Re: [Emc-users] BP Knee Mill Spindle

[Jon E. <el...@pi...>]

John Thornton wrote:
> I have a BP Series 1 knee mill with an Anilam 3 axis CNC conversion and 
> a Kwik Switch spindle on it that now runs with LinuxCNC. I have a 
> GS2-23PO 3hp AC drive for the spindle. I recently added a 2500 line 
> encoder to the spindle and can now rigid tap.
>
> http://www.automationdirect.com/adc/Shopping/Catalog/Drives/GS2_%28115_-z-_230_-z-_460_-z-_575_VAC_V-z-Hz_Control%29/GS2_Drive_Units_%28115_-z-_230_-z-_460_-z-_575_VAC%29/GS2-23P0
>
> Right now I have the original 1 1/2 hp BP motor and the vari-speed head 
> on it. So I've been running it at 1800 RPM and using the vari-speed to 
> change spindle RPM which can be a bit of a pain when swapping back and 
> forth from drilling to tapping.
>
> The thought came to me yesterday after remembering my buddy had one of 
> his BP's converted to a timing belt drive and a VFD for speed control. I 
> found a 2 hp 3600 RPM inverter duty motor for $440 at automation direct.
>
> http://www.automationdirect.com/adc/Shopping/Catalog/Motors/AC_Motors_-_General_Purpose_and_Inverter_Duty_%280.25_-_300HP%29/AC_Motors_-_Inverter_Duty,_Marathon_%280.25_-_100HP%29/Marathon_Inverter_Duty_Motors_%28by_HP%29/E2006
>
> The specs say the motor will run from 350 RPM to 7200 RPM. If I gear it 
> at 1.4:1 I can get 250 RPM to 5142 RPM which the spindle should do as it 
> can do 4200 RPM now. I can tap at 250 RPM and do that now.
>
> Have I missed anything? Is this a bad plan?
>   
Why change the motor?  I do rigid tapping with the stock 1 Hp motor on
my 1J Bridgeport at 20% speed (12 Hz).  I can do this all day long with
several spindle reversals a minute with no detectable motor heating.

I leave the belt on the highest speed setting so the inertia of 
reversing the
motor is minimized.  For bigger taps, it would be needed to change the belt
for reduction.  This is the 1J head with 4 step-pulley speeds plus the
back gear.

Jon