How to Design a Rack and Pinion Assembly in Fusion 360 - Part 1

hey guys Vladimir here with desktop makes I thought I'd do a tutorial showing my design approach and techniques I use to create this spur gear assembly here so I've got a few projects in mind that are going to be using this mechanism and I thought I'd start with sort of this basic approach here on how I designed The Spar and the rack here and my approach to getting them to align so perfectly so in this video we'll take a look at that and in the next video I'll show how I was able to apply of motion you see here uh using joints and motion links so all right we'll get started and first thing actually I want to show is that I approach this design using components so here uh we've got our base and our spur gear and then our rack here I think you're going to find this model very fun to design and 3D print and also highly educational let's Jump Right In we'll Begin by creating a new design and here instead of starting with a sketch we're going to go ahead and start by using a gear generator right under the utilities menu here and we can go to add-ins and then script and addin we'll get this dialogue box and if you scroll all the way down we'll see our python spur gear generator we're going to click run and you'll get this dialogue box here now don't be overwhelmed if you see all these terms here that you may not grasp the full meaning of I'm no mechanical engineer here and actually my approach to this was just to kind of play around with the numbers and see what happens sort of a trial and error here so the way I started is I looked at this pitch diameter and I have a pitch diameter in mind of the size of gear I want to make so I started experimenting with the numbers here to see what affects that parameter there now you can't directly change pitch diameter you just can only affect it by changing these other parameters and I found that the two that affected are the number of teeth and the module so number of teeth 24 sounded good to me module I brought brought that down to two and that went from a 3 and something pitch diameter to 48 mm all right that looks good except I've got this sort of message here and I can see my okay button is grayed out so let's look at what that message says it says the root fillet radius is too large it must be less than 1.18 no problem I can make that happen fillet radius going to change that to one now the rest the gear thickness you can make that whatever thickness you want I'm going to leave it at 12.7 not sure if that's sort of a default gear thickness or what whole diameter I'll just leave it the same as well you can always change this by creating a sketch and extruding anyway but I'm going to not complicate things leave everything else as is and click okay and there we have it my gear right there on the origin there centered on the XY plane and this orientation I can move it if I want but I'm just going to leave it as it is and you also one thing I want to point out is that came in as a component so you can see the little component symbol there and if I expand it you see you've got your own bodies and your own sketches and the cool thing here if I go down to the timeline and I click the little plus button you can actually see how this component was made with that python script so here if I just walk through the timeline we've got a couple sketches there an extrusion a second sketch here and this sketch actually shows the profile that was made to create the tooth of the gear so here we see it's uh generating a bunch of spline points to create that profile and then the next item here is extrudes it up and we have a fillet and a circular pattern and then our final sketch here shows that pitch diameter circle here we at 48 mm so I just wanted to show that here just in case you were curious of how they made this and you kind of wanted to see an approach on making your own okay that's that I'll collapse that timeline there and now we'll create our next component here which is going to be our rack to do that I'll click on the top of my browser here select new component and give it a name we're going to call this one rack and then we're going to orient to a top view here as we're looking at it from our view Cube orientation and I'm going to right click go to move copy I'm going to select the translate option here move object is set to bodies I'm going to select the body and I want to move this down a certain distance now how far do I want to move it down well this is very important because this is what's going to determine whether the two gears mesh or in this case the gear here in my rack so the answer to that is you want to look at what that pitch diameter circle is here let me cancel out of the move copy for a second and it's very faint but if we have it turned on even though that component is not active we're in the rack component you can see it right there and click on it it's that dashed line here and we can see the diameter is 48 mm all right so that tells us that we want to move down 48 mm because anytime you have two different gears no matter the size as long as you get that pitch diameter circle to be tangent the gears will mesh so again I'll pull up my move copy by right clicking I'm going to change this move object to bodies selection is going to be my body here and I'm going to choose the translate option create copy I'm going to make sure that's activated or enabled and I'm going to move this down I can just go ahead and type it in right here Nega 48 mm and I'm going to click okay now I'm going to go back to that gear here I'm going to activate that component and I'm just going to rotate this so that it looks correct um the important thing here is at this bottom gear that this tooth over here is going to be facing straight up but just so that it looks right I'm going to right click go to move copy and I can rotate this by clicking on the body here make sure I have body selected my move type is going to be rotate axis of rotation I can select any one of these circles here I'll go with that inner circle and now I can can start moving this to give me a rotation now I can eyeball it but you don't really want to do that you want to be as precise as you can get like I can see that that kind of works um so we want the exact number here and how do we figure that out let's back up for a minute and I'm going to explain this because to me this is something I find really helpful um so I'm going to go under the assumption that you may find it helpful as well now you may be a math Wiz but not all of us are and I am certainly not one of them so I have to kind of think of the rational steps to slowly step My Mind through how I can approach this and so that it makes sense versus just like oh what's the formula do this because I find memorization to be useless okay so the question I need to answer is what is the precise angle I need to move this and the great thing with Fusion 360 even if you're not kind of sure of the math you can just figure it out by measuring so let's go ahead and create a sketch now here I have the spur gear component activated I'm going to create a sketch sketch on that uh surface of that gear and so basically what I want to know what's the angle to move this gear one to over all right so what I can do is uh project in two points I'm going to hit P for project specified entities is selected and I'm going to click on two corresponding points on different teeth so this point right here if this tooth is moved all the way over one step it would be the same point here I'm going to click okay and I'm going to draw a line from the center origin here to that first point and then draw another line to that second point and if I hit D for Dimension I can click on both lines and I can see that that is 15° perfect that's all I needed there and the other way if you just want to use math to do this you can say well okay if I take 360° which is a full rotation here and I divide it by the number of teeth that should get me that same angle right CU you take that angle times it by the number of teeth you should get 360° so in that case we can do the math I'll take 360 / 24 which will equal 15° so perfect the math checks out wanted to show the two approaches there because um sometimes we can just get overwhelmed by the numbers in the math but you know if you just kind of rationally step through it and just think of the problem and use the tools in Fusion you can work out the steps that you need to get there and it's okay it's perfectly fine if you just have to kind of measure it first to understand it and then uh arrive at the whole oh it's just you know 360 divided by number of teeth that's how my brain works okay so I'm going to click finish sketch here okay now that I know the angle I need to rotate this I'll right click go to move copy again move type is body selection is going to be my gear I'm going to choose the rotate option select that inner circle and I can start twisting it now remember 15 degrees if I do 15 degrees here it's going to go one full rotation which is really not going to help me I have to take half of that to get it to go in between the two teeth there so half of 15 is 7.5 and enter and there we have it okay a valid question here would be wouldn't I want a little clearance here um between the teeth so they're not you know grinding um yeah you can do that you so instead of moving this 48 maybe I would move it down 48.2 mm give me a slight clearance but to be honest I was curious and just tried printing it out with no clearance and it worked fine the gears weren't getting stuck or grinding so I'm just going to keep it as is here but remember you always have the option if you need to to space that down a little more to give it a little more clearance and I would probably start with like2 mm okay I think I'm going to stop there for now I can see that a full tutorial of the entire assembly is going to take quite a bit longer than I anticipated so instead of making one really long video I think I'll go ahead and break this this down into a multi-part series so next week we'll look at creating uh or jumping into that bottom gear there that bottom spur gear and we're going to isolate this one tooth here it's the only one that's facing vertical right so we'll look at isolating it and creating a rectangular pattern of it so that we can create our rack here and also talk about the math involved to get the spacing just right so stay tuned for that I'll upload that video in a few days in the meantime if you enjoy this type of content make sure to check out the additional resources I've linked below including links to my online courses I also do a weekly live Fusion 360 class that you can join or if you simply enjoy this type of content consider becoming a patreon member all right guys I will see you in a few

Channel: Desktop Makes

Views: 7,479

Keywords: learn fusion 360, Autodesk Fusion 360 Tutorial, fusion 360 help, fusion 360 guide, 3d printing, fusion 360 for 3D printing, 3d modeling with fusion 360, 3D design with Fusion 360, fusion 360 tutorial, Fusion 360 for beginners, best cad software, learn cad, learn 3d printing, desktop makes, gears in Fusion 360, fusion 360 rack and pinion, Fusion 360 how to align gers, Fusion 360 joints

Id: laBmk4ksrmg

Length: 11min 0sec (660 seconds)

Published: Mon Oct 16 2023