Scripted Parts: Ball Bearing - Part 1
|Part Scripting - Ball Bearing #1|
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This tutorial is meant as a beginner's introduction to creating parts with python scripts within FreeCAD.
This tutorial will cover how to build a ball bearing with a CSG-workflow.
The code will produce a new FreeCAD document with 12 shapes (Inner Ring, Outer Ring and 10 balls/spheres).
It will look like this:
The workflow is more or less identical how you would create the part in part workbench.
Just some small differences.
- Create a new empty document and make it the active document
- Insert Cylinder
- Insert Cylinder
- Do boolean cut to get basic shape of inner ring
- Select all edges and apply a fillet
- Insert torus
- Move torus into position and do a boolean cut to create the groove for the balls
- Repeat all steps for getting the shape for the outer ring
- Insert first ball
- Insert other balls using math to calculate the position of the balls
- Set view to axometric
- Zoom to fit all
In part workbench using the GUI, you would select chamfers in the 3D view or in the menu for fillets and then apply the fillets.
Here we select all edges of a shape and apply fillets.
Therefore we need to select the edges BEFORE creating the groove.
This tutorial is using part primitives and boolean operations, which can be performance consuming.
For doing a scripted part with revolved sketches have a look at the tutorial Scripted Parts: Ball Bearing - Part 2.
Scripted objects: The wiki page explaing the basics of scripting
Topological data scripting: A tutorial for covering basics of scripting
Scripted Parts: Ball Bearing - Part 2: Doing it with sketches
Bearing Script 1: Base for this tutorial, thanks to JMG ...
## Ball-bearing script ## 11.08.2016 by r-frank (BPLRFE/LearnFreeCAD on Youtube) ## based on ball bearing script by JMG ## (http://linuxforanengineer.blogspot.de/2013/08/free-cad-bearing-script.html) # #needed for inserting primitives import Part #needed for calculating the positions of the balls import math #needed for translation of torus from FreeCAD import Base # #VALUES# #(radius of shaft/inner radius of inner ring) R1=15.0 #(outer radius of inner ring) R2=25.0 #(inner radius of outer ring) R3=30.0 #(outer radius of outer ring) R4=40.0 #(thickness of bearing) TH=15.0 #(number of balls) NBall=10 #(radius of ball) RBall=5.0 #(rounding radius for fillets) RR=1 #first coordinate of center of ball CBall=((R3-R2)/2)+R2 #second coordinate of center of ball PBall=TH/2 # #Create new document App.newDocument("Unnamed") App.setActiveDocument("Unnamed") App.ActiveDocument=App.getDocument("Unnamed") Gui.ActiveDocument=Gui.getDocument("Unnamed") # #Inner Ring# B1=Part.makeCylinder(R1,TH) B2=Part.makeCylinder(R2,TH) IR=B2.cut(B1) #get edges and apply fillets Bedges=IR.Edges IRF=IR.makeFillet(RR,Bedges) #create groove and show shape T1=Part.makeTorus(CBall,RBall) T1.translate(Base.Vector(0,0,TH/2)) InnerRing=IRF.cut(T1) Part.show(InnerRing) # #Outer Ring# B3=Part.makeCylinder(R3,TH) B4=Part.makeCylinder(R4,TH) OR=B4.cut(B3) #get edges and apply fillets Bedges=OR.Edges ORF=OR.makeFillet(RR,Bedges) #create groove and show shape T2=Part.makeTorus(CBall,RBall) T2.translate(Base.Vector(0,0,TH/2)) OuterRing=ORF.cut(T2) Part.show(OuterRing) # #Balls# for i in range(NBall): Ball=Part.makeSphere(RBall) Alpha=(i*2*math.pi)/NBall BV=(CBall*math.cos(Alpha),CBall*math.sin(Alpha),TH/2) Ball.translate(BV) Part.show(Ball) # #Make it pretty# App.activeDocument().recompute() Gui.activeDocument().activeView().viewAxometric() Gui.SendMsgToActiveView("ViewFit")
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