Wire Drawing m/c using Siemens Master Drive

Hello everybody,

A few days back I was asked to design a control panel for a EDM wire drawing m/c. The m/c is already there but the old control system had to be done away with because of too many problems with the old DC drives.

The machine basically has One main DC motor which is drawing out the wire through chain of dies,one spooler DC motor which is spooling the wire in different size spools. The Spooler drive has a additioned reference from a dancing arm. The traverse mecahnism is via a smaller DC drive.

We decided to go for Siemens Master Drive 6RA70 series for both the Main motor and the Spooler Motor.

The Control panel is now ready, the Siemens guy came down for the m/c commissioning and after 2 days told us that he needs to use the S00 drive technology s/w to do the job. The drive technology software is free for 500 hrs and after that we have to pay around Rs 30,000.Now, this we were not told earlier and since this would add to the total cost of the already budgeted project, it is going to be difficult to explain to the higher autorities.

The siemens guy would come back after 3 days again for the commissioning ...no probs for me.

The problems for me now is that I have been asked to try and synchronise the 2 drives for the m/c in these 3 days time gap !!!

Personally I have never used Siemens Drives. Now I need to study the Control system for the machine as a whole for the Wire drawing application and then implement it using these Siemens Drives.

A long shot for me, but I want to try for sure. I believe that there must be a structured process approach for such application.

Although I am not asking for someone to do my job for me but a hint and a few suggestions as to how the application in general should be approached would give me a good start.I don't mind burning the midnight oil if I can learn anything from the situation here.

Thanks to you all in advance.

-Anshuman

I've used Simolink + F01 to synchronise Masterdrives drives together - what is your connection between the drives so you can synchronise them ?

I find it a bit disgusting that the Siemens folks are not there helping you with this. It sounds to me like you have bought four of their drives. I would think that that deserves at least a little factory support.

I suggest putting some pressure on Siemens for the support you deserve.

Thanks for your replies guys !!!

Well, what I understand from the application :

The Main drive would run at a constant speed as set by the operators say ...1500 rpm which would amount to a line speed of say xy m/min.

Now the Spooler Motor ( winder ) would have to spool this wire in a spooler. As the wire dia is getting reduced and there by the length of the wire increases when it passes through the die set ( when drawn by the main motor )..the spooler motor has to run at a higher speed to compensate for this increased length.

As the spool dia increases the Spooler motor has to decrease speed to maintain the same line speed.( Diametric compensation )

The Spooler drive is also responsible for maintaining the tension of the wire in the spool. This is done by the dancing arm which is the second speed ip to the Spooler drive, the first comes from the Main Drive and these 2 sp are additive ( Tension control )

So basically the application requires :
1. Diametric compenstion
2. Wire tension control.

In total the synchronisation has to be done between the main motor and the spooler motor with the dancing arm as the stabilizing ip for tension control.

The system has 2 Siemens Master Drives of 6RA70 series and no additional PLC.

I hope I was able to throw some light on the requirements of the application.

-Anshuman

If you examine the detailed description of the free blocks available (refer to the Compendium), a technology controller (PID) can be used to provide a basic dancer controlled spooler. The free blocks also provide multiplication/division as well as boolean logic so you should be able to piece together a spooler controller. A print out the all the function diagrams will be worth it's weight in gold when implementing this type of system in the drive. Remember you've got all the free functions in two drives available if you run out of functions in one of them - it all depends on how many free analogues you have to interconnect the signals between the two drives.

A basic controller may work for you, it all depends on the required dynamic performance of the machine, the spooler build up ratio (max diameter/core diameter - if too high will require gain profiling), and the variation in different wire diameters required.

If you are not familiar with a MasterDrive, then 3 days to get it going might be a bit tight (no pun intended!).

I put the Centerwinder manual in the "Downloads" section.

This will shed some light on your application. I have started up several of these and no "option" is needed for this application. I am not aware of any 500 hour option or PIN number like the 6SE70 MC has. I would be very surprised if these are Siemens engineers at your plant. Siemens has canned "script files" already done and are very easy to impliment.
Anyway, that is a whole different discussion.
Check out the manual under "downloads"

Thanks JRW for the link, by chance I also stumbled upon the same link yesterday while suring for some tips. I am going though it, and yes these guys are from Siemens, and If they are playing with me then God help them !!!

Currently I am searching for a structured step by step approach to this application be it Siemens or ABB Controllers or what ever.A common approach for all controllers.

By the way I didn't understand what you meant by

"Siemens has canned "script files" already done and are very easy to impliment."

Would you please elaborate ??? Thanks

-Anshuman

help needed

in need an analog inputs signal to profibus converter ? can you help me?
regards
prasad

Guys anyone with any Idea ? I am sure many of you have done Wire Drawing machines before..for your information ..the Siemens Guys are back and now they have a new Idea : a diametric compensation device/ sensor ...this was after the software thing with S00 and the only 500 hrs availibilty story ...

-Anshuman

You are getting very bad advice.

Your wire-drawer is a simple machine, and the subsections have absolutely no reason to be closely coupled.

The drawing machine will run fine (with a simple ramp) all by itself.

The spooler, should be 100% dancer controlled. That is, PID Regulated on dancer position. I've had the best success running spooler machines in pure torque mode, but speed mode is possible as well.

'Diametric Control', is a term I'm assuming to mean 'Using dancer tension to neck down the wire from an oversize final die to the target final diameter'. The spooler drive doesn't care at all. For that, you just control the air loading on the dancer. Done.

The traverse control should be nothing more than a simple analog speed ratio off of the actual speed of the spooler motor. Traverse on a wire-drawer is not critical at all in 99.3% of the cases. In fact, a very loose traverse (more than 10 to 20 diameters between lays) usually results in the best final package.

The Dancer PID doesn't even need to use the S00 Tech functions, just use a seperate analog PID controller, and feed a speed (or torque) reference into the spooler drive.

Thankyou rdrast for your reply.

As you have mentioned I did try with your principle of the Spooler being 100% controlled by the Dancer, but being new to Siemens I am having a little trouble using the connectors and all, and my dancer arm is moving all the way up and down while it tries to regulate the spooler..

What I have thought of is these steps as under, I am doing this wiredrawing m/c for the first time so please do not mind if I am at the far end of wire drawing logic

The Main motor Rpm is 1500, the Spooler motor Rpm is 3150.

1. Run the Main motor ( which is pulling the wire out of the die chamber ) at say 750 rpm which would be say for our eg x m/min line speed of the wire. Note down the ananlog reference to the Main drive. Say this is 5 volts,with Acc time 5 secs.

2. Now put the wire trough the dancing arm ( the dancing arm feedback is not connected at this moment )and then start the main motor, now slowly increase the refrence to the spooler drive via a pot so that the dancer arm now is at a straight level ( which is the ideal place when the machine is running ).

3. Now measure the rpm of the Spooler motor at this speed with the dancer at a straight level.This is the max rpm of the spooler at the set speed of the Main drive.

4. Now we Set the Rpm max of the Spooler to this rpm ( change from 3150 to new value xyz rpm). So now at 10 v dc reference the Spooler motor would run at this Speed xyz rpm.Now we set the acc time to be 5 secs for the Spooler.

5. Now we put the wire on the dancer arm and the Spooler ( the dancer f/b is still out ) and start the machine,the reference to the Main motor is drive is 5 volts and the Spooler is 10 volts now .Since the acc time of the main motor and the Spooler motor is same the dancer would remain at the middle level through out acceleration and when the speed becomes steady. ( Only assuming )

6. The dancer arm span is a total of 2.5 volts dc ..in the middle it is 1.25 volts. The arranagement is such that if the dancer goes down the dancer arm op would be high ( 1.25 to 2.5 vdc ) and if it goes up the op would be low 1.25 to 0 vdc.

7. So at middle of dnacer we get 1.25 volts. Now adjust the analog op of the main drive such that if the Reference to the Main drive is 5 volts then the analog op1 should be 8.75 vdc, and put this 8.75 Vdc to the analog ip 1 and the dancer reference at analog ip 2.

8. Now put the wire in the machine and keep the dancer at the middle level, now the reference to the Spooler is 8.75+1.25 volts and the main Drive is 5 volts.The PID now tries to reach the set speed as required by this 10 v dc to the Spooler

Now If I run the machine, what do you think would be the result ( neglecting the effects when the dia on the spooler gets bigger ..if the m/c runs at all .

By diametric compensation I mean that when the dia of the Spooler increases the line speed would also try to increase if we keep the Spooler running at the earlier Rpm ( the main motor speed is fixed ).Now the dancer would start going up and start jumping again So to maintain the Line Speed we decrease the Spooler reference a little. ( This part I have not thoght out yet )

Pl.Let me know what you think and thanks again for reading all that I wrote

-Anshuman

You cannot control the spooler speed off of the main drive, unless in some bizarre world, you are doing a one-pass level wind on a drum.

The spooler bobbin diameter will vary over at least a 2 to 1 range, and depending on bobbin construction, you might have a much larger MAX_DIAM / CORE_DIAM ratio. Feed-forward will simply not work.

Your issue seems to be more with the tuning of your PID loop than anything. Tuning a Torque mode spooler is much simpler than a speed mode spooler, but at the danger of getting a severe overspeed on a wire break. (Which should just cause a drive fault nowadays).

The dancer PID reference should be your 'Target Run Point', or 1.25 VDC in your example. Then the feedback can go from 0 to 2.5 VDC, and when stable, you should be running at 50% storage.

There should be no reason to fiddle with line-speed limits on the drawing machine, unless your spooler drive cannot keep up when the bobbin is at small diameters.

Unless you have an odd design for the spooler, this shouldn't be the case on a wire-drawer at all.

Additional thought -

The spooler drive should have absolutely NO ramp time programmed in, for the run condition. Ramps are Bad Things here.

Also, start your tuning by running the spooler, tied to the wire, with the drawing machine at zero speed. Try for a stable dancer position. THen increase the drawing machine speed to a low value, perhaps 5 or 10%, and again, try tuning for position stability on the dancer.

Hello guys

Well..the Siemens guys are back and have been working on the machine for more than a week now ..without any improvement the dancer arm still rocks like a pendulum and we are making scrap like around 40 kgs /day I have already put a lot of pressure on Siemens here but it seems like nobody there has any experience with wire drawing machine at all..real bad situation here.

During the project negotiation I had disclosed everything to them ...with the details of the panel hardwire and relay logic built in ( No plc here )and they "boasted" that they would be finishing the job in a DAY !!! and believing them and the reputaion they had I was just waiting for a good learning experince for me, but now everything has gone down the drain when I ask those guys about the blocks they are using for teh synchronization ..so that may be I can throw some light on it they tell me that it a company secret ..and only Siemens technical guys are supposed to know that ..I donot know what to say

Just asking..have any of you guys faced a similar tight situation ???

-Anshuman

Sounds like they are insistent on running the spooler in Speed-Loop mode. Have them try direct torque control (not modifying current limits, but pure torque control).

Drawing machines are completely non-magical, and with a single drawing machine drive, should be a piece of cake.

Once more, there should be absolutely NO synchronization between the drawing maching and the spooler. They should be completely independent.

1) String Up Drawing Machine.
2) String wire onto bobbin
3) Start Spooler
4) Start Drawing Machine.
5) End of run, Stop Drawing Machine
6) When Drawing Machine is stopped, Stop Spooler.

The only synchronization required, once more, is a very loose coupling between the actual spooler bobbin RPM and the spooler traversing drive. That's it.