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Mach4 General Discussion / Re: Possible Feed Rate Bug?
« on: February 25, 2018, 03:30:24 PM »
smurph: Bug is present on completely stock install of MACH using simulator motion controller with zero third party plugins installed. I would see that as best case scenario so MACH should feedback exactly what was it was told.
The Sim plugin is not a motion controller. It is not real-time and it uses Windows timers to make it tick. A 10% variance in timing is quite the norm for Windows. It doesn't feed back exactly what it is told. It feeds back the feed rate that it is able to produce. The Sim plugin is used as an example for people who wish to write motion controller plugins. Therefore, it is written to use the API in a manner that real motion control plugins would use. I could make it feed back exactly what it was fed from Mach, but that would not be a very good example.
So the moral to this story is that Sim is not perfect. Windows is the "bug". It relies entirely on Windows and every Windows machine will have different timings depending on what components make it up. A real motion controller will provide better feed rate feedback. Also, it is common to have some feed rate variance when CV is in use. You will see the feed rate drop on corners. How much depends on the acceleration capabilities of the motors. But a straight line should report a feed rate VERY close to the desired feed rate. But do keep in mind that not all motion controllers will report the current feed rate at a frequency that appears instant. Some could only report at 250 millisecond intervals, for example. Also, the screen DROs will only update at the screen refresh frequency (stock is 50ms) no matter how often the feed rate is updated.
Steve