Lloyd:
OK, two months in and I don't have much to report. I've mostly been drilling small holes in plastic and that variable speed is soooo nice - no more melted plastic from running the bit too fast. I haven't had a reason to try drilling any big holes in anything yet but I'm sure that will help there also.
Lessons learned, a few come to mind immediately, in no particular order:
1) The Rpm indicator on my servo drive only displays to the nearest 100 Rpm. It's got a 4 digit display so you've got to wonder WHY? I know that this is displaying the actual motor speed and not the speed setpoint because I can slightly change the speed pot setting and hear the motor pitch change, but the display doesn't change. This isn't really a big deal though, as it's a WAYYYYY more better indicator than I had before - which was Nada. Any of these drives by a different manufacturer will probably be different, so you may - or may not - get an Rpm display.
2) The speed pot circuit in the Home Machinist link, referenced earlier in this thread, replaces the Hall Effect sensor speed controller and is a good starting point. You may want to do some experimenting with the resistors to the 1K pot. These resistors control the minimum and maximum voltage that the pot's wiper will sense. Mine currently goes to minimum speed at about 15-20% of the pot's travel instead of closer to 0% where I would like it. The same is true for the upper end, I get full speed at about 80-85% instead of 100% where it should be. I probably should decrease both of those resistors, but I decided that I'd already rebuilt that circuit enough times and that I could live with it - as is.
3) When I started trying to replace the Hall Effect sensor speed control with a speed pot I had assumed that this was a simple voltage divider circuit. I didn't bother to measure the current on any of the connections. I tried building a voltage divider circuit with the parts I had on hand and it didn't work. I was getting the correct voltages, but apparently my speed pot circuit was not able to supply enough current to drive the circuit within the servo. Moral of the story? Use a 1K pot - it works.
4) The Home Machinist circuit includes a Run/Stop switch which bypasses the speed pot setting and stops the motor. Be sure to switch the motor to Stop before turning off the servo drive, you'll get the "Pedal Error" fault if you don't. DAMHIK
5) I'm not sure about other servo drives, but mine came with a "Brake to Stop" feature and it sounds like most other drive are the same. The range of this setting was 0-5 and it defaulted to 1, I set mine to 0. This causes the drill to coast down to the minimum speed setting, THEN brake to a stop. It MIGHT be amusing to watch the drill chuck spin open or closed when the motor brakes to a sudden stop... But a lathe chuck, filled with a big honkin' hunk of steel, unthreading and spinning across the shop would be less than amusing.
6) I've got my minimum speed set to the drive's absolute minimum of 100 Rpm. It's a lot easier on the equipment to brake to a stop from 100 Rpm than it is to brake to a stop from 3000 Rpm. And we're talking about coming to a full stop within 50-100 milliseconds, it takes about 100-400 milliseconds to blink your eye. I think you might also be able to increase the braking time so that the servo would brake the motor to a stop a little more slowly. I might have to check into that and try it. My servo drive doesn't like running at 100 Rpm, the motor speed oscillates. It doesn't smooth out until about 300 Rpm, but I don't really RUN the drill at 100 Rpm unless I'm getting ready to shut it off.
Don
