Build Thread- Converting from steppers to servos?!

[m1911bldr]

I have a stepper-driven 3-axis machine using 305 oz-in steppers and Mach 3. It runs relatively well but loses steps and stalls unpredictably. I'm trying to use it for production and the intermittent stepper issues are unacceptably unreliable. Anyone have a suggestion for a "turn-key" servo upgrade? I don't need more power or speed, just better dependability. Suggestions on appropriately sized motors and drives would be appreciated.

[stevespo]

What are you using for stepper drivers, power supply, etc?
How fast are you cutting, what material?
What is are you using for linear rails and screws?

Closed loop servos will give you the dependability you're looking for, but you may also gain a performance boost with a very modest change to your stepper setup.

I'd eventually like to find an affordable servo upgrade, but for the time being I'm getting very good performance from my steppers with a beefy power supply and a faster (used) PC.

Steve

[m1911bldr]

My controller is Hobby CNC's 4-channel board. The steppers are their 305 oz-in NEMA 23's. I'm using 16 mm round linear rails and bearings. I cut mostly wood at 40 IPM with 60 IPM jog rapids but the missed steps and stalling occur only on the X axis and even when I'm not cutting anything. My machine is a little different than most. I'm using 2 motors on the X axis, running in synch, with the idea of eliminating racking of the Y carriage. When the machine isn't acting up it runs flawlessly. I have added dampers to the X motors and that halped some. I have also added a timing belt between them and that also helped. I've aligned, checked and lubed everything with extremem care and, as I said, the machind runs flawlessly most of the time. When it does start to act up, I have had no luck finding the exact reason why. My idea is to upgrade to appropriately sized servos with feedback and get 100% reliablitiy. I'm pretty sure it's not a resonance problem since most of the missed steps occur at the beginning of moves.

[jalessi]

M1911bldr,

What is the tpi of your screws?

Are they acme?

Jeff...

[imserv]

Originally Posted by m1911bldr Anyone have a suggestion for a "turn-key" servo upgrade? I don't need more power or speed, just better dependability. Suggestions on appropriately sized motors and drives would be appreciated.

This system will provide a closed loop capability with approximately
the same holding force, much higher accel rates and top end speed.
Motors bolt onto NEMA23 pattern.

SYS-4B servo system for parallel port

Fred Smith - IMService
http://www.imsrv.com

[amplexus]

What is the inductance of your motors and what is the power supply voltage and current. Also are the motors resonating when you lose steps? I suspect you can tweak your setup and fix the problem without going to the expense of servo's, encoders, a new drive etc. well designed stepper systems seldom lose steps.
Amplexus