Rob, Let me clarify a bit. The application is for a coil winder on a non round form. The form will be directly attached to the motor shaft. I need to velocity modulate the speed of the A axis as it goes around corners in order to help maintain constant tension. The test setup I'm using is a stepper motor with a piece of tape on it to indicate position. There is no actual machine yet, I wanted to make sure this motion is possible before building anything. The only physical limiting factor at present is the motor inertia itself.
The problem is not that the hardware is loosing steps, but that EMC is causing following errors. The upper limit on how fast the A axis can turn should be the maximum rate the steps can be generated. In stepconfig, I can get the motor to move reliably at 2400 deg/sec. This equates to 144000 deg/min in the units EMC uses. Anything faster than about 25000 deg/min will cause EMC following errors. This is about 6X slower than stepconfig will spin the motor. I've tried setting the microstepping on the drive to different values so that there are a different number of steps per degree, but I still run into the same wall around 25000 deg/min. This implies that the problem is not in generating the steps, but somewhere deeper in EMC. This happens in both the G1 command, as well as manual jogging. They both cause following errors at about the same speed. Is it possible that numbers bigger than this are overflowing? Fred --- Rob Jansen <[EMAIL PROTECTED]> wrote: > Fred, > > as I understood the stepconf wizzard is a brand-new > feature in version 2.2.2 > I also have similar problems as you are seening with > the A-axis on XYZ axes: > > > Configuration in stepconf gives me reproducible > results, the machine is 1x2 > meters and the whole bridge (moving along X-axes) is > about 60 kilogramms. > Stepconf shows great results with speed = 60mm/s and > acceleration = 500 > mm/s2. > > What I have noticed is that the speeds that stepconf > shows during the test > are different from the ones seen in the axis > program. Axis uses faster steps > than stepconf, resulting in higher speeds (I still > have to measure the real > difference using the logic analyzer). > > And yes, this is a problem (for us) since we use > stepconf to validate our > movements. My settings mostly work but yesterday the > machine lost steps when > reversing directions so I have to lower my > acceleration and try again. > > Differences you see are however much higher that > mine. You tested in > stepconf with 6 revs/s and an acceleration of 66 > revs/s and you are noticing > problems in axis with speeds > 1.18 revs/s. > If you did not change the accelaration ramping down > at this speed takes > about 0.017 seconds ... A it too fast if you ask me > and you'll defenitely > loose steps if this is higher than your machine can > handle - independent of > the speed used. > > The way it is described in the manual: with low > acceleration determine max. > speed and then increase the acceleration. > I know this is a problem with stepconf given wrong > results and it will take > some time to get values that work in axis but I > think you should try to > decrease your acceleration first (try 2400 deg/s2) > and run your G1FxxxA360 / > A0 test at different speeds. If you are confident > that you have found a > proper speeds, only then start increasing the > accelaration. > > Then there is the question about your A-axis drive: > From your description it > looks like you are performing a direct drive with > the turn table connected > to the stepper motor. This will not work properly at > speeds (anything above > real slow). > And keep in mind that the A-axis is not a lathe. > I've translated your rotation speed into lineair > speed. 6 revs/s with a 10mm > round object equals to 10 x pi x 6 = 204 mm/s = > 12240 mm/minute (73 km/h) or > 1/2 inch => 1/2 x pi x 6 x 60 = 565 inch/min. > > Regards, > > Rob > > Quoting f m <[EMAIL PROTECTED]> <[EMAIL PROTECTED]>: > > Anyone have any ideas on this? I'm really stuck here > and would like to have a fix or a work around. > > Thanks, > > Fred > > > --- f m <[EMAIL PROTECTED]> <[EMAIL PROTECTED]> wrote: > > Hello, I'm having some problems with getting the A > axis on EMC working. Primarily following errors, but > there also appears to be a discrepancy in units > between the stepconfig wizard, (degrees/second) vs. > EMC (degrees/minute), and deceleration at the end of > a move. > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Microsoft > Defy all challenges. Microsoft(R) Visual Studio > 2008. > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/> _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
