Slender Zhou Dingyi
A shaft type part (l/d>25) with a length greater than 25 of the direct ratio is called an elongated shaft.
Clamping method for long and thin shafts
1, two, the center of the device between the slender shaft, this method is no device error, easy to ensure the workpiece coaxiality. But the rigidity is bad, easy to cause a sensation. Used for the length and diameter ratio is not large, less margin, the workpiece needs repeated installations.
2, a clip of a top clamping thin major axis, in order to prevent repeat positioning and clamping some short, or in the card up to 4mm * 20MM pad into the wire between the claw and shaft. One clip one, better than two top rigid, widely used.
When the turning length and diameter are relatively large, the reverse feed cutting method should be adopted, the tool will be drawn from the chuck side to the rear seat direction, and the workpiece will be subjected to axial tension, which will eliminate the sensation and improve the processing quality.
3. Use the base support to support the long axis
The base frame is directly supported on the workpiece, the workpiece can be segmented when turning, the groove in the central location of a supporting base blank frame, the surface roughness is small, coaxiality tolerances, and adhere to the lathe rotating coaxial base.
With the transition of slender cylindrical sleeve bearing, contact base frame supporting claw and transition sleeve, both ends of the transition sleeve are respectively provided with four screws, screw clamp blank workpiece, and adjust the transition sleeve coincidence excircle axis rotation axis and lathe.
4 、 use the heel support to support the slender axis
The two jaw follows the tool post, and the follower follows the lathe tool. The cutting resistance of the tool to the workpiece causes the workpiece to be attached to the two supporting claws of the follower, reducing deformation.
Second, three claws with the tool post, three claws with the turret below a support claw to bear the weight of the workpiece, can overcome the two claws, with the lack of tool post, so that when turning stable, not easy to cause a sensation.
With the contact pressure and the workpiece support tool to moderate, should not be too large or too small, the contact pressure is too large, showing the bamboo shaped, the contact pressure is too small, with a knife does not work, showing the polygon.
The ring type heel tool holder is arranged in the special tool carrier, and the turning tool is turned between the two rings.
Elongated shaft; thermal deformation; elongation
The effect of thermal deformation should be taken into account when the car is in a slender axle. The thermal deformation elongation of the workpiece can be calculated by the next type
Alpha Delta L= delta T lL
In L, thermal deformation and elongation (mm);
Alpha L - coefficient of linear expansion of materials (1/ DEG C);
L - total length of work (mm);
T - workpiece temperature increase (C).
Request and geometric parameters of the excircle tool for slender shafts
The excircle tool requires small cutting force, less back force, low cutting temperature, sharp cutting edge, smooth chip removal and long tool life.
Difficulties in processing slender shafts and the measures adopted
1, slender shaft rigidity is very poor, in the cutting force, gravity and so on, prone to twists and turns, a sensation;
Increase rigidity, reduce workpiece twists and turns.
Choose the base frame and the tool holder to improve the rigidity of the workpiece.
Increase the main deflection angle of tool and decrease the back force.
The reverse feed cutting method is adopted to eliminate the tension caused by the axial tension of the workpiece.
2, in the cutting process, the workpiece heating elongation, and increase the twists and turns, severe, will cause the workpiece in the center between the stuck;
Thermal deformation elongation of workpiece.
Apply the elastic reverse center to compensate the thermal deformation elongation of the workpiece.
Add sufficient cutting fluid and reduce cutting temperature.
The cutter sticks to the sharp edge and reduces the conflict between the lathe tool and the workpiece.
3. The time required for the feed at one time is longer and the tool wear is larger.
Reasonable selection of tools.
Choose the hard alloy material with good wear resistance.
Reasonable selection of tool geometry.
Precision grinding tools, cutting tool surface roughness.