need help

Thanks in advance for any help. I am a novice at plc programming. I am working on an assembly machine right now that is basically all air cylinders. I have two particular problems. One is I need one of the air cylinders to strike the same piece multiple times (Probably two or three times). The other more difficult problem is I have a six station indexing wheel. I am trying to make it so if a piece is missing I do not want the other stations to try to load pieces to something that is not there. I use fpwinpro software using ladder and function blocks to program.

Disclaimer, I have no knowledge of fpwinpro software.

bmtool said:

Thanks in advance for any help. I am a novice at plc programming. I am working on an assembly machine right now that is basically all air cylinders. I have two particular problems. One is I need one of the air cylinders to strike the same piece multiple times (Probably two or three times).

Click to expand...

Does the air cylinder that you want to "restrike" have any sensors to indicate position of stroke?

bmtool said:

The other more difficult problem is I have a six station indexing wheel. I am trying to make it so if a piece is missing I do not want the other stations to try to load pieces to something that is not there. I use fpwinpro software using ladder and function blocks to program.

Click to expand...

Are there any sensors to indicate the part is missing? And that the indexing wheel has moved? Does your software have a "shift register" instruction?

Yes all cylinders have front and back magnetic sensors. Also the software does have shift registers. That's what I was trying to use. I just can't seem to figure it out.

for the indexing wheel I have seen things similar that use a add/subtract system. where if piece A is present you add one, once the wheel indexes you subtract one. piece B present add one, wheel indexes, subtract one. then if the number ever goes above 1 or below two, something is missing or out of step.

just an idea.. but it would be easier if we had an idea of the I/O you have available.

I am using a panasonic fp-x 16k c14t plc with an expander. I have around six inputs left and about a dozen outputs. If that's what you mean by I/O. I am a tool and die maker by trade attempting to get what I design and build to run.

yeah, I/O is the inputs outputs, but what I really meant was what actual field devices do you have in your system?

Do you have a limit,photeye,prox (or anything like that) that will indicate that the wheel has turned?

do you have anything that tells you a part is in place? (maybe a photoeye that is blocked when the part is in place)

what is the criteria for the air cylinder to strike 3 times instead of only one?

Yes a plastic is is put on the wheel. Next station an electric eye sensor checks if it's there or not. The next station, a cylinder pushes a rubber cap on. Next station a cylinder will strike rubber cap multiple times to make sure it is seated all the way. Next station piece will be air ejected. Next station a sensor will make sure the piece left the wheel so there will be no chance of a double load of the plastic piece.

bmtool said:

Yes all cylinders have front and back magnetic sensors.

Click to expand...

For the "restrike" cylinder You will probably need a pair of recycling timers that stroke the cylinder. Depending on if the cylinder extension when restriking activates the end of stroke sensor they may be needed to "hold" the valve position before reversing. Then use a counter to count the strokes. I'm presuming this restriking is done on the part indexing wheel. If this is the case, the restrike counter needs to be satisfied before the wheel can index.

bmtool said:

Also the software does have shift registers. That's what I was trying to use. I just can't seem to figure it out.

Click to expand...

The shift register instruction normally has an input, clock pulse, and a reset. You normally set the input to on if the part is present. The clock pulse would be the indexing wheel moving to the next station. In many PLC shift registers they need to start the addressing at a bite or word boundry (multiples of 8 or 16).

The input would classically be a sensor that detects whether the part is present or not.

If you have a electronic copy of your manual perhaps you can copy and paste the text concerning the shift register.

do you build one part at a time start to finish or do you have many on the go. does the first slot refill as soon as it is indexed?

the first slot is refilled as soon as the wheel spins

Bitshift Functions (E_)SHR
109
Description SHR shifts a bit value by a defined number of positions (N) to the right and fills the
vacant positions with zeros.
the 4 most significant bits are filled up with zeros
3
bit
bit
DT0
15 . . 12 11 . . 8 7. .4 . . 0
DT0 0 0 0 0
15 . . 12 11 . . 8 7. .4 3 . . 0
source register (N = 4 bits)
target register
For the difference between the normal IEC function and the function with an enable
input, see page 24. You can find an example for the “function with enable” in the
Online Help.
Data type I/O Function
BOOL, WORD, DWORD 1st input input value
BOOL, WORD, DWORD 2nd input number of bits by which the input value is shifted to the
right
BOOL, WORD, DWORD output as input result
If the second input variable N (the number of bits to be shifted) is of the data
type DWORD, then only the lower 16 bits are taken into account.
Example In this example the function SHR is programmed in instruction list (IL).
In the POU header, all input and output variables are declared that are used for
programming this function.
This example uses variables. You may also use a constant for the input variable.
Body The value for source_register are shifted N (3) bits to the right. The resulting vacant
bits are filled with zeros. The result is written in target_register.
IL
(E_)SHR Shift bits to the right

From your first post

I do not want the other stations to try to load pieces to something that is not there.

Click to expand...

From your fourth post

Next station a sensor will make sure the piece left the wheel so there will be no chance of a double load of the plastic piece.

Click to expand...

It seems that this sensor, similar to the one in the second station but opposite in purpose, does exactly what you are looking for in your first post.

So it seems that your purpose is just to provide the multiple striking operation.

bmtool said:

Yes all cylinders have front and back magnetic sensors. Also the software does have shift registers. That's what I was trying to use. I just can't seem to figure it out.

Click to expand...

Are you trying to shift a bit or a word in the shift register.

Give us a screen shot of what you attempted that did not work .

Often it is easier to make a shift register work, if you shift the register from the higher number to the lower number, I know that might sound backwards, but it often avoids over writing data during the scan.

I cant be more specific as I don't know your PLC

Edit started typing before post 11

Bernie, There are four stations between the two sensors that I don't want to trigger as the blank station goes past. The last sensor is going to stop the machine in it's tracks if a part makes it past the air blow off. I'm hoping not to stop the machine if the first station misses a piece. But I will also want to stop it if there are say three pieces missing the first station in a row.

Gil47 I have the screen shot but i don't know how to post it on here. I doubt it would help you at all anyway. It's a function block that isn't right and I probably need someone who uses fpwinpro to be able to show me what to do here.