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Aerospace composite tooling with LAST-A-FOAM® FR-4500: Soft tooling delivers hard benefits

When it comes to short-run, prototype tooling or tooling support for aerospace, composites prove their strength and value. They cost less than metallic or aluminum tools, reduce production lead time, and readily accommodate complex shapes.

Thanks to the material’s low weight, high strength and superb machinability, it’s no surprise that many aerospace customers rely on our LAST-A-FOAM® FR-4500 High-Density Tooling Boards for composite tooling. This highly engineered polyurethane foam series is time-efficient and cost-effective when used as a soft tool. It streamlines production, there’s minimal cleanup and no equipment damage.

Most valuable physical characteristics

LAST-A-FOAM® FR-4500 foams are designed and formulated to satisfy key aerospace composite tooling applications:

  • They can be processed at temperatures up to 200ºF, compatible with many types of resin systems.
  • The material is consistently uniform, durable and dimensionally stable. Boards will not warp, twist or bow – whether in use or over time.
  • Easy to machine using HSS cutters and create a very smooth surface finish.

“In densities of 30 pcf or higher, you can achieve a high level of detail and resolution on tooling, which is important when machining complex designs,” says Todd Roppo, General Plastics’ senior sales engineer.

These boards also have an anti-static characteristic. Unlike other foam tooling boards that cover equipment and shop floors with dust, our FR-4500 material creates shavings for a cleaner environment.

Common applications for composite tooling using FR-4500 foams:

  • Master models
  • Layup tool masters
  • Shop aids / vacuum holding fixtures
  • Part modeling and prototyping
  • Mold and foundry patterns

Master models

“Master molds and master models are commonly made from the FR-4500 foam for composite tooling,” Roppo explains. “Customers create a master model from which they take a plaster-faced plastic (PFP) splash, then lay up their tool. Once they create that surface, typically a carbon fiber epoxy tool, they produce a supporting structure beneath that composite tool on which they lay up their parts.”

Roppo cites two primary processes when laying up parts: The first, vacuum bag oven curing produces a maximum of 14.7 psi if it is a perfect vacuum. The second is a high-temperature, high-pressure autoclave cure. “Being able to generate 90 psi produces much greater compaction on the fibers you’re laying up.”

When it comes to this application, our LAST-A-FOAM® polyurethane foams can hold a vacuum better than other materials due to its closed-cell characteristic.

Layup tool masters

In the case of room temperature curing, soft tooling is a more cost-effective and efficient alternative to hard tools. The FR-4500 can be used as the actual layup tool to make the part. Bypassing the PFP and composite and going straight to a foam tool saves time and money. “If customers are doing low volumes or prototyping, that’s a much quicker way to do it,” Roppo adds.

Substituting FR-4500 foams for low-density applications such as master layup tools and vacuum forming highlights another advantage compared to metallic tooling. For example, even in high densities, LAST-A-FOAM® FR-4500 foam is 75 percent lighter than aluminum. From a safety and ergonomic standpoint, it’s easier to move and less dangerous to maneuver around in the shop, as well as cheaper to ship.

Doing double duty – vacuum holding fixtures and shop aids

Many of our aerospace customers get even more value from their investment in our foam. In the previous example where FR-4500 products serve as the master model used with the PFP and composite tool, they often convert the master model to a vacuum holding fixture (VHF).

“Once the part is layed up on the composite tool, vacuum ports or paths are added to the master model. Then, the part is removed from the composite tool and placed over the master model, and vacuumed down onto the foam tool,” Roppo explains. “Next, it is machined and interior features, such as pockets, are added. So, now it’s holding that part in place for all the post-machining operations – locking it down so the part can’t move around.”

Oftentimes, the FR-4500 high density foam boards are also used as shop aids. The foam can be used to create a holding cradle, essentially functioning as a tool inside the CNC machine when performing complex machining.

Part modeling and prototyping

Our FR-4500 high-density foams are also valuable for modeling and prototyping parts prior to producing the final product – particularly in expensive or exotic metals, such as titanium. For part verification, it’s faster and more affordable to machine the part out of our foam, and use that tangible, three-dimensional object to proof the prototype as well as for tool path verification.

Before cutting into expensive materials, this process ensures customers that the programming of their tool path is correct for machining the material. It makes it easier to confirm that they have a good model to produce a part that’s appropriate, and to validate the accuracy of their program without the extra costs.

One-stop tooling convenience: machining

Some customers purchase our foams to machine and produce their tooling in-house. Others take advantage of our production services to machine their foam tooling for them. As part of this service, General Plastics also performs an inspection utilizing our state-of-the-art CMM to ensure that what they receive conforms to their engineering and exacting standards. Other companies without in-house machining who order foam boards from us and send them to another shop for machining don’t realize that the added operations, activities and shipping add cost and time to their workflows.

“It’s more efficient and cost-effective to have us produce the tool they need,” Roppo says.

Producing finished tools for customers also includes supplying large, monolithic tools that require no bonding. For even larger tools that exceed our biggest block sizes, customers may also take advantage of our expert bonding capability to obtain the size and shape they require. We can bond together our foam material to produce a larger block or produce more material before machining to satisfy job requirements.

LAST-A-FOAM® FR-4500 high-density tooling boards are available in densities ranging from 12-50 pcf, although composite tooling applications require densities of 30 pounds and up. In addition to stock boards, customers can request custom sizes. For more information, contact our technical sales representatives at sales@generalplastics.com  .