CNC machining experience sharing

1,
Effect on cutting temperature: cutting speed, feed rate, back-feeding amount.
Effect on cutting force: back-feeding amount, feed rate, cutting speed.
The impact on the durability of the tool: cutting speed, feed rate, the amount of back eaten.
2,
When the amount of back-eating knife doubles, the cutting force doubles;
When the feed rate is doubled, the cutting force will increase by about 70%;
When the cutting speed doubles, the cutting force gradually decreases;
In other words, if G99 is used, the cutting speed will become larger and the cutting force will not change much.
3,
The cutting force can be judged based on the discharge of iron filings, and whether the cutting temperature is within the normal range.
4,
When the measured actual value X and the drawing diameter Y are greater than 0.8 when the concave arc of the car is turned, the turning tool with a secondary declination angle of 52 degrees (that is, our commonly used blade is a turning tool with a 35 degree main declination angle of 93 degrees) R out of the car may wipe the knife at the starting point.
5,
The temperature represented by the color of 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 generally default G command:
G69: Not very clear
G21: Metric size input
G25: Spindle speed fluctuation detection disconnected
G80: Cancel fixed cycle
G54: Coordinate system default
G18: ZX plane selection
G96 (G97): constant linear speed control
G99: feed per revolution
G40: Tool tip compensation canceled (G41 G42)
G22: Storage stroke detection is turned on
G67: Macro program modal call canceled
G64: Not very clear
G13.1: Polar coordinate interpolation mode is cancelled
7. The external thread is generally 1.3P and the internal thread is 1.08P.
8. The thread speed S1200 / pitch * safety factor (generally 0.8).
Nine, manual tip R compensation formula: chamfering from bottom to top: Z = R * (1-tan (a / 2)) X = R (1-tan (a / 2)) * tan (a) from Chamfer up and down the car will be reduced to plus
Ten. For every 0.05 increase in feed, the speed is reduced by 50-80 rpm. This is because reducing the speed means that the tool wear is reduced, and the cutting force increases slowly, thereby making up for the increase in cutting force due to the increase in feed, and the increase in temperature. The impact.
11. The impact of cutting speed and cutting force on the tool is very important. The main reason for the tool collapse due to cutting force. The relationship between cutting speed and cutting force: the faster the cutting speed, the feed will remain unchanged, and the cutting force will slowly decrease. At the same time, the faster the cutting speed will make the tool wear faster, the cutting force will increase, and the temperature will also come The higher, when the cutting force and internal stress are too large to withstand the blade, it will fall into the avalanche (of course, there are also reasons such as stress and hardness decline caused by temperature changes)
12. During CNC lathe machining, the following points should be paid special attention to:
(1) For the current economic CNC lathes in China, ordinary three-phase asynchronous motors are used to achieve stepless speed change through frequency converters. 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 be boring Car, but some machine tools have gears to solve this problem.
(2) As far as possible, the tool can complete the processing of one part or one work shift. Special attention should be paid to the finishing of large parts to avoid tool change in the middle to ensure that the tool can be processed at one time.
(3) When turning the thread with CNC turning, the highest possible speed is used to achieve high-quality and efficient production.
(4) Use G96 whenever possible.
(5) The basic concept of high-speed processing is to make the feed exceed the heat conduction speed, so that the cutting heat is discharged with iron filings to isolate the cutting heat from the workpiece and ensure that the workpiece does not heat up or less. Therefore, high-speed processing is selected very high The cutting speed is matched with the high feed and a small amount of backfeed is selected.
(6) Pay attention to the compensation of tool nose R.
thirteen,
Workpiece material cutting machinability classification table (small P79)
Common thread cutting times and back-eating knife scale (large P587)
Commonly used geometric figure calculation formula (large P42)
Inch and millimeter conversion table (large P27)
14. Vibration and chipping often occur during slotting. The root cause of all this is the increased cutting force and insufficient tool rigidity. The shorter the tool extension length, the smaller the back angle, and the larger the blade area, the better the rigidity. , The larger the cutting force can be, but the larger the width of the groove cutter can withstand the corresponding increase in cutting force, but its cutting force will also increase, on the contrary, the smaller the groove cutter can bear the smaller force, But its cutting force is also small.
Fifteen, the reason for the vibration when the car groove:
(1) The extension length of the tool is too long, which causes the rigidity to decrease.
(2) The feed rate is too slow, which causes the unit cutting force to become large, which causes a large vibration. The formula is: P = F / back-feeding amount * f P is the unit cutting force F is the cutting force, and the speed is too fast Will also shake 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 tool can not bear it. To put it bluntly, the machine car does not move. Generally, such problems will not occur in new beds. Either the machine tool killer is often encountered.
16. When a car is loaded, the size is found to be okay at the beginning, but after a few hours, the size has changed and the size is unstable. The reason may be that the cutting force is new at the beginning, so the cutting force It is not very big, but after a while, the tool wears and the cutting force becomes larger, which causes the workpiece to shift on the chuck. If you want to learn UG programming, the 616857166 group can help you, so the size is old and unstable.
17. When using G71, the values ​​of P and Q cannot exceed the sequence number of the entire program or an alarm will appear: the G71-G73 instruction format is incorrect, at least in FUANC.
18. There are two formats of subprograms in the FANUC system:
(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 the L are the number of cycles
19. The starting point of the arc is unchanged, and the end point is offset by a mm in the Z direction, then the position of the arc bottom diameter is offset by a / 2.
20. When drilling deep holes, the drill bit does not grind the cutting groove to facilitate chip removal.
Twenty-one. If the tool is used for drilling with a knife holder, the drill can be turned to change the hole diameter.
22. When drilling the stainless steel center hole, or when drilling the stainless steel hole, the drill bit or center drill center must be small, otherwise it will not move, and the groove will not be polished when drilling with a cobalt drill to avoid annealing the drill bit during drilling.
Twenty-three, according to the process of cutting materials are generally divided into three types: one material, two goods, the entire bar.
Twenty-four, when the ellipse appears when the thread is turned, it may be that the material is loose. Just use a dental knife to handle a few more knives.
Twenty-five. In some systems where macro programs can be input, the macro program charge can be used to replace the subprogram cycle, so that the program number can be saved and a lot of trouble can be avoided.
Twenty-six, if the drill is used for reaming, but the hole jumps greatly, then the flat bottom drill can be used for reaming, but the twist drill must be short to increase the rigidity.
Twenty-seven, if the hole is drilled directly with a drill bit on the drilling machine, the hole diameter may deviate, but if the size of the hole is expanded on the drilling machine, the size will generally not run. Generally around 3 wire tolerance.
Twenty-eight, in the small hole (through hole) of the car, try to make the chips continuously curl and then discharge from the tail. The main points of the curling: one, the position of the knife should be properly raised, two, the appropriate blade angle, eat The tool amount and feed amount, remember that the knife cannot be too low or it will easily break the chip. If the auxiliary angle of the tool is large, it will not jam the tool bar even if the chip is broken. If the auxiliary angle is too small, the chips will jam after the chip is broken It is easy to be dangerous if you hold the arbor.
Twenty-nine, the larger the cross-section of the cutter bar in the hole, the harder it is to vibrate the knife. There is also a strong rubber band that can be attached to the cutter bar, because the strong rubber band can play a certain role in absorbing vibration.
30. When turning the copper hole, the tip R of the knife can be appropriately large (R0.4-R0.8), especially when the taper under the car, the iron parts may be nothing, and the copper parts will be very chipped.