April 28, 2009
This technical article from TRUMPF takes a look at how parts can be redesigned to include less material and to be processed much more efficiently.
Modern machine technology has changed in the past decade. But have your designs kept up?
Now might be a good time to reassess existing designs for cost savings and optimal equipment utilization. The best part of this type of reassessment is that it doesn't require investment in sophisticated software or expensive consultants.
A healthy dose of contemplation and creativity, along with innovative thinking, can go a long way toward achieving cost savings when it comes to sheet metal design or, in this case, redesign. Also, don't dismiss intuition, as it too plays an important role in the reworking of a workpiece.
It's generally assumed that when reinventing an existing part, the designer's chief intent is to fashion something that is still effective, yet more efficient than its previous incarnation—whether efficiency is defined as a reduction in weight, an increase in functionality, a way to improve manufacturability, or as a cost savings. And sometimes the definition does not fall under any of these areas and is unique to that particular part. No matter. With a redesign as your ultimate goal, now is the perfect time to unleash those creative juices to help determine the best approach to your cost-savings project.
But wait. You have a case of sheet metal redesigner's block, you say? Not to worry.
If you're drawing a blank, the best way to tackle the task is to first launch the left side of your brain. Initially you will want to spend some time thinking about how the original part was designed in the first place and revisiting the purpose that it actually serves. Once you're on solid ground with that basic information, switch gears and enlist support from the right side of your brain, your creative control center, to figure out how to design it better.
Unfortunately, that's often easier said than done.
One of the most effective methods for working through a creative void and tapping into your ingenuity—and the thing that causes a slight panic among students who go through a part redesign course—is to begin the redesign process with nothing but a clean slate.
When walking into a setting without computers, desks, and drawing board—all traditional tools in the designer's cache—a part designer has no choice but to call on ingenuity. While it seems difficult to believe, the lack of traditional tools indeed will yield to a tangible outcome of a redesigned part that almost always involves cost savings.
What are the tools needed for this exercise? Sheets of paper, scissors, adhesive tape, and a conference table.
Like sheet metal, paper can be cut, bent, or joined. It allows the part designers to create 3-D models that bring their project to life.
What looks like an art class in origami is really an exercise in redesigning a part for cost savings (see Figure 1). With an authentic customer part as the model, you can re-create the part using these simple tools, which often leads to the elimination of many of the single components within that part.
So how does this exercise work? Let's examine some key components of such a project.
One of the most basic, and probably one of the most important, tenets of manufacturing is to eliminate as many welds as possible when trying to achieve cost savings. Replacing the welds with bends during the exercise, or eliminating them altogether, typically results in the greatest cost savings. In this type of exercise, it's possible to reduce the number of welds from 50 to 100 percent. You can imagine the impressive cost savings this would achieve in real-world situations.
When this type of part redesign effort is open to all within a company, it's interesting to observe that some of the most innovative and effective paper designs come not from trained engineers, but from machine operators or others. Each works on developing solutions to the same problems; however, it's always fascinating to see the many different outcomes. Not only does this provide an authenticity to the project, but it also gives everyone an opportunity to see the kind of tangible impact a part redesign can have on the company.
Once a paper design is complete, it is gathered and evaluated by the exercise leader and the participants. The part is then created in CAD and then transferred to CAM. CAM software helps the group visualize the fabricating technologies talked about in the class before the files are transferred to machines for production.
In addition to eliminating as many welds as possible, a part "redesigner" needs to consider the type of materials used in the product. The raw material is an important factor when addressing the issue of redesigning parts for cost savings.
For example, a workpiece may have been fabricated with aluminum to allow for easy machining. However, using sheet metal in the redesign will result in a significant cost savings because cheaper materials such as steel can be used instead of aluminum.
Material substitutions abound; however, something to remember is that their use in a redesign can't be based solely on their face value. All elements of the process must be factored into the equation. For example, how will the part be created? Generally speaking, eliminating a process such as milling will result in a cost savings. In Figure 2, a redesigned proximity switch bracket resulted in a cost savings of 75 percent. The original design called for two milled aluminum parts, approximately 100 mm by 40 mm by 40 mm in size. The redesign resulted in a single steel part that called for simple two bends.
Bent metal is strong, and flat metal is not. So incorporating solid corners and bent flanges strengthens a metal part (see Figure 3).
That, however, leads to another important component to consider during the redesign process: the weight of the fabrication. Once again, it's the design itself and not the sheer weight of the material that is the determining factor in the redesign, but if the final fabrication has moving parts, those will generally perform better if they weigh less.
These are just some of the elements to keep in mind during the all-so-important design phase. After all, it's the initial groundwork that lays the foundation for additional cost savings at later stages in the production process.
The FABRICATOR® is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The FABRICATOR has served the industry since 1971. Print subscriptions are free to qualified persons in North America involved in metal forming and fabricating.