29 Pieces Of Mechanical CNC Machining Knowledge

1. In CNC machining, the following points should be paid special attention:

(1) In China’s current economic CNC lathes, ordinary three-phase asynchronous motors achieve step-less speed change through inverters. If there is no mechanical deceleration, the output torque of the spindle is often insufficient at low speeds. If the cutting load is too large, it is easy to get stuffy. Car, but some machine tools have gears to solve this problem;

(2) As far as possible, the tool can complete the processing of a part or a work shift. For large-scale finishing, focus on avoiding tool changes in the middle to ensure the tool can be completed in one operation.

(3) When using NC turning to turn threads, use as high a speed 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 conduction speed so that the cutting heat is discharged with the iron chips to isolate the cutting heat from the workpiece and ensure that the workpiece does not heat up or less. Therefore, high-speed machining is selected at a high The cutting speed is matched with the high feed while selecting a smaller back feed amount;

(6) Pay attention to the compensation of the tool nose R.

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

When the feed rate doubles, the cutting force increases by about 70%;

When the cutting speed doubles, the cutting force gradually decreases;

In other words, if G99 is used, the cutting speed becomes more extensive, and the cutting force will not change much.

3. The cutting force and temperature can be judged according to the discharge of iron filings.

4. When the actual value of the measured value X and the diameter Y of the drawing is more significant than 0.8, the turning tool with a secondary deflection angle of 52 degrees (that is, a turning tool with a blade of 35 degrees and a central deflection angle of 93 degrees) ) The R from the car may wipe the knife at the starting position.

5. The temperature represented by the color of iron filings:

White is less than 200 degrees

220-240 degrees yellow

Dark blue 290 degrees

Blue 320-350 degrees

Purple-black is more significant than 500 degrees

Red is more significant than 800 degrees

6. FUNAC OI mtc generally default G instruction:

G69: Not quite sure

G21: Metric size input

G25: Spindle speed fluctuation detection is off

G80: Canned cycle canceled

G54: default coordinate system

G18: ZX plane selection

G96 (G97): Constant linear speed control

G99: Feed per revolution

G40: Tool nose compensation canceled (G41 G42)

G22: Stored stroke detection is on

G67: Macro program modal call canceled

G64: Not quite sure

G13.1: Cancel polar coordinate interpolation mode

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 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 chamfers from the top to the bottom of the car will be reduced to plus.

10. For every 0.05 increase in feed, the rotation speed is reduced by 50-80 rpm. This is because lowering the rotation speed means that the tool wear is reduced, and the cutting force increases more slowly, compensating for the increase in cutting force and temperature due to the rise in feed—the impact.

11. The influence of cutting speed and force on the tool is significant.

The main reason for cutting the tool is that the cutting force is too high. The relationship between cutting speed and cutting force: The faster the cutting speed, the quicker the feed does not change, and the cutting force decreases slowly. At the same time, the faster the cutting speed, the faster the tool will wear, the cutting force will increase, and the temperature will increase. The higher, when the cutting force and internal stress are too large for the insert to withstand, there will be a landslide (of course, there are also stress and hardness reduction caused by temperature changes).

12. Influence on cutting temperature: cutting speed, feed rate, back cutting amount;

Effect on cutting force: back cutting amount, feed rate, cutting speed;

Impact on tool durability: cutting speed, feed rate, backed amount.

13. Vibration and chipping often occur in the slot.

All the root causes are that the cutting force becomes more extensive and the tool is not rigid enough. The shorter the tool extension length, the smaller the back angle, and the larger the blade area, the better the rigidity. It can follow the more significant cutting force, but the more critical the width of the slotted cutter, the larger the cutting force it can withstand, but its cutting force also increases. On the contrary, the smaller the slotted cutter, the smaller the force it can withstand. Its cutting force is also small.

14. Reasons for vibration in the car slot:

(1) The extended length of the cutter is too long, which reduces the rigidity;

(2) The feed rate is too slow, which will cause the unit cutting force to increase and cause significant vibrations. The formula is: P = F / back feed amount * f P is the unit cutting force, F is the cutting force, and the speed is too fast.t Will also shake the knife;

(3) The machine tool is not rigid enough; the tool can bear the cutting force, but the machine tool cannot. To put it plainly, the machine tool does not move. Generally, new beds do not have such problems. The bed with such issues is either old or old. Either the machine killer is often encountered.

15. When loading a load, the dimensions were found to be good at the beginning, but after a few hours, the dimensions were changed, and the dimensions were unstable.

The reason may be that the cutting forces were all new at the beginning because the cutters were all new. It is not very large, but after some time, the tool wears, and the cutting force becomes more extensive, which causes the workpiece to shift on the chuck, so the size is always running and unstable.

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

17. The subroutine in the FANUC system has 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 last three digits of L are the number of cycles.

18. The arc’s starting point does not change; the end of the arc is shifted by a mm, and the position of the bottom diameter of the arc is moved by a / 2.

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

20. If the tool holder is used for drilling, the drill bit can be rotated to change the hole diameter.

21. When drilling the stainless steel center eye, or when drilling the stainless steel eye, the drill bit, or the center drill center must be tiny. Otherwise, it cannot be moved. When drilling with a cobalt drill, do not grind the groove to avoid the drill annealing during the drilling process.

22. According to the process, there are generally three types of blanking: one for each material, two for each material, and the entire rod for each material.

23. The material may be loose When the ellipse appears in the car’s thread. Use a dental knife to cut a few more.

24. In some systems where macro programs can be entered, macro programs can be used instead of subroutine cycles. This saves the program number and avoids a lot of trouble.

25. If the drill is used for reaming, but the jitter of the hole is significant, then a flat bottom drill can be used for reaming, but the twist drill must be short to increase rigidity.

26. The hole diameter may vary if you drill directly with a drill on a drilling machine. Still, if the hole size is enlarged on the drill machine, such as using a 10MM drill to expand the hole on the drill machine, the expanded hole diameter is generally Around three wire tolerance.

27. In the car’s small hole (through hole), try to make the chips continuously curl and then discharge from the tail.

The main points of the chips are: first, the position of the knife should be appropriately high, and second, the appropriate blade inclination angle, and the amount of knife And the feed rate, remember that the knife cannot be too low or it is easy to break the chip. If the secondary deflection angle of the blade is large, the toolbar will not be stuck even if the chip is damaged. If the secondary deflection angle is too small, the chips will jam the tool after the chip breaking. The pole is prone to danger.

28. The more extensive the shank cross-section in the hole, the more difficult it is to vibrate the knife. Also, a strong rubber band can be attached to the shank because it can absorb vibration.

29. In the copper hole of the car, the tip R of the knife can be significant (R0.4-R0.8), especially when the taper is under the vehicle; the iron parts may be small, and the copper parts will be very chipped.

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