[mackeym]

I have 3 AC servo motors and drives (2 that are nema 34 and 1 that is nema 42) that I thought would be relatively easy to put on the shopmaster in place of the stepper motors. Below are pics of the motors the faceplates and the drives. The motors are Pacific Scientific; 2 with resolver feedback and one with encoder and hall signals. The drives are Pacific Scientific SC903 and SC904 with OC930 and OC950 option cards, respectively, and one is Kollemorgen Servostar CD. I also have a 3-phase power filter, which i'm going to use to filter the single phase 240 V AC. Although the filter is for 3-phase, I called the manufacturer and they said it will also work almost as good for 240V AC single phase. The first step will be to power-up the drives and motors to see if they still work (I haven't turned them on in about 5 years). I have some SSR's i plan to use as a switch for the 240 V power into the filter, and I need to use some switches to enable/disable the drives. I'm going to put the power switch and enable switches in a homemade wooden box. Then tune the motors with no load. I found all the manuals and software for the motors and drives on the Kollemorgan website. I'm not completely decided yet if i'm going to use the tuning from no load. One of the manuals said that if you have backlash the motors should be tuned with no load. My shopmaster seems to have a 2-3 thou backlash in each acis. I'm open to advice on this one.

The nema 34 motors should be a direct (or close to it) swap (since the steppers are also nema 34). The nema 42 motor will need a new mount, timing pulley, and belt (going to order from mcmaster). I'm using the nema 42 for the x axis, the next smaller motor for the y-axis and the smallest motor for the z-axis. For safety (since runaway can happen with AC servos), I'm going to use two latching switches that can be positioned anywhere on each axis that when pressed will either cut the drive power or disable the enable pins. Anyone know which is better to use? I would think that disabling the enabling pins would be better because the motors should stop quite fast as opposed to cutting the drive power which may allow the motors to keep going for longer because the drive may store power in capacitors etc.

After I finish the conversion and if all goes well I might try something. This something is to use the glass scale DRO output as a position feedback on the z-axis Servostar CD drive and the motor encoder/hall as velocity/torque feedback for a dual loop to maximize accuracy with the parts/pieces that I currently have. This is possible with the z-axis (small motor and servostar drive) since this drive has an optional encoder input for just this. The manual said the it's preferable to have zero backlash for this though. So we'll see. I don't want to get ahead of myself, but I also have a brand new zero backlash ground C3 ballscrew (ebay find...actually I have 2 of these) I could maybe resolve the backlash on the z-axis rolled ballscrew.

All the motors and drives I got from ebay for a previous project; they all seem to be in good shape. The nema 42 motor I know is a little overkill, but it'll fit if I make a new faceplate (i'm going to change the pulley ratio on this one to 1:1). I'll post updates and pics as I make progress and hope to hear any feedback (good/bad, advice, recommendations, questions, or whatever) from fellow shoptask (or not) folks. This is exciting for me and I hope you enjoy following along.