Page 28 - MetalForming August 2014

Digital Manufacturing Impacts Sheet Hydroforming
Sheet hydroforming often allows for the formation of multiple parts in a single press cycle. Shown are sheet-
hydroformed parts and their related 3D-printed tools, manufactured from Ultem 9085—a high-perform- ance fused-deposition-modeling thermoplastic from
Stratasys. The material can withstand hydroform- ing pressure to 20,000 PSI.
the need for third-party
suppliers. Second- ary tooling, such as drill and trim tools, as well as check fixtures also can
be eliminated.
Step 3–Sheet Hydroforming
The last leg of our journey involves sheet hydroforming—forming sheet- metal using a flexible rubber diaphragm or bladder against a single tool or form block. Hydraulic fluid pumped into the bladder pressurizes it to supply a sig- nificant and evenly applied force on the entire part surface. Because the bladder acts as a universal die half that conforms to any shape within the form-
ing chamber, only a single tool half is required—traditional matched die sets are eliminated.
Sheet-hydroforming tooling can be produced quickly and inexpensively from a variety of materials, including steel, aluminum, poured epoxies, wood and, of course 3D-printed mate- rials. This dramatically improves new- part development time and lowers overall process costs, making sheet hydroforming ideal for rapid proto- typing and short- to medium-volume production.
Summarizing his thoughts on the combination of simulation software, 3D-printed tooling and sheet hydro-
forming, Pryer adds:
“If you need to run production, you
might still consider a traditionally machined steel or aluminum form block. But for proving out new designs or for low-volume part production, 3D- printed tooling is an extremely attrac- tive compliment to the sheet-hydro- forming process.” MF
Case Study: Steelville Manufacturing, Steelville, MO
In March 2014, Steelville Manufacturing Co., a contract machine shop specializing in milling, turning, waterjet cut- ting and metalforming, took delivery of a new sheet hydro- forming press (a Triform 24-5BD from Beckwood Press Co.) The bladder forming press features a 24-in.-dia. forming area with a maximum forming pressure of 5000 PSI.
“Before the Triform, we often would form flanges and other part features in a press brake,” says Steelville engi- neer Joseph Dust. “We would also preform certain parts by forming them into stacked rubber against a male or female die, before finishing them in a secondary operation in a traditional stamping press with male/female tooling. With the sheet hydroforming press, we can bypass those processes and form our parts more quickly and efficiently.”
This multistep forming process proved time consuming and expensive. In addition to increased engineering requirements, Steelville’s traditional methods also required considerable CNC labor and machine time. Its manufac- turing team would have to design and manufacture mat- ing dies for those parts which could not be press-brake
formed, and those parts which were eligible for press- brake forming often would require multiple hits in order to fold multiple flanges on a single part.
“Now, we can use the Triform to form a seven-bend part in less than one-fourth the time it would have taken in our press brake,” says Dust.
While Steelville can create a single tool using poured epoxies and traditional machined materials, it has been an early adopter of 3D-printed tools. By using 3D printing to produce form blocks, Steelville bypasses its machining centers all-together.
This collaboration between 3D printing and sheet hydroforming has dramatically shortened turnaround time for new-part production, while driving down overall cost per part.
“We had been forming parts for years that we now know were tailor-made for the Triform,” concludes Dust. “Within the first week of having the press on our floor, we’d already moved more than 10 parts that now are being formed using the Triform process.”
26 MetalForming/August 2014
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