Following sequence and bypassing parts of it...best practices ???

[darkesha]

Hi, I have a series of subsystems as parts of one machine that runs product.
Transfer table (TT) moves product from one subsystem to another. TT has 6 positions until product moves from beginning to the end.

Now I want to put a PB on HMI which will start following flawed product on position 1 through whole sequence and bypass every subsystem until this product is out on exiting conveyor.

I did this the only way I could think off but I believe there is got to be better practice which I would like to learn. I think it would save me writing as many rungs and simplify troubleshooting and allow expandability. Its been 7 years since I finished college and in all this time I haven't used much of what PLC can do except pretty simple things which I make sure the least skilled maint. guy can figure out.

So the way I wrote bypass machin, I started with TT movement incrementing counter from 0 to 5. Every .acc value is turning a bit for certain substep. This bit is used elsewhere in program and will inhibit that subsystem.
After whole cycle counter resets itself and waits for another engagement.

I see potential problems with 2 or more product in a row not being able to be bypassed and for that I would have to double the whole thing...potentially writing it up to six times (which isn't big deal unless there is something more elegant solution).
Also potential problem would be bad good product (bypassed) and then another which is ok, followed by another bad product.

If someone did something like this and know what's the best way to do it please share.

Thanks for reading !

 

[Franky_B]

Hello,

If I understand correctly, the TT is like a turntable, having several positions which 'dock' to the substations and are processed simultaneously.

Are the positions on the table identifiable ?
With other words, can the system determine which TT-position is at which substation.
If so, you can connect a 'bypass' bit to each position, which is set if the TT pickes up the product (via the HMI).

If TT-positions are not identifiable, I suppose the only way is a bit-wise shift-register. This shift-register can cover all your sub-stations so only 1 is needed.

Kind regards.

Frank

 

[darkesha]

Hello,

If I understand correctly, the TT is like a turntable, having several positions which 'dock' to the substations and are processed simultaneously.

Are the positions on the table identifiable ?

No...TT (transfer table) is like turntable, in sense it always run 360 degrees and in every cycle it picks up 6 products off their positions and lands them on the next position. So after every cycle/circle it lands in home position and product was moved forward.

If TT-positions are not identifiable, I suppose the only way is a bit-wise shift-register. This shift-register can cover all your sub-stations so only 1 is needed.

Kind regards.

Frank

I haven't had much experience with BSL/BSR and FIFO instruction since I finished college, and even then we didn't spend much time on them.

I will have to see how they work again and hopefully I wont have much pitfalls with them.