Additive Manufacturing, Topology Optimization and 3-D Printing

Additive manufacturing (AM), topology optimization and 3-D printing have produced some remarkable changes in the manufacturing sector, enabling companies to make parts whose geometries would have been all but impossible using traditional techniques. Still, being a relatively young technology, AM faces some challenges before it can enjoy more widespread use.

One of our largest customers has categorized these challenges, in order of importance to them:

1. Build volume (the size of the part that they are able to make): While tiny and complex is interesting, large and complex is where the money is.
2. Build speed: Even with a new facility with 100 DMLS (Direct Metal Laser Sintering) machines to print one part, 24 hours a day, every day, this customer can’t manufacture parts fast enough to keep up with demand.
3. Build failures: These are caused by thermal distortions, build plate connection failures, interference with the powder spreading mechanism because of distortion, etc.

We’ll discuss the obstacles and potential solutions for the first two of these items today. In a future blog, we’ll take up the issue of build failures and one other industry-wide concern:

4. Confidence in the material properties being produced: How can we be sure that a part made using AM has consistent mechanical properties throughout the part?

Let’s take a closer look at the first two issues.

Additive Manufacturing and Build volume

Parts made by AM tend to be tiny. These parts have incredible resolution, with details that could not be made by any other process — not casting, and not subtractive machining. Metal AM started out as a bit of a novelty item, great for printing desktop trophies to show things like metal lattice structures balanced on the head of a dandelion gone to seed, but not really very good at printing parts that actually did anything useful. Where was the problem, why were the build volumes small?  The difficulty was in scaling up the internal mechanisms for the DMLS machines — the powder spreaders and the laser controls.  Making these mechanisms larger while maintaining the incredible resolution required to produce precision parts proved to be problematic.

Highly-detailed Additive Manufacturing part

But that’s changing, and relatively quickly. Smart engineers are producing ever larger control and material handling systems, while maintaining the precision for which the AM processes are known. ExOne, for instance, is producing machines that print not the part, but the mold for traditional casting, and these molds are nearly the size of a pickup truck bed. Also, DMLS machines, the predominant commercial choice of aerospace companies, are getting larger and larger, so much so that it’s possible to print multiple versions of the same part at the same time, with no loss of the precision that would sacrifice surface finish, material properties, etc. It’s obvious that engineers are quickly solving the scale-up challenge.

Additive Manufacturing and Build speed

While the precision parts, particularly in metal, that are coming out of today’s AM machines are marvels to hold, spin, bolt to your car, etc., it can be maddening to watch an AM machine at work. Many builds take up to 8 hours. Two of the biggest factors in build speed are layer thickness and laser travel velocity. Smart companies have already started tackling this problem from a number of different angles. Several companies have put multiple lasers in the same machine, with multiple control mechanisms. Productivity scales nicely when you do that. So, if one laser is good, and two lasers is better, then what about three?

This reminds me of the razor blade wars that went on for a while. For many years, there was one razor, then there were two and it was a huge breakthrough in shaving speed and reduced bloodletting potential. Then there were three blades, then four. I have no idea how many blades are in vogue now, whether they are stationary, or vibrate or what, but it’s billions of dollars in market value for something that seems pretty simple, in hindsight.  (Why didn’t I think of that?)  But, back to the point, Additive manufacturing production speeds are going up rapidly, and, no coincidence, so are the number of AM parts being put into service as final production parts.

So, additive manufacturing may have some problems, but problems with great promise attract great minds, and these minds are knocking down the barriers faster than most thought possible. Some forward thinking companies are racing into the age of additive manufacturing, while others are cautiously optimistic and taking a wait and see approach.

Additive manufacturing at the University of Pittsburgh

Optimized topology using ANSYS Mechanical (created by CADFEM for ANSYS)

Also, the recently released ANSYS 18 contains a new topology optimization feature in ANSYS Mechanical can define the region and loads for a given scenario or multiple scenarios, and let the solver use a physics-driven approach.

Attend the webinar on February 14th to learn about all the enhancements to ANSYS Mechanical, for additive manufacturing and for other engineering applications. And watch for our second blog in this series, in which we’ll tackle challenges 3 and 4 listed above.

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