Dongguan CNC machining experience sharing

A PTJ company that has been engaged in CNC machining services in China for many years has accumulated some experience, and I will share it with you today.

  1. The speed of the white steel knife should not be too fast.
  2. For coppersmiths, use white steel knives less frequently, and more use flying knives or alloy knives.
  3. When the workpiece is too high, you should use different length cutters to roughen it in layers.
  4. After roughing with a big knife, use a small knife to remove the remaining material to ensure that the remaining amount is consistent.
  5. Flat-bottomed knives are used to process planes, and ball knives are used less to reduce processing time.
  6. When the copper worker cleans the corner, first check the size of the R on the corner, and then determine the size of the ball knife to use.
  7. The four corners of the calibration plane should be flat.
  8. Where the inclination is an integer, use an inclination knife to process, such as pipe position.
  9. Before doing each process, think clearly about the margin left after the previous process is processed, so as to avoid empty cutters or excessive processing.
  10. Try to take simple toolpaths, such as shape, grooving, one-sided, and avoid the surrounding height.
  11. When walking WCUT, if you can go FINISH, don’t go ROUGH.
  12. When the shape of the light knife is rough, polish it first, then polish it. When the workpiece is too high, polish the edge first, then polish the bottom.
  13. Set tolerances reasonably to balance processing accuracy and computer calculation time. When roughing, the tolerance is set to 1/5 of the margin, and for light knife, the tolerance is set to 0.01.
  14. Do more procedures to reduce the time of empty knife. Do a little more thinking to reduce the chance of error. Do a little more auxiliary line auxiliary surface to improve the processing condition.
  15. Establish a sense of responsibility and carefully check each parameter to avoid rework.
  16. Diligent in learning, good at thinking, and continuous improvement of CNC machining in Dongguan. For non-planar milling, use more ball cutters, less end cutters, and don’t be afraid of receiving the cutter; small cutters clean the corners and large cutters for fine-tuning; don’t be afraid to make up the surface, the appropriate surface can increase the processing speed and beautify the processing effect.
  17. The rough material has high hardness: Up-milling is better. Blank material hardness is low: down-milling is better. Machine tool has good accuracy and rigidity. Finishing: It is more suitable for down-milling, and vice versa. Down-milling is strongly recommended for finishing of inner corners of parts. Rough machining: up-milling is better, finishing: down milling is better. Tool material has good toughness and low hardness: more suitable for rough machining (large cutting amount processing). Tool material has poor toughness and high hardness: more suitable for finishing (small cutting amount processing) ).
  18. Copper processing methods and matters needing attention: Before writing the tool path, after finishing the three-dimensional picture, move the center of the graphic to the origin of the coordinate, and move the highest point to Z=0, then it can be processed, and the copper male spark position can be processed with negative reserve. Before processing, check whether the clamping direction of the workpiece is the same as the direction of the graphics in the computer, whether the alignment in the mold is correct, whether the fixture is blocking the processing, and whether the directions of the front and rear molds match. Also check whether the tools you use are complete, the benchmarks in the calibration table and so on. Matters needing attention when processing copper: For determining the spark level, the general reserved amount for young males (that is, fine males) is 0.05~0.15, and coarse males are 0.2~0.5. The specific spark level can be determined by the master of the mold. Are there any dead corners that cannot be processed by the copper public? Do you need to dismantle one more scattered public? The tool path for processing copper is generally: broad knife (flat knife) to open rough-small knife (flat knife) to clear the corner � smooth knife with a ball knife to smooth the surface. Generally, teachers use a flat knife instead of a ball knife. After the big knife, use a small knife to make the roughness, and then use a large ball knife to smooth the surface, and then use a small ball knife to smooth the surface. Using a knife to process the dead corners that the big knife can’t pass can limit the range of the knife, so as not to broadcast too many empty knives. Copper males, especially young males, have relatively high accuracy requirements. The tolerance is generally 0.005~0.02, and the step distance is 0.05~0.3. When the copper is exposed to the thickness, leave the over-cut position of the ball tool position, that is, make the copper male profile thick and deep by one knife radius. Tonggong also needs to process the median and calibrate the benchmarks, and calibrate the coppers during spark discharge. Generally, the coppers processed by the three sides (up, down, left, and right) must have three reference planes. Copper is a material that is relatively easy to process. The cutting 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, and the knife can be moved faster when roughing. ,Improve efficiency. Note: The parameters in the brackets are the parameters when the high-speed steel knife is roughing the steel. The above cutting speed refers to the roughing, the required shape F=300~500, and the steel smooth knife F is 50~200.
  19. The problem of rough opening of the front mold: First, rotate the copper figure in the front view or the side view by 180o to turn it into the front mold picture. Of course, add the pillow position and the PL surface; where the original body needs to be left in the front mold, do not use the mirror body method to remove the copper. The work drawing becomes the front mold drawing, sometimes wrong (when the copper drawing is asymmetric in the X direction and the Y direction). There are two difficulties in the processing of the front mold: the material is relatively hard; the front mold cannot be easily welded and cannot be mistaken. The principle of using a knife when the front mold is rough is similar to that of a copper worker. The big knife is rough → the small knife is rough → the big knife is light knife → the small knife is light knife, but the front mold should use a big knife as much as possible. Use the knife handle () to make rough, and try to use a round nose knife when smoothing. Because this kind of knife is big enough, powerful, and the parting surface of the front mold is processed, there is usually a problem. The piercing machine should be accurate, and the cavity should have a machining allowance of 0.2~0.5 (leave it out for sparks). This is to correct the surface of the mold cavity by 0.2~0.5 in the positive direction, and set the machining allowance to 0 when writing the tool path. The cutting range is usually limited when the front mold is roughed or smoothed. Remember that the range you set is the range of the tool center, not the range of the tool boundary, not the range that the tool can process, but a larger tool radius. The commonly used tool path method for front mold roughing is curved surface grooving and parallel light knife. When the front mold is processed, the parting surface and the pillow surface are generally processed to the correct number, while the collision surface can be left with a margin of 0.1 to prepare the mold.
  20. Problems often encountered in molds after processing: There are two types of back molds: the original type or the inlay type. The back mold is made of steel like the front mold, and the material is harder. It should be processed with a tool holder as much as possible. The common tool path is curved surface grooving, parallel milling cutters, and the principle of tool selection is Large knife open coarse → small knife open coarse → large knife light knife → small knife light knife. The post-mold picture is usually made by reducing the material level of the copper drawing and adding the PL surface, pillow position, and the original body. If the material level is relatively uniform, you can directly leave the negative material level in the processing information, but PL (Parting surface), the pillow position and the contact surface cannot shrink the material position. At this time, you can first correct these faces by a material level or draw the subject. A problem often encountered by the original division is that the ball knife cannot clear the sharp corners. At this time, you can use a flat knife to go to the steep slope of the curved surface to process the clear corners. For example, the back mold is divided into a hidden frame and a core. Please pay attention to the empty knife several times, otherwise the frame will have a slope, the upper edge is accurate, the lower edge is small, it is difficult to match the mold, especially the deeper frame, we must pay attention to this problem, and the knife of the light frame should be new. Okay, and choose a larger knife. If the core is too high, you can turn it over and process the frame first, and then assemble it into the frame, and then process the shape. Sometimes there is a branch. Be careful not to overcut the shape with a ball knife. Be sure to protect the support step. In order to facilitate the matching mode, the frame size can be smaller than the external size of Koxin-0.02/s. The tolerance and step distance of Koxin light knife can be slightly larger, and the tolerance is 0.01~0.03, and the feed is 0.2~0.5.
  21. Problems in bulk copper processing: Sometimes it is difficult to process the overall copper male, there are dead corners that cannot be processed, or it is not easy to process, and the required tool is too long or too small, you can consider adding one more copper male, and sometimes it is necessary to clean the corners of the copper male. It is not difficult to process the public, but it is necessary to figure out the deviation of the real good spark, and the calibration standard.
  22. Processing of thin plate position copper male: This kind of copper is easy to change during processing. When processing, use a new knife, the knife should be small, and the knife should not be too large. When processing, the length a can be adjusted first, but d should be left with a large margin (such as 1.0 mm) Walk on two sides again, each time the depth is h=0.2~1, don’t go too much in depth, and don’t go around the knife in a circle, but divide it into two sides and walk separately.
  23. The direction of left and right pieces and one out of two: Sometimes a set of molds will produce two parts. For the left and right parts, the graphics can be made by mirroring. If there are two identical parts, the graphics must be flat or rotated in XY, and they must not be mirrored. Be careful not to reverse the direction.
  24. The direction of Dongguan CNC machining mold: The four guide bolt holes of the mold blank are not completely symmetrical. One of them is asymmetrical. Therefore, when processing the front and rear molds, it is clear that there are benchmarks on each template. The front and rear molds must be combined with the benchmarks. , Particular attention must be paid to the mold forming the original mold blank. Pay attention to the direction when drawing the picture. The direction of the Tong Gong is the same as that of the front view (top view), the direction of the core and the Zangke frame are the same as that of the Tong Gong, and the front mold is the opposite. Some decorative lines such as grooves or bosses on the curved surface are not easy to process because they are relatively narrow. For the groove, we generally avoid the groove, that is, mill it deeper, and then add a loose male to make a countersunk surface. Generally, the boss can only be made a loose male separately, and a large copper male does not, so as to ensure the quality.
  25. Tolerance of mold and product fit: A set of products usually has several or more than a dozen parts. The main matching dimensions of these parts are guaranteed by computer gong processing. It is important to choose a reasonable tolerance, especially for some product design drawings that do not consider the matching problem. The matching of the bottom and the surface shell is undoubtedly a 0 to 0 fit, and the positioning is guaranteed by the branch. The tolerance of the concave branch and the convex branch is generally 0.1mm, unilateral. Accessories on the big body, such as transparent mirrors, generally have a smaller shape than the size of the big body by 0.1~0.2 on one side. For movable accessories on the big body, such as buttons, the shape of the accessories is 0.1~0.5 smaller than that on the big body. The surface shape of the accessories on the body should generally be the same as the surface shape of the body, which can be removed from the surface of the body.
  26. Draft angle (draft angle): Plastic molds must have a mold inclination, otherwise it will be scratched. If the drawing is not marked, you can discuss with the mold master. The mold inclination is generally 0.5 to 3 degrees. If the mold is etched, the mold exit angle should be larger. , 2~5 degrees, depending on the thickness of the etching pattern.
  27. The knife problem: In many cases, when the tortoise cutter is just milling, the amount of tool eaten is relatively large, which is likely to cause the tool to break or snap the knife. At this time, you can first open the lower tool position or lift the cutter to move away, or cut the cutter outside the material during the day. Give full consideration to this issue. Knife grabbing, flicking, and dropping When the processing volume is relatively large, the tool holder is too long, and the tool is too small. This often happens. The processing volume is relatively large, especially when the concentration of cutting is high, it is easy to happen. For example, the light side depth H=50mm diameter 3/4 cutting, we can divide the 25mm secondary processing, and it is not easy to happen. The tool clamp is too long. The length of the tool is very important for processing. It should be as short as possible. It is easy for beginners to ignore this problem. The clamping length of the tool must be marked on the program paper. It is easy to grab a knife when turning a corner. The solution is to clear the corner layer by layer with a smaller knife, and then change the side of a larger knife. Like the semi-circular groove with diameter 8 as shown in the figure, if it is directly processed with R4 knife, it is easy to grab the knife at the position of the knife. The solution is (1) use R3 to scan the tool path (2) first use R3 to make rough, and finally Use the R4 knife to clean the corner light knife.
  28. Sharpen a knife: The different shapes of computer gongs often need to be sharpened. Various shaped knives are worn and need to be sharpened. Only the following accounts can be used to grind a usable knife1. The four corners of the tool should be the same height2. Point A is 3 tools higher than point D. The forward (face) is higher than the back, that is, there is a certain clearance angle.
  29. Overcut inspection: Overcutting is a problem that often occurs in masterCAM, so be careful. Over-cutting may occur in multi-curved surface roughening, light knife, tool path trimming, shape, grooving, even if the parameter settings of the chest and the three-dimensional diagram are correct, it may happen. Some of the errors are the software itself. The main inspection method is Simulate the tool path again and check repeatedly in the top view and the side view. The tool path that has not been checked is not allowed to be used on the machine. When contour milling, improper selection of the position of the cutting tool will result in overcutting, which can be avoided by changing the position of the cutting tool.
  30. Milling direction: Computer gongs are generally down milling, unlike milling machine up-milling. The reason is that computer gongs have better rigidity and are not easy to let the cutter. The backlash is small, and the milling shape or inner groove is left-compensated. When machining a symmetrical shape, the tool path of the contour cannot be mirrored, otherwise the machining effect of the mirrored side will not be good. The writing method of the program paper In order to communicate with the personnel operating the machine tool, the program paper should include 1) program name 2 tool size and length 3 machining tool path method 4 machining allowance 5 rough or light knife 6 drawing file name 18. Graphic management computer drawing application For proper file management, it is best to create a catalog for each product, and give a different name to each part. For example, the name of the copper image is A10, the back image can be A10C, the front image is A10CAV, and the scattered copper image is A10S1. , So it’s clearer. 19. Format conversion between different software: Communicate with AutoCAD, DWG files can be read directly for MastCAM 7 and above, and DXF format can be converted into DXF in autocad for versions lower than 7. Other CAM software such as (cimtron, pro/e, UG) can be converted to IGS format first.

31.DNC usage:

After the program is completed, after inspection, there is no problem and it can be copied to the DNC computer for actual processing. There are two ways to copy the program: 1 copying with a disk, 2 sending it through the local area network. Then start the DNC software, find the program you want to run, and press ENTER.

  1. Coordinate system: There are three types: mechanical coordinate system, processing coordinate system, and temporary coordinate system. In the mechanical coordinate system, the mechanical zero point is a reference point on the machine. After each power-on, the origin is determined after returning to zero. The position of the mechanical zero point is determined by the machine factory and should not be changed. The machining coordinate system is used for workpiece processing. It is a sub-coordinate system of the mechanical coordinate system. A point in the mechanical coordinate system (usually the center point of the workpiece) is taken as the coordinate origin, and the mechanical coordinate value of this point is recorded as the processing The origin of the coordinate series can be set as the machining coordinate system. Temporary coordinate system: reset each point as the coordinate origin at any time. Corresponding to the coordinate value, there are also three kinds of coordinate values: machine coordinate value, processing coordinate value, temporary coordinate value (also called relative coordinate value)
  2. Commonly used filter values: The commonly used filter value is 0.001~0.02, and the filter radius R=0.1~0.5. Use a large value for the rough toolpath, a small value for a smooth surface toolpath, a large value for a smaller surface radius, and a smaller value for a larger surface radius. Filtering can effectively reduce the program capacity and make the tool pass more smoothly, but if it is too large, it will affect the machining accuracy.

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