Re: [CAD_CAM_EDM_DRO] Bridgeport retrofit servo questions

Hi Brady,

I really would not recommend using the steppers. I could never trust my
mill not to lose steps at some point. Maybe it was a problem with my
setup but once I changed to servos the machine performed so much better.

1) 10-1573 - This is the one I use. It needs at least 2:1 reduction. The motor build quality isn't brilliant but the flange on the front makes mounting fairly easy. They need some form of enclosure on the back to keep swarf etc out.

2) 10-1783/10-1783 - As far as I can tell they is pretty much the same as 10-1573. They have increased the supply voltage and revs to get more power but at a reduced duty cycle. It is quite likely that the windings are pretty much the same.

3) 10-1906 - Fully enclosed which is nice. This is a fairly square motor so the rotor inertia is probably quite high. This may affect your acceleration. It should have more than enough torque for 1:1 gearing. This reduces the rotor speed which reduces the effect of inertia. May be a tight squeeze on the Y axis. If I remember correctly the original motors have a 5/8 shaft so you probably wouldn't have to buy new pulleys. With a 75V supply the motor will have a top speed of about 1700RPM giving a max theoretical rapid speed of 340IPM :-0. With 1:1 drive a 200 line encoder is pretty marginal. You really need something like 500 lines or more.

4) 10-1723 - not fully enclosed but it looks like it could be enclosed with the addition of a couple of steel bands. Long and thin is good because it keeps rotor inertia down, however it won't fit on the Y axis. Again it should have plenty of torque for 1:1.

As far as drives are concerned it is difficult to choose between Rutex and Gecko. I tried both on my mill and with a 200 line encoder the Rutex drives could be tuned to be considerably 'stiffer' than the Geckos. Increasing the encoder line count is a good way of increasing stiffness. The high following error trip limit on the Rutex drives is nice if you are pushing the acceleration to the limit but it does mean that if something goes wrong the motors will move quite a long way before the drives trip.

If you are running higher resolution encoders you may need to use step
multiplication to get good rapids. I have to say I prefer the way Rutex
drives do the step multiplication. Geckos use a phase locked loop system
which can theoretically lose steps if you reverse the direction shortly
after issuing a step pulse. In practise I haven't heard of people having
problems but as an electronics designer it just makes me a bit nervous.
Rutex drives to the multiplication in software which cannot lose steps.

Geckos have two big advantages over Rutex. They are cheaper and they are
easier to wire up. I really like the nice simple screw terminal block on
the Geckos compared to the slightly awkward D connectors or ribbon cable
connectors used for the signals on Rutex drives.

In the end I used Geckos on my mill because I had a set of 3 and it was
easy to fit them in place of the G201 stepper drives that I originally
fitted. They were actually bought for another job but that job is on
hold for the time being. The wiring in my mill is not the tidiest and I
may well redo it at some point, in which case I may well go for Rutex.

Les