Flying Saw

Determine the reason why the <...synchronous problem occurs...>, and put in place such measures that will prevent it happening again. After all, it cannot be seen from here.

Without knowning the process control systems such as feed back loops, timing and safety on the processes....well, it could be almost anything!

Flying cutoff saw systems are a coordinated 3 axis motion control application that requires precision. If you have a motion controller and some of the programming is incorrect, you need someone who understands it to look at it and troubleshoot it. They are VERY specific, so make sure whomever you hire confirms that they have experience with YOUR SPECIFIC motion control system, you do not want to pay for a learning curve.

If you are attempting to accomplish a flying cutoff saw without a motion controller, you are asking for trouble.

Tube cutting systems work generally in 2 axis : parallel to tubing forwards movement and normal to it in cutting and retracting.

3 times are synchronized with tubing advance and the retraction time is coordinated with the length which has to be cut.

Depending how and where the blade was destructed you get a 1st information about which part of the program is wrong.

Although principle is the same control systems differ depending on the sensors used and type of controller.

I called it 3 axis because you have to control the cutting motion of the saw itself, either up and down or sideways. That's geneally not necessary to be as precise nor controlled by a servo, but it still has to be part of the control system. So I suppose that could be called 2-1/2 axis by some. It's just that it seems whenever I use the term "1/2 axis" to someone not familiar with motion control, it confuses them.

I've known a lot of "1/2 axis", too.

Great name for a motion control integrator too.

"Half Axis Control Systems".

Gotta remember that if I ever decide to go back into that industry.

As others have said, get a machine service technician to fix your saw.

Or go back to manual cutting.

It should be fairly simple to do a cost/benefit analysis of:

1. Repairing the machine properly and regaining full production capacity

2. Losing production time/product and buying new blades

3. Lost production/added cost of manual cut-off process

Call the man!

If there is any error in the program then every time a new blade is used it can be destroyed during first operation, the only way is to repair.

In order to avoid such situations it is may be a solution to have 3 controllers which will allow as well a continuity if a difference is noticed by majority voting as an error detection if differences are logged which could reduce time for error seaking and correction.

Cost of production losses is in many cases so high that a more complex solution for higher reliabilty is economical.

Saws on tube/pipe mills have a couple common trouble spots that are usually the cause of the problems:

First one is Tach Wheel to Tube/Pipe interface... tach slips, the saw thinks the mill is slowing down. Key indicator, your cut takes on the profile of a curve. Common contributing factors to this condition revolve around:

Wrong kind of lubricant or too much lubricant in the tach-wheel bearings, or wrong kind of bearing to begin with - the best type of tach-wheel bearing is a free-spinning, something akin to a skateboard wheel, lubricated with oil, not grease.

No vibration isolation between the cutting area and the tach wheel. Let's assume you have sealed bearing lubricated with grease supporting your tach wheel the vibration caused during the cutting causes short time burst where your loose contact between the tube/pipe and the tach wheel. The bearing seal and grease create excessive rotational resistance so every time the tach separates from the tube/pipe, it slows down, screwing up your line-speed match.

There are a number of other causes, and having worked in the Tube and Pipe industry my whole career, I have probable seen them all. If you give a little more detail, I can probably narrow in on the culprit.

If you are talking about an existing flying saw that has been in service (sucessfully) for some time, you might consider the simple maintenance problems first!

We had a flying saw in a lumber fingerjointing plant where a continuously moving ribbon of 2" x 4" lumber was cut into 32' blanks. The flying saw started getting destroyed and the maintenance guys all started pointing fingers...the mechanical guys started blaming the electrical guys and vice versa.

Just out of curiosity, I looked at the linear ball slides on the saw assembly and noticed that all the balls had disappeared. No wonder the servo drive couldn't match the speed of the line! Replacement of the linear slides and a kick in the a** for the guy who was supposed to be greasing the things was all it took to fix.

As an aside, this flying saw was only one axis of servo motion. Once the saw was moving the same speed as the lumber the saw was operated by a simple air cylinder with limit switches on each end of the cylinder stroke.

Jon.

Hi all,

Generally when the tube is changed problem occurs.

Lengt is Ok. Because we must do some adjustments work or setting.

But when we change the thickness or diameter blade is killed.

Therefore we udjust cutting time, distance between blade and pipe and also some modification about clamp jaws.

Our saws work 3 axis.

1-) saw carriage backward, forward

2-) saw blade backward-forward

3-) saw blade up-down

Manytimes form-calibration causes blade killed.

Best Regards,

Musa UÇAN

Based on this, I wonder where, and how, you are picking up your speed reference for the saw? Your positive contact tach-wheel should be mounted either between your lasting Sizing Stand and your first Turks Head or between your last Turks Head and a Vibration Isolation Stand.

Having done this myself, I suggest if the tube is stiff enough, then mechanically clamp the saw to the exiting tube (not the cut-off) then release it when the cut is completed, a spring can return it. Can't go out of sync then.

Tony

"...then mechanically clamp the saw to the exiting tube (not the cut-off)..."

ALWAYS good to "lock" saw carriage to workpiece; if pipe is steel / iron, use an electromagnet to clamp them together. The type used for bases of portable power drills should do the job nicely, and will avoid the need to design from scratch.

Yes, nice idea Ron, may need to be profiled, depending on the tube profile.

I was thinking more of a pair of clamp blocks, maybe clamped as the saw begins it's stroke and released when it retracts?

Tony

Right: base should conform - but there's already a fairly straightforward method, though I don't know for certain whether it is in production. See http://www.google.com/patents?id=btsTAAAAEBAJ&printsec=abstract&zoom=4#v=onepage&q&f=false for a pair of plates which serve to adjust the pole-pieces for work on cylindrical workpieces.

If magnets are unsuitable for any reason (non-magnetic pipe, e.g.), then clamps, preferably with some spring-like means to permit the jaws to conform to the workpiece, are the answer.

Flying saw!! the mind boggles. I'm only surprised it was just the blade that got killed.