Seeking advice on what I need to provide motion control to a prototype 96 inch vinyl cutter. Cutting in a straight line and the ability to cut in the opposite direction. I'm planning on using Thomson lead screw/ball screw 1/2" dia. rod. The drag of the cutter is about 3 Lbs. What type of step motor should I consider? How do I find the appropriate drive sprocket for gears or a belt that will be the right size to attach to the step motor and Thomson rod? What do I need off the shelf for a controller and programing unit to program the motor to run a certain number of turns, pause and reverse it's polarity and return to it's start point? Any help would be greatly appreciated....Mike

 

Hello Mike,

If it makes sense to your mechanical system use a prepackaged ballscrew actuator from THK/NB/Parker/etc. They often come with linear guide rails ballscrew with end support bearings and a flange to mount the motor. I'm particularly fond of the THK precision ballscrews (SKR and KR series). NB's seem to be a less expensive knock off of these. Unless you are making hundreds of these things or need a strange mechanical layout it probably doesn't make sense to engineer your own here. Maybe they don't make actuators this long, but I'd check. At any rate I'd direct couple the motor to the ballscrew with a bellows coupling. Going through extra gearing or belting will make your application more difficult due to the added slop/spring in the system.

I'd use a servo motor. Unless you are REALLY strapped for cash it just doesn't make sense. For about $1k USD you should be able to buy something from Yaskawa or Mitsubishi that will interface to the ballscrew actuator directly and auto tune itself. Even an auto tuned servo is better than a stepper. The amps these days can be bought to take stepper style input if you need that. I don't know where you are, but our local distributor will sell us the actuator and motor/amp and help get it going as well. Do some homework and talk to your local vendors.

So basically ---> A good linear ballscrew actuator + bellows coupling + Properly sized servo = Happy Engineer. )

KEJR

 

My first thought is that a 1/2" dia ballscrew sounds too small for a 72" travel.  A stepper motor is very sensitive to non-linear loads, like a whipping ballscrew.  You might want to look at servo motors instead, even though they cost more.  I'm not saying a stepper won't work, but they are more difficult to apply.  You didn't mention anything about linear speed.

 Bill Sturm

 

Unless you need good positioning accuracy, which I don't think you do, you should consider a belt drive modular actuator. What kind of speeds and loads are you talking about? A belt will more than likely need a gearbox, but the ballscrew probably won't. Servo is usually better, but not always. Give us some more information: speeds, loads, does it have to interface to some other controller?

 

Unless positional accuracy is critical, the length of this application makes it a belt driven actuator. There are many off the shel belt driven actuators for a wide variety of speeds, loads and thrusts that can be almost as cost effective as building your own system with components.

Steppers are great for positioning but if this application requires dynamic performance, then Servos are the way to go.

Let me know if you need direction with belt drive sizing.