mill motor direction.

Hi

I have a Chester Conquest mill and I wondered if anyone out there knew if there was an easy way to reverse the motor direction/

If I do a lot of tapped holes it would be handy to power tap them.

I was going to ask this on the Chester forum but it's been down for days .

cheers Roy.

I've replaced my single phase motors on lathe amd mill/drill with 3 phase running through an inverter so it is just the flick of a switch at the inverter control pad or remote pod

John

Roy

The simple way to do it is to fit a changeover switch in the drive motor feed. The only problem with this is that it doesn't stop the machine before reversing the motor but at low tapping speeds this is less of a problem. At high speeds the immediate switch from forward to reverse will put a significant strain on the motor and associated electronics, can blow the drive board. Normally these switches have 3 positions 'Forward - Off - Reverse' They not only switch the DC motor supply polarity but as they pass through the 'Off' position interrupt the mains feed to the machine which releases the zero-volt switch and powers the drive circuits down until activated again by the user.

As detailed above the simple way is just to fit changeover switch to the DC motor feed but be aware that prior to operating the changeover switch the spindle should be stationary. Also be aware that the feed to the motor is effectively rectified and switched mains so there is potential for electric shock unless the mill is disconnected from the mains supply.

Hope this helps

Martin

PS This assumes that the motor is a brushed DC motor which is what it looks like from the catalogue

Edited By Martin W on 23/09/2014 12:52:18

i used a simple DPDT switch on my WM14 using this wiring diagram
not sure if it would work on your machine, only you can decide that

works a treat for me
obviously you have to come to a complete stop before changing direction. but you knew that anyway, didnt you

doesnt take long to fix up

Z

Edited By Ziggar on 23/09/2014 12:52:15

Cheers guys, that was quick.

I was hoping it would be something easy, I'll use a double pole changeover switch with a centre off , that way it can stop before I reverse it.

cheers

Roy.

Hi

Farnell sell these with a center off position so at least if you do hit it accidentally its initial position will be in the OFF position which while not switching the motor driver board OFF will drop the drive to the motor off until the next/reverse position is engaged.

There are two types one with screw terminals here or these with push fit terminals with either a Metal Toggle Lever here or iof you prefer a Plastic Toggle Lever here.

Cheers

Martin

I use a tapping head which has a reverse function, simples

Hi

I too have a tapping head but on a small mill it takes up a lot space between the table and quill so not always convenient or practical.

Cheers

Martin

Bear in mind the motor supply is 300+ volts DC, not AC so you will need a switch bigger than you would use for switching mains and to keep everything well iinsulated.

The reversing switch on the mini-lathes would be suitable (it's pretty huge).

Neil.

Neil

The motor on the Chester Conquest is rated at 350W so the continuous current will only be around a couple of amps even when working hard. Secondly the switch will only be operated, in theory, at very low or zero speed settings so the major inrush/start currents will be low though there could be a higher very short lived peak. I think that a 10 - 15 amp rated switch would be more than adequate for this purpose. If my understanding is correct then the supply to the motor rather than being DC is switched fully rectified and unsmoothed mains which will have similar characteristics to that of raw mains regarding switching etc..

The first switch I referred to from CPC was incorrect as it was an Momentary On rather than a Toggle On-Off-On as per the correct version.

Martin

I have now removed the cover from the electrical box , temporarily removed the on/off switch and reversed the motor wires and the motor runs quite happily backwards.

the motor wires are quite thin so there can't be that much current.

incidentally, I also turned the switch 90 degrees so off is up and on is down rather than side to side.

where the hell did they get that idea from?

all I have to do now is find somewhere to fit the switch.

I may even try replacing the current switch ( no pun intended) with a centre off type, only thing is, there's another wire on the centre row and I don't yet know what that does.

Roy.

Hi Martin,

That switch is rated 16A DC, but only up to 125V DC.

Most of the switches listed by CPC for 250V AC are only good up to 75 or, more usually, 28V DC, so that's probably the best you can get.

The problem is not so much the amperage, but arcing welding them together as DC sparks don't self-extinguish.

Neil

Hi All

As Neil points out that DC arcing can weld the contacts together.

That is NOT a problem IF you switch off the 230 volt AC line first then as Ziggar suggests allow the spindle to STOP.

Then flick the reverse switch, then switch on the 230 volt AC line the control will then ramp up to the set speed.

No point in destroying the electrics or yourself to save a dollar or a couple of seconds in time.

Be careful out there

Eric

You could use a 3 position 2 pole switch with the motor wired to the "throw" so in the centre position it is shorted. This would stop it very quickly as you went fro fwd thru stop to reverse.

Neil

In my first post I described the action of the reversing switch as factory fitted to some of these machines and highlighted the fact that it interrupted the mains supply thereby releasing the zero volt switches and disabling the motor drive and said that prior to operating a simple reversing switch that the spindle should be stationary, perhaps more correctly that the motor should be stopped.

Secondly the supply to this type of motor is NOT DC but phase switched full wave rectified AC which is completely different. Should an arc develop then it will extinguish as the waveform approaches zero volts.

Martin