Converting machine

I am working on a converting machine that is direct driven thru magnetic clutch to regulate tension on the final shaft. The new machines use a servo drive to control this shaft I am considering changing our older machines to this type of system. What it needs to do is keep a constant tension between this shaft and the rest of the machine. i am looking for the easiest cheapest way to do this. The simpler the controls the better. It is being done with a simple pot controlling the voltage to the clutch. i would like it to be a close to this from the operator standpoint as possible. The machines are being controlled by a step-7 200 plc ranging from a 214 to a 226 cpu. Any ideas on a simple system for this??

It's not flashy and its not state of the art but, if you want simple, you've already got it. An eddy current clutch acting as an adjustable torque drag brake.

Today, to do the same thing, we would use an induction motor with a regenerative AC drive set in regen torque mode.

As much as I like AC drive technology, if you can get parts for your present arrangement, stay with that.

The only disadvantage I can see is that your braking energy is wasted as heat whereas a regen drive would save it. Probably not worth making the change for energy savings alone although an analysis could be done to be sure.

The reason i am changing is we are burning up clutches too frequently. We are running a heavy material that uses a lot of clutch. They are costly to rebuild and getting hard to find. The new machine we purchased uses the servo for this. and i want to duplicate it if i can.

I have never used step-7 200 plcs but I have worked on many converting machines. I mostly use Eurother Drives ( SSD now) (690+ AC Drives) for converting machines. They ,in my opinion, have the best canned macros for winding and good math capabilities.



You can do the taper and tension math in the drive using the analog inputs and out puts. Their closed loop speed winder macro is quite nice.



If you want to keep it simple find a low cost PLC with analog in puts and out puts, a cheap operator interface and go to town. I generally keep all the taper tension math in the PLC because it is easier to change the taper calculation in the PLC when the cutomer want to different style of tension curve.



There are million way to skin this cat find one you like and as long as it works you are in good shape



Any special reason servos are on the rewinds????????



GO JETS

[font=&quot] Keep’em in Jersey[/font]

the reason they OEM went to servo was the clutch brake arangement was a maintenance issue with the clutches burning out frequently on heavy materials. As well as they rewind would get weaker and weaker as they clutch wore. the servo gives alot of adjustment for different web types. As far as set up all I need is to keep the same tension (operator adjustable) on the web @ all times and for the drive to stop and start with the plc. On the new machine this was done with a touch screen to set tension with i would like to do without on the older machines. I would like a simple pot control if this is possible??

I still do not see the need for a servo with a mechanical brake. Maybe I am missing something.



All I would do is over speed the rewind a bit keep tension with the brake



On the new machine is the clutch being used???? Or is the torque of the servo keeping tension??? On many Servo drives and AC drives torque is adjustable with a the use of some sort of analog input signal that can come from a PLC, pot or another device. I am assuming that your set up is open loop with no tension feed back.



At what speeds are you winding??? Is your rewind spindle slowing down as you diameter grows??? Does the tension signal (I assume it’s a 0 to 10 volt or 4 to 20 ma signal) to the drive or brake change as the diameter grows??





[font=&quot]Go JETS[/font]

thanks for all the responses The servo is replacing the clutch brake configuration. Running the rewind spindle. The spindle is not slowing down as the diameter grows. The tension is only changed as the product is changed. Such as light tension for paper and heavier tension for tight non-wovens. the machine is winding from 400 to 600 fpm.

Note guys, this is not a winder or unwinder application. This is a pinch or nip roll that runs with the web and tension is controlled simply by negative torque on the roll shaft.

If you want to do this job electronically, all you need is an induction motor with a regenerative drive sized to handle the torque and braking energy. Actually, if wasting the braking energy as heat as now, you can use a cheaper standard non-regen drive with snubber braking.

A servo for this application will work but is major overkill. The AC drive above is adequate to get the results you want.

I agree with Dick that this application will work acceptably with an AC induction motor and drive. Depending on what you are planning to replace you might also want to consider DC bus sharing. If you have one axis pulling backward, another axis (or two) must be pulling forward. If the DC bus for those axes are connected the regen energy from the retarding drive can feed the pulling drives.
This may be why the OEM listed in the original post used servos. Most of us are aware of servo packages with a shared bus arrangement. Not as many are aware of shared bus arrangements for standard AC drives.

Keith

Let me start by saying thanks for everyones input. As you can probably tell i am no engineer. I have been a tech for 9 years and have went to work for a small company that either modifies or builds most of what it needs. This is not a pinch nip application. This is actually a set of chain driven drives that are brought into a core that the material is wrapped around. at length the material is cut and the cones as we call them are disinguaged and the finished roll falls out. They then raise up and grab the new roll. These chains are driven by a single shaft that is controlled by the clutch/brake in the old configuration and a servo in the new. This type of machine is generally used for rolling christmas paper. we use it on much heavier much longer length materials. Again thnks everyone

Thought this sounded familiar....I am familiar with xmas and wall paper embossing. Is the machine 20 to 30 years old?

I am familiar with printing xmas and wallpaper...gravure and flexo.

I agree it probably isnt a NIP application but servo is still overkill.

There are several ways to do this. Got pics of the embosser and drive/clutch?

Most of those that have responded are far better at modifying then I am but i have BTDT...especially with xmas paper. Plusmark/American Greetings.

You with one the outfits that stole their contract? I am not with them anymore and that plant is closed.

rsdoran, If you worked for plusmart then u probably had one of these machines. It is an Elsner v-4-36. i am adapting the cone drives on this machine. we are running very long rolls through this machine. Thus killing the clutch???

Now that I know its an Elsner I know a servo WILL fit the application BUT its not just the cone drive you want to replace with it, its that limit switch/cam follower setup too. The main drive can still work the unwind and main drive rolls and the servo replaces all that gearing/cam stuff.

Makes the machine sound so much better.

I meant to post more earlier

Originally Elsners used a variable sheave drive with a clutch/brake on the cone (not variable) [sidenote: I wouldnt make the cone clutch brake variable]. Originally they used a cam follower system with limit switches which provided the length/cut.

The Elsner is basically an unwind/rewind system that cuts the paper on the fly. They were chain driven and very very noisy. The idea behind the servo drive eliminates alot of the chain drive for belts and is far more accurate on the "fly cut".

Elsners newer models are servo but its possible to use VFD(s) and clutch/brake assemblies with belt drives and accomplish the same thing. I converted alot of the drives to AC using a VFD but also converted some to belt drives and eliminated that cam follower/gearing mechanism. I also eliminated the wheel for an encoder.

May want to rethink using variable adjustment on the cone clutch.

There are several ways to modify these machines...I had 40 or 50 to experiment with at one time. Even a few of the Jumbo 48/60 inch units. We had one project making large rolls of that Dupont landscape material, cant think of the name for it. I got to convert a Jumbo just for that purpose. When done they threw the machine away. Take a loader and go dig behind Plusmark and you can find at least 50 Elsners, maybe more.

I converted a couple of their embossers. Did your company buy some of their machinery?