Hello forum members. My problem is the wire feed motor does not brake I believe it has dynamic braking . The machine is a 600 amp miller mig with a model 10 em/4 control feeder. Any help much appreciated.
cheers
Is the machine still under warranty? Have you tried contacting your seller or Miller dealer?
Was the wirefeed braking previously working OK, has this problem just happened, did you do anything just before the fault happened ( such as fit a new reel of wire ) ?
If the wirefeed motor runs on DC, there will typically be a power transistor on the wirefeed control PCB that supplies a variable amount of drive power. To provide braking, a second power transistor will be switched on to short-circuit the motor armature, perhaps through a low-resistance high-wattage resistor. This forces the spinning motor to act as a generator, dumping the kinetic energy and bringing it to a rapid halt. To troubleshoot the fault, we would need to get the exact model number of the feeder, then search for a circuit diagram.
Thanks for your replys
The welder doesn,t have a delay adjustment on it.
I think it was made in 1977.
The model of the feeder is 10 em/4
if that is of any help.
The wire keeps coming after the trigger has been let go about 5 inches
cheers
5" sounds more like a relay sticking rather than a brake not working.
Find the wires to the motor and put a volt meter on them. See if it still has power after the trigger is released
The Miller forum that Munkul linked to implies that rather than electronics, the brake circuit is just a relay and a resistor. Back in 1977 things were simpler !
"Resistor R1 - 12W, 10ohm wire wound, Miller PN 030942.
Also make sure the Normally Closed (NC) contacts in Control Relay 1 (CR1) are making contact when de-energized as these complete the brake circuit."
Somewhere in the feeder you should find a relay, which operates when you press the torch trigger. Power goes to the wirefeed motor via that relay. When the trigger is released, the relay drops out, power is disconnected from the motor, and instead a pair of normally-closed ( NC ) contacts on the relay short-out the motor armature via a wire-wound resistor. The resistor may look like this:
As hotponyshoes suggested, that relay may be sticking "on", or the normally-closed contact pair may be dirty or burned, or the wirewound resistor may have burned out ( i.e. not 10 Ohms but gone open circuit ).