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Author Topic: Need Guru input on an idea: Using Mach as dynamic balancer  (Read 14756 times)

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Offline simpson36

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Re: Need Guru input on an idea: Using Mach as dynamic balancer
« Reply #10 on: May 15, 2010, 03:23:10 PM »

On your accelerometer, I would pick one that you could adjust its trigger, since each thing you try to balance may have different out of balance amounts. I would put the Unknown object in the spindle, then turn it on, then I would "increase" the trigger force until the strobe quits lighting all together, then come back in, till the strobe lights again, at the very edge of max detection. that would show the "Top of the bell curve" of your deflection.

Could this be done with an analogue accel. using a pot to adjust the input until Mach just 'sees' the high points of whatever signal is being produced?

More than likely there is a way to filter and condition the signal from the Accel, but that's over my head.  That's why I was trying to scare up a Guru or two.

I think I can figure out how to fire the strobe with a Mach output.

Offline RICH

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Re: Need Guru input on an idea: Using Mach as dynamic balancer
« Reply #11 on: May 15, 2010, 06:42:39 PM »
Simpson,
I was assuming the R8 or 5 spindles would be used in your 4th axis you have been working on.
So comment referred to end use.
RICH

Offline khalid

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Re: Need Guru input on an idea: Using Mach as dynamic balancer
« Reply #12 on: May 16, 2010, 07:36:12 AM »
Hi,
I am also looking for the solution..We had a manual balancing machine for compressor/Turbines rotar etc.. I also want to make one with Mach3.. Will closely watch this thread...

Offline poppabear

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Re: Need Guru input on an idea: Using Mach as dynamic balancer
« Reply #13 on: May 20, 2010, 04:31:15 AM »
Ok, lets make some "Assumptions", since your not providing what you want to use.

Lets assume your Analog device "accelerometer" will put out a 0-10v, or 0-5v analog signal the high end of the range would represent the "Max",
acceleration, that you trim out with your "adjustment" pot or what ever, for that piece your spinning.

I would purchase something like an Automation Direct DL05 PLC, and a 12 bit analog module that has at least 2 inputs. I would have one of the inputs that is feed
by your Accelerometer, and the other input, I would use to "adjust" high or low, the Raw data coming in on the accelerometer. This would allow you to Fine tune, your device "On the Fly" (so to speak). You would have to purchase and do some reading and set up your ladder logic in your PLC.  I would set it where, I could tune (using the 2cd input with a POT, so as that the max signal will just barely exceed a "Threashold" value. At that point (Using a compare statement), I would go to a "Control Bit" as an output, that will write directly to the Serial Plugin Modbus as an Input. When that Input goes HOT, (representing max deflection on your accelerometer), I would have mach trigger an Modbus OUTPUT in a brain this is triggered off of the SErial modbus input. That would come back to your PLC and trigger an OUTPUT what would fire your stobe. Also, since the Trigger could technically be "inbetween" machs scans, I would my my Accelerometer control bit a "Set" control bit, and when the Strobe output went HOT, I would use that output as a RESET for your Set control bit.

Cheaper solutions may be that you purchase a: M1/M12 from CNC4PC (M12 has 4, 8 bit analog inputs), OR, you can purchase Peter Holmans ModIO device he also has Analog input capability. But since those devices dont not have "Programable" space on them, you would need to do your calculations in VB script in the Macropump, OR, in Brians, or perhaps a combination thereof, or a plugin.

scott

scott
Commercial Mach3 & Mach 4, Design/Build/Retrofit CNC and Industrial machines.
http://www.ss-systems-llc.com/

Offline simpson36

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Re: Need Guru input on an idea: Using Mach as dynamic balancer
« Reply #14 on: May 20, 2010, 05:40:20 AM »
Ok, lets make some "Assumptions", since your not providing what you want to use.
Scott, I am not providing what I want to use because I don't know what to use. I don't know enough about electronics to make an informed decision on the best way to proceed. So I ask questions that hopefully are not terribly stupid and leave it to experienced people like yourself who offer up ideas that perhaps would have never occurred to me.

Quote
Cheaper solutions may be that you purchase a: M1/M12 from CNC4PC (M12 has 4, 8 bit analog inputs), OR, you can purchase Peter Holmans ModIO device he also has Analog input capability. But since those devices dont not have "Programable" space on them, you would need to do your calculations in VB script in the Macropump, OR, in Brians, or perhaps a combination thereof, or a plugin.

Here is a good example of what I just mentioned. The solution you outlined with the PLC would be too complicated and expensive for a layman, certainly for me, but this looks like a palatable alternative and gives me another idea. I have seen some accelerometers that are already installed on boards with some controls built in. Some are pre-assembled and some are in 'science kit' form. Perhaps that would be a place to look to get the sensitivity adjustment needed.

Offline simpson36

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Re: Need Guru input on an idea: Using Mach as dynamic balancer
« Reply #15 on: May 20, 2010, 06:04:21 AM »
I was assuming the R8 or 5 spindles would be used in your 4th axis you have been working on.

Yes, the R8 is the mill spindle and runs 8,500 RPM max. The 5C is the 4th axis and would only run in the 4,000 RPM neighborhood (hopefully), but it has a 4" steel disc brake on it that is not balanced, so even with the lower RPM, it is a larger problem.

I have had the mill spindle over 7,000 RPM so far and while it is smooth enough for most of the range, it has some harmonics at certain RPM, so there are some 'illegal speeds' that I would like to eliminate. Only yesterday I finally was able to get the 4th axis spindle up to about 3,000 (estimate). It has no harmonics, and is pretty smooth, but if you slap a 4" 3 jaw chuck on there you get quite a vibration. I could send chucks out to be balanced, but I have lots of other uses for balancing capability, so I still need a solution.

There are two other reasons that I am persuing this capability; One is that if the spindles are well balanced and I have some form of rudimentary 'in place' or 'field balancing' capability, I would then be able to balance (within reason) any part that I made on either spindle.   Second is for production purposes; if a badly unbalanced part, say a casting for example, needs to be turned, it can be done much faster if a counterbalance weight is added to the fixture.

As I mentioned earlier, for my own purposes, I believe I have a solution in hand with a particular programable USB scope. However this is still a very interesting topic to discuss and it would benefit a lot of Mach users if an inexpensive and reasonably effective solution was developed that utilized the CNC PC and MACH software that's sitting there already.



 
« Last Edit: May 20, 2010, 06:08:12 AM by simpson36 »

Offline Dan13

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Re: Need Guru input on an idea: Using Mach as dynamic balancer
« Reply #16 on: May 20, 2010, 12:19:13 PM »
Hi Steve,

Just wondering what kind of bearings do you have on your mill spindle and how is it cooled to run at 8500RPM?

Daniel

Offline simpson36

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Re: Need Guru input on an idea: Using Mach as dynamic balancer
« Reply #17 on: May 20, 2010, 02:03:14 PM »
Just wondering what kind of bearings do you have on your mill spindle and how is it cooled to run at 8500RPM?

No hijacking, naughty boy.

Start a new thread on medium speed spindle cooling and perhaps I will participate.

Offline RICH

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Re: Need Guru input on an idea: Using Mach as dynamic balancer
« Reply #18 on: May 20, 2010, 02:03:38 PM »
Quote
has a 4" steel disc brake on it that is not balanced, so even with the lower RPM, it is a larger problem.
The spindle should be balanced as a unit, thus it would include the disc brake.

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no harmonics
Yes it does, the spindle has a natural frequency ( all things do even the human body) and a critical speed, and whether you get vibration or worst yet resonance can be
 dependant on the dampening effects of the mounting, bearing, machine frame, runout,  etc, and could be influenced by repetative driving forces and transmissions.
Usualy you deisgn the part or system to not operate near a harmonic, in some analysis it is looked at to the 16th mode and design
changes made to move the natural freqeuncy away from a resaonant point for a given or fixed rpm. In the analysis, the harmonics of the system are used
and it is important to go through the resonant points / modes in a timely fashion such that resonance cannot occur.

You can have a spindle balanced to satisfy some spec, ( there are ISO and ASME spec quidelines for rotating machinery ). As you have become aware, as soom as you
add a different component  the balance changes, runout changes, leveling plays into this, the natural frequency has changed. As a component in the makeup, a good
example is the addition of say a set screw / screws, or weight additive attachment can be used, or even a movable balance plate can be used to advantage, but ,
like all things it becomes a matter of degree and what your trying to do ( your unlikely to be removing material to accomplish it).
The 4 jaw chuck can be balanced, but then as soon as you put something into it there goes everything  to poop again.

From a practical viewpoint, lets use consider what we do instinctively on say a lathe. If the lathe starts to get some vibration while we are trying to turn
something mounted off center, we slow it down and take cuts to make things symetrical and at some some point we crank up the speed and do more finishing to the piece.
Instinctively we deal with balance, runout, and vibration.
Now if you were to do some study on a part relative to it's natural frequency and as compared to degree of out of balance / loading conditions you could probably
relate back to some calcualted  speed and balanced adjustments. Not something you would want to invest into if not in a large production quantity.
Time spent trying to follow a procedure may not pay when an additional roughing cut may be quicker.

I guess my viewpoints are more from a design point of view but the topic is of interest.

Back to the sidelines......
RICH
« Last Edit: May 20, 2010, 02:06:11 PM by RICH »

Offline simpson36

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Re: Need Guru input on an idea: Using Mach as dynamic balancer
« Reply #19 on: May 20, 2010, 02:41:58 PM »
The spindle should be balanced as a unit, thus it would include the disc brake.

We are talking about balancing in-place, so the entire rotating assembly would be balanced by default. If the imbalance is too far from the center, then you would need to a true dynamic, which is sort of beyond what I am talking about in this instance.

Quote
The 4 jaw chuck can be balanced, but then as soon as you put something into it there goes everything  to poop again.
I was talking about a 4 inch chuck, not 4 jaw

Quote
From a practical viewpoint, lets use consider what we do instinctively on say a lathe. If the lathe starts to get some vibration while we are trying to turn
something mounted off center, we slow it down and take cuts to make things symmetrical and at some some point we crank up the speed and do more finishing to the piece.

You make a valid point, but limited to something that should be and eventually will be symmetrical. I was thinking in terms of a workpiece (or assembly) of some odd shape that will have a monstrous imbalance before during and after the cut. Cutting such a part in extreme slow motion is one solution, but often that will result in an intolerably low SFM or intolerably high production time.

You would agree, methinks, that the closer you can bring the part into balance, even a very rough balance for example by bolting a bob weight to a rotating fixture or even just a face plate, the faster you can spin it for the needed operation. That's all I was talking about, in practical terms. I would tell a story about huge eccentric hinge pins, but I see my time is up... ;)