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automated noise check for gearbox continued

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engineheat:
Hi, this is regarding the noise check quality test automation project I talked about in another thread. I was able to use FFT to differentiated between a bad motor and gear motor. However, I originally thought about implementing this test on the production line, which has too much random noise. The FFT/microphone approach worked much better in a quieter setting.

Once the gearbox come off the production line, they get put into open top boxes, 100 per box, so 10 rows and 10 columns. The box is roughly 0.5 m by 0.5 m.

I'm thinking about building an apparatus that once place on top of the box, and it will turn on each handle via a servo or stepper motor, and a microphone can feed the sound to a processor. The whole thing can be placed in a quiet setting. So the requirement is:

1. A device that carries the microphone needs to move in a grid like fashion to examine each motor 1 by 1. The servo to physically turn the motor on/off will need to move in a grid like fashion too.

2. I'm not sure if the processing unit will need to move. If the CPU is stationary, then signal from the microphone will have to be wirelessly transmitted (please advise). I don't want wires since that'll get tangled up quickly in the grid like movement. Or I can use something like an Arduino to move along with the microphone. It might just have enough processing power to do some simple FFTs...

3. What's the easiest way to implement this grid like movement? How can I ensure the moving part moves a fixed distance each iteration? I'm thinking about building a 10 by 10 "track" that gets placed on top of the box. But that still doesn't solve the issue how setting the stopping points. Perhaps mark each point with a black dot and use an optical sensor?

4. I also need a way to display which motors are bad after the run. This can be a simple screen that display the row numbers and columns numbers. But if I place a 10 by 10 track on top of the box, it'll be awesome if we can light up a LED for each position a bad motor is found. This is much easier to locate bad products than reading row/column numbers.

What are your suggestions? I prefer quick and dirty, off-the-shelf solution as possible. If needed, I can also fabricate parts.

Thanks a lot.

Ian.M:
So now you want to test the motors/gearbox assemblies *after* they are packed? You do like making life hard for yourself.


A more rational approach would be to design a test jig as part of the production line using resiliently padded clamps with a contact microphone embedded in one of them.  It will be much less sensitive to background acoustic noise.  The tesst jig should be mounted to a heavy concrete slab on resilient mounts to isolate it from vibration sources on the production line.  If that's still not good  enough, the test station may need a sound-dampening cover, that closes over it during the test.

engineheat:
I cannot put the sound check on the line. The way the production machine is designed, it's too difficult to build a sound barrier. It's also deemed too much of a risk to put a custom solution like this to the actual production line.

Ian.M:
In that case, you are looking at an xyz gantry system.  You've still got to deliver power and control to the head so one more cable (or an extra balanced pair + grounds either side) in a ribbon cable for the output of the contact microphone preamp isn't going to make much difference to your moving cable management.

The gantry and head will be need to be retracted for good access while the guard on the machine cell is open, so indicating failed units by LED isn't really an option.  Probably the best choice would be a paint dotting system on the head for go/no-go marking, combined with a monitor displaying red and green squares + a machine vision system checking  the operator has removed the correct reject parts.  The machine vision system can also confirm the presence and correct placement of the part at each grid location, preventing expensive head crashes.

engineheat:

--- Quote from: Ian.M on February 06, 2019, 11:49:30 pm ---In that case, you are looking at an xyz gantry system.  You've still got to deliver power and control to the head so one more cable (or an extra balanced pair + grounds either side) in a ribbon cable for the output of the contact microphone preamp isn't going to make much difference to your moving cable management.

The gantry and head will be need to be retracted for good access while the guard on the machine cell is open, so indicating failed units by LED isn't really an option.  Probably the best choice would be a paint dotting system on the head for go/no-go marking, combined with a monitor displaying red and green squares + a machine vision system checking  the operator has removed the correct reject parts.  The machine vision system can also confirm the presence and correct placement of the part at each grid location, preventing expensive head crashes.

--- End quote ---

An xyz gantry system offer the advantage that one can change the movement via programming easily. In my case, since the positions of the points of interest are always fixed, would it be easier to hard code the movement along some kind of "grid-like track cover" that I can place on top of the box? This way, at least the xy movement is hard coded or at least constrained in a way that might make it technically easier. I'm not sure how hard/expensive it would be to make a xyz gantry that is of the right size for the box. On the other hand, I can easily machine a custom track out of plastic.

I plan to just use a LCD display to shows the positions of the bad ones.

thanks

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