Thread: HafCo HM-47 milling machine electrical problem

Hi all,
Machine stopped starting motor today - yesterday was all OK.
All electrics seems starting OK - pump, DRO, all lights, etc.
Fuses are OK
When I press buttons forward/reverse on panel nothing happens.
When I push little knobs on KM1/KM2 switches inside box motor start rotating forward/reverse so I think motor is OK but there is some relay issue?
Can someone direct me where I need to dig?
20240926_183237KP.jpg20240926_183230KP.jpg20240926_183247KP.jpg

KM1 and KM2 are the relays (actually contactors).

If the light HL1 on the control panel is working (that will be the 'Power' indicator top right of the panel), then according to that diagram both the 24v transformer and fuse FU2 must be working.

In which case, the problem has to be between fuse FU2 and the 24v coils of KM1 and KM2 below, so switches SB1, SQ1 and SB2. If both forward and reverse aren't working, then it's unlikely to be SB3 and SB4.

Best guess - you've accidentally knocked the Emergency Stop button SB1 in the lower left of the panel. Turn it clockwise to reset it. You wouldn't be the first to have done this one, and looking at the layout of the HM47 panel it'd be very easy to hit that instead of the normal stop...

Second guess - SQ1 doesn't appear to be on the front panel, I strongly suspect it is an interlock switch on the chuck guard. On some machines the screws retaining the guard can slip, and closing the guard doesn't actually press the switch. If the guard is removed, check that whatever is being used to jam the switch closed is still doing so.

Beyond that, you've going to have to do some digging with a multimeter (or pay someone to do it). Slight possibility that the Stop button SB2 is stuck open, or a else a wire may have come adrift in the back of one of those switches.

The suggestions provided (by Jekyll and Hyde) around the emergency stop knob buttons and the interlock switch on the guard is great as a first pass.

Beyond that as he mentioned, it will require probing via a multimeter.

I think a disclaimer does apply here: You are working with electrical mains wiring. Your either know what you are doing or you are out of your league on this. Make a sensible decision on how much more involved you want to be with the troubleshooting and take into account risks involved along with possible consequences. Ideally an industrial sparky will be recommended for probing and troubleshooting since mains wiring is involved.

Originally Posted by kafie1980

The suggestions provided (by Jekyll and Hyde) around the emergency stop knob buttons and the interlock switch on the guard is great as a first pass.

Beyond that as he mentioned, it will require probing via a multimeter.

I think a disclaimer does apply here: You are working with electrical mains wiring. Your either know what you are doing or you are out of your league on this. Make a sensible decision on how much more involved you want to be with the troubleshooting and take into account risks involved along with possible consequences. Ideally an industrial sparky will be recommended for probing and troubleshooting since mains wiring is involved.

Great thanks, kafie1980 and Jekyll and Hyde!
Indeed, that was safety(guard) switch. Plastic guard was removed while ago and rotating mount was slightly turned away - probably, I touched it when was covering machine after work.