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Introduction and question

MailleMas

Plastic
Joined
Mar 10, 2011
Location
Swift Current, SK, CA
Hi All,
I'm a machinist by trade living in Canada. I have yet to write my last tests for journeyman, but have all my hours complete. I've only found this site recently and have found it chock full of great info! On to the question:

Myself and three friends have started a manufacturing facility. Some of the older machines we have I would like to convert from mechanical (cam-shaft) driven to some variety of computer control. The cams actuate mechanisms to handle wire, and both timing and displacement need to be consistent, accurate and independently adjustable. At the moment the two camshafts are driven by a single 1/4hp motor. I was considering using a screw drive (or linear motor) on each of the cam linkages to replace the camshaft, tho small solenoids or small air rams also could be used if the control is much easier and cheaper. The max displacement of any linkage unders 1/2".

If I could hear some thoughts on what type of controllers I should start researching, I'd be thrilled. My main problem is I have no real idea where I should start looking. Is this a job for a CNC type controller or more in the realm of PLC, or some other option I haven't heard of?

Any other info you might find helpful I'd be happy to give.
 
Hi All,
I'm a machinist by trade living in Canada. I have yet to write my last tests for journeyman, but have all my hours complete. I've only found this site recently and have found it chock full of great info! On to the question:

Myself and three friends have started a manufacturing facility. Some of the older machines we have I would like to convert from mechanical (cam-shaft) driven to some variety of computer control. The cams actuate mechanisms to handle wire, and both timing and displacement need to be consistent, accurate and independently adjustable. At the moment the two camshafts are driven by a single 1/4hp motor. I was considering using a screw drive (or linear motor) on each of the cam linkages to replace the camshaft, tho small solenoids or small air rams also could be used if the control is much easier and cheaper. The max displacement of any linkage unders 1/2".

If I could hear some thoughts on what type of controllers I should start researching, I'd be thrilled. My main problem is I have no real idea where I should start looking. Is this a job for a CNC type controller or more in the realm of PLC, or some other option I haven't heard of?

Any other info you might find helpful I'd be happy to give.

Welcome and hello! There are several here that should be of help to you. Motion Guru comes to mind, but you should be seeing some responses here soon from some of the local denizens.
 
Welcome and hello! There are several here that should be of help to you. Motion Guru comes to mind, but you should be seeing some responses here soon from some of the local denizens.

Mr. Guru sent me in the direction of Emerson unidrive when I had a similar situation. I had a constant Torque rewind application for textiles and while I personally had a large learning curve, you should have no problem. Here is the sales info on it:

Winder Solution

The unidrive is expensive but well worth the cash.

Jason
 
I have a lot of experience with wire forming machinery and one of the things to be aware of is the magnitude of the forces on the mechanisms that are currently cam driven.

Are these a four slide type of machine or something custom?

Cams are very elegant devices because of the accuracy and the force they can generate to drive a mechanism. Unless you really need to have adjustability I'd try to leave the cams in place and maybe learn how to design them, it's quite easy.

That being said a PLC is more than adequate for something like this but again we need to know some details, how many axes etc, and of course Pictures Pleeze!

The complexity of your control system will depend on what degree of adjustability you need.

Servo drives with build in indexers allow for a set number of pre-programmed moves to be ran as stand-alone systems. Simply send them an input from a switch or plc and they will execute a "move" by themselves. That move can be a simple in-out or for something like bending it can be rapid until the mandrel hits the wire, then slow and then a rapid retract.

A lot of drives will allow for multiple indexes that can be pre-programmed and then selected depending on machine setup.

Chris
 
Do you need the adjustments for job optimisation prior to relatively long runs or for rapid changeover between short run jobs?

If its the former it may be worth considering exploiting modern CNC machining capabilities to make job specific cam sets "on demand" rather than undertaking major rebuilding. Far as I can see designing a cam set is not, in principle, different to programming a computer or PLC based system so much of the learning curve will be similar. A pretty modest CNC set-up should be adequate as you won't need production speed or, presumably, large component capability. Something from the better end of the Home Shop range ought to be up for it, either 4 axis vertical style or lathe with live tooling spindle operating much as a form relieving machine does.

If you can produce exactly the cam profiles needed for each job it ought to be possible to lock, or dispense with, many of the fiddly mechanical adjustments. Especially if these are mostly provided to let one cam form do multiple jobs. Ideal would probably be to have a cassette style changeover where you swop a whole box containing cams, shaft, drive et al. One on, one off being set up for the next job. Don't forget toothed belts. They make so many "used to be hard" drive jobs easy. Simple cam manufacture means you can relax material constraints. Bottom line is its good enough if it lasts twice as long as the longest job takes before wearing out of spec!

As Chris says cam operated systems easily produce considerable forces and accelerations. The amount of power reserve needed for an actuator driven system to be a direct replacement can be a nasty shock. Especially when you hafta explain to the boss why you've gotta tear it all out and start over! When going the actuator conversion route its essential to start with a force and acceleration analysis and consider if a different way of going about things suits electronic control better. Cam systems inherently tend to be constrained in timing and rotational velocity. With electronic systems its easy to, effectively, vary relative cam timing and velocities during the cycle which can be exploited to reduce acceleration and force requirements. Think of the solution "what movements do I need at the business end" not the problem "how do I convert these cam movements".

Clive
 
Wow, this post got backburned and lost for alot longer than I had feared. Thanks for putting in the effort to reply everyone! Sorry I kinda lost this one (to be fair it got lost for at least a day during some server issues on PM's end).
My shop is busier than I dared dream at them moment and myself and 2 other partners are running the machines 24/7 (ish) and plan on continuing that for the next 6 weeks at least! Obviously, things like major machine redesigns are on hold! I will be looking into PLC control much more seriously then. However, I might as well start the learning curve now.

Now, answers for all!:

Clive603:
I mostly need pre-job optimization with some continual tweaking for a purpose built machine. As for CNC machining capabilities, my shop has none. I have ran 3 and 4 axis mills and 2 axis lathes, but now am strictly a conventional guy. I am planning on fixing each cam more securely to the shaft (dog point set screws instead of standard). As for a force and acceleration analysis, I haven't even begun to start systematically evaluating that yet. The original cam designs are not exactly an optimal benchmark to look at (lots of hand grinding and basically a train-wreck all around)

Chris999:
It is similar to a 4 slide, but is a custom machine. Max wire size right now is 0.032" dia so forces shouldn't be too bad. I will be trying to eliminate the cam adjustment on these machines eventually. I think the other 70 points of adjustment should suffice! The machines dont' need a large range of adjustability, but they do need repeatable and predictable movement, accurate to 0.001" . If built in indexers are adjustable, and fit that bill, I am excited! I'll look into them. Thank you.
As for pictures, I am not prepared to spill the beans just yet. We aren't the only company using these machines, so I don't want to spread things around.

Tonytn36:
Rotation rate is between 100 and 150rpm.

Jason H:
Thanks for the info, I will check it out asap. I have to be to work in 5 hrs so, that might be a few days lol It looks like it might have uses in a few applications I am looking at.

gorilla,
Thanks for the welcome!
 
You will need a motion controller, some PLC systems do an OK job, some don't.
You will need to know the forces/speeds/accelerations to figure out your requirements.
You will need to figure out what sort of interface you want...I suspect you will want a screen and a way to enter data, but maybe you are OK with programming each part on a PC then reprogramming the machine.

That's where to start.
 
Thanks Miguels224,

I was trying to determine if PLC was sufficient for my needs, or if I needed a CNC style control.

Speeds, forces and accelerations I will attempt to estimate when I have more time to work at this. Speed should be easy, acceleration, somewhat less so, and forces will need some serious considering to get anymore accuracy than "uhhh... 'bout that much".

I do have an interface idea that I will probably need to get custom coded, well adapted anyway.
 








 
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