ian maybury
06-18-2015, 4:43 PM
I'm setting up a new RF31/ZX30M format Chinese made and UK sourced mill drill. 1.5kW, 50Hz, 230V, and have run into a problem. It runs when the start button is held down, but stops immediately it's released.
The machine is fitted with a UK style three contact solenoid closed/spring to normally open NVR (no volt release) switch, plus safety switches on the splash guard and the belt drive cover. The two safety switches, the solenoid/coil and the third of the contacts seem to be wired in series and to take power via a tapping/loop from the live feed to the motor. So far as i can figure pressing the green start button manually makes the three contacts, but once this is done the feed to the motor is live and this energises the solenoid through the above tapping - holding the contacts closed and keeping the machine running. Pressing the red stop button presumably reverses the effect of the start button - once it momentarily opens the contacts the solenoid is powered down and the spring drives the contacts to the fully/normally open position. The machine stops.
Opening either or both of the above safety switches also breaks the circuit in this same loop, with similar results - the contacts spring open and the machine stops. There's a 'pseudo' E stop button, but it's placed over the main/red stop button and bears directly on it to stop the machine. (it has no independent electrical action)
Presuming the above is correct, and guessing that the safety switches need adjustment to keep it running I'm a bit thrown by the thought that pressing and holding down the green run button causes the machine to go even if the two safety switches are open, and would appreciate some informed views on whether this likely makes sense or not.
Thanks
PS I should say that the machine itself at this early stage seems mechanically pretty solid. It'll win no prizes for silky smooth operation of the various controls, fine finishing or careful assembly (loose stuff all over the place including a few majors, and the motor will probably be headed for the skip fairly soon in favour of a VFD controlled local model) - but (subject to testing for runout, alignments etc) it seems to run pretty true and be tight.
The machine is fitted with a UK style three contact solenoid closed/spring to normally open NVR (no volt release) switch, plus safety switches on the splash guard and the belt drive cover. The two safety switches, the solenoid/coil and the third of the contacts seem to be wired in series and to take power via a tapping/loop from the live feed to the motor. So far as i can figure pressing the green start button manually makes the three contacts, but once this is done the feed to the motor is live and this energises the solenoid through the above tapping - holding the contacts closed and keeping the machine running. Pressing the red stop button presumably reverses the effect of the start button - once it momentarily opens the contacts the solenoid is powered down and the spring drives the contacts to the fully/normally open position. The machine stops.
Opening either or both of the above safety switches also breaks the circuit in this same loop, with similar results - the contacts spring open and the machine stops. There's a 'pseudo' E stop button, but it's placed over the main/red stop button and bears directly on it to stop the machine. (it has no independent electrical action)
Presuming the above is correct, and guessing that the safety switches need adjustment to keep it running I'm a bit thrown by the thought that pressing and holding down the green run button causes the machine to go even if the two safety switches are open, and would appreciate some informed views on whether this likely makes sense or not.
Thanks
PS I should say that the machine itself at this early stage seems mechanically pretty solid. It'll win no prizes for silky smooth operation of the various controls, fine finishing or careful assembly (loose stuff all over the place including a few majors, and the motor will probably be headed for the skip fairly soon in favour of a VFD controlled local model) - but (subject to testing for runout, alignments etc) it seems to run pretty true and be tight.