Mysterious Screw
 

Hello all,

We're doing a physics project and I "borrowed" this screw from our team as we have never used it before and have no idea what its use is. So, now that I've shown off the "uber-neat-screw" to everyone, they all want one. Does anyone know what this is called and who makes it?

Thanks
-Tanner

Re: Mysterious Screw
 

that is called a leadscrew. If that one was from a team from a previous KOP it was made by Kirk Motion http://www.kerkmotion.com/products/l...lead-screw.asp

you can also get them at mcmaster car www.mcmaster.com

Re: Mysterious Screw
 

The function of that part is to keep one student occupied playing with it during the entire build season. It doesn't have to be the same student all the time, they can take turns.

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i have one of those on my hobie cat, i have no idea what it does though, so i leave it alone:yikes:

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Can't you connect one directly to a motor and use it to open and close claws and mechanisms of that sort?

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Actually, the primary operators of this device should be those who cannot land the lead position for "Time Waster", whose sole purpose is to use the Igus track throughout the entire season.

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Team 79 used one this year to raise and lower our scissorlift.

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An awesome device used like crazy on all sorts of machining tools and other great things.

Lead screws FTW!

Re: Mysterious Screw
 

Sweet guys! Thanks for the info.

Cheers
-Tanner

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i know that team 103 has used them last year on their robot, to raise a section of their robot up to knock off the track ball.

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Be careful with those lead screws! They apparently have extremely sharp ends that like to cut fingers when trying to spin it. I managed to get a cut from the bottom of my index finger almost to the tip, it wasn't too pleasant :P

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Gee... I can't believe all these teams that let the students play with their leadscrews and IGUS e-chain track... I thought those were to keep the mentors busy!

I also can't believe that no one has mentioned the coolest part about the leadscrews... you will note that they are quad-start (look at the end of the screw and you'll see four "bumps"). That means that there are actually four seperate "threads" twisted around the axis of the screw as opposed to just one for a standard "single start" bolt or screw. That is why the nut moves so quickly.

It moves so smoothly because it is magic.

Jason

Re: Mysterious Screw
 

Our team used two of the lead screws to make each side of our chassis expand out. They were actuated by Globe motors. It worked pretty well for us.

I believe some of the teams with launchers used them to pull back their spring-loaded actuators.

Re: Mysterious Screw
 

Even cooler than lead screws, in my opinion, are ball screws. They perform the same function as lead screws, but instead of relying on surfaces sliding against each other, they have lots of ball bearings inside (and a mechanism for recirculating the balls between the bottom and top).

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So do ball screws do anything better than a lead screw? Or was it just another case of an engineer with to much time on his hands and to many resources? (Creepy Thoughts)

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Ball screws have been used in automotive steering gears for the past 50 years or so....

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Ball Screws have less friction and maintain a lot higher linear tolerance than lead screws.

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They can also handle a heavy load with marginal lubrication.

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Hmm, your team is organized different then mine... I always thought the head time-waster got the screw, and the assistant was stuck with the track... especially considering we actually used the track this year!

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you will find lead screws and ball screws in machines such as lathes and mills.
they are both do there job very well as for which is better it depends on what you are doing i have been told that for mills and lathes if set up right ball screw tend to be more accurate but u can get real accurate lead screws as well.

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Lead screws can be made exceptionally accurate. Moore Tool developed jig boring machines that are very accurate and they used lead screws. Richard Moore has been recognized as the man who "gave the world’s industry an additional decimal place of accuracy!"

His son Wayne wrote the book "Foundations of Mechanical Accuracy".

I don't know what they use these days, but they have jig grinders that will position within 90 millionths of an inch in 18 inches of travel.

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From what I hear, on team 829 the Head Time-Waster becomes the Lead Button-Maker.

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Ball screws provide less friction in the mechanism, and you could find them at the end of older vehicles and truck steering columns before rack and pinion became the norm.

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As a warning: MULTIPLE leadscrews are a MUST for any build team if you have too many freshmen. Just tonight, in fact, we had a minor argument over who's turn it was to hold the "cool screw thing."

We've never used it, but it is notorious for being either the the most useful or useless thing in the KOP. Come to think of it, didn't 330 use it in 2007 inside their arm to activate their claw?

EDIT: Nevermind, that was pneumatically actuated.

Re: Mysterious Screw
 

Hehe, I found one application that I think I need it for.

Need help with this. So for robotics, I'm creating a simple manufacturing workcell that autonomously places sheets of aluminum into a dye and then pneumatics come down to just bend the sheets. What I wanted to use the lead screw and a motor for is to have a custom made vice run on a bed (much like a vice would on a mill) to come forward and make sure the sheet is positioned correctly but I don't know how to set up the lead screw to do this. Also which motor should I use to have the sheet of metal positioned quickly using the vice and screw? Thanks, any help would be appreciated.

Re: Mysterious Screw
 

330 hasn't used one on a competition robot since 2002. Then they used two small ones...and come to think of it I'm not even quite sure they were leadscrews. I do know they came out of a gearbox that we haven't gotten since then.

The leadscrew's only function other than wasting time is to turn rotational motion into linear motion. While it is theoretically possible to go the other way, reality wins and it's pretty hard to do so.

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But you can have fun with the concepts of friction and angles by figuring out just how steep the thread angle has to be to keep it from backdriving.

The fancy coating, low friction plastic nut, and multiple threads make it so that the KOP lead screw can indeed be back driven, but normal nuts and bolts can't.

Re: Mysterious Screw
 

First, Pneumatics are not a good choice for bending metal, you cannot get the power required. Hydraulics are the better choice. But, that's not your question.

To use the leadscrew as a positioning element, you first need to create the system that drives the leadscrew - for example a window lifter motor. Then, you need a system to know the exact* position of the nut on the screw. Using a PID loop, you drive the motor until it is in the desired location.

*Exact is relative. 0.001" is hard to do with a quadrifilar leadscrew, 1/8" should be possible.

For repeatable. low-load positioning, you should consider pneumatics. Use an adjustable end stop on your mechanism to set the exact spot to push the material to. That also actuates a switch, which makes the hydraulic press come down onto the die and do whatever you want. Then another thingus comes up and pulls the workpiece off while a new one is being put on.

Re: Mysterious Screw
 

take a look at the 2016 robot when you get a chance... we will post more details when we get to competition.
you can also take a look at 2753's arm as we have a joint effort here.

That lead screw is an integral part of our design and it works amazingly well.

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Large versions of this little screw are used to adjust position on satellite dishes all over the world. I work with one dish that has a lead screw for elevation and it is connected to a 3/4 HP motor with an electric brake. The screw is about 4' long and at least 2" in diameter. Another dish that is much larger has two, one for azimuth and one for elevation. Both can be operated by a hand crank or electric drill attachment. The dish is 6 meters in diameter.

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1625 has used leadscrews very successfully in the past. In 2006 it was used to actuate the hood on our turreted shooter and in 2008 it was used to bring our shooter from pick-up to shooting position.

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The dishes I worked on way back when used gear drive...10 meters with a pretty heavy equipment room attached to the az drive....

If you ever get the chance to peer into the workings of a 1957-59 Ford Retractable car, you can see several lead screws. An engineering marvel.

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6 motors too

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Jim,
Our old 10 meter C band dish had manual adjustments for azimuth but luckily was a polar mount. As I remember, the lead screw transmission had another right angle gear reduction box on it. It moved exceedingly slow. We only had to aim once when the main PBS satellite reached end of life and we had to reposition.

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I guess that X band stuff was more finicky about where you point the antenna...or it was just that some of the birds were about out of gas and moved around a lot..but our tracking systems ran full time

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Because after a day of cutting out circles with scissors your hands are so cramped up you cant operate the lead screw anymore.