production including 5 axis CNC milling, CNC turning, precision grinding, sinker and wire EDM, laser welding and 3D printing.|
|Ideal Gear & Machine Works||Canada||full service gear manufacturer and designer, machine shop.|
|Horton Machine||Canada||Custom Machining.|
|GPL Machine & Tool Inc.||Canada||machining and manufacturing shop.|
|Gestion Industrielle Maintenance Man inc.||Canada||parts machining.|
|Eagle Specialty Machining||Canada||machine shop, machining from stainless steel to brass and plastic materials. manufacturing all types of products.|
|Diacarb||Canada||high precision machine shop, production parts in low and high volumes on complexe CNC equipement.|
|Dhillon Machine Shop Inc.||Canada||custom precision machine shop specializing in the machining of components for the telecommunication industry.|
|Cut Rite Machining||Canada||cnc machined products, job shop.|
|Central Interior Rebuilders (1998) Ltd.||Canada||Machine Shop specializing in: cylinder heads, blocks & casting, hard chrome plating, crankshaft grinding, align boring, machining, hydraulic remanufacturing.|
|Canak Industries||Canada||machine shop, custom machining.|
|Can West Machinery (2012) Ltd.||Canada||precision machining, welding, fabrication and professional rebuilding of babbitt lined bearings.|
|BGM Metalworks Inc.||Canada||Full service precision machining and fabrication company specializing in customized steel fabrication and erection, stainless steel welding and fabrication, sanitary piping, and aluminum fabriation, machine shop.|
|Becland Stamping & Machining Corp.||Canada||General & Custom Machining (conventional & CNC); Metal Fabrication.|
|B.C. Precision Inc.||Canada||Contract Manufacturing.|
|ASDAC C.N.C. Machining Ltd.||Canada||machining and manufacturing shop.|
|Affinity Manufacturing Ltd.||Canada||custom machine shop capable of manufacturing a multitude of precision components.|
|Aerial Industries Inc.||Canada||Toronto CNC machining & manufacturing shop.|
|Abipa Canada inc.||Canada||Contract Manufacturing.|
|9200-3821 Qc Inc.||Canada||CNC machine shop, high precision turning and machining work.|
|414163 Ont. Ltd||Canada||Precision Machine Shop,CNC Machining Centers, machined parts.|
|1477638 Ontario Limited||Canada||custom made fabrication, welding and machining.|
|1254909 ONT LTD||Canada||custom machining welding and fabricating.|
|Wong's Machine & Tool Co. Ltd.||Canada||machine shop, manufacturing plastic bag converting machinery.|
|Laser Concepts | Machining & Fabrication||US||full-service metal machining and fabrication shop.|