I looked on the Wiki, and believe I could provide something that would be useful. I could include more information to give a more complete treatment of the time limiting factors of using stepper motors. I have a few questions to try to make it more informative, and since I've never posted to the Wiki I could use some advice.
1: Can I compose this offline using Open Office Writer, and transfer the final form to the Wiki? 2: Some tables would be helpful. How can I include tables in the Wiki? 3: I could use to include one or two plots from Switcher Cad (many thanks to the folks at LT). Can I include them as .jpg or .png? 4: Can you help me with the outline of what to put in there? Perhaps it could be called "What Limits a Stepper Motor's Speed in EMC2" 1: How inductance/voltage/current limits the max stepper motor speed and how torque drops as speed increases. 2: How the step/direction interface vs quadrature A/B interface affects performance along with how discrete speed changes as you approach max step rate can hurt performance. 3: How resonances can reduce the maximum speed. 4: How micro-stepping reduces torque from full step torque. Perhaps I could include a little discussion on how an axis getting behind during cutting might not affect the quality of the part (when the tool slows to take a corner, the axis can catch up). How most machining is done at low speeds where torque in a stepper system is good. Any suggestions of how to tweak this outline will be helpful. Thanks! On 12/19/2010 04:39 PM, [email protected] wrote: > On 12/18/2010 11:43 PM, cogoman wrote: > >> > On 12/18/2010 08:35 AM,[email protected] wrote: >> >>> >> I was wondering if u could tell me what this means: Setting PFD, >>> >> "Adjustable, >>> >> percent fast decay". The manual I got with my stepmaster stepper board >>> >> says >>> >> this should be adjusted for each axis. It doesn't say what it does or >>> >> how it >>> >> affects the operation of the stepping motors. Do u know what this is >>> >> and how >>> >> it would help me tweak the system? >>> >> >>> >> > With switching current regulation in a stepper driver, the current is >> > controlled by turning on the switch to one side of the coil connecting >> > it to the positive coil supply voltage, and connecting the other side to >> > the negative through the sense resistor. When the current reaches the SNIP: Leaving just enough to provide context. >> > milli-Henrys. At 12 volts even low inductance stepper motors can take >> > hundreds of micro-Seconds to achieve their rated full current. At 90 >> > Volts stepper motors with coils in the range of 2 to 3 mH can start to >> > tax the speed of EMC2s fast thread driving through the parallel port, >> > but even at 90 Volts a stepper motor with 12 mH coils will be slow to >> > respond, and at 12 volts a 12 mH coil will be terribly slow, OK for >> > tracking stars, but not for fast positioning. >> > >> > For (perhaps) more information than you ever wanted to know, search >> > for "Jones on stepping motors". A generous soul has given a great >> > tutorial on all aspects of stepping motor operation. >> > >> > Hi, Cogoman: > > Thanks for taking the time to compose this thoughtful response to Cathrine. > > IMHO the content of your message deserves a place on the LinuxCNC Wiki > (which currently considers stepper-motor inductance only from the > standpoint of maximum power supply voltage). > > Perhaps you would consider rewriting it into the "Stepper-specific info" > section of "Configuring EMC2" with an appropriate title. > > Regards, > Kent > ------------------------------------------------------------------------------ Learn how Oracle Real Application Clusters (RAC) One Node allows customers to consolidate database storage, standardize their database environment, and, should the need arise, upgrade to a full multi-node Oracle RAC database without downtime or disruption http://p.sf.net/sfu/oracle-sfdevnl _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
