1. Effects on cutting temperature: cutting speed, feed rate, and depth of cut, effects on cutting force: depth of cut, feed rate, and cutting speed, effects on tool durability: cutting speed, feed rate, and depth of cut.
2. When the negative cutting depth doubles, cutting force doubles, when the feed rate doubles, cutting force increases by approximately 70%, when cutting speed doubles, cutting force gradually decreases. In other words, if using G99, increasing cutting speed will not significantly alter cutting force.
3. Cutting force and temperature can be assessed based on chip ejection patterns to determine if they fall within normal ranges.
4. When the measured actual value X exceeds 0.8 times the drawing diameter Y during concave arc turning, an R-value at the starting point may cause tool rubbing when using a tool with a secondary rake angle of 52 degrees (i.e., a commonly used tool with a primary rake angle of 35 degrees and a total rake angle of 93 degrees).
5. Chip color temperature indicators:
White: <200°C
Yellow: 220–240°C
Dark blue: 290°C
Blue: 320–350°C
Purple-black: >500°C
Red: >800°C
6. FUNAC OI mtc default G-code functions:
G69: Function unclear
G21: Metric dimension input
G25: Disables spindle speed fluctuation detection
G80: Cancels fixed cycle
G54: Default coordinate system
G18: Selects Z/X plane
G96 (G97): Constant linear speed control
G99: Feed per revolution
G40: Tool tip compensation canceled (G41 G42)
G22: Travel detection enabled
G67: Macro program mode call canceled
G64: Not clear
G13.1: Polar interpolation mode canceled.
7. External threads are typically 1.3P, internal threads are 1.08P.
8. Thread cutting speed S1200/pitch × safety factor (typically 0.8).
9. Manual tool tip R compensation formula:
– For chamfering from bottom to top:
Z = R × {1 – tan(a/2)}
X = R × {1 – tan(a/2)} × tan(a)
– For chamfering from top to bottom, replace subtraction with addition.
10. For every 0.05 increase in feed rate, reduce spindle speed by 50–80 rpm. This is because lowering speed reduces tool wear while cutting force increases more gradually, thereby counteracting the effects of increased feed rate on cutting force and temperature rise.
11. Cutting speed and cutting force critically impact tool performance, excessive cutting force is the primary cause of tool breakage. Relationship between cutting speed and cutting force: At constant feed rates, faster cutting speeds gradually reduce cutting force. However, higher speeds accelerate tool wear, progressively increasing cutting force and temperature. When cutting force and internal stresses exceed the insert’s tolerance, tool breakage occurs (factors like temperature-induced stress and hardness reduction also contribute).
12. During CNC turning operations, pay special attention to the following points:
(1) Most economical CNC lathes in China currently use standard three-phase asynchronous motors with variable frequency drives for stepless speed control. Without mechanical reduction, the spindle often lacks sufficient torque at low speeds. Excessive cutting loads can easily cause stalling. However, some machines equipped with gear-shifting mechanisms effectively address this issue.
(2) Whenever possible, ensure a single tool completes the machining of one part or one work shift. For large-part finishing, take special care to avoid tool changes mid-process to guarantee single-setup completion.
(3) When threading with CNC lathes, employ the highest feasible speeds to achieve high-quality, efficient production.
(4) Use G96 whenever possible.
(5) The fundamental principle of high-speed machining is to exceed thermal conduction rates through feed rates, expelling cutting heat with chips to isolate it from the workpiece. This minimizes workpiece temperature rise. Thus, high-speed machining involves pairing very high cutting speeds with high feed rates while selecting minimal depth of cut.
(6) Pay attention to tool tip radius compensation.
13. Vibration and tool breakage frequently occur during groove turning. The root cause lies in increased cutting forces and insufficient tool rigidity. A shorter tool projection length, smaller rake angle, and larger insert area all enhance rigidity, enabling the tool to withstand greater cutting forces. However, a wider groove tool can handle larger cutting forces, but its cutting forces also increase accordingly. Conversely, a narrower groove tool can withstand smaller forces, but its cutting forces are also reduced.
14. Causes of vibration during groove turning:
(1) Excessive tool overhang reduces rigidity.
(2) Slow feed rate increases unit cutting force, causing significant vibration. Formula: P = F / Depth of Cut × f, where P is unit cutting force and F is cutting force. Excessively high spindle speed may also cause tool vibration.
(3) Insufficient machine rigidity—the tool can withstand cutting forces, but the machine cannot. Simply put, the machine cannot handle the load. New machines rarely exhibit this issue, affected machines are either outdated or frequently subjected to machining-intensive operations.
15. When machining a workpiece, dimensions may initially appear accurate but become unstable after several hours of operation. This occurs because new tools exert lower cutting forces initially. As the tool wears over time, increased cutting forces cause the workpiece to shift within the chuck, leading to dimensional instability.
16. When using G71, the values of P and Q must not exceed the total number of program sequences, otherwise, an alarm will occur: “G71-G73 command format incorrect.” This is at least the case in FANUC systems.
17. Subprograms in FANUC systems have two formats:
(1) P000 0000: The first three digits indicate the number of cycles, and the last four digits are the program number.
(2) P0000L000: The first four digits denote the program number, and the three digits following “L” indicate the number of cycles.
18. If the arc starting point remains unchanged but the endpoint is offset by a mm in the Z-direction, the arc’s base diameter position shifts by a/2.
19. When drilling deep holes, do not grind the flutes on the drill bit to facilitate chip evacuation.
20. When using a tool holder for drilling with a fixture, rotating the drill bit can alter the resulting hole diameter.
21. When drilling center holes or holes in stainless steel, the drill bit or center drill must be smaller, otherwise, drilling becomes impossible. When using cobalt drill bits, avoid grinding grooves to prevent annealing during drilling.
22. Material cutting methods generally fall into three categories: single-piece cutting, dual-piece cutting, and full-bar cutting.
23. Elliptical threads during turning may result from material loosening. Resolve this by re-tapping the thread multiple times with a tap.
24. In systems supporting macro programs, use macro sequences instead of subroutine loops. This conserves program numbers and avoids complications.
25. If using a drill bit for reaming causes significant hole runout, switch to a flat-bottomed reamer. Ensure the twist drill is short to enhance rigidity.
26. When drilling holes directly on a drill press, the hole diameter may deviate. However, when reaming on a drill press, the dimensions generally remain stable. For example, reaming a hole with a 10mm drill bit on a drill press typically yields a hole diameter within a tolerance of about 0.03mm.
27. When turning small holes (through holes), strive to achieve continuous chip curling and discharge from the tailstock. Key points for curling chips: 1. Position the tool appropriately higher. 2. Adjust the cutting edge angle, depth of cut, and feed rate. Remember: Do not position the tool too low, as this may cause chip breakage. If the secondary rake angle is large, chip breakage will not jam the tool holder. However, if the secondary rake angle is too small, broken chips may jam the tool holder, posing a safety hazard.
28. A larger cross-sectional area of the tool shank within the hole reduces tool vibration. Additionally, securing a strong rubber band around the shank can help absorb vibrations.
29. When boring holes in copper, the tool tip radius (R) can be appropriately larger (R0.4~R0.8), especially when boring downward tapers. While iron parts may not be affected, copper parts are prone to severe chip jamming.
