Hi We operate a retrofitted pfauter hobbing machine at work. I could not get rid of the unwind problem but managed to devise a workaround.
This is a servo system with feedback and PID. I first used the encoder-ratio component that is included in the standard iso. With a first job after homing, this setup functions without error. The problems come when the next job is set with a different tooth count. If memory serves me right, with a non-zero spindle encoder count, simply disabling the encoder ratio component results in a massive f-error on the c-axis. Similar happens when setting a new ratio for a different tooth count on the job. I am keen to help wherever I can in improving this functionality, even if it is just testing. IMO, we would be better off commanding the c-axis position somehow than intercepting the encoder feedback and adding a factored value dependent on the job. F-error monitoring and doing a controlled stop when problems arise is a must. I destroyed a few hobs and jobs costing a couple of thousand $. When things go wrong during hobbing it is a major crash when all motion stops. I tried implimenting f-error monitoring but was not successful. Probably didn't spend enough time on this. Happy to contribute wherever I can. Henk On Fri, 15 Nov 2019, 14:09 , <[email protected]> wrote: > Send Emc-users mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > https://lists.sourceforge.net/lists/listinfo/emc-users > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Emc-users digest..." > > > Today's Topics: > > 1. How to Hob (andy pugh) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Fri, 15 Nov 2019 11:01:07 +0000 > From: andy pugh <[email protected]> > To: "Enhanced Machine Controller (EMC)" > <[email protected]> > Subject: [Emc-users] How to Hob > Message-ID: > < > can1+yzudrmnpvy+d2fy043-z2noh3m-byotco_pkjmputgo...@mail.gmail.com> > Content-Type: text/plain; charset="UTF-8" > > Some time ago I realised that a spindle encoder allows LinuxCNC to do > gear-hobbing. (And I made a video which now has 200,000 views, so > there is clearly some interest in the subject) > > At that time I linked the output of some HAL logic direct to the > stepgen of the rotary axis. > In a later iteration I made a HAL component that handles a change in > tooth-count without trying to instantly rewind to the new target. > > I have had an enquiry about helping to set up a hob for someone else, > and I am wondering how one would do it now. > > It could clearly be built into a kinematics module. Would that make > sense? I am not sure. > We now have "External Offsets". I can definitely see a good argument > for feeding the synched offset in via an external offset rather than > just adding numbers in HAL. Though one advantage of the current method > is that I can flash an LED to suggest the F-error is nut under control > (so slow the spindle) rather than stop all motion and _completely_ > ruin the part. > But then using ext-offsets doesn't specifically preclude monitoring > f-error. > > Thoughts. > > -- > 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, 1916 > > > > ------------------------------ > > > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > > > ------------------------------ > > End of Emc-users Digest, Vol 163, Issue 24 > ****************************************** > _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
