Re: Re: Any DeskCNC or DeskWinNC users out there???

> Date: Mon, 24 Feb 2003 14:18:26 -0000
> From: "forumtvm <forumtvm@...>" <forumtvm@...>
>Subject: Re: Any DeskCNC or DeskWinNC users out there???


> I have DeskWinNC board connected to Dan Mauch's 2A driver (half step)
> to Sherline 5410 (metric) + Sherline Motor
>
> For a pure single axis move, the motor begin to stall at 18 ipm which
> will make it 18 x 25.4 x 400 = 182880 steps/min or 3048 steps per
> sec. Not sure if it is the driver board or pulse generator that is
> limiting the max speed. Anyone has any idea how to find out?

Peter, Check out this chart:

http://www.empiremagnetics.com/global_pages/torque_charts/calc_st_torq_U21.htm

They have graphed the torque curves for a stepper motor at various
supply voltages. Note on the top chart (2 amp motor), curve #2. At 5 rps (revolutions per second)
the torque drops from over 50 to around 17.

If you have a 20 tpi sherline direct drive system, this is around 300 rpm at 15
inches per minute (20*15=300). If you are using a 24 volt supply and a motor
with similar torque curves, you are limited by the top end of the motor at the
rated voltage. It has nothing to do with the DeskCNC program or controller
board. Both of which can outrun the motor and voltage of nearly any CNC mill
with the serial port, and with the 5X speedup of the USB, will be able to outrun
most CNC router applications too. The USB will be a chip upgrade, which in
the past has been about $25 for Deskwinnc.

The 300 block limit on throughput will yield 22.5 ipm at .00125 average block
size (.00025 in /step * 5, minimum size for continuous contouring to work).
This is a minimum as the normal average block size
is probably more like 1 or 2 inches when pocketing or drilling.

The step limit on the DeskCNC controller itself is over 40,000 steps per second
with 3 axis interpolated motion.

For those that are trying out the deskCNC demo, a new build (2.013) has been
uploaded tonight. It has some improvements in the STL file handling (auto Z set
to top of model) and the tool tables have been upgraded to include tool angles for
tapered tools.

Best Regards, Fred Smith- IMService

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