Introduction
Chandra Systems has experience over 40 years in the field of Mechanical Engineering & is exposed to various design styles & processes.
Highlights:
· Competence with both Classic Design process with 2D & Solid Modelling based processes for engineering design
· Tools: nanoCAD for 2D tasks & FreeCAD for Solid-Modelling, FEA & other tasks.
· Selection of best design process as per project requirements.
· Development of innovative design styles based on experience
Chandra Systems Projects
Recent Design Project by Chandra Systems- MagicMini Video Link
Classic Design Process
Before the evolution of Solid Modelling / 3D software, all engineering designs & drawings were prepared manually as 2D drawings, using drawing boards. This can be considered to be the “Classic Design Process” of engineering design. Engineers had to visualize design from 2D drawings & this skill was referred to as “drawing reading” & “drawing visualization”.
Classic design process involves Layouts (or General Arrangement drawings), assembly drawings with multiple views, part drawings manufacturing drawings, process drawings, flow charts, control documentation, etc. Design & Design Validation processes are essentially manual.
Classic design process offers great flexibility during the design process; including graphic mechanism analysis, hydraulic/pneumatic circuits, control charts & representation of alternate solutions in the same document. It is versatile & complex in nature & generally “Top-Down” in nature. Even today, some organizations prefer Classic design style in the initial project stage & then proceed with Solid Modelling for the final design.
Chandra system has experience with the classic design process.
2D software: nanoCAD 5.0
Chandra Systems uses nanoCAD for 2D tasks & classic approach.
The “nanoCAD 5.0” is 2D CAD software that is compatible with AutoCAD & DraftSight platforms. It is also used to process FreeCAD-generated drawings in .dxf format to .dwg format. (TechDraw workbench)
Solid Modelling with FreeCAD
FreeCAD
FreeCAD offers a complete design platform for Solid Modelling tasks & jells nicely with all design approaches like Bottom-up, Top Down & a unique design style Vector3D.
Design Approaches
Bottom-Up Design:
In the Bottom-Up Design approach, the assembly tool works on predefined part models or components, with appropriate assembly constraints to generate assembly. It is a more conventional solid-modeling style & useful in design validation.
FreeCAD offers two assembly workbenches: A2Plus & Assembly4. A2Plus is based on assembly constraints while Assembly4 incorporates Local Coordinate Systems.
Top-Down Design:
Top-Down Design is a generative modeling technique that involves designing parts or assemblies from the top-level assembly, down to the individual parts. In this CAD approach, assembly or final product is defined at the start of the design process & serves as a reference for part design.
FreeCAD, being a parametric CAD software, offers various tools and methods for implementing the Top-Down Design process. FreeCAD covers almost all known Top-down design methods.
Top-Down Design Process with FreeCAD:
FreeCAD workbench Assembly4 supports Top-down design approach. It has features like Master-sketch, Local Coordinate System (LCS), variables, shape-binder & spreadsheets.
Video - Top-Down Design with FeeCAD
The following are some main approaches:
1. In-Context Part Design
In this approach, a part can refer to features of another mating part as external reference for sketching & part building. FreeCAD shape-binder tool is used for referring faces of other parts.
2. Master-model Technique
Master-model serves as a reference for part design & assembly. Shape-binder (or binder) is used for deriving parts from Master-model.
3. Shell / Surface-based Top-Down Design
A set of reference surfaces (planes) or shell is used for the design of mating parts fitting on the base part. FreeCAD shape-binder tool is used for referring faces of the reference part.
4. Skeleton-based Top Down Approach
A skeleton is an abstraction of an assembly & generally consists of points, 3D lines, planes, 3D sketches & in some cases surfaces. FreeCAD Assembly4 workbench offers a nice platform for skeleton-based design & offers animation too.
5. Master-sketch based Top-Down design
Master-sketch serves as a reference sketch for the design of multiple parts & assembly. Shape-binder (or binder) is used for deriving parts from Master-sketch.
Innovative Design Approach: Vect3D
Vect3D is inspired by " 3D sketches"- the favorite of artists, architects, scientists & designers in general. Vect3D is based on the FreeCAD Assembly4 workbench & meets most of the CAD software expectations.
Chandra Systems has developed an innovative CAD approach based on 3D sketches/skeletons, parametric design, animation & mathematical /vector analysis with Spreadsheets.
This is a unique design approach due to the focus on abstract models & computations in spreadsheets.
Illustration of Vect3D approach
Illustration: Three Actuator Gantry
Analysis
FEA / FEM
Finite Element Analysis (FEA/FEM) receives inputs from Solid Model software & has different file formats, like .inp, .dat, and .unv for design inputs & .vtk & .vtu for design output.
Best Design Practices
Chandra Systems has experience over 40 years in Machine Design, Automation & Mechanical Engineering Design; & has vast data of best design practices. This helps in developing state-of-art design solutions for customer needs.
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