RE: [CAD_CAM_EDM_DRO] upgrade cnc

Reversing DC motors, you can do it instantly, BUT!!!

I used to work for a while at Darlington rolling mill in England

The steel went under huge rollers, 6ft diameter and about 6 ft long solid
steel. These were driven by a huge DC motor of about the same size with a 6
inch diameter drive shaft, direct coupled. They would send the metal down
through the mill, don’t know how many revs the rollers were doing, but the
metal flew through at a very fast rate.

Now the reversing of the motor bit, no deceleration, apparently that wasted
time on the mill, instead they just used a huge contactor and swapped the
polarity, with a very loud shriek, bang and ammeters canned on the end stops
the rollers would reverse in fractions of a second, absolutely amazed me.
The mill was breaking these 6 inch diameter motor shafts, at £5000 each plus
a motor rewind, the group I was with continually rebuilt 7 to 10 a month, a
very nice contract. You would have thought the down time to change a motor
and roller would have been worth considering to weigh against a short
deceleration time, but !!!





Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Bob Campbell
Sent: 17 April 2007 18:38
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] upgrade cnc



Bill,

Baldor makes a board that may help. I used one recently for a customer.
Reversing the direction of a DC motor on the fly may be a problem. You
basically need to stop the motor and reverse the wires.

Robert Colin Campbell
Bob Campbell Designs
www.Campbelldesigns.net
Mach 2/3 breakout boards
Relay boards
Spindle Speed boards
Stepper motors
Plasma Torch Height control

----- Original Message -----
From: bill hribar
To: CAD_CAM_EDM_ <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
DRO@yahoogroups.com
Sent: Tuesday, April 17, 2007 11:12 AM
Subject: Re: [CAD_CAM_EDM_DRO] upgrade cnc

Hi Bob and all who are trying to help.

guess you can't read my mind and it would help to know what the motor is
for. I want to use it to drive the spindle. In fact it is driving the
spindle now with great success. I just wanted to use the PWM signal from
mach3 to control the rpm and direction of the motor. that way i can do screw
th'ds and the like.

thanks for the help.
Bill

Bob Campbell <bob@campbelldesigns <mailto:bob%40campbelldesigns.net> .net>
wrote:
Bill,

What are you going to use the 12 DC motor for?

Robert Colin Campbell
Bob Campbell Designs
www.Campbelldesigns.net
Mach 2/3 breakout boards
Relay boards
Spindle Speed boards
Stepper motors
Plasma Torch Height control
----- Original Message -----
From: billhribar
To: CAD_CAM_EDM_ <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
DRO@yahoogroups.com
Sent: Monday, April 16, 2007 2:08 PM
Subject: [CAD_CAM_EDM_DRO] upgrade cnc

Hi all:
I am upgrading a small cnc to a more powerful cnc and am using mach-3.
what I need to know is how to interface the PWM signal from mach-3 to
drive my 12 volt DC motor. You can't just connect the output of the
parallrl port to a mosfet driver, can you??? what kind of circuit do i
need? Anyone?

thanks:
Bill

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