3-D Modeling

By Claude Goguen, P.E., LEED AP

Communications play a vital role in precast concrete manufacturing, and a significant amount of critical information is communicated on plans and drawings.

Owners need a structure to fulfill a specific function. Engineers and architects analyze concepts and create designs. Precasters study those designs and create shop drawings for approval and plant fabrication. Plant employees read the shop drawings to fabricate the formwork and reinforcement and place blockouts and inserts. Contractors on site look at the site plans for guidance on how to properly install the precast structure.

Did the owners get what they envisioned? The answer to that depends on numerous interpretations of mostly two-dimensional diagrams and drawings.

While evolutions in design and drafting software certainly are enhancing communication, imagine how valuable it would be to see the finished structure before it is poured and hold it in your hands ahead of time.

3-D modeling can accomplish this, and it’s easier and more affordable than you might think.

For the Precast Manufacturer

Depending on a precast structure’s complexity, it can be challenging to convey a finished product using a two-dimensional drawing. Even a three-dimensional drawing does not allow for rotations and views from different angles.

Kirby O’Malley, president of Garden State Precast in New Jersey, sees these challenges regularly as his company often manufactures large, complex structures. Not long ago, he visited a supplier and happened to see its 3-D printer.

O’Malley asked about what benefits the company sees from having 3-D capabilities, and a light went on.

When O’Malley got back to Garden State, he asked his engineering manager, Rob Romanow, to look into 3-D printing. Romanow did some research and recommended buying a Prusa i3 MK3 3-D Printer. Its build volume is 8 ½-by-8 ½-by-10-inches and uses a variety of polymers and colors.

After a few weeks of training, Garden State Precast now had a new tool in its arsenal.

Garden State Precast first used the 3-D printer to create a model of a large stormwater netting chamber. The finished structure would be comprised of many separate sections, so Romanow entered the design into a 3-D CAD software program and used the 3-D printer to print the miniature components.

This allowed design and production personnel to hold each component in their hands and see how they were assembled, helping designers envision how the products could best be poured, lifted and handled at the plant and assembled in the field.

On another project, Romanow printed mesh reinforcement cage models and traffic barrier forms to see how the cages would fit in the forms.

“It’s really helped us with process planning,” Romanow said.

Garden State Precast also has been using 3-D models to help installers. Models of three-sided, 29 3/4-foot-span-by-14 1/2-foot-rise box culverts were created to show an installer where the various pick points would be to demonstrate how to unload, place and pull together the culvert sections.

“It was so useful that customers now are requesting models so they can have them on site,” said Romanow, who now prints models with multiple colors using different colored filaments.

Romanow also uses the printer to create small blockouts that would take more time and effort to make in the plant.

The printer and software cost about $1,000 in late 2019. Filament is about $25 per roll and may last for several prints depending on model size.

For the Precast Industry Supplier

ALP Supply Chief Operating Officer Christian Rescate bought a 3-D printer a few years ago with no upfront plans on how it would contribute to ALP’s operation.

ALP has begun using the printer to create prototypes to help with research and development.

“It helps us flush out many unknown issues up front and develop a good proof of concept.” Rescate said.

It’s helped so much that ALP has since purchased a second 3-D printer to give them more options and enhance creativity. Sometimes, Rescate sets up a print job and lets the printer work overnight.

One of the printers has a webcam built in so Rescate can use an app and monitor the printer’s progress from his cell phone.

“We print out prototypes of parts and products, and the sales team can take those to customers to show them how it would look and assess if it could be used in the products,” Rescate said.

ALP even has used 3-D printing to help in repairs.

“We had a piece of equipment that needed a replacement part, and we couldn’t wait, so we took the old part, measured it, created a 3-D CAD drawing and printed a new one,” Rescate said. “The part has worked fine ever since.”

Rescate said 3-D printing has been especially valuable in research and development.

“It keeps a project moving along by quickly revealing potential fitment issues on a prototype, and then you can quickly print another and try again,” he said. “It’s like the saying goes, ‘Bad news early is good.’ 3-D printing has allowed us to see that bad news early and accelerate our timeline from concept to finished product.”

Afinitas has been using 3-D printing for about seven years, primarily to illustrate entire plant layouts with all the production equipment placed appropriately, according to Dave Stoller, vice president of engineering.

“This aids in prospective customers being able to understand machinery layouts, production flows, personnel requirements and plant service requirements,” Stoller said. “We also do some design work with 3-D printed models to verify complex parts such as castings and injection molded items.

“These models are regularly displayed at trade shows, including The Precast Show, since the scale of our equipment is typically very large.”

Types of Consumer 3-D Printers

Most common consumer 3-D printers operate in one of two ways. They either deposit layers of material in small beads, or they create the solid structure from within a liquid-filled enclosure.

Fused filament fabrication (FFF) or fused deposition modeling (FDM) printers feed a filament made of thermoplastic, metal wire or a similar material into an extruder, which heats the filament and deposits beads of material along a predetermined path, fusing each layer together to eventually form the finished product. The structure is printed on a plate or bed. Some newer printers use pellets instead of filament.

Stereolithography (SLA) devices print objects using a liquid resin. The product is printed upside down as a laser selectively hits the photosensitive resin from the bottom up, curing or hardening the material. The process continues outward until the entire object is completed. There are digital light processing (DLP) printers and Mask Stereolithography (MSLA) printers that operate along the same principle as SLA printers. However, they use LED and LCD technology to cure the resin.

SLA type printers are generally more expensive, as they produce a higher quality finish, but FFF printers are easier to use and offer more material and color variety.

How they Work

Most 3-D printers work using the same process.

A CAD drawing of the 3-D model must first be created. You could create the design yourself using a variety of programs such as AutoCAD, Google SketchUp, Onshape and Solidworks. You also could search online to determine if your design already may have been created. There are many sites that contain thousands of model designs, including Thingiverse, MyMiniFactory and GrabCAD.

Then the 3-D drawing is converted to an STL or OBJ file, which facilitates the device’s reading of the object shape. Slicing software is then used to determine layering, tool path and other functions. During this stage, a user can adjust print speed, product size, orientation and nozzle and bed temperature. Users also can control the amount of infill in thicker sections. To save printing material, thicker sections can have different degrees of infill.

The slicing software typically comes with the printer. However, there are many software options on the market, such as Simplify 3D and Ultimaker Cura.

The printer then proceeds to create the model. There is a learning curve involved, especially when printing certain shape configurations. For example, when printing a box culvert, the model’s print orientation would have to be on its side. If one were to try printing it as it would stand in the field, the material would sag in the middle as it would not have the proper support.

Sometimes, there may be no orientation that will satisfy a lack of support in a hole or overhang. In those cases, temporary bracing can be included in the 3-D drawing and later removed from the end product.

A potential game-changer on all scales

NPCA is fully engaged and monitoring larger scale 3-D printing and additive manufacturing developments to gauge potential applications in manufacturing. Some in the precast industry already are on board. Gate Precast used 3-D printing to make molds to manufacture wall panels for the Domino Sugar Factory residential building.

Hamilton Form Company uses the technology in its form fabrication process.

“We have used large scale 3-D printing to make complex forms,” said Bob Mills, who works in marketing and product development at Hamilton Form Company. “When the required geometry is not practically accomplished in steel, we have had mold components printed and machined. Those components were then enclosed in a steel framework for production.”

For smaller-scale printing, consumer device choice is expanding, and prices have dropped where some printers can cost as little as a few hundred dollars. As printer technology advances, so will the number of potential uses for precast manufacturers and suppliers.

Consider the added value of manipulating a scaled-down model of a finished structure in your hands before you touch the first piece of formwork or reinforcement. How could that enhance communication and avoid issues during production?

Imagine being able to bring models of manhole sections, a wastewater treatment system, retaining walls, a short-span bridge or a parking garage structure to a specifier.

Think of the potential of having such models available at plant tours, trade events and outreach presentations.

Envision the impacts 3-D printing could have on product research and development.

“I can directly attribute our use of 3-D printing to increasing revenue due to its impact on R&D and quality control,” Rescate said.

The technology is here. It’s accessible. The only question that remains is: Are you ready to venture into another dimension?

Claude Goguen, P.E., LEED AP, is NPCA’s director of technical education and outreach.