Mechanical Engineering Consultants Use 3D CAD Software Comparison via Custom Motorcycle Frame: Creo vs Solidworks vs Inventor: Part 2

3D CAD Software Comparison Blog Series: Starting the Motorcycle Frame Design in Solidworks™ 

Welcome back to our 3D CAD software comparison blog series. Recall that in last week’s discussion, as Mechanical Engineering Consultants we introduced our plan to to model a motorcycle frame in three different 3D CAD software packages.  We gave a brief history of the three CAD software packages that Glew Engineering employs: Solidworks™, Creo™, and Inventor™.

In this week’s blog, as Mechanical Engineering Consultants we use Solidworks™ CAD software to model a portion of the motorcycle frame, a simple tube, while comparing three modeling techniques:

  • Extruding
  • Sweeping
  • Weldment

Motorcycle Frames

We designed a simple bobber inspired motorcycle frame, this is conceptual, yet realistic enough to illustrate our points. See Fig. 1.

Solidworks CAD Motorcycle Frame Components

Fig. 1 – Rigid Bobber Frame Components[1]

3D CAD Software Sketching and Feature Generation

For comparison, as Mechanical Engineer Consultants we modeled the bottom rail portion of the motorcycle frame via three different techniques: (1) an extrusion, (2) a sweep, and (3) a weldment.  Each modeling technique has advantages in certain design scenarios. In other design scenarios, any modeling method may do.  As is the case in most 3D CAD programs as well as Soldiworks™, one first creates a 2D sketch of a profile, then converts it into a 3D feature.

Solidworks™ Extrude Command

First,  we created the motorcycle frame bottom rail from a 2D sketch of two concentric circles (to simulate the tube profile and wall thickness).  We extruded it to a specified length of 20 inches. Solidworks™ represents the length with the parameter D11, visible in the figure. See Fig. 2.  This parameter can be changed, hence the term "parametric design." As Mechanical Engineering Consultants we have many tools available to perform the most intricate of designs. 

Motorcycle Frame Bottom Rail Solidworks Extrude

Fig. 2 – Motorcycle Frame Bottom Rail via Extrude Command

Solidworks™ Sweep Command

Secondly, we created the motorcycle frame bottom rail with the Solidworks™ Sweep command. It requires a 2D sketch of the geometric profile, in this case the concentric circles, as well as a 2D sketch “path” to sweep the profile over, creating the 3D part. See Fig. 3.  This is analogous to gouging out a groove using a chisel to follow a penciled line drawn on a piece of wood.  The shape of the chisel is the profile and the penciled line in the wood is the path. 

Motorcycle Frame Bottom Rail Solidworks Sweep

Fig. 3 – Motorcycle Frame Bottom Rail via Sweep Command

Solidworks™ Weldment Command

Thirdly, we created the motorcycle frame bottom rail using the Solidworks™ Weldment command.  See Fig. 4. It creates information in a Solidworks™’ database to recognize the feature as a welded or weldable part for manufacture. Soldworks™ contains a list of weldment profiles from which to choose, including both ANSI and ISO metal pipes and beams. 

Motorcycle Frame Bottom Rail Solidworks Weldment

Fig. 4 - Motorcycle Frame Bottom Rail via Weldment Command

Solidworks™ Feature Comparison: Extrude vs Sweep vs Weldment

There are advantages to each technique: (1) extrusion, (2) sweep and (3) weldment.

  • The Extrude command is simple to use, but requires one to piece together individual parts to form an assembly. This procedure may be tedious for large welded structures, such as motorcycle frames.
  • The Sweep command in Solidworks™ may fail due to geometric interference when sweeping a large 2D sketch profile over sharp transitions along paths, and should be considered carefully.
  • Because Solidworks™ treats weldments differently, observe care when drawing the 2D sketch path the weldment will follow.

Summary

As Mechanical Engineering Consultants we designed a custom bobber motorcycle frame.  Next, we modeled (designed) a portion of tubing in the motorcycle frame with Solidworks™ by three different methods.  We showed that Solidworks converts 2D sketches into 3D parts in multiple ways. We discussed some of the issues faced with each of the three techniques we showcased.  As of yet, we have not determined which of the three is the best method.  However, as we progress through the design, there may suggest one method as the best choice for patrons of the frame.

[1] http://www.custom-choppers-guide.com/how-to-build-a-chopper-frame.html

 

Mechanical Engineering Consulting Firm Evaluates 3D Software Using Motorcycle Frame – Part 1

motorcycle meshed for mechanical engineering consulting

Fig. 1 A street bike shown in CAD mesh.

Mechanical Engineering Consulting Group Evaluates 3D CAD Programs

Mechanical Engineering Consulting Testing of Creo™, Solidworks™, and Inventor™

Mechanical Engineering Consulting service companies largely use one of three 3D CAD programs: Creo™, Solidworks™, and Inventor™.  At Glew Engineering, we have licensed seats of all three CAD mechanical design packages.  We reviewed the CAD workflow and feature sets of each 3D CAD program using motorcycle frame design as an example.  Also, we showed that some of the specialized commands of each 3D CAD software programs are better suited for specific tasks. Our engineers are experienced with 3D CAD,  stress analysis by Finite Element Analysis (FEA), as well as Computational Fluid Dynamics (CFD) FEA & CFD.   Using Glew Engineering’s expertise, we help answer the question: which is the best CAD program for various applications?

Mechanical Design 3D CAD Software Benefits Custom Motorcycle Builders 

Mechanical Design 3D CAD software provides value to motorcycle companies in high volume manufacturing production, customer builders, and motorcycle aftermarket suppliers. The large meshed figure above in Fig. 1 illustrates 3D CAD software technology used in the sport bike industry.   Unfortunately, many custom bike manufacturers and low volume motorcycle shops design and build by hand, not with CAD.  They miss the CAD benefits of the ability to redesign on the fly, optimize material selections prior to fabrication, simplify their tooling and jigs, and reduce weight.  These benefits drive down time to market and cost.  Engaging an outside mechanical engineering consulting firm can bridge the gap with custom motorcycle builders and fast time to market expectations of clients. See Fig. 2 below of a chopper, and Fig. 3 of a custom bike in process.  

 

 

Red Bobber Motorcycle

Fig. 2 A Bobber Style Motorcycle Frame

Fig. 3 Custom Bike in Progress

Mechanical Design using Creo™, Solidworks™, and Inventor™

CAD companies design their software with different intended principal applications and markets, hoping to serve the broadest mechanical design market spaces possible. AutoCAD™ was initially designed for Architectural CAD (ACAD).  The 3D CAD software packages CREO™, Solidworks™, and Inventor™ were originally designed for Mechanical CAD (MCAD).  To some extent, most MCAD software integrates with or has some Electrical CAD (ECAD) capability.  Further, they also integrate with Finite Element Analysis (FEA) software and Computational Fluid Design (CFD) packages.  Most companies use 3D CAD software for various functions, not just mechanical design and layout: two dimensional (2D) part drawings, assembly drawings, illustrations, bills of materials (BOMs),  parts lists, animations, illustration, manuals and more. 

Benefit of Using a ‘Software Agnostic’ Mechanical Engineering Consulting Firm 

When searching for an outside mechanical engineering consulting firm, it is advantageous to engage an organization that uses the same package as your internal engineers. Or if no internal CAD program already exists, then choose an outside firm that can select the software that is optimal for the design requirements at hand.

SolidWorks™ tends to be used by small to medium sized companies needing an easy-to-use, intuitive, and affordable 3D CAD program. The medical device industry uses SolidWorks™ almost exclusively. Many perceive that it has a fast learning curve, as well as, user friendly. 

Large companies, as well as their supply chain, who need a mature, robust 3D CAD program use Creo™.  Companies value the ability to handle large assemblies and uniformly control many CAD seats.  Companies, along with their supply chains, in the defense and aerospace industries use Creo™ for complex projects.  CAD users often perceive, rightly or not, that Creo™ has a steep learning curve.  However, the same CAD users realize its many advantages for complex projects and configuration management.  Simply, some feel it trades power for simplicity.  PTC has made many changes in Pro/Engineer, and CREO™ a more user friendly and stabile than it was three decades ago.  PTC’s many enhancements to the graphical user interface (GUI) rivaling the competition’s user experience.   

Small to medium sized companies tend use Autodesk Inventor™ for its 3D capability, design tree, and other features that are necessary to MCAD users.  Also, it provides tight integration with their FEA and CFD offering (FEA & CFD). Autodesk sells Inventor™ as part of a software design suite with 20 other pieces of software to enhance the design process.  CAD users often perceive it as having a simple user interface with a fast learning curve, more akin to SolidWorks™ than CREO™.

At Glew Engineering, we use all three of these 3D CAD software packages (CAD) and wrestle with the question of which package is best for a project.  Generally, we use the CAD software that our clients use for compatibility.  This enables a seamless transfer of knowledge and files between the Glew team and the client.  If a client does not not already use CAD, Glew will discuss the trade offs of the different software approaches.  Leading to many of the same questions, posed in the blog series relating to which 3D CAD software would be best for a specific project.  

In the next installment in the 3D CAD Comparison series of blogs, we actually design and model a motorcycle frame and compare different programs.  Fig. 4, Early Stage 3D CAD Bobber Motorcycle Frame Design, and Fig. 5 Completed 3D CAD Bobber Motorcycle Frame, are featured in the next part of the series.

 

 

CAD Motorcycle Frame 1

Fig. 4 – Early Stage 3D CAD Bobber Motorcycle Frame Design

Fig. 5 – Completed 3D CAD Bobber Motorcycle Frame

Italian Masters: Volta Jump-Starts Electrical Engineering

Italian Masters: Volta Jump-Starts Electrical EngineeringCardanoFigure 1: Girolamo Cardano (1501-1576)

Welcome back to our series on Italian Masters of math and science.  Last week I wrote about Galileo’s extensive accomplishments both in the field of astronomy and beyond.  This week, I’ll take a look at another renaissance polymath who dabbled in astronomy, along with his work in mathematics, medicine, biology, chemistry, philosophy, and gambling (yes, seriously): Girolamo Cardano.  Cardano is a less well-known figure than Galileo or some of the other scientists I’ve written about who have famous equations or units of measurement named after them, like Volta or Torricelli.  He is regarded as one of the greatest mathematicians of his age, however, and made a great many contributions to science, mathematics and mechanical engineering, despite his reputation as a disrespectful, gambling misanthrope.

Girolamo Cardano (1501-1576)

Born in 1501 in Pavia, Cardano was the illegitimate son of a Milanese lawyer and mathematician.  Although his father hoped Cardano would follow in his footsteps and study law, he was too intrigued by the sciences, and pursued a path in academics, starting with a degree in medicine in 1526.  He lived a hard life, as the circumstances of his birth, his perpetual gambling habits, and his irascible temperament always stood in his way.  It took him 14 years to gain admission as a professor at the College of Physicians in Milan, due to being a bastard in more ways than one: besides his illegitimate birth, he also penned scathing critiques of the physicians at the College as vain and talentless hacks.  Ultimately, he was awarded a professorship at a series of universities throughout his life, though his troubles never ceased.  Of his three children, his older son was executed in 1560 for poisoning his wife and his younger son was banished and disowned in 1569 for gambling away Cardano’s money and burglarizing his house to pay overdue debts.  Not long after in 1570, Cardano found himself under arrest by the Catholic Church on charges of heresy.  He was only imprisoned for a few months, but after his release he was nonetheless forbidden from holding a university post or publishing any work for the rest of his life.  He finally passed away in 1576, and many believe he intentionally committed suicide in order to fulfil a horoscope he had cast for his own life years earlier.

Mathematics and Probability

Cardano spent a great deal of time tackling the mathematical unknowns of his time.  His biggest impacts on the field of mathematics arose from his work on algebra and probability.  Cardano derived solutions for a number of significant problems in algebra, including methods for determining the roots of cubic and quartic equations and expanding binomial equations.  His solutions are all the more impressive considering that European mathematicians were not yet acknowledging that negative numbers could exist and had not yet developed a theory for complex numbers.  His methods may seem needlessly complex by today’s standards, considering how broad our mathematical toolbox is, but the fact that his solutions worked despite such handicaps is testament to his brilliance.

Cardano-diceFigure 2: Six-sided dice (6d6)
Daniel Tan,

[FreeImages.com Content License]

That brilliance also found its way into his life in dice halls and chess games.  His insight into the nature of these games of strategy and chance led him to the development of the first systematic exploration of probability and statistics.  He based his theory on the ratios of favorable outcomes to non-favorable outcomes, which we now call “odds” in both gambling and statistics.  His initial forays into determining the combined probabilities of multiple events with their own odds set the stage for later mathematicians to develop the rules we still use in statistics today.  Indeed, the very examples he used in his treatise Book on Games of Chance would still be familiar to students 5 centuries later, as he used throws of 6-sided die to demonstrate the likelihood of certain outcomes.

Mechanical Engineering

Cardan-gearFigure 3: Cardan Gear
By http://www.mekanizmalar.com/cardan_gear.html

Cardano was also an accomplished mechanical engineer, constructing devices that were the predecessors to tools we still use today.  Some of his inventions are so tied to his work that they still bear his name.  The cardan gear, for instance, is an efficient method for converting rotational motion into linear motion.  He is sometimes credited with inventing a combination lock, the three-ringed gimbal method for stabilizing compasses, and the universal joint, the last of which is still sometimes called the Cardan joint.  There is some debate as to whether he independently arrived at these inventions or was just improving ideas by previous scientists and inventors.  Regardless, the fact that so many inventions are credited to his experimentation goes to show how much respect his peers and successors had for his creativity.

Lasting Impact

In his own autobiography, Cardano described himself as “hot-tempered, single-minded, and given to women,” and considered himself “cunning, crafty, sarcastic, diligent, impertinent, sad, treacherous, magician and sorcerer, miserable, hateful, lascivious, obscene, lying, obsequious.”  While he wasn’t proud of his own gambling or abrasive personality, he did take great pride in his work as a physician, mathematician, scientist, and inventor.  People tend to focus on Cardano’s hard living and the scandals he was involved in, while unfortunately overlooking his many achievements.  Steeped as we are in math and science, we can surely appreciate the accomplishments of a man who burned the candle at both ends as brightly as Cardano did.

FEA Consulting Part 3: Meshing and Boundary Conditions

We’ll continue on now with our blog series on finite element analysis (FEA).  After discussing how to best set up a computer-aided design (CAD) model for FEA simulation, in this blog I’ll cover the next step: meshing the model and applying boundary conditions.  “Meshing” is the process by which the CAD model is separated into discrete finite elements; it can be done in the same program that runs the FEA numerical simulation later, or it might be performed in a standalone program, depending on your software.  Boundary conditions are the loads (forces, movements, impacts, etc) and constraints that interact to actually cause deformation and stress in each element, and in turn the model as a whole.

Mesh Generation

The mesh essentially gives finite element analysis its name; breaking a large complex shape into many smaller simple shapes allows the FEA program to easily evaluate the stresses for those simple shapes.  In a 3D element like our concrete slab in Figure 1, these elements might be simple cubes, or they might be more irregular pyramids and tetrahedrons.  Once the meshing program has evaluated the behavior of each discrete shape, it can integrate the data from these elements to create a model for the complex shape as a whole.

Automatic versus Hand Generation

FEA can be performed by hand, as it was during its initial development in the 50s and 60s (Comini, p. 1)

[i].  Most FEA software still allows the user to develop meshes by hand, but for anything beyond the simplest shapes it becomes quite time consuming.  It must also be redone for each design iteration.

In general, it is preferable to allow a meshing algorithm to generate the mesh.  Based on a few parameters that the user can adjust, including ideal element size and aspect ratio, the program will move through the model and attempt to create a cohesive mesh.  However, despite many improvements over the years, automatic mesh generation is still not foolproof.  Even a simple flat plate can be have trouble meshing, if there are discontinuities in the boundary conditions.

Guided Automatic Generation

Meshing programs usually offer tools to locally refine a mesh at specific spots on the model.  Autodesk Simulation, for instance, allows the user to create nodes on the model and then force the mesh to generate elements of a smaller size in a certain radius around that node.

The best solution for mesh generation is a compromise between drawing the mesh by hand and giving the meshing program total control.  An experienced FEA consultant can design or reconfigure a CAD model such that it encourages the mesh to form a certain way.  With an understanding of mesh generation algorithms, how meshes should be formed for certain constructions (for instance, at sharp corners or through thin plates), as well as how the algorithm interacts with the CAD file, an expert FEA engineer can make the meshing program run in predictable and useful ways.  Figure 1, at the opening of the blog, shows a portion of our final mesh after we’d guided its generation with some careful CAD work.  This is one reason that Glew Engineering keeps multiply CAD licenses, to correct CAD designs for FEA purposes.

Boundary Conditions

FEA is the solution of partial differential equations for many small elements, with certain boundary conditions applied to the perimeter and perhaps internal nodes.  The boundary conditions are thus the loads.  FEA modeling is always concerned with how an object will respond to some external stimulus, simply called the loads.  Force on a part results in deformation, or motion.  If the part is static, then there must be reaction forces opposing the loads.  The concrete slab in this problem is being pulled down by gravity and the loads placed on the floor, but opposed be the support columns and constraints around the perimeter of the floor.  Without specifying both the applied loads and external constraints, the floor would not be static.

mesh_loads_and_constraints_pre-analysis
Figure 2: Loads and constraints
© Glew Engineering Consulting, 2016

Loads

There are a few types of loads that a CAD model can be subjected to in a FEA program.  A force pushes or pulls on a specific section of the model, while a pressure exerts a distributed force across a surface.  An impact is simply a force that is exerted instantaneously but then drops to zero.  Objects can also be set with an initial velocity, to study collisions.  Enabling gravity pulls all of the elements downward equally.  Lastly, for thermal or electrostatic analyses, surfaces can be set to a specific temperature or exposed to an electrical current.

Gravity is essential in this simulation, since the main contributor to punching shear is the weight of the concrete slab itself.  In civil engineering, the weight of the structure is called the “dead load”.  There was also a “live load”, representing the people, furniture and equipment on top of the slab.  We modeled these loads with a pressure, or equally-distributed force, across the top surface of the slab.  The live load pressure is represented in Figure 2 as the orange force arrows pressing down on every element along the top surface.

Constraints

Constraints prevent some part of the concrete slab from moving vertically, which causes the weight to deform the slab.  Every model needs a set of physical constraints keep it from flying off into infinity while still letting it bend, expand or contract as it would in real life.  These constrains can prevent translation (movement) in the x, y and z directions or rotation about the x, y and z axes.  Many times the constraints on a given surface will involve restraining some translational axes and some rotational axes.  If the model has been cut across a symmetry plane, for instance, then the elements on that surface need to be constrained such that they can’t move across it or rotate into it (otherwise our side and the mirrored side would rotate into each other, which we can’t allow).

The small red circles shown in Figure 2 mark the constraints on every node (the intersections between element) along one symmetry plane on our slab.  To obtain the correct symmetry behavior, we set:

  • No translation in the x-direction
  • No rotation about the y-axis
  • No rotation about the z-axis

Applying loads and constraints in FEA

The initial steps in setting up an FEA model determine the simulation.  The CAD model may need to be constructed in a certain way to allow the mesh to generate.  Then, that mesh needs to meet certain criteria if it’s going to be useful and give accurate results.  The loads need to be set correctly. Appropriate constraints ensure that the system is not under- or over-constrained.  Accurate and useful results in FEA simulation requires one to be careful and thorough in the initial setup.

Glew Engineering has done FEA consulting on a variety of projects, from semiconductor chambers and optical systems to vehicle lifts, heat exchanges and smart phone headsets.  Most of these we can’t post for proprietary reasons.  Take a look at our finite element analysis consulting services, and let us know how we might help you.

References

[i] Comini, G., & Giudice, S. (1994). Finite element analysis in heat transfer: Basic formulation and linear problems. Washington, D.C.: Taylor & Francis.