On 5/11/12, andy pugh <[email protected]> wrote: > On 11 May 2012 14:45, Jean <[email protected]> wrote: >> Hello, >> I'm new to linuxcnc. I want to port linuxcnc to ARM9(IMX257) . but >> when i test linuxcnc with a nc program on my ubuntu pc in simulation >> mode(configs/sim/axis_mm.ini, G64 P0.005, max_velocity is 200mm/s, >> max_acc is 1000m/s2), it is very slow compare to Power Automation >> CNC(PA8000, based on windows) with same max velocity and acceleration. >> PA8000 has looking-ahead with 200 blocks. >> I googled internet, someone said that linuxcnc G64 lookahead is only >> one segment 'deep' . Is it possible to increase more lookahead blocks? > > It is possible, and it might even happen, but it isn't trivial. > There was a recent change to the motion system (only in Master) that > allows different acceleration at each end of the block, and that > apparently can make a big difference.
It's really very exiciting and expected indeed! Thanks so much for your efforts! > > There is a general feeling that G-code which needs 200 blocks of > lookahead to run fast is bad G-code. But you can even agree with that, > and still have the G-code and need to run it. > >From techinique point, I completely agree with you . But many commercial CNC controllers have more looking ahead blocks and works really fast. Take PA8000 CNC as an example, if looking-ahead is disabled, when process same NC program using same max_acc and max_velocity, it's slower than LinuxCNC. But if enabled with looking-ahead ability by insert a Gcode(G09), PA8000 is much faster than LinuxCNC. PA8000 takes 8~9 minutes to complete my test NC if looking ahead is enabled(Max_velocity: 200mm/s, max acceleration: 1000mm/s2) LinuxCNC takes more than 20 minutes to finish this NC (Max_velocity: 200mm/s, max acceleration: 1000mm/s2) > There is discussion ongoing on a new motion planner structure that > will allow more lookahead, but it is not clear if it will happen. > > -- > atp > The idea that there is no such thing as objective truth is, quite simply, > wrong. > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > Emc-developers mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-developers > ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
