During CNC programming, programmers must determine the use of cutting each process and writing it in the program in the form of instructions. The quantity of cutting includes cutting speed, back-food tool and power speed. For different treatment methods, different cutting doses must be selected.
1. Principles to select the use of the cut
During approximate treatment, productivity is generally mainly used to improve, but economy and treatment costs should also be taken into account; The specific values must be determined as a function of the instructions manual of the tool-machine, the cutting dosage manual, and combined with experience.
On the basis of the sustainability of the tool, the order of selecting the use of the cut is: first determine the quantity of the back-food tool, determine the flow and finally determine the cutting speed .
2. Determine the amount of knife
The quantity of the loading tool is determined by the rigidity of the tool-machine, the part and the tool. Possible, in order to reduce the number of tools and improve production efficiency.
Principles to determine the amount of knife to transport:
1) When the room surface roughness value must be Ra12.5 μm ~ 25 μm, if the treatment allocation of the CNC treatment is less than 5 mm ~ 6 mm, the requirement may be met by a power supply rough treatment. However, when the margin is large, the process system is mediocre or the machine tool is insufficient, it can be completed in several flows.
2) When the surface roughness value of the part must be RA3.2 μm ~ 12.5 μm, it can be divided into two stages: rough and semi-finishing treatment. The same as before is selected for approximate treatment. After a rough treatment, leave a margin of 0.5 mm to 1.0 mm and cut it during the half-year.
3) When the surface roughness value of the part must be RA0.8 μm ~ 3.2 μm, it can be divided into three stages: rough, semi-finishing and finish treatment. The back knife is measured 1.5 mm to 2 mm during semi-finishing. During the finish, take 0.3 mm to 0.5 mm by carrying the knife.
3. Determination of the quantity of food
The quantity of power is mainly selected according to the treatment accuracy and the surface roughness requirements of the parts and the materials of the tools and the parts. The maximum power supply speed is limited by the rigidity and performance of the machine system machine.
Principles to determine the power speed:
1) When parts’ quality requirements can be guaranteed, higher power speed can be selected to improve production efficiency. Generally selected in the range of 100 to 200 m / min.
2) When cutting, the treatment of deep holes or treatment with high -speed steel tools, it is advisable to choose a lower power speed, generally in the 20 to 50 m / min range.
3) When the treatment accuracy and surface roughness are necessary, the power speed must be smaller, generally in the 20 to 50 m / min range.
4) When the tool is empty, especially when it “comes back to zero” at long distance, you can choose the maximum power speed defined by the CNC system of the machine tool.
4. Determination of the speed of the spindle
The speed of the pin must be selected according to the authorized cutting speed and the diameter of the part (or the tool). The calculation formula is:
n = 1000v / πd
V —— The cutting speed, the unit is m / min, determined by the sustainability of the tool;
N —- Speed of the pin, the unit is R / MIN;
D —- The diameter of the diameter of the part or the tool, unit in mm.
The calculated pin speed N must finally be selected according to the instructions of the machine tool or the speed closest to the machine tool.
In short, the specific value of the cutting dose must be determined by analogy methods based on the performance of the machines, the relevant manuals combined with a real experience. At the same time, the speed of the pin, the cutting depth and the power speed can be adapted to each other to form the optimal cutting quantity.
Reference formula:
1) Measurement of the loading tool (cutting depth) AP
The vertical distance between the treated surface of the room and the surface to be treated is called the back -e -eating tool. The back tool is the amount of tool measured by the basic point of the point edge and perpendicular to the worktop. the cutting depth. Depending on this definition, if the vertical outer circle of the vehicle is in the form of calculation, the quantity of the back of the knife can be calculated as follows:
AP = （DW – DM） / 2
where AP – The measurement of the knife (mm);
DW —— The diameter of the surface of the part to be treated (mm);
DM —— The part treated the surface diameter (mm).
Example 1: The diameter of the part to be treated is φ95 mm; Now the diameter of the power truck is φ90 mm at the same time, please find the back and take the tool.
解: AP = （DW – DM） / 2 = （95 —90） /2=2.5 mm
II) Quantity of power f
The relative movement of the tool and the part in the direction of the movement of the power supply each time the part or the tool turns for a cycle.
Depending on the direction of the power supply, it is divided into vertical power supply and horizontal power. .
Note: VF power speed refers to the instant speed at which the stitch selected on the cut edge moves compared to the power supply.
VF = FN
Where VF – – power speed (mm / s);
n —— Speed of the espède (r / s);
F – – feed (mm / s).
3) Cut the VC speed
The instantaneous speed of the point selected on the edge compared to the main movement of the room. The calculation formula is as follows
VC = (π dwn) / 1000
where VC – – reduction speed (m / min);
DW —— The diameter of the surface of the part to be treated (mm);
n —— The speed of the room (r / min).
The maximum cutting speed must be calculated during calculation, as during filming, it is calculated as a function of the value of the surface diameter to be treated, because the speed is highest here and the tool is the fastest.
Example 2: Turn the exterior circle of the part with a diameter of φ60 mm, and the selected tower spindle speed is 600R / min.
Solution: vc = (π dwn) / 1000 = 3.14x60x600 / 1000 = 113 m / min
In real production, the diameter of the part is often known. The following formula:
n = (1000v c) / π dw
Example 3: Turn the outer circle of the pulley of φ260 mm on the horizontal Tour CA6140, select VC at 90 m / min and find n.
Solution: n = (1000v c) / π dw = (1000×90) / (3.14×260) = 110r / min
After calculating the speed of the tower spindle, the value close to that of the signage plate must be selected, that is to say n = 100r / min is selected as real speed of the turn.
3. Summary:
Use of reduction
1. Back to take the knife to measure AP (mm) AP = (DW – DM) / 2 (mm)
2. Food capacity F (mm / r)
3. Cutting speech VC (m / min) VC = ∏dn / 1000 (m / min)
n = 1000vc / ∏d (r / min)
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