CNC machining experience sharing (Part 1)

A number of years engaged in CNC processing experience, today to share with you.

The speed of white steel knife should not be too fast.
Copper roughing less white steel knife, more use flying knife or alloy knife.
When the workpiece is too high, it should be sliced with different length of knife.
After roughening with a big knife, use a small knife to remove the remaining material to ensure that the allowance is consistent.
The plane should be processed with flat bottom cutter and less ball cutter to reduce the processing time.
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.
The four corners of the calibration plane should be smooth.
If the slope is an integer, use the slope cutter to process, such as pipe position.
Before each process, think about the remaining allowance after the previous process, so as to avoid empty tool or excessive machining
Try to take simple cutting path, such as shape, grooving, single side, less walking around the same height.
When taking wcut, if you can walk finish, don’t go rough.
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.
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.
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.
Establish a sense of responsibility and check each parameter carefully to avoid rework.
For CNC processing, diligent in learning, good at thinking, 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.
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).

Copper processing method

Before writing the cutter path, after the three-dimensional drawing is finished, the graphic center should be moved to the coordinate origin, and the highest 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.

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. Front die opening is commonly used