On Wed, 2011-03-02 at 21:41 -0600, Igor Chudov wrote: > On Wed, Mar 2, 2011 at 8:38 PM, Jon Elson <el...@pico-systems.com> wrote: > > > Igor Chudov wrote: > > > > > > I do think that the motor is underpowered for the axis, if I had to move > > the > > > axis continuously. However, if I only need to use it occasionally to > > adjust > > > for tool height changes, it is OK. > > > > > Right, I understand what you WANT to do, and it does make some sense, > > but EMC is not designed to operate an axis in this manner. You want to > > completely break the normal way of doing things. > > > What is the issue that you are pointing out, is that when the axis is "at > > > rest", it is not really at rest from EMC2's standpoint, and its pid just > > > keeps applying the same logic as during the moves. > > > > > Yes, exactly, that is the normal design for an axis. > > > So, if I can find some way around that, I will be golden. > > > > > I really think it is a bad idea, as the position will be uncontrolled > > when not moving. > > > > Jon, this is a ACME type screw that moves the knee, not a ballscrew. It is > 100% self locking.
But that is exactly why it takes more power to turn. IIRC acme's are about 10% efficient whereas ball screws are in the range of 90%. Some years ago I put a servo on the W of my cinci contourmaster. A gearhead motor with additional 3:1 timing belt. Max speed was about 10 ipm; no pneumatic boost. Motor was probably 300 W. Even then it finally smoked. Even at 10 ipm I could do contouring. I had no drive on the Z at the time so this had to do. ;-) Sometime I may get around to driving the z again to comp for tool length since I have less than 3" on the quill. The plan will be to use an adequate gear ratio to do the job, even if slowly since it is supposed to do tool length not contouring. Good luck on your conversion. Glad most of it is working. Dave > > > > > > > > > The better news is that based on limited post-change testing that I did > > (I > > > was very tired by then at midnight), these changed in P and I, do work > > > better as far as bringing the ppmc.0.DAC.03.value down after a while. > > > > > > The motor does succeed at getting f-error very low (think 0.00007), and > > the > > > output of the motor controller becomes several times lower than in the > > past. > > > It settles down kind of slowly, over several seconds. > > > > > > > > That is the I term working as it should, it keeps creeping until it > > finally nulls out the error. Well, the real question is does the motor > > still overheat? If not, you are done. Maybe strap a safety thermostat > > to the motor to cause an estop if some time in the future it does run > > hot again. > > > > I will keep an eye on the motor. I will post some updates. > > > > > I know that my drive is in torque mode (controls current), and the > > current > > > is about 10 times ppmc.0.DAC.03.value, per ammeter. So I can > > > watch ppmc.0.DAC.03.value and I will know what the current is. I am > > pretty > > > sure that the motor will not overheat from, say, 1 amp. > > > > > No, even a small motor should be OK. Assuming a rotten motor with 1 Ohm > > resistance, that will only dissipate one Watt with a 1 Amp idling > > current. Those crummy Ametek motors with 4 Ohm resistance would > > dissipate 16 W, which might still be in the safe area, but would get > > pretty warm. > > > > > I will double check everything, including the current, I hope that I will be > fine. > > I got your A/D converter today, thanks. > > i > > > > Jon > > > > > > ------------------------------------------------------------------------------ > > Free Software Download: Index, Search & Analyze Logs and other IT data in > > Real-Time with Splunk. Collect, index and harness all the fast moving IT > > data > > generated by your applications, servers and devices whether physical, > > virtual > > or in the cloud. Deliver compliance at lower cost and gain new business > > insights. http://p.sf.net/sfu/splunk-dev2dev > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > ------------------------------------------------------------------------------ > Free Software Download: Index, Search & Analyze Logs and other IT data in > Real-Time with Splunk. Collect, index and harness all the fast moving IT data > generated by your applications, servers and devices whether physical, virtual > or in the cloud. Deliver compliance at lower cost and gain new business > insights. http://p.sf.net/sfu/splunk-dev2dev > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Free Software Download: Index, Search & Analyze Logs and other IT data in Real-Time with Splunk. Collect, index and harness all the fast moving IT data generated by your applications, servers and devices whether physical, virtual or in the cloud. Deliver compliance at lower cost and gain new business insights. http://p.sf.net/sfu/splunk-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
