If you design assemblies, chances are good that you have to deal with moving parts. You may want to find out if your clearances are adequate; you might want to determine the strength of a hinge; you might need to know if a cylinder has sufficient headroom, once the motor force is applied.
Pro/ENGINEER comes with powerful mechanism design tools such as a tool for checking clearances between moving parts – Pro/ENGINEER Mechanism Design Extension (MDX) – which is standard with the Pro/ENGINEER Foundation Advantage package. It allows you to move and animate your moving parts, without having to leave the familiar assembly design environment of Pro/ENGINEER.
But what about the other aspects of motion analysis – applying friction or custom loads and forces such as combustion, hydraulic loads and gravity? For this you can add on Pro/ENGINEER Mechanism Dynamics Option (MDO), a tool for exposing your assembly to real world conditions, without having to rely on multiple physical prototypes.
It would be nice, for example, to be able to add friction to a wheel bearing, so you’ll know with certainty that your design will hold up under the customer-specified conditions.
Here are a few things you should know about the powerful and complete motion analysis tools found in Pro/ENGINEER.
1. Motion analysis is easier than you think.
Many design managers, and even engineers, feel the price of admission for learning to perform motion analysis is too high to justify the benefit. But this is not the case with the mechanism design and dynamics solutions in Pro/ENGINEER.
With both MDX and MDO, you don’t need training on a new interface, because it is completely integrated with Pro/ENGINEER. You get multiple ways to do things – for instance, to put a part in motion, you can drag it, or you can build a motor to push it. And you get clear onscreen feedback at all times. For instance, automated vector arrows show where forces are being applied, and the arrows themselves will change size to indicate the magnitude of the dynamic forces in your assembly.
2) Motion analysis, integrated with Pro/ENGINEER, can save you time.
Pro/ENGINEER Mechanism Design and Pro/ENGINEER Mechanism Dynamics streamline your analysis and eliminate the time required to export and import your assembly data via IGES, STEP or other data translation standards.
If you want to analyze your design’s dynamics, but do not use MDO, you have to pass your design off to a colleague with a third-party motion-analysis or Finite Element Analysis (FEA) software package.
This transfer requires you to take extra time and effort to translate your data to the format that will allow you to then import it into another equivalent analysis tool. Once you get results that require you to change your design, you have to manually make the changes to your design assembly or export it out of the motion analysis software and back into your CAD package. This requires rebuilding the model, and can take anywhere from 15 minutes to a full day, depending on the assembly’s complexity.
With MDO, there’s no need for any data translation, since all processing, setup and analysis is done in Pro/ENGINEER, and all the motion definition is created and saved with the design model. This gives you more time for changing and fine-tuning your design.
3. You can measure different loading characteristics easily
MDO has tools for measuring both static and inverse-static loads. Together, these motion analyses will solve simple and complex loading conditions.
Static loading measures a non-changing load on a part. If you are designing a clamp-on desk lamp, for instance, you would use static loading to determine how much force the spring will need to keep the lamp clamped to the desktop.
However, if you are designing an automobile hood you would want to use inverse-static loading to deal with the greater complexities of designing hinges and gas pistons that will hold up the hood when required, and then let the driver, even a person with very little strength, close the hood. This is complex because it brings into play factors associated with balance, force applied by the person closing the hood and gravity.
4. You can create a CAM profile where no CAM exists
If you design internal combustion engines, you know that CAM and camshaft designs present distinct challenges involving not just motion, but things like friction slip and impact based on the “restitution” of materials during impact. Normally, CAM design requires numerous iterations – and physical prototypes – before it’s complete. But MDO enables you to build the CAM profile by first applying all these other forces to synthesize a CAM. You can then test the CAM for all conditions, and make iterative changes, without having to wait for physical prototypes or third-party FEA transfers.
5. You can dynamically transfer motion dynamic loads from MDO into Pro/ENGINEER Structural and Thermal
When you do need the additional analysis provided by Finite Element Analysis software, you can add the next step – Pro/ENGINEER Structural and Thermal – as a fully integrated solution. Using the automobile hood example again, MDO allows you to send the completed design model and the maximum and minimum forces on the parts to Pro/ENGINEER Structural and Thermal. This helps you determine the stress and failure characteristics of the hinges during use. And because Pro/ENGINEER Structural and Thermal is fully associative with Pro/ENGINEER and MDO, changes made in the FEA model will be immediately reflected in the original design, and vice versa. With each design change, you can quickly rerun the motion analysis, pass the new forces to Pro/ENGINEER Structural and Thermal and rerun the structural and thermal analysis, all without having to recreate and set up either the motion or structural analysis again.
Welcome to the real world. The motion analysis tools in Pro/ENGINEER, particularly MDO, can be an immense help to the designer of moving assemblies, according to Ric Leeds, PTC’s Product Manager of Assembly and Motion Products.
“Designers and the companies they work for are frequently finding that virtual prototyping improves the quality of the finished product and allows them to be much more competitive by speeding time-to market,” he says.
“If design engineers analyze their designs earlier in the product development process, they’ll perform more design iterations resulting in more innovative products. The more innovative the products, the better the products will perform in the market place.
So it makes sense that design engineers do as much testing as possible in the original design phase. That’s where MDX and MDO can make a real difference.”
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