On 18 Jul 2013, at 22:15, sam sokolik wrote: > So - as far as I can tell - the original control did 1/2 stepping up to > about 19ipm - then full stepping from there to 30ipm. Now the lathe > runs fine on full stepping from 0 to 40 (maybe 45)ipm. Half stepping > only works well up to 20ipm-ish. (stalls above that) > > But why stop there.. > > I started thinking about if linuxcnc could do that.... (without coding > anything) > > A couple advantages of halfstepping.. > 1 higher resolution 0.000273403/step vs 0.000546806 per step > 2 reduced resonance.. (I have not run into this with full stepping on > the lathe) > > Then at normal cutting speeds - < 16ipm you get a higher resolution. > > So why not have 2 stepgens running. One that half steps (type 9) with > input scale of 3657.6073152 and the other full stepping (type 6) with a > scale of 1828.8036576 (lathe calculation - metric screws) > Then switch between the two stepgens at a specific feed (I picked 16ipm > with a hysteresis of 1ipm)
Nice. That's pretty much what the Gecko drives do when they morph, I think. Works well. http://www.geckodrive.com/support/application-notes/step-drives/how-morphing-works.html But your method is simpler and much cheaper. Marcus > All I can say is - HAL IS AWESOME > I setup a Lut5 with Jeff E's help (thanks jeff!) that switches the > printer port between the 2 stepgens. > A offset componant was used between the 2 stepgens to better align the > phasing. (not tweeked 100% yet) but we jogged it around - could not > tell that it was switching between the 2 stepgens and it always came > back to 0. > there is a bit more than that.. (ddt for calculating the axis velocity, > abs of that, comp w/hystorisis, and stuff I have forgotten already.) > > > And here is a halscope capture. Left side is halfstepping - right side > is full stepping. The trigger is the velocity threshold. > http://www.electronicsam.com/images/emco/Screenshot.png > > I think the offset could be tweaked more scientifically to maybe get rid > of the blip. But as it is running the 4 phases directly - it didn't > seem to effect the motion. > > here is the initial configs. > > http://www.electronicsam.com/images/emco/linuxcnc_configs/full-half_step_test/ > > again - jmk and everyone that has worked on hal - Very very awesome work! > > sam > > ------------------------------------------------------------------------------ See everything from the browser to the database with AppDynamics Get end-to-end visibility with application monitoring from AppDynamics Isolate bottlenecks and diagnose root cause in seconds. Start your free trial of AppDynamics Pro today! http://pubads.g.doubleclick.net/gampad/clk?id=48808831&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
