Re: Varispeed Motor Control

Darrell <dgehlsen@e...> wrote
On the subject of
Re: Varispeed Motor Control

>Other than using a variable frequency drive to control there
>is no way for the control to know where that type of
>mechanical speed changer is. There is no feed back to the
>control. The best way to handle speed changes in this case
>is to use a message to indicate the required speed and a
>pause to wait for you to change the speed.
>Darrell

Actually it can be done Darrell and has been on some early
CNC's If you go to
http://www.metalworking.com/dropbox/both.jpg There is a
picture there of two millers I have recently bought still on
the customers premises prior to shipping. The Green one is
an Acton Powercentre. This obviously has it's history with
the manual range as the book shows a manual method ie. Hand
wheel and the method fitted to the CNC's. If you look at the
head there is a horizontally mounted motor. This is a 110V
DC motor that winds the variable speed pulleys up and down
on a ball screw.
The way it works is that the controller puts out a speed signal and
switches the motor on. At the top of the spindle there is a tacho
generator, a spindle speed signal is sent to a speed board on the machine
and this adjust the speed via the 110V motor. On the front of the machine
is a pair of override switches for manual control.
I must admit that it's not a very good system but it was probably the best
they could do for the day.
I aim to leave this on purely on manual front panel control on this machine
as I want it as a CNC drill and one speed will do me.
If I wanted CNC controlled speed I would lock the drive into a mid range
ratio and use a 0 - 10v analog command from the controller to run an
invertor. By far the quickest and easiest way.
The grey machine is a Beaver with Fanuc 5M controller and servo's. The
green Acton is on 42 steppers with a Posidata controller, 4 axis, it has
steppers on the knee as well as the quill.
Both are up for Ahha conversions.
An existing Beaver is already on Ahha and the second system has been
bought. The third Beaver will follow after Christmas as space is a problem
at the moment.

John Stevenson,
Nottingham , England

>>----- Original Message -----
>>From: "Smoke" Smoke@5...
>>To: CAD_CAM_EDM_DRO@egroups.com
>>Sent: Tuesday, October 24, 2000 10:53 AM
>>Subject: Re: [CAD_CAM_EDM_DRO] Varispeed Motor Control

>> The machine must be set to highor low gear and then turned
>>on. The speed is then changed using a handwheel. I suspect
>>I'd have to put some sort of stepper motor attachment in
>>place of the hand wheel....leaving the hand wheel on also to
>>allow for manual use of the machine too.
>>>
>