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Additive manufacturing machines are sold on the basis of convenience (“you can 3D print at the push of a button”) and cost (“complexity is free”). In reality, the cost of 3D printing, especially in metal, can be quite costly.

Champions of 3D printing and vendors of 3D printers argue that due to the machines placing material only where it is needed, companies will save on the cost of material. They argue that parts manufactured traditionally—whether by machining, casting or molding—are overdesigned, using more material than is necessary.

“A part that has had its shape optimized and 3D printed can easily save 50-60 percent in material,” says Daniel Pyzak, whose official title as CATIA Mechanical Engineering Worldwide Industry Process Success Manager for Dassault Systèmes hardly does justice to his grasp of the emerging technology that his company puts into its design and engineering application.

We reach Pyzak at his home in Saint Remy de Provence, France. It is well into his evening, but Pyzak’s enthusiasm for incorporating leading-edge technology in Dassault Systèmes CATIA and its 3DEXPERIENCE platform is undiminished. He reminds us of Doc Brown and we expect him to hold up a flux capacitor; instead, he shows us a part for a satellite. The part is a support bracket for a parabolic dish. It has been optimized and will be printed in metal.

Why So Much?

We ask what, in Pyzak’s experience, contributes to the expense of metal 3D printed parts.

“Well, metal 3D printers cost a lot of money,” he says.

Of course! That seems so obvious now. The cost of metal 3D printers is the first, and most formidable, barrier engineers have to overcome before they can realize any of the benefits 3D printing promises.  Metal 3D printers, as big as a walk-in closet and as expensive as homes, have to be factored into the cost of the part. This also limits implementation of 3D printing because only big companies can buy metal 3D printers and only the larger service bureaus can offer metal 3D printing to their customers.

As for all the industry claims that a 3D printer will produce a part exactly as designed: that is kind of a myth, according to Pyzak.

As anyone who prints their first metal 3D-printed part soon discovers, what was designed is not at all what is produced by the million-dollar 3D printer. The changes in state from powder, to liquid, to solid play havoc on the shape of the part. Powder melted with laser produces pools of molten metal that cool and solidify unevenly. Contraction during solidification will distort the shape of the part and can permanently lock in stresses. Therefore, a part design that is fed into a 3D printer is almost invariably a distorted part when it cools. If the distortion is severe, the part will not pass inspection.

The changes of state, heating and cooling, expansion and contraction all combined with other variables such as a unique shape, the variation in temperature and orientation of the laser, the speed of the print head, the thickness of each layer, etc., have made for an unsolvable calculation. The industry has had to resort to trial-and-error methods, iterating on part shape. You know the first part will be wrong, but you print it anyway to get an inkling of how it will distort. Then you change the CAD shape to compensate for the distortion. But if getting a hole-in-one is impossible, an eagle (2 attempts) is only improbable. So, it’s wash, rinse... and repeat.

This is a process that contributes greatly to cost and extends timelines. The satellite bracket Pyzak is showing us took 40 hours to print.

“That’s a lot of time to tie up for a very expensive machine—and lot of time for something to go wrong,” says Pyzak, before adding, “And you don’t have to do that anymore.”

“We’ve figured it out,” says Pyzak. “The part shape, the wrong part shape that will be the correct part shape after it comes out of the 3D printer and cools, is a solved problem.”

To solve it, Dassault Systèmes drew on its own experience figuring out the shape that had to go into a brake or stamping setup that would result in a shape that would pass inspection.

“We solved springback years ago using our SIMULIA applications,” says Pyzak. “A sheet metal part has springback, so we must calculate the correct wrong shape so that after the part is formed and springs back, it is the correct design.”

“When the material is known to us, we can do the same for 3D printing and predict distortion accurately by simulation during the manufacturing,” Pyzak continues. “If the material is not known, you may need to sacrifice the first part out of the printer. You feed the design shape into the 3D printer and let the part be distorted. Then you can 3D scan the distorted part and feed it into the 3DEXPERIENCE platform. From the difference in the design shape and the distorted shape coming either from the SIMULIA prediction or the ‘as built’ scan of the first printed part, CATIA will be able to calculate a shape that compensates for the distortion that is sure to follow. The result: a part that, when all said and done, is exactly the designed shape.”

“Others do this,” admits Pyzak. “But we are the only ones who do the morphing of the shape on the solid. Everyone else does the morphing on a mesh. The problem with working on a mesh is twofold. First of all, the mesh has to be very fine, so you have a lot of computing to do and long run times. Second, if the shape changes a lot, the only accurate way is to morph the solid, not the mesh.”

Knowing the correct wrong shape in advance saves time and money. Engineers will get the right part sooner, without trial and error.

Optimizing for Support

“As much as half the cost of a part is in the finishing,” says Pyzak, referring to the post-processing that has to be done on a metal part after it emerges from the printer. Most of that has to do with the supports.  “You spend a lot of time adding the supports to the model shape, then you spend a lot of time physically removing them.”

Supports are added to the model under “overhangs,” those features that are less than 45° from the horizontal plane. Because the part is soft as it is getting built layer by layer, it cannot support itself. Thin vertical columns are added to the imported CAD model underneath the overhangs, using 3D printing software. The supports can be tapered to a point where they meet the part so that they can be broken away by hand, but they still leave a bit of material that has to be filed off, adding manual labor and an extra step. The supports can theoretically be recycled, but it would take too much energy and effort to turn them back into the powder they started as, so they usually end up as scrap.

“The powder metal used for 3D printing is not cheap,” says Pyzak, setting us up for what is a better way.

“Why not orient the parts so they don’t need supports—or very few supports?” he offers. “We can do that in the software.”

As proof, Pyzak shows parts being created in a 3D printer vertically.

“You may think laying a part down flat is best, that by lying flat a part would require the least number of supports, but that may not be the case,” says Pyzak. He shows one part built vertically that requires only a couple of supports.

“This is done in the software,” says Pyzak. “CATIA can optimize the weight of a part, maximizing it stiffness and in case of a 3D printed part, generate a shape with the minimal are to be supported.”

Indeed, optimization of part orientation (to avoid supports) would be a godsend to any engineer or designer.

To Marketplace

Use of an engineering and manufacturing marketplace, such as the 3DEXPERIENCE Marketplace, may result in getting the part sooner than if it was 3D printed in house. Online marketplaces offer a selection of 3D printing services and those with years in the business will have a staff experienced in orienting and packing parts. Such a service will avoid the learning curve for product engineers. Engineers are typically hard pressed to deliver innovative products in ever-shortening design cycles and have little time to master fast emerging technologies. They may be teaching themselves 3D printing or doing it so infrequently that never get skilled-- and end up frustrated and wasting time.

To help engineers keep to what they are best at, Dassault Systèmes has added services in addition to 3D printing and CNC machining services to its 3DEXPERIENCE Marketplace. Engineers can avail themselves of services outside their comfort zone, such as industrial design and optimization – including part orientations and stacking optimization discussed in this article.

Use of a marketplace can also help reduce the cost of 3D printing. With an online marketplace, engineers are no longer bound to local vendors and can shop around. The competition can bring down the cost of the 3D printed part. Several vendors in a the 3DEXPERIENCE Marketplace provide instant pricing, making comparison shopping easy.

Learn more about 3D printing on demand on 3DEXPERIENCE Marketplace by Dassault Systèmes.