On Wednesday, December 7, 2016 at 4:16:41 AM UTC+7, DaBit wrote: > > > >No, I don't think anyone is interested in being judged in comparison to >> linuxcnc (or Mach for that matter) >> >You can diff the repos and look at the documentation for specific >> features / differences. >> >> It is not about 'being judged'. It is about 'what advantages would > MachineKit provide me over LinuxCNC?'. I am struggling with this also. > > I am happily running LinuxCNC on my mill and lathe, and now I am > contemplating a 3D printer. Not because I would like to have a functional > 3D printer asap, but because I like to construct and tinker. See it more as > a motorcyclists way of thinking: 'the destination is the excuse'. Here is a > screenshot of the thing under construction: > https://dl.dropboxusercontent.com/u/2762301/3dprinter/frame5.png > > I have been succesfull at running LinuxCNC on a Raspberry Pi using a cheap > ($2,51) USB-connected STM32 board on that thing: > https://www.youtube.com/watch?v=5WsugS7hTLk > Works well enough, even considering the fact that USB is just not optimal > for this purpose (I did that STM32/USB thing to be able to do a LinuxCNC > workshop on laptops). So I more or less decided to base the controller on a > Pi with the 7" touchscreen and use SPI-controlled L6470 dSpin drives for > the motors. Waiting for those to arrive from China; will take a few weeks. > > I know how to do this using LinuxCNC. Write a few HAL components to drive > the hardware, remap some G-codes, etc. > However, what I don't know is whether Machinekit would be a better > platform for this and why. When I look at the documentation I mostly see > things that are familiar from LinuxCNC. The developer manual talks about > NML, I'm seeing the familiar Axis/Touchy/Mini/etc. GUI's and no > Machineface/Cetus, etc. Hard to figure out what the strong and weak points > of MK are compared to LCNC. > > Questions, for example: > - How similar to LinuxCNC is it to write components in C? > - Does MK use the actual servo cycle time instead of assuming it is 1ms > for a 1kHz servo thread? It is not really important that the time between > invocations of the component functions is 800us at time t and 1200us at > time t+1. Computers can calculate, so when moving in a straight line at > 100mm/s position has advanced 0,08mm for time t and 0,12mm for time t+1. > Same goes for integrators in a PI controller, etc. However, the LinuxCNC > assumption that 1ms has passed (and just passing a period of 1e6 nsec to > the components) is not optimal, especially on a system with a fairly high > jitter such as a Pi and a motion platform capable of high accelerations. > - Does the trajectory planner still switch back to 'slow' when using more > than only XYZ axes, forcing the use of velocity-based extrusion as a > workaround? > > I guess I have to try out MK to find the answers. >
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