Linear Motors

[gerard]

Hi,
Just wondering if anyone has much experience with Linear Motors? I am going to use one for an application but I'm not sure whether I should use an electric or pneumatic motor. I want the more precise of the two. It's not 'nano' precise i'm looking for or anything like that. As I have no experience with this type of motor can anybody that has experience give me some information.

Thanks.

 

[philipb]

Hi Gerard,
I have some experience with linear motors,it depends on the application,do you need a lot of torque or
exact position?If you just need torque an electric unit is ok,they usualy have overtravel switches
inside which stops the motor going to its too far and jamming up.If you require exact positioning you will
have to buy a motor with an encoder fitted.

 

[gerard]

Hi,
Thanks for that. I will need exact positioning with low torque. The Linear Motor will have a pneumatic cylinder attached to it and when the Linear Motor is in position, the piston will come down. So, would you recommend an electric or pneumatic motor? is the motor you worked on DC driven?

 

[philipb]

The motors i worked on were 240volts three wire,two live inputs for the selection of direction and
a common,the linear part is done by a gearbox so they had lots of torque,so electric would be ok as its
easy to control.for exact positioning you can get an encoder mounted on the end or
somewhere on your cylinder to take out any backlash in the mechanics.You can also drive a digital display.
All the controls you need are in Radio spares,talk to there technical dept,they are very
helpfull.

 

[gerard]

What was giving the signal to the Linear Motor to operate? I will be giving it a signal from a PLC, which is getting it's signal from a vision system. It is my job to ensure the PLC side and the motor side is working.

 

[philipb]

The motor is switched by relays which are controlled by plc outputs.the 24volt plc output
switches the relay coils on and off.The encoder can be connected to a plc input pcb,you can then programme the
plc to display the position of the piston

 

[netblindpaul]

I have done design/applications and service engineering for a manufacturer of linear servo motor drive systems, and still do turnkey packages with the motor and attached linear bearings etc.
However, I only use one manuf' kit, my ex-employer and it is not cheap but it is quality kit from a global manufacturer and what could be considered in some ways to be a household name.

 

[pmac10]

have a look into stepper motors, sounds like it would suit your application as we use them in very similar circumstances to which you described, you would need a stepper motor controller coupled to a plc, normally i would give a much better explanation to how they work but its friday night and i'm half ****ed.

 

[netblindpaul]

Thing is pmac a conventional stepper motor is a rotary device not a linear device.
It depends on the application and how the mechanics are configured does it not.

 

[pmac10]

good point paul, i'm not on top of my game at the minute, and dont know the exact application, but a torque tube will convert a rotary device to linear.

 

[netblindpaul]

Never heard them called torque tubes before!
Not doubting you but what are you referring to?

 

[Knobhead]

Personally, I’d go for the bog standard electric linear motor, if you need an encoder they are readily available accessories. Pneumatic will not stop at a precise location due to residual pressure.

 

[pmac10]

Never heard them called torque tubes before!
Not doubting you but what are you referring to?

a torque tube is a mechanical device which converts rotary motion to linear, an engine crank shaft maybe, it rotates but is converting rotarty motion to linear, ie driving pistions up and down, irrelevant but i;m just trying to convince you i didn't make it up, ha ha!

 

[netblindpaul]

Like a ball screw or leadscrew & nut?

 

[pmac10]

Like a ball screw or leadscrew & nut?

no mate, they utilise thread forms, but would have been a much better idea for the op, while a torque tube relies on mechanical arrangement, a bad idea on my part anyway. I've encountered them in aerospace engineering and apparently they're used in automotive engineering also. There is no set design or spec for a torque tube, its just a name for a mechanical component which converts rotary to linear motion.
My original idea for a stepper motor, was for the motor to be mounted 90degrees from the direction of travel coupled to some form of drive. (and i dont know of any kind of torque tube that would be needed!)

 

[netblindpaul]

Aerospace is an area I have not worked, apart from on the machine tools they use!
Just not come across the term before.
I'll have to look it up.
I can't even remember the OP's problem now!!!