Hi,
So, Craig, are suggesting that an ethernet cable could be used? Obviously, it can plug into the computer, but what about at the breakout board?
No, I think there is some confusion about what a breakout board and a motion controller is.
A breakout board has no 'processing power', but rather just buffers signals and offers screw terminations for wires , and maybe a relay or two, and sometimes a PWM to analogue
converter for the spindle.
A motion controller on the other hand accepts numerical trajectory data from Mach/PC and converts that numeric data into stream of pulses. In many cases the output
of the motion controller goes into a breakout board, or more than one, and then to the machine. Other motion controllers require no breakout board.
The motion controller can be connected to the PC by either a USB cable or Ethernet, with Ethernet cables having a noise advantage. Such a motion controller will require
a micro-controller and/or an FPGA to process numerical data to accurately timed pulse streams
The confusion has resulted from the way Mach was originally developed, namely the parallel port. In a parallel port PC there are two distinct software chunks running, the one
most familiar is the Mach program itself and its GUI, a Windows application. Machs task is to interpret Gcode and generate the numeric trajectory data, also called P(osition)V(elocity) over
T(ime), PVT data. The second chunk is Machs pulse Engine which is code that lives in the kernel alongside Windows. Its this software that converts the PVT data to pulse streams
and communicates that to the outside world via the printer port. So according to the definition above Machs Pulse Engine IS the
motion controller.The issue is that Machs Pulse Engine has to co-exist with Windows is very subject to stalling and jitter because of the shared processing. With an external motion controller like the UC100,
the UC300 or an Ethernet SmoothStepper that conflict does not occur because the processing of trajectory data is handled NOT by the PC but the motion controller. The hardware used
for the motion controller does just one job, and does it well. As a result the pulse streams coming from a good external motion controller are much faster, smoother and more accurately timed
without the stalling and jitter that occurs with Machs Pulse Engine. It also means that Mach, the Windows application is no longer tied to running on a 32 bit machine that was mandatory for
Machs Pulse Engine, so you can use laptops, 64 bit and Windows 10 etc, none of which were possible with Machs Pulse Engine.
In short a good external motion controller is a major step up in performance and capability over Machs parallel port. The choices we have alluded to are a (genuine)UC100, a UC300, or
an Ethernet SmoothStepper, but there are other worthy choices also like a PoKeys 57CNC, as CSMIO or a Hicon. The later two are very good but quite expensive, starting at $600USD.
If you are considering a motion controller a good purchase will result in you using that board for many years and the suggestion is consider the current requirements but also what you might like to do
in the years to come. For instance a UC100 has the equivalent of 'one parallel port' or 17 inputs and outputs. That's enough for a basic machine, but if you ever need more IO you're screwed,
whereas the UC300 has 85 inputs and outputs, or the Ethernet SmoothStepper (ESS) has 51 inputs and outputs, so either would be of use in later years. The UC100 operates up to 100kHz,
a good step up from the parallel port, but the UC300 operates up to 400kHz and the ESS up to 4MHz! Thus if you ever upgrade to servos you'll want at least the speed of the UC300
but better the speed of the ESS to take advantage of the resolution and speed that servos offer.
About eight years ago I bought an ESS (cost at that time $180USD) and Mach4 ($200USD) and have been using them ever since, and both have proven to be the best value investments in CNC
I've ever made. Machines, spindles, tools, vices, breakout boards, steppers, servos are all subject to change over the years but Mach4/ESS has the backbone right from the start.
Craig
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