Re: [CAD_CAM_EDM_DRO] Re: Raspberry Pi for CADCAM CNC?

On 12/26/2012 10:18 AM, scyvt wrote:

> Not long ago I asked this group if there was a simple hardware/software solution for single axis control. There were two answers: 1) just use use a cheap computer running Mach, and ignore the excess capacity, and 2) hang on for Mariss to release the long-awaited FPGA-based drive that would (maybe) have that capability built-in.
>
> Would perhaps the board & Linuxcnc that you recommend be a third path to consider for this application?
>
> TIA

Even a Basic Stamp (Parallax, Inc.) can do single axis stuff, but how
fast and with what level of interactivity becomes an issue.

If programming time doesn't count, such a choice makes sense, but in
most one-off cases it doesn't.

A simple PC with 512 MB of RAM and a CF disk drive should be available
for under $100.00. There are Intel Atom based systems which have been
verified for Mach and LinuxCNC which can be built with new parts from
scratch for well under $200. Even with no monitor and keyboard and a
virtual console these can do the job for as little as $100.00 (LinuxCNC
is zero cost, Mach has a test version which will run a very limited
version for free, but Windows costs unless it came bundled in the
machine.) Setting up such a machine is pretty simple, and the drivers
and power supply are the same cost regardless of the processor.

Assuming the programmer time is worth $1.00/hour, the machine which
supports the existing program is free after 2 weeks of head scratching.
If programmer time is worth more than that (let's say $10/hour), after a
day the machine is free. You make money by having a result you want in
hand and working sooner.

VNC or Remote Desktop applications are very common, many which work well
and are free. By using a non-routable IP address not on the same
segment as your Internet gateway (e.g. your gateway at 192.168.1.1
supports a subnet of 192.168.1.1-192.168.1.254, the CNC controller is at
192.168.100.100 and nothing on the Internet can see it), the CNC machine
is pretty safe from interference. The main "work" machine has two
addresses, 192.168.1.XXX (assigned by DHCP) and 192.168.100.101 (static
assignment), only it can pass data to the CNC controller. Adding a
switch (note NOT a hub!), the CNC controller never sees any traffic
except that to the work machine.

I would use 10baseT or slow fiber connections, it reduces machine
interruptions and is plenty fast enough. Fiber tends to eliminate any
circulating ground currents.

Is this sufficient to get you started?

Dave 8{)

--

/"The first method for estimating the intelligence of a ruler is to look
at the men he has around him."/
Niccolo Machiavelli

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