Homebrew PCBs

Dave and Jan,

Yes, these big machines took lots of air to run them. The air 
requirements are because of the air bearing table and spindle 
sleeves. Each axis glides on a cushion of air in these systems. 

Our air source was a 15 HP, 60 CFM rotary screw compressor. It would 
carry all three of our machines but it was a rare occasion when more 
than two machines were running at the same time. 

The spindle motors have high frequency three phase motors. There is a 
frequency converter in the machine that drives a high voltage 
transistor output stage at about 150 volts. The frequency is 
controlled by the CPU and displayed on the CRT screen as spindle 
speed. 

If you ever get the chance to watch one of these Excellon machines 
run you will certainly be amazed. Try to watch even one hole being 
drilled and ten more will be drilled before your eyes can focus on 
one... these machines really scream.

Tom


--- In Homebrew_PCBs@yahoogroups.com, JanRwl@A... wrote:
> In a message dated 1/18/2003 6:17:44 AM Central Standard Time, 
> twb8899@y... writes:
> 
> 
> > Several types of spindles were available but I used the 60,000 
rpm 
> > drill/route spindles on the EX-200 and 80,000 drill only spindles 
on the 
> > other machines. The air requirements for these machines was about 
20 cfm at 
> > 90 psi.
> 
> Tom:  
> 
> TWO points:  60,000 and 80,000 RPM?  Were these "high frequency" 
motors, or 
> "brush motors"?  TEFC, I would assume!
> 
> WOW, 20 CFM at 90 PSI!  That would keep a 10 hp compressor running 
possibly 
> over 50% duty-cycle!  Wouldn't it?
> 
> Jan Rowland
> 
> 
> [Non-text portions of this message have been removed]