Using a history stack in CascadeStudio

[raydeleu]

I created a small part to repair the interior lighting of an old FIAT Panda. The part is not very interesting, but I experimented with encapsulating every modeling step into a function. This allows to use a kind of history stack at the bottom of the code. Just like the modeling history in many CAD programs you can go through each step backwards by putting comment marks in front of each step. In the CascadeStudio editor you can achieve this by selecting the lines you want to be marked as a comment and pressing [CTRL] +[/].

// Small part to repair the cabin lighting of FIAT Panda

// dimensions 
let hTot      = 16;
let hInn      = hTot -3;
let hMax      = hTot - 6 ;
let hMin      = 2;

let dTop    = 3.5;
let dMax    = 6;
let dMin    = 4;

let tInn    = 1;
let tMax    = 2;
let tMin    = 1; 
let tBase   = 2; 

let wTot    = 17;
let wCut    = 10;

let p0 = [0,0];
let p1 = [0, hTot]
let p2 = [dTop,hTot];
let p3 = [dMax,hMax];
let p4 = [dMin,hMin];
let p5 = [dMin-tMin,hMin];
let p6 = [dMax-tMax,hMax];
let p7 = [tBase+tInn,hInn];
let p8 = [tBase,hInn];
let p9 = [tBase,0];

function DrawSideView()
{
// sideView
let sideView = new Sketch(p0)
.LineTo(p1)
.LineTo(p2)
.LineTo(p3)
.LineTo(p4)
.LineTo(p5)
.LineTo(p6)
.LineTo(p7)
.LineTo(p8)
.LineTo(p9)
.End(true,false)
.Face(true);

return sideView
}

function ExtrudeSideView()
{
// extrude side_view
let holder = Extrude(sideView,[0,0,wTot]);
return holder
} 

function CreateCutter()
// create boxCutter to create 2 separate springy arms
{
let wBox = wCut;
let dBox = dMax;
let hBox = hInn;
let boxCutter = Box(dBox,hBox,wBox);
boxCutter = Translate([tBase,0,(wTot-wBox)/2],boxCutter,false);
return boxCutter
}

function CreateHole()
// add hole for screw
{
let hole = Translate([0,hTot/2,wTot/2],Rotate([0,1,0],90,Cylinder(1,10,true)))
return hole
}

// Model stack
let sideView        = DrawSideView();
let holder          = ExtrudeSideView();
let boxCutter       = CreateCutter();
holder              = Difference(holder,[boxCutter]);
let hole            = CreateHole();
holder              = Difference(holder,[hole]);

Here is the same shape create in OnShape. At the left you can see the feature list or rollback bar that is almost identical to the model stack in the CascadeStudio code.

I think that the concept of this modeling stack is very practical, in particular if you happen to change the model in such a way that the numbering of edges or faces changes. In that case you have to adjust the parts that reference these edges or faces. Using the modeling stack it is relatively easy to go back to a certain state of the model and determine the correct numbers.

An issue that I still need to solve is the creation of sketches. Currently I do this using a paper notebook or using a tool like SolveSpace. After creating the sketch in SolveSpace I export the sketch to an image, number the points/vertices around the contour of the sketch and then determine the values or equations (relationships between dimensions) for each point. The benefit of the modeling stack is that it is easy to go back to the creation of just that sketch in CascadeStudio and determine the effects of changing dimensions.