Learning by Doing

Doug-P said:
Would it be feasible to add a drive motor to run the feed spool? If so, this would ease the requirements for the feed/stepper motor

Technically feasible, yes. But I don't think it's economically feasible in this application. It would have to be set up on some kind of feedback system which senses the pull from the drive rollers downstream, or perhaps maintaining a degree of "slack" at the roll's perimeter. I wouldn't think that you could use a constant speed motor, since the effective diameter of the roll changes continuously, depending on what part of the roll the wire is feeding from at any given instant.

I should point out that the unwinding of a roll of spring wire is, in a small sense, self-driven. A certain amount of work is expended in coiling the wire. Since the elastic limit of the wire has not been exceeded, the work that was performed in coiling the spring wire remains within the wire itslef as stored potential energy. That energy is released when it is uncoiled, and in this case, that release manifests as a small amount of torque applied in the direction that the wire is uncoiling. Something to be reckoned with and/or used, as I see it.

pstephens
 
Last edited:
Mike

If you work with low consumption solonid valve.You dont need inerposing relay.
In machine who design for highly rate there is no relays outputs.
SMC Fasto and others have valve for that.0.3W with suppressor.
I use it all the time.
AB have outputs SSR cards for high consumption.like hydraulic valves.
I basically prefar DC output for most of my machines.
Assembely machine make many opration in minute un like elevator which make cycle im minute or so.
 
pstevens,

Looking at your diagram, your diriving the feed with a belt . If this turns out to be the case then and encoder is a must, as the belts are going to slip some, unless of course it's a timing belt.

The more I think about it the less I like the stepper motor. 1) you will need feedback to ensure proper length, which negates part of the reason for using the stepper (for positioning). 2) programming, setup, and servicing the unit will be way more complicated for a beginner.

Using a conventional motor with a drive will greatly simplafy your programming. Your inputs to the drive from the PLC will be as simple as Forward, Reverse, High Speed, Low Speed, and maybe Zero Speed. You will setup the drive seperatly so that it knows what to do with thoes inputs it gets from the outputs of the PLC. There will be no question about having enough torque to drive the wire.
 
Arik,

My big hangup is I see everything as an elevator....That goes for this projet too..

But you may be right on the soleniod issue, I donno for sure. It depends on the valve he ends up with.. However if all he's got to power with 24vdc is the inputs, encoder, EZ touch, and Drive signals he might be able to get away with using the 24vdc power supply on the PLC. If he powers the coil with it, he'll likely need an bigger power supply.

IMHO...
 
ArikBY said:
I dont know if you plan to use straightening wheels as Rube mentioned,I think it neceessary.Otherwise you will get "curves" in the end of the roll.

Hi ArikBY,

Straightening wheels are not needed for this application, as the wire was straightened prior to hardening. It is not an issue at all, in this instance.

My question is how many pieces per minute you want?

Since the finished length of the part can vary anywhere from 12 to 144 inches, the pcs/min rate will vary considerably. I proposed designing the machine with an 8-12 in/sec feed rate, and that was fine with the customer. Beyond that, he doesn't seem too concerned with the rate of output. It will easily be faster than what they are doing now, and that's all he cares about.

For 10 pieces fer minute Rube idea with limit SW is the best,You can pull very slowly "hit" the SW and cut.

Yes, but this would (presumably) require re-setting the location of the switch each time a different part length was to be run. It would make the handling of the cut parts much more problematic, as the switch support and wire guide setup would have to be worked around. It would also make the machine somewhat more unweildy. Metering the wire before it is cut has many advantages that my customer is eager to gain.

I think you need "Rewinder". 500 leb(240Kg) is pretty havey roll to pull and cut. The simplest system is with feed motor and 2 sensors. Up to systems with loadcell magnetic brake etc.

We will have to see on that. I don't think the budget for this machine will support much more than an air-operated brake to keep the feed roll from overruning. I'm guessing that the pulling issue is more economically dealt with on the motor-sizing end. I could be wrong about that, though.

Thanks for your vote of confidence on the DL06. I'm still trying to determine for sure if I need some kind of counter module to interface with the stepper. What kind are you using in your application?

Thanks for the suggestions!
 
pstephens said:
Thanks for your vote of confidence on the DL06. I'm still trying to determine for sure if I need some kind of counter module to interface with the stepper.

The encoder will connect directly to the D0-06DD via X0 & X1. You do not need a H0-HCTRO or what ever it is.. for the encoder. My calcs indicate that the counting function from the encoder will be well below the max rate for the built in counter function on this PLC.
 
Hi Mike,

elevmike said:
Looking at your diagram, your diriving the feed with a belt. If this turns out to be the case then and encoder is a must, as the belts are going to slip some, unless of course it's a timing belt.

Yes, I believe I mentioned somewhere that I would be using a gearbelt system to drive the rollers. I've had good results with these. They allow some flexibility in adapting the drive speed to the ideal RPM range of the motor. And unlike friction-driven belts, gearbelts do not strain the bearings, as very little belt tension is required.

The more I think about it the less I like the stepper motor. 1) you will need feedback to ensure proper length, which negates part of the reason for using the stepper (for positioning).

I was under the impression that steppers were sometimes used in conjunction with encoders. Oriental Motor sells a couple of different lines (ALPHA-Step and ALPHA-Step Plus), which have built-in encoders for closed-loop accuracy, though I'm guessing this is a pricy setup.

Using a conventional motor with a drive will greatly simplify your programming.

What type of motor would it be? How does it stop at a discrete position when the controller tells it? I'm open to all suggestions.

pstephens
 
pstephens

In this case I use the builde in counter it should be good enough.
According the rate you wrote it roughly 10-50 pic per/min.
First I would check if steper motor can do the job.You need to calculate the torque for gearing use timming belt in ratio of 1\3 or
1\4.(AD have step motors in decent price)
I think air brak would not work.The easy way is 2 sensors and feed motor.You need to have loop of your wire when the loop is loose the motor stop.when the wire is taut the motor start.very simpel system.
I made some wire feed systems like that in the past.
The loop allow you to pull from the loop with out the mass of the roll.
Encoder is always recomended.
Second using VFD in that case you must to have encoder.
You can set 2 parameters length and speed change point.
The motor will pull 95% in high speed and the rest in low speed.
Here you need also feed system.

Motor gear cost about like air brak.
If you go with VFD take one in one size above.(if you need 0.5KW take 0.75KW).
This option is very simple to program.
My program might fit for you in minor changes.That exactly my paper machine drive work.
 
Steper motor are very simpel.
The rotation divided for count let say 2000.
so if you send the motor 2000 pulses you will get one rotation.
If you play with the pulses width you will get different speed.
DL06 have build in function for that.
Step motor work with out feedback I would add the encoder for that.
 
pstevens,

To end the stepper motor debate I'm gonna suggest you go ahead and build the part of the unit that will include the drive and pressure rollers, and then some how measure the amount of force you need to grip the wire, and pull on the fully loaded reel at the desired speed. Since you will have a belt drive, mounting what ever motor you decide on, at a latter date, will not be a big deal.

Regarding the brake for the reel. I would also suggest an electro-mechanical brake. I'll bet that you could find a sutable one for less then $500.00, and it will pick and drop quickly, and likely need less servicing in the future. You would energize to pick/release and de-energize to drop/stop (spring applied).
 
forgive me for taking this back to basics but with +/- 1/8" tolerance for part length and not being a high speed output of product and most importantly "keeping the cost as low as possible".is there a chance to set up an adjustable sensor for length required ie.pe cell,proximity or limit switch,that the operator moves into position on start up ?.obviously for ultimate accuracy an encoder in a closed loop system is the way to go.
anyway just a thought.
:D
 
Since cost is a factor in the design you may want to look at http://www.plccenter.com

If the customer is agreeable to using surplus items in the design you may be able to offer more system for the same money.

Speck controls (plccenter) offers a multitude of items like Oriental motors steppers, Yaskawa servos, most brands of AC drives...just about any automation device you can think of, never hurts to checkout what they have.

The Oriental stepper motors I use to work with were the 5 phase that included an encoder, these were overall reliable units but I can state dont cheat on the wire (go to small) especially if the units are not stationary. These units were very precise in positioning.

I have also worked with Yaskawa servo systems (conveyance) that were reliable in positioning applications. http://www.yaskawa.com/site/products.nsf/home/home.html

As an FYI, I did some work for a company that made threaded rods: http://www.vulc.com/ that used systems similar to what you are designing. I can not remember the company names of the machines that cut the wire prior to threading tho. I noticed that this company, http://www.threadedrod.com/index.php also makes threaded rod if the process is similar and you could get a tour you may get some more ideas.

I can state they did not use a turntable with the wire, they fed it straight up thru a pulley system with a machine interlock...no material/no tension then machine stops. The machines I remember used regular AC drives with feedback from a counter or encoder and brakes to do a feed to length then cut style system. For the material being worked with I thought it was extremely fast. I would be scared to try cut on the fly with a metal product like a rod.

They also used a conveyor after the cut to move the rod down to a push/roll off (holding area) where the rods dropped into a box. This allowed the operator to replace the box without having to stop the process.

Wish I could remember more details so I could get in on this design thing but you have the real pros offering some great advice.
 
With a tolerance that sloppy why not use pneumatic motors on the feed reel and the feed rollers that way you could sync both motors. That would also enable you to use cheap metering valves to set the speed you want and also use standard off the shelf solenoid valves. when you shut off the valves the motor itself will act as a brake. I would think that the pneumatic motors would have plenty of torque for this application and are probably allot cheaper to. If you want real precision just use a pneumatic servo valve.

Just a thought, and it could be a bad one at that.

I just love air!
 
pstephens said:
I was under the impression that steppers were sometimes used in conjunction with encoders. Oriental Motor sells a couple of different lines (ALPHA-Step and ALPHA-Step Plus), which have built-in encoders for closed-loop accuracy, though I'm guessing this is a pricy setup.

The only problem with a motor mounted encoder is that it really only lets you know that the MOTOR moved the correct amount. Ideally, you'd want to know that the WIRE moved the correct amount. I'd lean toward an independent encoder driven by the wire movement.

We installed a few accumulators for a company that makes swimming pool hose. The hose is created by winding extruded plastic like a spring. They had the same type of cutter that you're using, and the cutter operated so quickly that it wasn't necessary to stop the process for the cut. It just cut the hose on the fly. The encoder simply measured the lengths (1' to 50') and actuated the cutter.

As Arik (and others?) mentioned, you don't necessarily HAVE TO use a stepper. An AC or DC motor may work just fine. When you approach the correct length, slow down, creep to the exact length, then stop and cut.

beerchug

-Eric
 
In My Humble Opinion.....for what it's worth.

Your big focus focus focus right now is on the mechanical aspects of this machine. Actually how your going to drive (motor type) it and the programming etc.. is going to be pretty streight forward.

So 1st thing I would do would be to build the friction wheels/drive mechinizem to grip and pull the wire off the reel. You can design machine and assemble this one assembly so that you can add whatever motor you want at a later day, whether or not it's a stepper or a convnetional C-face mounted type with a drive. After you've compleated this assembly you can test as to the amount of torque/power it will require to pull the wire off the reel, and force it through the friction drive assembly. And how well your drive wheels/sheaves grip the wire, how much tension is needed, the inertia on the reel, etc etc..

Ok so with that said here's a link for timing belts, sprockets, pullys etc.. These guys are REALLY helpfull, so dont be afraid to call them. http://www.sdp-si.com/D260/D260cat.htm

Also be sure to figure for mounting the encoder on one of the bottom idler wheels below the wire and drive sheaves. A simple 2 x 2 angle protruding out from the base under the idler to provide a tiedown that would keep the encoder from rotating. I usually mount my encoders rigid to the driving shaft, or use a hollowshaft encoder sized for the drive shaft then tie down the encoder with a stiff rubber leash. Others use a flexable coupling, but they eventually tend to fracture after some use if not lined up really really well.

So that's my say on the subject for now.

While there are a lot of smart people who already posted good suggestions I'm gonna say that you should really focus on building the machine. Then come back to this thread when you start working on the controls/motor/drive etc. That way you'll have a good way of testing your code and wont spend a lot of time suppositioning and dealing with all kinds of other noise from people like me.

Good luck with it. Mike
 

Similar Topics

Hello everyone. I am currently doing a project to teach about ethernet topologies such as ring or bus. For example. But instead of using an...
Replies
8
Views
4,321
Although I did not title it as such the last chapter would have been the PID. Learned a lot will give the details in that post. SO on to the...
Replies
20
Views
10,543
I've gotten to the learning curve where I can program a call for pump to come on at set point but I'm not sure how to turn the same pump off when...
Replies
1
Views
56
I want to pick up an Allen Bradley PLC so I can practice writing programs. I have 10 years as a maintenance tech and a good understanding of...
Replies
8
Views
221
Hi all, i have started a new chapter in my career with a local company. a lot of their plc's is omron and i have the cx version 9.75 software...
Replies
25
Views
4,156
Back
Top Bottom