FreeCAD Lesson 08 - Inner Threads

hello and welcome to another video tutorial about freecad in this video tutorial we are going to discuss how to model enough threads as an example we will have a look at a hexagon not of a size m6 and we will talk about different kind of representation so to say different kind of modeling ending up in a swept profile along a helical path and a boolean cut to get a fret like with Reds we have in real life or knots or other parts a free cat version we use here is with 0.15 stable release on the windows 7 64 bit system when it comes to mechanical engineering and we have let's say a quite complex technical machine of some sort we have a lot of nuts and enough frets on all parts but in most cases you won't see the threads because if you insert a bolt or screw or something alike the thread becomes invisible to you to save CPU performance in mechanical engineering we don't use a representation which shows an enough thread remember we talked about a 3d model showing a thread on a virtual 2d sheet of paper is something else but in mechanical engineering for freedom model we use a representation like this it's an abstract representation we have a flat cylindrical inner face as you can see here in the preview the model was done using a part design work bench in freecad we first made a sketch and revolved it the sketch contains the in a profile here it defines the eight of the screw and the two slopes the slope here and the slope here when varies a pocket operation applied to get the six phases which form the hexagon on the outer shape of the model this kind of representation is sufficient for mechanical engineering somebody doing mechanical engineering will have a look at this model and say okay we are talking about a hexagonal nut and maybe he will use the measurement tools in the C ad system to measure the width across flats here to get an idea about the size of a nut maybe he will also measure the aid of a nut to get an idea if you are talking about and not with normal aid or reduced aid but in real life this person would have to consult for example the part list to get additional information about the nut such as the material or maybe there is also a surface treatment applied to the not something like zinc plating or nickel plating of course there are a certain cases when you need an optical representation of a fret in this case you could use a model like this as you can see in the tree view the part design workbench was used for pet operation doing the hexagon faces and we also did a revolution if we look at the sketch of a revolution here you can see we have this zigzag like profile with a polyline and if you revolve this each and then do a boolean common operation well at least talking about optical representation it looks like a fret and doesn't use that much CPU power and therefore it doesn't use that much file size on your hard disk additionally there might be cases when you need a real thread with all correct dimensions for example for 3d printing then you would use for the inner profile a helix and of course some sort of a triangular sketch being swept along the helix and then doing a boolean cut on the rest of the shape to get this helix like shape I am now going to show you how to do all of the free models step by step so let's first close these documents here let's insert a new document and make sure that part design workbench is activated let's first create a sketch on the XZ plane applying ok let's zoom a little bit to the origin and in my case I chose by edit preferences display sketcher a grid size to be shown of two millimeters so each step here is 2 millimeter okay so let's start with sketch by using the polyline tool and starting on the horizontal axis let's first insert a slope like here then let's insert a vertical line here a slope in this direction horizontal line slope here vertical line let's go back in a slope to the horizontal axis and then back to your first point of our polyline if I would have caught a here V horizontal axis the solver would have shown an error message saying this point on to this axis this point on this axis and a horizontal constraint is one constraint too much but in this case everything is ok we have an under constraint sketch with eleven degrees of freedom so let's first begin with constraining our angles here according to the ISO and we now need an angle of 150 degrees we also need here an angle of 150 degrees because Dean ISO says that this angle here should be in total 60 degrees and this slope here can be Ryba tween as far as I know if I recall correct 15 and 30 degrees so let's choose 30 degrees so that this angle here is 150 degrees because horizontal line would be 180 degrees okay let's constrain this angle here to be also 150 degrees and let's also constrain this angle here to be 150 degrees let's choose these two lines here and apply an equality constraint and also apply a quality constraint on these two lines let's choose this point here and the origin and apply a horizontal constraint of 2.5 millimeters because with an m6 Fred the inner bore diameter according to Dean or to use the newer definition to according to ISO is five millimeters so the radius is 2.5 millimeters also apply to these two points a horizontal constraint of a horizontal dimension of three millimeters let's the 6/2 we apply to these two points a horizontal dimension of four point 4 comma 9 millimeters and we will pull slide a little bit inwards and apply to these two points a horizontal dimension of 6 millimeters we can then place these dimensions a little bit better for visibility and we will apply two V's two points a vertical dimension of four comma seven millimeters that's it we have a fully constrained sketch we close the sketch and apply a revolution for vertical sketch access let's say okay and we just did the first sketch correctly okay so the next operation is to use the pocket operation to get the six hexagon faces on the outer wall of the shape so let's select the face here apply a sketch to a face and let's select the create regular polygon icon to get its help in creating the hexagon so click on the icon here select the origin and let's select the point here so we have now another constraint sketch with four degrees of freedom left so let's select this point here and let's select the horizontal axis and we will fix the point on to the axis with this constraint here so let's repeat the operation with this point here we then have two degrees of freedom left so we will apply to these two points in regard to the horizontal axis a symmetry constraint and then we will apply to these two points a horizontal distance of 10 millimeters we will then insert a circle from the origin here and we will click once again here and remember that we did a radius here of six millimeter so we apply a radius to this circle of six millimeter or more let's say we use seven millimeters in this case to get an overlapping for our boolean cut which is mostly a good idea let's close the sketch it is fully constrained and use the pocket operation to say for example through all or I could use dimension of 4.7 or more remember v8 we defined with 4.7 millimeters I click on OK and we are here complete with the whole model for the first case so for the next case with cylindrical a thread which I did show you let's use a different design approach just to practice modeling and freak out a little bit more let's close this document here let's create a new document and we once more use the part design workbench and in the end we use the pot module workbench for our boolean operation so first we apply a sketch to the XY plane we do once more use my create regular polygon icon we select the origin here we click here in a empty space we'll apply a fixture constraint from this point to the vertical axis let's try what happens if we apply a vertical constraint here and we still have two degrees of freedom left so we could apply a constraint of this point and the origin being coincident this would have been the same as applying for example symmetry to these two points or these two points or these two points so we have still one degree of freedom left this is the horizontal dimension of ten millimeters between let's say these two points we closed the sketch and we pet it to a height of four comma seven millimeters we choose okay and we just completed the first step of this model okay so the next step is to draw the sketch which we will use for evolution and the last step would be to use the boolean common operation on both solids to get the resulting shape so first I'm going to select a pet here doing a right click and toggle its visibility to be able to sketch a little bit better when I click in empty space somewhere to deselect everything I will apply a new sketch this time to the XZ plane for reference just look in right down corner we have a small create with coordinate system is always present and click on OK so now we will draw once again our sweep profile our revolve profile with a polyline tool we will begin on the horizontal axis doing a slope here going vertical a little bit here do one zigzag being once more vertical here doing a second time a six egg being vertically here doing once more an exact vertically now one more zigzag and now one more vertical one last slope in watts and when we have a horizontal line slope here a vertical line slope going back to the horizontal axis and back to the first point of a polyline we have our well-known arrow in this case I'm going to remove this constraint here by selecting it and when you can press Delete on your keyboard or you could also for example do a right click here on this constraint and choose delete so the error message is now gone and we will begin to constrain our sketch so first thing we can do is select this point and this line here and apply a fixture of a point on to the object this will cause these two lines to be collinear or in line we will repeat this operation here and we will repeat the operation once more here and once more here we will tell these free inner lines to be equal or to be correct of equal length we will tell all these lines to be also of equal length we will apply an equality constraint to these two lines and we will apply an equality constraint to these two lines okay so now we will use a small geometric trick we will create a line from this point here to this point here and apply a vertical constraint to this line we will then choose this line and we will toggle a construction mode and then we will apply a fixture constraint of Reath point here on this line here we will repeat the operation here we will repeat the operation with this point here and we will repeat the operation here so the next thing to do would be to constrain all four angles again remember to choose each angle to be 150 degrees and apply here fourth angle to be 100 now we don't need a fourth one here s in this case it's it would be over constrained as you can see from the error message so let's break let's press cancel and we are done with the angles so let's then do another geometric small trick let's draw a line from here to be on the line here let's choose the line to be of construction mode let's select the line once more and apply a horizontal constraint and let's choose this point here for line and let's also choose this line here and apply a symmetry constraint so now we are left with six degrees of freedom so the next thing would be to apply this dimension here which is also regulated by Dean thirteen we apply in this case a vertical distance of one millimeter as we see ever solver overreacted a little bit so we choose to go back and we apply a constraint once more let's first beer for moment Wilfer two-millimeter that's been reduced to 1.5 very good then let's reduce to 1 millimeter now still overreacting a little bit so let's use smaller reduction steps 1.2 and 1 millimeter okay this looks perfect let's reduce we ate Vanderbilt and let's apply our first constraint to these two points here the origin and this point here let's use a horizontal constraint of 2.5 millimeters as before let's make sure what per profile looks right sometimes as it just have seen the solver overreacts a little bit and finds a different solution which is unwanted so the next thing would be to reduce here we ate a little bit and now apply a constraint to these two points our sample dimension constraint of remember three millimeters as you can see here solver we overreacted a little bit okay let's go back choose these two points apply our horizontal constraint let's be R at the moment with 2.86 let's change it to three millimeter and for some reason we are good sometimes you need to play around with values a little bit in free cat to get free cat going so the next thing would be to apply a horizontal dimension constraint to these two points off remember 4 comma 9 millimeters as you can see here once more the solver overreacted a little bit so we go back we pull this line a little bit inside okay we choose once more these two points supply constraint here and when we do a double click on with dimension and when we choose small steps to reduce to the value we like to have okay so now we need to select these two points and apply a horizontal constraint of remember 6 millimeters when we choose these two points to apply our last constraint and we apply a total line 8 of 4 comma 7 millimeters let's let me close my sketch we do a revolution we say ok we select the pad do a right click and toggle its visibility to get both shapes shown here again in the 3d view we choose part module workbench we select both of these shapes here and when we apply the boolean common operation or in other words we make an intersection of the to save shapes so now we have resulting shape here and this ends my demonstration of the second showcase for optical representation of a hexagonal nut now for the third case so to say the real fret I'll close this document here I will create a new document and I will switch back to part design workbench I will begin with the same shape as used in the first sketch so first I will apply my revolution operation and then my pocket operation so first I'm going to insert once more on V X Z plane a sketch I will zoom a little bit here I will use a polyline tool I begin on the horizontal axis and I'm doing my revolution profile once more so once more ideal eat with constraint here let's apply equality let's apply equality let's apply once more almost four angles of remember 150 degree no it was this angle here but needs 150 degrees 150 degrees and once again 150 degrees so now I'm going to apply all the horizontal constraints once more which was 2.5 millimeters this one here was free millimeters this one being 4 comma 9 millimeters oops my solver overreacted a little bit so I'm going to go one step back draw the line inwards a little bit apply once more horizontal what do you do here let's say six millimeters and when doing a double click and when correcting finally 2 4 comma 9 millimeters when I will apply here a horizontal distance of 6 millimeters and here I will apply a vertical distance of 4 comma 7 millimeter and then I will do the revolution once more and so we are done with our first step and now I will choose a pocket operation so I select the face here once more I'm doing my sketch doing a hexagon sketch let's say this time I apply a fixture to this point on V vertical axis I apply here once more vertical constraint I do apply a coincidence constraint on these two points and I'm applying here a horizontal distance of 10 millimeters I will then need my circling site at the origin and let's say we have a circling once more of seven millimeters radius to be sure to have an overlapping profile here we close we apply the pocket operation through all and now we all have our basic shape and we are now able to apply our hallux sweep and when our boolean cut on this shape here okay so for the next step we switch to a part module workbench and we will create a geometry primitive we choose the hallux we want to have a pitch of one millimeter that's okay we want to have a total of more than 4.7 let's say we want to have to be real sure six millimeters complete eight and we want to have a radius of let's say 2 comma five millimeters we leave the angle at 0 degrees and right hand it is okay so we create V Alex and now we close this dialogue here we select the pocket shape and we targeted specifically to be able to draw a little bit better when we switch back to a part design web bench and we apply a sketch to the xz-plane say okay we do zoom here and then we will draw a triangle with its let's say base point on the horizontal axis having here are a vertical line and going back to my first point so now we have to apply equality constraint to these two lines we have to apply an angle of 60 degrees and we have to apply a horizontal dimension of well we want to have an overlapping so we apply a little bit less than 2.5 millimeters so let's try it with two point or two comma point to two gamma 4 millimeter to be real correct and this here should get the horizontal distance of three millimeters and that's it we have fully constrained sketch we closed the sketch and then we go back to a part module workbench we click an empty space to make sure to have everything be selected and we choose the utility to sweep we want to sweep sketch 0:02 we click once more here in empty space and a sweep path we select we do a multi select a tube to then press control on the keyboard on windows in this case and we select all these segments here say done we want to create a solid and we want the beginning face and the end face to be coplanar so we select the Fred an option we click on OK and visit our swept profile we talk about visibility or for not here and then be select the pocket and then the sweep a shape and then we apply a boolean cut we can toggle the visibility of three Alex and as you can see the sketch is also visible we talk about visibility of a sketch here and here we go this is for complete Fred with everything made since you may encounter a problems in 3d modeling so to say you may encounter situations where boolean operations especially boolean cuts will fail so let's talk a little bit about troubleshooting in 3d modeling for talking about troubleshooting we have to talk a little bit about the background of 3d see ad with your personal computer you need a basic operation system to run it this could be one of the different versions of Windows or Linux distribution of your choice or one of the products from Apple with 3d see ad you also need a basic software it is called kernel there are a well known see ad kernels on the market of course commercial ones speaking of licenses the biggest free are the Katia kernel the step kernel and the Asus kernel whose native file format is SAT free cat is set atop on as far as I know the only existing open source 3 DC ID Colonel open cascade Colonel or in short OCC this kernel provides free care the ability to do 3d operations it's providing whenever needed mathematics and geometric a basis to do that as our technical products it has some limitations and sometimes you need one or two let's say small tricks to get everything going so the best advice is if you're doing boolean cuts be sure to have overlapping geometry coplanar faces are not very good for boolean cuts it may work but the operation is also quite likely to fail a second trick would be to use part primitives instead of revolve or extruded profiles at least with earlier free versions of freecad I was thinking that free cut or these the geometric kernel was reacting more robust when doing boolean operations with primitives rather than revolved or extruded profiles I also encountered one time a situation with an earlier version of freecad that occ so to say the geometric kernel didn't seem to like the fact that the hallux and a profile to be swept we're lying on the same plane so in this case we XZ plane asthma revolved profile which was responsible for the outer geometry so in that case I applied we are placement a 90-degree turn to the hallux Andrus we profile so the hallux and miss be profile begin on the Y Z plane and suddenly the boolean cut worked this would be another trick you can use another trick would be well a little dirty one we are talking here about mathematics if free - free is zero well when we have to cheat a little bit so maybe you could have success with a boolean cut if you do a shift for position of one of the two solids you want to cut by a very small amount let's say one thousandth of a millimeter in real life this is in most cases beyond all accuracy of milling machines measurement tools and even beyond normally all accuracy of 3d printing but shifting positions a B a placement for example of one of the solids by one thousandth of an millimeter will result in a mathematic result of not being zero and so maybe the boolean operation will succeed in this case so with these tricks for troubleshooting we have reached the end of today's lesson I hope that I showed some new things and what you did learn something feel free to leave any comments here on youtube and mel maybe see you in another video bye

Channel: Learn FreeCAD

Views: 118,076

Keywords: CAD, 3D, Open Source, FreeCAD, Tutorial, Windows, Linux, OSX

Id: Y5b1FUEfAFw

Length: 45min 31sec (2731 seconds)

Published: Tue Jun 23 2015