Not really sure how to ask this but if you are using Mach and a smooth stepper, are you running your machine at the maximum speed it is capable of or did you manually limit the speed since the smooth stepper allowed it to travel too fast to feel safe?

Here's the reason I ask the question:

I'm getting ready to bring an old CNC veritcal milling machine up to current technology and have a question about servo drives. The Supermax YCM-40 currently has servo drives model SEM 30M4-59, 2400 rpm, 142 volts, 30 pulse amps. I've read on a forum that these use around 10A continuous.

In my research I've found that some Viper 200 servo drives would work with this setup (rated at 170V, 20A) however carry a heavy price tag of $240 each.

Gecko 320's are rated at 80V, 20A and are only $119 each. I think I understand that the Gecko's would work however my max speed would be reduced. Is this the only downside?

I've noticed in a lot of posts that when people switch to a smooth stepper board they could get very quick rapid speeds however backed them down for safety concerns. So it seems that quite a few people don't use their max speed anyway?

I'm just curious how slow the machine would be setup like this or if it would only be noticed in a production environment where every second counts?

Thanks for any feedback...

My machine will do 400 IPM on X and Y, but I limit Mach to 200 IPM.  400 is just too scary - that's about 6 seconds for my 49" table to run stop-to-stop.  Doesn't leave much reaction time if something goes wrong.  And there's little benefit to those kinds of speeds anyway, other than bragging rights.  At some point, I'd like to change out the reduction pulleys, and go from 2.5:1 to 4.8:1, just to bring to max speed down, so I can use more of the available motor speed range.

Regards,
Ray L.

I've read that on many build threads on a couple forums and was curious just how many people have reduced their max speed for this reason.  If my max speed is really not feasible or doesn't leave much reaction time, then I would feel confortable going with the smaller rated drives on my retrofit.

My Lathe had 5m/min rapids when Churchill made it, I now have it running 10m/min but have had it as high as 20m/min. Reason I slowed it down is its scary seeing the 400Kg saddle hurtling up towards the chuck at 20m/min and secondly as the machine was originally only 5M/min I think double the rapids is fast enough and hopefully will not wear things out where 20m/min would I think.

With the Geckos you should reckon on about 1300rpm from your motors, with 1:1 gearing that would give you (assuming 0.2 lead screws)  260IPM approx. What was the original rapids on the machine? You may well find that the original drives only put out around 90v to the motors.
Hood