TechniCom tests (Part 4) – Inventor’s digital prototyping vs. SolidWorks for a clevis pin design/analysis

Assembly Design and Analysis

Continuing on with part 4 of our blog series dedicated to showing the differences between Autodesk Inventor Professional 2011 and SolidWorks Premium 2011 for digital prototyping workflows, we examine the ability to select and analyze the correct clevis pin for the assembly shown below.

Assembly with clevis pin indicated by orange dot

This test focuses on the design of a clevis shear pin and its related holes in this hydraulic clamping assembly. The pin needs to be optimized so that if a failure occurs, the pin fails and not the other components. We’ll seek a factor of safety of 2 for the clevis pin, and 4 for the rest of the assembly. The Clevis Pin shear pin must withstand 250 N force with a factor of safety of 2. The bending force on the pin is important. If it exceeds maximum allowance the pin cannot be removed. The pin should be sized to meet the forces at the designated safety factor and fit within the support structure. The pin should further be selected from a standard library of components and created with the size required. The design calculations should be stored for documentation.

Autodesk provided a Parasolid model of the above assembly and a video of Inventor performing the design and analysis to select the proper pin to fit within the clevis opening.

The key differences you will see demonstrated below

Both Autodesk Inventor and SolidWorks can solve this problem; however there are important differences in the steps required to complete the exercise and the confidence in the engineering optimization.

Inventor executed all of the steps within one command sequence. SolidWorks uses separate commands for each of the three key steps. Both Inventor and SolidWorks seem to have an equally robust clevis pin library, and automatic sizing capability.

The engineering calculation is the differentiator in the example. For this problem Inventor designed a solution using its engineering calculations library for clevis pins. The only solution offered by SolidWorks was to use FEA, which in this case, proved to be difficult to verify and is a questionable strategy.

Inventor users have the ability to leverage standard engineering calculations shown below which are included in design accelerator tools. In this test we examine the clevis pin generator. The same concept applies to bolts, bolts, frames, shafts, gears, bearings, belts, chains, keyways, cams, splines, o-rings, and springs. Inventor does not require the user to know or learn the engineering equations; the software does it for you. In the case of using FEA, the engineer must be concerned with the accuracy (error) inherent to FEA methods, necessitating a higher skill set, and certainly more time. Inventor’s automation of standard engineering calculations provided a better solution and reduced design time.

What’s Important in Assembly Design and Analysis

  • Select the most appropriate purchasable clevis pin that meets the specifications
  • Weigh design decisions that affect cost, product reliability, and weight
  • Evaluate the performance of the final design

Observations

Inventor executes all of the steps (make the hole, insert the pin, perform the engineering calculation) required within one command (feature). SolidWorks uses separate commands for each of the three key steps. Both Inventor and SolidWorks seem to have an equally robust clevis pin library, and automatic sizing capability.

The engineering calculation is the large differentiator in the example. Both Inventor and SolidWorks offer integrated finite-element analysis (FEA). However, using FEA methods for this kind of problem is a questionable strategy. Autodesk prompted the user to determine the correct pin size by using its engineering calculations. SolidWorks does not provide this kind of functionality. SolidWorks’ concept was to have the designer select the pin size and then perform an FEA analysis in an iterative fashion to arrive at the correct sizing. SolidWorks was able to use its own no-charge Simulation Xpress to perform the FEA analysis. SolidWorks Simulation Xpress is a first-pass basic stress analysis tool that comes with every SolidWorks Standard and Professional software package, offering limited FEA functionality.

Design Accelerator in Inventor

SimulationXpress environment in SolidWorks

 

Standard engineering calculations (analytical methods) exist for this situation, making FEA methods unnecessary/overkill. The FEA boundary conditions necessary for this case present a convergence issue (singularity) for most solvers. This increases the expertise required to verify the accuracy of this FEA study with any level of certainty. Some FEA programs will simply never reach a reliable result for this case. This is typically referred to as a divergent case. SolidWorks Simulation Xpress did not allow us to individually manipulate the mesh to test for convergence.

See how Inventor solved the problem in this video.

See how our engineer solved the problem with SolidWorks.

Here are the calculations  Inventor uses to solve the clevis pin selection.

Engineering equations Inventor used for the clevis pin calculation

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The next blog in this series will examine exporting a mechanical design to a BIM system. Stay tuned or sign up to be notified of my blog updates.

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TechniCom tests (Part 3) show why Inventor’s digital prototyping outshines SolidWorks in Plastic Injection Mold Design

Plastic Injection Mold Design

Continuing on with part 3 of our blog series dedicated to showing the differences between Autodesk Inventor Professional 2011 and SolidWorks Premium 2011 for digital prototyping workflows, we examine the ability to design and validate molds, starting with a pre-designed part.

We show below, using videos from both systems,three major design aspects of mold design:  the ability to use a 3D model of a plastic part to create the core and cavity of the mold, designing and engineering the multiple components and systems of the mold, and validating the design to ensure it can manufacture high-quality plastic parts.

Simple mold design used in this workflow test

Autodesk provided us with a model of the handle to be molded, detailed specifications for the mold, and three videos of Inventor performing the desired tests showing the workflow for splitting core and cavity, engineering of the mold, and a simulation and validation of the mold.

The key differences you will see demonstrated below

Autodesk Inventor provides standard libraries of mold bases and components along with automated tools for splitting the core and cavity and for designing the runners, gates, and cooling and ejection systems. The inclusion of Autodesk Moldflow simulation software directly in the design workflow allows designs to be validated and improved upon until they will optimally manufacture products of the highest quality.

SolidWorks includes dedicated functionality for splitting the core and cavity, but that is where the mold design capabilities end. With no automated design tools and no libraries of components, the design of injection molds is entirely manual and inefficient. Without any built-in plastics simulation capabilities, mold designers must purchase third party software, such as Autodesk Moldflow, often at significant cost, to validate and optimize their designs to ensure quality.

What’s Important in Plastic Injection Mold Design

  • Balance of speed in designing the mold while ensuring high quality.
  • Accurate design of mold components including runners for injecting the plastic materials, cooling of the mold, and ejecting the finished part.
  • Iteration of the mold design with simulation to arrive at an optimal design.

Observations

Splitting the Core and Cavity

The desired result was to generate parting surfaces and complete the core and cavity operations.

Inventor parting surface generation

SolidWorks parting surface generation

Inventor used a mixture of automated and manual patching and runoff surface creation tools. Surfaces for simple holes and profiles were created automatically which increases productivity. Complex patching and runoffs were created using Inventor’s surfacing tools.

SolidWorks also assisted the user in splitting the core and cavity with automated and manual tools for defining the parting line and creating patching and runoff surfaces.

The two systems are comparable in capability. SolidWorks required a few more menu picks and interactions, but both came up with an acceptable mold core and cavity. SolidWorks generated an odd triangular shape in the area to be removed, but it was temporary and did not affect the final part.

See the video of Autodesk’s engineer using Autodesk Inventor to perform the core and cavity workflow using Inventor: 

See how our engineer used SolidWorks to perform the core and cavity operation:

Engineering the Mold

The tasks completed included: designing the runners, adding a submarine gate, inserting a properly sized mold base, inserting a sprue bushing, designing cooling channels, attaching pipe fittings for cooling channels, and adding ejector pins as specified.

Inventor completed this task using a built-in workflow for designing injection molds that includes libraries of mold bases and standard components as well as automated design tools for runners, gates, cooling channels, slides, lifters, and ejectors.

 

Automated ejector placement in Inventor

Manual ejector placement in SolidWorks

SolidWorks had no built-in functionality for designing injection molds. All standard components needed to be searched for and brought in from external content centers or supplier websites, a time-consuming process. All modeling was done manually as there are no automated design tools for the various systems of the mold. This made mold design in SolidWorks a tedious and labor-intensive process with low user productivity. SolidWorks was able to build the geometry required for the moldbase design, but it was a laborious process.

See the video of the Autodesk engineer performing the mold design:

See TechniCom’s engineer performing the mold design using SolidWorks:

Validating the Mold Design

To validate the mold design for manufacturability we needed to first determine the optimal molding conditions for the entire system as designed. Next, we performed a filling analysis to determine if the mold, as designed, could completely fill the cavity at acceptable quality. Then, we assessed the location of air traps and weld lines. Lastly, we performed a shrinkage analysis so exact figures could be input for core and cavity sizing rather than manually inputting generic percentages.

Inventor includes Autodesk Moldflow simulation built-in to the mold design workflow, which was used to simulate the filling phase of multi-cavity molds and their respective runner systems to validate manufacturability. A shrinkage analysis was also used to ensure cavities were sized based on the specific design, rather than relying on generic shrinkage factors from the material supplier.

Inventor validates the mold design.

SolidWorks has no built-in simulation capabilities and therefore had no ability to validate the mold design for optimum molding conditions or for a filling analysis that would help the user avoid manufacturing problems that can potentially result in huge expenses in both time and cost. SolidWorks was unable to perform any portion of this validation using its software or no-charge software, of which there was none available that we were able to find.

Users could use Autodesk Moldflow stand-alone software that would have the capabilities required, at extra cost. Our analysis did not include examining extra cost third party products. We only compared Inventor Professional to SolidWorks Premium. Therefore we do not have a video of SolidWorks performing the mold validation.

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The next blog in this series (Part 4) will examine designing and analyzing a clevis pin in a hydraulic clamping assembly. Stay tuned or sign up to be notified of my blog updates.

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TechniCom tests (Part 2) show why Inventor’s digital prototyping outshines SolidWorks in Plastic Part Design

Part 2 of this 8 part series reveals the results of the Plastic Part Design workflow

Plastic Part Design tests the ability to import surface data from Alias, stitch the skins into a solid body, design the shell the part with a specified wall thickness, part using surfacing and plastic features, import new surfaces and update the model, and perform an injection molding simulation on the part.

Autodesk provided us with data files specifying the solid model, IGES and WIRE data files of the surfaces, and three movies depicting the workflow for surface import, engineering design, and simulation and validation.

A view of the final parts

What’s Important in Plastic Part Design

  • Rapid design, ready for manufacturing
  • Working with surfaces from industrial design software
  • Ability to directly create mold ready parts, typically for injection molding
  • •Evaluating the moldability of the part

Observations

Surface Import

Inventor was able to import the Alias wire file natively without issue. SolidWorks was unable to import the Alias wire file. Users must first translate Alias data to an IGES file, which is susceptible to translation errors, albeit not in this case.

Here is how Autodesk used Inventor to perform the surface import workflow:

Here is how TechniCom’s engineer used SolidWorks to perform the surface import workflow:

Building the Model

Creating a solid model from imported surfaces and being able to shell the resulting solid are typically the most error-prone steps in the process. Inventor was able to stitch and shell the part with zero errors. The shell was created in one step by defining the variable in the shell dialog box. SolidWorks was also able to stitch and shell the part with zero errors. Shell creation involved several steps to create and define the variable.

Specifications of the bosses

Plastic parts are typically designed using a set of standard features such as ribs, bosses, grilles, snap-fits, and lips to name just a few. The MCAD software should assist the user in efficiently modeling these features. Inventor used its plastic features toolset to add the two different types of bosses, a lip feature, and ribs. SolidWorks used plastic features for a majority of the features, although the recessed bosses required for this test first needed to be built manually and then added from the library of custom user features.

Here is how Inventor was used to build the model:

Here is how SolidWorks was used to build the model:

Simulate and Validate the Part Design

Plastic parts must be checked for potential quality defects prior to committing to the cost of designing and building the mold.

In the simulation to evaluate the manufactured quality of the product as-designed, Inventor simulated the injection molding process and uncovered high amounts of shear stress due to the part being too thin. If left uncorrected, this issue would lead to material degradation and molding defects or field failure. Inventor’s built-in mold analysis software also provided more extensive capabilities in terms of material selection and multiple gate analysis.

SolidWorks feedback about potential quality issues

Inventor feedback about potential quality issues

There are no built-in simulation capabilities within SolidWorks for evaluating the manufactured quality of the product as designed. However, we were able to use a third partner add-in module called SimpoeXpress. This has limited function, but allows for some material selection and a single gate. SolidWorks was able to simulate the molding process but the only result the user received was the filling pattern, which provided limited value. It was unable to identify any quality defects and the user was misled into thinking the design was acceptable. More comprehensive simulation packages are available at a cost of more than $5000.

After modifying the 3D CAD model, we reran the simulation to validate the design change. After making the recommended change to the part, Inventor automatically updated the model in the simulation environment; all that was required was to re-run the analysis. SolidWorks automatically updated the geometry but the analysis had to be setup from scratch, including processing parameters, gate location, and material selection.

Inventor’s workflow:

SolidWorks’ workflow:

Summary

Importing the IGES files and creating the plastic part was comparable for both products. While SolidWorks was able to import IGES curves from industrial design software, Inventor was able to directly read Alias (a leading industrial design software package) surface data, an advantage. Both products had excellent capabilities for building specialized plastic features such as the mounting boss and the lip and groove on the connecting halves of the model.

Inventor’s built-in analysis software powered by Moldflow provides impressive analysis capabilities, and is well integrated into part design. To perform these same tests with SolidWorks, on the other hand, required a no-charge third party product that was able to perform only a limited analysis of the part. The limited function mold analysis software that was free does not provide the engineer enough insight to be confident that parts can be manufactured at all or at acceptable quality. More complex mold analysis software with advanced analysis capabilities (which was not used) is available to SolidWorks users at considerable extra cost.

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TechniCom detailed tests (Part 1) show why Inventor’s digital prototyping outshines SolidWorks

Executive Summary (Part 1 of an 8 part series)

Last Summer (August 2010) TechniCom Group published a report comparing Autodesk Inventor and Dassault Systemes SolidWorks using our Delphi Expert Analysis methodology[1]. The results of this report were somewhat controversial; Autodesk Inventor scored better in all fifteen categories than did SolidWorks, including core modeling. The scoring for the Delphi Expert report was the result of a very detailed survey of eight expert users of the two systems, four experts for each system. The experts had comparable familiarity with their systems and comparable backgrounds.

Readers of that report evidenced hunger for more detailed information, one that might be less sensitive to opinions and be more factual. As a result, TechniCom worked with Autodesk to develop a series of tests between the two systems that might expose the differences between the two systems and perhaps highlight advantages Inventor might have as compared to SolidWorks.

We are publishing the results of this series of tests in an eight part blog beginning with this summary of the results. Every two days or so we will add the details of each test, concluding the whole series within the next three to four weeks. Videos and images of both systems performing the tests will be included. At the end of this blog series we will publish a pdf version of the complete report on http://www.cad-portal.com.

A little background up front:

  • Autodesk commissioned (paid for) the tests.
  • Autodesk specified the tests which it challenged TechniCom, using SolidWorks Premium 2011, to match the results.
  • The seven tests are in the seven categories where TechniCom’s Delphi Expert report showed Autodesk Inventor rated the highest.
  • Extra cost third party software was not to be considered. When we were able, we used no-charge third party add-ins for SolidWorks — none were needed for Inventor.

Deciding what to test

First we had to decide what to test and the scope of the testing.

Followers of the mechanical CAD market are no doubt aware of the term Product Lifecycle Management, often designated as PLM. Autodesk’s mechanical philosophy is to eschew developing PLM software in favor of digital prototyping.

The term “Digital Prototyping” has led to some confusion in the industry. One clear definition comes from IDC in a paper entitled “Digital Prototyping: Autodesk Strengthens Competitiveness of Worldwide SMB Manufacturers’, published October 2008. This whitepaper differentiates digital prototyping from PLM by noting that “PLM reaches from a product’s cradle to its grave. On the other hand, digital prototyping stops at the completion of the digital product and its engineering bill of materials . . . The beauty of digital prototyping is that designs can be tested out before they go to manufacturing.”

Thus, Autodesk’s definition of digital prototyping includes the basic functions of PLM — industrial design, design and engineering, data vaulting, and collaboration, without the post-manufacturing baggage.

Autodesk has been carefully steering its Inventor software product development over the past few years to enable workflows that take maximum advantage of seamlessly passing data among its built-in application solutions. Thus, what we see in Inventor today is a careful melding of technologies that Autodesk has acquired or built. Many of these technologies are not available as extra cost add-ons to the base software, but fully included as part of the Inventor software. Some example, of which you will see more later, include mold analysis software, mold base design capabilities, built-in advanced simulation, inherent design automation options, an intelligent part library, built-in engineering calculations, and many others. Not only are these available as an integrated part of Autodesk Inventor, but they are often combined to form workflows that aid in developing the digital engineering models.

Thus, when deciding the scope of what to test, we settled on a series of tests that focus on the areas in our Delphi Expert analysis where Inventor rated the highest. These areas include the following:

  1. Plastic Part Design
  2. Plastic Injection Mold Design
  3. Assembly Design and Analysis
  4. Exporting BIM-ready Models
  5. Interoperability
  6. Design Automation
  7. Mechatronics

Even deciding on these seven areas leaves a great many options to be tested. Autodesk decided on the detailed functions to be tested; Autodesk specified the seven tests in detail. They are aimed at comparing the two systems ability to perform common, real-world engineering workflows. These tests are not designed to be impartial; they are taken from standard demos used by Autodesk that were designed to represent a series of engineering workflows highlighting Inventor’s digital prototyping capabilities. Most of them, as the users will see from the blogs that follow in the next few days, are aimed at performing a complete design sequence. The complete eight blogs, including this summary, will cover the seven workflow tests we performed. We will include the details of what we tested, images and videos of the results, what we observed comparing the two systems, and our summary of how well each system was able to perform the desired workflow.

Tests specified by Autodesk

Autodesk provided TechniCom with the test definitions including videos of Inventor performing the desired task, starter geometry, related dimensions, and other relevant data, all described below within each test section. TechniCom’s task was to perform the same tests using SolidWorks Premium 2011. Because Autodesk provided much of the model data we were able to focus on the desired workflow details of each test rather than building geometry.

Autodesk commissioned TechniCom to perform these tests and to document the results.

Our approach

TechniCom, in collaboration with a Certified SolidWorks Professional (CSWP) performed and analyzed these tests during November and December 2010 using Inventor Professional 2011 and SolidWorks Premium 2011. To make the scope reasonable, we limited each vendor’s software strictly to what was included with the package or third party add-ins that we were able to find and download free of charge.

For the test definitions, we used the Inventor videos illustrating the work to be performed. We attempted to deliver the same results, as did Inventor, using SolidWorks Premium 2011.

As we publish the results of the seven tests, we will make available annotated videos of both Inventor and SolidWorks performing the tests on TechniCom’s blog at http://www.raykurland.com. Readers wanting to understand how the two products compared have the unique ability to review these videos along with reading our test summaries in this report.

We remind the reader that we compared Inventor Professional 2011 versus SolidWorks Premium 2011 with the restriction that extra cost third party software was not to be considered. When we were able, we used no-charge third party add-ins for SolidWorks — none were needed for Inventor.

Summary of the test results

We plan to provide more detail, including videos of both systems performing the tests, in a series of blogs beginning in the next two days.

Plastic part to be designed

In the first two tests, plastic part design and injection mold design, Inventor clearly outclasses SolidWorks. Whereas Inventor completed all aspects of the test, SolidWorks was unable to complete major portions of the analysis of the part and the mold.

Mold design used

Inventor was also able to design the mold significantly faster than SolidWorks due to the inclusion of automated tools for designing the various subsystems of the mold.

For the assembly design and analysis test, both systems were able to model the addition of a clevis pin. However, Inventor excelled in its ability to design the correct pin by coupling its engineering calculation library to the potential design. In other words, Inventor helped select the correct pin size because it was able to use its calculations concerning the required stress that the pin would need to perform correctly. This is subtly different than SolidWorks, which used its library to size the pin, but without taking into account its stress requirements.

Final assembly showing clevis pin

The SolidWorks approach was to design the pin and then analyze it in an iterative fashion using its built-in FEA solution until the specifications were met. In this case SolidWorks was unable to verify that its built-in FEA solution was correct. A more advanced version of the FEA solver would have been required; concomitant with more advanced engineering skills.

Chiller exported to Autodesk Revit

The latest release of SolidWorks added some BIM exchange capabilities, but Inventor’s BIM data transfer capabilities exceeded SolidWorks in key areas important to building designers. These included specifying connection points and component types that are carried over to the BIM-designer’s software. In addition, the mechanical designer using SolidWorks had a more difficult time orientating the model and simplifying a non-native model for export.

Bell housing

Our test of CATIA interoperability and direct modeling on imported models reiterated the widely known issue that SolidWorks does not directly import a native CATIA V5 file, even though both products are part of the same company. Direct modeling was comparable for both Inventor and SolidWorks, with SolidWorks being a little easier to use for the simple direct model changes we made. The SolidWorks drawing output in DWG format produced an incorrect dimension in a scaled view.

Copies of frame along a path

For design automation, our tests revealed two weaknesses of SolidWorks. SolidWorks with DriveWorks Xpress was not able to automatically scale drawing views to fit a part within the confines of a drawing after the size of the part was changed. Manual intervention was necessary. A second weakness was shown when scaling a copied assembly using 3D curves to define key points as the assembly was copied and scaled to other planes. Inventor was easily able to scale a copied assembly using drive curves; SolidWorks could, but required significant manual effort.

Electrical schematic and assembly

Both systems proved to be comparable in mechatronics where we tested the ability to build wire harnesses using schematic input from electrical software packages, albeit Inventor was able to do so with many fewer interactions.

Conclusions

Ray Kurland, President of TechniCom, knew that the tests were meant to highlight Inventor strengths, but was surprised that SolidWorks Premium 2011 was, in many tests, not able to do the work without adding pricey third party software. Duplicating Inventor’s capability on these tests with third party products will also make SolidWorks substantially more expensive than Inventor.

These seven tests underscore our contention from our previous Delphi Expert Analysis, that Inventor is a mature system that can more than effectively compete with SolidWorks and should definitely be considered for even the most complex situations.

The Inventor workflows illustrated in this series of tests are integrated and highly logical, enabling users to accomplish their design goals with minimal effort. Beyond that, we hope to have shown the value of Autodesk’s digital prototyping emphasis, which we expect will continue to evolve even further.

“I didn’t know that Inventor had this much functionality,” said TechniCom Group’s associate performing the tests, a CSWP. “I know that they acquired a lot of technology over the past few years, but I am surprised to see it all integrated so well into Inventor.”

Overall, TechniCom is most impressed with Inventor and the direction Autodesk is taking for the future. To keep abreast with our continued tracking of the industry and our reactions to Autodesk’s direction we advise readers to follow our blog and twitter feeds.


[1] “Comparing the Capabilities of Autodesk Inventor Professional 2011 and SolidWorks Premium 2010 Using TechniCom’s Delphi Expert Technique”, 9 August 2010, a paper by TechniCom Group, available at http://www.cad–portal.com.