First off, the new forum software is superb thanks for upgrading Boss!

Now... I'm working part-time in a print-shop because Job Is Job has slowed down quite a bit.

Print shop does silk-screening and pad-printing... I deal with the pad-printers.

Basically we split an image into it's color components and apply the image to the product one stroke per color at a time.

In between strokes the product can't move AT ALL. If it does horrible image related fail occurs.

We got a job from the Big Red X across town (as opposed to the Yellow K), it's a "simple" four color job, the white part says MEDIA EXPANSION PORT, then there is a funky three-color USB logo and of course the trademark Big Red X.

Problem was the part was shifting causing the USB logo to look like pure condensed fail. My task was to redesign the fixture and since I'm the closest thing to a machinist he has, guess who got to run the Bridgeport?

Using my "machinist" fu I milled a block of aluminum into shape so it formed a nest to hold the part, then I drilled out the bottom and pressed in two $20 Super Magnets. As I predicted the magnetic force held the part in the nest without shifting. HOORAY.

Enter the Boss. He looks at the fixture, looks at me printing and wants to know how I did it. He comes over and plays with it (the fixture not me) and declares "How the F$K did you magneticfy (his word) aluminum, that ain't possible!"

I told him it was a special heat treating procedure, he didn't buy it. Then I tried the "well it's actually an old Army trick" but he didn't buy that. Then I tried to convince him that it's a spray-on chemical compound that I found in the storeroom. Still not buying it.

Haven't told him yet. The fact that he can't figure it out is a riot.

that is pretty funny. persumably the magnets hidden.

Well, some people actually BRAG about the fact that they were lousy in math and science in school.

Arminius

Surplus John: Yes, hidden in the bottom. Fixture bolts to the printer and you can't remove it mid-job it'll throw the registration off and that's Very Bad.

I love it.

Did you do the trick of laying a few hairs across the fixture before leaving for the weekend so you know if someone has been in and pulled everything apart during the weekend?

You have given me an idea for the neatest tool holder: A piece of aluminum with magnets set in from the back all nicely anodized with the outline for each tool engraved after anodizing.

Not hair but I did encounter a situation where someone was fiddling with my setups so I started using a paint-marker to leave witness marks.


...can't claim credit for the magnet trick though, I've seen plenty of fixtures like this over the years just copying what I've seen.

At one point in my speckled career I worked for a large medical supplier, a lot of the time dealing with glass capillary tubing. Our main competitor was a former neighbor who had helped me a lot with things like science fair projects when I was a teen ager. When people talk about Hitler, I say that I worked for someone like that, my boss at the time, screaming tantrums, totally illogical orders, the whole bit. He flip flopped back and forth between wanting me to get into the competitor's shop and steal secrets and terror that I would give some of ours away. One day Bosso came storming into the engineering office because he had been told by a salesman that the other guys were making circa 1/16" dia capillaries from solid rods. "They must be drilling holes lengthwise in the glass rods and drawing them down to size. That SOB is crazy." Of course, they were just using rods because they could be fed into a puddle of molten glass without carrying in air bubbles. Then they were forming tubing from the puddle. The story was a deliberate plant because my friend knew that the salesman would carry tales. We had a good laugh and never did tell him.

Bill

tell him you cryo'd it so it will superconduct.

Great story Sander and well told!

Bob

If he hasn't figured it out Monday by noon I'll fill him in on the "secret."

Good story Sander.

-DU-

I would be gentle. "It was clear that you knew that even I, as a terrific machinist, couldn't make Al magnetic. And you were sophisticated enough to recognize that there must be a "trick". There is. Care to take one more guess? No. Turn the unit over."

Let him take the final steps of the journey.

"Old Army trick". Great story.

J

many years ago I designed a little automatic cutter for a vinyl extrusion that used a couple of small air cylinders and a utility knife blade cutting against a plastic block. Over the years this set up cut hundreds of thousands of pieces [maybe a million], supposibly with the same blade. The maintainance guy swore that he never changed the blade but he was a bit of a practical joker so I think he did but was just leading me on. I think maybe everyone was in on the joke but me since the " miracle blade" would come up often....

Showed him this morning when I tore the job down. Now he wants me to "magneticfy" some of the other fixtures on the shelf.

So I work in a chemistry dept shop and we do a lot of work with VERY STRONG magnets. We were goofing off on day and started running a big flat round magnet over an 4"x4" bar of 6061 Alum. When you run the magnet over the bar back and forth, it feels like the magnet is in a pan of water. There is serious drag and if you let go, the magnet seems to be stuck in the wave. I don't know why, I need to confer with someone who knows more about metallurgy. Greyson

Greyson;

The only way it has to do with metallurgy is that it has to be a metal that is non-magnetic; actually any conductive material will do. What you have discovered is eddy current damping.

When you move a conductor in a magnetic field a current is induced in the conductor; this of course is how a generator/alternator works. A current flowing in a conductor creates a magnetic field; this is how solenoids work so the induced current creates its own magnetic field. The two magnet fields intereact to oppose each other and that is what gives the drag you feel.

If you move it very slowly the induced current is low so the drag is low but if you try to move it very fast the current goes up and the drag goes up.

Actually this is the principle behind induction motors. The alternating current creates a constantly changing magnetic field and in three phase motors the way the field increases and decreases in the three sets of poles makes the field rotate. This rotating magnetic field induces currents in the rotor which induces magnetic field and the rotating field going from pole to pole drags the rototr with it.

Hdpg,

Thanks, that is cool information. I will look into this further. I am at Oregon State University, so I should be able to find more out. Thanks again, Greyson

Actually it didn't click at first that you are a chemist and probably use magnetic stirrers. These are normally a bar magnet on the end of a motor shaft with magnetically couples to your magnetic stirrer which is either another magnet or just a piece of soft iron encased in teflon. When the motor rotates the stirrer rotates (normally).

This is not due to induced currents or anything it is just straight magnetic attraction. However, if you have very shallow water in a beaker and carefully float a piece of aluminum foil on the surface tension; not really floating of course but supported by the surface tension, you can sometimes get the foil to start rotating slowly by cranking the motor up to full speed.

Sorry for the misconception, but I am a Mechanical Engineering student. I work in the shop in the Chem Dept. for experience and some extra tool money.

I figured that the stir bars used a moving magnet on the end of a motor shaft because they are usually integral with a hot plate.

Greyson

Didn't the old cable drive type speedometer use some kind of spinning magnet inside an aluminum cup (to which the needle indicator was fixed), to move the needle, and the rotation of the cup was countered by a coil spring?