DC Drive replacement

Giving a bit of a stab in the dark here, since I haven't used any DC controllers.

Firstly, All modern drives that I have seen so far have in built PID control. I am sure some don't, so be careful, but you can get a drive with PID control and this may eliminate the need for another controller.

Secondly, the input signal should should conform to the 4-20mA, 0-20mA, 0-10V or similar standard. If not, it may need signal conditioning.

Thirdly, quite a few drives have in built equivelents of PLC control. This could also be of assistance in eliminating the need for an additional controller.

Remember, if they could do it in the past, you should be able to do it better now.

Doug

Ok let me explain how most printing presses work. Your unwind usually doesnt have a motor except a "take up" motor for splicing on the fly...this depends on the type of unwind.

The rewind will maintain tension usually thru a "dancer". A dancer can be numerous devices but its a roller that puts weight against the paper, if the paper tension increases this roller is pushed up and the "dancer" sends a signal that provides "position" or "rate of tension", the drive usually incorporating PID will use this signal to adjust the speed...if roller goes up then rewind slows down, if roller falls then rewind speeds up.

It depends on the type of printing press what is used for actual speed reference. A gravure press may use one large motor to drive many decks but its speed will be set by the operator. This will usually be the main speed reference the rewind will operate from.

In some cases there may be a "nip" or "chill" roll that is the "lead" motor that provides the speeed reference.

In most cases the devices should work with a newer DC drive. Verify what the output signals are and match that to the new drives capabilities.

If this OLD drive is a Reliance Maxpak then look at getting a Reliance Flexpak...its more or less a drop in replacement in many situations. I would have a Reliance drive representative look at the system and give you a quote etc.

What brand rewind is it?

NOTE: New drives are digital and PID is setup thru programming software or the operator interface. ON older DC drives it still used a form of PID but it was done electronically (not digital) so it doesnt "appear" to be the same thing.

The machine is Italian, it is a Cerutti Printing press.
From what I can get out of the documentation, the control is done by a Ward-Leonard system.

This machine has the same setup at both the rewind and unwind ends, they do sometimes do splicing on the fly as well.

The Dancer scenario looks exactly like what you described. From the schematics, it looks like it takes a speed reference from the paper speed as well.

Will have a search for a local reliance agent, have a feeling though it could be slightly political if it is a rockwell product.
We are looking at using Sprint-electric drives, they are UK based, but seem to have some good looking kit.

Hey scottmurphy

We have a simular set up on several of our machines.Ours are tubular knit textile {fleece wear.. sweat shirts etc}machines, but the principle should be the same.Instead of a variable resistor mechanically linked to the dancer most of our machines use an analog proximity switch and an offset cam. Just something to consider if you go with a VSD.

Later Todd.

I worked at a plant that printed xmas paper, they had 7 Cerutti gravure presses and one Flexotechnica (Cerutti) flexo press. Many were old but didnt have a mogen (Ward Leonard) setup, most were just older DC driven with alot of cards involved. The rewinds could be messy because the motor/gearbox setup, on the spindles, had issues, the turret was ok tho. We did have alot of paper converters that used mogen sets tho and one gravure press (not Cerutti) that did.

Contact a Reliance rep, they have ALOT of experience with rewind applications and DC drives. Note I am not a Reliance rep but in DC driven applications like this I think they are one of if not the best.

This is a WOW for me, I finally get to see questions in a specific field I am familiar with.

Thanks for your replies chaps, I will take the info and ponder over it, I am still looking for a reliance rep, but am also dealing with another company that is being quite helpful.

On the subject of questions being asked in a field you are familiar with, how are you with hot embossing registration control?

The difference with this method compared to a traditional printing press is that we have to stretch the material to get it to fit the print pattern. ie. the drum is 523, and the print repeat is 520, so we need a 3mm stretch, and need to maintain this.

Any experience......anyone?