How to use Variables and Equations to Design in FreeCAD|JOKO ENGINEERING|

welcome to this video I'd like to go over making dimensions with variables and equations in freecad this is particularly useful when you have multiple features that you want to have a shared dimension with for a design intent instead of updating them one by one you change one number and they all update automatically I want to start by going to part design from here we can start by making a new document creating a body and now that we've created a body I want to divert to the spreadsheet workbench and creating a new spreadsheet clicking on that button did not look like it did much but we actually have a spreadsheet added into our history tree now so if I double click on that I can start creating variables I don't necessarily need to create names but it sure helps the user interface especially when you go to edit in the future so I'm going to add in a few names here width length and then maybe thickness and over here I can start giving values maybe 6 2 and 1 and now I can actually assign an alias to the cell which essentially makes a variable i right click on the cell and say properties and Elias and I say width I'm doing everything in lowercase for a just more simple way of doing it so with properties alias and length and properties alias thickness okay so the cell turns yellow to acknowledge that there is an alias I may want to work with my spreadsheet and my model simultaneously and that's pretty easy to do I'll close the start page tab down here and say windows tile and that way the start page doesn't title with everything else I might want more real estate for my model so I'll scoot my spreadsheet down as small as it will go and I can have a little bit of overlap with my graphics display window just like that so heading back to the part design workbench and I've already created a body so we'll go to model and on my body I'll create a sketch on the XY plane and I can scoot this window over a little bit I'll create a rectangle and then I'll choose a construction polyline and this will of course help Center up that rectangle now I can choose equal with the e key and select both again and choose parallel now it's time for dimensions so shift H I can give this a horizontal width but instead of just typing in a number I can choose this little button here it looks like it's got a sine wave going through it and I can say spreadsheet just scroll down and spreadsheet notice there's a period there so spreadsheet dot width is referring to the alias now I cannot say enter because if I just say enter and okay and whatever no I guess I did accept it usually the variable I have to actually click on it in the drop down menu so there are times when if it doesn't work for you for some reason just click on that width and then it should go through and notice it jumps right to that six millimeters control I'm sorry shift V and I'll do the same thing spreadsheet dot and then I'm gonna say length and there we go and it jumps to the dimension that I gave it now I'm fully constrained so I'm gonna close my sketch and under tasks I'll choose pad and notice it gives me a distance already but I can click on that little sine wave and again spreadsheet dot thickness okay and it goes to the thickness that I've specified of one millimeter and from here I can choose symmetric to plain so that it extrudes on the center now if I want to change something in the future instead of trying to edit a sketch I have my spreadsheet open I can say oh you know make it six by four and it automatically adjusts and I can say make it six by six by 0.05 and just by typing in these numbers this updates automatically and robustly so that in itself is a design treasure let's say that I want to have a hole in this face and have the hole be 1/10 1/10 of the total area of this face we can certainly do that as well I can add in the the word area and then I can say equals b1 times b2 and that is just like in Excel there we go I forgot to say that this is case sensitive so use capital letters when referencing these cells we have an area of 24 and I can say we want this to be a tenth of the area so we'll say area divided by 10 and I can say equals b5 divided by 10 and now we've got an area of 2.4 so then I just need to figure out the whole area now this next part gets a little bit tricky just because of the syntax of course we're solving for a radius we have the area that we want and we're asking ourselves what radius and so when when we do the equation we have to solve PI R squared equals a for the variable R and that comes out to the square root of the area divided by pi and so we're going to say SQ RT but make sure that that is an all lowercase s QR t is lowercase if you have any capitals in the s qrt you will in fact all do it up here so it's a little bit more visual equals s QR t and then of course our cell reference is going to be a capital b and it's going to be six and then we're going to divide by PI which is lowercase P I and there we have a radius 0.87 so I can say radius so we're going to say we're going to right click and say properties Elias and then again keeping with my lowercase convention our ad IUS radius okay so now I can sketch on this face and making a driving dimension I'm going to constrain it right in the center and now I'm going to choose our shift our rather for a radius and as we as before spreadsheet dot radius and now our radius is 0.87 and we have a hole with the radius of 0.87 we'll go to tasks and we're going to pocket through all now when I actively update the dimensions of my face the hole will automatically resize so five six s if I say 6x6 the hole becomes slightly different if I say ten and in fact let's do something crazy 100 by 6 that might make the hole a little bit larger than than what we want it looks like though hundred wouldn't rebuild properly so as you can tell as a as I make this wider the hole becomes larger if I say this has a width of two that hole becomes very small so we can compute all these different characteristics autonomously and update autonomously so you can see what an immensely powerful tool that this is a free CAD and also how easy it is to use so kudos again to the developers of free CAD I am in awe as to how wonderful of a software that they've made I hope this video was helpful and if it was please subscribe and I'll see you in the next video [Music] [Applause] [Music]

Channel: Joko Engineeringhelp

Views: 42,627

Keywords: joko, engineering, help, jokoengineering, engineeringhelp, ACADEMY, jokoengineeringhelp, tutorial, how, to, howto, engineer, JMT, EXPLAIN, EXPLAINED, GOENGINEER, KHAN, modeling, design, use, equations, variables, FreeCAD, spreadsheet, hole, square, rectangle, geometry, formula, math, dimension, size, open, source, workbench, part, model, solid

Id: Jze6ftGc6BQ

Length: 10min 25sec (625 seconds)

Published: Sat May 11 2019