The Motion Control Show, Episode 6: What Terminology do I Need to Know? (Types of Linear Mechanics)

We've been talking about a lot of different basic terminology.  Now we're going to talk about just some basic types of linear mechanics. I'm Corey foster of Valin Corporation.  Let's talk about some mechanics.

The first, most basic, one that we often times talk about is just a screw-driven actuator.  If you look here, it's a screw that can be turned by a motor and this nut moves up and down the screw as it rotates.  It is attached to a carriage, or a tabletop, on top of that and that's where you put the load so it's going to move back and forth as the screw turns.  But, it's supported by bearings, or linear guides, and then these bearings go on guide rails and the whole thing is held together by a base.  Pretty simple concept.  It might end up looking something like this: here's a finished product.  It has a cover over here so you can't see the screw, but you can see the screw here.  There are different types of screws.  There are lead screws.  There are ball screws.  But, here's the bearings and then there's a cover that can cover it all.  And then the motor gets attached to the end of the screw and that's what turns the screw which is what moves this carriage back and forth.

Here's a belt driven actuator.  This is looking down the end of it.  You can see the bearings here in the carriage or tabletop here.  Here are the bearings and then the base holding it together.  But, you can see there's a pulley here with a belt that wraps around it from the side that looks like this.  Here's a pulley here and a pulley here and the belt goes down around the pulleys and back.  And then this belt is attached to the carriage which moves it back and forth on the bearings.  Same actuator may look something like this.  Again, it's covered here on one end, but on this end you can see the belt.  You can see the belt on the bottom.  It goes down and around these pulleys here and here and the motor attaches at a right angle here.  

Linear motors.  Now a linear motor is the same concept as a rotary motor, but now the motor is just opened up.  You still have magnets.  You still have wires.  You still have current going through it.  Just the formation of those creates different types of linear motors.  This is an iron core motor where you have a forcer which is essentially the same thing as the carriage at this point.  The load is going to be bolted to the top of this forcer.  Then the forcer has the coils, or the copper wires, going around each part of it here.  Then the current is controlled through the copper wire and it changes how it moves based upon the magnets down here.  It has a flat iron plate to help increase that force.  Then this whole forcer moves back and forth.   So, it has to have bearings on that in order to support it just like a ball screw or a belt and pulley.  But the basics of the linear motor are there.

Then there's another kind which is ironless.  Which is now, rather than having iron in here, it's a bunch of copper coils.  Then the magnets are on either side of it and it's going through a U-channel here.  So, the magnets are both sides here of the U and the forcer is going through it like this.  And then on top is the carriage and that's where the the load can be mounted.  Now, this whole thing can be on its side of course and supported by bearings.  It has to be air gapped and all that correctly.

Lastly, another basic type is a rack and pinion.  The pinion is on the gearbox or the motor and then the rack here is on the bottom.  Now, in this case, either one can be fixed so the motor could be fixed and the rack could be moving up and down.  Or the rack could be fixed and the motor could be moved up and down.  

There we have it.  Those are the basic types of linear mechanics. I hope that helps!

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