The single line look-ahead is only a limiting factor when commanded g-code segments are shorter than what your acceleration settings can achieve the commanded speed in. For example if your machine is configured for 100in/sec^2 acceleration and milling at 90inchs/min it would be able to maintain full speed through g-code with segments a little less than 0.01 inch long without any slow down due to single line look-ahead.
Don't be confused by the huge slow down potentially caused by not using G93 (inverse time feeds) when you should be for mixed linear/angular commands. That slow down is caused by the F feed rate being applied in degrees/min limiting the moves speed (a 10 degree move at normal F90 will take 6.7 seconds.) A move will always be limited by which ever is slower the move's F speed in degrees/min or distance/min. If a combined move's degrees moved is greater than the linear distance moved, then the feed rate of the angular move will be controlling the time of the move. Switching from inches to mm in your G-code could also have a big effect, making the F settings 25.4 times larger, and therefore the angular moves 25.4 times faster. Todd Zuercher P. Graham Dunn Inc. 630 Henry Street Dalton, Ohio 44618 Phone: (330)828-2105ext. 2031 -----Original Message----- From: Marius <mar...@mastercut.co.za> Sent: Friday, July 07, 2023 4:17 AM To: emc-users@lists.sourceforge.net Subject: Re: [Emc-users] [Emc-developers] Trajectory planner shortcomings [EXTERNAL EMAIL] Be sure links are safe. On 2023/07/06 22:54, John Allwine wrote: > The latest software on the Pocket NC is using the same trajectory planner as > what is in LinuxCNC. > > I haven’t followed the whole thread. What seems to be wrong with the > trajectory planner when doing 4 or 5-axis? The trajectory planner only has one line look ahead for any rotary axis. So this means that trajectory planning is not really happening and performance is very poor when trying to achieve faster moves. >> On Jul 6, 2023, at 12:34 PM, Eric Keller <keller...@gmail.com> wrote: >> >> The Pocket NC runs Machinekit. I'm told machinekit has a better TP, >> but I haven't seen any evidence of that. >> >>> On Thu, Jul 6, 2023 at 12:27 PM Roland Jollivet >>> <roland.jolli...@gmail.com> wrote: >>> >>> The small 4-axis CNC machine,'Pocket Nc' uses LinuxCNC as far as I >>> can tell, and it seems to run just fine. Or does it? >>> >>> Roland >>> >>> >>> >>>> On Tue, 4 Jul 2023 at 20:16, andy pugh <bodge...@gmail.com> wrote: >>>> >>>>> On Tue, 4 Jul 2023 at 18:34, Marius <mar...@mastercut.co.za> wrote: >>>>> The problem seems to be that our trajectory planner lack the >>>>> ability to look ahead for any rotary axis. This means that a >>>>> coordinated move that includes a rotary move will be dysfunctional at >>>>> best. >>>> It's not as bad as that. >>>> >>>> There is a 9-axis blending planner in Tormach, but it's not trivial >>>> to merge it with Linuxcnc due to divergence in the codebase. >>>> >>>> If we could get hold of the patches that introduced it to Tormach >>>> then we could look at integrating it, but doing it just from >>>> comparing the code sounds hard. >>>> >>>> -- >>>> atp >>>> "A motorcycle is a bicycle with a pandemonium attachment and is >>>> designed for the especial use of mechanical geniuses, daredevils >>>> and lunatics." >>>> — George Fitch, Atlanta Constitution Newspaper, 1912 >>>> >>>> >>>> _______________________________________________ >>>> Emc-users mailing list >>>> Emc-users@lists.sourceforge.net >>>> https://l/ >>>> ists.sourceforge.net%2Flists%2Flistinfo%2Femc-users&data=05%7C01%7C >>>> toddz%40pgrahamdunn.com%7Cab74bf847dbf4526bf1508db7ec2a17c%7C575854 >>>> 4c573f47cebee96c3e0806fb43%7C0%7C0%7C638243146663401436%7CUnknown%7 >>>> CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLC >>>> JXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=TFj1jTETd5iX3h7J8%2B%2FNc3usPgZF >>>> o8N4E7lrAShUfhU%3D&reserved=0 >>>> >>> _______________________________________________ >>> Emc-users mailing list >>> Emc-users@lists.sourceforge.net >>> https://li/ >>> sts.sourceforge.net%2Flists%2Flistinfo%2Femc-users&data=05%7C01%7Cto >>> ddz%40pgrahamdunn.com%7Cab74bf847dbf4526bf1508db7ec2a17c%7C5758544c5 >>> 73f47cebee96c3e0806fb43%7C0%7C0%7C638243146663401436%7CUnknown%7CTWF >>> pbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI >>> 6Mn0%3D%7C3000%7C%7C%7C&sdata=TFj1jTETd5iX3h7J8%2B%2FNc3usPgZFo8N4E7 >>> lrAShUfhU%3D&reserved=0 >> >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lis/ >> ts.sourceforge.net%2Flists%2Flistinfo%2Femc-users&data=05%7C01%7Ctodd >> z%40pgrahamdunn.com%7Cab74bf847dbf4526bf1508db7ec2a17c%7C5758544c573f >> 47cebee96c3e0806fb43%7C0%7C0%7C638243146663401436%7CUnknown%7CTWFpbGZ >> sb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0% >> 3D%7C3000%7C%7C%7C&sdata=TFj1jTETd5iX3h7J8%2B%2FNc3usPgZFo8N4E7lrAShU >> fhU%3D&reserved=0 > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://list/ > s.sourceforge.net%2Flists%2Flistinfo%2Femc-users&data=05%7C01%7Ctoddz% > 40pgrahamdunn.com%7Cab74bf847dbf4526bf1508db7ec2a17c%7C5758544c573f47c > ebee96c3e0806fb43%7C0%7C0%7C638243146663401436%7CUnknown%7CTWFpbGZsb3d > 8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C > 3000%7C%7C%7C&sdata=TFj1jTETd5iX3h7J8%2B%2FNc3usPgZFo8N4E7lrAShUfhU%3D > &reserved=0 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
