chengcg – Page 94 – CNC Machining & Turning, Milling, Metal parts

The NC machining steps of parts are as follows:

① According to the drawing and process plan of the parts to be processed, the processing program is written with the specified code and program segment format; ② the written processing program instruction is input into the CNC device of the machine tool; ③ after the NC device processes the program (code), it sends control signals to the servo drive mechanism and auxiliary control device of each coordinate of the machine tool; ④ the servo mechanism receives the execution letter After No. 1 command, the machine drives all moving parts of the machine tool and controls the required auxiliary actions; 5) the machine tool automatically processes qualified parts;

1. Stipulation of machine tool coordinate system

The Cartesian and Z coordinate systems are determined by the Cartesian coordinate system and the right-hand coordinate system

The thumb, index finger and middle finger of the right hand are 90 ° to each other. The thumb represents the X coordinate, the index finger represents the Y coordinate, and the middle finger represents the Z coordinate;

The thumb points in the positive direction of X coordinate, the index finger points in the positive direction of Y coordinate, and the middle finger points in the positive direction of Z coordinate;

1. Stipulation of machine tool coordinate system

The Cartesian and Z coordinate systems are determined by the Cartesian coordinate system and the right-hand coordinate system

The thumb points in the positive direction of X coordinate, the index finger points in the positive direction of Y coordinate, and the middle finger points in the positive direction of Z coordinate;

3. Workpiece coordinate system and program origin

Definition: the workpiece coordinate system is used by the programmer when programming. The programmer selects a point on the workpiece as the origin (also known as the program origin), and establishes a coordinate system, which is called the workpiece coordinate system. Once the workpiece coordinate system is established, it will remain valid until it is replaced by a new one.

CNC machining features:

1. High machining precision

It is generally between 0.001-0.1mm. Not affected by the complexity of parts, automatic compensation.

2. Stable quality

For the same batch of parts, the machining path is identical, avoiding human error. Part one

The quality is stable.

3. High production efficiency

Large cutting parameters, automatic speed change, automatic tool change and other auxiliary operation automation are adopted

Function; the auxiliary time is greatly shortened (omitting marking work, reducing fixture design and adjustment,

There is no need for inspection and measurement between processes), and the productivity is 3-4 times higher. Spindle speed and feed range

Larger than ordinary machine tools.

4. Flexibility and adaptability

When the multi axis linkage and changing the machining parts, only the NC program needs to be replaced. Adapt to many varieties and small batch

Mass production.

5. It can realize multi-purpose and centralized operation

Automatic tool change machining center, in the case of clamping, can almost complete the parts

All processes. Reduce clamping error and save transportation, measurement and clamping between working procedures

Wait for auxiliary time.

6. Reduce labor intensity and improve working conditions

Automatic continuous processing simplifies the operation of workers and greatly reduces the labor intensity.

7. It is conducive to production management

It can accurately calculate the working hours, reduce the management of fixtures and semi-finished products, and reduce misoperation.

8. It is conducive to the development of computer control and management.

Digital signal is used to describe and control, based on program processing, which is convenient for computer networking and realize set

Medium control and management

9. It can reduce the production cost of the enterprise, improve the economic benefit of the enterprise, the quick response ability of the market and the competitiveness.

High quality, investment and management of maintenance personnel

Summary of NC machining:

1、 Question: how to divide the process?

Answer: generally, the division of NC machining process can be carried out according to the following methods:

(1) Tool centralized sorting method is to divide the process according to the tool used, and use the same tool to process all the parts that can be completed. Use a second knife, a third knife to do whatever else they can. In this way, the number of tool changes can be reduced, the idle travel time can be compressed, and the unnecessary positioning error can be reduced.

(2) According to the structural characteristics of the parts, the processing parts can be divided into several parts, such as inner shape, shape, surface or plane. Generally, the plane and positioning surface are processed first, and then the hole; the simple geometric shape is processed first, and then the complex geometric shape; the parts with low precision are processed first, and then the parts with high precision requirements are processed.

(3) According to the method of rough and finish machining, the parts which are easy to deform need to be adjusted because of the possible deformation after rough machining, so generally speaking, the working procedure should be separated for rough and finish machining.

To sum up, in the division of working procedures, it is necessary to flexibly master the structure and technology of parts, the function of machine tools, the number of NC machining contents of parts, installation times and the production organization of the unit. In addition, it is suggested that the principle of process centralization or process decentralization should be adopted according to the actual situation, but it must be reasonable.

2、 Q: what principles should be followed in the arrangement of processing sequence?

Answer: the arrangement of processing sequence should be considered according to the structure and blank condition of parts, as well as the need of positioning and clamping. The key point is that the rigidity of the workpiece will not be damaged. Generally, the sequence should be carried out according to the following principles:

(1) The processing of the previous process cannot affect the positioning and clamping of the next process, and the machining process of general machine tool should be considered comprehensively.

(2) The inner shape and inner cavity processing sequence is carried out first, and then the contour processing process is carried out.

(3) In order to reduce the times of repeated positioning, tool changing and pressing plate moving, the same positioning and clamping methods or the same tool processing process should be well connected.

(4) For multiple procedures in the same installation, the process with less damage to the rigidity of the workpiece should be arranged first.

3、 Question: which aspects should be paid attention to in determining the clamping mode of workpiece?

A: in determining the positioning reference and clamping scheme, the following three points should be noted:

(1) Strive to design, process, and programming calculation of the benchmark unity.

(2) The clamping times should be reduced as much as possible, and all the surfaces to be machined can be processed after one positioning.

(3) Avoid using manual adjustment plan.

(4) The fixture shall be open, and its positioning and clamping mechanism shall not affect the tool feeding during processing (such as collision). In case of such situation, the vise or bottom plate drawing screw can be used for clamping.

4、 Question: how to determine the tool setting point is reasonable? What is the relationship between workpiece coordinate system and programming coordinate system?

1. The tool setting point can be set on the part to be processed, but pay attention to that the tool setting point must be the reference position or the position that has been finished. Sometimes, the tool setting point will be damaged after the × * * process, which will make the second process and the subsequent tool setting point impossible to find. Therefore, when setting the tool in the × * * process, it is necessary to set up a relative tool setting where there is a relatively fixed dimension relationship with the positioning reference In this way, the original tool setting point can be retrieved according to the relative position relationship between them. This relative tool setting position is usually set on the machine tool table or fixture. The selection principles are as follows:

1) It’s easy to find the right one.

2) Programming is convenient.

3) The tool setting error is small.

4) It is convenient to check during processing.

2. The origin position of the workpiece coordinate system is set by the operator himself. After the workpiece is clamped, it is determined by tool setting. It reflects the distance position relationship between the workpiece and the zero point of the machine tool. Once the workpiece coordinate system is fixed, it is generally not changed. The workpiece coordinate system and the programming coordinate system must be unified, that is, during machining, the workpiece coordinate system and the programming coordinate system are consistent.

5、 Question: how to choose the cutting route?

Tool path refers to the path and direction of the tool relative to the workpiece in the process of NC machining. The reasonable choice of machining route is very important because it is closely related to the machining accuracy and surface quality of parts. The following points are mainly considered in determining the tool path:

1) Ensure the machining accuracy of parts.

2) It is convenient for numerical calculation and reduces the workload of programming.

3) To find a short processing route, reduce the idle time to improve processing efficiency.

4) Minimize the number of program segments.

5) To ensure the surface roughness of workpiece contour after machining, the final contour should be processed continuously by the next tool feed.

6) The tool’s advance and retreat (cut in and cut out) routes should also be carefully considered, so as to minimize tool marks caused by tool stopping (elastic deformation caused by sudden change of cutting force) at the contour, and to avoid scratching the workpiece due to vertical cutting on the contour surface.

6、 Q: how to monitor and adjust during machining?

After the alignment and program debugging are completed, the workpiece can enter the automatic processing stage. In the process of automatic machining, the operator should monitor the process of cutting to prevent the quality problems and other accidents caused by abnormal cutting.

On the cutting process

CNC processing skills:

1. The speed of white steel knife should not be too fast.

2. Copper roughing less white steel knife, more use flying knife or alloy knife.

3. When the workpiece is too high, it should be sliced with different length of knife.

4. After roughening with a big knife, use a small knife to remove the remaining material to ensure that the allowance is consistent.

5. The plane should be processed with flat bottom cutter and less ball cutter to reduce the processing time.

6. When the copper worker cleans the angle, first check the size of R on the angle, and then determine how large the ball knife is used.

7. The four corners of the calibration plane should be smooth.

8. If the slope is an integer, use the slope cutter to process, such as pipe position.

9. Before each process, think about the remaining allowance after the previous process, so as to avoid empty cutter or excessive machining.

10. Try to take simple cutting path, such as shape, grooving, single side, less walking around the same height.

11. When taking wcut, if you can walk finish, don’t go rough.

12. When the shape of the light knife is smooth, first rough and then fine. When the workpiece is too high, polish the edge first and then the bottom.

13. Set tolerance reasonably to balance machining accuracy and computer calculation time. The tolerance is set to 1 / 5 of the allowance for roughening and 0.01 for smooth knife.

14. Do more procedures to reduce the time of empty knife. Think more and reduce the chance of making mistakes. Make more auxiliary lines and auxiliary surfaces to improve the processing condition.

15. Establish a sense of responsibility and check each parameter carefully to avoid rework.

16. Be diligent in learning, good at thinking and make continuous progress. When milling non flat surface, use ball cutter more, use less end knife, do not be afraid to connect knife; small knife angle cleaning, big knife finishing; don’t be afraid of patching, proper patching can improve the processing speed and beautify the processing effect.

17. High hardness of blank material:

Better up milling, lower hardness of blank material: better forward milling, better machine tool precision, good rigidity, finish machining: more suitable for forward milling, vice versa, more suitable for finish machining of inner corner of parts by up milling. It is strongly recommended to use forward milling. Rough machining: reverse milling is better, finish machining is better: down milling is better, tool material toughness is good, hardness is low: it is more suitable for rough machining (large cutting amount processing), tool material toughness is poor, hardness is high: it is more suitable for finishing (small cutting amount processing).

18. Copper processing methods and precautions:

Before writing the cutter path, after the three-dimensional drawing is finished, the graphic center should be moved to the coordinate origin, and the high point should be moved to Z = 0 before machining. The copper male spark position can process negative reservation. Before processing, it is also necessary to check whether the clamping direction of the workpiece is the same as the graphic direction in the computer, whether the arrangement in the mold is correct, whether the fixture hinders the processing, and whether the direction of the front and rear dies match. Also check whether the tools you use are complete, and check the benchmark in the calibration table. Matters needing attention in copper processing: for the determination of spark position, the reserved amount of young male (i.e. fine male) is 0.05 ~ 0.15 and coarse male is 0.2 ~ 0.5. The specific spark position can be determined by the mold maker. Copper public has no dead corner that cannot be processed. Whether it is necessary to dismantle one more loose one. Generally, the cutter path of copper processing is as follows: big knife (flat knife) roughening – small knife (flat knife) angle clearing – ා 0; smooth knife uses spherical knife to smooth curved surface. In general, teachers use a flat knife instead of a ball knife. After a big knife, they use a small knife to make a rough cut. Then they use a large ball knife to smooth the surface, and then use a small ball knife to smooth the surface. It is not easy to use a small knife to process the dead angle that the big knife can’t pass for some small angles. It is advisable to limit the range of the knife’s travel so as to avoid too many empty knives. Copper, especially Yougong, requires high precision. The tolerance is generally 0.005 ~ 0.02 and the step distance is 0.05 ~ 0.3. When the copper is exposed to be thick, the tool passing position of the ball cutter position should be reserved, that is, the copper male shape should be opened to a depth of a knife radius. In general, the copper worker must have three datum planes when calibrating three surfaces (upper, lower, left and right). Copper material is easy to process. The feed speed and rotation speed can be faster. When roughing, the machining allowance is 0.2 ~ 0.5. Depending on the size of the workpiece, the machining allowance is large, so the cutting can be fast and the efficiency can be improved. Note: the brackets are the parameters of high-speed steel knife for steel roughening, and the above cutting speed refers to that the required profile f = 300 ~ 500, and the steel smooth cutter f = 50 ~ 200.

19. Problems of front die opening:

First of all, rotate the Copper drawing 180o in the front view or side view to turn it into the front mold drawing, and of course, add the pillow position and PL surface. If the original body needs to be reserved, do not use the mirror body method to change the Copper drawing into the front model drawing, which may be wrong (when the X direction and Y direction of the Copper drawing are asymmetric). There are two difficulties in front mold processing: the material is relatively hard; the front mold can not be easily welded and wrong. The principle of using a knife for roughening the front die is similar to that of a copper tool. However, a large knife should be used as far as possible for the front die, rather than a too small knife. It is easy to snap the knife. Generally, the handle () is used for roughening, and the round nose knife is also used for the smooth knife. Because this kind of knife is large and powerful, there is usually a problem when processing the front die with parting surface The parting surface should be accurate because of the impact of the machine, and the cavity should be left 0.2 ~ 0.5 machining allowance (reserved for spark). In this way, the surface of the die cavity can be corrected by 0.2 ~ 0.5 towards the positive direction, and the machining allowance can be set to 0 when the face is writing the tool path. When the front die is roughened or polished, it is usually necessary to limit the cutting range. Remember that the range you set is the range of the tool center, not the range of the tool boundary, not the range of the tool processing, but a larger tool radius. The common tool path method of front die roughening is surface grooving and parallel light knife. The front mold processing time division surface, the pillow position surface generally must process to the standard number, but the collision surface may leave 0

Solutions to problems in CNC machining:

1. Workpiece over cutting:

reason:

1. The tool strength is not too long or too small. Cause the tool to bounce.

2. Improper operator operation.

3. The cutting allowance is not uniform. (e.g. 0.5 for side of curved surface and 0.15 for bottom surface)

4. Improper cutting parameters (such as too large tolerance, too fast SF setting, etc.).

improve:

1. The principle of using knife: it can be big or small, short or not long.

2. Add corner clearance procedure, and the allowance should be uniform as far as possible (the allowance of side and bottom should be consistent).

3. Reasonable adjustment of cutting parameters, large margin corner rounding.

4. Using the SF function of the machine tool, the operator can adjust the speed to achieve good cutting effect.

reason:

1. The operator’s manual operation is not accurate and the number of manual operations is wrong.

2. There are burrs around the mold.

3. There is magnetism in the center rod.

4. The four sides of the mold are not vertical.

improve:

1. The manual operation should be checked carefully repeatedly, and the points should be at the same height as far as possible.

2. Deburring the periphery of the mould with an oilstone or file, wipe it with rags, and then confirm it by hand.

3. Demagnetize the center bar before parting the mold (ceramic bar or others can be used).

4. Check whether the four sides of the mould are vertical by checking the table (the verticality error is large, and the scheme should be reviewed with the fitter).

3. Knife setting:

reason:

1. The operator’s manual operation is not accurate and the number of manual operations is wrong.

2. Tool clamping error.

3. The blade on the flying knife is wrong (there is a certain error in the flying knife itself).

4. There is error between R knife and flat bottom knife and flying knife.

improve:

1. The manual operation should be checked repeatedly, and the tool setting should be at the same point as far as possible.

2. When clamping the cutting tools, blow them with air gun or wipe them with rags.

3. When the upper blade of flying knife needs to measure the cutter rod and smooth bottom surface, one blade can be used.

4. A tool setting program can avoid the error between the flying knives of R knife and flat knife.

4. Collision programming:

reason:

1. The safety height is not enough or not set (when the rapid feed G00, the cutter or chuck collides with the workpiece).

2. The tool on the program list is wrong with the tool in the actual program.

3. The tool length (edge length) and the actual machining depth on the program list are wrongly written.

4. The depth z-axis access on the program list is wrong with the actual z-axis.

5. Coordinate setting error during programming.

improve:

1. Accurate measurement of the height of the workpiece also ensures that the safe height is above the workpiece.

2. The tool on the program list should be consistent with the actual program tool (try to use the automatic program sheet or the picture to make the program list).

3. Measure the actual machining depth on the workpiece, and write the length and edge length of the tool clearly on the program sheet (generally, the length of the tool holder is 2-3mm higher than the workpiece, and the length of the blade is 0.5-1.0mm).

4. Take the actual z-axis data on the workpiece and write it clearly on the program sheet. (this operation is generally manual operation, and it should be checked repeatedly).

5. Collision Operator:

reason:

1. Depth z axis tool setting error.

2. The number of collisions and operation errors (such as: unilateral access without feed radius, etc.).

3. Use the wrong tool (e.g. D4 is processed with D10).

4. The program goes wrong (for example: a7.nc goes a9.nc).

5. The handwheel is in the wrong direction during manual operation.

6. Press the wrong direction during manual rapid feed (for example: – x press + x).

improve:

1. The depth z-axis tool setting must pay attention to the position of the tool. (bottom, top, analysis, etc.).

2. The number of collisions and operations should be checked repeatedly after completion.

3. When clamping the tool, check it with the program sheet and program repeatedly before installing it.

4. The program should go in order one by one.

5. When using manual operation, the operator should enhance the operation proficiency of the machine tool.

6. In manual rapid movement, the z-axis can be raised to the workpiece to move.

6. Surface accuracy:

reason:

1. The cutting parameters are unreasonable and the surface of workpiece surface is rough.

2. The cutting edge of the tool is not sharp.

3. The tool clamping is too long and the blade is too long.

4. Chip removal, air blowing and oil flushing are not good.

5. Programming tool feed mode, (can consider the following milling as far as possible).

6. The workpiece has burr.

improve:

1. Cutting parameters, tolerances, allowance, speed and feed settings should be reasonable.

2. The tool requires the operator to check and replace the tool from time to time.

3. The operator is required to clamp the tool as short as possible and the blade should not be too long.

4. For flat cutter, R knife and round nose knife, the speed feed setting should be reasonable.

5. Workpiece has burr: it is directly related to our machine tool, cutting tool and tool feeding mode. Therefore, we need to understand the performance of the machine tool, the edge of the burr repair

Cause analysis and prevention of over cutting and tool collision in CNC machining

1、 Cause analysis of workpiece over cutting

1. Deviation or error of workpiece edge seeking

(1) Negligence of site personnel;

(2) The dimensions of the drawing are not clear, and X, y and Z are not marked in the usual way;

(3) The processing origin of program sheet does not coincide with the origin of drawing.

2. Wrong tool use or wrong program list (this error often occurs when the program is copied)

Preventive measures:

(1) Fill in the program sheet while writing the program;

(2) After the program is finished, the tool size must be checked one by one;

(3) Manually add the program number and tool size to the beginning of the program NC code.

3. When rough milling, the allowance is too small or the diameter of tool is not accurate

Preventive measures:

(1) The programmer should have a deep understanding of the cutting performance and material of the tool, and make allowance according to the actual situation;

(2) The tool must be measured accurately before clamping.

4. The cutting tool is not clamped firmly or extended too long, resulting in over cutting

Preventive measures:

(1) The clamping tool should be firm;

(2) The tool elongation generally does not exceed 2 / 3 of the total length of the tool;

(3) Under special circumstances, the tool must be extended (more than 2 / 3). The cutting amount must be reduced accordingly, and the speed and speed must also be reduced;

5. Excessive cutting amount causes broach over cutting

In cutting, the processor should consider the material and hardness of the workpiece, the rigid feed rate of the cutting tool and the machine and the rotation speed.

6. Over cutting caused by wrong adjustment procedure on site

Preventive measures:

(1) The site shall carry out the procedure according to the path specified in the procedure sheet;

(2) The site shall understand the operation sequence and coding principle of program code of the programming class;

Program code = two codes after mold number + workpiece code (two codes) + electrode serial number (if electrode is used) + program number.

7. Program writing error (for example: input error of boundary allowance floor surface)

2、 Causes of Tool Collision

1. NC code writing error;

For example, the zero point of the work piece is at the bottom or the center of the work piece, but not on the top surface of the workpiece. After the program is finished, the post processing program has a fixed height of = 50.0. When the distance between the required point of the workpiece and the top of the height is 50.0, the workpiece may collide with the cutter.

2. Inaccurate tool measurement;

Preventive measures: the tool measurement should be carried out with a more accurate tool as far as possible.

3. Program garbled code (knife collision caused by transmission error);

Program number call error or program has been modified, but still using the old program processing and writing date;

When the program sheet is changed, the principle of replacing the old one with the new one should be adopted to destroy the old drawings and the program list;

The on-site processor should check the detailed data of the program below as much as possible.

4. Wrong tool use or wrong tool writing in program list;

Prevention: add the program number and tool diameter to the program head.

5. The safety plane setting is not high enough, and the tool does not move when it is opened, resulting in knife collision;

For example: In order to save the time of tool lifting, two safety planes (the higher safety plane is greater than the high point of the workpiece, and the lower safety plane is lower than the high point of the workpiece and higher than the part to be processed) in order to save the time for lifting the tool on site. When the tool finishes machining a part, it is raised to the lower safety plane (due to the limitation of software) When preparing to process a part, the middle lifting tool passes over the boss, and the height is lower than the boss, resulting in knife collision.

prevention:

(1) After the program is written, the path of the program should be modeled;

(2) In view of the above question, in order to shorten the on-site processing time, it is necessary to write the processing procedures of each part separately, and then post them together;

(3) The distance between the tool and the workpiece is not enough, so that the tool can be directly inserted into the workpiece;

Prevention and reference standard: the length of tool feed and pull out should be greater than half shank of cutter.

6. The remarks of the procedure are not well considered;

Examples: (1) the height of the workpiece protruding from the vice is not enough;

(2) The swing range of clamping screw is smaller than that of tool path when lifting screw, which results in the tool hitting the surrounding screw;

(3) When the tool is noted, the tool collision will be caused when the elongation remarks are ominous or wrong.

7. Uneven residue;

8. The workpiece material itself has defects or hardness is too high;

The position of clamping block is not considered in the procedure;

10. If the residual material is not uniform enough to cause the tool collision, it is not considered whether the residual material distribution is uniform when compiling the processing program; it is easy to hit the knife when changing the small knife, because once the thick material is cut in a row under the condition of constant feed and rotation speed during processing, the impact force will increase, which will cause the cutter to hit.

Requirements of CNC parts processing

Part material, single piece production. The parts have been machined to size.

Selected equipment: Machining Center

2、 Preparatory work

Finish related preparation work before machining, including process analysis and process route design, tool and fixture selection, programming, etc.

3、 Operation steps and contents

1. Start the machine and manually return each coordinate axis to the origin of the machine tool

2. Tool preparation

According to the processing requirements, select a Φ 20 end mill, a Φ 5 center drill and a Φ 8 twist drill, and then use the spring chuck shank to clamp the Φ 20 end mill. The tool number is set to T01. Use the chuck handle to clamp the Φ 5 center drill and Φ 8 twist drill, and set the tool number to T02 and T03.

3. Put the toolholder with the tool clamped into the tool magazine manually

1) Enter “T01 M06” to execute

2) Manually install the tool T01 onto the spindle

3) Put T02, T03 and T04 into the tool magazine according to the above steps

4. Clean the worktable, install the fixture and workpiece, clean and install the flat jaw vise on the clean workbench, align and level the vise through the dial indicator, and then install the workpiece on the vise.

5. Tool setting, determine and input workpiece coordinate system parameters

1) Use the edge finder to set the cutter, determine the zero offset value of X and Y direction, and set the zero deviation value of X and Y direction

Input to the workpiece coordinate system g54, the zero bias value of Z direction in g54 is 0;

2) the Z axis setter is placed on the upper surface of the workpiece, and the 1 cutter is installed on the upper surface of the workpiece. The spindle is determined by using the tool to determine the zero value of the workpiece coordinate system Z, and the Z to zero offset value is input into the corresponding length compensation code of the machine tool. The “+” and “-” numbers are determined by G43 and G44 in the program. If the length compensation instruction in the program is G43, then the input “-” Z to zero deviation value to the machine tool. Corresponding length compensation code;

3) In the same procedure, input the zero offset value of No.2 and No.3 tools into the corresponding length compensation code of the machine tool.

6. Input processing program

The processing program generated by computer is transferred to the memory of CNC system through data line.

7. Debug processing program

The method of moving the workpiece coordinate system along + Z direction, that is, tool lifting operation, is adopted for debugging.

1) Debug the main program and check whether the 3 tools complete the tool change action according to the process design;

2) Debug three subroutines corresponding to the three tools to check whether the tool action and machining path are correct.

8. Automatic processing

After confirming that the program is correct, restore the Z value of the workpiece coordinate system to the original value, set the fast moving rate switch and cutting feed rate switch to low gear, press the NC start key to run the program and start machining. Pay attention to observe the tool path and the remaining moving distance during machining.

9. Take down the workpiece, carry out the inspection, select the vernier caliper for size detection, and conduct quality analysis after detection.

10. Cleaning the processing site

11. Shut down

Development trend of CNC parts processing

The product quality of CNC parts products, whose products improve the product quality of users, can get customers. For the improvement of processing technology, all walks of life have not stopped. Taking the hard oxidation industry as an example, the early products are all using electroplating oxidation because of its low cost and easy control, which has been recognized by the market. However, with the development of surface treatment technology, this product has been developed In order to seize the market, the product manufacturers use aluminum shell, which makes the material feel better and more beautiful, and can be made into high-quality parts. In the surface treatment method, the advanced hard oxidation treatment is used. The surface has texture and good aesthetics. The important thing is that the hard oxidation strengthens the surface quality of the product, increases the corrosion resistance, and makes the product quality more stable and service life Long life, has been recognized by the market.

In today’s manufacturing industry, there are many products customers need to carry out hard oxidation surface treatment when designing. How to ensure the quality of hard oxidation products in batch production. If the surface treatment of CNC precision parts does not reach the required oxidation thickness, it will not meet the customer’s order requirements. Therefore, it is necessary for the hard oxidation factory to have sufficient technical equipment and experienced technicians, so that the customer products can have higher added value and the whole industry can be developed.

CNC parts processing is an important part of the manufacturing industry. Many machinery and parts with ≡ technology need CNC parts with high precision and hardness. In the processing and production, the surface treatment effect of parts will directly affect the quality of products. Therefore, enterprises should attach great importance to the selection of hard oxidation processing plants.

Process analysis

The NC machining process of the parts to be processed involves a wide range of issues. In this paper, combined with the possibility and convenience of programming, some main contents to be analyzed and reviewed are proposed.

1. Dimension marking should conform to the characteristics of NC machining

In NC programming, all the sizes and positions of points, lines and surfaces are based on the programming origin. Therefore, the coordinate size is directly given on the part drawing, or the dimension is quoted with the same datum as far as possible.

2. The conditions of geometric elements should be complete and accurate

In the process of programming, the programmer must fully master the geometric parameters of the part contour and the relationship between the geometric elements. Because it is necessary to define all geometric elements of the part contour in automatic programming, and to calculate the coordinates of each node in manual programming, no matter which point is unclear or uncertain, programming cannot be carried out. However, due to the part designer’s carelessness or neglect in the design process, the parameters are often incomplete or unclear, such as whether the arc and the straight line, the arc and the arc are tangent or intersecting or separated. Therefore, in the review and analysis of drawings, we must be careful, and timely contact the designer if problems are found.

3. The positioning datum is reliable

In NC machining, the working procedure is often concentrated, so it is very important to locate with the same datum. Therefore, it is often necessary to set some auxiliary datum or add some process boss on the blank.

4. Uniform geometry type or size

The shape and inner cavity of the parts are of uniform geometry type or size, which can reduce the number of tool change, and may also apply control program or special program to shorten the program length. The shape of the parts should be symmetrical as far as possible, so that it is convenient to use the mirror processing function of CNC machine tool to program, so as to save programming time.

How to set the reference point and coordinate of NC lathe in NC machining?

You can see if your bed reference point parameters are set correctly.

Generally, CNC cutting system automatically processes the parts to be processed according to the pre programmed processing program (commonly used drawing software aotocad). According to the instruction code and program format specified by the NC cutting system, a machining program sheet is compiled for the machining process route, process parameters, tool movement path, displacement, cutting parameters (spindle rotation, feed rate, back feed, etc.) and auxiliary functions (tool change, spindle forward rotation, reverse rotation, cutting fluid on and off, etc.), and then record the contents of this program list in the NC cutting system Control medium (such as perforated paper tape, magnetic tape, magnetic disk, magnetic bubble memory), and then input into the numerical control device of the numerical control machine tool, so as to direct the machine tool to process parts.

The whole process from analysis of part drawing to making control medium is called NC programming. The difference between CNC cutting equipment and ordinary hand and semi-automatic cutting equipment in processing parts is that CNC cutting equipment automatically processes parts according to the program, while ordinary hand and semi-automatic cutting equipment needs to be operated by people. We can achieve the purpose of processing different parts as long as we change the program that controls the action of the machine tool. Therefore, CNC cutting equipment is particularly suitable for processing small batch and complex shape parts with high precision requirements!

Because the CNC cutting equipment must process parts according to the program, the programmer will input the program into the CNC system to direct the work of the machine tool. The program input is through the control medium. In this way, the NC system is used to control and complete the processing of parts. The drawing staff can modify the graphics in time, and the accuracy of the parts is greatly improved compared with that of the semi-automatic cutting equipment!

What are the contents of process analysis of part drawing in NC machining?

In the process of NC process analysis, first of all, the process analysis of the part drawing should be carried out to analyze whether the structural process of each part of the part conforms to the characteristics of NC machining

1. The dimension marking of part drawing should conform to the convenience of programming

In the NC machining drawing, it is better to use the same datum to quote the dimension or give the coordinate size directly. This marking method is not only convenient for programming, but also convenient for coordinating the setting and calculation of design datum, process datum, testing datum and programming zero point.

2. The geometric element conditions of the contour structure of parts should be sufficient

In programming, all geometric elements that constitute the contour of the part should be defined. When analyzing the part drawing, it is necessary to analyze whether the conditions of various geometric elements are sufficient. If not, it is impossible to program or model the parts to be processed.

3. Can machining accuracy and dimensional tolerance required by parts be guaranteed

Although the machining accuracy of CNC machine tools is very high, for some special cases, such as the processing of thin-walled parts, due to the poor rigidity of thin-walled parts, the cutting force generated during machining and the elastic yielding of thin-walled parts are easy to produce vibration of the cutting surface, which makes the dimensional tolerance of thin-walled thickness difficult to guarantee, and its surface roughness also increases When its thickness is less than 3 mm, we should pay attention to this problem in technology.

4. Are the geometric types and dimensions of the internal and external contour of the part unified

In NC programming, if the geometric types of the inner contour and outer contour of the part are the same or similar, consider whether it can be programmed in the same program to reduce the tool specification and tool change times as far as possible, so as to reduce the auxiliary time and improve the machining efficiency. It should be noted that the diameter of the tool is often limited by the radius r of the inner contour arc.

5. Can larger diameter tools be used in the process structure design of parts

Using larger diameter milling cutter to process can reduce the number of tool passes and improve the tool rigid system. Not only the machining efficiency is improved, but also the processing quality of the surface and bottom surface of the workpiece is also improved.

6. The fillet radius of the groove bottom or the fillet radius r at the intersection of the base plate and the edge plate should not be too large

Because the large diameter of the cutter contacting with the milling plane D = d-2r, where D is the diameter of the milling cutter. When D is constant, the larger the fillet radius R (as shown in Fig. (1), the worse the ability of milling cutter end edge to mill plane, the lower the efficiency and the worse the manufacturability.. When R reaches a certain degree, it must be processed with ball end milling cutter, which should be avoided. When D is larger and R is smaller, the area of milling surface is larger, the ability of machining plane is stronger, and the milling technology is better. Sometimes, when the bottom surface area of milling is large and the bottom arc R is also large, two milling cutters with different R can be used to cut twice.

7. Principle of ensuring the unification of standards

If the parts are re installed on the other side after milling one side, due to the non-uniform datum, it is often difficult to connect the cutter due to the re installation of the parts, and the contour position and size on the positive and negative sides are not coordinated after machining. Therefore, it is necessary to make full use of the appropriate hole of the part itself or the reference edge of the part contour or specially set the process hole (such as adding process boss on the blank or setting the reference hole on the allowance to be removed in the subsequent process) as the positioning reference, so as to ensure the accuracy of the relative position after two clamping processes.

8. Consider the deformation of parts

When the parts are deformed in the process of NC milling, not only the machining quality of the parts is affected, but also the phenomenon of skipping cutter sometimes occurs. At this time, we should consider the milling process, separate the rough and finish machining as far as possible, or use the symmetrical method to remove the allowance. Of course, heat treatment can also be used to solve the problem.