Linear motion

Dear Friends.



I need a linear movement, where I, by using my plc, can tell how far this movement shall be.



What is a cheap solution for this ?



I was earlier thinking of using a Smartmotor and attach it with some kind of linear motion, but this would cost me a fortune.



Is’nt it possible to make this motion control easier ?



Best regards



laura

What is the linear distance that you are attempting to travel? And what type of accuracy do you require?

Thank You.

The traveldistance is something like 8 inches (20 cm) or so.

The accuracy must be within +- 2mm or so.


laura

Hello Laura;

We've used these in some low-cost applications, they worked well; they use a 4-20 mA input signal to the PLC:
http://www.positek.com/p100.htm

or you could look at Temposonic sensor, more expensive but very accurate.

Hope this helps,
Daniel Chartier

Dear chartier.


It looks like it is only a sensor, You recommend.

Then what about the actuator and the controlling of the actuator ?

laura

I recommend a Robo Cylinder.

Be careful going Cheap, it may cost you dearly.
Good luck.

Laura,

You may use the linear sensor that Daniel proposed on many different types of actuator, from a gear-operated mechanical arm to an air-operated cylinder. There are also linear motors and motor-operated screw drives. That part is up to you. Only you can decide what you are able to design and buy. I gather from your previous posts that you are a student learning on your own with limited funds.

The actuator type depends totally on what you are going to do with it. Are you moving 3 ounces or 300 pounds? If it is a home project with a small load, then a toy DC motor and a rotary-to-linear gearbox would work. Buy a toy Lego set with the mechanical arm, and use the linear gear for your actuator. On the other hand if this is an industrial job, you need industrial equipment. You did not tell us what it is for, so our suggestions will be only as good as your description of the problem.

If you have a compressed air supply or a small air compressor, then the air-operated cylinder ram would be a good choice. With careful selection of the cylinder size and stroke length, you could probably get a 2 mm accuracy over an 8-inch distance for many different load levels.

I have used DT-500 laser measurement sensor from Sick Optics. Around $1400.00. You can get it in 4 to 20 miliamp or RS 422 format. In RS422 it will give you the distance in Meters. Its accurate to + - 2mm. Good upto a distace of 20 Meters.

Thank You.

Lancie1 can You please explain the air-operated cylinder ?

I have bought myself a plc for about 2000$, and have limited funds. This is kind of a hobby for me.

I want to lift objects up to 10 pounds with this "lineaer motioned" device.

This linear motion is all very new to me, and therefor I am glad for all the help You give me.


laura

PLZ anyone ??



laura

Linear motion just means motion in a straight line,
As opposed to rotational motion like a motor.
You can convert rotational motion into linear motion using by using a rack and pinion for example.
An air cylinder is just one of many ways to get linear motion.
Put Air cylinders in the Find search box on McMaster-Carr website. There is some good info there.
Hope this helps.
Good luck

Dear gbradley.

Thank You again.

It's just that, this is all very new to me.

As I understand, dc-motors are very difficult controlling, so I actually did'nt want to use them for this application.

Then I was thinking of stepmotors, where I also would change the rotary movement to linear movement, but for the stepmotors, I need controllers, drivers etc. so this would not be cheap.

Then I was thinking of the Smartmotors from Animatics, but they are actually quite expensive.

Then the thought hit me....... that I maybe could find some cylinders, that I can control directly, without changing from rotary to linear, and without buying alot of extra products such as controllers, drivers and others.

I am totally blank about these cylinders, and I hope You, or anyone else, can give me more information.

laura

I agree with Lancie

Lancie1 said:

If you have a compressed air supply or a small air compressor, then the air-operated cylinder ram would be a good choice. With careful selection of the cylinder size and stroke length, you could probably get a 2 mm accuracy over an 8-inch distance for many different load levels.

Click to expand...

Have you clicked on the McMaster Carr link?

Laura,

Don't take this the wrong way, but you don't sound like you have a whole lot of automation experience, right?

What I'd suggest you do is tell us EXACTLY what you want to do, with as much detail as possible. Tell us what you are moving, why you are moving it, where it needs to go, how long it has to get there, and why it needs to be automated. There are a ton of people here who have a lot of experience in machine design, etc... Given enough information for what you want to do, we should be able to come up with something to fit your needs perfectly.

Laura,

Sorry, I have been working some and have not checked here recently.

I see now that you want to move 10 pounds for a distance of 8 inches. You have received good advice from Tom and GBradley opn the air cylinders. Air-operated cylinders are available in a wide range of stroke lengths, diameters, and pressure ratings. The proper cylinder size depends on the inertia and resistance of the load to be moved, how far to move it, and the pressure of the available air supply.

If you have to move 10 pounds exactly 8 inches, and you have a 50 PSI air supply, then buy a 1"-diameter cylinder with 8-inch stroke length (F = Pi x R^2 x PSI) = 39 pounds total lifting force). You may want some type of adjustable arm on the end to fine tune the exact travel distance to within 2 mm. Once adjusted the cylinder will travel the same distance each time you apply air pressure. If no standard length will work for your job, then you may try stopping the cylinder before it reaches the end of travel. Use a 3-way solenoid valve in the air line to start, stop, and reverse the cylinder movement. You PLC can control the solenoid valve.

For experimental and learning purposes, you may want a longer cylinder that will have more travel distance and more travel time. You could get a 24" long stroke length and then experiment with stopping it at different points.

You may attach a linear motion sensor to the cylinder (or to the load) to detect the analog position, or you may buy a cylinder with magnetic proximity switches built into the cylinder to detect the begin and end points (also to stop the cylinder at some point by shutting off the air valve), or you may use external adjustable limit switches for the same purpose.