Bright Ideas

I am recently joining this forum but I have been using this site more than two years when there were no Q/A forum. I am just new in this field . I bought last year "Your Personal PLC Tutor - A Guide to Understanding PLCs" written by Phil Melore through internet. And I found the book very useful for beginners,for basic understanding. Then I joined a school in Toronto and learned PLC2,PLC5 and SLC500 and did practice on free software(Trial) of AB and leaned a lot through "Learning pit".
I am working in a co. on probation period. This co. welcomes "Bright Ideas" from emplyes. We are using AB plcs. Machines, we use, make a punch or embosing (say 2 inches of width) on a steel belt at different lengths then cut this belt from center of punched area so the pieces comes out of required lengths punched at both ends half of the width i.e. 1 inch each sides. I want to get a solution to use a kind of sensor or detector to read this punched area(corrugated)adjustable form 1/2" to 2" to read and send a signal to PLC to cut in the middle of the punched area (tolerence +/- 2.0 mm or less)I want to know,
1. which command( Basic/Compare/Math or any other command) should be used to achieve this accuracy.
2. which type of sensor or detector to be used to read corrugated area only not plane area
Thanks
Shams

Shams,

From your description, I envision the figure below where the Yellow is the final product.



Is this so?

Your description indicates that this system use two Presses; a Punch-Press followed by a Shear-Press.

Unless you have a "Flying-Punch" (moves with the material for a short distance as it punches, then returns to the Home position), I assume that the material moves through the process in increments.

(There's also the kind of Press where the Punch and Shear are in the same device. The Punching/Shearing action produced by a rolling tool-head, supported by a rolling die under the material. Of course this type is more suitable for fixed-lengths.)

How is that move accomplished? Some sort of Indexer? Pinch-Roller? What? How does the process know that it is time to punch or shear?

In order to solve a problem like this, the "right questions" have to be asked. However, we are subject to your description! As it stands, we don't know enough about your system to ask the right questions.

A half-dozen guys could jump in with a half-dozen suggestions... but, those suggestions would be based on guessing what you are really talking about!

You have to provide a better description... details count! In fact, in the control world, the details are everything!

Received via Private Message...

shams wrote on Today 11:16 AM:
Hi Terry!

You are very near to my question, the two punch indicates not a hole, but press with shear which is achieved by "Branson ultrasonic convertor" with high frequency of 20 khz and that the material moves through the process in increments and this move is accomplished by an indexer then stops for a while (say for two seconds) for the press, to embose on an corrugated envil with plastic tape which is running along with steel tape . The purpose of Branson convertor is to embose while pressing as wel as to weld the portion (steel and plastic tape) through very high frequency converted to mechanical energy by Piezo Electric Effect. This press (embossing) is done by flat horn of rectangular shape (say 20*40 Sq. mm).
Thanks for reply
Shams

Click to expand...

I'm even more confused. I feel like I have more information, but it seems not to match my original view.

Shams, are you making Measuring Tapes?

I can't help unless I understand the problem. And it's up to you to make the problem (situation) clear.

Anyone else see what's happening here?

C'mon Terry, that was supposed to be PRIVATE !

Sorry, but I pictured it the same way you did.

I'm familiar with Branson ultrasonic welders (welding plastic to plastic), so I think he's probably just welding the plastic tape to the steel tape.

From what I read, I think he's embossing and punching the steel tape (whatever shape) at one machine, producing a blank, then welding the plastic tape to this blank. Now he need to accurately locate (register) this blank when it gets welded.

Continue your description shams... We'll figure it out eventually!

-Eric

Attached you will see the sketch of the system that I asked for it?
I appologise for delay and also the sketch is not scaled.
Shams

Thanks for the drawing, for the most part it's the same as Terry's...

If the web is indexing, how do you plan to vary where the cut occurs? If you change the indexer's stop position, it directly affects the weld position. Do you plan to move the cutter's position relative to the web? Otherwise you'll need a dancer between the welder and cutter to allow a variable distance. In any case, I wouldn't use a photoeye... the cutter will be some fixed distance from the welder, which sounds like a good place for an encoder.

Let Terry have a crack at it... Maybe he'll figure out what I missed?...

beerchug

-Eric

Simple

Most motion controllers can do this easily. Motion controllers require an encoder to measure positions. The programming should not be an issue. Getting the motor, drive and encoder mounted, powered and wired correctly would take 99% of the time. At least for me.

The motion sequence would require two moves per cycle.

The key is that the emboss happens at the 0 position always. The knife position happens at the real knife position mod the difference between the emboss positions. If the knife position was 13 inches from the emboss position and the difference between the emboss positions is 12 inchess then the move to the knife position would be a move two one inch.

One could do this in a PLC but the performance would suffer compared to motion controller. The proper motion controller can even talk to you AB PLCs using Ethernet so you can change the distances rapidly from the PLC, HMI, PC.

Shams,

As Terry wrote :
"You have to provide a better description..."

We can see now what your final product looks like, but we can't suggest any solution or idea until you give explanations about the other parts and mechanical constraints of your machine (a motion pattern + timing would be useful).

Will your cutter act on-the-fly ? Is it, or can it be moveable ? Why do you plan to detect or measure the corrugated area, since the distance between two cuts is ever known (at least through the indexer's movement)? Your machine seems to be currently running. What kind of improvement do you attempt to do ? Does your post relate to sensors or to some retrofit project ?

"...details count !"

Shams,

The comments by Eric, Peter and Laurent indicate one thing...

Your description of how the process works is inadequate.

There's still something missing here!

I can see a few ways to impliment this system...

Method One:

• The welding head is fixed in position.
• The knife is fixed in position.
• The plastic, steel and fabric move together in steps.

Operation:

• Material begins feeding into the process.
• When the correct amount has been fed, feeding stops.
• Welder closes and knife cuts.
• When weld & cut are done, repeat process.

In this case, measurements are determined by feed-back from an encoder which indicates the amount of material that has been fed.

The other factor is the distance between the welder and the knife.

This method can produce very good results IF you can accurately control the feed and stop. And, if you do as Peter said, Reset the Welding point to zero on every cycle, you won't have an accumulating error.

The down-side is that material is always go/stop/go/stop. That can be tough on any system.

Method Two:
(Assuming the material is feeding from left to right, and that the welding head is above the anvil...)

• The welding head moves up/down in a counter-clockwise circular motion above the material.
• The anvil moves similarly in a clockwise circular motion below the material.
• The knife is a "flying knife".
• The plastic, steel and fabric move together constantly. The rate is determined by a pinch roller located between the welder and knife.
• The supply rolls have "drag" applied.
• The welder, pinch roller and knife are mechanically synchronized.

Operation:

• Material is constantly being pulled into the process by the Pinch Roller.
• The welding head and anvil come together every rotation. The welding head is spring-mounted so that contact is maintained for X-Degrees of rotation.
• While the welder is welding, a knife-clamp closes on the material, and the knife cuts while moving with the material.
• Process continues non-stop.

In this case, measurements are determined by the relative positions of the welder and knife.

Now...

I get the feeling that your process is somewhere between those two.
Can you describe it in a like manner?

I also get the feeling that you are trying to apply a correction at the end of the process - a problem which actually occurs earlier in the process. The problem should be addressed where it occurs - not down-line.