Knowledge about CNC machining

1. Influence on cutting temperature: cutting speed, feed rate, backing amount

Effect on cutting force: back-feeding amount, feed rate, cutting speed

Impact on tool durability: cutting speed, feed rate, back-feeding

2. When the amount of back-feeding knife is doubled, the cutting force is doubled.

When the feed rate is doubled, the cutting force is increased by about 70%.

When the cutting speed is doubled, the cutting force is gradually reduced

In other words, if the cutting speed is increased with G99, the cutting force will not change much.

3. The cutting force can be judged according to the condition of iron filings, and the cutting temperature is within the normal range.

4. When the actual value X of the quantity and the diameter Y of the drawing are greater than 0.8, the concave arc of the car, the turning tool with the auxiliary declination of 52 degrees (that is, the commonly used blade is a blade with a main angle of 93 degrees of 35 degrees) The R that is out of the car may be wiped at the starting point.

5, the temperature represented by iron filings: white is less than 200 degrees

Yellow 220-240 degrees

Dark blue 290 degrees

Blue 320-350 degrees

Purple black is greater than 500 degrees

Red is greater than 800 degrees

6, FUNAC OI mtc general default G command:

G69: Not very clear

G21: Metric size input

G25: Spindle speed fluctuation detection disconnected

G80: Canned cycle cancellation

G54: coordinate system default

G18: ZX plane selection

G96 (G97): constant line speed control

G99: Feed per revolution

G40: Tool nose compensation cancel (G41 G42)

G22: Storage stroke detection is turned on

G67: Macro program modal call canceled

G64: Not very clear

G13.1: Polar coordinate interpolation method canceled

7, the external thread is generally 1.3P, the internal thread is 1.08P

8, thread speed S1200 / pitch * safety factor (usually 0.8)

9. Manual tool nose R compensation formula: chamfer from bottom to top: Z=R*(1-tan(a/2)) X=R(1-tan(a/2))*tan(a) From The chamfer up and down will be reduced to plus

10. For every 0.05 increase in feed, the rotation speed is reduced by 50-80 revolutions. This is because lowering the rotation speed means that the tool wear is reduced, and the cutting force is increased more slowly, thereby making up for the increase of the cutting force and the temperature increase due to the increase of the feed. Impact

11. The cutting speed and the influence of cutting force on the tool are the main reasons, and the cutting force is too large to cause the tool to collapse. The relationship between cutting speed and cutting force: the faster the cutting speed, the constant the cutting force, the slower the cutting force, and the faster the cutting speed, the faster the tool wears, the larger the cutting force, the more the temperature will come. The higher the cutting force and internal stress are, the landslide knives (of course, there are also changes in the stress and hardness caused by temperature changes).

12. When processing CNC machines, the following points should be paid special attention:

(1) For the current economic CNC 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. Stuffy car, but some gears with gears on the machine solve this problem very well.

(2) As far as possible, the tool can complete the machining of one part or one work shift. In the case of large-piece finishing, pay special attention to avoiding the middle of the tool change to ensure that the tool can be processed once.

(3) When using CNC machine to turn the thread, use high speed as much as possible to achieve high quality and efficient production.

(4), use G96 whenever possible

(5) The basic concept of high-speed machining is to make the feed exceed the heat transfer speed, so that the cutting heat is discharged along with the iron scraps to isolate the cutting heat from the workpiece, ensuring that the workpiece does not heat up or heat up. Therefore, high-speed machining is very high. The cutting speed is matched with the high feed and the smaller back knife is selected.

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

13, workpiece material cutting processability classification table (small P79)

Common thread cutting times and backing knife scale (large P587)

Common geometry calculation formula (large P42)

Inch and millimeter conversion table (large P27)

14. Vibration and chipping are often generated in the trough. All the root causes are the cutting force and the rigidity of the tool. The shorter the tool extension length, the smaller the back angle, and the larger the blade area, the better the rigidity. The cutting force can be increased with the larger cutting force, but the cutting force of the groove cutter can be increased correspondingly, but its cutting force will also increase. On the contrary, the small groove cutter can withstand less force, but Its cutting force is also small

15. Reasons for vibration during the trough:

(1), the tool extension length is too long, and the rigidity is lowered.

(2), the feed rate is too slow, and the unit cutting force becomes large, causing a large vibration. The formula is: P=F/back knife amount *f P is the unit cutting force F is the cutting force, and the rotation speed is too Will also vibrate the knife

(3), the rigidity of the machine tool is not enough, that is to say, the tool can bear the cutting force, and the machine can’t bear it. To put it bluntly, the machine tool does not move. Generally, the new bed will not have such problems. The bed with such problems is either old. Or often encounter machine killers

16. When I was in a car, I found the size at the beginning, but after a few hours, I found that the size has changed and the size is unstable. It may be because the knife is new at the beginning, so the cutting force is It is not very big, but after a period of time, the tool wears and the cutting force becomes large, causing the workpiece to shift on the chuck, so the size is old and unstable.

17. When using G71, the values ​​of P and Q cannot exceed the sequence number of the whole program. Otherwise, an alarm will occur: the G71-G73 instruction format is incorrect, at least in FUANC.

18. Subroutines in the FANUC system come in two formats:

(1) The first three digits of P000 0000 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 three digits after L are the number of loops.

19. The starting point of the arc is unchanged, and the end Z direction is offset by a mm, then the arc bottom diameter is offset by a/2.

20. When the deep hole is drilled, the drill does not grind the cutting groove to facilitate the drill bit removal.

21. If you are using a tool holder for the tooling, you can turn the drill bit to change the aperture.

22. When hitting the stainless steel center eye or the stainless steel eye, the drill bit or center drill center must be small, otherwise it can’t be moved. When using the cobalt drill, do not grind the groove to avoid the bit annealing during the drilling process.

23. According to the process, there are generally three kinds of materials: one material, two goods, the whole bar.

24. When the ellipse appears in the thread of the thread, it may be loose, and it will be fine with a knife.

25. In some systems where macro programs can be input, macro program charging can be used instead of subroutine loop, which saves the program number and avoids a lot of trouble.

26. If the drill hole is used for reaming, but the hole jumps very much, the flat hole drill can be used for reaming, but the twist drill must be short to increase the rigidity.

27. If the drill hole is directly drilled with a drill bit, the hole diameter may be deviated, but if the drill hole is not expanded in the size of the drill hole, for example, using a 10MM drill bit to ream the drill bed, the enlarged aperture is generally Around 3 wire tolerances

28. In the small hole (through hole) of the car, try to make the scraps continuously and then discharge from the tail. The main points of the scrap are: First, the position of the knife should be properly raised. Second, the appropriate blade inclination angle, the amount of knife And the feed rate, remember that the knife can not be too low or it is easy to break the chip. If the secondary declination of the knife is large, the cutter bar will not be stuck even if the chip breaking is broken. If the secondary declination is too small, the chip will catch the knife after the chip breaking. Rod is easy to be dangerous

29. The larger the cross section of the arbor in the hole, the less likely it is to vibrate the knives. It is also possible to attach a strong rubber band to the arbor, because the strong rubber band can play a certain role of absorbing vibration.

30. When the copper hole of the car, the tip R of the knife can be appropriately large (R0.4-R0.8), especially when the car is taper, the iron piece may be nothing, the copper piece will be very chipped.

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