Apparatus for milling cams and the like, as for swiss-type screw machine cams

Abstract

The invention is directed to a novel apparatus for milling Swiss-type screw machine cams. The invention provides a highly simplified and economical numerically controlled system enabling Swiss-type screw machine cams and similar articles to be milled with an ease and precision heretofore unattainable otherwise than with highly sophisticated and costly equipment. In its most typical application, the invention is utilized in the retro-fitting of an existing .Iadd.cutting machine, such as a shaping or .Iaddend.milling machine apparatus of otherwise conventional construction. Alternatively, the invention can be applied in the first instance in connection with the manufacture of modified milling machines incorporating the new control system. The system of the invention utilizes a conventional three axis .Iadd.cutting machine, such as a shaping or .Iaddend. milling machine, which is fitted out with a rotary table. Numerically controlled stepping motors are provided for the "X" and "Y" axes of the .[.milling.]. machine, as well as for the rotary table. An otherwise conventional linear interpolator system, which is substantially self contained and commercially available, is connected between one of the linear axis stepping motors and the rotary table stepping motor. By appropriate control of the linear and rotary stepping motors through the linear interpolator, precise, continuous path cutting of involute cam curves is made possible. Such curves are widely utilized in cams for controlling the operation of Swiss-type screw machines, for effecting cutting tool movement at a constant linear speed. For some Swiss-type screw machines, where the desired cam contour departs slightly from the true involute to accommodate the geometry of the tool supporting arms, the system of the invention provides for programming of the linear and rotary axes to move in the nominal involute relationship, and the "Z" axis of the machine is actuated by a simple mechanical device to introduce the necessary minor geometrical corrections. The system of the invention provides a highly simplified and economical system for performing a complex .[.milling.]. .Iadd.cutting .Iaddend. operation in the production of precision control cams for Swiss-type screw machines.

I claim: 
     
       1. An N/C controlled system for cutting involute and/or corrected involute cam profiles for Swiss-type screw machine control cams, which comprises, a. a .[.milling.]. machine having a cutting head and a work supporting slide,   b. said slide having at least one linear axis of movement,   c. a work-holding rotary table mounted on said slide,   d. said cutting head mounting a .[.milling.]. cutter engageable with a cam blank on said rotary table,   e. N/C controlled motors driving said rotary table through rotary movements and said slide through linear movements, and   f. an N/C program control, including a linear-to-linear continuous path interpolator, connected to said table driving motor and said slide driving motor to effect integrated linear and rotary movements of a cam blank relative to said cutter.   
     
     
       2. An N/C controlled system according to claim 1, further characterized by a. means interconnecting said motors and the respective slide and rotary table for translating incremental rotary movement of said motors into incremental linear movement of said slide and incremental rotary movement of said table,   b. the incremental movement of the slide being not more than 0.0001 inch per rotary increment of the motor, and   c. the incremental movement of the rotary table being not more than 0.01 degree per rotary increment of its motor.   
     
     
       3. An N/C controlled system according to claim 2, further characterized by a. said .[.milling.]. machine having a second slide mounted along a linear axis disposed at right angles to the first linear axis,   b. an N/C controlled motor for said second slide,   c. means interconnecting said second slide and its motor providing for a linear increment of second slide movement on the order of 0.001 inch per rotary increment of its motor, and   d. selector switch means for connecting the motors for the first or second slides alternatively in association with said rotary table through said interpolator.   
     
     
       4. An N/C controlled system for cutting involute and/or corrected involute cam profiles for Swiss-type screw machine control cams, which comprises, a. a .[.milling.]. machine having a cutting head and a work supporting slide,   b. said slide having at least one linear axis of movement,   c. a work-holding rotary table mounted on said slide,   d. said cutting head mounting a .[.milling.]. cutter engageable with a cam blank on said rotary table,   e. N/C controlled motors driving said rotary table through rotary movements and said slide through linear movements.   f. an N/C program control, including a linear-to-linear continuous path interpolator, connected to said table driving motor and said slide driving motor to effect integrated linear and rotary movements of a cam blank relative to said cutter,   g. a second slide having a second linear axis of movement at right angles to said first linear axis, and   h. correcting cam means being provided, operative to effect tangentially directed movement of the cutter relative to the circumferential edge of the cam blank, independent of the rotary movement of the rotary table and in accordance with linear movements of said work supporting slide.   
     
     
       5. An N/C controlled system for cutting involute and/or corrected involute cam profiles for Swiss-type screw machine control cams, which comprises, a. a .[.milling.]. machine having a cutting head and a work supporting slide,   b. said slide having at least one linear axis of movement   c. a work-holding rotary table mounted on said slide,   d. said cutting head mounting a .[.milling.]. cutter engageable with a cam blank on said rotary table,   e. N/C controlled motors driving said rotary table through rotary movements and said slide through linear movements,   f. an N/C program control, including a linear-to-linear continuous path interpolator, connected to said table driving motor and said slide driving motor to effect integrated linear and rotary movements of a cam blank relative to said cutter,   g. means interconnecting said motors and the respective slide and rotary table for translating incremental rotary movement of said motors into incremental linear movement of said slide and incremental rotary movement of said table,   h. the incremental movement of the slide being not more than 0.0001 inch per rotary increment of the stepping motor,   i. the incremental movement of the rotary table being not more than 0.01° per rotary increment of its stepping motor,   j. a second N/C controlled stepping motor providing for a linear increment of slide movement on the order of 0.001 inch per rotary increment of the stepping motor, and   k. control means for selectively rendering effective one or the other of the linear movement-producing stepping motors.