On Tue, 30 Apr 2013 12:25:05 -0400, you wrote: >On Tuesday 30 April 2013 12:06:13 Cecil Thomas did opine: > >> Gene, >> You need to remember that the seemingly high hp ratings of these >> relatively small motors is due to the very high rpms at which the >> ratings are valid. >> These 1 1/2 to 2 hp motors develop that hp at 5000 to 6000 rpm. You >> will have to rethink your drive coupling system to reduce that speed >> down to something usable especially for threading. > >I am aware of that, the toothed belt pulleys stock on the 7x means its >turning about 8000 revs to get the 2500 rated in high back gear. I very >rarely use it as there isn't enough torque to even cut alu 1/2" in >diameter.
Gene I'm running a no name "US made" treadmill motor as a spindle motor on an SX3 mill, it says on the label 2.75 HP, 180VDC, Rated speed is 5700rpm. The brushes are 180 degreed to the armature and the motor casing, despite this it's 1000 rpm down in "reverse" to it's normal 5700 rpm. at 180V. It has 12 windings on the armature. It's "coggy" at less than 500 motor rpm. It's had an encoder fitted and I tried as a servo and failed. It generates a lot of heat and has to be fan cooled. But it's lasted pretty well. It's done thousands of hours, had three sets of brushes and it's due for it's third set of bearings when I get around to it. Works OK in it's present use linked to a KBIC-225 speed controller with a 2:1 reduction to the spindle and it's got bags of torque at anything over 1000 rpm at the motor. I've got the largest plug in horsepower resistor fitted so controller's good to 16A at 180VDC. The max load I've ever seen is 9A and I had to back off the feedrate as the machine was struggling and complaining, but the spindle never dropped more than 20rpm from the 2000 I'd set. I was running a 15mm end mill at the time in AL and it got into some sort of resonant vibration - thought it was going to bust something but it didn't. I like the KB SCR drives - they are pretty linear speed wise and easy to interface using an isolated PWM to Voltage adapter. The IR compensation works pretty good too if set correctly, little or no speed change under load to free running. And most importantly they are inexpensive! Steve Blackmore -- ------------------------------------------------------------------------------ Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET Get 100% visibility into your production application - at no cost. Code-level diagnostics for performance bottlenecks with <2% overhead Download for free and get started troubleshooting in minutes. http://p.sf.net/sfu/appdyn_d2d_ap1 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
