Create a rotatory control system

[DavidLee]

For increase the efficiency of check barcode tape , we need to construct a motion control
system . There should be two reel , one is used to load barcode tape not checked (source),
and the other is used to load barcode tape that is check passed(target) . So when the
system running , the diameter of source tape reel will be litter and litter , and the target
reel's diameter will be bigger and bigger . Once there is an error of a barcode label is found,
the motor should stop immediately , so that one can rip off the improper barcode label , and then
continued the check process . Please advise me , to construct such a motion control system ,
what components must be prepared ? Are there any othere important thing need to be considered ?

Your advise is highly appreciated.

[mhaag]

David,

From your description it sounds like you are putting together a complete machine vision and motion system that will both inspect barcodes and control the movement of the reels. From this description, the simplest setup would probably involve a single motor that would be geared to rotate both reels at the same speed, and therefore stop/start motion simultaneously as well. To do this, I would one of our motion controller boards (such as the 7344 or 7358) that would allow you to easily program and manipulate the motors being used. These boards would also allow you to synchronize with our IMAQ Frame Grabbers boards so that you can control the motor based on the results of your vision tests.

Information on our motion and vision products can be found at the fo
llowing websites:

Machine Vision
Motion Controllers and Drives

If you have more detailed questions then please let us know, and also feel free to speak with one of our technical sales representatives to help you with any other decisions you may have.

[Brian_Beal]

You don't want the reels to rotate at the same speed. As the diameter of the reels change, the a tangential velocity will change for a given RPM.

You would be better off to either have a drag brake on the feeding reel, or have a tension sensor that controls the speed of the feeding reel.

[DavidLee]

Hi Brain,

Could you advise me the detail of using tesion sensor?

David

[Buechsenschuetz]

First you have to evaluate whether you need feeding the labels with constant speed, with constant drag (i.e. with constant force applied to the label tape) or both.

There are several possible approaches towards feeding the tape with constant speed. One would be using a friction roller with a speed sensor such as an incremental encoder and use this encoder as feedback source for the target reel drive.

For constant drag control you can use a similar roller but it does not have to have good friction with the tape - it is simply used to reduce friction between the tape and the arm the roller is riding on. You can detect angular position of the arm, or - in case you use a more or less flexible arm - a strain gauge to detect the load on the ro
ller arm.

However, I think your problem is not related to motion control only, I think there is quite a bit of mechanical engineering and general metrology involved, too. In case you don't have the background to solve such problems you can look for a consultant or contract engineer to design the system you need.

[Brian_Beal]

For your described system, you would probably be better off using a capstan drive to feed the tape. This is the same design that is in a cassette player. The tape is pulled between 2 rollers at a constant speed(or variable if you like). The take off reel provides drag. This could be a simple friction brake, or a magnetic clutch. Depending on how big your reels are, and how much tension your tape can handle,the friction may need to be adjusted as the reel changes sizes. Magpower and Warner both make clutches like this, and controls for them.

The take up reel would have a similar system that would provide just enough pulling force to wind the tape on the reel. Again, a magnetic clutch may be the easiest solution. A motor would be conn
ected to the clutch, and would turn at a constant speed.

There are other methods, including servo motors controlled by tension sensors(dancers are the simplest), but I don't think you need that.

This constant linear velocity design would probably be best for you vision system. Assuming that the barcodes are evenly spaced, you could have an optical sensor sense the barcode and trigger the camera for an inspection. The constant linear speed makes it easier since you don't have to worry about timing issues once things are set up.

These are all standard web handling methods. The same things are used in the wire industry. Do some Internet searches on those subjects for some more ideas.

Given all that, you probably don't need a motion controller.