As an MSC employee I often gain an appreciation for the complexity of everyday machines though my work, especially during my years in our Services organization building Adams models for our clients. But, sometimes personal experience illuminates such matters. And, occasionally, there is an overlap between the two. I returned home one day after starting a load of laundry a few hours earlier to find the washing machine got stuck on the spin cycle and my sheets had become very, very dry. Scorched, actually. While shopping for a new set of sheets and pondering what could have gone wrong, I realized how little I knew about how a washing machine actually works. Well, not for long. Shortly after, I found myself on a washing machine project at work.
After describing my job to most people they hear “computer simulation” and think spacecraft and airplanes, not washing machines. But, as I found out there are actually many complex aspects of washing machine design and function well-suited to multibody dynamics (MBD) simulation and several companies take advantage of the technology. A fast-spinning basket filled with heavy, damp clothes poses many design challenges including:
- Suspension: Its springs, arms and dampers must keep the basket from knocking the inside of the housing or causing unwanted vibration. MBD simulation is highly valuable whether one is optimizing the parameters of design (spring rates, arm positions and compliance, etc.) or evaluating wholly different design options (hung suspension, bottom mounted, etc.). Check out this example of suspension modeling presented at a previous Adams user conference.
- Balance Ring: If you use a top-loading washer, its basket likely has a solid, or even fluid-filled, ring mounted on top to counteract the force of an unbalanced load in spin cycle and prevent the entire washing machine from literally walking across the floor (and I thought I had it bad with my non-stop spin cycle!). MBD simulation helps engineers quickly evaluate the efficacy of balance ring designs in the face of different unbalanced load conditions. An Adams user presented this example of balance ring evaluation at a previous user conference.
- Brakes: Yes, some washing machines actually have brakes. Like their automotive counterparts, they are subject to performance requirements for certification. MBD simulation is used to evaluate the stopping time of different braking system designs as well as to provide loads to finite element analyses for evaluation of the component strength and durability. A very interesting case study of a customer using MSC Adams for brake analysis can be found on the MSC website.
- Drive System: Electric motor controls models can be integrated with the mechanical system model with the likes of Adams/Controls to provide a comprehensive evaluation of all it takes to agitate and spin that heavy payload. Perhaps my sheets could have been spared with more diligent design work here!
In addition to meeting engineering design challenges, washing machine manufacturers have a compelling business case for simulation. The intense pressure they face to quickly deliver new products to the market requires smarter, faster product development. Furthermore, there is naturally a need to minimize warranty costs by delivering a high quality product in those aggressive timeframes. Gosh, if I had known warranty claims were taken so seriously, maybe I would have tried to get my new sheets paid for.