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« on: October 23, 2010, 03:06:30 PM »
Rich, thanks for the help.
Using Version 3.042.020
Using CV
can't really tell about how much RPM loss but looks like about 30 RPM
Using VFD
Single Index
Don't know what spindle speed averaging checked is, can guess what it is but don't know where to find that option or if it should be used.
As far as the taper. Let's say I'm making .002 depth of cut per pass so it doesn't bog down the motor, I think Mach may set it's own depth of cut anyway even though this is what I have it set for in the threading wizards setting page, because it doesn't take that long to thread as it sounds with a .002" depth of cut per pass. Anyway, let's say I'm making 16 TPI threads on 4" stock. First pass will be 3.996", next pass will be 3.992, then 3.988, by this time (with the old motor) it will start to loose RPMs and instead of the next pass being at a depth of 3.984", it will start at 3.984" and go down to something like 3.9645" tapering down the run and continue if I let it. I can't really tell what the exact end depth is on X as I'm just looking at the DRO on Mach and it's moving counting down as it moves. The beginning of the thread is larger in diameter and the back end is smaller. It happens after it makes a normal pass where it starts to loose RPMs, then the next pass is tapered and it continues.
@ Himy, I can't go slower even geared down motor with a VFD if I go to 100 RPM the motor will be very weak. I assume Himy, that you have a CNC lathe that you can actually gear down to 100 RPM? I usually don't have a problem at 500-700 RPM. I was trying 1000 RPM because my motor lowered to 500 RPM was losing RPMS during threading, but last night I changed to my 2 HP motor with gearing so the highest RPM I can get is 742 rpm, so that will give me full HP at that RPM.
@ Hood, thanks also, I'll try lower speed with the motor, with the old motor back in, if it continues to work I'll put a different pulley on it to make it's top speed 350 RPM or so.