Which Shopbot is this?

[dray]

http://cgi.ebay.com/ShopBot-CNC-router_W0QQitemZ230153703939QQihZ013QQcategoryZ571 22QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Found this on ebay. Im looking for another shopbot for r&d and 3d laser scanning.

Anyone know which shopbot this is and hos fast it can jog/cut?

Thanks alot

D.Ray

[aaasigncom]

LOOKS LIKE A PRT

[jamesgilliam]

Danny, It looks like a late PR that has been upgraded, or a very early PRT. The reason I say this is the brand of stepper motors pictured and the way the table legs are mounted.

[richards]

Danny,
The Oriental Motor PK299-01 motor is not geared. The motor is rated at 9V (serial) or 6.4V (half-coil/unipolar). My tests with Gecko G202 and G203 stepper drivers show that 15X voltage is a good compromise between too much heat and too little speed. However, the G202/G203 stepper drivers are limited to 80V. So, you could not run the PK299-01 at it's optimum voltage for speed with a G202/G203, although you could get 10X voltage rating with a 70V power supply and half-coil/unipolar connections.

Since the motor has no gear box, you would probably get the same kind of 'chatter' that is common with the PRT-Alpha. I had to install belt-driven gearboxes on my Alpha to get rid of the chatter.

As far as speed goes, the PK299-01 motor, without gearing, and with a 20T pinion (spur gear) will travel 3.14 inches per shaft rotation. At a very modest motor speed of 150 RPM, you would get a speed of 7.85 inches per second; however, a 2A motor, without gearing, would require some significant ramp times to get to that speed.

If I were thinking of getting that particular machine, I would add at least 3:1 gearing to get the torque up to a useful level. I would add Gecko G202 or G203 stepper drivers to amplify both the speed and the resolution. (The 4g upgrade solves that problem - but I would mount the stepper drivers on a large heatsink instead of leaving them connected directly to the 4g controller card. Also, I would put in a 70V power supply to get the PK299-01 motors up to speed.)

Assuming that you could buy the machine at $4,000 and that the modifications 'only' cost another $1,500, you would be at $5,500 for a machine that is not nearly as nice as the PRS-Standard. To me, spending $8,000 for a new PRS-Standard would be the way to go.

[dray]

Thanks alot guys!!

Mike you are ALWAYS saving me $$$!!!
thx again