The Geneva Mechanism

what does a Swiss watch film projector and CNC machining Center have in common this odd-looking mechanism is date we'll be discussing what it is how it works and why you know exactly what it sounds like let's get started just before we get started I would like to say that this video is brought to you by the great courses plus and can go to the great courses plus for splash makers muse to sign up for a free one-month trial today this is the Geneva driver gear mechanism that translates continuous rotational movement into indexed intermittent movement it's one of the earliest of all intermittent motion mechanisms and derives its name from its use in Switzer's in the 17th century however it's entirely likely that similar mechanisms were in use from a much earlier period the mechanism consists of a pin which rotates in a slot of the driven wheel and pulls it one step forward before the circular portions interact and lock the movement for another rotation of the drive wheel the driven wheel has a highly unique look to it which is what drew my attention to this mechanism in the first place and you can have from three to around 18 indexed location or known as also known as the Wells only driven wheel and when designed with Ford Wells you can see how it gets its other name the maltese cross mechanism so i drew this in fusion 360 you can get the 3d printing files here on the card above and i'll be making a video in future on how i drew it it's actually fairly straightforward but you do need to use a lot of constraints within fusion 360 to draw properly so there are several forms perspectivism can take with this external drive wheel being the most popular another variation is the internal geneva drive and the funky-looking spherical geneva drive with the added bonus of translating the motion at a right angle it's also another variation color Geneva stuff which is very similar to the external drive however then it will stop at a certain point and be prohibited from rotating any further this was used in watches to prevent over winding of the spring mechanism so what's so special about this mechanism you might be asking well despite it's fairly simple nature it actually accomplishes a movement purely mechanically that quite useful in many industries let's take a look at how it operates using this cordless drill the drive pin engages and moves the driven wheel over one stop however it's not a smooth linear movement between each dwell like you might expect but it's actually instead quite violent in terms of the acceleration curve which looks along the line of this it flicks the driven wheel over so fast in fact that when you're spinning it with a drill at roughly 400 rpm you actually can barely see the transition between each 12 period which is pretty crazy actually it's this behavior that found in Geneva mechanism widely used in early film projectors where it was used to quickly advance the film between frames leaving each exposed for a set period of time remember at the start I said that you know the sound of this mechanisms well it's true almost everyone knows that old timey clacking sound associated with old-fashioned film projectors and so what about CNC machines well accurate indexing of the tool change carousel is a must for fast pre-programmed tool changes and many older machining centers make use of a huge Geneva Drive to safely and accurately index each new tool into the spindle we need to at all change as you can see in this video and also pretty much guarantees that this mechanism would has found use in military applications but I couldn't find any specific example so let me know in the comments if you know of any I'd certainly like to hear all about it so you'll notice I mentioned old film projectors and older CNC machines well it's a pretty good reason for that you see despite the Geneva Drive being a really cool and simple independent motion mechanism has some pretty huge downside some of which you might have already noticed starting with we're so unlike eight gears mechanism where the motion components roll by each other this mechanism consists almost entirely of sliding contact the pin slides into the slot and the dwell cycle has a cylindrical faces sliding across one another so can you imagine how much friction and heat will be involved in one of these spinning at several hundred rpms for hours days or even years of operation because of this geneva drives are known to wear out very fast however it's similar to cans in your engine you can protect them using oil in fact projectors used to encase the entire mechanism in and in an entire enclosure full of oil so the entire matrons was always coated with oil to help prevent overheating and undo wear however even with this it often fell quickly and the movement relies on high precision as well so any anywhere would actually lead to premature failure quite quickly as you can see with this mechanism if I rotate this part here and I put some weight here it starts jamming up another huge disadvantage depending on application is the acceleration and deceleration curves mentioned earlier this means these drives vibrate hugely under operation and make Heckman noise - at higher speeds so in most applications you probably want a smooth transition between each dwell cycle and there is actually patents detailing attempts to modify geneva mechanisms to make them more accurately provide this but the popularity of this mechanism is definitely not what was twenty to thirty years ago and that's just because of modern automation technology you can easily control movement precisely now using low-cost servos or stepper motors just as you'd find in your 3d printer there's no need for an elegant mechanical solution so that's the Geneva mechanism guys a gorgeous elegant and outdated solution for intermittent motion and next time you hear that film projector sound you'll know exactly what made it I think thanks to the great courses plus sponsoring this episode on maker's news if you enjoy learning you think in incredible detail which you probably do if you follow this channel then you'll love the content on the great courses plus the great courses plus is a subscription on demand video learning service which provides you with unlimited access to over 7,000 top-notch lectures and courses from top professors from the Ivy League and other great universities globally as well as experts from places such as National Geographic and the Smithsonian if you enjoyed this video then I highly recommend checking out the 36 part lecture series on the Industrial Revolution taught by Professor Patrick alert in lecture 14 he discusses the creation of tools that drove the machines that then drove the Industrial Revolution I found the entire course hugely inspiring for this video for example who made the machines that made them nuts and bolts to make the machines that's the sort of stuff I like to know to head over to the great courses cluster komm splash makers needs to start your free one-month trial today and I also leave a link in the video description and it helps support the channel as well so I can continue to bring you content like this in future if you want to see future 3d printing projects tutorials and more mechanisms then be sure to subscribe to makers muse my name is Angus I look forward to seeing again very shortly happy printing guys by December

Channel: Maker's Muse

Views: 4,400,079

Rating: 4.7532706 out of 5

Keywords: 3d, printing, geneva mechanism, intermittent motion, mechanism, intermittent, history, what is, geneva, maltese cross, star, gear, 3D Printed, tutorial, fusion 360, 3D design, model, demonstration, maker's muse, makersmuse, angus, deveson, australia

Id: Le-PVXUCl0M

Length: 7min 16sec (436 seconds)

Published: Fri Jul 28 2017

Reddit Comments

[u/yetiwizard]

I watched a heap of this guys videos the other day, love them made me want a printer

[u/HanoverWilliam]

kakakakkakakakakak

-the sound lol