1756-HYD02 to be used with a saw.

Peter Nachtwey said:
You didn't explain the speed limit of 123mm/s. Is that the line speed?
No, that´s cylinder speed i.e. saw speed to cut the pipe, carriage is another story , carriage speed is max 25 m/min that part is driven by same Controllogix PLC but thru a servo motor and inline encoder, that part is working properly.

http://www.iyeya.cn/thread-63637-1-1.html
Thanks for the link , I´ll take a closer look.

If hydraulic cylinder is for the saw, is precise positioning required? I know the M02AE position should be precise.
Well, I would say just to cut the pipe and then return, I´d say +/- 1 cm.

BTW, I have canned programs for flying cut off saws or shears.
http://deltamotion.com/peter/Videos/FlyingShear/SimpleFlyingShear.mp4
With a RMC you can test your program at your desk.
Yes. I have your software installed in my computer. No doubt i will do it.

I still don't like the valve.
Click to expand...
Me neither, BTW they already bought it. I do not know why i never recommnended to do it.

Sorry for the confusion, but finally all I talk about this time is only for saw.
As i said before, nowdays that saw is being driven by a bang bang valve, they use limit switches to indicate both ends of stroke. They have to move them every time they change pipe diameter, and they want to change that. They want to do it by software that´s the reason for a servo control.

I forgot to mention that maximun pipe OD diameter is 6" minimum OD 3", that means that maximum stroke would be aprox 8.5" and minimum 5.5" not 16", that is maximum stroke of cylinder.

If you need extra info or explanation, I´ll be here.

Regards,

William Delatorre (widelto)
 
they expect toNorman:

Thank you for your valuable comments, I will visit the plant very soon.
I will let you know if they have blocking valves, I would say, yes they have them because the saw has been working for four years with no problem.
As I mentioned before the saw is working with a bang bang valve and uses limit switches to control stroke.
They want to gain some seconds on every cut, and this way they expect to increase production.

Regards,

william
 
Last edited:
It sounds like you don't need very precise control on position with the saw.

I assume you are always sawing all the way through the part? Please confirm.

If you are always going all the way through the part and are not concerned with accuracy of position at the end of strokes, you can probably make the 4WRKE valve work. it will be harder than the 4WRLE valve I mentioned but it can be done. You'll need to program in the overlap and the tolerances on overlap are not that tight so it can be tricky.

If you have to stop the saw at precise locations or follow specific velocity profiles to optimize the cutting as you are sawing through the different cross sections of the pipe, you should get a different valve.

I would not assume that they already have blocking valves. The most common way to prevent a falling axis with bang bang valves is with a counterbalance valve. Again, you probably "can" make it work with a counterbalance valve but it becomes harder and if someone re-adjusts the counterbalance valve your tuning is affected.

Please keep us posted about what you find when you visit the site.
 
ndzied1 said:
It sounds like you don't need very precise control on position with the saw.

I assume you are always sawing all the way through the part? Please confirm.
Yes, that is correct.

If you are always going all the way through the part and are not concerned with accuracy of position at the end of strokes, you can probably make the 4WRKE valve work. it will be harder than the 4WRLE valve I mentioned but it can be done. You'll need to program in the overlap and the tolerances on overlap are not that tight so it can be tricky.

A:/ When saw finishes cut I need to retract it at once and as fast as possible. Remember that unit is a flying cutoff and saw is part of it.

If you have to stop the saw at precise locations or follow specific velocity profiles to optimize the cutting as you are sawing through the different cross sections of the pipe, you should get a different valve.

A:/ OK, when starting cut, saw must initially move fast very close to the pipe then cut a joint with a specific speed, when finishing cut saw must retract to home position as fast as possible , we are cutting steel pipes from 3 up to 6 inches OD diameter. I am with you I do not like that valve.

I would not assume that they already have blocking valves. The most common way to prevent a falling axis with bang bang valves is with a counterbalance valve. Again, you probably "can" make it work with a counterbalance valve but it becomes harder and if someone re-adjusts the counterbalance valve your tuning is affected.
A:/ OK.

Please keep us posted about what you find when you visit the site.
Click to expand...

@Norman: They sent me a hydraulic diagram I do not know if you took a look at it.

@Peter: I visited your web page looking for a canned solution at:
http://deltamotion.com/dloads/downloads.php?category=rmc70&subcategory=Examples
but found nothing
 
See attached file

@Peter:
@Norman:
All comments are in spanish, I hope you can translate them.
Otherwise let me translate them for you.
I hope it is clear enough.
I have not checked if diagram is correct, as I told you i have to go there very soon to discuss proposal.
 
widelto said:
@Peter:
@Norman:
All comments are in spanish, I hope you can translate them.
Otherwise let me translate them for you.
I hope it is clear enough.
I have not checked if diagram is correct, as I told you i have to go there very soon to discuss proposal.
Click to expand...

The diagram appears to be of the new design with the proportional valve with blocked center. There are no blocking or counterbalance valves included in the sketch.

The accumulator is good to have.
 
@Norman: They are using a bang bang valve, I know that for sure.
I was the one who designed and started the flying cutoff system, then a salesman appeared and made them to buy that valve, now they want to use it.
 
The hydraulic design is simple. My hydraulic calculator says the cylinder bore and rod diameters are plenty big enough for the load. It is probably bigger that I find necessary because I don't have a value for the load due to cutting the pipe but the stall force is big enough even with my calculations.

BTW, how big is the accumulator? It probably won't make that much difference since you aren't doing precision positioning.

My concern is the valve.
 
@Peter:
Accumulator is 9" OD 29" Height. I read your article about unsung heroes (accumulators).
As I told you the saw is nowadays working, so I was confident that cylinder dimensions were suitable.
Let me know your conclusions about the valve. Take your time.
 
Norm would be a better person to answer this question since he sells valves and has a catalog. Another thing that bothers me is that I calculate you need about a 227 LPM valve. Yet you stated above you are using about a 100 LPM valve now. That is probably because the pressure drop across the old valve is rated at 10 bar instead of 70 bar.
I know it won't be cheap because you probably will need to by a 250 LPM valve. Another trade off would be to increase the pressure. Then you may be able to get by with a smaller valve.
 

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