17. When turning a slender shaft, what are the benefits of using reverse feed instead of forward feed?

Answer: Under normal circumstances, slender objects are easy to bend under pressure but not easy to deform under tension. Use forward feed (by

When turning (the tailstock feeds toward the main spindle box), since the workpiece is clamped in the chuck, the axial separation produced during cutting

The force directed toward the spindle box puts pressure on the workpiece, which can easily bend the slender shaft. And using reverse feed (from the main spindle box to the tail

When turning (feed in the direction of the tailstock), the axial component generated by the cutting pulls the workpiece toward the tailstock. If the center tip is

If the tightening force is small or an elastic rotary top is used, the workpiece will be in a state of tension, which will not easily cause bending and reduce the pressure.

Deformation of elongated shafts.

18. What measures can be taken to reduce or eliminate vibration during processing?

Answer: For forced vibration, the vibration can generally be eliminated by finding out the source of the disturbing force and trying to eliminate it.

For self-excited vibration, low-frequency vibration can be reduced or eliminated by using the following measures:

(1) Improve the rigidity of the process system, especially the rigidity of the workpiece, boring bar, tailstock and weak links.

sex.

(2) Reduce the clearance of moving parts.

(3) Grind the tool and change the tool clamping method. Change the direction of cutting force and reduce the impact on the workpiece

The technology system reduces the cutting force in the rigid direction.

(4) Change the geometric parameters of the tool and change the cutting parameters.

To eliminate high-frequency vibration, in addition to increasing the rigidity of the tool and workpiece, impact or vibration-absorbing devices can also be used.

19. When turning cylindrical workpieces, what factors of the machine tool are related to the taper defect?

Answer: Factors related to machine tools that cause taper defects in turning workpieces include:

(1) The parallelism of the saddle movement relative to the spindle axis is out of tolerance.

(2) The bed guide rail surface is severely worn.

(3) When the workpiece is clamped between the two centers for processing, taper occurs because the tailstock line and the spindle axis do not coincide.

(4) The bed anchor bolts are loose, causing the machine tool level to change.

20. How to check the flatness error of the finished turning end face in the working accuracy of the lathe? Write the tolerance for this item.

Answer: When checking the flatness of the finished turning end face in working accuracy, clamp a disc-shaped specimen on the chuck, with a diameter larger than or

It is equal to the maximum workpiece rotation diameter D2, the maximum length of the test piece is equal to D./8, and the finish turning is perpendicular to the end face of the spindle.

Two to three 20mm wide planes can be machined on the end face, one of which is the central plane. Use a ruler and measuring block or

Indicator inspection, the tolerance of this project is -0. 02m on 300mm diameter (only concave is allowed).