Cam machine with acceleration control

Apparatus for machining cam profiles, comprising, mounting means for rotatably holding a workpiece while the cam profile is being machined thereon, drive means for rotating the workpiece held by said mounting means, a machine tool for removing stock from a portion of a workpiece held by said mounting means, profile control means for providing relative movement between the machine tool and the mounting means laterally of the axis of rotation of said workpiece during the removal of stock from said workpiece portion so that a predetermined cam profile is machined thereon, speed control means including a programmable memory for storing a speed programme relating the angular displacement from a datum of a workpiece to the rotational speed required for a subsidiary constant stock removal rate for said predetermined cam profile, means for monitoring said instantaneous angular displacement of the workpiece and for referring to the memory of each time a change in the rotation of speed of the workpiece is required by said speed programme for data relating to the new rotational speed, a speed counter of which the output is connected to the drive means via a digital-to-analogue converter, for storing a speed count indicative of the required instantaneous rotational speed of the workpiece, means for determining the difference between the content of the speed counter and a new speed count indicative of a new rotational speed when a change of rotational speed is dictated by said speed programme and for altering the content of the speed counter to equal the new speed count, wherein the improvement comprises the provision of acceleration control means which are connected to the input of said speed counter to control the rate at which its contents are altered to equal the new speed count and hence the rate at which the rotational speed of the workpiece is changed, said acceleration control means being arranged to receive and store acceleration data relating to the current rotational speed change, derived from said new rotational speed data each time the content of said speed count is altered to equal a new speed count.