Manufacturing macro and micro designs

Oct. 10, 2002
Software streamlines the design of progressive dies as well as micromachines.

The complex progressive die was designed with Progressive Die Wizard. Users start with solid models of proposed parts in any translated CAD format and follow the sequence in the user interface to complete the die. Developer EDS says the wizard is built on the knowledge and best practices of industry experts. One company says it now completes three weeks of progressive die-design work in three days.

The stages in the forming of a bracket show several steps, such as scrap design and strip layout. The progressive die wizard assists in planning each step of the progressive die design, from maintaining intelligence of imported 3D models to material behavior, blank and scrap design, and process planning.

Efab builds complex shapes such as these coils for small high-Q inductors, magnetic actuators, and transformers. So far, tolerances for the process have been better than 0.0001 in. Design guides for the process can be described in one page.

Efab handles a patterned electrodeposition of one material using an Instant Mask, followed by a blanket electrodeposition of a second material. Where conventional processes take one or two days to generate a single pattern layer, Efab generates patterned layers in 1 to 2 hr. This makes it possible to produce over a dozen layers in a single day. Complete build times are generally a matter of days, not weeks as with traditional methods. Etching away the sacrificial material releases the device.

Over the last decade, software developers have chipped away at the mundane chores that every manufacturing shop deals with — testing toolpaths, data management, and tracking machine and material use. These chores were relatively easy to automate compared to those that need solving in the next 10 years.

Difficult tasks now seem clustered around large jobs and small products. For instance, EDS, Plano, Tex. (, has released its Progressive Die Wizard that designs complex tools more creatively and with less manual labor. And for designing micromechanisms, MEMgen, Burbank, Calif. (, has delivered a sort of factory-in-a-box, a self-contained package that solves several problems associated with making MEMS-sized devices.

A software wizard helps those designing progressive dies tie the many operations together into a streamlined workflow. EDS' Progressive Die Wizard brings a needed dose of automation to what has been a largely manual task. It also improves productivity by a factor of three or more. EDS says the wizard captures industry-specific knowledge and turns complex elements of design technology into automated sequences.

Stampings from progressive dies are mostly used in computers, electronics, automobiles, and electrical devices. The dies transform metal strips into formed parts. A series of stations cut, coin, form, and bend material into required shapes. Die components make precision-cut openings in plates. A press moves dies up and down, feeding material as it progresses from one station to the next. What's more, every die design is different and some simultaneously produce two or more different parts.

Traditional die design is a series of time-consuming and expensive manual operations. Modifications to parts have to be manually rerun through the entire process because there is no associativity between different systems that might be used. And the whole operation takes lots of design knowledge and years of experience.

"The Unigraphics Progressive Die Wizard uses intelligent automation of industry-specific processes and requires no other software or operations," says Hilde Sevens, a spokesperson for EDS. "The wizard is a complete system for designing progressive dies. For instance, right from the start, it has tools that turn dumb solids, such as those from IGES, into more usable feature-based solids," she adds. "It has die-making expert knowledge. But it's also flexible enough to incorporate special customer requirements."

Following the series of icons in the wizard toolbar takes engineers through the industry's best practices. These include, for example, ways to organize the design, create the blank, design scrap, and layout the strip.

The system extracts sheetmetal features and maps them to process features that represent a company's design standards. Blank-layout design tools position the unfolded sheet metal on the metal strip while checking material use. Strip layout plans process features in many operation stations. When finished, simulation for the 3D strip layout provides feedback to design and process changes. The software does not presently animate the die, but shows how finished parts will be created. From that, users adjust the dies to produce exactly what's needed.

The wizard's customizable library has die bases, standard parts, and insert groups to expedite die-structure design. The system holds its knowledge in spreadsheets in English and standard algebraic equations that formerly resided only in the minds of senior die designers. Changing a process or tweaking spreadsheet values takes no programming. Sevens says the system lets less-experienced designers turn out expert work. And experienced designers quickly gain higher proficiency levels.

Some experts say micromachines are set to become a key technology. These small devices are measured in microns, easily sit on the head of a pin, and can include electric motors, gears, and electronic controls. But traditional manufacturing methods work mostly with silicon, take weeks to produce, and cost a bundle in small lots.

For instance, designers lay out conventional MEMS with as many as five 2D patterns, and then rely on process tricks to generate extrusions or other projections to shape the part. Only 3D extrusions or projections permitted by the particular process can be made, and typically, a new fabrication process has to be invented to generate each new geometry.

A manufacturing tool called Efab Manufacturing System from MEMGen may change all that with a batch process that builds MEMS and larger micromachines in small lots, shorter periods, and out of almost any metal that can be electroplated. "Efab technology uses a self-contained machine to fabricate small devices," says Chris Bang, director of application with the company. "These can be on the scale of MEMS in terms of microns, and larger, measured in millimeters. What's more, design models can come from standard CAD packages, and the machine can be run on factory floors by nonspecialists. No clean rooms are necessary."

The Efab system is similar to rapid prototyping in that models are read into the system in STL formats, an output of most CAD systems, and then sliced into a number of layers. But similarities end there.

"Layers are built by electro-deposition using patterning technology called Instant Masking," says Bang. "It's tooling built for each layer because the process uses no lasers. But it lets us shape a wide variety of metals — nickel, copper, gold, or platinum — anything that can be electrodeposited." Few RP machines work with these metals. The Efab system generates microstructures quickly and without the need for slow and repetitive photolithography steps. The mask makes it possible to deposit an unlimited number of independently patterned layers which form arbitrary, complex 3D shapes, thereby overcoming limitations of conventional microfabrication.

The mask is an "electrochemical printing plate" that contains images of all the cross sections of the microdevice to be built. "This tooling is placed between the substrate and material to be deposited," says Bang. "It's covered with a patterned insulator, all in a plating solution. An applied voltage transfers material from the mask to the substrate. The material becomes a layer of the part. A second material electroplated later onto the substrate covers the previous layer completely. The two materials are planed to produce a single two-material layer. The process repeats, adding layer upon layer until all cross sections of the design are constructed. The sacrificial material is then etched out, revealing a complete, fully assembled part. "It's faster than photolithography used in the MEMS industry," notes Bang.

Many sacrificial and structural materials could be used, creating complex multimaterial devices for specialized applications. So far, the company has produced electronic devices such as a filter for gigahertz frequencies, optical parts, and surgical tools.

The Efab technology's advantage, says Bang, includes making small components available to non-MEMS engineers. It's scalable so it ramps quickly, and can accommodate low to high-volume runs. In addition, it's more flexible than silicon. It also speeds design iterations and minimizes dependence on elaborate simulations. And part changes do not require manufacturing process changes.

Typical devices produced with the Efab system can be taller and have footprints somewhat larger than conventional MEMS. "The process is evolving so we have not established a minimum feature size or layer thickness," he says.

The company expects to add new capabilities, materials, and technologies to lower barriers between the micro and macro world. Initial product development will focus on providing metal micromachines to a select group.

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