Traverse Rewinding

Having some problems getting the logic straight for a traverse winder application.
Basically we have steel that has been previously slit being pulled by a nip roller and a rewinder with a hydraulic traverse winding it up.
Steel thickness (.010" to .060") and material Width (.25" to 1 7/8") is entered along with traverse width (0-16")
Both Motors are AC Black Max controlled by ABB ACS 880 VFD.
Nip roller operating in speed and rewinder in Torque mode.

I think once the nip roller starts to operate the rewinder will go also since it is trying to maintain torque. My problem is with the traverse winding. We want a nice even wind and smooth sides to the roll.
If I know the material width + Gap factor (Since I don't think it will be zero) it will give me pitch per rev. The problem is that the traverse is hydraulic not a motor.
Been doing a ton of reading and think I am confused more. (Maybe I need more input from operator, like angle or to calculate my roll width divide it by material thickness to have a calculated gap? Use dwell timers to hold the web before changing direction in the traverse? But then the rewind speed is going to change as the web builds up, so the time may change.....ahhhhhhhhh!!!

I don't think you're going to be happy with the results using a hydraulic traverser for the reasons you have already discovered. This really is a servo application. If you get speed feedback from the nip and from the rewinder you can calculate roll diameter. This will let you determine your required traverser speed based on material width + gap.

Without good speed control and position feedback on your traverser, you won't get the level of control that you want.

Sorry.

--Joe

Both motors, (Rewinder and Nip roller) have encoders, and the Traverser has a Balluff micropulse LVDT rod sensor on it. The hydraulic traverser is also controlled by a servo valve.

If you have an LVDT for position feedback on the traverser and a servo valve, then it is *technically* possible to make it work. It will definitely offer a "unique challenge" for you!

Basically, you will have to determine (using the two roll encoders) how fast your traverser needs to move to properly lay the product. Then use the LVDT to calculate how fast your traverser is moving by taking multiple position readings over time, and adjust your servo valve to regulate the speed of the cylinder.

Ultimately you are closing the loop on the traverser with your code to set the desired speed of the cylinder. The LVDT should also let you know when you hit the end of travel so you know when to reverse direction.

Good Luck!

--Joe

It is easier if one uses a hydraulic motion controller built to do these applications. There is too much that needs to be written from scratch if you try to do this in a PLC let alone the PLC is probably not fast enough nor does it have a synchronous scan. I have a few customers that have been doing this for years.

Really??? Oh no... back when I was looking at this job I was told the hydraulic traverser wouldn't be an issue....

http://www.plctalk.net/qanda/showthread.php?t=84309

How are you positioning the traverse? what's the controller?
you have some block diagram?

The PLC is AB Compactlogix L33ER, with analog input and output modules.... Servo Valve is 4-20mA and Balluff rod is 0-10vdc

was doing some reading I think I might be able to use linear motion move command

Can you get a rotary position from the winder drive ?

I think so.. the rewinder motor has an encoder on it, as does the nip roller motor both connected to the compact logic controller (HSC card). Both motors controlled by ABB ACS 880 VFD

Been thinking about this...
Operator will enter Material Width, thickness, Reel Width, Line Speed (FPM) and Rewind Torque (%)
PLC will calculate the gap of each wrap.

The Rewind motor will need to control line speed based on the torque. (Torque is too high, then speed up nip roller).
The Traverse mixes everything up since it is a hydraulic controlled servo valve so speed is not adjustable (I don't think...)

Any thoughts...

Critt said:

Really??? Oh no... back when I was looking at this job I was told the hydraulic traverser wouldn't be an issue....

http://www.plctalk.net/qanda/showthread.php?t=84309

Click to expand...

I might not have seen that. If you get a real hydraulic motion controller that can synchronize or gear to an external encoder then it should be easy. My company has been designing and selling hydraulic motion controllers for over 30 years. You should look at
http://www.deltamotion.com/products/
or if you can use a ControLogix use a M02AS.

This is important. The feed back from your Balluff rod is analog. I DEFINITELY recommend against using analog because it is noisy and not as precise as SSI. I prefer SSI rods because the resolution can be as fine as 1 micron which is important when trying to control speeds that are slow. It is also important that the encoder you gear to have about 10000 PPR or higher. Resolution is important when gearing.

The motion profile you show must be executed as a function of the encoder. To do this you can use a spline or cam table and index into to the curve using the encoder position. EASY. Both our RMCs and the Rockwell M02AS with ControLogix can do this.

If you try to roll your own it can't possibly be as good as what I suggest and you will spend a lot of time reinventing the wheel.

So if you study post 9
What will it take with YOUR setup to get a profile like that?

We have a tool for that
http://deltamotion.com/peter/Videos/curvetool.mp4
You can even make a profile in Excel and copy and paste it.

Is there an algorithm I could use to handle this?