Purpose and principle of action of the leash cartridge. Lead cartridge. Tools and fixtures for turning

Self-gripping driving chucks chucks have two or three knurled eccentric jaws, with which they capture the workpiece at the start of cutting and cause it to rotate; As the cutting torque increases, the chuck torque automatically increases as well. Therefore, they work reliably with any chip cross-sections. Parts, as usual, are installed on fixed or floating centers. For ease of installation of parts on centers, structures with automatically opening cams are used, and to ensure uniform clamping by all cams, a floating cam system or a system with cams of independent action is used.

Rice. 11.1- Driver chuck.

Cam-driven chucks are widely used on multi-cutting lathes where high torque transmission is required.

When operating conventional eccentric chucks, there are cases when the workpiece is rotated under the action of cutting forces at the beginning of processing, which leads to breakage of the cutter. To eliminate this shortcoming and increase the automaticity and reliability of the action, lead chucks with loads based on the use of centrifugal inertia forces have recently been introduced. The introduction of these cartridges is facilitated by the speed of the spindles of modern lathes.

On fig. 11.1 shows a chuck with eccentric jaws. The chuck flange is bolted to the adapter flange or directly to the spindle flange as shown. The chuck body is connected to the flange 14 by means of screws with spacers and leading pins. The housing can move relative to the flange in the direction of its grooves, which ensures uniform clamping of the workpiece by cams 2; springs 11 return the body to its original central position.

Eccentric cams 2 are freely mounted on the fingers and have a notch on the profile. With the beginning of the rotation of the spindle, the cams, under the action of the centrifugal force developed by the weights 1, clamp the workpiece and cause it to rotate; further clamping is carried out during the cutting process. When the machine is stopped, the cams under the action of the springs 11 are automatically opened by the pushers 20. By changing the cams, the chuck can be used to clamp parts with diameters from 30 to 150 mm.

The fixing of the workpieces occurs due to centrifugal force.

Centrifugal driving chucks, depending on their diameter, can hold loads with a total weight of -3 to 6 kg. Then, for example, at G = 3 kg, R = 45 lsh, n = 500, 1000, 2000 rpm, the centrifugal force pressing the cams to the workpiece will be Pc = 34, 138, 552 kg/s, respectively.

The accuracy of the technological operation is characterized by the value of the installation error  and depends on the magnitude of the errors of basing  b, fixing  h and the position of the workpiece in the fixture  etc. In the general case, the installation error

Workpiece position error in fixture

where  p - error arising from errors in the manufacture of fixtures,  p = 15 µm;  s - error that occurs when the device is installed on the machine,  s = 10 microns;  and - the error arising from the wear of the installation parts, the amount of wear is approximately determined by the empirical dependence:

where N is the number of contacts of blanks with supports in 1 year, N = 50000; a and - empirical coefficient and exponent = 0.7, = 0.5:

The value of And is of great importance, therefore, we divide And by four, and in technical requirements we write to the equipment: change the supports after two months of operation (6 times a year). Thus, we accept  and \u003d 26 microns.

 pr === 31.63 µm.

The error of basing and fixing the workpiece is 0, therefore, the installation error is equal to the fixture error