Subject: nc mill
From: Rotary Engine
Date: 2/21/2006, 6:55 AM
To: AA-me




Isn't the Gecko a stepper. 4Mhz sounds like a stepper.
My servos are analog. Pulse width for speed and and a bit
for direction.  I don't know whether they have brushes
or not. I don't think my servo amps care. There is no need
for anything other than the cheap PC processor mother board
with a real time operating system like Linux RT.

Furthermore my Windows computer crashes almost once a day
on average while the Linux runs 24 hours a day seven days a week
for years without crashing. It is always telling me I need
to notify Microsoft of the problem but I never do :)

I can just see it now :) I am near done with a mold taking
12 or more hours to machine and Windows crashes ruining the
part :) There is no beating having the source code out in the
open on an operating system.

There is lots of software out there that converts CAD program
software to NC codes and has been for years. Surfcam is one
of them.

Paul Lamar ...No rotor no motor.

Paul, actually GeckoDrive produces products for both stepper and servo system's
The G100 is actually a small processor all by it's self independant of any window's
timing issue's, however it is still fed by a windows based programe.

The typical hardware that I'm familiar with all produce's a step and direction
pulse, in steppers this pulse is them jumped in both power level via a 'driver' to power
the stepper. In a servo system these step and direction pulse's are seen a bit different by the driver
and it simply applies power to turn the motor 1 of two directions. The encoder is what feed's back to
confirm that the 'step' actually took place. If a encoder dies, the typical response is a runway servo.
All of the typical lower-end software packages like MACH drive your system [regardless of servo or stepper]
at up to a max of about 45000Hz, this is why the 4Mhz per axis is so exciting, that mean's we could run
an encoder at about 10 times the current resolution and not have any issue's. Also its worth mentioning that
the G100 will run 6 axis at once all at 4Mhz each, along w/ something like 22 inputs 16 outputs and a bunch
of anologe I/O stuff also. As far as your encoders you could check Usdigital, I think thats where a pile
of people are getting their encoders.

I can see why you don't like window's  :-) If mine crashed that often I'd have gone looking for a solution
in linux also. As far as Linux NC programs I think there is 1 or 2, and they may even be free-ware. If
I come across any in the future, I'll let you know.

Jarrett

You got to be kidding Jarrett :) Have you not heard of EMC?
http://www.linuxcnc.org/
A major world wide effort.

Paul Lamar

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EMC (the Enhanced Machine Control) is a software system for computer control of machine tools such as milling machines.

EMC is free software with open source code.

It provides a user interface, an interpreter for "G-code" (the RS-274 machine tool programming language), and operates the actual electronic interfaces that control the motor drives on the machine tool.

It provides the "computer" functions needed to actually run the machine's electronics. It does not provide drawing (CAD - Computer Aided Design) or G-code generation from the drawing (CAM - Computer Automated Manufacturing) functions.

It can control up to 6 axes and supports a variety of  interfaces.

The motion control can operate true servos (usually analog) with the feedback loop closed by the EMC software at the computer, or open loop with "step-servos" or stepper motors.

Motion planning includes cutter radius compensation, tool length offsets, and constant velocity control.

Support for non-Cartesian motion systems is provided via kinematics. This includes hexapods (Stewart platforms and similar concepts) and systems with rotary joints to provide motion.

EMC runs on Linux using real time extensions. Support currently exists for version 2.2 and 2.4 Linux kernels with real time extensions applied by RT-Linux or RTAI patches.

Because EMC needs real time extensions it cannot be easily installed on any existing Linux distribution. The real time extensions make changes to the kernel code and do this with the normal RPM or APT get type of tools requires immense effort to support the endless possible distribution/EMC combinations. Because of this there have, to date, been no attempts to provide this type of install tool. If you do not have experience compiling the kernel, you are strongly urged to consider installing a distribution that already has the real time extensions included. Several such distributions have been created for use with EMC. They are called BDI (short for brain dead install) distributions.

The simplest way to get EMC running is to dedicate a computer to EMC and install one of the BDI (Brain Dead Install) systems. The BDI comes on a CD rom (or a downloaded image of one) and installs a complete Linux operating system with the correct patches and EMC code pre-configured. There is even a BDI-Live version that runs directly from the CD without installing anything on the computer. It requires plenty of memory and is a bit slow due to the speed of a CD drive, but it does not modify anything on the hard disk of the computer. You can check out the BDI releases HERE.

Modification of the EMC software to use other platforms (BSD, Linux 2.6 kernels, etc.) is possible, but requires significant knowledge and effort.

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