The hottest inventory of CNC machining knowledge t

2022-08-09
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Check the NC machining knowledge that people in the machine tool industry have to know.

for the current economic NC lathes in China, the ordinary three-phase asynchronous motor is generally used to realize stepless speed change through the frequency converter. If there is no mechanical deceleration, the spindle output torque is often insufficient at low speed. If the cutting load is too large, it is easy to be stuffy, but some machine tools have gear positions, which solves this problem very well

you must know the following NC machining knowledge

1. Influence on cutting temperature: cutting speed, feed rate, back feed

influence on cutting force: back feed, feed rate, cutting speed

influence on tool durability: cutting speed, feed rate, back feed

2. When the back cutting amount is doubled, the cutting force is doubled

when the feed rate is doubled, the cutting force increases by about 70%

when the cutting speed is doubled, the cutting force gradually decreases

in other words, if G99 is used, the cutting speed will increase and the cutting force will not change much

3. Whether the cutting force and cutting temperature are within the normal range can be judged according to the discharge of iron chips

4. When the sum of the measured actual value x and the drawing diameter y is greater than 0.8, the turning tool with a secondary deflection angle of 52 degrees (that is, the turning tool with a main deflection angle of 93 degrees, which is our commonly used blade of 35 degrees) may wipe the tool at the starting point

5. Temperature represented by the color of iron filings:

all staff Participate in quality management throughout the process

white less than 200 degrees

yellow degree

dark blue 290 degrees

blue degree

purple black greater than 500 degrees

red greater than 800 degrees

nacoimtc general default G instruction:

g69: not very clear

g21: metric size input

g25: spindle speed fluctuation detection disconnected

g80: fixed cycle cancellation

g54: coordinate system default

g18: ZX plane selection

g96 (g97) Many things are saved for some enterprises: constant linear speed control

g99: feed per revolution

g40: tool tip compensation cancellation (g41g42)

g22: storage stroke detection on

g67: macro program mode call cancellation

g64: not very clear

g13.1: polar interpolation mode cancellation

7 The external thread is generally 1.3p, and the internal thread is 1.08p

8. Thread speed s1200/pitch * safety factor (generally 0.8)

9. Manual tip r compensation formula: chamfer from bottom to top: z=r* (1-tan (a/2)) x=r (1-tan (a/2)) *tan (a) chamfer from top to bottom can be changed from minus to plus

10. When the feed increases by 0.05, the rotation speed decreases. This is because reducing the rotation speed means that the tool wear decreases, and the increase of cutting force is relatively slow, so as to make up for the impact caused by the increase of cutting force and temperature due to the increase of feed

11. Cutting speed and cutting force are very important to the influence of cutting tools. Excessive cutting force is the main reason for tool collapse. The relationship between cutting speed and cutting force: the faster the cutting speed is, the feed does not change, and the cutting force decreases slowly. At the same time, the faster the cutting speed is, the faster the tool will wear, the greater the cutting force will be, and the higher the temperature will be. When the cutting force and internal stress are too large for the blade to bear, the tool will collapse (of course, there are also reasons such as the decrease of stress and hardness caused by the change of temperature)

12. When machining CNC lathes, the following points should be paid special attention:

(1) for the current economic CNC lathes in China, ordinary three-phase asynchronous motors are generally used to realize stepless speed change through frequency converters. If there is no mechanical deceleration, the spindle output torque is often insufficient at low speed. If the cutting load is too large, it is easy to be stuffy, but some machine tools have gear positions, which solves this problem very well

(2) try to make the tool complete the processing of a part or a work shift as much as possible, especially for the finishing of large parts, pay attention to avoid changing the tool in the middle to ensure that the tool can be processed at one time

(3) when turning thread with CNC lathe, adopt higher speed as much as possible to achieve high-quality and efficient production

(4) use G96 as much as possible

(5) the basic concept of high-speed machining is to make the feed exceed the heat conduction speed, so as to discharge the cutting heat with the iron filings, so as to isolate the cutting heat from the workpiece since peek was developed by ICI company in 1978, so as to ensure that the workpiece does not or does not heat up. Therefore, high-speed machining is to select a very high cutting speed to match the high feed, and select a small back cutting amount at the same time

(6) pay attention to the compensation of tool tip R

13. Vibration and tool collapse often occur when turning grooves. All the fundamental reasons are that the cutting force becomes larger and the rigidity of the tool is not enough. The shorter the extension length of the tool, the smaller the rear angle, and the larger the area of the blade, the better the rigidity. With the larger the width of the groove knife, the cutting force it can bear will increase correspondingly, but its cutting force will also increase. On the contrary, the smaller the groove knife, the smaller the force it can bear, But its cutting force is also small

14. Causes of vibration during grooving:

(1) the extension length of the tool is too long, which reduces the rigidity

(2) if the feed rate is too slow, the unit cutting force will increase, resulting in large amplitude vibration. The formula is: p=f/back cutting amount *fp is the unit cutting force, f is the cutting force, and in addition, if the rotation speed is too fast, the tool will vibrate

(3) the machine tool is not rigid enough, that is, the tool can bear the cutting force, but the machine tool can't. In short, the machine tool doesn't move. Generally, new beds won't have such problems. The beds with such problems are either old or often encounter machine tool killers

15. When turning a cargo, I found that the size was OK at the beginning, but after doing it for a few hours, I found that the size changed and the size was unstable. The reason may be that at the beginning, because the knives were new, the cutting force was not very large, but after turning for a period of time, the tool was worn and the cutting force became larger, causing the workpiece to shift on the chuck, so the size kept running and unstable

16. When using G71, the values of P and Q cannot exceed the sequence number of the whole program, otherwise an alarm will appear: the format of g71-g73 instruction is incorrect, at least in fuanc

17. There are two formats of subroutines in FANUC System:

(1) the first three digits of P refer to the number of cycles, and the last four digits are the program number

(2) the first four digits of p0000l000 are the program number, and the last three digits of L are the number of cycles

18. If the starting point of the arc remains unchanged and the Z direction of the end point is offset by a mm, the position of the bottom diameter of the arc is offset by a/2

19. When drilling deep holes, the drill does not grind the cutting groove to facilitate the chip removal of the drill

20. If the tool is used to drill holes with a tool holder, the drill bit can be rotated and the hole diameter can be changed

21. When drilling stainless steel center holes or stainless steel holes, the drill bit arranges more than 3000 laid-off employees for internal reemployment or the center drill center must be small, otherwise it cannot be drilled. When drilling with cobalt drill, do not grind the groove to prevent the drill bit from annealing during drilling

22. According to the process, there are generally three kinds of blanking: one blanking, two goods blanking, and the whole bar blanking

23. When turning the thread, the ellipse may be due to the looseness of the material. Just use a tooth cutter to straighten a few more knives

24. In some systems that can input macro programs, the subroutine cycle can be replaced by macro program filling, which can save the program number and avoid a lot of trouble

25. If you use a drill to enlarge the hole, but the hole has a large jump, you can use a flat bottom drill to enlarge the hole, but the fried dough twist drill must be short to increase the rigidity

26. If the drill is directly used on the drilling machine, the hole diameter can deviate, but if the hole is enlarged on the drilling machine, the size generally will not run. For example, if the drill is enlarged on the drilling machine with a 10mm drill, the expanded hole diameter is generally about 3 wire tolerance

27. When turning the small hole (through hole), try to make the chips roll continuously and then discharge from the tail. The key points of chip rolling are as follows: first, the position of the knife should be properly raised; second, the appropriate blade angle, cutting rate and feed rate should be kept in mind that the knife should not be too low, otherwise it is easy to break the chips. If the auxiliary deflection angle of the knife is large, even if the chips are broken, it will not jam the tool bar. If the auxiliary deflection angle is too small, the chips will jam the tool bar after chip breaking, which is easy to cause danger

28. The larger the cross-section of the knife bar in the hole, the less likely it is to vibrate the knife. In addition, a strong rubber band can be tied to the knife bar, because the strong rubber band can play a certain role in absorbing vibration

29. When turning the copper hole, the tip r of the knife can be appropriately large (r0.4-r0.8), especially when turning the taper under the car, the iron parts may be nothing, and the copper parts will too laggy

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