Manufacturing

Is RM Finally Ready For Prime Time?

9 Aug, 2007 By: Jeffrey Rowe

Stratasys addresses some of the typical roadblocks with its new direct digital manufacturing system.


Those of us involved in engineering and technology are always looking for “the next big thing.” Over the years, some of these technologies, such as bringing FEA to the masses, have panned out, while others, such as concurrent engineering (a term that seemed to defy definition, later replaced with PLM), have not. Rapid manufacturing (RM) is one technology that seems like it has been just around the corner for a number of years.

The main issues that have held RM back from fulfilling its promise are the RM machine itself (with concerns related to production speed, accuracy, and repeatability) and the RM material used to produce parts (with concerns about mechanical properties or lack thereof). The new Stratasys FDM 400mc system (pricing starts at less than $100,000), however, is addressing these roadblocks and may nudge RM into reality.

First let me clarify exactly what RM is for the purposes of this discussion. In his book Wohlers Report 2007, Terry Wohlers defines rapid manufacturing as “the direct production of finished goods using additive fabrication techniques. Additive processes produce end-use parts directly from digital data, thus eliminating all tooling.” That definition is pretty comprehensive and one that most (including myself, since I wrote a section of the report) would consider valid. Yet today most RM parts are relatively low volume and used for prototyping purposes.

Fused Deposition Modeling
I recently spoke with Fred Fischer, product marketing manager at Stratasys, about the FDM 400mc (the “mc” stands for “manufacturing center”) as it was being introduced to the public. He said that the new system was proof of the company’s commitment to RM, or what the company calls direct digital manufacturing. The FDM 400mc employs fused deposition modeling (FDM) technology and was designed for use both for rapid prototyping and RM, so if nothing else, the machine is flexible.

On the manufacturing side, Stratasys addressed the two main objections to RM. First, the machine itself was designed specifically with manufacturing in mind with higher levels of throughput (the company claims an average 29% increase in throughput when compared with its T-class machines -- the Vantage and Titan -- that this system will ultimately replace) and accuracy (precise data on the accuracy claim is still being compiled by Stratasys). Second, the system was introduced along with a new material, ABS-M30, which reportedly has significantly improved mechanical properties.

The Stratasys FDM 400mc system


The FDM process basically consists of heating plastic in an extrusion nozzle that allows the flow of a bead to be deposited in horizontal and vertical dimensions, building a part layer by layer. According to the company, because stable thermoplastics are used, there is virtually no warpage, shrinkage, or moisture absorption as with the resins used in some competing processes, resulting in more dimensionally accurate parts.

The base model of the FDM 400mc system has a build envelope of 14” x 10” x 10”. Customers can also optionally upgrade to a larger build envelope that measure 16” x 14” x 16”. It builds on the existing Vantage and Titan systems, but with significant improvements to the mechanical, electrical, and electromechanical subsystems, such as more precise alignment of mechanical components. The FDM 400mc supports the following slice (layer) thicknesses: 0.005”, 0.007”, 0.010”, and 0.013”; generally, the smaller the slice, the more accurate and aesthetic the resulting part.

Material Testing
For RM, the material being processed is as important as the system doing the processing. The company has performed extensive testing and claims that the new material, ABS-M30, is 25-70% stronger than standard Stratasys ABS with greater impact, tensile, and flexural strength. Layer bonding is also stronger, making for a more durable part that is more suitable for functional testing and end use. The material is available now only in an off-white color, but other colors should be available by the end of the year. Initially, the FDM 400mc can also process polycarbonate (PC), PC-ABS, and polyphenolsulfone. The company says other materials will be added to the list in the near future.

As important as some other attributes are for systems of this nature, part repeatability is also a key factor to consider when manufacturing multiple copies of a part. Extensive testing by Stratasys indicates that the FDM 400mc produces predictable, repeatable dimensional results when a part is produced in different runs in different build platform locations from the same system. The company has also proven that multiple systems can produce parts with repeatable dimensional accuracy when parts are built on different systems.

So, is the FDM 400mc the system that will finally prove that RM is ready for prime time? That’s hard to say at this point, but Stratasys is certainly doing what it can to ensure its place in RM’s industrial revolution.


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