RE: [CAD_CAM_EDM_DRO] Re: CAM Software Advice for Shopmaster CNC

Hi Wayne,

> John:
>
> The buffer board with the PIC16F877 can generate a step
> every 20uSec. However, I'm not sure that there is any
> realistic way to ramp a stepper up to that speed. I
> think a step every 100uSec is a more realistically
> obtainable rate -- call it 10KHz step rate. It won't
> win any of the Inch/Min. derbies out there, but quite
> respectable for a table top machine.
>

I have my ELS running a 10 uStep/Step at 20kHz which is 50uS per step
maximum. It used to be 25kHz (40 uS) but I just ran out of processor
time since the interrupt routine is also doing the micro-stepping
support for the LMD18245 drivers.

> The software performs all of the computations in floating
> point and quantizes at the very end. Thus, as the hardware
> step rate improves, the software does not need to be
> rewritten.
>
> My next rev. of the buffer board will probably be to
> switch over to an Atmel AVR processor (probably an
> ATMega168) to pick of a factor of 5 or more in speed.
>

Microchip has just announced (no samples yet) the 32 bit MIPs series
processors pin compatible with some of their dsPIC processors. They are
making available the various stacks and FAT16 file code. Makes my tray
of 16F877 PICs even older and sadder...

> After that, I intend to tackle the bandwidth bottleneck
> and switch over to 10MB Ethernet using a Microchip
> ENC28J60 chip. After that, I would speed up the
> microcontroller again, -- either an ARM or an FPGA.
> I'm leaning towards the FPGA, since they are kind of
> neat devices I've always wanted to figure out.
>
> Does that answer your questions?

I've always got lots more questions. <grin> But for now I've got so
many work-work projects on my plate in addition to the ELS that I have
to hold myself back from getting started on yet something else. The
layout of the latest ELS rev is done and I'm just prettying it up a bit
-- consistent trace widths and spacing etc. Prototype boards will be
ordered this week; schematic has already been posted.

I still have 3 more castings to make so that I can mount up the bits and
pieces for my ELS (Rev 0.1 prototype) controlled back fence for my 3:1
shear/brake/roller. Haven't even started on the software for that.
Can't wait till I can key in in a shear dimension or bend dimension and
have the fence move to the right spot.

John

>
> -Wayne
>
>
>
>
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