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BillSlugg
09-11-2008, 10:24 PM
[From Introduce Yourself thread (http://forums.trossenrobotics.com/showpost.php?p=20052&postcount=293):]
I want to devise a machine that will grind complicated curves and angles. The work holder will have one degree of rotational freedom. The grinding head will traverse in x, y, and z plus will rotate about x.

I am a complete newbie to microcontrollers and was looking for a place to help me get started. Adrenalynn convinced me to come on over and join. I am a little apprehensive though. I have looked all over this site and I do not see any vacuum tubes. Have I missed something since I graduated?

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Thank you all for your kind words.

I envision putting a 2" dia by 6" long end mill between static centers. I would loop a small toothed belt around it and tension a stepper motor. The grinding head is much larger, probably 80 pounds, and the resistance to linear motion is considerable, probably 10 pounds. I am going to have to fab up a smaller lighter grinding head.

One option I might consider is to move the grinding head by hand, and have a linearly variable displacement transducer tell the stepper motor where it needs to be. I have tons of pots taken from military equipment. 0-10K over ten turns. I'll just tie a cord to the carriage, run it over a pulley on the pot and hang a weight on the end. As I move the carriage, the spiral end mill will rotate just right. All of the other motions can be done by hand, that is angling the head just right, advancing the wheel due to wear. I am sure I am going to need fudge factors for dead band and hysteresis.

I ordered my Arduino starter board today. I will need some time to get proficient with it before I start cutting metal. The last electronic gizmo I made was a two transistor flip flop randomizer in 1965 from plans in Popular Electronics. Although my degree is Electrical, my career was spent in fluid dynamics and heat transfer. It will feel good to be back in the electronics game.

Adrenalynn
09-12-2008, 12:42 AM
Bill, feel free to edit and change the title of the thread. Please let me know if you aren't able to!

Here's the discussion leading to here from the intro above:


Sounds like a job for stepper motors. You'll need five -- one for each degree of freedom -- and you'll have to spec out how strong they need to be and how accurate they need to be. They are discrete devices that turn in fixed fractions of a circle per step, typically between 3.6 degrees (100/circle) to 0.5 degrees (720/circle). You can also get gearhead steppers that improve both torque and accuracy.

Can't help you much with the controller side as I'm a newbie there too, although I'm pretty good with tubes, as long as they are tubes full of liquor. Welcome!


Bill

How big are the grinding heads? How big are the parts your grinding? Just to get an idea of what your looking for.

Paul


You should totally talk to Matt Bauer and read his article in robot mag.

Welcome to the forum by the way...

DB